Temperature dependence of the figure-of-merit of Ag/sub 0.208/Sb/sub 0.275/Te/sub 0.517/

The p-type Ag/sub 0.208/Sb/sub 0.275/Te/sub 0.517/ boule was unidirectionally grown using a Bridgman furnace and subsequently rapidly cooled by Ar to form a Widmannstatten structure of a high temperature phase AgSbTe/sub 2/, which could be desirable for power generation. Though the boule looked a homogeneous Widmannstatten structure, XRD patterns revealed that some precipitates of Ag/sub 2/Te and Sb/sub 2/Te/sub 3/ were contained in the boule and increased in volume in the growth direction. The figure-of-merit Z of the p-type Ag/sub 0.208/Sb/sub 0.275/Te/sub 0.517/ boule have been evaluated in the temperature range from 300 to 700 K. The maximum figure-of-merit Z/sub max/ was different in the portions of the boule. The value of 2.0/spl times/10/sup -1//K was at 620 K for the former half portion of the boule and that of 1.7/spl times/10/sup -3//K was at 585 K for the latter half portion. The Ag/sub 0.208/Sb/sub 0.275/Te/sub 0.517/ boule with less precipitates showed higher Z at higher temperatures.