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Phase diagram of the ternary system SmCl3NaClCaCl2
therm0chimica acta ELSEVIER
Thermochimica Acta 254 (1995) 383-390
Note
Phase diagram of the ternary system SmC13-NaC1-CaC12 Y i f e n g Z h a n g *, Y u a n s h a n H a n , S h u l a n W a n g Department of Chemistry, Northeastern University, Shenyang 110006, People's Republic of China
Received 18 April 1994; accepted 21 July 1994
Abstract
The phase diagram of molten salts of the rare earth system SmCI3-NaC1-CaC12 has been investigated by DTA. For four liquidus corresponding to the primary crystallization of SmC13, NaCI, CaC12 and 2NaCI-SmCI3, five univariant lines related to the secondary crystallization, ternary eutectic point E=376°C (33.1 mol% SmC13, 46.9 mol% NaC1) and ternary peritectic point P = 389°C (29.3 tool% SmC13, 52.6 mol% NaC1) were found. Keywords: Calcium chloride; DTA; Phase diagram; Samarium chloride; Sodium chloride; Ternary system
1. Introduction
It is obvious that investigations on phase diagrams of rare earth molten salts are very important for understanding the basic physical chemistry properties of these compounds and the electrolytic production of their metals. However, there are only a few references in the literature related to this subject. As part of the series of investigations on phase diagrams of molten salts of rare earth chloride systems, we have determined the phase diagram of the ternary system SmC13-NaCI-CaCI2 by DTA, which has not previously been reported in the literature.
* Corresponding author. 0040-6031/95/$09.50 © 1995 - Elsevier Science B.V. All rights reserved SSDI 0040-6031(94) 02030-2
384
Y.F. Zhang et al./Thermochimica Acta 254 (1995) 383-390
2. Experimental methods 2.1. The anhydrous salts
NaC1 (A.R.) and CaCl2 (A.R.) were prepared and sufficiently dehydrated. The melting temperature of NaC1 is 800°C and that of CaC12 is 775°C. Sm203 (99.9 wt%) was chlorinated with HCI (A.R.), and the resulting SmCI3 • 6H20 placed in a drying vessel in P205 and dehydrated for the first time. It was then vacuum heated in dry HC1 and sufficiently dehydrated step by step [ 1]. The melting temperature of SmCI 3 is 676°C. 2.2. Preparation o f samples
The operation was conducted in a P205 drying box. Samples of about 150 mg were placed in silica ampoules and accurately weighed on a balance. The ampoules were sealed under vacuum, and the samples were melted and thoroughly shaken, and annealed for 12 h at 400°C. 2.3. DTA
The sample tube has a hole at the bottom in which a N i C r - N i S i thermocouple was placed. The DTA apparatus was calibrated by standard substances with known
SmCll
I
NaC!
I
tool %
CaCl,
Fig. I. Distribution of six sections on the composition triangle.
Y.F. Zhang et al./Thermochimica Acta 254 (1995) 383-390
385
TOO
(,.3 o
ou o=
L
s.oo
\
E
\~
/
-,+,
,lO0
['~;a.+M-gl.-
~+C.a,+M[ I
300
sma,+M+~a,
/
20
I
I
40
60
8~)
SmCI,
mot% Fig. 2. Section 1.
//
700
¢..)
101
•
o
._c
~. SO0 •. % \
/
sma,+L
E %
~
~ j+L
x
.,.
-.+ ~.' /
400 389:,,
~
n•
-I-M. , 320 0 '"
:
20
:30
=o,+~.o,+,. , ,o
376
SmCI,+Mac-CaLQ,
mol%
6'o
Fig. 3. Section II.
io
s.,o,
Y.F. Zhang et al./Thermochimica Acta 254 (1995) 383 390
386
700
|OG U
o
._c
SO(
•
~
:
o-o.-$00
~
E
40( '
._ !~O+
300
/ 3
1
1
~
:
,"--'--
376-
IC~.+M+I.
20
40
0
~CI,
80
Sm~,
rnol%
Fig. 4. Section III.
700
L
601
U o
500,
I::
400
30( 0
20
40
60 tool %
Fig. 5. Section IV.
Y.F. Zhang et al./Thermochimica Acta 254 (1995) 383 390
U o
L
)
o
SmCI,-4-1.4 ~-
I £=C1,"11~4+L
C.a~,
N~O'+ CaO,-t P,~
3¢C
20
40
60
80
~aC'l
tool% Fig. 6. Section V.
