Temperature dependence of the figure-of-merit of Ag0.208Sb0.275Te0.517

The p-type Ag_0.208Sb_0.275Te_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 AgSbTe₂, which could be desirable for power generation. Though the boule looked a homogeneous Widmannstatten structure, XRD patterns revealed that some precipitates of Ag₂Te and Sb₂Te₃ were contained in the boule and increased in volume in the growth direction. The figure-of-merit Z of the p-type Ag_0.208Sb_0.275Te_0.517 boule have been evaluated in the temperature range from 300 to 700 K. The maximum figure-of-merit Z_max was different in the portions of the boule. The value of 2.0×10^-1/K was at 620 K for the former half portion of the boule and that of 1.7×10^-3/K was at 585 K for the latter half portion. The Ag_0.208Sb_0.275Te_0.517 boule with less precipitates showed higher Z at higher temperatures.