The isothermal section of the Pr-Ti-Si ternary system at 773 K

Article abstract of DOI:10.1016/j.jallcom.2008.12.145

The isothermal section of the Pr-Ti-Si ternary phase diagram at 773 K was investigated by powder X-ray diffraction (XRD) and differential thermal analysis (DTA). The binary compound Pr₃Si₄ is not observed at 773 K. There are nine bin

Full text of DOI:10.1016/j.jallcom.2008.12.145

Journal of Alloys and Compounds 479 (2009) 201–203
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Journal of Alloys and Compounds
journal homepage: www.elsevier.com/locate/jallcom
The isothermal section of the Pr–Ti–Si ternary system at 773 K
Yongzhong Zhana,∗, Chunhui Lia, Jingqi Liua, Yong Dub, Honglou Moa
a Key Laboratory of Nonferrous Metal Materials and New Processing Technology, Ministry of Education, Guangxi University, Nanning, Guangxi 530004, PR China
b State Key Laboratory of Powder Metallurgy, Central South University, Changsha, Hunan 410083, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
The isothermal section of the Pr–Ti–Si ternary phase diagram at 773 K was investigated by powder X-ray
diffraction (XRD) and differential thermal analysis (DTA). The binary compound Pr3Si4 is not observed at
773 K. There are nine binary compounds in this system, which are Ti3Si, Ti5Si3, Ti5Si4, TiSi, TiSi2, Pr5Si3,
Pr5Si4, PrSi and PrSi2. No ternary compounds were found in this work. The 773 K isothermal section of
this ternary system consists of 12 single-phase regions, 21 two-phase regions and 10 three-phase regions.
The compound Ti5Si3 has a homogeneity range extending from about 37 to 38 at.% Si. The existence of
solid solubility of the other phases was not observed.
Received 4 December 2008
Received in revised form 20 December 2008
Accepted 28 December 2008
Available online 10 January 2009
Keywords:
Metals and alloys
Phase diagrams
X-ray diffraction
© 2009 Elsevier B.V. All rights reserved.
1. Introduction
electrode in high-pure argon atmosphere. The alloys were re-melted three times
and turned around after melting for better homogeneity. For most alloys, the weight
loss is less than 1% after melting.
An investigation of the Pr–Ti–Si ternary system is a part of a
systematical study of the interaction of metals with titanium and
silicon. Recently, we reported the phase equilibria of the La–Ti–Si
[1], Zr–Ti–Si [2], Nb–Ti–Si [3] and Gd–Ti–Si [4] systems by means
of experimental methods.
Ti–Si binary phase diagram [5] shows five intermediate phases,
i.e. Ti3Si, Ti5Si3, Ti5Si4, TiSi and TiSi2 with high-melting points and
tight homogeneity ranges. Morozkin [6] did not confirm that Ti5Si4
existed in the Dy–Ti–Si system at 1200 K. Pr–Si system has also been
reported [7]. In Refs. [8–11], the intermetallic compound informa-
tion of the crystal structure and crystallography in Pr–Si binary
system was reported. The compounds existing in this system are
Pr5Si3, Pr5Si4, PrSi, and PrSi2. No intermetallic phase was found
in Pr–Ti binary system. Structural data for the intermetallic com-
pounds in the three binary systems are given in Table 1.
Several typical ternary alloys with compositions that represent different parts of
the isothermal section were examined through differential thermal analysis (DTA) to
obtain the melting point. The homogenization temperature of the alloys were chosen
on the basis of the binary phase diagrams of the Ti–Si, Ti–Pr and Pr–Si systems as well
as the results of DTA. Then the samples were kept sealed in silica tubes in vacuum
during homogenization. The alloys were homogenized at 1023 K for 480 h at first
and then they were cooled down to 773 K and kept at this temperature for 240 h.
Finally, all these annealed alloys were quenched in liquid nitrogen.
The quenched samples were pulverized, sealed in evacuated glass tube and
annealed at 773 K for 4 days, followed by quenched into liquid nitrogen before X-
ray diffraction (XRD) experiment. The XRD analysis was performed using a Rigaku
D/Max 2500 V diffractometer with Cu K␣ radiation, graphite monochromator, a volt-
age of 40 kV and a current of 200 mA. The materials data were analyzed by using
JADE 5.0 software [13] and PCW (Powder Cell Windows software) [14]. A Powder
Diffraction File (PDF release 2002) was used to determine the phase existence in
each sample. DTA experiment was performed using a differential thermal analyzer
(PerkinElmer). The samples were heated or cooled at a rate of 20 K/min during DTA.
Up to now, no report on the isothermal section of the ternary
Pr–Ti–Si system has been found. This study was carried out to con-
struct the isothermal section of the Pr–Ti–Si phase diagram at 773 K,
so as to establish the phase relationship and formation of the solid
solutions in this system.
3. Results and discussion
3.1. Intermetallic compounds
In this work, five binary compounds, i.e. Ti3Si, Ti5Si3, Ti5Si4, TiSi
and TiSi2 have been confirmed in the Ti–Si binary system at 773 K.
In the Pr–Ti binary system, no binary compounds were observed.
The results obtained agree well with Ref. [5]. In the Pr–Si binary
system, there are five binary compounds, i.e. Pr5Si3, Pr5Si4, PrSi,
Pr3Si4 and PrSi2 reported [7–11]. However, Pr3Si4 has not been
observed at 773 K in this work, which agrees well with the results
of Liu et al. [15]. In Fig. 1, the XRD pattern of the equilibrated binary
alloy containing 42.86 at.% Pr and 57.14 at.% Si (Pr:Si = 3:4) indicates
2. Experimental details
The purities of praseodymium, silicon and titanium used in this work are 99.58%,
99.99% and 99.99%, respectively. The alloys (each weighing 1.5 g) were prepared by
arc-melting on a water-cooled copper crucible with a non-consumable tungsten
∗
Corresponding author. Tel.: +86 771 3272311; fax: +86 771 3233530.
E-mail address: zyzmatres@yahoo.com.cn (Y. Zhan).
0925-8388/$ – see front matter © 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.jallcom.2008.12.145

