Effect of Sb doping on the thermoelectric properties of Ti-based half-Heusler compounds, TiNiSn1-xSbx

Half-Heusler alloys (MgAgAs type) with the general formula MNiSn where M is a group IV transition metal (Hf, Zr, or Ti) are currently under investigation for potential thermoelectric materials. These materials exhibit a high negative thermopower (-40 to -250 mu V/K) and low electrical resistivity values (0.1-8 m Omega cm) both of which are necessary for a potential thermoelectric material. Results are presented in this letter regarding the effect of Sb doping on the Sn site (TiNiSn1-xSbx). The Sb doping leads to a relatively large power factor of (0.2-1.0) W/m K at room temperature for small concentrations of Sb. These values are comparable to that of Bi2Te3 alloys, which are the current state-of-the-art thermoelectric materials. The power factor is much larger at T approximate to 650 K where it is over 4 W/m K making these materials very attractive for potential power generation considerations. (C) 2000 American Institute of Physics. [S0003- 6951(00)01142-6].