Thermoelectric propertiesof Ti_X(Zr,Hf)_1-XNiSnhalf-Heusler ompounds

N. Shutoh, S. Sakurada

Corporate Research and Development Center, Toshiba Corp., Komukai-toshiba-cho,Saiwai-ku, Kawasaki, Kanagawa, 212-8582, JAPAN

Half-Heusler compounds(MgAgAs-type) with the general formula MNiSn where M is a group IV transitionmetal (Hf, Zr, or Ti) have good potential for thermoelectric applications. Inthis paper, the thermoelectric properties of Ti_X(Zr,Hf)_1-XNiSnhalf-heusler compounds prepared by conventional powder metallurgytechnique have been investigated.It is shown that the substitution of Ti for Zr-Hf results in a significantreduction of the thermal conductivity as low as 3.0 W/mK at room temperature.We also found the remarkable enhancement of thermoelectric power by Tisubstitution. The doping with Sb for Ti_X(Zr,Hf)_1-XNiSnleads to reduction in electric resistivity and, accordingly, to enhancement ofdimensionless figure of merit ZT more than 1.0 at 700 K. It would be possibleto develop high performance thermoelectric modules by using this half-Heuslercompounds.