APS of a XAS beam line at SOLEIL

Transcription

APS of a XAS beam line at SOLEIL
in the 4-40 keV range
Valérie Briois, Stéphanie Belin, Agnès Traverse
LURE
with the participation
for optical calculations and technical advices of
Gilles Cauchon, Mourad Idir, François Polack,
Jean Michel Dubuisson, Marc Ribbens
for contacts with the scientific communities
A. Traverse (Physics)
H. Magnan (Surface Science)
V. Briois (Chemistry)
D. Bazin (Catalysis)
I. Ascone (Biology and Biomaterials)
G. Sarret and J. Rose (Earth and Environmental Sciences)
Special acknowledgements for helpful discussions to
Anne-Marie Flank and Françoise Villain
April 2002
1
CONTENTS
Table of the technical Description
3
1) Scientific Case
4
State of the art of the XAS technique
4
Overview of the LURE and ESRF possibilities
5
The XAS beam line at SOLEIL
5
Materials Science
7
Biology and Biomaterials
8
Earth and Environmental Sciences
8
2) Beam line Scheme
9
3) Sample Environment
15
a) Detection Modes
15
b) Acquisition Modes
15
c) Sample Environments
16
i) For static working mode
16
ii) For dynamic working mode
17
iii) Equipment already available
20
d) Combined Experiments
20
e) Support Laboratory and Storage Room
23
4) Estimated Costs
24
5) Scientific Contributions of the users community
25
2
Technical Description
Photon Energy
Source
X Angular acceptance in the front end
Emittance of the BM
E=4-40 keV
Bending Magnet at 4°
1 mrad vertical by 6 mrad horizontal
Collimating mirror M1
at 16 m
Double Crystal Monochromator with horizontal
focusing
at 22.5 m
Collimating mirror M2
at 36 m
Sample environment
at 45 m
Double crystals with fixed exit equipped with
Si(111) and Si(311) crystals working in the 5 to
30° reflection range
5x1012 photons/s/0.5 Amp
106
80x30 µm
0.6 eV
0.50°
Optics Location in Geometry 1:1
Monochromator
At 5 keV with Si(111) Flux
Harmonic rejection
Spot size at 45m
Energy Resolution
Incident angle for
Mirrors
Harmonic rejection
Spot size at 45m
Energy Resolution
Incident angle for
Mirrors
Harmonic rejection
Spot size at 45m
Energy Resolution
Incident angle for
Mirrors
Acquisition Mode
Sample Environment
5x106
80x30 µm
0.4 eV
0.23°
NA
80x30 µm
1.3 eV
0.10°
Step by Step or Quick-EXAFS modes
Liquid Cells, Ovens, Cryostats, High Pressure
Cells, UHV chamber, controlled atmosphere
chambers, goniometers
Combined Experiments : DSC, XRD, UV-Vis
Transmission, Total Electron Yield, Fluorescence
For sample preparation and storage
Detection Mode
Support Laboratory and Annex
3
1) Scientific case
State of the art of the XAS technique
The physical process underlying the X-ray absorption spectroscopy (XAS) is the
ejection of an electron when X-rays are absorbed by the matter. The interferences between the
outgoing wave associated to the photoelectron and the waves originating from the
backscattering of this photoelectron by the neighbouring atoms give rise to oscillatory
structures on the X-ray absorption spectrum, arbitrarily divided into Extended X-ray
Absorption Fine Structures (EXAFS) and X-ray Absorption Near Edge Structures (XANES). In
contrast to X-ray diffraction (XRD), XAS is an element-specific probe which can be applied to
materials without long-range crystalline order. It allows the experimentalist to characterise
the structural and electronic properties of a system, whatever the state of the target, solid,
liquid or gas and for atomic concentrations ranging from a few ppm to the pure element. This
technique is thus widely carried out in a large community of users in the fundamental and
applied research fields, including Physics, Chemistry, Environmental Sciences, Biology and
Surface Sciences.
In the past two decades, the users’ community has benefited from real advances in
theory first with the improved treatments of scattering potentials used to calculate phase
shifts (Teo and Lee 1978, McKale et al 1981 and Rehr et al. 1992), second with the
implementation in various codes of multiple scattering processes. Let us mention the
pioneering works of Natoli and coworkers (1980) and Durham and coworkers (1981), then the
development of the different versions of the FEFF code (1992) by Rehr and coworkers. Today
the curved wave multiple scattering formalism available in the FEFF8 code provides a unified
treatment of the structures in both EXAFS and XANES. Such formalism which works in real
space is well adapted to the local range order XAS technique. It allows accurate determination
of geometrical arrangements of atoms from the analysis of the EXAFS part of the XAS
spectrum (coordination number, interatomic distances, disorder and angles) and provides
quantitative information about the electronic structure of the absorbing atom from the
analysis of the XANES part (local projected density of states (LDOS), spin and orbital
moments). Nevertheless, we are far from a reliable inverse-method of extracting structural
and electronic parameters from XANES simulations as the one available for EXAFS
simulations. The treatment of thermal and configurational disorder with the cumulant
expansion, nowadays implemented in most of the codes, has been also of crucial importance
for the accurate determination of structural parameters and vibrational properties. The
combination of EXAFS and molecular-dynamics simulations seems to be also a promising
approach for studying very disordered systems but remains nowadays a challenge for the
future. Referring to the last International Conference on XAFS held in Ako (Japan) in July
2000, what we can hope as improvements of theoretical tools are better calculations of
scattering potentials, in particular to go beyond the muffin-tin approximation, better
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treatments of core hole, multielectronic (multi-excitation and multiplet interaction) and manybody effects. Furthermore the implementation of automated error analysis method into robust
fitting codes should be also a priority.
Besides the theoretical developments which have largely benefited from interactions
between theoreticians and experimentalists, particularly favoured in synchrotron radiation
facilities, the users’ community has also benefited in the past from permanent technical
developments. These developments were focused on the beam line optics to increase the
photon intensity on the sample, the spatial and energy resolution of experiments, on the
efficiency of detectors to shift the detection limits towards highly diluted systems, and, on the
sample environments. Combination of techniques for sample characterisation and
optimisation of surroundings in order to carry out dynamical studies of systems are new
developments proposed in this document.
Overview of the LURE and ESRF possibilities
At LURE, 4 beam lines are fully dedicated to classical XAS, in the range 0.8 to 30 keV
with about 550 users per year. On the average over the last four years, the ratio between the
number of asked runs over the actually distributed ones is about 2. On the beam lines
dedicated to XAS, BM29, BM32 and ID26 at ESRF, this ratio is even larger, about 4. The
activity around XAS is thus still high as demonstrated by these numbers and also by the
systematic existence of XAS lines on synchrotron facilities over the world.
An immediate conclusion is that the synchrotron of third generation, SOLEIL, must
have beam lines dedicated to XAS. Indeed XAS now belongs to the conventional tools of
structural and electronic characterisation of materials, including biological systems. Its use
allows the experimentalist to validate elaboration processes of samples or to connect the
measured structural or electronic characteristics to relevant physical, chemical or biological
properties. The measurement is made either i) on already prepared samples with a controlled
variation of the parameters of preparation or ii) on samples presenting an in situ controlled
evolution of their physical and chemical properties. In this case, one can speak of a static or
quasi-static working mode. XAS can also be carried out to follow sample evolution during
structural or electronic transitions, induced by temperature, pressure, applied stress… Here,
one can speak of a dynamic working mode. In this dynamic working mode, the
experimentalist wants to follow a reaction in real time. Hence quick EXAFS must be available
on a SOLEIL beam line.
The XAS beam line at SOLEIL
Two meetings organized in Nov 97 and recently in June 01 with about 80 participants
from the Materials Science, Biology and Environmental Science communities, have led to the
definition of the main characteristics of an X-ray beam line dedicated to Absorption
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Spectroscopy. This beam line with high spatial and energetic resolutions must cover a large
energy range.
This proposal concerns a beam line for XAS in the 4-40 keV range.
The 4-40 keV energy range covers the K edges of elements with 20 ≤ Z ≤ 58 - i.e. from
Ca to Ce - and L edges of elements with 50 ≤ Z ≤ 98 - i.e. from Sn to Cf. This concerns the most
studied elements in catalysis (Re, Pt, Zr, Mo, Ru, Rh, Pd, Sn and Sb), in environmental science
(3d-elements, As, Cd, Hg…), in coordination chemistry (3d and 4d-elements), in biology (Ca,
3d, Pt …), and in physics (e.g. 3d and 4f elements for magnetic materials...). The energy range
above 25 keV is justifed by the strong emergence of scientific cases based on systems prepared
from heavy elements in different fields of Materials Science. In this case it is important not
only to access to the L edges of heavy elements which offer a reduced energy domain for
EXAFS measurements (typically from 150 to 450 eV) but also to the K edges. EXAFS
spectroscopy at these K edges allows an accurate determination of structural parameters and
their exploitation is very complementary to the one of L edges. Moreover the study of K edges
instead of the L edges of the same element is also useful in order to avoid the multielectonic
transitions pitfall, often difficult to handle in the EXAFS treatment. In fact frequently, in the
same proposal, users ask for the characterisation of the same material at both edges of a given
element or at edges of various chemical elements (e.g. the metal and the ligand in chemistry
or biology). Note that EXAFS measurements at edges located at lower energies (between 1
and 4 keV) will be available on the MICROXAS beam line, already validated by the Scientific
Council of SOLEIL. The general characteristics of the 4-40 keV beam line are presented in Part
2 of this document.
As already mentioned Materials Science, Biology and Environmental Science include
potential users belonging to many disciplines. Thus the beam line must be characterised by a
variety of Detection and Acquisition Modes, Sample Environments. A new and interesting
development on a SOLEIL beam line could be to combine structural techniques such as XAS
and XRD, XAS and X-ray scattering, provided that requirements for one technique does not
hamper the other one. A specificity of a beam line on SOLEIL could be also the combination of
XAS with techniques where a specific property is measured. Let us suggest, for instance, UVVisible absorption or visible scattering (turbidity) measurements, conductivity versus
temperature, or calorimetric measurements that can be achieved rather easily. These topics of
the beam line will be presented in Part 3.
An estimated cost of the beam line established from the known costs of two recent
beam lines working now or commissioning soon in the same energy range : H10 at LURE and
FAME at the ESRF are given in Part 4.
In Part 5 of the document have been compiled in a non exhautive way the scientific
cases of the different communities of users. This large part presents recent research topics for
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which XAS is still extremely useful. The proposed experiments are in connection with recent
results and thus made in the context of a tomorrow operation of the beam line. We summarise
herein the main directions of these scientific cases.
Materials Science
From the fundamental and technological point of view, nanosystems are nowadays of
great importance. These systems display only short-range order because of their small size,
hence, XAS is the required technique to describe their structural and electronic properties but
also to determine their average size. The motivation of XAS investigations performed on
nanomaterials is the understanding and optimisation of their new magnetic, electrical, optical
observed behaviours or of their enhanced chemical reactivity.
For example it has been shown that the optical absorption spectrum of metallic
aggregates embedded in dielectric matrices, called nanocermets, is strongly related to the
intrinsic electronic properties of the aggregates and to their local surroundings. The
development of magneto-optical devices has benefited from relationships between structural
and electronic characteristics and physical properties established by XAS on metallic clusters
in matrices, metallic thin films and epitaxial multilayers.
Besides the physical techniques (ion implantation, low energy clusters beam
deposition, …) used to prepare the above materials, a lot of chemical techniques allow the
researcher to be provided with materials with tailored properties. Among them, Soft
Chemistry has largely benefited from XAS to design new molecular precursors used in the
elaboration of nanomaterials for catalysis, optical and electrical devices, energy storage, high
performance ceramics and so on… and to understand the mechanisms of formation or
transformation of such materials. To illustrate this field we can just mention the strong
emergence of new anodic and cathodic materials for rechargeable solid state batteries. These
materials are based on the chemistry of intercalation and de-intercalation of lithium into host
matrices (NixSn, LiNiVO4, …). The knowledge of oxidation state of the elements of the matrix
and of the atomic arrangements of the solid network, generally disordered upon intercalation
and de-intercalation processes, provided by XAS is of prime importance for this research field.
The community expects from the high photon flux of SOLEIL to be able of studying such
batteries in situ during their functioning.
One of the well known applications of nanomaterials, in particular nanoparticles lies in
the heterogeneous catalysis field. Supported noble metal catalysts are used in a number of
important industrial processes (e.g. Fisher Tropsch reaction (production of long chain
paraffins from syngas CO + H2) uses for the most part cobalt catalysts supported on different
oxides) but also to solve environmental challenges like the emission control of toxic gases (e.
g. use of Pt-based catalysts supported on oxides or zeolithes for the reduction of NOx
emissions from Diesel car exhaust gases). Research at the cutting-edges requires the capability
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to perform in situ characterisation of the reactivity of these catalysts under experimental
conditions.
In coordination chemistry, prussian blue analogues have recently attracted great
interest because their use as molecular magnets. In particular the understanding of magnetic
phase transitions of these molecular systems upon light irradiation is nowadays the subject of
intense XAS and XMCD investigations.
The understanding of the mechanism of hydrogen adsorption in metals and
intermetallics motivates a lot of XAS studies. Metal-hydrogen systems are used in a variety of
technological applications including hydrogen storage materials and metal hydride batteries.
The synthesis of glasses with optimized optical characteristics (eg high non linear
refractive index in tellurite glasses) or ion conduction properties suitable for applications in
semiconductors devices, optical fibers, wave guides ... motivates also XAS studies. Besides
these technological motivations, a lot of structural XAS studies are connected to Earth Science
since the structure of glasses is considered to be analogous to that of magmatic liquids.
Finally the access to compressibility factors around minor elements in various
compounds (impurity in oxides, magnetic dopants in semi-conductors, minor elements in
metallic alloys…) by performing XAS experiments under high pressure and high temperature
is nowadays a challenge in Materials Science which could be taken up on a classical XAS
beam line at SOLEIL.
Biology and Biomaterials
Metal ions are present in the form of metallo-proteins (25-30% of all proteins) and of
various bio-inorganic complexes as active components of drugs involved in pharmaceutical
applications. The advantages of XAS for metallo-proteins over crystallography are that it does
not require extreme protein purity ; it avoids the requirement to grow crystals as proteins
could be in solution ; it is not limited by protein size; and metal sites are described at atomic
resolution. The technique is also interesting for the study of reactivity of biomimetic
compounds. These systems that are simple model compounds are used to understand the
mechanism of catalysis of large and sophisticated systems like metallo-enzymes.
Researchs in Environmental Sciences at the molecular level concern research groups
from various disciplines such as earth sciences, chemistry, biology, catalysis, and material
sciences. They provide some bases for the understanding of polluted site reclamation,
improvement of water quality, waste management … which are crucial for the preservation of
the environment. In the frame of the formations of rocks and magmas, the sensitivity of XAS
to the presence of redox states is fruitful to estimate the oxidizing conditions prevailing at the
Earth surface during magmatic eruptions.
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2) Beam line Scheme
The proposed beam line scheme is very close to that of the H10 beam line (LURE/Orsay) or
FAME (ESRF/Grenoble).
On SOLEIL, a bending magnet source will deliver a continuous spectrum of photons with a
critical energy Ec = 6.5 keV. The main characteristics of the SOLEIL source working at 2.75
GeV are summarized in Table 1.
1°
4°
σx (µm)
60.1
42.1
short
Medium
388
182
Bending magnet
σz (µm)
24.9
24.5
Straight section
8.08
8.11
Emittance
εx=3.74 nm rad
εz=0.0374 nm rad
σ’x (µrad)
134.8
107
σ’z (µrad)
2.1
2.1
14.5
30.5
4.6
4.6
Table 1 : Characteristics of SOLEIL
The beam line is designed to be used from 4 to 40 keV. Then the beam line should be installed
on a bending magnet. The angular acceptance delimited by a collimator in the front end is 1
mrad vertical by 6 mrad horizontal. A typical layout of the beam line is shown in Figure 1.
Figure 1 : Schematic drawing of the Beamline
Vertical collimation and focusing will be provided by two bendable mirrors M1 and M2
(parabolic shape) with lengths close to 1m located at 16 and 36 m from the point source,
respectively. These mirrors are made of silicon with a coated layer of about 100 nm of an
heavy element (e. g. Ni, Pt, Rh, Pd). Figure 2 presents the Reflectivity versus Energy for
different coatings of the mirrors at 0.15° (2.6 mrad) incident angle. To cover the largest energy
range, good candidates as element used as coating are Rh or Pd. In the 4-40 keV range, these
coatings present a discontinuity at the K edges (24350 eV for Pd and 23220 eV for Rh).
9
M ir ro rs 0 .1 5 ° (2 .6 m ra d )
23 keV
1 .0
Reflectivity
0 .8
Si
Rh
Pt
Pd
Ni
0 .6
0 .4
0 .2
0
5000
10000
15000
20000
25000
E n e rg y (e V )
Figure 2 : Reflectivity versus Energy for different mirrors at 2.6 mrad
Figure 3 presents the Reflectivity versus Energy for different Pd mirror incident angles. The
incidence angle on the mirrors will be optimized depending on the required energy for the
experiments. These mirrors will also be used to eliminate higher order harmonics reflected by
the monochromator. For instance for harmonic rejection above 10 keV, the Pd mirror will
work at 0.5° (8.7 mrad) whereas for harmonic rejection above 25 keV the incidence angle will
be 0.15° (2.6 mrad). The angular value of 0.08° (1.75 mrad) will be the condition to work in the
26-40 keV range. A fixed entry of the focussed beam on the monochromator and on the
sample will be ensured by a vertical translation of optics when the incident angle on the
mirrors will be changed.
1
0.08°
0,8
0.15°
Reflectivity
0.2°
0,6
0.3°
0.5°
0,4
0,2
0.8°
0
5000
10000
15000
20000
25000
30000
35000
40000
E (eV)
Figure 3 : Reflectivity versus Energy for a Pd mirror at different incident angles
10
Monochromatization will be performed by a fixed-exit, double-crystal monochromator. The
second crystal can be bent dynamically to provide horizontal focusing. The technical choice to
realise the fixed-exit option is not already defined and the possibility to work in the channelcut mode should be opened. The monochromator will be located at 22.5 m from the point
source.
The optical system is designed to be tunable between 4 to 40 keV with two sets of Si(111) and
Si(311) crystals in the monochromator. The angular range of the double crystal
monochromator is from 5 to 30°. The change of crystals, necessary to cover the entire energy
range with the best flux and resolution, should be easy and optimized in order to allow a
rapid change of experimental configurations. From the experience of colleagues in this
domain (e.g FAME beam line), we propose to use two interchangeable crystal-holders with
pre-tuned positions for horizontal focusing or the use of translating crystals as offered in the
KOHZU technology. This explains the high evaluated cost of the monochromator (see Part 4).
Beryllium windows will be installed near the front end of the beam line. The thickness of the
windows will be optimised to take into account the minimum thickness for the vacuum safety
and the maximum transmission for the lower energy part of the spectrum. For example, in
Figure 4 we have calculated the transmission of different Be filters versus Energy. From these
calculations, we can see that at 4 keV, a 100 µm Be filter gives 85 % transmission.
1.0
Transmission
0.9
0.8
500 µm
200 µm
100 µm
50 µm
10 µm
0.7
0.6
0.5
0.4
4000
4500
5000
5500
6000
6500
7000
7500
8000
Energy (eV)
Figure 4 : Transmission of Be filters versus Energy
Additional slits will be included in the beam line design in order to collimate the beam (at the
exit of the front end), to remove scattering on the sample and/or to fix the beam size on the
sample when the horizontal focusing of the monochromator is not used.
11
We have done raytracing1 calculations to characterize the flux and the shape of the beam at
the sample location. According to these calculations, a monochromatic spectral flux at 5 keV
delivered by a Si(111) double-crystal monochromator (sagittal focusing) of approximately
5x1012 photons/s/0.5 Amp will be focused on the sample (located at 45 m from the point
source) in a spot size of 80(horizontal)x30(vertical) µm. Figure 5 presents the result of the
raytracing calculation. This image calculated for ideal optics is a cross section of the beam at
the sample location.
14
Flux photons/s/0.5 amp
2.0x10
14
1.5x10
14
1.0x10
14
0.5x10
0
-125
-100
-75
-50
-25
0
25
50
75
100
125
Distance (µm)
Figure 5 : Cross section (in red) and profil (in blue) of the beam at the sample location
Ray tracing calculation for E=5 keV
At 5 keV, the spectral resolution is 0.6 eV, i.e. close to the Darwin resolution. In this case, the
horizontal divergence accepted by the first mirror is close to 6 mrad. The radius of the sagittal
focusing crystal is 8.9 m and the beam footprint on the crystal is 120 mm. In this
1
The raytracing calculation are performed with a code developped by the Caminotec Cie
12
configuration, the incident angle of the beam on M1 and M2 mirrors is 0.5° (8.7 mrad), this
gives an harmonic rejection of 106.
At 15 keV, (incident angle on M1 and M2 = 0.23° (4 mrad)), with a Si(311) double-crystal
monochromator,
the
expected
monochromatic
spectral
flux
will
be
5x1011 photons/s/0.5 Amp. in a spot of 80 (hor.) x 30 (vert.) µm. The resolution will be close to
0.4 eV.
At 35 keV, using a Si(311) double-crystal monochromator, the expected monochromatic
spectral flux will approximately be 2x1010 photons/s/0.5 Amp. in a spot of 80 (hor.) x 30
(vert.) µm. The resolution will be close to 1.3 eV, which is better by a factor of 10 as compared
to the intrinsic spectral broadening of K absorption edges of heavy elements (e. g. 12.3 eV at
the Cs K edge 36 keV). In this configuration, the M1 and M2 mirrors are used at 0.1° (1.74
mrad).
All these calculations were performed with optics with no slope error and with 5 Å
roughness.
In the case of the vertical focusing optics (bendable mirror shaped as a parabola), the influence
of the slope error on the spot size is illustrated in Figure 6. The state of the art concerning X
ray mirrors indicates that a 2-5 µrad slope errors can be achieved on these kind of optics. In
the case of the horizontal focusing (bent crystal of the monochromator), the influence of the
mosaic shape of reflecting Bragg planes was not taken into account in the calculations. This
will induce an enlargement of spot size in the horizontal direction by a factor 2 or 3. Then, the
expected spot size will be 120 –200 µm in the vertical direction and 200-250 µm in the
horizontal one. Note that the scope of the beam line is not to achieve microfocalization
experiments, such focus spot size is totally convenient for classical XAS.
450
400
Spot size (µm)
350
300
250
200
150
100
50
0
0
1
2
3
4
5
6
7
8
9
10
slope errors (µrad)
Figure 6 : Influence of the slope errors on the spot size
13
The location of all the optical components of the beam line is listed in Table 2. This design
corresponds to a 1:1 geometry which is known to minimise the aberrations on the optics. The
location is schematised on the ring in Figure 7 on a bending magnet (D06-2) with an exit at 4°
(near a beam line on a bending magnet with an exit at 1°).
Optical component
Distance from the source (m)
Mirror 1 (bendable) M1
16
Monochromator (horizontal focusing)
22.5
Mirror 2 (bendable) M2
36
Sample
45
Table 2 : Position of the optical components in the geometry 1:1.
M2
9m
36 m
Mono
16,5 m
45 m
da
i i
22,5 m
M1
d d alim
v p i i i
13,8 m
5m
5m
Figure 7 : Possible location of the beam line on the ring
Due to the different sample environments which are planned to be installed at the focus point
located at 45 m (see Part 3), the space available around the sample must be as large as
possible. For instance the installation of an ultra-high vacuum chamber for surface science
requires a free space at the focus point of about 5m transverse. The beam line should be
installed
- either on a bending magnet exit with a “short” neighbouring beam line (i.e.
the end of this beam line is located at 40 m maximum) ,
- or on a bending magnet with an exit at 4° (total length 50 m) without
implantation of a neighbouring beam line on the 1° exit.
14
3) Sample Environment : from the detection to the samples
a) Detection Modes
Three detection modes must be available on the beam line :
1) The use of ion chambers filled with different gases depending on the required energy is the
most versatile system available for the transmission mode. Three ion chambers (I0, I1 and
Reference ion Chamber I2) associated to full electronics including three Keithley current
amplifiers (working from the pA to nA range) are necessary.
2) The station must be equipped with a multielement solid state detector for fluorescence
experiments. Such a detector with energy discrimination is necessary for dilute systems or
thin layer characterisations. The electronics must include semi-automatic gating of the energy
range to be selected, high Input Count Rate capability (typically 100 000 cts/s) and dead time
correction.
