P형 열전분말의 수소환원처리가 상온열전특성에 미치는 영향

Abstract

Bismuth-telluride based (Bi0.2Sb0.8)2Te3 thermoelectric powders were fabricated by two-step planetary milling process which produces bimodal size distribution ranging 400 nm ~ 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 350oC for 10 min at the heating rate of 100oC/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 mΩ·cm) 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.