Thermoelectric properties of dilute PbTe-GeTe alloys
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[1] Seebeck c o e f f i c i e n t , p is t h e e l e c t r i c a l k is t h e t h e r m a l c o n d u c t i v i t y . T h e e x p r e s s e d i n t e r m s o f the m o r e f u n d a parameters:
Z am *3J2P/kL
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IRWIN KUDMAN is a Member of the Technical Staff, RCA Laboratories, Princeton,N. J. Manuscript submitted June 2 4 , 1970. METALLURGICAL TRANSA('TIONS
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20
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40 50 60 70 MOLE % PbSe
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F i g . 1--The r o o m t e m p e r a t u r e mobility and t h e r m a l conduct i v i t y of P b T e - P b S e a l l o y s as a function of c o m p o s i t i o n . VOLUME 2 , JANUARY 1 9 7 1 - 1 6 3
[2] r e m a i n s u n c h a n g e d i n the r e g i o n o f t h e t h e r m a l c o n d u c t i v i t y m i n i m u m . It w o u l d be e x p e c t e d , t h e r e f o r e , that n o i m p r o v e m e n t in t h e r o o m t e m p e r a t u r e f i g u r e o f m e r it w o u l d r e s u l t f r o m a l l o y i n g P b S e w i t h P b T e , a n d i n d e e d , t h i s c o n c l u s i o n h a s b e e n r e p o r t e d i n the l i t e r a t u r e .2 It i s o b v i o u s that f u r t h e r i m p r o v e m e n t s i n t h e f i g u r e o f m e r i t o f a P b T e - b a s e a l l o y o v e r that of P b T e c a n o n l y o c c u r i f t h e t h e r m a l c o n d u c t i v i t y i s r e d u c e d by a s i g n i f i c a n t f a c t o r f o r a l l o y c o m p o s i t i o n s in w h i c h t h e r e i s l i t t l e d e g r a d a t i o n of the c a r r i e r m o b i l i t y . C l e a r l y , i f the m i n i m u m t h e r m a l c o n d u c t i v i t y s h o w n in F i g . 1 c o u l d , by s o m e m e a n s , be s h i f t e d t o w a r d s P b T e - r i c h ( d i l u t e ) a l l o y s , a l a r g e a n d b e n e f i c i a l i n c r e a s e in t h e r a t i o (~/kL) w o u l d r e s u l t . It m i g h t be a n t i c i p a t e d , b a s e d o n t h e c o m p o s i t i o n d e p e n d e n c e of t h e t h e r m a l c o n d u c t i v i t y a n d e l e c t r o n m o b i l i t y shown in Fig. 1, t h a t a s h i f t i n t h e t h e r m a l c o n d u c t i v i t y m i n i m u m w o u l d be a c c o m p a n i e d by a s i m u l t a n e o u s s h i f t i n t h e m i n i m u m m o b i l i t y to t h e s a m e c o m p o s i t i o n . W h i l e t h i s is true f o r t h e P b T e - P b S e s y s t e m i t m u s t be c o n s i d e r e d f o r tuitous s i n c e the scattering of p h o n o n s and c u r r e n t c a r r i e r s do not d e p e n d on l o c a l i z e d s t r a i n s t o t h e s a m e e x t e n t . In t h e c a s e o f t h e I I I - V a l l o y s y s t e m s i t h a s been shown b o t h theoretically 4 a n d experimentally 5 that a l l o y s c a t t e r i n g o f c u r r e n t c a r r i e r s d o e s not l i m i t t h e m o b i l i t y in t h e s e m a t e r i a l s . What i s r e q u i r e d i s a basi s f o r the s e l e c t i o n of a n a l l o y s y s t e m w h i c h w o u l d r e sult in a l a r g e r e d u c t i o n in t h e l a t t i c e t h e r m a l c o n d u c t
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