Power factor enhancement in a composite based on the half-Heusler antimonide TmNiSb

Abstract

Electrical transport studies of half-Heusler (HH)-based composites (TmNiSb)1−x(TmNiSn)x were carried out in a wide temperature range aimed at searching for possible enhancement in the thermoelectric power factor (PF) over that observed in the parent compound TmNiSb. The best thermoelectric performance was found in the sample with x = 0.25, which showed PF = 1.3 × 10−3 W/mK at 1000 K, i.e., about 70% larger than PF of TmNiSb at the same temperature. The PF improvement was obtained due to the formation in the composite system of a microstructure in which semiconducting-like particles of TmNiSb were covered with a metallic layer of TmNiSn. The largest Seebeck coefficient S = 137 μV/K was observed for HH alloy TmNiSb at 560 K. In turn, TmNiSn showed a metallic behavior with small negative thermoelectric power (S = –2.6 μV/K).