Impact of Uniaxial Strain Treatment on Thermoelectric Performance of Alkaline-Earth Stannate Oxides: DFT Study

Recently, perovskite oxide-based materials, particularly alkaline-earth stannates, have shown promising candidates for thermoelectric applications. However, previous studies mainly concentrated on bulk material rather than thin film. A strategy like band engineering has been used to improve the thin film thermoelectric performance by strain treatment. This study examines the thermoelectric properties of alkalineearth stannate oxides under uniaxial strain using density functional theory (DFT) and Boltzmann transport theory. The results reveal that the tensile strain treatment predominantly improved the electrical conductivity, with BaSnO3 contributing 6.5 times higher electrical conductivity value under uniaxial strain. Meanwhile, compressive strain enhanced the Seebeck coefficient. Additionally, for CaSnO3, the Seebeck coefficient results suggest an interplay between charge carriers due to band gap shifting. Power factor improvements were seen between $300-650 \mathrm{~K}$ across all materials. Furthermore, strain generally increased the power factor at above 650 K. The study emphasizes the importance of optimizing strain direction and magnitude to achieve the desired thermoelectric performance enhancement.