Improved Thermoelectric Properties in Structure Controlled Ag-Sb-Te System

The p-type Ag0.208Sb0.275Te0.517 boule was unidirectionally grown using a Bridgman furnace and, it was subsequently cooled rapidly by an Ar flush to form a high temperature phase AgSbTe2, which could be desirable for power generation. Though the boule looked a homogeneous Widmannstatten structure of the AgSbTe2 phase, XRD patterns revealed that some precipitates of Ag2Te and Sb2Te3 were contained in the boule and increased in volume in the growth direction. The relationship between the transformation and the thermoelectric properties was investigated. Figure-of-merit Z of the p-type Ag0.208Sb0.275Te0.517 boule has been evaluated in the temperature range from 300 to 700 K. The maximum figure-of-merit Zmax was different in the portions of the boule. The value of 2.0×10-3 /K was for the former half portion of the boule at 620 K and that of 1.7×10-3 /K was for the latter half portion at 585 K . The Ag0.208Sb0.275Te0.517 boule with less precipitates showed a higher Z at higher temperatures. Possibility of improving thermoelectric properties in Ag-Sb-Te system was pointed out.