700
600
0
o
.__
~
CaCIm't- L SO0
E ."l+CaQ, + L 400 NaCI+M+L +CaCim+M 300
20
40
60
tool% Fig. 7. Section VI.
80
CaClm
387
388
Y.F. Zhang et al./Thermochimica Acta 254 (1995) 383 390
phase change t e m p e r a t u r e s ( c a l i b r a t i n g the heating a n d cooling curves at the same time). The h e a t i n g rate was 10 K min -~. A120 3 was used as reference substance. The t e m p e r a t u r e e r r o r was _+ 3°C. The liquidus t e m p e r a t u r e was d e t e r m i n e d with the aid o f the cooling curve; o t h e r t e m p e r a t u r e s were d e t e r m i n e d using the e x t e n d e d initial t e m p e r a t u r e o f the p e a k s f r o m the h e a t i n g curve.
3. Results 3.1. Studies on related phase diagrams o f binary systems
The related phase d i a g r a m s o f the b i n a r y systems SmC13-NaC1, N a C 1 - C a C 1 2 a n d SmC13-CaC12 were r e p o r t e d in Refs. [2]-[4]. Before d e t e r m i n i n g the t e r n a r y phase d i a g r a m , we studied the literature on phase d i a g r a m s o f the a b o v e two b i n a r y systems. T h e results for SmC13-NaC1 are different f r o m those in Ref. [2] for i n v a r i a n t temperatures. In the former, e~ = 410°C (50.0 m o l % NaC1) a n d p = 435°C (61.0 m o l % NaC1), whereas in Ref. [2] e~ = 390°C a n d p = 4 2 5 ° C . Hence the i n v a r i a n t t e m p e r a t u r e s are higher t h a n the values cited in the literature. Firstly, the reason m a y be the m o r e effective d e h y d r a t i o n (e.g. the melting p o i n t o f SmC13 in Ref. [2] is 665°C a n d in this p a p e r is 676°C); secondly, p e r h a p s it is due to the strictly sealed c o n d i t i o n s o f the whole e x p e r i m e n t a l process. The result for N a C 1 CaC12 is the same as in Ref. [3], being o f a simple eutectic type, i.e. e 2 :- 500°C (51.0 m o l % CaC12). SmC13-CaC12 is also a simple eutectic system, for which e 3 = 545°C (55.8 m o l % SmC13).
Table 1 Compositions and temperatures of deflection points on the liquidus Section
Mol%
Temperature in °C
Mol%
Temperature in °C
I
CaCI2 NaCI
22.3 77.7
SmCI3
31.5
401
38.5
399
II
CaC12 NaCI
38.2 61.8
SmC13
21.0
436
38.0
430
III
CaC12 NaCI
57.7 42.3
SmC13
46.5
500
IV
CaCI2 NaCI
78.2 21.8
SmC13
52.0
525
V
CaCI2 SmC13
68.7 31.3
NaCI
48.0
455
VI
NaCI SmCI3
72.8 27.2
CaCI2
34.5
448
Y.F. Zhang et al./Thermoehimica Acta 254 (1995) 383-390
NaQ
e,
389
CaCl~
rnol% Fig. 8. Phase d i a g r a m of SmCl 3 NaC1 CaCI 2.
3.2. Construction of the phase diagram of the SmCl3-NaCl-CaCl2 system Six vertical sections were determined, and their distribution in the composition triangle is shown in Fig. 1. The vertical sections I-VI are shown in Figs. 2-7. In these Figures L represents the liquid phase, and M represents the incongruent compound 2NaC1. SmCI3. The compositions and temperatures of deflection points on the liquidus at various vertical sections are shown in Table 1. The compositions and temperatures of the deflection points on the liquidus at the six vertical sections in Table 1 are orthogonally projected onto the base triangle. When they are connected, they form secondary crystallization lines. Extending and intersecting, and according to the calorific effect of equilibrium reactions with four phases under liquidus, we determine the ternary eutectic point E = 376°C (33.1 mol% SmC13, 46.9 mol% NaC1) and the ternary peritectic point P = 389°C (29.3 mol% SmC13, 52.6 mol% NaC1). The phase diagram of the ternary system is given in Fig. 8.
390
Y.F. Zhang et al./Thermochimica Acta 254 (1995) 383 390
References [1] [2] [3] [4]
Su Mianzeng, Chem. Bull., 4 (1979) 22 (in Chinese). B.G. Korshunov, Zh. Neorgan. Khim., 9 (1964) 1427. Li Ruiqing and Qiao Zhiyu, J. Univ. Sci. Technol. Beijing, 9 (1987) 114. Zhang Yifeng, Acta Metall. Sin. 27 (1991) B438.
