Effect of Bi-substitution on structural stability and improved thermoelectric performance of p-type half-Heusler TaSbRu: A first-principles study

Recently, Fang et al. have predicted a high ZT of 1.54 in TaSbRu alloys at 1200 K from first-principles without considering spin-orbit interaction, accurate electronic structure, details phonon scattering, and energy-dependent holes relaxation time. Here, we report the structural stability thermoelectric performance Bi-Substituted p-type calculations theses important parameters. This indirect bandgap semiconductor (Eg=0.8 eV by TB-mBJ+SOC) has highly dispersive degenerate valence bands, which lead to maximum power factor, 3.8 mWm-1K-2 300K. As Sb-5p small contribution formation, substitution Bi on Sb site does not cause significant change structure. Although Seebeck coefficient increases due slight changes bandgap, electrical conductivity, hence, factor reduces ~3 mW m-1K-2 300K (50% Bi). On other side, lattice thermal conductivity drops effectively 5 20 W/m as introduces acoustic region intensify scattering. Thus, value is improved through Bi-substitution, reaching 1.1 Bi) 0.45 (pure TaSbRu) only. Therefore, present study suggests how improve TE Sb-based half-Heusler compounds (with 50% promising material for high-temperature applications.