3) Measurements carried out on supported films, bulk materials etc … need to be recorded in
total electron yield detection mode. This includes the development of special detectors. The
electronics is the same as for transmission detection (in particular sensitive current amplifiers
in the pA range)
b) Acquisition Modes
An acquisition timescale varying from a few seconds (Quick-EXAFS mode) to a few minutes
(step by step EXAFS) must be available on the beam line.
The use of quick scanning EXAFS is a prerequisite to follow dynamical processes (phase
transition under temperature, hydrolysis-condensation processes in sol-gel chemistry …).
Some of the ancillary equipment (e. g. see below differential scanning calorimetry (DSC)) will
be fully exploited only if they are coupled with Quick-EXAFS. This option must be planned
from the conception of the monochromator system, data acquisition and storage system.
Among the 2 possibilities to carry out Quick-scanning of energy, we favourably consider the
use of a DC motor feedback servo system to scan the energy range at constant angular speed.
15
c) Sample Environments
i) For static working mode
Four kinds of sample environment should be made available for characterisation in the socalled static working mode :
A. Cryostats allowing the reduction of the damping effect due to thermal motions, the
damage protection of the samples against photon irradiation (e.g. biological samples) and
the study of temperature dependent behaviours.
B. Controlled atmosphere chamber allowing the damage protection against moisture,
oxygen …
C. Ovens with controlled atmosphere, thermostated liquid cells, stopped-flow system, highpressure cells and preparation chambers for surface characterisation… to perform
experiments under reaction conditions and/or to perform in-situ preparation of
materials.
D. A goniometer allowing versatile orientation of the sample surface for the study of
anisotropic behaviours (within 0,1 deg). Such measurements should be possible in the
three detection modes available on the beam line.
The biology community must use its own cells which will be adapted to common
equipments (cryostats, thermostated devices and pressure device to modulate the pressure
between 0 and 2 kbar). Specificities would be cells with a transparent aperture to enable a
laser irradiation, that means a tunable laser available on the line and cells equipped with
electrodes, for coupled electrochemistry experiments (that means an micro electrochemical
system) used to stabilize peculiar states of catalytic cycle of biomimetic compounds (cyclic
voltammetry experiments). Note that a special attention should be paid to the development of
cells having safety standards (P2 or P3 standards) for the study of pathogenic proteins (like
prion).
In the field of surface science, the community needs :
-an UHV analysis chamber with different detectors (total yield, multielements fluorescence
detector and an high luminosity electron spectrometer (Scienta type) for partial yield
detection); this last spectrometer will be also used for the resonant electronic spectroscopies
measurements in the X-ray range, since the same chamber can be used for the two
measurements (possibly on different beamlines). In this chamber, the sample must be heated
16
and cooled down to ≈ 20K and rotated with respect to the polarisation direction (polar and
azimutal angles). The rotation in polar angle should be precise to allow reflEXAFS
measurements.
-a standard preparation chamber for the studies of metallic thin films with a complete
equipment for surfaces and thin films preparation.
-a STM chamber. This chamber could be installed on the beam line in order to perform
combined STM and X ray absorption experiments, either to measure EXAFS spectra of a
particular dot or to use X-ray for STM elemental analysis. Tests of this method are still
necessary.
-different specific preparation chambers which can be shared with other SOLEIL experiments,
to prepare thin oxides layer with a oxygen plasma source and to prepare semiconductor
model devices. The existence of these specific preparation chambers will offer to the surface
community the possibility to study these new materials with several techniques using
synchrotron radiation.
Estimated costs: 2 MF for new equipements (Scienta+ STM). These costs are not yet included
in the estimated costs of sample environments presented in Part 4.
Note that the installation of the ultra-high vacuum chamber (2 m x 2 m x 3 m) to prepare and
characterise clean samples requires a sufficient free space at the focus point. This equipment
should be installed at the end of the beam line in a large enough area. In addition, a support
laboratory and a storage area (see above) have to be installed in the so-called “oreille” room.
ii) For dynamic working mode
Several communities of users have clearly shown an interest to develop equipment
suitable for dynamic measurements.
In the field of heterogeneous catalysis, the most valuable information is obtained for
samples during the catalytic activity. A consortium of several laboratories in France is
interested in developing equipment in order to reproduce, at the beam line, reaction
conditions which are as close as possible to those existing in the home laboratory (high
temperature 300-500°C, different reaction atmosphere: hydrocarbons, H2, H2S, NOx, CO …
and different pressures:1-40 bars). Basic developments which should be the responsibility of
the beam line scientists under the advice of the consortium of users include :
i) The reaction cell (1bar, 800°C) : 150kF
17
The powder is positioned in a boron nitride sample holder and cover plate. Boron
nitride is chemically inert and not harmful for human beings. The furnace is equipped with
two K type thermocouples : one inserted into the top of the sample mounting block and the
second at the bottom to monitor the temperature in the body of the reactor cell. With such an
experimental device, the maximum temperature is 700°C. Note that this information should
be recorded by the computer which collects the EXAFS data.
In addition, it is usually very difficult to perform structural investigations in systems
with concentrations of active components below 1%. Thus, a fluorescence reactive cell method
has to be build in order to study very diluted systems.
ii) A special regulation device : 150kF
A device with various gas cylinders (such for example H2, N2+O2, CO, NO, H2S, Ar
and other gases) and flow controllers with large flow rate ranges must be developed to
reproduce the catalytic conditions as closely as possible. It would be of great interest to have
the possibility to modify the nature as well as the rate of gas flow via the computer which
controls the experiment. This configuration allows perfect timing between the beginning of
the chemical reaction and the data acquisition procedure.
Note that the activity and selectivity of the catalytic reaction could be determined by
analysing the exhaust gases through gas chromatograph/mass spectrometer/catharometer.
This further development should be the responsibility of the concerned community.
iii) Security of the experimental set-up : 150kF
Due to the possible use of toxic gases, special attention has to be paid to the safety of
the experiment. Several specific gas detectors must be located close to the experiments and
must be linked to the regulation device in order to evacuate automatically the reactive gas in
case of a gas leak. Also, the output gas has to be removed from the experiment. Thus, a system
devoted to this operation has to be present on the beam line.
These basic equipment for heterogeneous catalysis can be also installed on the transferred
H10 and dispersive beam lines. Compared to the experiments available on these beam lines,
those carried out on the XAS 4-40 keV beam line will take benefit from the access to a large
energy range with a flexibility of detection modes (transmission, fluorescence…), from the
ability to study time scale reaction of a few seconds with QuickEXAFS scanning mode, and
from the ability to perform combined experiments, in particular XAS and Raman spectroscopy
(see the part devoted to combined experiments) in order to correlate the structural/electronic
description
of
catalyst
with
information
18
coming
from
the
measurement
of
its
activity/selectivity. The complementary between the different beam line projects in the field
of heterogeneous catalysis is addressed in a more extensive way in Part 5 of this document.
In the field of high pressure and high temperature, the community, who has already at
LURE an access to the EXAFS dispersive station, will develop experiments using the
voluminous Paris-Edimburgh (PE) cells (see the description in the x-ray diffraction under
extreme conditions APS) on the beam line proposed here. The PE cells allow the access to
higher temperatures (about 2000°C) than the diamond anvil cells used on the dispersive
station (limited typically at 700°C). The usual pressure for the PE cells used in the conditions
of an X-ray absorption experiment is about 6 Gpa. The use of such PE cells is compatible with
fluorescence experiments that offers the characterisation of minor elements in compounds
(impurity in oxides, magnetic dopants in semi-conductors, minor elements in metallic
alloys…). Note that such experiments are not possible at LURE on the dispersive set-up and
will be probably not straightforward on the dispersive set-up at SOLEIL. Furthermore, the PE
cells allow the study of materials with high atomic numbers which is not possible with the
diamond anvil cells (due to the presence of diamond Bragg reflections not easily removed by
rotation of the cell at high photon energy). Then, clearly new fields in the study of materials
under high pressure and high temperature should be available on the beam line with PE cells.
The experiments will take benefit from the possibility of recording both EXAFS and
diffraction on the same set-up. Therefore the pressure can be measured from the XRD patterns
of internal standard. This possibility is discussed on the part devoted to combined
experiments in this section.
For biological issues, dynamic measurements are required to study for example the
reactivity of pharmaceutical molecules. In this case a cell with a system ensuring the
circulation of the solution during kinetics experiments (like a stopped-flow system) or during
HPLC experiments should be available.
The different sample environments must be set on a motorised stage allowing easy
sample manipulation in x, y and z directions, and also tilt and rocking when required. This
table must be able to support large, heavy (until 100 kg) pieces of experimental equipment. It
must also be removable to give place to the preparation chamber for surface science.
19
iii) Equipment already available
A continuous He-flow cryostat with the sample being into the exchange gas has been
recently purchased in the framework of the “Option 1” program at LURE. With this cryostat,
measurements in the three detection modes can be performed at temperatures ranging from
4K to room temperature.
Other possible transferable equipment from LURE to SOLEIL:
- Thermostated liquid cells (-30°C<T<100°C) with adjustable optical path length for
transmission
- Liquid Nitrogen Cryostat for transmission and fluorescence experiments with
automation of the flow of Liquid N2 into the cryostat
For surface experiments, 1.5 MF of equipment including UHV elements, pumping, surface
preparation and characterization devices, electronics could be transferred from LURE.
d) Combined Experiments
The optics and detection of the beam line are optimised for absorption measurements.
Nevertheless, it is very convenient in Materials Science to have simultaneously an access to
different kinds of information for the same material. Indeed simultaneous experiments on a
sample offer great advantages with respect to separate experiments, not only to spare time but
also to rid oneself of errors due to differences in sample environment, thermal history, age,
temperature and sample preparation. Even more important is the possibility to resolve
ambiguities in the understanding of phase transitions mechanisms by allowing accurate
determination of the order of occurrence of the events by the different techniques. Note that
most of the combinations presented hereafter require Quick scanning EXAFS mode to
minimise the recording time and to access to time resolved studies like phase transition under
temperature variation (glass transition, gelification, crystallisation …).
Different combinations will be available at SOLEIL thanks to a transfer from LURE :
a) Combination of absorption spectroscopy with thermodynamic information
obtained from differential scanning calorimetry (DSC) experiments. We have
20
recently purchased a Setaram DSC111 instrument (Option 1) allowing accurate
determination of enthalpy of transition in the temperature range -196°C to 600°C.
b) Combination of absorption spectroscopy with electronic information obtained
from UV-Visible spectroscopic experiments. We have recently purchased a Cary 50
UV-Visible Spectrometer (Varian) combined with optical fibers and allowing
simultaneous recordings of UV spectra and EXAFS spectra.
New combinations will be proposed such as absorption and vibrational spectroscopies and
absorption and diffraction.
Recent technological developments in Raman spectrometry (increase of detector
sensibility and new concept for the dispersive optics (holographic Notch filters) allow the use
of optical fibers, coupled in a unique probehead, for excitation and for collection of Raman
spectra. Since common windows (quartz) or sample preparation (pellets) are available for Xrays and Raman spectroscopies, the combination of both techniques would be
straightforward allowing the simultaneous access to local order information and vibrational
data in the Mid-IR region for the same material, eventually under reactional atmosphere.
Raman and XAS spectroscopies are both local order techniques sensitive to the symmetry of
molecular species. But the high sensitivity of Raman to describe atomic arrangements
involving light elements like hydrogen atoms (e.g. hydroxyl groups and organic functions)
makes this technique complementary to XAS. Furthermore, a known advantage of Raman
spectroscopy over FT-IR spectrometry is its ability to be carried out in solution. All these
advantages make the combination of absorption and Raman spectroscopies valuable for the
study of liquid-solid interface (e.g. for water treatment or heavy elements speciation in soils in
environmental science) or for catalysis issues (understanding of active phase genesis, solid
reactivity under different atmosphere, study of adsorbed species …). A part of this
prospective development, in particular the design of reactor cell optimised for in situ
experiments in catalysis, should be the responsability of the user’s community but the
purchase of the Raman spectrometer could be included in the budget of the beam line
equipment.
Finally we would like to offer to the community the possibility of recording
(simultaneously or not with the X-ray absorption spectrum) an X-ray powder diffraction
pattern. This option is clearly a prerequisite of the high pressure and high temperature
community for the use of Paris-Edimburg cells. More generally, the combination of XAS and
21
XRD should be available during the dynamic characterisation of a reaction itself, that means
for a sample surrounded by special cell (oven, cryostat etc…). A flexible set-up should be
designed for such a combination. We can imagine to adapt a set of CdTe diodes like on the
BM29 beam line (ESRF) in order to record by energy scanning x-ray diffraction recording
(ESXRD) overlapped parts of XRD patterns. The principle of ESXRD is quite simple. The
diffraction pattern is obtained at fixed angles as a function of the energy of the incident
photons. This is quite similar to the energy dispersive set-up which is generally used with a
white beam. The main advantage of the energy scanning set-up is the resolution determined
by the angular acceptance of the slits system mounted in front of the detectors (10-3) and the
energy resolution of the monochromator which is smaller (10-4). In case of energy dispersive
set-up, the resolution is given by the energy resolution of the detector (10-2). With 6 detectors
at different angles, a large d spacing range can be covered with a limited energy scanning (<
10 keV). The sample is mounted in a quite complex assembly and the main problem for x-ray
diffraction experiments is to avoid the signal coming from the environment of the sample. The
energy dispersive set-up is well adapted to solve this problem because the slits system which
fixes the angle of diffraction acts also as a Soller slit (Figure 9).
Figure 9 : Principle of combination of XAS and ESXRD
For other purposes we can use an image plate or CCD device as position sensitive detectors.
Note that the possibility of probing both the short and long range ordered structures in a
given sample by use of the combination of XAS and XRD is clearly proposed in order to
optimize the XAS experiments. Structural studies which require high quality XRD data are not
the scope of the beam line presented in this document but rather of the transferred H10 beam
line.
Remarks about the manpower: The originality of the XAS beam line for SOLEIL is the variety
of scientific investigations that can be addressed, that implies an extreme versatility around
22
the sample as presented above. Such an originality must go with an adapted manpower. On
the one hand, the users coming with different scientific subjects must be well supported by
local contacts having complementary competences. On the other hand, the conception of the
different equipments together with the possibility of combinig several experiments requires
that ingeneers and technicians work with the beam line scientists. The installation of cryostats,
ovens, cells for liquids or gas on the station, and the maintenance of these equipments, also
require permanent technical support.
e) Support laboratory and storage room
It will be foreseen to have a support laboratory dedicated to the preparation of the samples
and their characterisation by standard materials science techniques (UV-Visible, IR, DSC…).
These characterisations could be made with the apparatus used for combined experiments
when they are not required on the beam line. The beam line is of about 50 m long and needs
an access at its end in order to remove voluminous chambers. Hence we would like to dispose
of a support laboratory at the external part of the building in which are the beam lines (i.e. at
the so-called “oreille” space). Necessary area : 20 to 25 m2
For the preparation of the samples, one should find :
A chemical hood for volatile substance manipulation
A dried box for the manipulation of sensitive samples
A system for powder deposition on membranes
A system to make pellets
A set (gloves, pipettes, syringes, needles) to manipulate liquid samples
Vacuum glass containers
A refrigerator
Several fluids should be available for general purposes:
Compressed air
Industrial water
Demineralized water
Nitrogen Gas
Gas evacuation line
A storage space must be free also for gas bottles and ancillary equipment storage when they
are not used on the beam line (particularly for voluminous chambers).
23
Scientific contributions of the users community
25
CONTENT
Materials Science
A. Nanostructured Materials and related applications
I - Ultrafine particles, Clusters embedded in a matrix
Nanocermets
32
32
32
32
T. Girardeau, S. Camelio, D. Babonneau, J. Mimault
LMP (Poitiers)
**********
Clusters embedded in matrices
A. Traverse
33
LURE (Orsay)
**********
Thin or thick films from clusters
34
L. Bardotti, V. Dupuis, A. Hoareau, B. Masenelli, P. Mélinon,
A. Perez, B. Prével, J. Tuaillon-Combes
DPM (Lyon)
II- Thin Films
35
Thin films from different techniques
35
I. Arcon
Nova Gorica Polytechnics (Slovenia)
**********
Surface EXAFS in the X-ray range
35
H. Magnan1, P. Le Fèvre2, D. Chandesris2
1CEA (Saclay), 2LURE, (Orsay)
III- Layered nanophase systems
Nickel Silicates
M. Richard-Plouet, M. Guillot, S. Vilminot.
IPCMS (Strasbourg)
26
37
37
**********
Layered Double Hydroxides and related materials
38
F. Leroux, J. P. Besse, A. De Roy
LMI(Clermont-Ferrand)
IV- Nanophase Materials prepared by “Soft Chemistry”
Lithium battery materials, Pigments-UV absorbersCatalysis and Doping oxides
39
40
G. Ouvrard
IMN (Nantes)
**********
Smart oxides layers
C. V.
Santilli1,
Pulcinelli1,
Dahmouche1,
41
Briois2
S. H.
K.
V.
1 IQ UNESP (Brésil), 2 LURE (Orsay)
and S.
Belin2
**********
Electrode materials, insertion compounds and nanostructured solids 43
J. C. Jumas, C. Belin, L. Monconduit, J. Rozière, D. J. Jones, F. Favier
LAMMI (Montpellier)
**********
Nanometric Ferrites
45
N. Guigue-Millot
LRRS (Dijon)
B. Catalysis
46
Characterisation of catalytic systems by EXAFS
48
E. Payen
Laboratoire de Catalyse (Lille)
**********
Metal-supported catalysts
P. Massiani
LRS (Paris 6)
**********
27
49
Synthesis of catalysts
C. Especel, L. Pirault-Roy, M. Guerin
LACCO (Poitiers)
50
C. Three-dimension systems
51
I - Molecular Materials
51
Photomagnetic Prussian blue analogues
51
A. Bleuzen, V. Escax, C. Cartier dit Moulin, F. Villain, M. Verdaguer
LCIMM (Paris 6)
II - Intermetallics and Alloys
52
Influence of H-absorption on the properties
of rare earth and transition metal alloys
52
V. Paul-Boncour, A. Percheron-Guégan, E. Alleno, C. Godart
LCMTR (Thiais)
**********
Evolution of the local structure with hydrogenation
in quasicrystals and approximants
53
A. Sadoc1, K. F. Kelton2
1LPMS (Cergy-Pontoise) et LURE (Orsay), 2Department of Physics, Washington
III - Glasses
54
Tellurite Glasses
54
P. Armand, P. Charton and E. Philippot
LPMC (Montpellier)
**********
Structure of glasses and liquids
L.
Cormier1,
D.
Neuville2,
1
Linard2,
Galoisy1,
Y.
L.
G.
LMCP (Paris 6 & 7), 2IPGP(Paris)
Calas1,
55
P.
Richet2
**********
BIMEVOX , Transition metal mixte oxides and associated glasses
S. Daviero Minaud, L. Montagne, O. Mentre, F. Abraham, G. Mairesse and G. Palavit
LCPS (Lille)
28
56
IV - Others
57
Combined x-ray absorption spectroscopy and x-ray diffraction under 57
extreme conditions of pressure and temperature in a large volume cell
J. P. Itié and A. Polian
Physique des Milieux Condensés (Paris 6)
29
Biomaterials
58
I. Ascone1, S. Benazeth2, J. Parello3
1 LURE, 2 LB (Paris V), 3 CBIB (Montpellier)
Biological XAS (BioXAS) experiments at SOLEIL
Background
58
Example of Bioxas experiments
58
Pharmaceutical studies
58
Metalloproteins in post-genomics
59
Reactivity of metalloproteins and biomimetic compounds
60
BioXAS strategies and perspectives
60
Laboratories support
62
X-ray absortpion and geo-risk assessment :
63
64
Contributions from a new-, hard x-ray beamline at SOLEIL
for the understanding of environmental issues.
F. Farges, S. Djanarthany, M. Harfouche, V. Malavergne, M. Munoz, S. Rossano
C. Lapeyre, J.-M. Le Cleac'h et M. Deveughèle
LG (Marne la Vallée)
**********
Molecular environment of As, Pb, U, Zn in soils and mine-tailing
64
G. Morin, F. Juillot, T. Allard, L. Galoisy
LMCP (Paris 6 & 7)
Synthetic glasses
65
L. Galoisy, L. Cormier, G. Calas
LMCP (Paris 6 & 7)
Nuclear waste glasses
L. Galoisy, L. Cormier, G. Calas, G. Morin, A. Ramos
LMCP (Paris 6 & 7)
30
66
Volcanic Glasses
67
L. Galoisy, M. A. Arrio, G. Calas
LMCP (Paris 6 & 7)
**********
Geosciences at the CEREGE
68
J. Rose, A. Masion, J. Y . Bottero, J-M Garnier
CEREGE (Aix en Provence)
**********
Study of actinides and lanthanides
69
C. Den. Auwer
CEA (Cadaache)
**********
Authors’ adresses
70
31
Materials Science
A. Nanostructured Materials and related applications
Nanostructured materials have been classified by Siegel [1] according to their integral
modulation dimensionality: zero for ultrafine nanoparticles and clusters, one for multilayers,
two for films and three for nanophase materials. These materials present exciting properties,
e.g. mechanical properties such as superplasticity and high hardness, magnetic properties
such as giant magnetoresistance, electrical and optical properties such as ferroelectricity and
quantum-size effects... They are produced by a wide variety of physical, chemical and
mechanical techniques as described in the different contributions. The understanding and the
optimisation of their physical and chemical properties need a precise knowledge of the atomic
structures. Serious attention has been paid to develop proper characterisations since the
nanometer size range of the materials often falls just below or at the resolution limit of the
conventional tools. X-ray Absorption Spectroscopy (XAS) is one of the few structural
techniques that provides information over the short-range order (interatomic distances, types
and number of first and more distant neighbours) around almost any atomic species of the
solid and that gives also the average cluster size. The contributions are presented following the
Siegel 's classification, i.e. from the zero to the dimension three.
[1]
Siegel, R. W. 1993, NanoStructured Materials, 3, 1.
I - Ultrafine particles, Clusters embedded in a matrix
Nanocermets
T.Girardeau, S. Camelio, D. Babonneau, J. Mimault.
LMP (Poitiers)
Composite materials including metallic aggregates embedded in dielectric matrices (nanocermets) have
received much attention for several years [1] due to their original magnetic and optical properties
resulting from their finite size. Optoelectronics [2], magnetic storage, energy conversion, optical filters
[3] are some potential fields of application of such nanostructured materials. They can be produced by
many different techniques, as colloidal solution, sol-gel or chemical synthesis, pulse laser deposition,
low energy cluster-beam deposition, electrochemical deposition, ion implantation and sputtering codeposition [4].
The fundamental properties of nanocermets that are used for optical applications are surface plasmon
resonance in the free-electron metallic grains, which leads to a resonance band in the absorption
spectrum. Its spectral position and half-width depend on the intrinsic electronic properties of the
aggregates and on their local surroundings. Therefore, the choice of the metal and the dielectric host,
particle size and shape, distribution and size dispersion are key factors to determine the final properties
of the nanocomposite material.
Our technical objective is to control the physical and chemical properties of the nanocermets, their
morphology and their spatial self-organization in order to get specific optical properties, i.e. a
controlled spectral position and frame of the resonance band.
Our aim is to study nanocermet films prepared by co-sputtering of the dielectric host (Si3N4) and two
noble metals. In order to get the wider range for the spectral position of the resonance, the two metals
must have electrical properties rather different, leading to different spectral positions of the absorption
32
resonance. Therefore, two pairs of metal with distinct thermodynamic behaviors are tested. On the one
hand, we will study the metastable Cu-Ag system (two resonant peaks) and on the other hand the
miscible system Cu-Al (one resonant peak). Depending on the metallic species ratio, the position and
frame of the absorption peak(s) will be modified. Post-treatment such as ion irradiation or annealing
will be considered in order to control the morphology and spatial organization of the metallic
aggregates.
The crystalline structure, the morphology, the spatial organization of the aggregates (that depend on the
used preparation techniques and on elaboration conditions) are of fundamental importance for the
understanding of their physical properties. The XAS technique will be useful to characterize the
aggregates present in the film and therefore clarify the different phases (pure metal or alloy). This
technique will also give some information on the evolution of the aggregates size after the different
post-treatments. Grazing Incidence Small Angle X-ray Scattering (GISAXS) and Transmission
Electronic Microscopy (MET) will be associated to EXAFS in order to characterize the physical and
chemical properties of the nanocermets. This fine description will be related to their optical properties,
that we can measure in our laboratory using spectroscopic ellipsometry and classical transmission and
reflection measurements.
[1] U. Kreibig and M. Vollmer, Optical properties of metal clusters (Springer, Berlin - 1995).