Thermochimica Acta 254 (1995) 383-390
Note
Phase diagram of the ternary system SmC13-NaC1-CaC12 Y i f e n g Z h a n g *, Y u a n s h a n H a n , S h u l a n W a n g Department of Chemistry, Northeastern University, Shenyang 110006, People's Republic of China
Received 18 April 1994; accepted 21 July 1994
Abstract
The phase diagram of molten salts of the rare earth system SmCI3-NaC1-CaC12 has been investigated by DTA. For four liquidus corresponding to the primary crystallization of SmC13, NaCI, CaC12 and 2NaCI-SmCI3, five univariant lines related to the secondary crystallization, ternary eutectic point E=376°C (33.1 mol% SmC13, 46.9 mol% NaC1) and ternary peritectic point P = 389°C (29.3 tool% SmC13, 52.6 mol% NaC1) were found. Keywords: Calcium chloride; DTA; Phase diagram; Samarium chloride; Sodium chloride; Ternary system
1. Introduction
It is obvious that investigations on phase diagrams of rare earth molten salts are very important for understanding the basic physical chemistry properties of these compounds and the electrolytic production of their metals. However, there are only a few references in the literature related to this subject. As part of the series of investigations on phase diagrams of molten salts of rare earth chloride systems, we have determined the phase diagram of the ternary system SmC13-NaCI-CaCI2 by DTA, which has not previously been reported in the literature.
* Corresponding author. 0040-6031/95/$09.50 © 1995 - Elsevier Science B.V. All rights reserved SSDI 0040-6031(94) 02030-2
384
Y.F. Zhang et al./Thermochimica Acta 254 (1995) 383-390
2. Experimental methods 2.1. The anhydrous salts
NaC1 (A.R.) and CaCl2 (A.R.) were prepared and sufficiently dehydrated. The melting temperature of NaC1 is 800°C and that of CaC12 is 775°C. Sm203 (99.9 wt%) was chlorinated with HCI (A.R.), and the resulting SmCI3 • 6H20 placed in a drying vessel in P205 and dehydrated for the first time. It was then vacuum heated in dry HC1 and sufficiently dehydrated step by step [ 1]. The melting temperature of SmCI 3 is 676°C. 2.2. Preparation o f samples
The operation was conducted in a P205 drying box. Samples of about 150 mg were placed in silica ampoules and accurately weighed on a balance. The ampoules were sealed under vacuum, and the samples were melted and thoroughly shaken, and annealed for 12 h at 400°C. 2.3. DTA
The sample tube has a hole at the bottom in which a N i C r - N i S i thermocouple was placed. The DTA apparatus was calibrated by standard substances with known
SmCll
I
NaC!
I
tool %
CaCl,
Fig. I. Distribution of six sections on the composition triangle.
Y.F. Zhang et al./Thermochimica Acta 254 (1995) 383-390
385
TOO
(,.3 o
ou o=
L
s.oo
\
E
\~
/
-,+,
,lO0
['~;a.+M-gl.-
~+C.a,+M[ I
300
sma,+M+~a,
/
20
I
I
40
60
8~)
SmCI,
mot% Fig. 2. Section 1.
//
700
¢..)
101
•
o
._c
~. SO0 •. % \
/
sma,+L
E %
~
~ j+L
x
.,.
-.+ ~.' /
400 389:,,
~
n•
-I-M. , 320 0 '"
:
20
:30
=o,+~.o,+,. , ,o
376
SmCI,+Mac-CaLQ,
mol%
6'o
Fig. 3. Section II.
io
s.,o,
Y.F. Zhang et al./Thermochimica Acta 254 (1995) 383 390
386
700
|OG U
o
._c
SO(
•
~
:
o-o.-$00
~
E
40( '
._ !~O+
300
/ 3
1
1
~
:
,"--'--
376-
IC~.+M+I.
20
40
0
~CI,
80
Sm~,
rnol%
Fig. 4. Section III.
700
L
601
U o
500,
I::
400
30( 0
20
40
60 tool %
Fig. 5. Section IV.
Y.F. Zhang et al./Thermochimica Acta 254 (1995) 383 390
U o
L
)
o
SmCI,-4-1.4 ~-
I £=C1,"11~4+L
C.a~,
N~O'+ CaO,-t P,~
3¢C
20
40
60
80
~aC'l
tool% Fig. 6. Section V.
700
600
0
o
.__
~
CaCIm't- L SO0
E ."l+CaQ, + L 400 NaCI+M+L +CaCim+M 300
20
40
60
tool% Fig. 7. Section VI.
