Low lattice thermal conductivity driven by weak interlayer interaction and acoustic–optical coupling in the SrZnSbF thermoelectric material

The thermoelectric performance of the SrZnSbF compound is comprehensively evaluated using first-principles calculations and Boltzmann transport theory in present study. The electronic band structure shows that the SrZnSbF compound is semiconductor with a direct bandgap of 0.64 eV. A comprehensive evaluation of elastic modulus calculations, <i>ab initio</i> molecular dynamics simulations and the phonon dispersion confirmed that the SrZnSbF compound has excellent thermal and dynamic stabilities. The weak interlayer van der Waals forces between [Sr₂F₂]²⁺ and [Zn₂Sb₂]^2- layers, the distribution characteristics of electronic antibonding states near the Fermi level, and the strong acoustic-optical coupling in the low-frequency region of the phonon dispersion curves lead to the strong anharmonicity of the SrZnSbF compound, resulting in a low lattice thermal conductivity (1.68 W m^-1 K^-1) at 300 K. By combining multiple carrier scattering mechanisms, the thermoelectric performance of SrZnSbF compound is evaluated, and an optimal dimensionless figure of merit (<i>ZT</i>) of ∼1.93 (p-type) is achieved at 900 K. The current work not only reveals the thermoelectric enhancement mechanism of SrZnSbF compound by electron-phonon synergistic regulation, but also highlights the application potential of the SrZnSbF compound as a high-temperature thermoelectric material.