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Y. Zhan et al. / Journal of Alloys and Compounds 479 (2009) 201–203
Table 1
Binary crystal structure data in the Pr–Ti–Si system.
Compound
Space group
Lattice parameters (nm)
Reference
a
b
c
Pr5Si3
Pr5Si4
PrSi
I4/mcm
P41212
Pnma
I41/amd
P42/n
0.7814(5)
0.790
0.8240
0.4205(5)
1.0196
0.8236(6)
0.361
0.74610(3)
0.7133
0.657
–
1.374(2)
1.491
[12]
[12]
[12]
[12]
[6]
[6]
[6]
[6]
[6]
0.3941
–
–
0.4773(4)
1.377
–
0.5920
1.373(2)
0.5097
0.8523(6)
0.365
0.51508(1)
1.2977
0.503
PrSi2
Ti3Si
a
TiSi2
TiSi2
Fddd
b
Cmcm
P63/mcm
P41212
Pnma
Ti5Si3
Ti5Si4
TiSia
–
0.364
0.6492
[6]
[6]
TiSib
Pmm2
0.3618
0.4973
Fig. 1. XRD pattern of the equilibrated alloy (42.86 at.% Pr and 57.14 at.% Si) indicating
the existence of PrSi2 and PrSi.
Fig. 3. XRD pattern of the equilibrated alloy (14 at.% Pr, 30 at.% Ti and 56 at.% Si)
indicating the existence of Ti5Si4, TiSi and PrSi2.
the existence of PrSi2 and PrSi. Moreover, from the XRD analysis
result of the equilibrated sample containing 36 at.% Pr, 14 at.% Ti
and 50 at.% Si, it is clear that it consists of three phases, i.e. Ti5Si3,
PrSi2 and PrSi (as shown in Fig. 2). Both the above results indicate
the nonexistence of Pr3Si4 phase in the Pr–Si system at 773 K.
In the previous works, no ternary compounds have been
reported in this system. It is confirmed in this work that there was
no ternary compound exists in the Pr–Ti–Si ternary system at 773 K.
sample containing 14 at.% Pr, 30 at.% Ti and 56 at.% Si consists of pat-
terns of three phases, i.e. Ti5Si3, PrSi2 and PrSi. Fig. 4 clearly shows
that the equilibrated sample containing 12 at.% Pr, 28 at.% Ti and
60 at.% Si located in the three-phase region of TiSi2, TiSi and PrSi2.
In Fig. 5, the XRD pattern of the equilibrated samples containing
14 at.% Pr, 46 at.% Ti and 40 at.% Si clearly indicates the existence of
the three phases, i.e. Ti5Si3, PrSi and Pr5Si4.
The range of solid solubility for each phase at 773 K has been
determined by XRD using the phase-disappearing method [16] and
comparing the shift of the XRD pattern of the samples near the com-
3.2. Isothermal section
positions of the binary phases. Three equilibrated samples (Ti62Si38
,
One hundred and fifty-two equilibrated samples have been pre-
pared and analyzed to make clear the phase compositions. It is
shown in Fig. 3 an example that the XRD pattern of the equilibrated
Ti62.5Si37.5 and Ti63Si37) have been analyzed by XRD, the results
show that they all have only one phase with Mn5Si3 structure. It is
obvious that they all belong to the extended region of Mn5Si3-type
Fig. 2. XRD pattern of the equilibrated alloy (36 at.% Pr, 14 at.% Ti and 50 at.% Si)
Fig. 4. XRD pattern of the equilibrated alloy (12 at.% Pr, 28 at.% Ti and 60 at.% Si)
indicating the existence of Ti5Si3, PrSi2 and PrSi.
indicating the existence of TiSi2, TiSi and PrSi2.