80
CaClm
387
388
Y.F. Zhang et al./Thermochimica Acta 254 (1995) 383 390
phase change t e m p e r a t u r e s ( c a l i b r a t i n g the heating a n d cooling curves at the same time). The h e a t i n g rate was 10 K min -~. A120 3 was used as reference substance. The t e m p e r a t u r e e r r o r was _+ 3°C. The liquidus t e m p e r a t u r e was d e t e r m i n e d with the aid o f the cooling curve; o t h e r t e m p e r a t u r e s were d e t e r m i n e d using the e x t e n d e d initial t e m p e r a t u r e o f the p e a k s f r o m the h e a t i n g curve.
3. Results 3.1. Studies on related phase diagrams o f binary systems
The related phase d i a g r a m s o f the b i n a r y systems SmC13-NaC1, N a C 1 - C a C 1 2 a n d SmC13-CaC12 were r e p o r t e d in Refs. [2]-[4]. Before d e t e r m i n i n g the t e r n a r y phase d i a g r a m , we studied the literature on phase d i a g r a m s o f the a b o v e two b i n a r y systems. T h e results for SmC13-NaC1 are different f r o m those in Ref. [2] for i n v a r i a n t temperatures. In the former, e~ = 410°C (50.0 m o l % NaC1) a n d p = 435°C (61.0 m o l % NaC1), whereas in Ref. [2] e~ = 390°C a n d p = 4 2 5 ° C . Hence the i n v a r i a n t t e m p e r a t u r e s are higher t h a n the values cited in the literature. Firstly, the reason m a y be the m o r e effective d e h y d r a t i o n (e.g. the melting p o i n t o f SmC13 in Ref. [2] is 665°C a n d in this p a p e r is 676°C); secondly, p e r h a p s it is due to the strictly sealed c o n d i t i o n s o f the whole e x p e r i m e n t a l process. The result for N a C 1 CaC12 is the same as in Ref. [3], being o f a simple eutectic type, i.e. e 2 :- 500°C (51.0 m o l % CaC12). SmC13-CaC12 is also a simple eutectic system, for which e 3 = 545°C (55.8 m o l % SmC13).
Table 1 Compositions and temperatures of deflection points on the liquidus Section
Mol%
Temperature in °C
Mol%
Temperature in °C
I
CaCI2 NaCI
22.3 77.7
SmCI3
31.5
401
38.5
399
II
CaC12 NaCI
38.2 61.8
SmC13
21.0
436
38.0
430
III
CaC12 NaCI
57.7 42.3
SmC13
46.5
500
IV
CaCI2 NaCI
78.2 21.8
SmC13
52.0
525
V
CaCI2 SmC13
68.7 31.3
NaCI
48.0
455
VI
NaCI SmCI3
72.8 27.2
CaCI2
34.5
448
Y.F. Zhang et al./Thermoehimica Acta 254 (1995) 383-390
NaQ
e,
389
CaCl~
rnol% Fig. 8. Phase d i a g r a m of SmCl 3 NaC1 CaCI 2.
3.2. Construction of the phase diagram of the SmCl3-NaCl-CaCl2 system Six vertical sections were determined, and their distribution in the composition triangle is shown in Fig. 1. The vertical sections I-VI are shown in Figs. 2-7. In these Figures L represents the liquid phase, and M represents the incongruent compound 2NaC1. SmCI3. The compositions and temperatures of deflection points on the liquidus at various vertical sections are shown in Table 1. The compositions and temperatures of the deflection points on the liquidus at the six vertical sections in Table 1 are orthogonally projected onto the base triangle. When they are connected, they form secondary crystallization lines. Extending and intersecting, and according to the calorific effect of equilibrium reactions with four phases under liquidus, we determine the ternary eutectic point E = 376°C (33.1 mol% SmC13, 46.9 mol% NaC1) and the ternary peritectic point P = 389°C (29.3 mol% SmC13, 52.6 mol% NaC1). The phase diagram of the ternary system is given in Fig. 8.
390
Y.F. Zhang et al./Thermochimica Acta 254 (1995) 383 390
References [1] [2] [3] [4]
Su Mianzeng, Chem. Bull., 4 (1979) 22 (in Chinese). B.G. Korshunov, Zh. Neorgan. Khim., 9 (1964) 1427. Li Ruiqing and Qiao Zhiyu, J. Univ. Sci. Technol. Beijing, 9 (1987) 114. Zhang Yifeng, Acta Metall. Sin. 27 (1991) B438.