Effects of partial substitution of Co by Ni on the high-temperature thermoelectric properties of TiCoSb-based half-Heusler compounds

TiCoSb-based half-Heusler compounds were prepared by solid-state reaction and their thermoelectric properties were studied. The un-doped TiCoSb compound shows n-type conduction and demonstrates high Seebeck coefficient at high temperatures. The partial substitution of Co by Ni caused great increase in electron concentration and electrical conductivity, while the Seebeck coefficient and the thermal conductivity showed little change when Ni content (x) is below 5%. A maximum power factor of 16 μW/K2 cm and a maximum dimensionless figure of merit (ZT) of 0.27 have been obtained for the composition of TiCo0.95Ni0.05Sb at 900 K.