ICT2014 Abstracts

In our experiment, the ternary AgSbTe₂ alloys of high performance thermoelectric materials at medium temperature are fabricated by a synthesis process of melt, pulverization, and spark plasma sintering (SPS). The thermoelectric effect in AgSbTe_1.97Se_0.03 compounds prepared by ball milling and different sinter atmosphere conditions is studied. From the analyses of crystalline phases and differential scanning calorimetry, Se-doped AgSbTe₂-based sample can suppress the appearance of Ag₂Te and Ag₅Te crystalline phases. Therefore, in addition to main phase AgSbTe₂, AgSbTe_1.97Se_0.03 sample coexist a few amount of cubic Ag₂Te. For these measurements of thermoelectric properties, the electron conductivity of the AgSbTe_1.97Se_0.03 sample prepared by SPS under argon atmosphere condition is slightly enhanced and the Seebeck coefficient does not change. At the same time, the thermal conductivity of the AgSbTe_1.97Se_0.03 sample prepared by SPS under argon atmosphere significantly decreases. This seems to be the existence of nanoscale precipitates of second phase and the increase of carrier concentration caused by heat trace of plasma between grain interfaces, resulting in the decrease of the thermal conductivity and the optimization of the thermoelectric effect. For the stoichiometric composition of AgSbTe_1.97Se_0.03, the thermal conductivity is very low as 0.4~0.5 W/mK by combining ball milling and sinter under argon atmosphere condition technology. Finally, the deduced figure of merit ZT reaches 1.25 at 243 ^oC.