[2] C. Flytsanis, F. Hache, M.C Kelin, D. Ricard and P. H. Rossignal, in Progress in Optics, edited by E. Wolf
(North-holland, Amsterdam,1991) Vol. XXIX 323.
[3] A. Dakka, J. Lafait, C. Sella, S. Berthier, M. Abd-Lefdil, J.C Martin, M. Maaza, Applied Optics vol 39, n°13
(2000) 2745.
[4] T. Girardeau , S. Camelio, A. Traverse, F. Lignou, J. Allain, A. Naudon , Ph. Guérin, Journal of Applied
Physics, vol 90, n°4 (2001) 1788.
**********
Clusters embedded in matrices
A. Traverse
LURE (Orsay)
Among the different techniques used to prepare clusters in matrix, ion implantation has some
advantages. One of them consists in the possibility to prepare particles embedded in a matrix, particles
that can be studied from the point of view of their different properties such as optical, magnetical,
mechanical, transport properties… In collaboration with M. Borowski (thesis 1995), we showed that it
is possible to prepare small clusters between 0.5 et 9 nm average diameter provided the implanted ions
are non miscible in the matrix. The average size can be adjusted with the implanted fluence and postannealing treatments. Then, D. Zanghi performed magnetic measurements either with a SQUID or by
circular magnetic dichroism to obtain the magnetic moment per atom (MMA) in Ni et Co clusters
embedded in an AlN matrix (1999). The MMA decrease is interpreted as due to the interaction between
atoms located at the cluster surface and the atoms of the matrix. This is an interaction between s and d
electrons in this particular case, that leads to one atomic plane magnetically dead. In the implantation
conditions selected during these two theses (incident energy of the Ni, Co ions typically of the order of
100 keV), the clusters are close to each other, with average centre-to-centre distance of the order of 1
average diameter. They are thus magnetically interacting, as shown by FC-ZFC curves measured with
the SQUID.
The research programme in the future takes advantage of ion implantation. Implanting Co, Ni, Fe ions
in matrices different from AlN, i.e. having a more « d » character than « s » for example, provided they
are non-miscible, one can modify the cluster-matrix interactions. By playing with the incident ion
energy, particularly by increasing it, it is possible to prepare cluster far from each other and to monitor
the cluster-cluster interactions. Another possibility consists in implantation of other type of ions, such
as rare-earth to study size effect and matrix interactions on f-d hybridisations responsible for the
magnetic properties of these systems.
In this research programme, XAS plays a fundamental role since it is the only technique allowing the
chemical and structural characterisation and the diameter measurement of particles in this size range.
The detections modes, such as Total Electron Yield and fluorescence are particularly useful. The
brillance of Soleil will allow us to study more diluted samples, ie. with cluster more dispersed in the
33
matrix, thus without interaction. Combining other characterisation techniques such as RX diffraction
and RX scattering, the possibility to measure in situ properties such as electric transport, to apply
pressure on the samples, while the atomic (EXAFS) and electronic (XANES) structures are followed,
are important aspects to consider when building the sample environment.
X-Ray Absorption Study of Ti, Cu and Fe Implanted AlN, M. Borowski, A. Traverse and J. Mimault, Acta Physica
Polonica A 86 (1994) 713.
Phase Formation after High Fluence Implantation of Fe in AlN : A Mössbauer Study, M. Borowski, A. Traverse
and J.P. Eymery, Nucl. Instr. and Meth. B 122 (1997) 247.
Magnetic properties of Ni clusters embedded in AlN by x-ray magnetic circular dichroism, D. Zanghi, A.
Delobbe, A. Traverse and G. Krill, J. Phys. : Condens. Matter 10 (1998) 9721.
Structural Characterisation of Ni Clusters in AlN via X-ray absorption, X-ray diffraction and transmission
electron microscopy, D. Zanghi, A. Traverse, J-P. Dallas and E. Snoeck, Eur. Phys.J. D 12 (2000) 171.
Structural and magnetic properties of co/aln multilayers, D. Zanghi, A. Traverse, F. Petroff, J.-L. Maurice, A.
Vaures, J.P. Dallas, J. Appl. Phys. 89 (2001) 6329.
Reduced magnetic moment per atom in small Ni and Co clusters embedded in AlN, D. Zanghi, C.M. Teodorescu,
F. Petroff, H.Fischer, C. Bellouard, C. Clerc, C. Pélissier and A. Traverse, J. Appl. Phys. 90 (2001) 6367.
Atomic surrounding of Co implanted in AlN at high energy A. Traverse, A. Delobbe, D. Zanghi, M. Renteria, M.
Gailhanou, J. Synchrotron Rad. 8 (2001) 51.
**********
Thin or thick films from clusters
L. Bardotti, V. Dupuis, A. Hoareau, B. Masenelli, P. Mélinon,
A. Perez, B. Prével, J. Tuaillon-Combes
DPM (Lyon)
The « Clusters » group of the Département de Physique des Matériaux de Lyon is a current user
of synchrotron radiation (SR) at LURE, in view of the numerous experiments proposals submitted from
ten years which concerned a great number of beam lines (EXAFS, SEXAFS with MBE environment,
anomalous Diffraction, XPS, XMCD, high pressure physics…).
Sometimes, experiments were also realized at the ESRF-Grenoble for high flux, high sensibility or/and
high energy intensity experiments necessities.
We are interested by the synthesis and properties of nanogranular thin films obtained from Low Energy
Clusters beam Deposition (LECBD), where the nanoparticules are produced in the gas phase from an
original vaporization source. Various characterization techniques are used as a function of the nature of
the elements constituting the clusters. We can mention microscopy techniques : AFM, STM, TEM and
HRTEM, X-rays diffractions : reflectometry, in grazing incidence, the Raman, Photoelectron and Auger
spectroscopies.
Two research axes are concerned by SR measurements : magnetic clusters with transition metal and rare
earth (TM and RE) and covalent clusters based on silicon (SixC1-x and SixGe1-x). We prepare either thick
films especially assemblies of clusters embedded in a matrix from an specific co-deposition technique
or discontinuous thin films (i.e. before the percolation threshold) in particular to study auto-organisation
on a functionalized substrate.
So, from FEFF8 code simulations, we were able to well define the cluster/matrix interface for Coclusters embedded in miscible (as niobium or platinum ones) (respectively, immiscible (as silver one))
matrices and it diffused (resp. sharp) character. For the alloyed interfaces we were able to relate their
structural and magnetic properties : from magnetically dead (as in the Co/Nb case) until exacerbated
magnetic interface (as in the Co/Pt one).
We also showed the first experimental evidence of a predicted «icosahedral» compact network in the
case of a mixed C60Si clusters deposit. At the same time, we study clathrate structures based on silicon
elements and prepared by chemical process. Such structures formed a periodical network of connected
cage molecules. Foreign atoms (as sodium) can be sited inside the silicon cage. At the edge of this
foreign atom, EXAFS simulations can lead to a precise position of the «encaged» atom and of its
environment. So, we clearly evidenced very strong «Jahn Teller» effects in such materials.
34
Cobalt and nickel assembled thins films obtained by low energy neutral cluster beam deposition, J.Tuaillon, V.
Dupuis, P. Melinon, B. Prevel, M. Treilleux, A. Perez, M.Pellarin, J.L. Vialle, M. Broyer, Phil. Mag. A, 76, 493
(1997).
Structure and magnetism of well-defined cobalt nanoparticles embedded in a niobium matrix, M. Jamet, V.
Dupuis, P. Melinon, G. Guiraud, A. Perez, W. Wernsdorfer, A.Traverse, B. Baguenard, Phys. Rev. B 62, 493,
(2000).
Nanostructured Co/Ag and Co/Pt thin films from clusters, M. Negrier, J. Tuaillon, V. Dupuis, P. Melinon, A.
Perez, A. Traverse, Phil Mag A (2001).
X-ray Photoemission, SEXAFS and magnetic dichroïsm study of the Ferromagnetic/Superconducting
interface prepared under UHV: From cobalt clusters embedded in a Niobium matrix samples (Part I) and from
Co/Nb thin bilayers (Part II), M. Jamet, V. Dupuis, J.Tuaillon-Combes, P. Melinon, A. Perez, N. Barrett, P. Le
Fevre, C. Teodorescu, F. Bertran, B.Bouchet-Fabre, A. Traverse, J. Vogel, C. Thirion, W. Wernsdorfer à
soumettre à Phys. Rev. B (2001).
II- Thin Films
In this section are gathered two contributions concerning two-dimension systems, either
prepared in a classical way, i.e. ex situ or prepared in situ. In the last case, surface EXAFS
(Surface Extended X-ray Absorption fine Structure) can be performed.
Thin films from different techniques
I. Arcon
Nova Gorica Polytechnics (Slovenia)
The field of research of our group is focused on thin films and coatings prepared by different
techniques. We follow the evolution of different phases in ion-beam mixed transition metal aluminides,
used as diffusion barriers to suppress hillock formation and to increase electromigration, and as wear
resistance coatings. The effect of Cesium and Iodine incorporation into ZrO2 and spinel crystal structure
by ion beam implantation is characterized.
We also study the formation of clusters in crystalline or polymer substrates by ion beam deposition, in
relationship with the determination of crystal structure and size distribution of clusters (for example:
CdS nanocrystals embedded in SiO2 amorphous matrix, Ni, Cu, and Zn in polymers or SiO2 ...).
The structure of PZT thin film amorphous precursors and ceramics on sapphire or platinum substrate
prepared by different sol-gel synthesis routes is investigated. In lead/zirconate/titanate solid solution
based ceramics (PZT) small variations of reaction conditions lead to different product morphologies.
From the point of view of the technique itself, we carry on a program for EXAFS calibration in order to
determine the size parameters of clusters, with measurements performed on standard metal clusters with
a well-known and narrow size distribution.
I. Arcon, M. Mozetic, A. Kodre, J. Jagielski, A. Traverse, J. Synch. Rad. 2001 8 493-495.
**********
Surface EXAFS in the X-ray range
1
CEA (Saclay), 2LURE (Orsay)
The continued miniaturisation of electronic devices is leading us into the domain of
nanostructures, which exhibit novel electronic or optical properties different from those of bulk matter.
In the field of magnetic storage devices, the interest in nanostructures has intensified in the last decade
due to the discovery of oscillatory magnetic coupling [1] and giant magnetoresistance in multilayers [2].
Artificially layered materials involving magnetic and non-magnetic elements are the foundation of
magnetic recording in today's computers and it is predicted that this technology will continue evolving.
Advances in growth techniques lead to sophisticated nanostructures which are interesting both for
35
applications and from a fundamental point of view. For example, recent effort has been devoted to
fabricating wires and dots. For semiconductors, the potential applications are single electron transistors
or quantum-dots lasers.
However, the controlled fabrication of ordered metal and semiconductor nanostructures at
surfaces remains a difficult challenge. Their size, shape and structure at the atomic scale were shown to
be very dependent on the conditions of preparation, leading to different physical or chemical properties.
Moreover, clear explanations of the physical properties of nanostructures (e.g. magnetic properties), as
well as improvements of theoretical models, require a precise characterisation of the film
crystallography and of the first interface layers.
Surface EXAFS [3] is a very attractive technique to characterise crystallographic structure of
thin films or nanostructures even at the very first stages of growth (below one monolayer). It allows the
in-situ study of thin films deposited on crystalline substrates which can stabilize in metastable phases
and gives to a high precision the shape of the first neighbour shell of a selected atom [4], including its
possible asymmetry [5] and its thermal broadening [6, 7] which is related to the elastic force constant
between nearest neighbours in the film. Moreover, the linear polarization of the synchrotron radiation
reveals information about a possible anisotropy of the crystallographic structure. In addition, EXAFS is
a selective method : films of any thickness, coated films and multilayers can be characterised with the
same precision.
Surface EXAFS is complementary to other surface techniques: the study of local
crystallographic structure can be completed with other surface techniques such as STM and Surface XRay diffraction which study the sample at another scale. Moreover, all the results can be connected to
electronic and magnetic properties with PEEM or XMCD measurements.
What we propose, is to promote a Surface EXAFS experiment in the X-ray range on the XAS
beam line at SOLEIL.
At present, few set-ups are available for such experiments, which need sample preparation
facilities in UHV and in situ detection of the EXAFS signal (total yield detection and/or energy
resolved fluorescence detection). Recent works have been done at LURE (DW21 beam line) [8-11], at
Daresbury (beam line 4.2) [12] and at ESRF (italian beam line GILDA) [13].
Most of the samples under examination with this technique are thin magnetic film deposited
either on metallic or semiconductors substrates [8-13]. The very recent works concern magnetic
nanostructures with low lateral size done by evaporation on vicinal or reconstructed surfaces [14-16] or
structured after deposition [17]. It is clear that these studies will develop in the future; the flux available
at SOLEIL will allow the study of sample with a lower density of plots or wires. These studies will
require an STM experiment connected or near the SEXAFS chamber. Other systems are also interesting
to study : thin oxides layers, samples prepared by laser deposition … which have always been studied
by EXAFS ex-situ because of the particular sample preparation procedure. Like for thin magnetic films,
the knowledge of their crystallographic structure during growth is mandatory to understand their
physical properties.
This experiment will concern mainly three scientific themes, and the concerned community is listed
below :
-metal/metal interfaces
*thin magnetic films : IPCMS Strasbourg [9,15] (B. Carrière, C. Boeglin, F. Scheurer), LPM Nancy[11] (S.
Andrieu), CEA Saclay SPCSI [8,16].
*autorganized metallic interfaces : GPS Paris (S. Rousset, B. Crozet), CEA Saclay SPCSI.
-metal/semiconductor interfaces : LMCP Paris (V. Etgens), LPSE Mulhouse [10] (G. Gewinner, M. H.
Tuilier).
-oxides/metal interfaces
* in-situ thin films : CEA Saclay SPCSI (M. Gautier, S. Gota), Laboratoire de Recherche sur la réactivité des
solides Dijon (S. Bourgeois).
* spin valves interfaces : CNRS LCR Thales Orsay (F. Petroff, H. Jaffrès), Laboratoire Physique Matière
condensée Toulouse.
[1] P. Grünberg, R. Schreiber, Y. Pang, M. B. Brodsky, H. Sower, Phys. Rev.Lett. 57, 2442 (1986).
[2 ] M.N. Baibich, J.M. Broto, A. Fert, F. Nguyen Van Dau, F. Petroff, P. Etienne, G. Creuzet, A. Friederich, J.
Chazelas, Phys. Rev. Lett. 61, 2472 (1988).
[3] J. Stöhr, D. Denley, and P. Perfetti, Phys. Rev. B 18, 4132 (1978); P. H. Citrin, P. Eisenberger, and R. C.
Hewitt, Phys. Rev. Lett. 41, 309 (1978).
[4] D. E. Sayers, E. A. Stern and F. W. Lytle, Phys. Rev. Lett. 27, 1204 (1971).
36
[5] G. Bunker, Nucl. Instr. Meth. 207, 437 (1983) ; H. Magnan, D. Chandesris, G. Rossi, G. Jezequel, K.
Hricovini, and J. Lecante, Phys. Rev. B 40, 9989 (1989).
[6] R. B. Greegor and F. W. Lytle, Phys. Rev. B 20, 4902 (1979).
[7] P. Roubin, D. Chandesris, G. Rossi, J. Lecante, M. C. Desjonquères, and G. Tréglia, Phys. Rev. Lett. 56, 1272
(1986) ; P. Roubin, D. Chandesris, G. Rossi, and J. Lecante, J. Phys. F 18, 1165 (1988).
[8] P. Le Fèvre et al. Eur. Phys. Journal B 10, 555 (1999) ; N. Marsot, et al., Phys. Rev. B 59,3135 (1999); H.
Magnan et al. Surf. Sci. 454-456, 723 (2000).
[9] C. Boeglin et al., Phys. Rev. B 60 4220 (1999).
[10] P. Shieffer et al., J. Synchrotron Rad. 6, 784 (1999).
[11] S. Andrieu et al., J. of Magn. Magn. Mat. 198-199, 285 (1999).
[12] S . P. Harte et al. Surf. Sci. 424, 179 (1999) ; G.C. Gazzadi et al. Applied Surf. Sci. 162-163, 198 (2000);
M.T. Butterfield, M. D. Crapper, Surf. Sci. 454-456, 719 (2000) ; S. D'Addatto, P. Finetti, Surf. Sci. 471, 203
(2001).
[13] F. Rosei, et al., Thin solid films 369, 29 (2000) ; F. d'Acapito et al., Surf. Sci. 468, 77 (2000).
[14] S. d'Addato et al., Surf. Sci. 442, 74 (1999).
[15] S. Cherifi et al., Phys. Rev. B 64, 184405 (2001).
[16] A.Chaumin Midoir et al., Applied Surf Sci. (2002).
[17] H. Jaffres, et al. Phys. Rev. B 61, 14628 (2000).
[18] K. Tsuji et al., Surf. and Interface analysis 27, 132 (1999) ; Y. Hasagawa, J. of Sci Vac. B 18, 2676 (2000).
III- Layered nanophase systems
Materials with layered structure often have anisotropic properties related to their
bidimensional organization. The linear polarisation of the synchrotron radiation combined
with EXAFS, enables to display the crystallograpic anisotropies and allows for example the
understanding of the magnetic exchange mechanisms between cations or the grafting
processes.
Hydrothermal synthesis of nickel silicates
M. Richard-Plouet, M. Guillot et S. Vilminot.
IPCMS (Strasbourg)
Numerous works are dealing with magnetism of low dimensionnal structures. In order to
understand the exchange mechanisms, a fine structural characterisation of the studied compounds is
necessary to model the magnetic behaviour. Our studies are focused on the hydrothermal synthesis of
nickel silicates obtained from transition metal acetate and a propylamine modified alkoxysilane
(Si(OC2H5)3C3H6NH2). Depending on the experimental conditions, different phases were isolated
presenting a transition towards a ferromagnetic ordering with a ferromagnetic ground state at low
temperature, with Ni/Si≈3/2 or an antiferromagnetic one with Ni/Si≈3/1.
These compounds are bad crystallised finely divided powders. Powder diffraction data are too poor to
allow a structural model refinement, due in particular to the small grain size. The interlayer distance is
close to 21 Å for both compounds.
However, from several spectroscopies (IR and XPS), Ni2+ are known to be located in octahedral sites
sharing edges as in the hydroxide structure (brucite). Ni K edge EXAFS measurements confirm on the
one hand that Ni cations are in octahedra with 2.05 (± 2) Å Ni-O distances, in agreement with the
expected value. On the other hand, they allow us to bring to the fore the existence of 6 second Ni
neighbours at 3.11 (± 2) Å together with 2 Si neighbours at 3.24 (± 2) Å et 3.29 (± 2), for the two silicates.
Moreover, it was possible to perform orientated self supported films which were also recorded at the Ni
K edge for different incident angles using the polarised character of the synchrotron beam. Such an
experiment was already successfully applied on minerals and gave structural information on
phyllosilicates from which our compounds are derived. Thus we record the absorption coefficients
(χ(α)) for α=70, 60, 50, 35, 20, 0°, where α is the angle between the incident beam and the normal to
the preparation.
Experimentally α=90° spectrum (χ(90°)) can not be performed because the beam would have to be
tangent to the film surface. Nevertheless the latter can be calculated from the other ones by
37
extrapolating χ(α) = (χ(0°)-χ(90°))cos2α+χ(90°). The linear relation between χ and cos2α has been
checked, for every k values. The polarisation effect strongly affect the Fourier transforms of EXAFS
oscillations. This is due to the layered structure of the compound and its texture. In case α=90°, it is
clearly seen that the contribution of the out of plane scattering atoms is lowered. Structural parameters
such as the flattening angle of the NiO6 octahedra were evaluated : 58 and 60°, which are expected
values. The trioctahedral nature of the layers was confirmed. Lastly, we demonstrated that the
condensation mode of the Si tetrahedra is different from the one observed in clay structures.
Durand G., Vilminot S., Richard-Plouet M., Derory A., Lambour J.P., and Drillon M., J. Solid State Chem., 131,
335, (1997).
Richard-Plouet M., Vilmino S., J. Mater. Chem., 8(1),131-137, (1998).
Richard-Plouet M., Vilminot S., Solid State Sc., 1, 381-393, (1999).
Guillot M., Richard-Plouet M., and Vilminot, S., in press J. Mater. Chem., (2002).
Richard-Plouet M., Vilminot S., Guillot M., Kurmoo M., in preparation.
**********
Layered Double Hydroxides and related materials
LMI (Clermont-Ferrand)
Our research group is involved in the synthesis, characterization and optimization of the
versatility of Layered Double Hydroxides (LDH) and relative materials (hydrocalumite and organic
exchanged derivatives). They are described with the general formula MII1-xMIIIx(OH)2x+ Az-x/z. nH2O
(noted as [MIIrMIII-A], with r=1/x -1), in which the substitution of a part of the divalent cations by
trivalent gives rise to a net positive charge. This excess of charge is counterbalanced with anions
present in the interlamellar domain. LDH materials are ideally described according to the hydrotalcite,
natural anionic clay of composition Mg2Al(OH)6(CO32-)0.5.2H2O.
The question of homogeneity in the layers is often questioned. This is of importance for catalytic
applications for which large surface area combined with good metal dispersion is needed. With the
ever-growing demand for multi-properties materials, many cations are incorporated in LDH framework,
such as tetravalent cations.
This is illustrated by some recent publications (see references), where other techniques of
characterization felt short to access to such informations.
It is of great importance for our activity to find a beam line at SOLEIL for the X-ray absorption in the
4-40 keV energy range, and equiped with cryogenic apparatus and furnace working with different
atmospheres (in-situ measurements).
Local order of the transition metals for the substitution (Co1-yCuy)2Al(OH)6Cl nH2O (0<y<1) in a copperaluminium layered double hydroxide-like phase, F. Leroux, El M. Moujahid, H. Roussel, A.-M. Flank, V. Briois,
J.-P. Besse. Clays and Clay Miner., sous presse.
Effect of layer charge modification for Co-Al layered double hydroxides: study by X-ray absorption spectroscopy.
F. Leroux, El. M. Moujahid, C. Taviot-Guého and J-.P. Besse. Solid State Science, 3, 81-92, 2001.
Delamination and restacking of layered double hydroxides. F. Leroux, M. Adachi-Pagano, M. Intissar, S.
Chauvière, C. Forano and J.-P. Besse. J. Mater. Chem., 11, 105-112, 2001.
Trivalent cation substitution effect into Layered Double Hydroxides (Co2FeyAl1-y(OH)6Cl. nH2O : study of the
local order. Ionic conductivity and magnetic properties. M. Intissar, R. Segni, C. Payen, J.-P. Besse, F. Leroux. J.
Solid State Chemistry, submitted.
Cationic order and structure of [Zn-Cr-Cl] and [Cu-Cr-Cl] Layered Double Hydroxydes : a XRD and EXAFS
study. H. Roussel, V. Briois, E. Elkaim, A. De Roy and J.P. Besse. J. Phys. Chem. B, 104, 5915-5923, 2000.
Study of the formation of the Layered Double Hydroxide [Zn-Cr-Cl]. H. Roussel, V. Briois, E. Elkaim, A. de Roy,
J. P. Besse and J. P. Jolivet. Chem. Materials, 13, 329-337, 2001.
38
IV- Nanophase Materials prepared by “Soft Chemistry”
The development of new materials with high performance requires a good knowledge
and control of the preparative routes. Among the techniques of preparation, Soft Chemistry,
synthesis methods are today commonly used because of their numerous advantages over
conventional routes like higher purity and homogeneity of the final materials, formation of
thermodynamically metastable phases, versatility of morphology control for the so-prepared
materials (monoliths, nanoparticles, films, fibers etc…) and economic process [1].
In such chemistry, the precursor compound holds a considerable importance and much
efforts are devoted to design specific precursors or to modify the reactivity of existing ones, in
particular by varying the nature and configuration of ligands. Indeed the nature of the
precursor will influence the rate of reaction, the obtained final product [1] and of course its
application field. To exemplify this point, we can mention the sol-gel chemistry of zirconium
for which in presence of sulfate anions the formation of colloidal suspensions made of
isotropic nanoparticles capped in surface by ligands [2] has been evidenced whereas the
formation of layered phases [3] is well known in presence of phosphate anions. With the
former system, thermoreversible sol-gel transition [4] which presents potential applications in
the development of smart windows has been evidenced whereas the second ones displays
applications in ion exchange, catalysis and high temperature ion conductivity [5]. In fact soft
chemistry methods are largely topotactic since the final product retains the “memory” of the
precursor structure. For example in the acido-basic processes of hydrolysis-condensation
involved in sol-gel chemistry the condensation of blocks takes place at the protonated sites that
are the most basic anionic sites. But this basicity depends on the geometry of the sites, the
distances to the neighbouring cations, and the nature of these cations. Consequently, the
knowledge of the structure of precursors, and more generally, of the different building blocks
during the solid state growth is of crucial importance to optimise the process and the
properties of the final materials. Since the assembly of the blocks takes place in solution and
often leads to amorphous or poorly crystallised materials, structural techniques, like the XAS
are of prime importance to aid the researcher in reaching a fuller understanding of the
preparative routes.
