Effect of substitutions on the thermoelectric figure of merit of half-Heusler phases at 800 °C

The merit of thermally stable MNiSn (M=Ti, Zr, Hf) half-Heusler phases, as n-type thermoelectric materials, for high-temperature power generation has been examined. Sb doping at the Sn site is shown to increase both the figure of merit, ZT, and the temperature at which ZT is maximized. The benefits of increased alloying at the M and Ni sites, on the thermal conductivity and thermoelectric transport properties, have also been investigated. The thermoelectric figure of merit, ZT∼0.8 at T∼800°C, for select Sb-doped MNiSn alloys was found to meet or exceed the industry benchmark set by SiGe alloys.