Thermoelectric Properties of Zr0.5Hf0.5Ni0.8Pd0.2Sn0.99Sb0.01 half-Heusler Alloy with WO3 Inclusions

Abstract

AbstractZr0.5Hf0.5Ni0.8Pd0.2Sn0.99Sb0.01 composites with various concentrations of WO3 inclusions were synthesized by mechanical alloying using high energy shaker mill. High density hot pressed pellets of the synthesized materials were characterized using powder X-ray diffraction and transmission electron microscopy and their thermoelectric properties were investigated in the temperature range from 300 to 750 K. The electrical conductivity of the composites at 300 K decreases from 2500 S/cm for 0 wt.% WO3 alloy to 2200 S/cm for the composite with 2 wt.% WO3 inclusion. The electrical conductivity of composites containing 5 wt.% and 10 wt.% WO3 inclusions showed sharp increases with increasing WO3 content. The electrical conductivity of the composites monotonically decreases with rising temperature. All samples showed n-type semiconducting behavior and the thermopower values decrease with increasing WO3 content. The lattice thermal conductivity of the composites increases with increasing WO3 content. However, these values are about 30% lower than that of Zr0.5Hf0.5Ni0.8Pd0.2Sn0.99Sb0.01 alloy prepared by high temperature solid-state techniques. The synthesized composites showed lower figure of merit than the half-Heusler matrix due to large reduction in the thermopower values with increasing WO3 content.