Experimental Study of the Sn-Sb-Zn Phase Diagram at 150 Chung-Yung Lin( *

Experimental Study of the Sn-Sb-Zn Phase Diagram at 150℃
Chung-Yung Lin(林忠永)1,*,, Chiapyng Lee(李嘉平)2 , Wen-Horng Lee (李文鴻)3 ,
Yee-Wen Yen(顏怡文)4
1
Chin-Min Institute of Technology(親民技術學院), 2Department of Chemical Engineering, National Taiwan University of
Science and Technology(台灣科技大學化工所), 3 Department of Chemical and Materials Engineering, Lee-Ming Institute
of Technology (黎明技術學院化學工程與材料工程系), 4Graduate Institute of Materials Science and Technology, National
Taiwan University of Science and Technology(台灣科技大學材料科技所)
國科會計畫編號：NSC 95-2221-E-011-167-MY2
Abstract
The isothermal section of the Sn-Sb-Zn ternary system at 150℃ has been investigated by means
of X-ray diffraction, optical and scanning electron microscopy and electron probe microanalysis. The
ternary compound Sn30Sb25Zn45 has been confirmed. Intermetallic compounds ε-Zn4Sb3, SbSn ,ternary
compound Sn30Sb25Zn45, and Sn solid phase are in equilibrium with the β-ZnSb phase. The solubility
ranges of solid solutions and IMCs phases were determined. Up to about 4.5at.% and 1.4 at.% Sn can
dissolve in the ε-Zn4Sb3 and β-ZnSb phases, and the solubility of Zn in the Sn phase is approximately
3.2at%. Each of the Sb and SbSn phases has a limited solubility of Zn.
Keywords : Phase equilibria; Sn-Sb-Zn system; Ternary compound
1. Introduction
Lead-tin alloys have been used as soldering
materials for a long time. However, lead is a
heavy poisonous metal and can be harmful to
human health. Legislative actions in America
and Europe have pushed the electronic industry
to restrict the use of lead-containing solders [1].
Thus, there is an urgent demand for lead-free
solders in the electronic industry. Among various
lead-free solders, Sn-Sb based alloy is one of the
promising candidates for the replacement of the
high-melting-point Sn-95wt%Pb alloy [2].
Besides, Sn-Zn alloy has good mechanical
properties and low cost, and is likely a good
candidate [3]. Hence, ternary Sn-Sb-Zn alloys
may also be considered as promising lead-free
solders.
To our best knowledge, no study on the
Sn-Sb-Zn ternary phase diagram has been
published. In addition, the ternary phase diagram
of Sn-Sb-Zn system at 150 ℃ is important
during the service. Therefore, the need for
further study on the ternary phase diagram of the
Sn-Sb-Zn system at 150℃ has become pressing.
The purpose of this study is to determine the
isothermal section of the Sn-Sb-Zn system at
150℃ by experimental investigations. The
equilibrium phase relationship is proposed based
on the experimental results of the ternary alloys
obtained in this study and on the available
phase-equilibrium knowledge of the constituent
binary systems [4].
2. Experimental Procedures
Each alloy specimen, having a total mass of
1.5 g, was prepared with Zn, Sn, and Sb shots of
99.9wt% purity. Proper amounts of pure
elements were weighed and encapsulated in a
quartz tube under a vacuum of 0.1N/m2. Each
capsule was first placed in a furnace at 950℃
for 72 h before it was quenched in ice water. This
was to ensure a homogeneous liquid mixing of
the three constituent elements. The quenched
capsule was then annealed at 150℃ for 60 days
so that the equilibrium states of the alloys could
be reached. Then, the quartz tube containing the
alloy ingot was quenched in ice water. Finally,
the alloy ingot was removed from the quartz tube
and cut in half.
One half of the alloy specimen was mounted
in epoxy for metallographic analysis. Optical
microscope and scanning electron microscope
(SEM) were used for microstructure examination,
while SEM with electron probe microscopy
analysis (EPMA) was used for compositional
analysis. The second half of the alloy specimen
was pulverized and analyzed with an x-ray
diffractometer (XRD). The phases present in
each equilibrated alloy were determined by the
use
of
microstructure
examination,
compositional analysis, and XRD cooperatively.
3. Results and Discussion
The three constituent binary systems,
Zn-Sn, Zn-Sb, and Sb-Sn, have been well
established experimentally. Some features of
these binary systems are described as follows.
First of all, no intermetallic compounds exists
and there are the Zn solid solution and Sn solid
solution in the binary Zn-Sn system at 150℃ [4].
The Zn phase is a HCP structure phase with a
limited solubility of Sn. The Sn phase has almost
no solubility of Cu. Next, there are two
intermetallic compounds, β-ZnSb and ε-Zn4Sb3,
in addition to the Sb and Zn solid solutions in the
binary Zn-Sb system at 150℃ [4]. The Zn phase
has almost no solubility of Sb. The homogeneity
range of β-ZnSb is around 1.5 at.% and that of
ε-Zn4Sb3 is around 1.0 at.%. The Sb phase has
almost no solubility of Zn. Thirdly, the Sb-Sn
system was the subject of the numerous
investigations [4-6]. According to Predel and
Schwermann [5], at 150℃, the Sb phase has a Sn
solubility of approximately 12.6 at.%, and the
homogeneity range of SbSn is around 17.0 at.%.
The Sn phase has a Sb solubility of
approximately 5.0 at.% [4].
