Optimizing the thermoelectric performance of FeVSb half-Heusler compound via Hf-Ti double doping

FeVSb-based half-Heusler (HH) compound has recently been identified as promising medium-high temperature thermoelectric (TE) materials for power generation applications. In this study, enhanced thermoelectric performance of Fe(V0.8Hf0.2)(1-x)TixSb (x = 0.0, 0.2, 0.4, 0.5, 0.6) HH alloys by Hf-Ti dual-doping was reported studied in a temperature range from 100 to 900 K. A high content of Ti doping not only optimized the carrier concentration but also reduced the lattice thermal conductivity, which all contribute to high zT. As a result, a zT value was increased by -20% at 873 K for Fe(V0.8Hf0.2)(0.8)Ti0.2Sb compound. Hf-Ti dual doping significantly reduced the lattice thermal conductivity due to enhanced point defect scattering which is mainly attributed to mass fluctuations. Hence, suppressed the material's total thermal conductivity. A reduction of similar to 20% was obtained for the Fe(V0.8Hf0.2)(0.8)Ti0.2Sb sample, compared with the single Hf-doped FeVSb sample and of similar to 80% compared to FeVSb at room temperature.