Besides the design of new precursors, the control of the processing of the materials
(gelation, ageing, syneresis, shaping, drying, sintering, …) is also of prime importance on the
optimisation of the properties of the materials. Dealing with nanometer blocks, XAS allows to
determine the nanocrystallite size of these blocks, with an accuracy all the better as these
objects are small (typically less than 2-3 nm).
[1] Brinker, C. J., and Sherer, G.W. 1990, Sol-Gel Science, The physics and Chemistry of Sol-Gel Processing,
Academic Press, Inc., San Diego.
[2] L. Chiavacci, S. H. Pulcinelli, C. V. Santilli, V. Briois, Chem. Mater 1998, 10, 986-993.
[3] J. M. Troup, A. Clearfield, Inorg. Chem.1977 16 3311-3314.
[4] L. Chiavacci, C. V. Santilli, S. H. Pulcinelli, A. Craievich , J. Appl. Cryst. 1997 30 750-754.
[5] A. Clearfield Chem. Rev. 1988 88 125-148.
39
Lithium battery, Pigments – UV Absorbers –
Catalysts and Doping oxides
Guy Ouvrard
IMN (Nantes)
In the recent past, the Laboratoire de Chimie des Solides (LCS) of IMN has largely used SAX in
order to characterize more or less divided, amorphous or structurally modified compounds. Moreover,
the edge part of XAS spectra (XANES) has been especially considered for the determination of the
oxidation state of elements. This is of great importance for a better knowledge of the redox processes
taking place in the battery materials, in order to characterize the chemical bond, or in some cases to
obtain a detailed experimental electronic structure of a solid. This last point is an essential part of a
general activity using the combination of various experiments and electronic band structure calculations
in order to precisely define it.
It appears now very clearly that the size, the morphology and the conditioning of active species, is a
crucial aspect of the performances in many applications we are interested in. We are presently largely
involved in the synthesis, elaboration and characterization of materials for catalysis, color, UV
absorption, energy storage, waste treatment … In these domains, soft chemistry synthesis methods,
leading sometimes to very small or disordered particles, are very powerful. We may exemplify the
importance of XAS for the LCS with three main examples :
- Lithium battery materials. Upon functioning of such batteries, the active phases are transformed
in their atomic arrangements, in local or general structural changes, and in the oxidation state of at
least one element. More generally, we may consider that the chemical bond is modified. In this
matter a detailed study of the XAS edge shape and position has proved to be a powerful tool. To
develop and improve such experiments, it is essential to have a good access to high energy X-ray
(K edge of transition elements) and low energy X-ray (L edges of transition elements and oxygen K
edge). In a near future, polymer /transition metal oxides composites will be used as electrode
battery materials and a good spatial resolution will be of a great interest. Last point, we are very
much interested in the capability of studying such batteries in situ during the functioning. Such
experiments would largely benefit of a high photon flux.
- Pigments -UV Absorbers - Catalysis. The morphology of the particles is often a key point in the
properties and, in order to control it, soft chemistry methods have been proved very efficient. In this
case, EXAFS allows determining the atomic arrangement and the reaction process. Moreover, the
understanding of the property comes through experimental approach of the electronic structure. For
these studies, it is absolutely essential for us to access to X-ray source at both high and low energy
range.
- Doping of oxides. Intense fundamental studies are aiming to understand some physical properties
in transition metal oxides : superconductivity, giant magnetoresistance, spin liquids. The first step
in this study is the elaboration of well-defined materials as structure, stoichiometry, doping. XAS is
used to precisely define the electronic, magnetic and local structural effects of such doping.
To summarize, it is essential for us to have an easy and important access to X-ray intense sources as
they can be delivered by SOLEIL. In many cases (batteries, synthesis, reactivity with gases or light
beam) dynamic behavior will use the high brilliance. We are very interested in a high spatial resolution
and experimental set up as low and high temperature and in situ electrochemical experiments.
Intercalation Chemistry
1- Electronic structure and charge transfer in lithium and mercury intercalated titanium disulfides, P. Moreau, G.
Ouvrard, P. Gressier, P. Ganal and J. Rouxel, J. Phys. Chem. Solids 57 (1996) 1117-1122.
2- Sulfur K-edge X-ray-absorption study of the charge transfer upon lithium intercalation into titanium
disulfide, Z.Y. Wu, G. Ouvrard, S. Lemaux, P. Moreau, P. Gressier, F. Lemoigno and J. Rouxel, Phys. Rev.
Lett. 77 (1996) 2101-2104.
3- XAFS study of charge transfer in intercalation compounds, G. Ouvrard and Z. Wu, Nucl. Instr. Meth. Phys.
Res. B133 (1997) 120-126.
Battery materials
4- V2O4S, a new transition metal oxysulfide as positive for lithium batteries. G. Tchangberdji, D. A. Odink and
G. Ouvrard, J. Power Sources 43-44 (1993) 577-581.
40
5- On the nature of Li insertion in tin composite oxide glasses, G.R. Goward, F. Leroux, W.P. Power, G.
Ouvrard, W. Dmowski, T. Egani and L.F. Nazar, Electrochem. Solid State Lett. 2 (1999) 367-370.
6- X-ray absorption spectroscopy study of the structural and electronic changes upon cycling of LiNiVO4 as a
battery electrode, C. Rossignal, G. Ouvrard and E. Baudrin, J. Electrochem. Soc. 148 (2001) A869-A877.
Synthesis
7- Room temperature synthesis of highly disordered a-Ni2P2S6, P. Fragnaud, E. Prouzet, G. Ouvrard, J. L.
Mansot, C. Payen, R. Brec and H. Dexpert, J. Non Cryst. Solids 160 (1993) 1-17.
8- XAS study of mesostructured TiO2, a potential lithium ion battery anode material, F. Lerous, P.J. Dewar, M.
Intissar, G. Ouvrard, and L. F. Nazar, Electrochemical Society Proceedings, 99-24 (2000) 273-279.
Electronic structure
9- Experimental and theoretical studies of the electronic structure of TiS2, Z.Y. Wu, F. Lemoigno, P. Gressier,
G. Ouvrard, P. Moreau, J. Rouxel and C.R. Natoli, Phys. Rev. B54 (1996) 11009-11013.
10- Interpretation of preedge features in the Ti and S K-edge x-ray-absorption near-edge spectra in the layered
disulfides TiS2 and TaS2, Z.Y. Wu, G. Ouvrard, P. Moreau and C.R. Natoli, Phys. Rev. B 55 (1997) 95089513.
Pigments
11- Absence of chromatic effect : crystal relaxation around CeIII in Y1-xCexPS4 (0<x<1), G. Gauthier, Y. Klur,
A. Pourpoint, S. Jobic, G. Ouvrard, R. Brec, D. Huguenin, P. Macaudiere, International Journal of Inorganic
Materials, 2 (2000) 717-722.
Catalysis
12- EXAFS identification of the active species in supported niobium sulfide hydrotreatment catalysis, N. Allali,
E. Prouzet, A. Michalowicz, V. Gaborit, A. Nadiri and M. Danot, Appl. Catal. A 159 (1997) 333-354.
13- Two cation disulfide layers in the WxMo1-xS2 lamellar solid solution, C. Thomazeau, C. Geantet, M.
Lacroix, V. Harle, S. Benazeth, C. Marhic and M. Danot, J. Solid State Chem. 160 (2001) 147-155.
Doping
14- Electronic structure of a hole doped oxide with a quasi-1D crystal structure Y2-x(Sr,Ca)xBaNiO5, F. X.
Lannuzel L, E. Janod, C. Payen, G. Ouvrard, P. Moreau, O. Chauvet, P. Parent and C. Laffon, J. Alloys
Comp. 317-318 (2001) 149-152.
**********
Smart oxides layers
C. V. Santilli1, S. H. Pulcinelli1, K. Dahmouche1, V. Briois2 and S. Belin2
1
IQ UNESP, 14800-900 Araraquara, Brésil, 2 LURE
In the past 10 years, our group, in close collaboration with V. Briois working in the framework
of french-brazilian research cooperation programs, has been involved in systematic studies of structureproperties relationships in various oxide systems and organically modified hybrids listed briefly below.
Ceramics and Thin Films based on SnO2
In Collaboration with A. Larbot, IMPM, Montpellier, T. Chartier, ENSCI, Limoges, D. Stuerga and D.
Chaumont, LRRS, Dijon.
SnO2 films are transparent to visible light and reflect infrared radiation ; they present an
electrical resistivity of about 10-3 to 10-1Ωcm. These optical and electrical characteristics are suitable
for the elaboration of electro-optical, photoelectrochemical, photoelectrocatalytical and
electrochromical devices. Our interest is the development of supported SnO2 membranes for
ultrafiltration and coatings used for the protection of fluoride glasses against water. Such developments
first required fundamental studies of drying [1] and sintering processes [2]. The information obtained by
EXAFS on the crystallite growth (e.g. crystallite size and anisotropy) during the first stages of sintering
combined to the information obtained by SAXS and porosimetry on the pore distribution were useful to
optimise the permeability of the ultrafiltration membranes [3, 4]. The preparation of crack-free
membranes was achieved by adding surface modifying molecules into the colloidal suspensions. The
structural study performed by EXAFS on the surface modified SnO2 particles and membranes fired at
different temperatures allowed to determine the key parameters of preparation (optimal surfactant
concentration and sintering temperature), and, consequently to rationalise the process [5, 6]. Finally the
structural study by EXAFS of the role of dopants (e.g. Cu, Nb) on the densification of monolithic
41
bodies [7, 8] was also useful to prepare transparent and hermetic coatings used to shield fluoride glasses
against corrosion [9]. In this case, the formation of substitutional solid solutions was evidenced and
discussed in terms of lattice diffusion and crystal growth processes.
Quantum-sized Nanoparticles and Thin Films based on ZnO
In Collaboration with A. Smith, ENSCI, Limoges
The method proposed by Spanhel and Anderson [10] in 1991 is commonly used to obtain ZnO
nanometer-sized particles in order to prepare nanoparticulate ZnO films with good electrical
conductivity, high visible transmittance and infrared reflectance. These polycrystalline films have
potential application in various semiconductor devices like solid-state displays, photovoltaic cells and
planar waveguides. It was outlined that nanometer-sized particles obtained by the Spanhel method are
not pure ZnO nanoparticles and that the presence of reaction products plays a dominant role in the
evolution of visible luminescence of the films prepared from the so-obtained colloidal suspensions [11].
The EXAFS characterisation carried out during the formation of ZnO nanoparticles under different
catalysis and temperature conditions allowed to identify the oligomeric Zn4O(COOCH3)6 compound as
the precursor [12] and the subproducts of the hydrolysis-condensation reactions. Such EXAFS studies
were incomparable to rationalise the formation of colloidal suspensions suitable for the preparation of
ZnO thin films with strong luminescence and electrical properties [13, 14].
Alkali-doped Siloxane Poly(oxopropylene) Hybrids
In Collaboration with P. Judeinstein, Laboratoire de Chimie Structurale Organique, UPS - Orsay
The mixed organic-inorganic solid state chemistry is actually the subject of intense researchs
because of many opportunities for applications in different fields such as batteries, sensors,
electrochromic and photochromic devices, data storage, catalysis … [15]. A novel class of solid
electrolytes called ORMOLYTES (Organic-Modified Electrolytes) which are based on hybrid materials
constituted of oligopolyoxyethylene chains grafted to a siliceous network have emerged in the past few
years [16-17]. In these materials, the polymer could act as a “solid” solvent for numerous chemical
species, while the structural silica network mechanically strengthens the final material. Specific
physical properties can be obtained by dissolving suitable doping agents within such network, for
example, alkaline salts and polymetalates, which induce ionic conductivity [17] and photochromic
properties [18] respectively, while luminescent properties are induced by rare-earth doping [19].
Recently we have developed lithium-doped siloxane-polyoxyethylene (PEO) or siloxanepolyoxypropylene (PPO) solid ionic conductors [20] which exhibit high transparency, good ionic
-4
−1
-1
conductivity (~ 10 Ω .cm ), better chemical stability and mechanical properties than classical
organic conducting polymers. In order to optimise the conduction properties of these materials we have
studied the connectivity between the organic and inorganic phases and the mobility of the structural
network and active ionic species by different characterisation techniques (NMR, XRD, DSC, SAXS,
EXAFS). In the case of sodium and potassium doped hybrids [21-22], XAS is particularly fruitful to
discriminate different environment of doping ions and to establish a relationship between local structure
and ionic conductivity. In particular we showed that the ionic conductivity is dependent of the amount
of species involved in interactions with the polymer in agreement with the mechanism of segmental
motion.
In the future, taking advantages of the brillance of the SOLEIL source, we plan to develop
experiments in which dynamic measurements of the property of interest would be investigated, e.g.
structural change of the environment of alkali ions in ORMOLYTES during the conduction process or
dynamic study of corrosion processes of uncoated and coated fluoride glasses.
Needs in an absorption beam line at SOLEIL :
In the EXAFS studies on nanomaterials prepared by soft chemistry, we try to understand the role of
42
different processing parameters (T, pH, nature of ligands and so on…) on the structure of precursors
and final products. Such characterizations are carried out on isolated solid materials (powders obtained
by freeze drying, centrifugation …) but also in solution.
We have interest to study the matrix, i.e. the cationic metal but also sometimes the anionic species used
as complexing ligands such a sulfate, chlorine, phosphate …. This requires measurements in
transmission for bulk materials, in total electron yield or fluorescence for supported films in a large
energy range. Typically 1.5 to 35 keV.
We are also interested to study the dopant. This requires measurements in fluorescence with high
efficiency for the detection limit when dealing with the characterization of dopant in thin films.
Hydrolysis-condensation reactions, gelation and sintering processes must be characterized in a
dynamic way by EXAFS. Quick-EXAFS data acquisition must be available for this purpose, combined
with techniques like UV-Vis spectroscopy, light scattering techniques, Differential Scanning
Calorimetry ...
[1] V. Briois, C. V. Santilli, S. H. Pulcinelli, G. E. S. Brito J. Non Cryst. Solids 1995, 191, 17-28.
[2] G.E.S. Brito, V. Briois, C. V. Santilli, S. H. Pulcinelli J. Sol-Gel Sc. and Tech., 1997, 8, 269-274.
[3] L. R. B. Santos, S. . Pulcinelli, C. V. Santilli, J. Sol-Gel Sc. and Tech., 1997, 8, 477-481.
[4] L. R. B. Santos, S. . Pulcinelli, C. V. Santilli, J. Mem. Sc., 1997, 127, 77-86.
[5] L. R. B. Santos, S. Belin, V. Briois, C. V. Santilli, S. H. Pulcinelli, A. Larbot, accepted in J. Sol-Gel Sc. and
Tech., 2002.
[6] S. Belin, L. R. B. Santos, V. Briois. A. Lusvardi, C. V. Santilli, S. H. Pulcinelli, T. Chartier accepted in
Langmuir 2002.
[7] C. V. Santilli, S. H. Pulcinelli, G. E. S. Brito, V. Briois J. Phys. Chem. B, 1999, 103, 2660-2667.
[8] V. Briois, S. H. Pulcinelli, C. V. Santilli J. Mat. Sc. Lett., 2001, 20, 555-557.
[9] A. P. Rizzato, Ph D Thesis (UNESP-Araraquara Brazil and Dijon, France 2002).
[10] L. Spanhel, M. A. Anderson, J. Am. Chem. Soc. 1991, 113, 2826.
[11] S. Sakohara, M. Ishida, M. A. Anderson, J. Phys. Chem. 1998, 102, 10169.
[12] M. Tokumoto, V. Briois, C. V. Santilli, S. H. Pulcinelli, accepted in J. Sol-Gel Sc. and Tech., 2002.
[13] M. Tokumoto, Ph D Thesis (UNESP-Araraquara Brazil and Limoges, France 2000).
[14] M. Tokumoto, A. Smith, C. V. Santilli, S. H. Pulcinelli, E. Elkaim, A. Traverse, V. Briois, accepted in Thin
Sol. Films, 2002.
[15] F.M. Gray, Solid Polymer Electrolytes, Fundamentals and Technological Applications; VCH Publishers:
New York, 1991.
[16] M. Armand, Adv. Mater. 2 1990 127.
[17] P. Judeinstein, J. Timan, M. Stamm and H. Schmidt, Chem. Mater. 6 1994 127.
[18] P. Judeinstein and H. Schmidt; J. Sol-Gel Sci. Tech. 3 1994 189.
[19] S. J. L. Ribeiro, K. Dahmouche, C.A. Ribeiro, C.V. Santilli, S.H. Pulcinelli, J. Sol-Gel Sci. Tech. 13 1998
427.
[20] K. Dahmouche, C.V Santilli, M. da Silva, C.A Ribeiro, S.H Pulcinelli, and A. F Craievich, J. Non.-Cryst.
Solids 247, 108 1999.
[21] J. A. Chaker, K. Dahmouche, V. Briois, C. V. Santilli, S. H. Pulcinelli, P. Judeinstein, accepted in J. Sol-Gel
Sc. and Tech., 2002.
[22] J. A. Chaker, K. Dahmouche, C. V. Santilli, S. H. Pulcinelli, V. Briois, A. M. Flank, P. Judeinstein, accepted
in J. Non Cryst. Solids, 2002.
**********
Electrode materials, insertion compounds and nanostructured solids
J. C Jumas, C. Belin, L. Monconduit, J. Rozière, D. Jones, F. Favier
Laboratoire des Agrégats Moléculaires et Matériaux Inorganiques UMR5072
The research carried out at the Laboratoire des Agrégats Moléculaires et Matériaux Inorganiques
(LAMMI) UMR5072 has been linked to the used of synchrotron radiation for the past 20 years, and the
needs of the laboratory for XAS (EXAFS and XANES) is currently particularly strong. For the past 5
years, the laboratory has benefited from approximately 20 beam-days per year.
43
In the broader context of the University Montpellier II, XAS is an essential component of research in
the Chemistry and Physics departments, in particular for the local structural characterisation of
functional solids (A. Vioux), catalyst materials (F. Fajula) and carbon nanotubes (J. L. Sauvajol).
Electrode materials (J. C Jumas, C. Belin, L. Monconduit)
XAS is fruitful for study of structural and compositional changes in intermetallic or oxide
electrodes under electrochemical cycling conditions (in situ or ex situ) in a lithium battery. Moreover,
analysis of the near edge allows to follow the oxidation state changes of atoms constituting the
electrode during the oxidation (lithium deinsertion) or the reduction (lithium insertion) processes. As
opposed to electrochemistry studies that probe macroscopic properties, EXAFS and XANES can
provide insight into the atomic-level structure of the electrode as a function of cell potential. This
allows to better understand reversible lithium intercalation mechanisms and to optimize performances,
in this “hot” lithium battery field.
R. Dedryvère, J. Olivier Fourcade, J.C. Jumas Electrochimica Acta, 46, 1, 2000, 127-135
J. Chouvin, C. Branci, J. Sarradin, J. Olivier-Fourcade, J.C. Jumas, B. Simon, P. Biensan, J. Power Source, 81-82,
1999, 277-281.
L. Monconduit, M. Tillard-Charbonnel, C. Belin, J. Sol. St. Chem., 156(1), 37-43, 2001.
M.L. Doublet, F. Lemoigno, F. Gillot, L. Monconduit, submitted to Chem. Mat.
Brevet CNRS, USA, december 2001,”lithium- transition metal pnictide as negative electrode in lithium ion
battery” L. Monconduit, M.L. Doublet, F. Gillot.
Insertion compounds, materials of controlled architecture (J. Rozière, D. J. Jones)
XAS provides essential characterization of local structural and electronic changes occurring in
spinel-structured and layered transition metal oxides following the chemical extraction or insertion of
lithium or protons. In the field of new solid hybrid organic-inorganic proton electrolytes for
electrochemical applications, EXAFS and XANES are unique in allowing us to follow the growth of
nanoparticulate proton conducting inorganic phosphates at ion-exchange sites of proton exchange
membranes. The frameworks of solids of controlled architecture prepared by supramolecular templating
are frequently amorphous, and local structural methods provide unique information.
Effect of chromium substitution on the local structure and insertion chemistry of spinel lithium manganates:
investigation by X-ray absorption fine structure spectroscopy. B. Ammundsen, D.J. Jones, J. Rozière , F. Villain,
J. Phys. Chem. B (1998) 102 7939
X-ray absorption fine structure as a probe of local structure in lithium manganese oxides. B. Ammundsen, D.J.
Jones, J. Rozière, J. Solid State Chem. (1998) 141 294.
Cobalt substitution in lithium manganate spinels : examination of local structure and lithium extraction by XAFS
P. B. Aitchinson, B. Ammundsen, D.J. Jones, G. Burns, J. Rozière. J. Mater. Chem. (1999) 9, 3125.
Nanostructured solids (F. Favier)
EXAFS and XANES are precious tools for the electronic and structural investigations of
nanostructured materials : with the decrease in size, the loss of long range order limits the use of
conventional X-ray diffraction techniques. In these nano objects, surface reactivity and interfacial
contributions dramatically drive the main characteristics of the material. In the case of a sensor, for
example, EXAFS as well as XANES are among the rare available techniques for an in-situ observation
of the analyze absorption.
Electrochemical synthesis for the control of -Fe2O3 nanoparticle size. Morphology, microstructure and magnetic
behavior, C. Pascal, J.L. Pascal, F. Favier, M.L. Elidrissi Moubtassim and C. Payen, Chem. Mater., 11, 141,
1999.
Hydrogen sensors and switches from electrodeposited palladium mesowire arrays, F. Favier, E. C. Walter, T.
Benter, R.M. Penner, Science 2001 ; 293 : 2227-2231.
Improvements sought : Development or, at least, a status quo of beam-days on
spectrometers/experimental set-ups allowing the straightforward study of new compounds or materials.
Such studies are essential for materials scientists and chemists following the evolution of a structure,
44
local structure, coordination environment, oxidation state, etc. as a function of synthetic parameters
varied prior to the x-ray absorption experiment (i.e. ex situ). Even such routine experiments require
environments such as ovens or cryostats. In other cases, the composition, local structure etc. must be
varied in situ, or may require specific electrical or magnetic equipment.
- In the case of insertion compounds and heteroatom-doped materials, the means necessary for XAS
analysis of elements present in low proportion is identified as essential.
- For compounds in which lithium can be inserted/deinserted electrochemically, it is important to
continue the effort to enable XAS experiments to be performed in an inert atmosphere, and to develop
the environment allowing electrochemical experiments in situ.
- In general for materials chemistry, the need is identified also for the techniques using
microfocalisation of the beam, providing access to the local structural characterization of
microheterogeneous materials.
**********
Nanometric Ferrites
Nadine Guigue-Millot
LRRS (Dijon)
The field of nanoparticles in materials research has sparked intense interest in expectation that
this unexplored range of materials dimensions will yield drastic size-dependent properties. In this
context, the fundamental aim of our work is to explain why materials properties change when their
grain size decreases [1].
First, we have to select a model material making it possible to study the surface influence on the
materials properties. For their scientific and applied interest we have chosen nanometric ferrites with
the spinel structure. Two phenomena studied in our group particularly require a technique sensitive to
short-range order :
- the influence of surface energy on the thermodynamical properties of materials,
- the influence of surface stress on the structural properties of materials.
The first phenomena, has already been studied at LURE. It has been shown that the surface
energy allows to stabilise phases apart from their usual limits. Indeed, in the case of the Fe-Ti-O
system, the spinel phase which is confined in the case of monocrystals with large grain, extends with a
broad area in the case of nanometric grains obtained by soft chemistry : (Fe3-xTix)1-δO4, grain size lower
than 30 nm [2]. However, the surface energy is not sufficient to completely avoid the immiscibility of
the Ti and Fe cations. Indeed, TiO2 clusters of size lower than 4 Å have been detected in the spinel
structure for the richest compositions in titanium [2, 3].
The second phenomena is currently studied on a γ-Fe2O3 powder with grain size equal to 10 nm.
By describing the adsorption isotherm of water on this powder, we change the quantity of water
adsorbed on the surface, therefore the nature of the H2O− γ-Fe2O3 surface interactions is transformed
and consequently the surface energy. Thanks to the complementarily of various techniques : TGA,
XRD and microcalorimetry, we observed a diminution of the lattice parameter of the γ-Fe2O3 sample of
about 0.1% due to OH- chimisorption ; then an increase probably due to the water physical absorption.
