Thermoelectric and Thermophysical Properties of TiCoSb-ZrCoSb-HfCoSb Pseudo Ternary System Prepared by Spark Plasma Sintering

We studied the thermoelectric and thermophysical properties of TiCoSb-ZrCoSb-HfCoSb pseudo ternary system. Polycrystalline samples were prepared by a spark plasma sintering (SPS) technique, and their thermoelectric properties above room temperature and thermophysical properties at room temperature were measured. All the samples were identified as a half-Heusler compound by the X-ray diffraction analysis. The lattice parameter, electrical resistivity and thermoelectric power systematically change with the composition in the pseudo ternary phase diagram. All the samples indicated negative values of the thermoelectric power. Low thermal conductivity was achieved in the samples with the composition near the center of the pseudo ternary phase diagram where the effect of the alloy scattering becomes large. The maximum value of ZT was obtained to be 0.073 at 790 K for Ti0.25(Zr0.5Hf0.5)0.75CoSb.