Effects of hydrostatic pressure on the thermoelectric performance of BaZrS 3

Recently, the BaZrS 3 is considered suitable for thermoelectric (TE) applications due to relatively small band gap and low lattice thermal conductivity. To unravel the TE transport properties of BaZrS 3 under high-pressure condition, first-principles calculations combined with semi-classical Boltzmann transport theory are carried out to investigate the effects of pressure on its TE transport properties. The nonlinear relationship between lattice thermal conductivity and pressure has been observed, which can be explained by the irregular response behavior of phonon lifetime to pressure, due to the synergetic effects of lattice anharmonicity and three-phonon scattering channel. Also, application of hydrostatic pressure can tune the electronic structure of BaZrS 3 , i.e., both band effective mass and band degeneracy generally decrease with the increasing pressure, which causes decrease in the Seebeck coefficient and increase in the electrical conductivity, ultimately leading to reduced power factor. The increased thermal conductivity together with decreased power factor results in a decrease in optimal figure of merit value for BaZrS 3 . The presented results, thus, suggest that the TE properties of BaZrS 3 is degraded under hydrostatic pressure.