Thermoelectric properties of (Ti,Zr) CoSnxSb1-x half-Heusler compounds

We have studied (Ti,Zr)CoSb half-Heusler compounds substituted by tin for antimony in order to develop p-type compounds. The electrical resistivity and thermoelectric power were measured from 323 to 1000 K. The thermal diffusivity was measured by a laser flash technique from room temperature to 1000 K. From the above-mentioned data, we calculated the dimensionless figure of merit ZT. By increasing the tin content of TiCoSn_xSb_1-x and ZrCoSn_xSb_1-x, the electrical resistivity decreased and the sign of the thermoelectric power changed from negative (n-type) to positive (p-type). The thermal conductivity was reduced by an alloy scattering effect between antimony and tin. Relatively high ZT values were obtained; ZT = 0.30 at 959 K for TiCoSn_0.1Sb_0.9 and ZT= 0.45 at 958 K for ZrCoSn_0.1Sb_0.9