Effect of Ti substitution on the thermoelectric properties of (Zr,Hf)NiSn half-Heusler compounds

The effect of Ti substitution on the thermoelectric properties of (Zr,Hf)NiSn half-Heusler compounds was studied. It was found that the substitution of Ti for (Zr,Hf) reduced the thermal conductivity significantly to a low value of 3.0W∕mK at room temperature. In addition, a remarkable enhancement of the Seebeck coefficient due to Ti substitution was observed. Furthermore, doping of the Sn sites in (Ti,Zr,Hf)NiSn with Sb led to a reduction in the electrical resistivity and to a corresponding enhancement of the power factor. In Sb-doped (Ti,Zr,Hf)NiSn compounds, the dimensionless figure of merit, ZT, increased with the increase in temperature and reached a high maximum value of 1.5 at 700K.