Electronic structure and thermoelectric properties of Ta-based half-Heusler compounds with 18 valence electrons

Abstract

Recently, the half-Heusler compounds with 18 valence electrons have been considered as promising candidate for thermoelectric applications due to their interesting properties. In this work, the structural, electronic and thermoelectric properties of Ta-based half-Heusler TaXY (X = Ru, Rh; X = Sb, Bi, Sn and Pb) have been investigated using the full-potential linearized augmented plane-wave (FP-LAPW) method within the density functional theory (DFT) and the classical Boltzmann transport theory. Generalized gradient approximation as parameterized by Wu-Cohen (GGA-WC) and Tran-Blaha modified Becke-Johnson exchange potential (mBJ) are employed for taking on account the exchange-correlation electron potential. All four studied materials are semiconductor with indirect band gap 0.815 eV for TaRuSb, 0.906 eV for TaRuBi, 1.109 eV for TaRhSn and 1.138 eV for TaRhPb. Additionally, the spin-orbit coupling (SOC) decreases slightly the band gap of these materials. Thermoelectric properties, such as, Seebeck coefficient, electrical conductivity, power factor, total thermal conductivity and figure of merit are calculated in function of chemical potential. Obtained results show that TaXY compounds have good thermoelectric performance with high figure of merit value 0.99.