Abstract
High-efficiency thermoelectric conversion systems require materials with a high electrical conductivity, a large Seebeck coefficient and a low thermal conductivity. Traditional ternary MNiSn (M = Ti, Zr, Hf) half-Heusler alloys are known to have reasonable electrical and thermoelectric properties, but undesirably high thermal conductivities. To reduce thermal conductivity, quaternary alloys, e.g. Zr 0.5 Ti 0.5 NiSn, were fabricated to suppress the lattice thermal conduction by a mass fluctuation scattering effect. In the present work, the effects of antimony doping are investigated in an attempt to further enhance the thermoelectric properties of multi-element alloys. It is found that for optimized contents of Sb, the Zr 0.5 Ti 0.5 NiSn 1-x Sb x alloys possess enhanced thermoelectric power factors. The highest figure-of-merit of the Sb-doped alloys at room temperature is 0.16, which is about 4 times higher than the parent Zr 0.5 Ti 0.5 NiSn alloy. © Lavoisier.