Dependence of the Thermal Conductivity of BiFeO3 Thin Films on Polarization and Structure

The role of the ferroelectric polarization state and crystal structure in determining the room-temperature thermal conductivity of epitaxial BiFeO3 thin films is investigated. The ferroelectric domain configuration is varied by changing the oxygen partial pressure during growth, as well as by polarizing the samples by the application of an in situ electric field during the thermal conductivity measurement. However, little or no dependence of thermal conductivity on the ferroelectric domain structure is observed. In contrast, the thermal conductivity significantly depends on the morphotropic phase structure, being about 2/3 as large in tetragonal-like compared to rhombohedral-like BiFeO3 film. The substantial structural dependence of thermal conductivity found here may provide a route to reversible manipulation of thermal properties.