Unveiling the thermoelectric potential of KBaBi: a dive into high-temperature stability and thermoelectric performance

We systematically investigate the mechanical, electronic, and thermoelectric properties of the half-Heusler compound KBaBi using first-principles methods, including self-consistent phonon theory and the Boltzmann transport equation. Our results demonstrate that KBaBi maintains good thermal and mechanical stability at elevated temperatures. Importantly, this study incorporates higher-order anharmonic effects, especially four-phonon scattering, which are manifestations of nonlinear lattice dynamics. These nonlinear interactions drastically suppress the lattice thermal conductivity, reducing it to as low as 0.49 Wm $$^{-1}$$ - 1 K $$^{-1}$$ - 1 at 800K. For electronic transport, we account for multiple scattering mechanisms to determine carrier relaxation times with improved accuracy. High band degeneracy near the valence band maximum leads to a large Seebeck coefficient under p-type doping. A peak dimensionless figure of merit zT of 3.22 is achieved at 800 K, highlighting KBaBi as a promising thermoelectric material with strong nonlinear phonon-limited thermal transport behavior. Graphical abstract