Synthesis and thermoelectric properties of Ti-substituted (Hf0.5Zr0.5)1-xTixNiSn0.998Sb0.002 Half-Heusler compounds

The Half-Heusler (Hf0.5Zr0.5)1-xTixNiSn0.998Sb0.002 (x = 0, 0.1, 0.3, 0.5 and 0.7) compounds were prepared by vacuum induction melting method combined with annealing, mechanical grinding and spark plasma sintering (SPS) process. For the sintered bodies, the phase and the temperature dependent thermoelectric properties were characterized. The pure phases of Half-Heusler (HH) structure were successfully obtained by subsequent SPS at 1273 K for 1 h under vacuum. With Ti substitution the lattice parameter decreased systematically and carrier concentration increased showing n-type semiconducting behavior, and the thermal conductivity decreased due to reduction of lattice thermal conduction. As a result, it was obtained the figure of merit ZT∼0.92 at 837 K at x = 0.3.