Thermoelectric properties of strontium oxide under pressure: First-principles study

Abstract

We studied the electronic structure and thermoelectric properties of SrO under pressure via first-principle calculations. The obtained phase transition pressure of SrO from B1 phase to B2 phase is 37 GPa at room temperature. At Gamma point, the phonon largest peak frequencies of SrO are 14.6 THz (B1 phase) and 18.9 THz (B2 phase), in addition, the LO-TO splitting frequencies are 8.6 THz (B1 phase) and 8.21 THz (B2 phase) under 0 GPa for B1 phase and 64 GPa for B2 phase, respectively. The B1 phase of SrO has an indirect band gap (3.31 eV) at 0 GPa, while the B2 phase has a smaller direct band gap (2.27 eV) at 70 GPa. At 0 GPa, the born effective charges of SrO are 2.44 (B1 phase) and 2.60 (B2 phase), and the dielectric constants are 3.80 (B1 phase) and 4.47 (B2 phase). When the temperature reaches 700 K and the carrier density reaches 1.2×1021 cm−3, the ZT value of B1 phase reaches 0.61 at 0 GPa. By comparison, we found that the thermoelectric properties of the B1 phase behave better than those of the B2 phase at zero pressure.