Enhancing Thermal Conductivity Switching in a Bulk Ferroelectric by Defect Engineering

Active thermal management requires thermal switching materials whose thermal conductivity can be efficiently controlled by external stimuli. Ferroelectrics are proven to be a promising platform for electric-field control of heat conduction, yet the intrinsic switching mechanisms in bulk single crystals and the role of defects remain less explored. Here, we demonstrate enhanced electric-field-induced thermal conductivity switching in bulk single-crystalline BaTiO3 at room temperature through defect engineering. Using a customized steady-state platform with in situ fields up to ±10 kV/cm, we observe a conductivity modulation of up to 35% in fresh BaTiO3 driven by polarization reorientation and domain restructuring. First-principles finite-temperature lattice dynamics calculations show that the switching originates from anisotropic phonon transport linked to domain configurations rather than strain-induced effects. We further find that ambient and thermal aging enhance the switching contrast, which may arise from the defect dipole alignment that modifies phonon-defect scattering. These results establish defect engineering as a promising strategy for enhancing thermal conductivity switching in bulk ferroelectrics and provide an experimental platform for exploring electric-field-controlled thermal transport.