For these two studies, only the synchrotron radiation allows flux and resolution sufficient in the
4500 - 8500 eV range in order to explain these structural changes versus grain size or surface coating.
[1] N. Guigue-Millot, N. Keller, P. Perriat, Phys. Rev. B 64 (2001) 012402.
[2] Synthèse et Propriétés de Ferrites Nanométriques : Influence de la taille des grains et de la nature de la
surface sur les propriétés structurales et magnétiques de ferrites de titane synthétisés par chimie douce et
mécanosynthèse. N. Guigue-Millot, Thèse de Doctorat, Chimie-Physique, Dijon (1998).
[3] Problématique des valences mixtes dans les ferrites nanométriques : possibilités offertes par la diffraction
résonnante des rayons X. J. Lorimier, Thèse de Doctorat, Chimie-Physique, Dijon (2001).
45
B. Catalysis
Much research in the coming decades will be dedicated to the characterisation of
nanomaterials, these materials being an elegant key to resolve different environmental and
industrial challenges of our modern society. Let's quote for example the reduction of NOx
emissions into the atmosphere [1-3], the optimisation of the Fischer-Tropsch process in the
conversion of natural gas to clean fuels [4,5] or the hydrogenation of hydrocarbons to produce
valuable petrochemical compounds [6,7], each of these challenges being associated with
catalytic materials made of nanomaterials. More precisely, practical catalysts usually consist
of a porous material containing a mixture of highly dispersed metallic or sulphide "active"
species. The active phase consists of nanometer scale entities, a structural specificity at the
origin of the high reactivity of such materials.
The diversity of the challenges in heterogeneous catalysis has led the community to
participate in four different scientific projects (Exafs-Awaxs, Dispersive Exafs, Xas with soft Xray photons and Xas in the 4-40KeV) with common equipment for in situ characterisation [810]. The ultimate goal is to obtain significant structural and electronic characteristics of
catalysts in order to understand/predict their catalytic activity/selectivity in a given reaction.
Among such nanomaterials, we can quote different challenges in which synchrotron radiation
related techniques have played a key role [11].
One challenge is related to nanomaterials made of quasi-atomically dispersed metals
on or inside well ordered oxides such zeolites. Only a study which combines X-ray absorption
spectroscopy and anomalous wide angle X-ray scattering [12] (i.e. determination of the
electronic state of the deposited metal as well as a detailed description of the mean local
order) allows a precise knowledge of the occupation site which determines the
activity/selectivity. Several works [13] illustrate perfectly the opportunities given by such
combination.
One way to optimise the physico-chemical properties of the catalyst lies in the
determination of intermediate states of the catalyst which can exist for example during the
preparation procedure or the activation step. The study of chemical oscillations constitutes
also a large field of interest [14]. Dispersive Exafs [15]. constitutes an elegant and efficient
way to perform such experiments, the acquisition time being around a few milliseconds [16].
Regarding soft X-ray absorption spectroscopy, we have recently underlined the
opportunities given by such approach [17]. Basically, the chemical reaction can be studied
through the molecule itself (see ref. 18 for experiments collected at the N K edge). Moreover,
for the active metal, we have already shown the great sensitivity of 2p spectroscopy to the
valence state of the metal atoms as well as to the symmetry of the sites [4]. From an
experimental point of view, the high K-edge energy compared to that of the L-edge implies that
detailed features at the edges can best be observed in the case of soft X-ray experiment, since
the shoulder generally measured at the K-edge can be observed in fine details at the L-edge.
Modern materials studies integrate systematically X-ray absorption spectroscopy in the
4-40 KeV range. This technique can be considered an invaluable starting point especially for
multimetallic systems. In this case, several papers show the importance of collecting on the
same sample the X-ray absorption spectrum on both edges. In the case of simple bimetallic
systems such PtSn, not only are the energies of the edges of interest very different (Pt LIII, E=
11560 eV; Sn K, E= 29200 eV) but so are the concentrations. Thus, one measurement can be
performed in transmission while for the other one, the fluorescence mode has to be considered.
The performances of the last generation of synchrotron sources give also the opportunity to
study in situ diluted systems (below 0.1 wt% of active phase or dopant) which are hardly
accessible with other techniques. Note that such experimental configuration is not easy in the
dispersive mode.
46
Also, the importance of recent results obtained using the Qexafs mode [7, 19] underline
the efficiency of this approach. There is clearly a set of major chemical reactions for which the
time scale is in line with the associated acquisition time (around the second).
Finally, major breakthroughs can be done through the possibility to correlate the
structural/electronic description of the catalyst with information coming from a measurement
of its activity/selectivity [20] or the adsorption mode of the molecule (through Fourier
Transform Infrared). At this point, special attention has to be paid to the design of the new
reactor cells in order to be compatible with these complementary techniques.
[1] C. Micheaud, P. Marecot, M. Guerin, J. Barbier, Applied Catalysis A: General 171 (2) (1998) pp. 229-239.
[2] K. Haj, S. Schneider, G. Maire, S. Zyade, M. Ziyad, F. Garin. Topics in Catalysis, 16, 205, 2001.
[3] S. Schneider, D. Bazin, G. Meunier, R. Noirot, M. Capelle, F. Garin, G. Maire. Cat. Let. 71 (2001) 155.
[4] D. Bazin, P. Parent, C. Laffon, O. Ducreux, J. Lynch, I. Kovacs, L. Guczi, F. De Groot. J. of Catalysis, 189
(2), 456, 2000.
[5] L. Guczi, D. Bazin. Applied Catalysis A General 188, 163, 1999.
[6] M. Delage , B. Didillon , Y. Huiban , J. Lynch , D. Uzio. Studies in Surface Science and Catalysis, 130B,
(2000) p. 101.
[7] C. Geantet, Y. Soldo, C. Glasson, N. Matsubayashi, M. Lacroix, O. Proux, O. ulrich, J. Hazmann. Cat. Let.
73,95, 2001.
[8] In situ XAFS measurements of catalysts. D. Bazin, H. Dexpert, J. Lynch. in "X-ray Absorption Fine Structure
for catalysts and surfaces", Ed. Y. Iwasawa, Ed. World Scientific, 1996.
[9] New set-up experiment dedicated to DeNOx catalyst. R. Revel et al., NIM B, 155, 183, 1999.
[10] Développement d'une cellule pour des études EXAFS in situ de pots catalytiques de voiture. S. Schneider et
al., J. de Physique, IV, Pr 10, 449, 2000.
[11] Application of synchrotron radiation to in situ characterization of catalysts, T. Shido, R. Prins, Current
Opinion in Sol. State and Mat. Science, 3, 330 (1998).
Effects of the support on the morphology and electronic properties of supported metal clusters: modern concepts
and progress in 1990s, A. Yu. Stakheev, L. M. Kustov, Applied Catalysis A: General, 188, 3 (1999).
Characterization of heterogeneous catalysts by X-ray absorption spectroscopy, K. Chao, A.C. Wei , J. of
Electron Spec. and Related Phenomena, 119, 175 (2001).
[12] Anomalous Wide Angle X-ray Scattering in heterogeneous catalysis, D. Bazin, L. Guczi, J. Lynch, Applied
Catalysis A 226, 87 (2002).
[13] M. Bellotto, B. Rebours, O. Clause, J. Lynch, D. Bazin, E. Elkaim, J. Phys. Chem. 100, 8527 (1996).
M. Bellotto, B. Rebours, O. Clause, J. Lynch, D. Bazin, E. Elkaim, J. Phys. Chem. 100, 8535 (1996).
[14] F. Schüth, B. E. Henry, L.D. Schmidt, Adv. Catal. 39, 51 (1993).
[15] Real time in situ Xanes approach to characterise electronic state of nanometer scale entities D. Bazin, L.
Guczi, J. Lynch, Rec. Res. Dev. Phys. Chem. 4, 259 (2000).
[16] D. Bazin, H. Dexpert, J. P. Bournonville, J. Lynch, J. Cat. 123, 86 (1990).
T. Ressler, M. Hagelstein, U. Hatje, W. Metz, J. Phys. Chem. B 101, 6680 (1997).
D. Bazin, L. Guczi, J. Lynch, Rec. Res. Dev. Phys. Chem. 4, 259 (2000).
A. Yamaguchi, A. Suzuki, T. Shido, Y. Inada, K. Asakura, M. Nomura, Y. Iwasawa
J. Phys. Chem. B 106, 2415 (2002).
J. Evans and M. A. Newton, J. Mol. Cat. A Chemical, In Press
[17] Soft X-ray absorption spectroscopy in heterogeneous catalysis D. Bazin, L. Guczi, Applied Catalysis
General A 213, 147 (2001).
[18] R. Revel, P. Parent, C. Laffon, D. Bazin, Cat. Let. 74, 189 (2001).
[19] R. Cattaneo, T. Shido, R. Prins, J. of Syn. Rad. 8, 158 (2001).
D. Lützenkirchen-Hecht, R. Frahm, J. Phys. Chem. B 105, 9988 (2001).
V. Schwartz, M. Sun, R. Prins, J. of Phys. Chem. B 106, 2597 (2002).
[20] N. S. Guyot-Sionnest, F. Villain, D. Bazin, H. Dexpert, J. Lynch, F. Lepeltier. Catalysis letters 8, 283 (1991)
& Catalysis letters 8, 297 (1991).
**********
47
Characterisation of catalytic systems by EXAFS
E. Payen,
Laboratoire de Catalyse (LILLE)
The Laboratoire de Catalyse de Lille has a long experience in the field of synthesis and
characterisation of catalytic materials. Its research themes tackle different fields, e.g. environment
(DeNOx catalysis), light alkanes valorization (oxydehydrogenation ..) and energy (hydrotreatment,
Fischer-Tropsch). Whatever the considered theme, the goal is to seek and to set up new catalytic
formulations. It therefore consists in synthesis of new materials, bulk and/or supported, that have to be
precisely characterised. However, these materials, that must have good textural properties (high specific
area, porosity …), are most often amorphous. On the other hand, in the case of supported phases, one
comes up against the sensibility limits of the usual techniques (X-ray Diffraction, vibrational
spectroscopies …). This is why the laboratory turned to the EXAFS technique in order to characterise
local order. In most cases, it is therefore all a question of characterising divided solids by EXAFS in an
energy range (10-20 keV) corresponding to the K-edge of 3d and 4d elements or to the L-edge of 5d
transition elements.
Several categories of solids are currently studied in the laboratory, e. g. :
transition metals and/or lanthanide based bulk oxides, spinel and perovskite-typed, for the DeNOx
treatments.
tungsten- or molybdenum-based heteropolyoxoanions, bulk or supported on different supports
(silica, alumina…) for oxydehydrogenation of light alkanes, hydrotreatment or isomerisationalkylation of petroleum feedstocks.
tungsten- or molybdenum-based iso and heteropolythioanions, bulk or supported on different
supports (silica, alumina…) for hydrotreatment of petroleum fractions.
supported metals (Pd, Rh) for elimination of volatile organic compounds.
Co-based catalysts supported on silica or mesoporous silica.
Whatever the considered field, we characterise, by means of EXAFS, the catalyst in two steps of
its implementation, e. g. its preparation and its activation, as well as the catalyst in the conditions
of reaction.
Catalysts preparation
A precise control of the synthesis routes of the catalysts goes along with improvement of
activities and selectivities. Recent studies by EXAFS at the Mo K-edge enabled us to determine the
exact nature of the alumina- or zeolite-supported oxomolybdate phases. These studies enabled a
description of the genesis of supported oxidic phases. However, the catalytic formulations are more
complex and generally involve several metals, the environments of which it is necessary to know
accurately, in order to infer the origin of the synergy effects generally described in the literature. Works
under progress in the laboratory within the context of a Ph.D. concern the development of this new
concept of dissolution-precipitation to multi-component solids (CoMo-W, NiMo-W…). On the other
hand, we plan to widen this study to the case of other supports (titanium or zirconium oxide). These
works will require EXAFS experiments at the edge of these transition elements.
Activation of the catalysts
These catalytic solids are usually prepared in the oxidic state and then go through an activation
in order to generate the active phase. Therefore, the genesis of this active phase must be perfectly
controlled, since it conditions the activity and the selectivity of the catalysts. Consequently, it is
important to be able to monitor the evolution of the solids during the activation period, in order to
optimise this step and to have an accurate knowledge of the structure of the active phase. This
activation takes place under different atmospheres (sulfiding for hydrotreatment, reducing for FischerTropsch, oxidising for mild oxidation, …). These studies must therefore be achieved under controlled
atmosphere and require temperature (up to 800°C) and pressure specific cells that enable a
characterisation of the catalyst under various atmospheres, including corrosive ones.
Study of the reactivity
Since two years, one of the laboratory’s orientations is in situ study of catalysts in working
conditions. It is indeed important to know the exact nature of the active phase in the working
48
conditions, e.g. the local environment of the active sites. Thus, we were recently able to characterise by
EXAFS the active sites of the hydrotreatment catalysts, whose active phases consist in Mo disulfide
nanocrystallites dispersed at the surface of a high specific area alumina. These structural studies by
EXAFS are complementary with studies carried out with other techniques that allow a characterisation
of adsorbats (FTIR, Raman, XPS). We also plan to characterise these adsorbats by XANES in the range
of low energies (for instance at the N K-edge to characterise the adsorption of NO or N2O).
This way, it will be possible to characterise the catalyst in various stationary conditions. A
coupling of these cells to an on-line analysis system (GC-MS) will allow the measurement of
conversion rates and selectivities under various catalytic modes. One will therefore be able to infer
directly structure-reactivity correlations, that will allow the identification of the reaction
“intermediates” (limiting step) and of the active site.
The research programme of the Laboratoire de Catalyse de Lille therefore focuses on the in situ
study of catalytic systems in working conditions and requires the implementation of catalytic cells
directly adaptable to the EXAFS analysis beamline, eventually combined with RAMAN spectrometry.
A. Y. Khodakov, A. Griboval-Constant, R. Bechara and F. Villain. Pore size control of cobalt dispersion and
reducibility in mesoporous silicas. J. Phys.Chem.B, 2001, v. 105(40), p. 9805-9811.
B. Olthof, A. Khodakov, A.T. Bell, and E. Iglesia. Effects of support and pretreatment conditions on the structure
of vanadia dispersed on SiO2, Al2O3, TiO2, ZrO2, and HfO2. J.Phys. Chem. B, 2000, 104, p.1516-1528.
A. Khodakov, O. Ducreux, J. Lynch, B. Rebours and P. Chaumette. Structural modification of cobalt catalysts:
effect of wetting studied by X-Ray and infrared techniques".Oil & Gas Science and Technology, 1999, V.54, n.4,
pp. 525-536.
A. Khodakov, J. Lynch, D. Bazin, B. Rebours, N. Zanier, B. Moisson and P. Chaumette. Reducibility of cobalt
species in silica supported Fischer-Tropsch catalysts. J Catalysis, 1997, v. 168, p.16-25.
G. Plazenet, S. Cristol, E. Payen, J. Lynch, J. F. Paul. In-situ EXAFS Study of the Sulphur Coverage of Alumina-Supported MoS2. Crystallites PCCP, 2001, 3, 246.
G. Plazenet, E. Payen, B. Rebours, J. Lynch. A Study by EXAFS, Raman Spectroscopy and NMR spectroscopies
of the Genesis of the Oxidic Precursors of Alumina- and Zeolite-Supported HDS Catalysts. J. Phys. Chem.
Submitted.
G. Plazenet, E. Payen , J. Lynch. Cobalt-molybdenum interaction inoxidic precursor s of Co promoted Zeolithe
supported HDS catalysts. PCCP , Submitted.
**********
Metal-supported catalysts
P. Massiani
LRS (Paris 6)
Metal supported oxides (in particular metal/zeolites) are involved in numerous industrial
processes of heterogeneous catalysis (refining, petrochemistry ...). Even though this field has been
widely studied, many questions remain and the needs for new materials with original and tuned
catalytic properties still represent a challenge for the future (for fine chemistry and environmental
applications, for instance). Our laboratory is strongly involved in the preparation of supported catalysts,
with the aim :
- to identify precisely, at the molecular level, the interactions that take place between the supported
metal species and their environment (metal-metal and metal-support interactions). An important aspect
is to characterize the catalysts not only in their activated state (final catalyst) but also all along their
preparation (introduction of the metal precursor, modification of the support, thermal calcination and
reduction treatments). Indeed, the "history" of the materials, and therefore the understanding of their
characteristics at the intermediate steps, are important parameters that determine the characteristics of
the activated solid. For instance, our recent data on Pd-supported and Pt-supported zeolite have shown
that the acido-basic character and the structure of the zeolitic support strongly influence the nature of
the metal species formed at the calcination step [1-2] with important consequences on the dispersion
and activity of the metal after reduction [3-6].
- to control the formation and the location in porous supports (zeolites, new mesoporous
nanostructured oxides) of highly dispersed metallic nanoparticles with well controlled characteristics
49
(nanotechnology approach). Not only the size but also the location and the chemical composition of the
active phase have to be controlled. In the particular case of bi-metallic supported catalysts, the
identification of the metal-metal interactions and of the segregation phenomena is required.
A good understanding of the history and of the properties of the catalysts requires that numerous and
complementary characterization methods be used. Thus, it allows to fully characterize the active site
(metal and environment) at the atomic scale. In some cases, the XAS approch is the only one that can
be used, for instance when segregation phenomena or metal nanoparticles with sizes below the limit of
detection of electronic microscopy ( < 7Å) need to be identified [7-9].
[1] A. Sauvage, M. Oberson de Souza, M. J. Peltre, P. Massiani, D. Barthomeuf. J. Chem. Soc., Chem. Commun.
(1996) 1325.
[2] A. Sauvage, M. Oberson de Souza, P. Massiani, D. Barthomeuf, "Catalysis on solid acids and bases", DGMK
Tagungsbericht Conference, Berlin, Allemagne, 295 (1996).
[3] T. Bécue, F.J. Maldonado-Hodar, A.P. Antunes, J.M. Silva, M.F. Ribeiro, P. Massiani, M. Kermarec, J. Catal.
181, 244 (1999).
[4] F. J. Maldonado, T. Bécue, J. M. Silva, M. F. Ribeiro, P. Massiani and M. Kermarec, J. Catal. 195(2), 342
(2000).
[5] Meriaudeau, P., and Naccache, C., Catal. Rev. Sci. Eng. 39, 5 (1997).
[6] Barthomeuf, D., Catal. Rev. 38, 521(1996).
[7] M. Vaarkamp, J.V. Grondelle, J.T. Miller, D.J. Sajkowski, F.S. Modica, G.S. Lane, B.C. Gates, D.C.
Koningsberger, Catal. Lett. 6, 369 (1990).
[8] C. Dossi, R. Psaro, A. Bartsch, A. Fusi, L. Sordelli, R. Ugo, M. Bellatreccia, R. Zanoni, G. Vlaic,. J. Catal.
145, 377 (1994).
[9] G. Jacobs, F. Ghadiali, A. Pisanu, A. Borgna, W. E. Alvarez, D. Resasco, Appl. Catal. A: General, 188, 79
(1999).
**********
Synthesis of catalysts
LACCO (Poitiers)
Already used in LACCO, synchrotron radiation is an essential tool for physico-chemical
characterization of solid catalysts, which is one of the main objectives of research of this group. Indeed,
to improve the performances of catalytic processes, LACCO develops new techniques of preparations
(or modifications) of catalysts. Such an effort is necessarily accompanied by an important expansion of
the number of structural characterizations for these new solid catalysts.
SOLEIL should enable to meet the demand in some cases on condition that it offers
satisfactorily at least the same possibilities of experiments as LURE did. So, it concerns mainly
obtaining on catalytic materials essential structural characterizations from in-situ experiments, for
example, performed in specific conditions (temperature, pressure and gas flow) corresponding to the
activation of catalysts or to the catalytic reaction. Some of works done in our Laboratory related to XAS
studies have been already published [1, 2, 3].
As SOLEIL, this modern source of synchrotron radiation, will be available very soon, it is
expected a noticeable improvement in performances of the related classical techniques which are
already used in our Laboratory. Moreover, with such a tool, development of other “new” techniques
(small angle scattering, anomalous scattering … EXAFS detection in fluorescence mode, …) is fully
conceivable. The different works to be carried out will consider especially bimetallic catalysts with low
(or very low) loading of active species, selective deposits on surface or catalysts prepared for electrocatalysis and it will correspond in fact to a broadening of fields of investigations led in all the teams of
LACCO.
According to their applications and on the basis of the different projects of experiments
proposed at LURE during the last years, the catalytic systems studied in LACCO concern often metals
(mainly those of the 5th raw as Rh, Pd, Sn) whose the edges are located at high energies > 20 keV.
[1] C. Micheaud, M. Guérin, P. Marécot, C. Géron, J. Barbier, J. Chim. Phys., 1996, 93, 1394-1411.
50
[2] A. El Abed, S. El Qebbaj, M. Guérin, C. Kappenstein, H. Dexpert, F. Villain, J. Chim. Phys., 1997, 94, 54-76.
[3] L. Pirault-Roy, M. Guérin, F. Maire, P. Marécot, J. Barbier, Appl. Catal., A, 2000, 199, 109-122.
Laboratories support :
D. Bazin,
LURE - UMR 0130
X. Carrier, G. Constentin, C. Louis, P. Massiani, C. Thomas, M. Breysse
Laboratoire de réactivité de surface, UMR 7609
F. Studer,
CRISMAT, UMR 6508
J. P. Gilson, F. Mauge, J. Leglise,
LCS, UMR 6506
C. Especel, L. Pirault-Roy, M. Guerin,
LACCO, UMR 6503
F. Garin,
ECPM-LERCSI-UMR7515
A. Khodakov, A. Griboval, C. Lamonier, E. Payen,
Laboratoire de Catalyse de Lille, UPRESA 8010.
A. de Mallmann , J. P. Candy
L.C.O.M.S. - CPE-Lyon,
C. Geantet, L. Bonneviot, J.M. Millet,
Institut de Recherche sur la catalyse, UPR 5401
J. Lynch, B. Rebours, C. Pichon,
Institut Français du Pétrole, 1 et 4 Avenue de Bois Préau, 92506 Rueil Malmaison,
L. Guczi
Department of Surface Chemistry and Catalysis, Institute of Isotope and Surface Chemistry
Chemical Research Center, Hungarian Academy of Sciences,
G. Vlaic
Dipartimento di Scienze Chimiche , Universita' di Trieste
P. Grange
"Faculty of Bio-Engineering, Agronomy and Environment", Unite de catalyse et chimie des materiaux divises
Universite catholique de Louvain
C. Three-dimension systems
In this section, we present contributions concerning different compound (glasses, intermetallic
or molecular systems) whose properties are not related to size or dimension effects but rather
to the chemical composition and (or) crystallographic structure.
I- Molecular Materials
Photomagnetic Prussian blue analogues
LCIMM (Paris 6)
The synthesis of new photomagnetic molecular materials is one of the most important research
field of our group [J. Am. Chem. Soc. 2000, 122, 6648-6652]. XAS have been used to characterise the
structure (EXAFS) and the electronic structure (XANES) of the materials, and their evolutions induced
by the irradiation with red light. The information given by this spectroscopy allowed us to progress
significantly in the understanding of the origin of the photomagnetic effect.
Starting from aqueous Co(II) and hexacyanoferrate(III), we obtain a powder that exhibits spectacular
photoinduced magnetisation at low temperature. The proposed explanation of the phenomenon was the
presence of diamagnetic low-spin Co(III)-Fe(II) pairs in the compound and a photoinduced electron
51
transfer from Fe(II) to Co(III) through the cyanide bridge to produce Co(II )[S=3/2]-Fe(III)[S=1/2]
magnetic pairs. We recorded the Co and Fe L2,3 edges for the Rb1.8Co4[Fe(CN)6]3.3 compound, before
and after irradiation. Our results evidence the electronic transfer and the spin change of the cobalt ions
induced by irradiation [J. Am. Chem. Soc. 2000, 122, 6653-6658]. This is the first experimental local
and direct evidence on the two metallic sites of a photoinduced metal-to-metal electron transfer in a
three-dimensional compound. We correlate the number of diamagnetic pairs to the intensity of the
photoinduced magnetisation effect. We demonstrate also, using XAS, that the presence of diamagnetic
pairs is a necessary but not a sufficient condition to observe the phenomenon [J. Am. Chem. Soc. 2000,
122, 6648-6652].
