Significant first-principles electron-phonon coupling effects in the LiZnAs and ScAgC half-Heusler thermoelectrics
arXiv:2506.13675 · doi:10.1103/ss62-r49n
Abstract
The half-Heusler (hH) compounds are currently considered promising thermoelectric (TE) materials due to their favorable thermopower and electrical conductivity. Accurate estimates of these properties are therefore highly desirable and require a detailed understanding of the microscopic mechanisms that govern transport. To enable such estimations, we carry out comprehensive first-principles computations of one of the primary factors limiting carrier transport, namely the electron-phonon () interaction, in LiZnAs and ScAgC. Our study first investigates their electron and phonon dispersions and then examines the temperature-induced renormalization of the electronic states. We then solve the Boltzmann transport equation (BTE) under multiple relaxation-time approximations (RTAs) to evaluate the carrier transport properties. Phonon-limited electron and hole mobilities are comparatively assessed using the linearized self-energy and momentum RTAs (SERTA and MRTA), and the exact or iterative BTE (IBTE) solutions within coupling. Electrical transport coefficients for TE performance are also comparatively analyzed under the constant RTA (CRTA), SERTA, and MRTA schemes. The lattice thermal conductivity, determined from phonon-phonon interaction, is further reduced through nanostructuring techniques. The bulk LiZnAs (ScAgC) compound achieves the highest figure of merit () of 1.05 (0.78) at 900 K with an electron doping concentration of 10 (10) cm under the MRTA scheme. This value significantly increases to 1.53 (1.0) for a 20 nm nanostructured sample. The remarkably high achieved through inherently present phonon-induced electron scattering effects, combined with grain-boundary engineering, opens a promising path for discovering highly efficient and accurate next-generation hH TEs.
Accepted manuscript in Phys. Rev. B