Thermoelectric performance of half-Heusler compounds MYSb (M = Ni, Pd, Pt)

Abstract

Motivated by the recent findings of potential topological insulators and good high-temperature thermoelectric materials in the half-Heusler compounds based on heavy metals, we combine first-principles and Boltzmann transport theory to systematically study the electronic structure and thermoelectric performance of half-Heusler compounds MYSb (M = Ni, Pd, Pt). We find that among these three compounds PtYSb is a direct band-gap semiconductor, while the remaining two show indirect band-gaps. Chemical potential dependence of Seebeck coefficients and power factors (PFs) are discussed in terms of electronic band structure and density of states near the Fermi level. Calculated Seebeck coefficients of these compounds are found to be about 245 µV K−1 at room temperature, and n-type doping would present a better PF. NiYSb has a high PF of 9.5 × 1011 W K−2 m−1 s−1 at 900 K and thus exhibits good high-temperature thermoelectricity. The temperature dependence of Seebeck coefficients under different carrier concentrations are also presented, which are in good agreement with available theories and experiments.