Fig. 1 is the backscattered electron image (BEI)
micrograph of alloy #12 (Sn-42at.%Sb-48at.%Zn)
annealed at 150 ℃ for 60 days. It can be
observed that there are three different
phase-regions: the dark single-phase region, the
bright single-phase region, and the grey
single-phase region. The composition of the dark
region
was
determined
to
be
Sn-43.3at.%Sb–55.2at.%Zn, while that of the
bright region was Sn-0.5at.%Sb-3.4 at.%Zn.
Compositional
analysis
results,
Sn-3.4at.%Sb-0.5at.%Zn, indicates that it is the
Sn phase in the grey region. It is concluded that
alloy #12 has Zn4Sb3, ZnSb, and Sn phases.
Based on the microstructures, the EPMA results,
and the XRD results, it is concluded that the dark
phase is the Zn4Sb3 phase with a Sn solubility of
approximately 1.5 at.%, and the bright phase is
the Sn phase.
Fig.2, the BEI micrograph of alloy #11
(Sn-42at.%Sb-38at.%Zn), exhibits three phase
regions with different brightnesses. The darkest
phase is likely to be the ZnSb phase with a Sn
solubility of approximately 3.8 at.%.. The
brightest phase is the Sn phase with a Sb
solubility of approximately 2.7 at.%. The grey
phase is likely to be ternary compoundSn30Sb25Zn45, is named A. Moreover, the XRD
analysis reconfirmed that alloy #11 has ZnSb, A,
and Sn phases. Similar result was found for the
alloy #15(Sn-45at.%Sb-35at.%Zn), which is in
the ZnSb, A, and Sn three-phase region. Fig.3 is
the
BEI
micrograph
of
alloy#16
(Sn-45at.%Sb-25at.%Zn) annealed at 150℃ for
60 days. The XRD analysis and the EPMA
results indicate that the darkest phase is the ZnSb
phase with a Sn solubility of approximately 1.4
at.%, the grey and largest phase adjacent to the
ZnSb phase is the A phase, and the brightest
phase is the SbSn phase with a Zn solubility of
approximately 0.3 at.%. Similar result was found
for the alloys #17 (Sn-45at.%Sb-15at.%Zn) and
#25(Sn-44at.%Sb-6at.%Zn), which are in the
ZnSb, A, and SbSn three-phase region. Fig. 4(a)
is the BEI micrograph of alloy #5
(Sn-30at.%Sb-40at.%Zn). The XRD analysis,
shown in Fig. 4(b), and the EPMA results
indicate that the darkest phase is the Zn4Sb3
phase and the brightest phase is the Sn phase.
Based on the experimental results of all 25
equilibrated alloys and the phase diagrams of the
constituent binary system, the isothermal section
of the Sn-Sb-Zn ternary system at 150℃ was
constructed and is shown in Fig. 5. Experimental
results indicate the existence of one ternary
compound, A, in the Sn-Sb-Zn ternary
isothermal section at 150℃. Up to about 4.5at.%
and 1.4 at.% Sn can dissolve in the Zn4Sb3 and
ZnSb phases, and the solubility of Zn in the Sn
phase is approximately 3.2at%. Each of the Sb
and SbSn phases has a limited solubility of Zn.
4. Conclusions
The isothermal section of the Sn-Sb-Zn
ternary system at 150℃ has been determined
experimentally. Some important results are
described as follows. The ternary compound
Sn30Sb25Zn45 has been confirmed. Intermetallic
compounds ε- Zn4Sb3, SbSn, ternary compound
Sn30Sb25Zn45, and Sn solid phase are in
equilibrium with the β-ZnSb phase. The
solubility ranges of solid solutions and IMCs
phases were determined. Up to about 4.5at.%
and 1.4 at.% Sn can dissolve in the ε- Zn4Sb3 and
β-ZnSb phases, and the solubility of Zn in the Sn
phase is approximately 3.2at%. Each of the Sb
and SbSn phases has a limited solubility of Zn.
Acknowledgements
The authors thank the National Science Council
of the Republic of China for financially
supporting this research under contract no. NSC
95-2221-E-011-167-MY2.
References
[1] M.E. Loomans, S. Vaynman, G. Ghosh, M.E.
Fine, Journal of Electronic Materials 23,
741(1994).
[2]W. Jang, P. G. Kim, K. N. Tu, Michael Lee,
Journal of Materials Research 14, 3895
(1999).
[3]K. Suganuma, K. Niihara, T. Shoutoku, Y.
Nakamura, Journal of Material Research 13,
2859 (1998)
[4] T. B. Massalski, Binary Alloy Phase
Diagrams. ASM Int., Materials Park, Ohio,
1990.
[5] B. Predel and W. Schwermann, J. Inst. Met.
99,169 (1971).
[6]H. Zhao, D.H.L.Ng, Z. Lu, N. Ma, Journal of
Alloys and Compounds 395,192 (2005).
Fig1. BEI micrograph of alloy #12
(Sn-42at.%Sb-48at.%Zn) annealed at 150℃ for
2000
Intensity
60 days.
1500
1000
500
0
30
40
50
60
70
80
90
Fig.4. (a) BEI micrograph of alloy #5
(Sn-30at.%Sb-40at.%Zn) annealed at 150℃ for
60 days.
0
Fig.2. BEI micrograph of alloy #11
(Sn-42at.%Sb-38at.%Zn) annealed at 150℃ for
10
100
90
20
60 days.
80
30
70
40
60
50
50
60
40
70
30
80
20
90
10
100
0
0
10
20
30
40
50
60
70
80
90
100
Fig.5. The isothermal section of the Sn-Sb-Zn
ternary system at 150 ℃
determined
experimentally.
Fig3. BEI micrograph of alloy #16
(Sn-45at.%Sb-25at.%Zn) annealed at 150℃ for
60 days.