Thermoelectric properties of strontium sulfide via first-principles calculations

Abstract

Thermoelectric materials are attracting increasing attention for their ability to convert heat into cleaner electricity. In this work, we have systematically studied the thermoelectric properties of strontium sulfide (SrS) in the rock-salt structure based on first-principle calculations together with Boltzmann transport theory. The phonon spectra of the rock-salt structure SrS have no imaginary frequency modes, indicating the dynamic stability of SrS. The room-temperature lattice thermal conductivity κι of SrS is calculated to be 10.70 W/mK. We also calculated the phonon-mode contribution to κι, scattering rate, and mean free path (MFP). It is found that the acoustic branches have obvious contribution to the total lattice thermal conductivity, and the MFP can provide guidance for designing thermoelectric nanostructures. The ZT values of SrS with respect to carrier concentration n and temperature T are also obtained. It is found that, when temperature is from 300 K to 700 K, for p-type, the highest ZT value calculated by PBE varies from 0.15 to 0.41, and the highest ZT value by HSE varies from 0.10 to 0.30; For n-type, the highest ZT value by PBE varies from 0.08 to 0.26, and the highest ZT value by HSE varies from 0.09 to 0.28. In general, the p-type SrS has the better thermoelectric property than the n-type SrS.