Recording EXAFS spectra at the Co K-edge, before and after irradiation, we showed that the
photoinduced electron transfer is accompanied with a bond lengthening in the first coordination shell of
the cobalt atoms. So, the inorganic network must be flexible enough to absorb the dilatation of the
bonds. The [Fe(CN)6] vacancies should act as relaxation points of the network strains provoked by
irradiation so that their presence in the structure should also be a necessary condition to observe the
photoinduced magnetization. The efficiency of the photoinduced electron transfer should then depend
on a compromise between the amount of diamagnetic pairs and [Fe(CN)6] vacancies. We are now able
to chemically control this compromise, to optimise the photomagnetisation effect [J. Am. Chem. Soc.
2001, 123, 12536-12543].
The direct determination of the coupling between Co(II) and Fe(III) paramagnetic ions in the
photoinduced metastable state is, in this case, not trivial. The relaxation of the photoinduced magnetic
phase to the diamagnetic ground state occurs at a temperature low enough (T = 105 K) to impede the
observation of the minimum of the χMT vs T curve, expected in the case of ferrimagnetism. We have
used X-ray Magnetic Circular Dichroism (XMCD) measurements to characterise the relative orientation
of the local magnetic moments of the metallic ions in the photoinduced metastable state of the Prussian
blue analogue Rb1.8Co4[Fe(CN)6]3.3. In that way, we propose the first direct experimental evidence of
the ferrimagnetic nature of the photoinduced metastable state in this material [J. Am. Chem. Soc. 2001,
123, 12544-12546].
This work illustrates the importance of X-ray absorption spectroscopy in this research field, combining
hard, soft X-ray and XMCD experiments, to progress in the understanding of macroscopic properties of
materials.
II. Intermetallics and Alloys
Influence of H-absorption on the properties
of rare earth and transition metal alloys
LCMTR (Thiais)
Several groups of the laboratory have worked for many years on the properties of rare earth
and transition metal alloys. Among these compounds some can absorb large amount of hydrogen, which
modify the structural, magnetic and electronic properties of these compounds. In addition hydrogen
storage leads to many applications such as hydrogen isotope storage, batteries, fuel cell, catalysis. Other
compounds when alloyed with an element of the groups III to VA can show interesting physical
properties : heavy fermion, magnetic superconductors etc ... Some of these compounds can be used as
thermoelectric materials.
We have been using the XAS for more than 20 years to characterise these compounds. The
magnetic and electric properties of the rare earth and transition metal alloys are very sensitive to the
electronic configuration, specially for intermediate valence elements such as Ce, Sm, Eu, Yb. The
measurement of the rare earth L3 edge allows to determine the valence, and to correlate it with other
structural, transport and magnetic properties. For example the influence of hydrogen absorption on the
valence state of Ce have been studied in-situ versus H content for compounds used in Ni-MH batteries.
The study of the local order by EXAFS experiments was also very useful to understand the evolution of
the structural properties of the compounds as a function or hydrogen content, for example in the case of
YFe2Dx deuterides. In many cases (Yb-and Eu-based systems), the local character of XAS as a probe
leads us to review the average view given by XRD. For instance we recently probe that in skutterudites
52
EuxM4Sb12 (M = Fe, Co, Ni), even though there is only one crystallographic site for Eu, XAS shows a
mixed valence state (in agreement with Mössbauer experiments) induced by the vacancies on the Eu
site.
To continue these studies, we need to perform XANES and EXAFS measurements at the
transition metal (3d, 4d and 5d) K edge and rare earth L3 edge. These edges are located in the 3-25 keV
energy range. This presents the advantage of studying compounds by transmission and to perform
volumetric measurements. For this we need a linear polarization and a very good resolution to measure
the XAS. The samples should also be measured either at low temperature (He cryostat) or at elevated
temperatures and an oven will also be necessary to characterize their transitions. We are also planning
to perform kinetic measurements (hydrogen absorption, electrochemistry and catalysis) and fast patterns
measurements will be useful.
S. Thiebaut, V. Paul-Boncour, A. Percheron-Guegan, B. Limacher, O. Blaschko, C. Maier, C. Tailland, D. Leroy.
Structural changes in Pd(Rh,Pt) solid solutions due to 3He formation during tritium storage. Phys. Rev. B, 57,
10379, (1998).
V. Paul-Boncour, A. Percheron-Guegan. The influence of hydrogen on the magnetic properties and electronic
structures of intermetallic compounds: YFe2H2 as an example. J. Alloys Comp., 293-295, 237-242, (1999).
V. Paul-Boncour, M. Gupta, J.-M. Joubert, A. Percheron-Guegan, P. Parent, C. Laffon. Investigation of the
electronic properties of substituted LaNi5 compounds used as material for batteries. J. Materials. Chemistry., 10,
2741-2747, (2000).
V. Paul-Boncour, J.M. Joubert, M. Latroche A. Percheron-Guegan, In situ XAS study of the hydrogenation of AB5
compounds, (A =La, Ce and B=Ni3.55Mn0.4Al0.3Co0.75), J. Alloys Comp., 330-332, 246-249 (C), (2001).
I. Moysan, V. Paul-Boncour, S. Thiébaut, E. Sciora, D. Courteix, J.M. Fournier, S. Bourgeois, A. PercheronGuegan, R. Cortes. Pd-Pt alloys : Correlation between electronic structure and hydrogenation properties. J.
Alloys Comp., 322, 14-20, (2001).
P. Bonville, J. A. Hodges,, Z. Hossein, R. Nagarajan, S. K. Dhar, L. C. Gupta, E. Alleno, and C. Godart. Heavy
electron YbNi2B2C and giant exchange YbNiBC: 170 Yb Mossbauer spectroscopy and magnetization studies
European Physical Journal B 11, 377 (1999).
M. Rams, K. Kroplas, P. Bonville, J. A. Hodges, Z. Hossain, R. Nagarajan, S. K. Dhar, L. C. Gupta, E. Alleno,
and C. Godart. Crystal electric field in YbNi2B2C and YbNiBC observed by 172Yb perturbated angular
correlations. Journal of Magnetism and Magnetic Materials 15, 21 (2000).
S. K. Dhar, C. Mitra, P. Bonville, M. Rams, K. Krolas, C. Godart, E. Alleno, N. Suzuki, K. Miyake, N. Watanabe,
Y. Onuki, P. Manfrinetti, and A. Palenzona. Magnetic and 4f quadrupolar behaviour of Yb2Co3Al9 and the Kondo
lattice Yb2Co3Ga9 .Physical Review B 64, 094423 (2001).
C. Mazumdar, E. Alleno, O. Sologub, P. Salamakha, H. Noel, M. Potel, A. D. Chinchure, R. Nagarajan, L. C.
Gupta, and C. Godart. Magnetic and valence properties of a new Ce-based quaternary borocarbide CeIr2B2C
Journal of Magnetism and Magnetic Materials 226 & 230, 307 (2001).
Y. Mudrik, A. Grytsiv, P. Rogl, A. Galatanu, E. Idl, H. Michor, E. Bauer, C. Godart, D. Kaczorowski, L.
Romaka, and O. Nodak. Physical properties and superconductivity of skutterudite related Yb3Co4.3Sn12.7 and
Yb3Co4Ge13. Journal of Physics : Condensed Matter 13, 7391 (2001).
***********
Evolution of the local structure with hydrogenation
in quasicrystals and approximants
1
A. Sadoc1, K. F. Kelton2
LPMS (Cergy-Pontoise) et LURE (Orsay), 2Department of Physics (Washington)
An understanding of the mechanism of hydrogen absorption in metals and intermetallics is of
considerable importance for both technological and scientific reasons. Metal-hydrogen systems are used
in a variety of technological applications, including hydrogen storage materials and metal-hydride
batteries.
Since the discovery of intermetallic alloys with both long-range aperiodic order and crystallographically
forbidden rotational symmetries by Shechtman, Blech, Gratias and Cahn (1984), a large body of
theoretical and experimental work has been devoted to the study of these materials, known as
quasicrystals (QC's). Among their physical properties, it has been found that some titanium/zirconiumbased QCs have a larger capacity for reversible hydrogen storage than competing crystalline materials
(Kelton and Gibbons, 1997).
53
The key parameters determining which materials can store hydrogen include the chemical interactions
between the metal and hydrogen atoms and the number, type, and size of interstitial sites in the host
material. In most transition metal alloys, hydrogen atoms prefer to sit in tetrahedrally coordinated sites.
Quasicrystalline alloys or crystalline approximant phases are expected to contain a high number of
short-range ordered tetrahedral structural units, which are favourable to occupation by hydrogen. This
encourages X-ray absorption investigations for these alloys.
Upon hydrogenation, X-ray diffraction only showed a monotonous increase of the lattice parameter, the
crystalline or quasicrystalline phase being retained up to the highest H/M ratios. Although EXAFS, as
X-ray diffraction, is not directly sensitive to the presence of hydrogen, it allows the study of the average
change in local order induced by hydrogen. Therefore, we have undertaken an EXAFS study of the
evolution of the short range ordering as a function of the hydrogen content in titanium-based alloys,
crystal or quasicrystal, to complement the information on the averaged, long-ranged ordering available
from diffraction measurements, thereby advancing understanding of the hydrogenation.
Sadoc A., J.Y. Kim and K.F. Kelton, Proceedings of the 1998 Materials research Society Fall Meeting, ed. : J. M.
Dubois, P.A. Thiel, A.-P.- Tsai and K. Urban, vol. 553, p. 141 (1999).
Sadoc A., Kim J.Y. and Kelton K.F., Phil. Mag. A, 79, 2763 (1999).
Sadoc A., J.Y. Kim and K.F. Kelton, Materials Science and Engineering A 294-29, p.348 (2000).
Sadoc A., Kim J.Y. and Kelton K.F., Phil. Mag. A, 81, 2911 (2001).
III- Glasses
Tellurite Glasses
LPMC (Montpellier)
The synthesis of glasses with high refractive index values is of great importance in the glass
science and the optical industries. Oxide tellurite glasses have been obtained showing an extremely high
refractive index, low crystallization ability and good chemical resistance. Also, they exhibit good light
transmission in the visible and near infrared regions (up to 5.5 µm). Further, TeO2-based glasses are
considered to be optically nonlinear materials. The high nonlinear refractive index of Te4+-containing
glasses is attributed to the nonbonding l one electron pair, 5s2, of tellurium. For these reasons, tellurite
glasses have become the subject of thorough investigations. Systematic changes in the proportion and
type of network modifier ions are used to increase or decrease refractive index values and optical nonlinearities.
It has been pointed out that the introduction of heavy transition element oxide with an empty d
shell as Ti4+, W6+, increases the optical properties (index of refraction). The same effect is attributed to
heavy elements having a l one electron pair as Sb +III, Nb +IV, Tl +I. In order to find a relationship
between structure and physical properties, structural characterizations of tellurite glasses with these
heavy elements is necessary. Reliable qualitative and quantitative structural information concerning the
short range order can be obtained by XAS.
Tellurite glasses are a good illustration of the necessity of a synchrotron facility with a hard Xray absorption beam. (Te K edge (31814 eV), Nb K edge (18985 eV), W LI edge (12100 eV)). Very
recently, we have performed W LI edge EXAFS and XANES studies on TeO2-WO3 glasses. This was
the first time that such experiments were performed on these binary glasses. These XAS experiments
was really necessary since the environment of the W atoms was still subject to discussion despite many
works using vibrational spectroscopies. Our X-ray absorption data analyses have pointed out the
existence of distorted WO6 octahedra whatever the glass composition.
This is why we are very concerned with the realization of a hard x-ray absorption beam at SOLEIL.
Mössbauer and XANES of TeO2-BaO-TiO2 glasses.
J-C. Sabadel, P. Armand, P-E. Lippens D. Cachau-Herreillat, E. Philippot .J. Non-Crystalline Solids, 244 (1999) 143-150.
X-ray absorption investigation of TeO2-BaO-TiO2 glasses. J-C. Sabadel, P. Armand, A. Ibanez, E. Phillipot, Phys. Chem.
Glasses, 41 (1) (2000) 17-23.
54
TeO2-based glasses : a structural investigation P. Charton, P. Armand, E . Phillipot, ICG XIX, Edinburgh 1-6 July, 2001,
Phys. Chem. Glasses, submitted sept 2001.
Glasses in the TeO2-Sb2O4 binary system P. Charton, P. Armand, J. Non-Cryst. Solids, submitted 15 janvier
XANES and Raman characterization of TeO2-Ga2O3 glasses P. CHARTON, P. ARMAND J. Physics : Cond. Matter,
submitted 29 janvier.
New tellurite glasses : TeO2-WO3-Sb2O4 and TeO2-WO3-Ga2O3 P. Charton, P. Armand, Phys. Chem. Glasses, submitted 31
janvier.
TeO2-WO3 glasses : infrared, XPS and XANES structural characterizations P. Charton, L. Gengembre, P. Armand J. Solid
State Chem., in preparation
***********
Structure of glasses and liquids
L. Cormier1, D. Neuville2, Y. Linard2, L. Galoisy1, G. Calas1, P. Richet2
1
LPC (Paris 6 et 7), 2IPGP (Paris)
A detailed knowledge of the atomic structure of any material is an important pre-requisite for
understanding both its properties and function. In the last two decades the XAS technique has found
increasing use in the analysis of glass structure [Brown et al., 1995]. In particular, XAS experiments
showed the non homogenous distribution of cations in the glassy state at the microstructural level,
which completely change the vision of glass structure [Greaves, 1989], yet our understanding of
disorder is still inadequate.
Our group is widely using XAS in order to better understand the structure of oxide glasses, with
a wide area of fundamental questions and technological applications. In particular, the understanding of
the glass structure would allow to validate relationships between the structure and physical properties
such as ionic conduction or thermodynamic properties. The studied glasses are also of interest for a
Earth Science point of view, since the structure of glasses is considered to be analogous to that of
magmatic liquids. The question of the location of ions in the glass networks and whether they act as
network modifiers or formers is also important in order to understand their properties [Galoisy et al.,
2000, Cormier et al., 2001].
High quality structural information are also required at elevated temperature to enlighten the
liquid to glass transition processes, the structural modifications with temperature and the crystal
nucleation in glasses [Linard et al., 2002], which play a fundamental role in the development of
advanced glass-ceramics. In particular, the structural role of the nucleating agents (Ti, Fe, Zr) is little
understood and would benefit from XAS studies. The success of such studies will depend on the
availability of suitable sample environment equipment such as the DSC set up in development on the
D44 station at LURE. These combined techniques are particularly important to link structural and
thermodynamic information.
A XAS instrument required a wide range of available energies in order to probe important glass
network former (Ge) to obtain information on the polymerised network. Alkalis and alkaline-earths (K,
Ca, Cs) and transition elements (Ni, Fe) are also of particular interest as these elements strongly affects
the glass properties. A hard X-rays absorption instrument will offer major advances for the community
of complex and disordered materials.
Brown G. E. Jr., Farges F., Calas, G. (1995). X-ray scattering spectroscopic studies of silicate melts. Structure
dynamics and properties of silicate melts. J. F. Stebbins, McMillan, P.F., Dingwell, D.B. Washington,
Mineralogical Society of America. 32 : 317-410.
Cabaret D., Le Grand M., Ramos A., Flank, A.-M., Rossano S., Galoisy L., Calas G., Ghaleb D. (2001). “Medium
range structure of borosilicate glasses from Si K-edge XANES: a combined approach based on multiple
scattering and molecular dynamics calculations.” J. Non-Cryst. Solids 289 : 1-8.
Cormier L., Galoisy L., Calas G. (1999). “Evidence of Ni-containing ordered domains in low alkali borate
glasses.” Europhys. Lett. 45 : 572-578.
Cormier L., Neuville D. R., Briois V. (2002). “The Ca environment in aluminosilicate glasses by X-ray
absorption spectrosocopy” in preparation.
Galoisy L., Cormier L., Rossano S., Ramos A., Calas G., Gaskell P.H., Le Grand M. (2000). “Cationic ordering
in oxide glasses: the example of transition elements.” Miner. Mag. 64: 409-424.
55
Greaves G. N. (1989). “EXAFS, glass structure and diffusion.” Phil. Mag. B 60: 793-800.
Linard Y., Neuvile D.R. , and P. Richet (2002) Rheology of andesite melts: the influence of iron content.
J.Geophys Res. (submitted).
***********
BIMEVOX , Transition metal mixte oxides and associated glasses
S. Daviero Minaud, L. Montagne, O. Mentre, F. Abraham, G.Mairesse and G. Palavit
LCPS (Lille)
The LCPS is mainly concern by the characterization of bismuth-based oxide ion conductors, mixed
valence transition metals and phosphate based glasses.
BIMEVOX and related bismuth-based oxide compounds.
Bismuth-based oxide ion conductors are well known to display excellent properties at moderate
temperature as low as 300-600°C. Among these bismuth-based conductors, the BIMEVOX group of
materials exhibit the highest conductivities. They derive from the parent compound Bi4V2O11 by partial
substitution for vanadium with a metal. A wide range of element is able to substitute for vanadium and
leads to the stabilisation of the high temperature γ-Bi4V2O11 form at room temperature. These
compounds are good candidates as membrane for Ceramic Oxygen Generators. In a classical device, to
allow the oxygen transfer into the membrane, electrode materials have to be added at the surface.
However a catalytic activity towards the oxygen transfer was usually observed for bismuth-based
materials.
By combining both electrochemical characterisation and in situ X-ray diffraction, performed on BM16
at ESRF, it was shown that under finite current density, these materials, when used as electrolyte for the
electrochemical oxygen separation from air, locally transform and become good electrodes for the
oxygen reduction reaction. This transformation was explained by a local and reversible reduction of
vanadium and metal at the surface of the membrane [1].
Partially reduced BIMEVOX were obtained by soft reduction with lithium and characterised on EXAFS
4 of D44 DCI’s beam line. The edge LIII of bismuth and K edge of vanadium and metal dopant was
examined. An evolution of the metal oxidation state was clearly evidenced in the case of the BICUVOX
materials. Further experiments, under operating conditions, would confirm the mechanism of
transformation during the oxygen separation.
If the oxygen transfer in BIMEVOX materials seems to be clarify, questions are remaining for other
bismuth-based system, the actual role of bismuth in the transfer is not understood and further XANES
experiments are planed to help for the understanding of these unusual materials.
Transition metals mixed oxides
The synthesis and characterization of new mixed valence transition oxide is one other important LCPS
thematic, notably for their electronic and magnetic properties. Different series are studied such as
hexagonal perovskite, low dimensional compounds, double Bi/M oxyphosphate... In theses compounds
the mean oxidation number of the metal is often non-integral, bringing up the problem of the charges
distribution related to some original physical properties [2]. At that point XANES spectroscopy is a
powerful tool to distinguish between mixed or double valence state, i.e. electronic delocalization or not,
completing the other characterization techniques.
Furthermore some of these oxides are synthesized by hydrothermal method [2, 3] where the
precursors reactions and the synthesis mecanism are unknown. For instance a proposal is accepted this
year for EXAFS and XANES study of the metal-precursors environment evolution in solution. More
completed studies are being envisaged to follow the metal environment evolution during the synthesis
under pressure.
Associated Glasses
Glasses of Na2O-P2O5- metal-oxide systems or Na2O-P2O5-Bi2O3- metal-oxide system are studies at the
laboratory. Besides their interest as scellement glasses, these compounds present also interesting Na+
ions conduction properties. They present particular Tg evolution related to their composition. A part of
their structural study is realized by 31P and 23Na MAS-MNR [4]. However it has to be completed by
determination of the Bi and metal environment by XANES and EXAFS spectroscopy. This allows to
related the evolution of the element environment with the glasses compositions and the physical
behavior.
56
[1] C.Pirovano Membranes céramiques BiMEVOX pour la séparation électrochimique de l’oxygène Thèse de Doctorat, 2000.
[2] N.Henry, O.Mentre, J.C.Boivin and F. Abraham Chem. Mater., vol. 13, No. 2, 2001, 543-551.
[3] P. A. Ndiaye, B. Loiseau, S. Minaud, P. Pernod, J. C. Tricot Microsystem Technologies, vol. 6, 1999, 15-18.
[4] EXAFS, XANES and
submitted.
31
P double quantum MAS NMR of (50-x/2)Na2O-x Bi2O3 (50-x/2)P2O5 glasses
IV- Others
Combined x-ray absorption spectroscopy and x-ray diffraction under extreme conditions
of pressure and temperature in a large volume cell
Physique des Milieux Condensés (Paris 6)
The purpose here is to combine x-ray absorption spectroscopy in a classical mode with x-ray diffraction
in the energy scanning mode on the same set-up without moving the sample. This is extremely
important for experiments under high pressure and high temperature where it is absolutely impossible to
move the sample.
Scientific case
It is clear that there is a great interest in following both short range and long range order for various
thermodynamical conditions (P and T). In many cases, their variation with external conditions are not
identical (melting, amorphisation, pseudo binary system as ZnxHg 1-xTe, ferroelectric perovskites…..).
For diluted impurities, the diffraction cannot provide the structural variations around the impurity but
remains necessary to follow the variation of the host structure. Combining both techniques allow to
follow directly the variation of the impurity site with the variation of the matrix. The ruby would be an
excellent candidate to illustrate this point. The ruby is widely used as a pressure sensor through the
variation of position of the fluorescence peaks with pressure. The fluorescence is due to the Cr impurity
in the Al2O3 matrix (the alumine is white while the ruby is red). Then this variation has been
extrapolated to higher pressure using calculated volume variation with pressure of different materials,
NaCl, Au, Pt … (the volume was measured using x-ray diffraction and the fluorescence of ruby by
optical technique). But up to now, no determination of the local compressibility around the Cr atom is
available. Therefore the variation of the fluorescence cannot be simulated. Such a simulation would be a
real progress in the determination of an absolute pressure scale.
Therefore the set-up described further will allow
- To follow both local order and long range order and to look at local deformation of a structure
(the structure obtained by diffraction is an average of the local structure)
- To follow the melting or the amorphisation of a material under pressure
- To perform XAS in the fluorescence mode under extreme conditions giving access to the
compressibility around minor elements in various compounds (crystallised or not).
57
Biomaterials
I. Ascone1, S. Benazeth2, J. Parello3
1 LURE, 2 LB (Paris V), 3 CBIB (Montpellier)
Biological XAS (BioXAS) experiments at SOLEIL
Background
X-ray absorption spectroscopy (XAS) has been widely used in many areas of science
during the last twenty years. Nevertheless, the development of XAS use for biomolecules - and
in particular macromolecules - has been relatively slow. BioXAS experiments can be
performed only with synchrotron radiation and the complexity of biological systems requires a
concerted action of biological research groups who use occasionally BioXAS and staff
members of SR facilities. Moreover, in Europe (in contrast with the USA) there is only one XAS
beam line fully dedicated to biology (EMBL Hamburg Outstation) and BioXAS proposals, that
are time-consuming, compete for beam time with materials science and chemistry.
Due to the high dilution of active species, BioXAS pushes the technique to its limits, from
experimental aspects (data collection, signal extraction) to theoretical analysis.
During the past 15 years, two technological advances have improved the experimental
conditions of BioXAS measurements :
- Third generation machines, like SOLEIL, produce high intensity and focalized X-ray sources.
This feature allows to decrease the biological sample concentration and/or sample volume.
- Fluorescence detectors, which are essential for measurements on diluted samples, allow a
better signal-to-noise ratio in spectra.
These technical improvements have increased the quality of BioXAS measurements : the
information obtained is more reliable as the k-range of EXAFS signal is extended.
Theory has also considerably progressed. Physical phenomena like multiple scattering
processes, which occur for instance when an histidine binds a metal, are now taken into
account by EXAFS programs. XANES simulations have improved and the fitting of XANES
is now a reality. Biological applications will particularly profit from the progresses in the
interpretation of XANES, as for very dilute samples (metal concentration < 0.1 mM) this
region of the absorption spectrum has a signal-to-noise ratio higher than the EXAFS region.
The French BioXAS community is not yet very large, but is well connected with the
international community. Three meetings have been recently organized at LURE : a meeting
[1] supported by the APD SOLEIL in 1998 , a BioXAS Workshop [2] in 2000 and a “Study
weekend” [3] on theory and refinement methods in 2001. The first BioXAS Workshop was
organized in February 1999 at the ESRF [4] and was followed by BioXAS 2000 at LURE and
BioXAS 2001 at Siena University. The BioXAS conferences and forthcoming Study Weekends
will be organized alternatively in the coming years, and there are also plans for another
Advanced Course like that one organized at EMBL [5] in June 1999. Concerted actions (such
as COST), in Europe and/or worldwide if possible, will be taken in order to ascertain the
continuity of such initiatives.
Example of BioXAS experiments
Pharmaceutical studies
Metallic compounds play a key role in a variety of biological processes and are, as a consequence,
involved in the composition of drugs and nutritional supplements. Precious insight into structure [6],
stability [7], and reactivity of such drugs can be accessed by XAS methods. Two levels are to be
58
considered : before administration and in biological samples after administration. A third point of view
concerns the pharmaceutical applications of energy transfer mechanisms.
