Effects of partial substitution of ni by pd on thermoelectric properties of ZrNiSn-based compounds

The ZrNiSn-based half-Heusler compounds crystallize in a cubic structure of the MgAgAs type, and belong to semiconductors with narrow band gaps. Due to promising potential as new thermoelectric materials, they have attracted much attention in recent years. In the present paper, compounds with Pd partial substitution on the Ni sites, were successfully synthesized by solid state reaction method. Effects of such substitution on the thermoelectric properties were mainly studied. It is shown that, the substitution of Pd for Ni resulted in a significant reduction in the thermal conductivity. The Seebeck coefficient also decreased, but only by a small amount. In a Hf_0.5Zr_0.5 Ni_0.8Pd_0.2Sn_0.99Sb_0.01 compound, a power factor of 19.5 μW/cm-K² and a thermal conductivity as low as of 4.5 W/m-K were measured at room temperature. The dimensionless figure of merit, ZT, increased with increasing temperature and reached a maximum value of 0.7 at about 800 K