Optimization of the thermoelectric properties of FeNbSb-based half-Heusler materials

FeNbSb-based half-Heusler compounds have recently been reported as promising materials for good high-temperature thermoelectric materials with a ZT > 1. Their electronic structure and thermoelectric properties are investigated based on a first-principles simulation and the semi-classical Boltzmann transport theory. The band structures show not only light and heavy bands but also high band degeneracy near the valence band maximum, which is beneficial for thermoelectric performance. The calculated Seebeck coefficients of p-type FeNbSb at high carrier concentrations exhibit the expected high values, which is consistent with experimental data. The evolution of the electrical conductivity and power factor with carrier concentration at different temperatures is investigated. Our results show that the thermoelectric performance of p-type FeNbSb can be improved by appropriate substitution; for example, by doping Hf on the Nb site, the maximum ZT of the p-type FeNb1-xHfxSb can reach similar to 1.5 at 1200 K. This study can provide some theoretical guidance for experimental research to improve the thermoelectric performance of FeNbSb-based half-Heusler compounds.