Abstract

Bismuth-telluride based (Bi_0.2Sb_0.8)_2Te_3 thermoelectric powders were fabricated by two-step planetary milling process which produces bimodal size distribution ranging 400;nm;sim;2;µm. The powders were reduced in hydrogen atmosphere to minimize oxygen contents which cause degradation of thermoelectric performance by decreasing electrical conductivity. Oxygen contents were decreased from 0.48% to 0.25% by the reduction process. In this study, both the as-synthesized and the reduced powders were consolidated by the spark plasma sintering process at 350°C for 10 min at the heating rate of 100°C/min and then their thermoelectric properties were investigated. The sintered samples using the reduced p-type thermoelectric powders show 15% lower specific electrical resistivity (0.8;mOmegacdotcm) than those of the as-synthesized powders while Seebeck coefficient and thermal conductivity do not change a lot. The results confirmed that ZT value of thermoelectric performance at room temperature was improved by 15% due to high electric conductivity caused by the controlled oxygen contents present at bismuth telluride materials.

• Keywords: Bismuth telluride;Electrical resistivity;Hydrogen reduction;ZT;