Effect of partial filling of the structural vacant sites on the thermoelectric properties of Zr_(0.25)Hf_(0.75)NiSn half-Heusler alloy

摘要

Composites containing mainly-half-Heusler MNiSn (HH) and full-Heusler MNi2Sn (FH) were prepared by solid state reaction of a mixture of polycrystalline bulk HH alloy with various concentrations of Ni up to 10 wt.%. Electrical conductivities, thermal conductivities and thermopowers of spark plasma sintered specimens of the as synthesized composite materials were measured in the temperature range from 300 K to 750 K. The conduction type of the composite changes from semiconductor to semimetal for Ni concentrations up to 2 wt.% and from semimetal to metal for higher Ni concentrations above 5 wt.%. A strong reduction in lattice thermal conductivity was observed for the composite containing 10 wt. % Ni inclusions.