Thermoelectric properties of (Ti,Zr,Hf)CoSb type half-heusler compounds

Half-Heusler compounds have a possibility as a new thermoelectric material due to the large thermoelectric power and low thermal conductivity derived from the band structure and voids in the crystal, respectively. Among these materials, we have paid attention to (Ti,Zr,Hf)CoSb system, and have investigated the improvement of the thermoelectric figure of merit from the measurements of the electrical resistivity, thermoelectric power, and thermal conductivity. We obtained the largest ZT = 0.027 on TiCoSb at 921 K. From the analysis by Jonker plot and the difference of the atomic radii between titanium and cobalt on TiCoSb, it is indicated that the dispersion between our data and a few previous data was originated in two effects: one is deviations from the stoichiometric composition by evaporation of antimony on arc melting, and the other is relaxation of the structural disorder by annealing.