Understanding and Tailoring Thermal Transport in Perovskite Oxides

Perovskite oxides have been extensively used in electronic, photovoltaic, and piezoelectric applications, owing to their remarkable flexibility in terms of structures, compositions, and properties. In the realm of semiconductor-oxide-based electronic devices, the thermal transport properties of perovskite oxides are crucial for fulfilling specific requirements, including heat dissipation, thermal switches, and energy conversion and storage. In this talk, I will highlight our work on understanding and further tailoring thermal transport in nanoscale perovskite thin films using lanthanum strontium cobaltite (LSCO) and strontium stannate (SSO) as two model systems. We demonstrate a tuning factor exceeding five in the thermal conductivity of LSCO through electrolyte gating at room temperature. This gating induces non-volatile topotactic phase transformation in LSCO from perovskite to brownmillerite, accompanied by a metal-insulator transition. By combining thermal and electronic transport measurements, model analyses based on molecular dynamics and Boltzmann transport, and structural characterization by X-ray diffraction, we uncover and deconvolve the effects of these transitions on heat carriers, including electrons and lattice vibrations. For SSO as an emerging ultra-wide bandgap material, we detail the impact of strong lattice anharmonicity on its temperature-dependent thermal conductivity, attributed to its distorted orthorhombic structure with tilted SnO₆ octahedra. The insights gained from these studies into the structure-thermal property relationships of LSCO and SSO enable us to engineer and optimize functional materials based on perovskite oxides, thereby advancing their utilization in solid-state thermal regulation and management applications such as thermal diodes, switches, and power electronics. This presentation is in memory of Dr. Natalio Mingo.