Before administration, there is a clear need for structural characterisation, stability determination
(including characterisation of degradation by-products) and reactivity studies (including eventually
reaction intermediates stabilisation and analysis). These studies have to be performed in the real drug
system, containing a low absorber concentration stretching the need for a brilliant source and a quick
spectra acquisition. The drug sample is usually a solution or non-crystalline solid but also liposome
emulsion as in the case of parenteral nutrition solutions. Similar experiments have already been carried
on at LURE about antitumoral drugs containing Pt or As and Zn/Cu parenteral nutrition preparations,
but with an increased metal concentration due to the low LURE beam brilliance [8].
After administration, there is a need to trace and characterise the metabolites of drugs : for example Asbased antileukaemia drugs are traced in hairs and urine of patients ; some preliminary results have been
obtained demonstrating the clinical interest of such data. Besides this elemental analysis, the metallic
speciation in tissues has to be determined, being often related to toxicity [9] (for instance copper
distribution in enteral wall cells after oral administration, or Fe, Zn and Cu speciation in various tissues
after parenteral administration of different complexes). The tissue and hair characterisations are to be
performed on very diluted and small samples and are well suited for a micro-XANES or micro-EXAFS
experiment involving a brilliant beam focalised at the micron scale (see below). On the other hand the
urine analysis can be considered in a coupled chromatography-XAS system to achieve in-situ separation
of the metabolites before spectrum recording.
The energy transfer resulting from the coupling of lanthanides with drugs is used as well for detection
purposes (for example fluorescence enhancement for anti-inflammatory drug detection) and for local
irradiation in photo-therapy. The coupling of UV-visible spectroscopy with XAS is to be considered in
order to simultaneously acquire knowledge on these processes, again in conjunction with a quick
EXAFS configuration.
Metalloproteins in post-genomics studied by XAS
Genome programmes have recently given access to sequences of various organisms including the entire
human genome. The next step is now the structural characterization of a very large number of proteins.
Several projects for structural genomics have led or are leading to the creation of new research centres
world-wide [10]
The research approach is completely new. Instead of developing a specific biological justification prior
to working on a protein, biocrystallographers and NMR specialists are now considering the
determination of structures for all proteins in an organism.
In spite of the largely demonstrated capabilities of these techniques to solve structural problems, at
present the successful use of these techniques for all proteins of a genome is not assured. For instance,
there are difficulties in the crystallization of many proteins while studies in solution by NMR are
limited by molecular weight of proteins, the size limitation with usual techniques being about 150
residues. Moreover, membrane proteins are still very difficult targets.
X-ray absorption spectroscopy applied to protein study allows to determine the metal site structure of
metallo-proteins, which are estimated to make up 25-30% of all proteins. Advantages of XAS are that it
does not require extreme protein purity ; it avoids the requirement to grow crystals as proteins could be
in solution ; it is not limited by protein size ; and metal sites are described at atomic resolution [11].
The limitation of protein studies with XAS approach in comparison with X-ray diffraction and NMR is
that XAS is a local structural method, giving only a structural description of the metal site and not of
the whole protein.
Nevertheless, the access to the structure of the metal site, which often corresponds to the catalytic site in
enzymes, will help to understand catalytic processes and probe biological functions in greater depth. In
this way, XAS is complementary to NMR and X-ray diffraction and could play an important role in the
post genome science. In order to investigate this point, a Study Weekend [3] was organized at LURE in
connection with Paris-Sud University and North West UK Structural Genomics Centres [12]. The aim of
the workshop was to determine which developments in theory and refinement methods are necessary to
a wider diffusion of XAS spectroscopy among the biological community.
59
Reactivity of metalloproteins and biomimetic compounds
One important step in the study of the catalytic cycle of metalloenzymes is the conception and the
analysis of more simple model compounds. Beyond this study, the biomimetic chemistry tries to
construct some new catalysts using the same procedure as the natural catalyst, but easier to produce and
that can be used under different physical conditions (pH, temperature ...).
The variety of chemical reactions with transition elements, that explains their use in catalysis, comes
from the numerous oxidation degrees they accept. Hence, the knowledge of the exact oxidation degree
is required to understand the mechanism of the catalysis. Besides, during the catalytic cycle, the close
environment of the metal ion is modified [13] (fixation of a ligand, transformation and release of the
product) and it is important to characterize it.
X-ray absorption spectroscopy is very sensitive to both information and is a very powerful method for
this kind of studies.
Nevertheless, in general, only one of the states of the catalytic cycle is stable in usual conditions and
can be studied. To stabilize the other states, a powerful technique is to impose the potential of the
solution [14, 15]. Doing that while performing the XAS experiments is then very informative.
Especially, coupling between XAS and cyclic voltammetry allows to follow the changes of the
oxidation state and of the local environment of the metal with the different areas in the voltammogram
[16].
In order to compare spectra of the sample at the initial state and during the reaction, the use of
differential XAS would be convenient. One part of the beam irradiates a reference solution, for instance
the catalyst in the stable form, whereas the second part irradiates the excited catalyst in the state
imposed by the potential or the photoexcitation. The high brilliance expected for Soleil makes this kind
of experiments possible and allows to determine small structural variations.
BioXAS strategies and perspectives.
A rigorous treatment of XAS experimental data involving metal cation-binding biological
macromolecules requires a strong experimental effort using small molecule models having the
following characteristics : (i) they must closely mimic the molecular environment of the scattering
metallic ion within its binding site in the biological macromolecule, (ii) they must have well
characterized X-ray structures. Such a modelling effort will certainly require that XAS experiments be
carried out with the small molecule systems in solution as well as in the crystal. The latter case is
crucial if exact parameters are needed for calculations with the biological samples. A great deal of work
has been carried out to date with biological macromolecules substituted with transition metal cations
(either as constitutive cations or as probes). This certainly reflects the availability and sensitivity of the
experimental devices commonly in use in the SR sources. However, several cationic species, including
Ca2+ and Mg2+ with lower Z values, are essential for biological function and are used by a large variety
of proteins in signalling pathways under in vivo conditions. Ca2+ can be reached by XAS in the 4 keV
region (see below). It can be predicted that XAS could help enormously the study of novel Ca2+-binding
proteins that can be readily identified on the basis of local amino acid sequences (full or partial EF hand
motifs) within the primary structures inferred from genomics. Several Ca2+-coordination scenarios are
presently known for the calciproteins. Since EXAFS is particularly accurate in determining metalligand distances, as well as coordination numbers, it would be of real interest to investigate different
types of Ca2+-binding modes by EXAFS (canonical EF hands, MIDAS-type Ca2+-binding sites as in the
integrins to take some examples). Obviously, this requires that the XAS SR beam lines will offer the
required energy range for such studies at the K-edge of Ca (see below).
It is certainly possible to foresee time-resolved XAS experiments with a variety of metalloproteins. As
mentioned above, the case of the calciproteins could be highly relevant; in this respect Ca2+/Mg2+
exchange in many of the calciproteins is part of the regulatory processes that underlie the role of these
proteins in vivo (muscle and neuron activity). Laser-monitored experiments with photoactivatable Ca2+
cages, as well as stopped-flow experiments, could be envisaged to follow Ca2+/Mg2+ exchange by
EXAFS in calciproteins with a time resolution down to the ms time scale. This could be feasible if the
exchange kinetics are under the control of external parameters such as temperature and/or pressure, to
slow down the exchange process when necessary. Such types of XAS experiments could favorably
complement time-resolved X-ray crystallographic studies with metalloproteins.
60
[
1] Workshop on "Spectroscopie d'absorption X en biologie structurale et chimie bioinorganique pour les sources
synchrotron de troisième génération". Supported by “APD SOLEIL” and LURE. Organized by I. Ascone, S.
Bénazeth, R. Fourme. December 7-8 1998 (80 participants).
[
2] BioXAS 2000 European Workshop on X-ray Absorption for Biology LURE 3-4 juillet 2000 (65 participants:
23 from Europe and USA). Organized by I. Ascone S. Bénazeth, R. Fourme
[
3] BioXAS Study Weekend: “Contribution of BIOXAS to Structural Genomics: developments in theory and
refinement methods” organized at LURE (Orsay) by I. Ascone, R. Fourme, and S. Hasnain in June/July 2001
[
4] BioXAS Workshop organized at the ESRF by Michael Borowski, José Goulon, Peter Lindley, Sakura
Pascarelli, and Armando Solé in February 1999
[
5] “Advanced Training Course in the use of Fluorescence X-Ray Absorption Spectroscopy in Biology”,
organized at the EMBL Hamburg Outstation by Wolfram Meyer-Klaucke and Paola d’Angelo in June 1999.
[
6] Differentiation of biological hydroxyapatite compounds by infrared spectroscopy, X-ray diffraction and
extended X-ray absorption fine structure. E. Chassot, H. Oudadesse, J.-L. Irigaray, E. Curis, S. Bénazeth,
I. Nicolis, Journal of Applied Physics, décembre 2001, vol. 90 n° 12, p.6440–6446.
The Recharacterization of a Polysaccharide Iron Complex (Niferex). E. M. Coe, L. H. Bowen, J. A. Speer,
Zhihai Wang, D. E. Sayers, R. Bereman, Journal of Inorganic Biochemistry, 1995, vol. 58, p. 269–278.
Preparation and characterisation of copper (II) hyaluronate. E. Tratar Pic, I. Arcon, P. Bukovec, A. Kodre.
Carbohydrate Research, 2000, vol. 324, p. 275–282.
Studies of the Structure and Composition of Rhenium-1,1,-hydroxyethylidenediphosphonate (HEDP) analogues of
the Radiotherapeutic Agent (186)ReHEDP. R. C. Elder, J. Yuan, B. Helmer, D. Pipes, K. Deutsch, E. Deutsch,
Inorganic Chemistry, juillet 1997, vol. 36 n° 14, p. 3055–3063.
Determination of Atomic Local Order in Thyroid Hormones by Extended X-Ray Absorption Fine Structure
[EXAFS] for Radiation Dose Estimates. B. R. Orton, D. Vorsatz, D. Macovei, Acta Oncologica, 1996, vol. 35
n° 7, p.895–899.
Calcium Environment in Encrusting Deposits from Urinary Catheters Investigated by Interpretation of EXAFS
Spectra. D. W. Hukins, L. S. Nelson, J. E. Harries, A. J. Cox, C. Holt. Journal of Inorganic Biochemistry, juin
1989, vol. 36 n° 2, p. 141–148.
[
7] Carboplatin decomposition in aqueous solution with chloride ions monitored by X-Ray absorption
spectroscopy. E. Curis, Karine Provost, I. Nicolis, D. Bouvet, S. Bénazeth, S. Crauste-Manciet, F. Brion,
D. Brossard, New Journal of Chemistry, décembre 2000, vol. 24, p. 1003–1008.
Carboplatin and Oxaliplatin Decomposition in Chloride Medium, Monitored by XAS. E. Curis, K. Provost,
D. Bouvet, I. Nicolis, S. Crauste-Manciet, D. Brossard, S. Bénazeth, Journal of Synchrotron Radiation, mars
2001, vol. 8 n° 2, p. 716–718.
[
8] XAS Applied to Pharmaceuticals: Drug Administration and Bioavailability. I. Nicolis, P. Deschamps, E. Curis,
O. Corriol, V. Acar, N. Zerrouk, J.-C. Chaumeil, F. Guyon, S. Bénazeth, Journal of Synchrotron Radiation,
mars 2001, vol. 8 n° 2, p. 984-986.
[
9] XANES Spectroscopy of a Single Neuron from a Patient with Parkinson’s Disease. S. YOSHIDA,
A. EKTESSABI, S. FUJISAWA, Journal of synchrotron radiation, mars 2001, vol. 8 n° 2, p. 998–1000.
Distribution and chemical states of iron and chromium released from orthopedic implants into human tissues.
A. Ektessabi, S. Shikine, N. Kitamura, M. Rokkum, C. Johansson, X-Ray Spectrometry, 2001, vol. 30 n° 1,
p. 44–48.
[10] “A new era” Tracy Smith Supplement of Nature Structural Biology volume 7 Number 1, 927 – 994. In the
same volume: “An overview of structural genomics” Stephen K. Burley; 932 – 934; “Structural genomics in
Europe: Slow start, strong finish?” Udo Heinemann, 940 – 942.
[
11] Structure of metal centres at subatomic resolution. S. S. Hasnain and Keith O. Hodgson. J. Synchrotron
Radiation (1999) 6 852-864.
[
12] http://www.nwsgc.ac.uk/.
[
13] I. Ascone, R. Castagner, C. Tarricone, M. Bolognesi, M. E. Stroppolo, A. Desideri. Evidence of His61
imidazolate bridge rupture in reduced crystalline Cu,Zn superoxide dismutase BBRC, (1997) 241,119-121.
[
14] I. Ascone, A. Cognigni, M. Giorgetti, M. Berrettoni, S. Zamponi, R. Marassi “X-ray absorption spectroscopy
and electrochemistry on biological samples” Journal of Synchrotron Radiation, (1999) 6, 384-386
[
15] M. Giorgetti, I. Ascone, M. Berrettoni, P. Conti, S. Zamponi, R. Marassi “In-situ XAS
spectroelectrochemical study of hydroxocobalamin” Journal Biological Inorganic Chemistry (2000) 2005, 156166.
[
16] A. Cognigni, I. Ascone, S. Zamponi R. Marassi “A quasi-solid state electrochemical cell for in situ EXAFS
measurements on biological samples.” J. Synchr. Rad. (2001), 8, 987-989.
61
Laboratories support
France
European Countries
Institut de Biologie Structurale et Microbiologie Laboratoire de chimie bioinorganique — Université
d'Heraklion — Crète
CNRS, Marseille
Contact scientist: A.Coutsolelos
Contact scientist: Mireille Bruschi
Department of Biochemistry — University of Oslo
Chimie Biomoléculaire et Interactions Biologiques, Contact scientist : K.Andersson
Montpellier UMR CNRS 5074,
Contact scientists: Joseph Parello and Jean Louis Laboratorio di Biofisica and INFM, Dipartimento di
Fisica,
Baneres
Universita’ « La Sapianza » Rome Italie
Contact scientist: A. Congiu Castellano
Groupe de Physique des Milieux Denses,
Université Paris XII Val de Marne, Créteil
Dep. of Biology
Contact scientists: Alain Michalowicz, K. Provost and University of Padova, Padova, Italy
D. Bouvet
Contact scientist: B Salvato
Laboratoire de Biomathématiques
INFM, Dipartimento di Matematica e Fisica,
Faculté de Pharmacie, Université Paris 5, Paris.
Universita' di Camerino, Camerino (MC) Italy
Contact scientists: Bénazeth Simone, Curis Emmanuel Contact scientist: Andrea Di Cicco
and Nicolis Ioannis
Dipartimento Scienze Chimiche
URA
CNRS
2096
&
SBPM/DBCM/CEA Universita' di Camerino, Camerino (MC) Italy
Contact scientist: Roberto Marassi
Centre d'Etudes de Saclay , Gif-sur Yvette
Contact scientist: Philippe Champeil (Inserm)
Lab. de Physique Corpusculaire, Université Blaise
Pascal
Contact scientist: Emmanuelle Chassot
Laboratoire de chimie bioorganique et bioniorganique
— Centre d'orsay — Université Paris XI
Contact scientist: J.P. Mahy
Laboratoire de pharmacie galénique
Faculté de Pharmacie, Université Paris V. (EAD 2498)
Contact scientist: J.C. Chaumeil
Institut de Génétique et Microbiologie
Université d’Orsay
Contact scientist: Béatrice Felenbok
Laboratoire de Génétique des Virus, UPR 9053 CNRS
Gif sur Yvette
Contact scientist: Rey Félix
Laboratoire de Radiolyse, DRECAM, CEA Saclay
Contact scientist: Serge Pin
LCM Institut de Biologie Structurale, Grenoble
Contact scientist: Richard Kahn
Fondation scientifique Fourmentin-Guilbert Paris
Contact scientist: Jean Fourmentin
LURE, UMR 130, Université Paris-Sud Orsay
Contact scientist: Isabella Ascone
62
Research in Environmental Sciences at the nanometric scale, i.e., at the molecular level,
concerns research groups from various disciplines such as earth sciences, chemistry, biology,
catalysis, and material sciences. The scientific knowledge developed in Environmental
Sciences provides some bases for the understanding of polluted site reclamation, improvement
of water quality, waste management, …
Synchrotron sources are essential tools for these subjects, and among the various
synchrotron techniques, XAS spectroscopy is of particular importance. It is certainly one of the
only techniques able to probe the local environment of any element in natural systems (soils,
sediments, snow, plants, microorganisms …) generally composed of micro-crystals or
amorphous phases. In the case of waste treatment, XAS spectroscopy allows the
characterization of the speciation of toxic elements, and a better understanding of the stability
of the products.
Nowadays, FAME beamline at the ESRF, which is mostly dedicated to Environmental
Sciences, opens large possibilities for the study of dilute systems in the 4-40 KeV energy range
by XAS, and soon by micro-XAS thanks to the development of micro-focalizing optics.
However, the beamtime available on this beamline is not sufficient to satisfy the
increasing needs in Geosciences, and another XAS beamline, complementary to FAME, i.e.,
allowing the study of less dilute samples, at high and low temperature, in variable redox
conditions and states, in the 4-40 keV energy range, is essential for the Environmental
Sciences community to produce a research of high quality. Moreover, the beamtime demand on
FAME will be greatly increased consecutively to the closure of LURE. Studies concerning
contaminations or waste treatment do not necessarily require a 10-micron focalization, and
the concentrations of the elements of interest may be higher than 0.1% weight in some cases.
Finally, in parallel to the observation of natural materials, the study of synthetic compounds is
generally necessary to compare the results and understand the general laws governing the
chemistry of the systems. In this case, samples can be homogeneous and concentrated.
The workshop that took place in Molsheim on the 7th and 8th of April 2001, involving the
British and French communities in Environmental Sciences, concluded on the necessity to
develop a XAS beamline on SOLEIL, complementary to FAME beamline.
Laboratories support :
Laboratory: LGIT-Géochimie de l'Environnement (UMR 5559), Univ. J. Fourier et CNRS, BP 53, 38041
Grenoble Cedex 9
Research areas: Speciation of trace elements in contaminated systems (soils and sediments): Interactions with
minerals and organic components (organic matter, plants, microorganisms). Adsorption mechanisms at the solidsolution interface. Structure of finely divided minerals.
Scientists involved: Alain Manceau (DR1 CNRS), Bruno Lanson (CR1 CNRS), Géraldine Sarret (CR2 CNRS).
Laboratory: CEREGE (UMR 6536) Europôle Méditérannéen de l'Arbois, 13545 Aix en Provence
Research areas: Physical chemistry of the hydrolysis of cations (colloids). Water and soil pollutions. Waste
treatment. Speciation of trace elements in cements.
Scientists involved: Jérome Rose (CR1-CNRS), Armand Masion (CR1-CNRS), Jean-Yves Bottero (DR1-CNRS)
Laboratory: Laboratoire Environnement et Minéralurgie, ENSG-INPL-CNRS UMR 7569 BP 40 54501
VANDOEUVRE CEDEX
Research areas: Hydrolysis-Condensation. Aggregation. Adsorption mechanisms at the solid-solution interface.
Scientists involved: Bruno Lartiges (MC), Laurent Michot (DR2 CNRS) Emmanuelle Montargès-Pelletier
(Contractuelle), Fabien Thomas (DR2 CNRS), Frédéric Villiéras (CR1 CNRS).
63
X-RAY ABSORPTION AND GEO-RISK ASSESSMENT
Contributions for a new-, hard x-ray beamline at SOLEIL
for the understanding of environmental issues.
F. Farges, S. Djanarthany, M. Harfouche, V. Malavergne, M. Munoz, S. Rossano
C. Lapeyre, J.-M. Le Cleac'h et M. Deveughèle
Laboratoire des Géomatériaux (Marne la Vallée).
Natural systems (magmas, clays, ceramics or fluids) are complex media, characterized by a
complex structure and chemistry, and which durability is highly time-dependant. Among the Earth
materials at the source of a potential georisk, fluids (like water), heavy metals (like lead), radio-activity
(natural or artificial) and organic artificial molecules (such as pesticides) are among the most
perturbating environmental agents. This is therefore crucial, for the conservation of the environments
(the planet being now a global ecovillage), to understand and model the effect of eco-pathogenic agents
on the ecosystems. If most models require on-site laboratory resources, direct experiments on
environmental issues often require an in-situ-, multi-parameter study on particularly fragile or
unquenchable samples.
To progress on natural system knowledge, our group has been actively using Synchrotron radiation
experiments in the 4 - 40 keV range. In a recent past, we obtained unique and accurate information on,
for example, the effect of water on the structure of highly explosive magmas [1-4] contamination of
heavy metals in soils [5] and the effects of radiation damage on materials used to confine nuclear wastes
[6]. This achievement was made possible by the recent opening of new-, third generation synchrotron
sources, mostly located abroad (USA, Germany). In the same time, the European (ESRF) and the old
French (LURE) sources were also used somewhat, but their design is not well adapted for studying
natural samples (need of high lateral-, and energetic resolution together with a maximum beam stability
and moderate photon flux) or their access was sometimes difficult (ESRF).
Our group has been highly involved in the building, commissioning or even partial design of
several environmental beam lines or components (APS, ESRF, SSRL, SLS). Our next priority, in our
new ‘volet recherche’ of the ‘plan quadriennal’ to come (2002-2006), is to be highly involved in any
support of this hard x-ray absorption beam line at SOLEIL. This is because they would be more and
more critical environmental issues to be clarified using this unique tool.
[1] Farges F. et Rossano S. (2000) European Journal of Mineralogy 12, 1093.
[2] Farges F., Munoz M., Siewert R., Malavergne V., Brown, G.E., Jr., Behrens H., Nowak M. and Petit, P.-E.
(2001) Geochimica et Cosmochimica Acta 86, 1679.
[3] Petit P.-E., Farges F., Wilke M. et Solè A. (2001) Journal of Synchrotron Radiation 8, 952.
[4] Wilke M., Farges F., Petit P.E., Brown, G.E. Jr and François Martin (2001) American Mineralogist 65, 713.
[5] Berrodier I., Farges F., Benedetti M. et Brown G. (1999) Journal of Synchrotron Radiation S6, 651.
[6] Farges F., Harfouche M., Petit P.-E., Brown, G.E., Jr. and Manuel Munoz (2002) Second Euroconference and
NEA workshop on Speciation, Techniques, and facilities for radioactive materials at synchrotron light sources.
ESRF, Gremoble, September 2000 (in press).
**********
Molecular environment of As, Pb, U and Zn in soils and mine-tailings.
G. Morin, F. Juillot, T. Allard, L. Galoisy
LMCP (Paris 6 & 7)
At Earth’s surface, the mobility and bio-availability of trace elements is mostly driven by surface
reactions on mineral and organic phases, as well as metabolic reactions within living organisms. These
interactions lead to a variety of sinking mechanisms such as precipitation of mineral phases and
sorption processes that are able to delay the dissemination of toxic elements in the environment. Our
recent XAS investigations allowed us to evidence the role of these processes in sequestering lead
(Morin et al. 1999 ; Morin et al., 2001), uranium (Allard et al. 1999), zinc (Juillot et al., submitted) and
arsenic (Juillot et al., 1999 ; Morin et al. 2002) in natural or polluted media.
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The main difficulty to investigate the speciation of trace elements in such heterogeneous media as
soils and sediments comes from the fact that an element often occurs under a wide variety of chemical
forms in the same sample, including atomic-scale surface species which can only be identified by
element selective spectroscopic techniques as XAS.
For instance, our recent works aimed at assessing the influence of microorganisms on the oxidation
state of arsenic and on the nature of As-Fe-bearing solids in Acid Mine Drainage systems, which
exhibits exceptionally high As level in waters. High-resolution XANES spectroscopy at the As K-edge
was used to measure directly arsenic oxidation state in suspended sediments and bacterial accretion
(stromatolites) as well as in samples obtained from bioassays. EXAFS spectroscopy at the As and Fe Kedges was used to distinguish among crystalline species as well as co-precipitation and adsorption
mechanisms.
The comparative study of field samples and of in-vitro samples prepared in biotic or abiotic
conditions, has allowed us to assess the role of various selected bacterial strains, in catalyzing Fe(II) to
Fe(III), and As(III) to As(V), oxidation reactions and in governing the structure of hydrated As-Fe gels
and/or crystalline phases formed in Acid Mine Drainage systems (Morin et al. in prep).
