Thermoelectric properties of ZrNiSn based half Heusler compounds

The thermoelectric properties of titanium substituted ZrNiSn have been measured from room temperature to 1000 K. The samples were prepared by arc melting followed by spark plasma sintering (SPS) technique. High SPS temperature increased the homogeneity of titanium substituted sample, result at increase of the electrical conductivity without deterioration of the Seebeck coefficient. Zr_0.7Ti_0.3NiSn showed higher power factor than pure ZrNiSn, the value reached 4 mW/mK² at 700 K. The SPS temperature had little influence on the thermal conductivity. However, the titanium substituted sample decomposed upon annealing at high temperature. Thus appropriate heat and preparation treatment appeared to be necessary for the samples containing titanium. Highest ZT was obtained for Zr_0.7Ti_0.3NiSn, equal to 0.48 at 800 K.