Effect of carrier doping on the thermal conductivity of MNiSn based half-Heusler alloy

Thermal conductivity of doped MNiSn (M = Ti, Zr) half-Heusler alloys has been investigated from room temperature to 1000 K. Nonnegligible increase of thermal conductivity was observed for all the samples at high temperature. The temperature dependence appeared to the corresponding to the change of electrical properties and carrier concentration, indicating that the electron-hole pair generation caused the increase of thermal conductivity. The effect, called ambipolar diffusion effect, depends on a bandgap and a ratio of electron and hole conduction. In this study the bandgap was determined from electrical conductivity of yttrium doped of ZrNiSn and the temperature dependence of the ambipolar diffusion effect was quantitatively investigated