Enhancing thermoelectric performance of FeNbSb half-Heusler compound by Hf-Ti dual-doping

FeNbSb half-Heusler compound has recently been identified as a promising high temperature thermoelectric material for power generation with figure of merit zT > 1. Single doping is a general and effective way to simultaneously adjust the electrical power factor and reduce the lattice thermal conductivity in this system. Here we report the enhanced thermoelectric performance of FeNb0.9-xHf0.1TixSb ( 0 <= x <= 0.1) by Hf-Ti dual-doping, which shows a maximum figure of merit zT of 1.32 at 1200 K. Hf-Ti dual-doping significantly reduces lattice thermal conductivity. A reduction of 30% was obtained at room temperature for the FeNb0.84Hf0.1Ti0.06Sb sample, compared with the single Ti-doped FeNbSb sample. The reduction of the lattice thermal conductivity in the Hf-Ti dual-doped FeNbSb compounds was attributed to both mass and strain field fluctuations.