Local structure of complex half-Heusler thermoelectrics with low thermal conductivity

The aim of the proposal is to use total scattering and pair distribution function analysis to study the local structure of three novel half-Heusler materials. These are rapidly quenched and slow-cooled Nb5/6CoSb with intrinsic vacancies and Zn0.5Ti0.5NiSb. In the former system heat treatment affects the short range clustering of Nb vacancies and leads to substantial differences in thermal conductivity. The latter system has an an intrinsically low thermal conductivity, despite the absence of mass or strain disorder. Large box Reverse Monte Carlo simulations will be used to determine the real-space structure of these materials. Improved knowledge of the structure is of vital importance to understand the measured low thermal conductivity in these materials systems.