Morin G., Ostergren J., Juillot F., Ildefonse Ph., Calas G. and Brown JR. G.E. (1999) XAFS determination of the
chemical form of lead in smelter-contaminated soils and mine tailings: Importance of sorption processes.
American Mineralogist 84, 420-434.
Juillot F., Ildefonse Ph., Morin G., Calas G., De Kersabiec A.M. and Benedetti M. (1999). Remobilisation of
arsenic from buried wastes in an industrial site: mineralogical and geochemical control. Applied Geochemistry
14, 1031-1048.
Morin G., Juillot F., Ildefonse Ph., Samama J.-C., Brown JR. G.E., Chevallier Ph. and Calas G. (2001)
Mineralogy of lead in a Pb-mineralized sandstone (Ardèche, France). American Mineralogist 86, 92-104.
Dumat C., Chiquet A., Goody D., Aubry E., Morin G., Juillot F. and Benedetti M. F. (2001) Metal ion
geochemistry in smelter impacted soils and soil solutions. Bulletin de la Société Géologique de France
172, 539-548.
Morin G., Lecocq D., Juillot F., Ildefonse Ph., Calas G., Belin S., Briois V., Dillmann PH., Chevallier Ph.,
Gauthier CH., Sole A., Petit P-E., and Borensztajn S. (2002) EXAFS evidence of pharmacosiderite and arsenic(V)
sorbed on iron oxides in a soil overlying the Echassiere geochemical anomaly, Allier, France. Bulletin de la
Société Géologique de France, in-press.
Juillot F., Morin G., Ildefonse Ph., Trainor T.P., Benedetti M., Galoisy L., Calas G. and Brown Jr. G.E. (2002)
Occurrence of Zn/Al Hydrotalcite in Smelter-Impacted Soils from Northern Franc e: Evidence from EXAFS
Spectroscopy and Chemical Extractions. Submitted to American Mineralogist.
Synthetic glasses
L. Galoisy, L. Cormier, G. Calas
LMCP (Paris 6 & 7)
Silicate glasses
Silicate glasses with various compositions corresponding to different degrees of polymerization
have been synthesized and the local environnement around nickel has been determined using XAS.
Interatomic distances and the symmetry of the site occupied by nickel give a precise image of the
environment of this element in the investigated glasses. Although Ni2+ is usually found in octahedral
site in minerals, these studies showed that this element is found in two unusual sites : A 5- and 4coordinated site. The relative proportion of the two sites varies as a function of the glass composition.
Beyond the information given by the coordination number of Ni2+ in these glasses, it has been shown
that these sites were representative of two distinct networks in the structure of the glass. When 4coordinated, Ni2+ belongs to a network in which NiO4 tetrahedra are linked with SiO4 tetrahedra with
Ni-O-Si angles which are especially small. When 5- coordinated nickel is located in a network ordered
at the medium range in which the Ni-Ni distances are representative of a a sub compact lattice. We also
performed experiments (EXAFS and XANES) to follow the evolution of the spectra as a function of the
temperature for a Na2Si2O5:Ni glass chosen for its low melting point and also because a coloration
change was observed when quenching the glass that could be related to a structural change. In the liquid
state (900°C), the short Ni-O distances showed that Ni2+, is exclusively located in a tetrahedral site at
difference from what is observed in the glassy state. An important structural change is thus evidenced
for this glass composition.
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Galoisy L. and Calas G. (1991)" Spectroscopic Evidence for five-coordinated Ni in CaNiSi2O6 Glass". American
Mineralogist, vol 76 (9-10) p 1779 - 1782
Galoisy L. and Calas G. (1992) " Network forming Nickel in silicate glasses ".American Mineralogist, Vol.77, p
677-680
Galoisy L. and Calas G. (1993) " Structural environment of nickel in silicate glass/melt systems. I. Spectroscopic
determination of coordination states". Geochimica Cosmochimica Acta Vol. 57 p 3613 - 3626
Galoisy L. and Calas G. (1993) "Structural environment of nickel in silicate glass/melt systems. II.Geochemical
implications".Geochimica Cosmochimica Acta Vol. 57 p 3627 – 3633
Farges F., Brown G.E. Jr., Calas G., Galoisy L., and Waychunas G. (1994) “ Structural transformations in Nibearing Na2Si2O5 glass and melt”. Geophysical Research Letter n°28 p 1931-1934
Farges F., Brown G.E. Jr., Calas G., Galoisy L., and Waychunas G. (1995) “Coordination change around 2 wt%
Ni in Na2Si2O5 glas/melt systems “. Physica B 208&209 p 381-382
Cormier L., Creux S., Galoisy L., Calas G. and Gaskell P. (1996) “ Medium range order around cations in
silicate glasses “. Chem.Geol. 128 p 77-91
L. Galoisy, L. Cormier, S. Rossano, A. Ramos, M. Le Grand, G. Calas and Ph. Gaskell (2000) “ Cationic
ordering in oxide glasses: the example of transition elements “. Mineralogical Magazine Vol. 64 (3) p207-222
Borate glasses
Local and medium range order in low alkali borate glasses (10 mol%) around Ni, Co and Zn have been
studied using XAS. First, it has been shown that the local environment around nickel in these glasses is
exceptional. Nickel is found in an octahedral site on the contrary to what is usually observed in silicate
glasses.
The medium range order around this element is related to the presence of the boroxol rings constitutive
of this low alkali borate glassy network. Nickel is located in highly ordered domains (up to 6Å) close to
the CFC NiO structure. Around Co and Zn in the same types of glass, the structure appears to be
similar. For Zn, the medium range order is also close to the CFC structure of ZnO. However, this is not
the stable structure for this oxide at room temperature and pressure, this structure being stable at high
pressure. Finding such a structure, even if deffective, in the glass around Zn, shows that the boroxol
network induces high constraints on the medium range order around this element in such glasses.
Cormier L., Galoisy L., Calas G. (1999) « Evidence of ordered domains in nickel-bearing alkali borate
glasses ». Europhysics Letter 45 (5) p.572-578
Galoisy L., Cormier L., Calas G. and Briois V. (2001) « Environment of Ni, Co and Zn in low alkali borate
glasses: information from EXAFS and XANES spectra ». Journal of Non Crist. Solids 293-295 p 105-111
Nuclear waste glasses
L. Galoisy, L. Cormier, G. Calas, G. Morin, A. Ramos
LMCP (Paris 6 & 7)
This study is a collaboration between the CEA (Valrho, Marcoule) and our Laboratory. We
want to establish the relationships between the structure of the nuclear waste glasses, their synthesis and
their behavior during long time storage (resistance to leaching, effects of radiations) following the
objectives of the 1991 law.
Using XAS, we studied the environment of fission products (Pd, Ru, Zr, Mo and Zn) in inactive glasses
(thèse M. Le Grand, 1999).
Precipitates are formed with elements present in the glass composition, in the high level nuclear wastes
glasses during incorporation of noble metals (Pd, Ru). Structural and bonding characteristics of (Pd, Te)
precipitates have been determined in a R7T7 French glassform using EXAFS. In this glassform, the
precipitates show an homogeneous composition, with about 10 wt% Te and retain a face-centered cubic
structure as in pure Pd. The cell parameter increases accordingly to Vegard's law. EXAFS shows the
presence of Te in the Pd coordination shell, with Pd-Te distances of 2.80 Å, i.e. 0.05 Å higher than in
pure Pd. The comparison with the average distances obtained by X-ray diffraction shows the nonmetallic character of the Pd-Te bond in these precipitates, in relation with the limited extent of the
partial Pd-Te solid solution.
66
Zirconium is 6–fold coordinated in these glasses with sodium and calcium compensating the charges.
Zinc is located in a tetrahedral site in network former position with a high connection to the borosilicate
network. Molybdenum is found under the molybdate form without any direct connection with the
network. This explains the precipitation of crystalline molybdate phases which are sometimes observed
when quenching the glass under special synthesis conditions.
The structural modifications of these glasses during leaching by solutions with compositions simulating
geological waters, have been studied using XAS (E. Pelegrin, 1999). Zr changes local environment due
to a loss in sodium or calcium. The structure of the glass is modeled using molecular dynamics and
Reverse Monte Carlo. XAS spectra are in process of being simulated to understand the competition
between the various cations to compensate the charge of Zr in these glasses and the alteration products.
Radiation effects are also studied using XAS to understand the structural modifications which occur in
irradiated glasses around specific cations such as Fe, Zr and Zn.
L. Galoisy, G. Calas, S. Pugnet, F. Pacaud and G. Morin. (1998). Structure of Pd-Te precipitates in a simulated
high-level nuclear waste glass Jour. Materials Research 13 (5) p 1124-1127.
L. Galoisy, J.M. Delaye, D. Ghaleb, G. Calas, M. Le Grand, G. Morin, A. Ramos and F. Pacaud (1998). Local
structure of simplified waste glass : complementarity of XAS and MD calculations. Scientific basis for Nuclear
Waste Management XXI p 133-139.
L. Galoisy, E. Pelegrin, M.A. Arrio, G. Calas, A. Ramos and F. Pacaud (1999). Evidences for Six coordinated Zr
in inactive nuclear Waste glasses. Jour. American Ceram. Soc. p. 2219-2224.
Le Grand M., Ramos A. Y., Calas G., Galoisy L., Ghaleb D. and Pacaud F. (2000). Zinc environment in
aluminoborosilicate glasses by Zn K-edge EXAFS spectroscopy. Jour. Mat. Res. vol.15 n°9p2015-2019.
Cabaret D., Le Grand M., Ramos A., Flank A.-M., Rossano S., Galoisy L., Calas G. and Ghaleb D. (2001).
Medium range structure of borosilicate glasses from Si K-edge XANES : a combined approach based on multiple
scattering and molecular dynamics. Journal of Non Cryst. Solids 289 p 1-8.
Le Grand M., Calas G., Galoisy. L and Ghaleb D. Structural location of molybdenum in borosilicate glasses : an
EXAFS study (submitted).
Volcanic Glasses
L. Galoisy, M. A. Arrio, G. Calas
LMCP (Paris 6 & 7)
One of the most important parameters in the modeling of magmatic systems concerns controls on
the oxidation state of the magma in response to crystallization under close or open system conditions. In
addition, oxygen fugacity changes from the reducing conditions during crust or mantle melting to
oxidizing conditions prevailing at the Earth surface during magmatic eruptions. The redox state of iron in
magmas reflects the prevailing oxygen fugacity. Thus, an estimate of the redox conditions in a volcanic
glass (which represents a quenched melt) will give information on the atmosphere encountered during
the cooling of the magma above the glass transition temperature, and hence on the magma dynamics
during volcanic eruptions. Volcanic glasses encompass obsidians which result from the cooling of
viscous silicic magmas and basaltic glasses, obtained by fast quench of more fluid melts (oceanic sea
floors). High resolution XANES spectra of iron allow to take into account the effects of the coordination
numbers on the quantification of redox values. Volcanic glasses show split pre-edge features, arising
from a bimodal distribution between the relative contributions of ferric and ferrous iron. The chemical
shift between these two oxidation states, 2 eV, has been resolved using a 400 Si monochromator. High
resolution pre-edge spectroscopy shows the distribution of ferric and ferrous iron between various
coordination states. Ferrous iron is mostly 5-coordinated and minority 4-coordinated while ferric iron
3+
occurs in 4- and 6-fold coordinated sites. The importance of Fe in basaltic glasses may explain the
3+
formation of magnetite during glass oxidation. The increase of Fe in the more silicic, pantelleritic glass,
is consistent with the peralkaline character of this glass. The increase of the proportion of tetrahedral
3+
3+
Fe , accompanied by more covalent Fe O bonds, is consistent with the chemical dependence of redox
equilibria in magmatic systems, in which the most differentiated terms correspond to more oxidizing
compositions.
L. Galoisy, G. Calas and M. A. Arrio (2001) « High-resolution XANES spectra of iron in minerals and glasses:
structural information from the predge region ». Chem. Geol. 174 p 307-319.
67
Arrio M.A., Rossano S., Brouder C., Galoisy L. and G. Calas (2000) « Calculation of multipole transition at the
Fe-K pre-edge through p-d hybridisation in the ligand field multiplet model ». Europhys. Let., 51 (4) :454-460.
**********
Geosciences at the CEREGE
J.Rose, A. Masion, J. Y . Bottero, J-M Garnier
CEREGE (Aix en Provence)
Our need in XAS experiments can be divided in few research fields:
Cement and heavy metals
The effect of leaching on the crystallographic sites of trace metals in cements
The aim of this study is to determine the leaching mechanisms of heavy metals during the interaction of
the Cement with water. The strategy adopted is to couple different spectroscopic techniques such as
NMR and XAS with electron microscopic investigations (TEMHR-EELS, SEM). This methodology
will provide a multiple scale structural analysis of the major phases of cement as well as a
charaterization of the speciation of heavy metals (mainly Cr, Pb, Cu and Zn) during leaching. Since the
concentration of heavy metals in cement is low (lower than 300 ppm) we need a brillant source as well
as a sensitive detector (multi-element fluorescent detector).
Solidification/Stabilization of heavy metals with cements
This aim of this type of experiment is different form the previous one. In this type of study, the goal is
to stabilize waste thus the concentration of HM is higher (in the order of few %). A beamline on which
XRD is coupled to XAS could give precious information on the mechanism of fixation of HM and to
improve the stabilization process.
Collaborators :
J.Rose CNRS, CEREGE, physical-chemistry group
J-M Garnier, CNRS, CEREGE. physical-chemistry group
J. L. Hazemann, CNRS, Laboratoire de Cristallographie-Bp166. 38042 Grenoble. CEDEX9
W.E. Stone (Solid state NMR of 29Si and 27Al) ULB, Phys. General, Av. F. Roosevelt 1050 Bruxelles Belgium
C.Haehnel ATILH ( = Cement industry), 7 place de la defense, 92974 Paris-La defense
Speciation of pollutants (such as As, Pb, Cd, Cu) in natural systems (contaminated or
not)
Transfert of heavy metals in contaminated soil from the north of France
The aim of this project is to better understand the molecular environment of heavy metals (Zn, Cd, Pb)
in the Soil-Microorganism-Plant system and to determine the effect on the several biological
compartments of this system. For this project a high flux is needed since the concentration of Cd for
example is lower than 300 ppm.
Collaborators
D. Petit Prof., Laboratoire de Génétique et Evolution des populations végétales 59655 Villeneuve d’Ascq cedexFrance
J. Balesden, INRA, Laboratoire d’Ecologie Microbienne de la rhyzosphère, CEN de Cadarache, 13108 SaintPaul-les-Durance-France
G. Sarret Groupe de Géochimie de l’Environnement du LGIT, 38041 Grenoble Cedex-France
Transfert of As from contaminated groundwater to drinking water : As-Fe interaction study
The arsenic content of drinking water is a growing concern in many parts of the world, and in
particularly in West Bengal, India, and Bangladesh where most of the population relies on millions of
tubewells that tap into the groundwarter aquifers of the Ganges-Brahmaputra delta. The objective is to
understand, and eventually predict, As behavior under the wide range of conditions (e.g. other ions
present, Eh, sediment type) characteristic of the Ganges-Brahmaputra delta. The study of the
68
interactions of As with Fe, and also with inorganic ligand (phosphate, silicate...), organic ligand and
microorganism will be carry out in part with the help of XAS. For this project XAS will be performed
at the LURE synchrotron at the Fe, As and also P K edges. Currently we are limited in the analysis of
only highly polluted water since the use of second generation synchrotron for these natural diluted
samples is not well adapted. More over experiments are conducted on synthetic samples to better
understand the As-Fe relation during redox cycles. XAS is certainly the only technique allowing us to
follow As and Fe speciation during Redox reactions.
Collaborators
S Thoral , CEREGE, physical-chemistry group
L van GEEN, university of columbia, Palisades, N-Y, USA
P Refait, université de la Rochelle
A-M Flank, LURE, Orsay
**********
Study of actinides and lanthanides
C. Den Auwer
CEA Cadarache.
Within the research programs related to the nuclear fuel cycle and nuclear waste repository, needs for
fundamental actinide physical chemistry studies have sharply increased within the past ten years. These
needs have been extensively described in the scientific case related to the implementation of an actinide
beam line on SOLEIL.
However, it appears that measurements carried out on non-radioactive materials must complement these
studies. They are highly related to the actinide work : actinide / lanthanide ionocovalency discrepancies,
5f orbital behavior with regards to 4d or 4f. Furthermore, model non-radioactive ions allow to simulate
the actinide behavior in the case where activity limits would be reached (Cm, Am elements).
The chemical systems of interest are the following : glasses related to nuclear waste repository, actinide
/ lanthanide selective extraction, sorption phenomena related to actinide remediation. To date, the
lanthanide cations have been the subject of most of the studies because of their chemical similarities
with the actinide ones.
The technical needs are the following (by order of decreasing priorities).
- Absorption / diffraction coupling, use of the polarized property of the beam for monocrystal
sorption studies.
- Electrochemistry of unstable ions, in situ studies.
- Micro-beam for absorption mapping.
Study of mechanisms iinvolved in thermal migration of molybdenum and rhenium in apatites, C. Gaillard, N.
Chevarier, C. Den Auwer, N. Millard-Pinard, P. Delichère, Ph. Sainsot, J. Nucl. Mat. (2001), 299, 43.
X-ray Absorption LIII and MV Edges of Hexavalent Lower Actinides, C. Den Auwer, E. Simoni, S. D. Conradson,
J. Mustre de Leon, P. Moisy, A. Bérès, Compt. Rend. Acad. Sci. Paris série IIc (2000), 3, 327.
Molecular and Electronic Structure of AnIVFeII(CN)6xH2O (An = Th, U, Np) Compounds : an X-ray Absorption
Spectroscopy Investigation. ; I. Bonhoure, C. Den Auwer, C. Cartier dit Moulin, P. Moisy, J-C. Berthet, C.
Madic, Can J. Chem. (2000), 78, 1305.
Crystallographic and X-ray Absorption Studies of Solid ans Solution State Structures of Trinitrato N,N,N',N'Tetraethylmalonamide Complexes of Lanthanides.Comparison with the Americium Complex. C. Den Auwer, M.
C. Charbonnel, M. G. B. Drew, M. Grigoriev, M. J. Hudson, P. B. Iveson, C. Madic, M. Nierlich, M. T. Presson,
R. Revel, M. L. Russel, P. Thuéry, Inorg. Chem. (2000), 39, 1487.
69
Adresses
T. Girardeau, S. Camelio, D. Babonneau
Laboratoire de Métallurgie Physique Université de Poitiers UMR CNRS 6630
SP2MI, Bd Pierre et Marie Curie Téléport 2, BP179
86962 FUTUROSCOPE CHASSENEUIL CEDEX France
Agnès Traverse
LURE, BP 34, Université Paris-Sud 91898 ORSAY Cedex
L. Bardotti, V. Dupuis, A. Hoareau, B. Masenelli, P. Mélinon, A. Perez, B. Prével, J. Tuaillon-Combes
Département de Physique des matériaux UMR CNRS 5586, 6 rue Ampère Domaine scientifique de la Doua,
F69622 Villeurbanne Cedex
Iztok Arcon
Nova Gorica Polytechnics Vipavska 13, POB 301 5001 Nova Gorica, Slovenia
CEA, Service de Physique et de Chimie des Surfaces et Interfaces, Saclay, 2LURE, Orsay
1
M. Richard-Plouet, M. Guillot et S. Vilminot.
Groupe des Matériaux Inorganiques, IPCMS, 23 rue du Loess 67037 STRASBOURG Cedex.
Laboratoire des Matériaux Inorganiques, CNRS-UMR n°6002, Université Blaise Pascal, 63177 Aubière cédex.
G. Ouvrard
Institut de Matériaux JEAN ROUXEL (IMN) – UMR 6502 Nantes
C. V. Santilli1, S. H. Pulcinelli1, K. Dahmouche1, V. Briois2 and S. Belin2
1
IQ UNESP, 14800-900 Araraquara, Brésil 2 LURE, BP 34, Université Paris-Sud 91898 ORSAY Cedex
J. C Jumas, C. Belin, L. Montconduit, J. Rozière, D. Jones, F. Favier
Laboratoire des Agrégats Moléculaires et Matériaux Inorganiques UMR5072
N. Guigue-Millot
Laboratoire de Recherche sur la Réactivité des Solides UMR 5613 Université de Bourgogne – CNRS - Equipe
"Matériaux à Grains Fins". UFR Sciences et Techniques 9 avenue Alain Savary BP 47 870 – 21078 Dijon Cedex
E. Payen
Laboratoire de Catalyse UMR CNRS N° 8010 Université des sciences et technologie de LILLE
P. Massiani, Laboratoire de Réactivité de Surface, UMR 7609 du CNRS, Université P. et M. Curie, 4 place
Jussieu, 75252 Paris Cedex 05
Laboratoire de Catalyse en Chimie Organique LACCO. Université de Poitiers.
D. Bazin,
LURE, BP 34, Université Paris-Sud 91898 ORSAY Cedex
Laboratoire de Chimie Inorganique et Matériaux Moléculaires, UMR 7071 Université Pierre et Marie Curie
Laboratoire de Chimie Métallurgique des Terres Rares, UPR209, CNRS, 2-8 rue Henri Dunant, 94320 Thiais
A. Sadoc, K.F. Kelton2
Laboratoire de Physique des Matériaux et des Surfaces, Université de Cergy-Pontoise et 1LURE Centre
Universitaire Paris-Sud, 2Department of Physics, Washington University, St. Louis, MO 63130, USA.
1
70
LPMC, UMR5617, UMII, CC 003, 34095 Montpellier Cedex 5
L. Cormier1, D. Neuville2, Y. Linard2, L. Galoisy1, G. Calas1, P. Richet2
1
Laboratoire Minéralogie-Cristallographie, UMR CNRS 7590, Universités Paris 6 et 7
2
Département des géomatériaux, Institut de physique du globe de Paris, UMR-7046 CNRS, 4 place Jussieu,
75252 Paris cedex 05.
S. Daviero Minaud, L. Montagne, O. Mentre, F. Abraham, G.Mairesse and G. Palavit, Laboratoire de
Cristallochimie et Physicochimie du Solide, U.P.R.E S. A CNRS 8012, E.N.S.C. de Lille
Physique des Milieux Condensés - Université P. et M. Curie - BP 77, 4 Place Jussieu - F 75252 Paris Cedex 05
I.Ascone LURE, BP 34, Université Paris-Sud 91898 ORSAY Cedex
F. Farges, S. Djanarthany, M. Harfouche, V. Malavergne, M. Munoz, S. Rossano, C. Lapeyre, J.-M. Le
Cleac'h et M. Deveughèle
Laboratoire des Géomatériaux / Centre de Géologie de l'Ingénieur, Université de Marne la Vallée, Ecole
Nationale Supérieure des Mines de Paris et F.R.E. CNRS.
G. Morin, F. Juillot, T. Allard, L. Galoisy, G. Calas A. Ramos, M.-A. Arrio
Laboratoire de Minéralogie Cristallographie de Paris (LMCP), UMR CNRS 7590, UPMC-P7-IPGP, case 115, 4
Pl. Jussieu, 75252 Paris Cedex 05
A. Manceau, B. Lanson, G. Sarret. LGIT-Géochimie de l’Environement (UMR559), Université J. Fourier BP 53
38041 Grenoble cedex 9.
J.Rose, A. Masion, J. Y . Bottero, J-M Garnier,. CEREGE (UMR 6536) Europôle Méditérannéen de l’Arbois,
13545 Aix en Provence.
B. Lartiges, L. Michot, E. Montargès-Pelletier, F. Thomas, F. Villiéras. LEM (UMR 7569) BP 40, 54501
Vandoeuvre cedex.
J. L. Hazemann, CNRS, Laboratoire de Cristallographie-Bp166. 38042 Grenoble. Cedex 9
W.E. Stone (Solid state NMR of 29Si and 27Al) ULB, Phys. General, Av. F. Roosevelt 1050 Bruxelles Belgium
C.Haehnel ATILH ( = Cement industry), 7 place de la Défense, 92974 Paris-La Défense
D. Petit Prof., Laboratoire de Génétique et Evolution des populations végétales 59655 Villeneuve d’Ascq cedex
J. Balesden, INRA, Laboratoire d’Ecologie Microbienne de la rhyzosphère, CEN de Cadarache, 13108 SaintPaul-les-Durance-France
S Thoral , CEREGE, physical-chemistry group, (UMR 6536) Europôle Méditérannéen de l’Arbois, 13545 Aix en
Provence.
L van GEEN, university of columbia, Palisades, N-Y, USA
C. Den Auwer, CEA Cadarache, 13108 St Paul Les Durances.
71

APS of a XAS beam line at SOLEIL

Transcription

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