Roles of Point Defects in Thermal Transport in Perovskite Barium Stannate

Perovskite barium stannate (BaSnO₃) is a promising candidate that can be used as transparent conducting oxide in optoelectronic devices and as the channel material in high-mobility oxide electronics. In this work, we calculate the lattice thermal conductivity and investigate the impact of point defects on thermal transport in BaSnO₃ based on the phonon Boltzmann transport equations with interatomic force constants from first-principles calculations. In pristine BaSnO₃, we find the contribution of acoustic phonons to thermal transport accounts for 54% at 300 K and the rest is attributed to the lower-frequency (27.5-50 THz) optical modes with relatively high group velocity. We show oxygen vacancies and impurities can cause noticeable reduction in thermal conductivity of BaSnO₃, but the corresponding mechanisms differ in terms of scattering rates on different phonon modes. The thermal conductivity reduction due to oxygen vacancies at 300 K is mainly caused by the increased scattering of the acoustic phonons and the low-frequency optical phonons. Lanthanum and potassium impurities mainly increase the scattering of acoustic phonons, but antimony impurity lowers the thermal conductivity by increasing the scattering rate of dominant phonons, including both the acoustic modes and the low-frequency optical modes. The results and findings facilitate us to better understand the thermal transport mechanisms of perovskite oxides with an emphasis on the impact of oxygen vacancies and impurities on the thermal properties of BaSnO₃.