Hidetoshi Miyazaki

Abstract:

Half-Heusler NiZrSn alloys have excellent thermoelectric properties [1], mechanical strength [2], and oxidation resistance [3], and are being commercialized for the development of thermoelectric power generation devices that operate in high temperature environments. The excellent thermoelectric conversion properties of half-Heusler NiZrSn alloys are attributed to their semiconducting electronic structure with a narrow band gap near the Fermi level and low thermal conductivity. Although the half-Heusler structure with high crystal symmetry inherently results in high thermal conductivity, it has been confirmed by synchrotron powder diffraction [4] and X-ray absorption fine structure measurements [5] that in NiZrSn alloys, interstitial atomic defects exist in the vacancy sites and the surrounding atoms are distorted. This has been found to contribute to a significant decrease in thermal conductivity. In this presentation, we will show that high thermal conversion properties can be realized by utilizing the defect structure at the vacancy site, together with the latest research results.