The heats of transformation of the high-pressure orthorhombic modification of indium antimonide
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M. B. BEVER,
AND
A. K. JENA, formerly Staff Member, Divisionof Sponsored Research, M.I.T., Cambridge, Massachusetts, is now Professor, Department of MetallurgicalEngineering,Indian Institute of Technology, Kanpur, India, M. B. BEVER, is MemberAIME, Professor Emeritus and Senior Lecturer, Department of Materials Science and Engineering, M.I.T., Cambridge, Massachusetts and M. D. BANUS, formerly Staff Member, Lincoln Laboratory, M.I.T., is now Consultant in Marine Ecology, St. Thomas, U.S. Virgin Islands. Manuscript submitted July 13, 1977. METALLURGICAL TRANSACTIONS A
LIQUID
700
M. D. BANUS
The compound InSb, which at a t m o s p h e r i c p r e s s u r e is a s e m i c o n d u c t o r with the z i n c b l e n d e cubic s t r u c t u r e , has t h r e e h i g h - p r e s s u r e p o l y m o r p h i c m o d i f i c a tions, 1'2 which a r e m e t a l l i c with t r a n s i t i o n s to s u p e r conducting b e h a v i o r at v e r y low t e m p e r a t u r e s . In a p r e v i o u s p u b l i c a t i o ns we p r e s e n t e d t h e r m o d y n a m i c p r o p e r t i e s of the h i g h - p r e s s u r e p h a s e s with t e t r a g o n a l (/3-Sn) and hexagonal s y m m e t r i e s . At that t i m e , it was not p o s s i b l e to make c a l o r i m e t r i c m e a s u r e m e n t s on the phase with o r t h o r h o m b i c s y m m e t r y b e c a u s e it was difficult to p r e p a r e and r e t a i n this phase f r e e f r o m s u b s t a n t i a l a m o u n t s of one o r the other of the highp r e s s u r e p h a s e s . Subsequently, the p r e s s u r e - t e m p e r a t u r e phase d i a g r a m for InSb (Fig. 1) was worked out m o r e fully and the s t a b i l i t y r e g i o n for each phase was c l e a r l y defined. 2 In addition, the k i n e t i c s of the t r a n s f o r m a t i o n s b e t w e e n the p h a s e s a r e now b e t t e r u n d e r stood. 2 U s i n g this i n f o r m a t i o n , we p r e p a r e d s a m p l e s c o n t a i n i n g only the o r t h o r h o m b i c phase and r e t a i n e d t h e s e s a m p l e s in this f o r m for c h a r a c t e r i z a t i o n and calorimetric measurements.3 S a m p l e s of the o r t h o r h o m b i c phase, InSb(IV), w e r e p r e p a r e d and c h a r a c t e r i z e d by the t e c h n i q u e s des c r i b e d in d e t a i l p r e v i o u s l y . 1-a With the p r e s s u r e t e m p e r a t u r e p h a s e d i a g r a m s as a guide, s p e c i m e n s of InSb(IV) weighing a p p r o x i m a t e l y 0.7 g were f o r m e d by a n n e a l i n g s p e c i m e n s of cubic InSb(I) at 62 or 65 kbar and 370 to 410 K for four d a y s . The s p e c i m e n s of InSb(IV) were s t o r e d in liquid n i t r o g e n at a t m o s p h e r i c p r e s s u r e . If they were s t o r e d longer than 48 h, the c a l o r i m e t r i c data obtained with the s p e c i m e n s were e r r a t i c b e c a u s e of the p a r t i a l t r a n s f o r m a t i o n to one of the m o r e stable p h a s e s . D u r i n g the 48-h p e r i o d , the s a m p l e s were cleaved into
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