Huge power factor in p-type half-Heusler alloys NbFeSb and TaFeSb

Abstract NbFeSb is a promising thermoelectric material which according to experimental and theoretical studies exhibits a high power factor of up to 10 mW m⁻¹ K⁻² at room temperature and ZT of 1 at 1000 K. In all previous theoretical studies, κ _latt is calculated using simplified models, which ignore structural defects. In this work, we calculate κ _latt by solving the Boltzmann transport equation and subsequently including the contributions of grain boundaries, point defects and electron–phonon interaction. The results for κ _latt and ZT are in excellent agreement with experimental measurements. In addition, we investigate theoretically the thermoelectric properties of TaFeSb. The material has recently been synthesised experimentally, thus confirming the theoretical hypothesis for its stability. This encourages a full-scale computation of its thermoelectric performance. Our results show that TaFeSb is indeed an excellent thermoelectric material which has a very high power factor of 16 mW m⁻¹ K⁻² at room temperature and ZT of 1.5 at 1000 K.