Y. Zhan et al. / Journal of Alloys and Compounds 479 (2009) 201–203
203
Table 2
The lattice parameters of the alloys in the solid solution region of Ti5Si3.
Alloys
Space group
Lattice parameters (nm)
a
b
c
Ti63Si37
Ti62.5Si37.5
Ti62Si38
P63/mcm
P63/mcm
P63/mcm
0.74389(9)
0.74597(5)
0.74532(6)
–
–
–
0.51343(7)
0.51541(4)
0.51486(5)
Ti3Si or Ti5Si4 was detected when Si content is lower than 37 at.% or
higher than 38 at.%, respectively. Therefore, the above results show
that the compound Ti5Si3 has a homogeneity range extending from
about 37 to 38 at.% Si. The existence of solid solubility of the other
phase was not observed.
Fig. 5. XRD pattern of the equilibrated alloy (14 at.% Pr, 46 at.% Ti and 40 at.% Si)
indicating the existence of Ti5Si3, PrSi and Pr5Si4.
Based on the experimental results, the phase relation of the
ternary Pr–Ti–Si system at 773 K was determined. The isothermal
section is shown in Fig. 7.
4. Conclusion
The phase equilibria of the ternary Pr–Ti–Si system at 773 K have
been determined. The existence of the binary compound Ti5Si4 was
confirmed. It is confirmed in this work that the binary compound
Pr3Si4 does not exist in the Pr–Si binary system at 773 K. No ternary
compound is found in the ternary system. The isothermal section
consists of 12 single-phase regions, 21 two-phase regions and 10
three-phase regions. The compound Ti5Si3 has a homogeneity range
extending from about 37 to 38 at.% Si. Solid solubility of the other
phases was not detected.
Fig. 6. The XRD patterns of some equilibrated Pr–Ti–Si ternary system samples: (a)
62 at.% Ti and 38 at.% Si; (b) 62.5 at.% Ti and 37.5 at.% Si%; and (c) 63 at.% Ti and 37 at.%
Si.
Acknowledgements
The authors wish to express thanks to the financial support
from the National Natural Science Foundation of China (50761003,
50831007), the Key Project of China Ministry of Education (207085)
and the Opening Foundation of State Key Laboratory of Powder
Metallurgy.
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Fig. 7. The isothermal section of phase diagram of Pr–Ti–Si ternary system at 773 K.
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Ti5Si3-based solid solution (shown in Fig. 6). The lattice parameters
of the three alloys in the solid solution region of Ti5Si3 are listed in
Table 2. However, another phase can be found in the samples when
the chemical composition exceeds the range of 37–38 at.% Si, i.e.