Phase Stability and Thermoelectric Properties of Half-Heusler (M~a, M~b)NiSn (M~a, M~b = Hf, Zr, Ti)

摘要

Aiming to improve thermoelectric properties of half-Heusler (M~a,M~b)NiSn alloys (M~a,M~b = Hf, Zr, Ti), phase equilibria in the (M~a,M~b)NiSn systems were investigated focusing on the phase separation of TiNiSn from ZrNiSn and HfNiSn while (Zr,Hf)NiSn forms all proportion miscible solid solution. Diffusion couples consisting of liquid Sn and solid (Ti,Zr)Ni were used to examine the partitioning behavior which is associated with T-rich and Ti-poor half-Heusler phase separation during the reaction at the interface. Thermal conductivity can be reduced in (M~a_(0.5),M~b_(0.5))NiSn and (Ti_(0.13),Zr_(0.87))NiSn alloys due to the solid solution effect of M-site substitution. (Ti_(0.13),Zr_(0.87))NiSn alloy has high potential as a ecological thermoelectric material.