Inelastic Neutron Scattering Study of defective half-Heusler Material

Typical Half-Heusler compounds, identified as promising high temperature thermoelectric materials due to their unexpected semiconducting nature and good thermal properties. Several HH compounds are recently found to contain high concentrations of vacancies. These vacancies exhibit some specific distributions, such as short-range ordering in Nb0.8CoSb and possible Zig-zag distribution in Eu2ZnSb2. Intriguingly, these vacancy defective compounds exhibit much lower lattice thermal conductivity than their counterparts without vacancies. Here, we synthesized a series of ZrCoSb vacancy-defective compounds that can control the degree of vacancy order and thermal conductivity without changing their composition. These defective ZrCoSb samples can be considered as a hierarchical structure of order at different length scales, short-range order in some samples and long-range order in others. However, a comprehensive understanding is missing due to the lack of an experimental measurements and analysis of lattice dynamics in those compounds. In this proposal, we want to apply neutron scattering technique to study the dynamic spectra, hence to assess the significance of vacancies in the suppression of lattice thermal conductivity.