Thermoelectric Properties of the Pseudobinary Alloy (Ag0.365Sb0.558Te)0.975(GeTe)0.025 Prepared by Spark Plasma Sintering

Abstract

Ag-Sb-Te-Ge-based alloys have received great attention in recent years. In the present work we prepared the pseudobinary alloy (Ag 0.365 Sb 0.558 Te) 0.975 (GeTe) 0.025 using spark plasma sintering and evaluated its thermoelectric (TE) properties over the temperature range from 318 K to 551 K. Rietveld analysis revealed that about 1.3 at.% Ge atoms occupy the Sb sites and that the alloy exhibits the same crystal structure as AgSbTe 2 . By using back-scattered electron imaging, we observed two instead of one phase in the sample. The small white AgSbTe 2 chunks embedded in the matrix can substantially scatter phonons. Compared with the transport properties of Ag 0.365 Sb 0.558 Te, we obtained a slightly increased Seebeck coefficient and reduced thermal conductivity without sacrificing electrical conductivity. The highest TE figure of merit, ZT, was 0.69 at 551 K, whereas that of the ternary alloy Ag 0.365 Sb 0.558 Te was 0.61 at the corresponding temperature, suggesting that (Ag 0.365 Sb 0.558 Te) 0.975 (GeTe) 0.025 has the potential to improve TE performance with optimization of its chemical composition.