Response of vibrational properties and thermal conductivity of perovskites to pressure

Abstract

We study the response of SrTiO3 and KTaO3's vibrational properties and thermal conductivity Λ to pressurization. Our goal is to improve the understanding of the relationship between crystal structure, vibrational dynamics, and thermal conductivity in perovskites. We measure the thermal conductivity of SrTiO3 and KTaO3 up to 28 GPa by time-domain thermoreflectance. We also perform Raman scattering and stimulated Brillouin scattering measurements of SrTiO3 and KTaO3 to characterize changes in vibrational dynamics with pressure. The thermal conductivity of SrTiO3 increases under pressure with a slope comparable to that of other perovskites whose thermal conductivity has been measured versus pressure. Alternatively, the thermal conductivity of KTaO3 has a stronger pressure dependence than that of other materials with similar crystal structure. We correlate pressure-induced changes in Raman and Brillouin spectra with pressure-induced changes in thermal conductivity. We show that pressure-induced changes in phonon lifetimes dominate the pressure dependence of thermal conductivity. This study provides benchmark knowledge of why Λ depends on pressure and improves understanding of structure/thermal-property relationships.