Electric-Field Enhanced Phonon Thermal Transport in Relaxor Ferroelectric PMN-30PT using Neutron Scattering

The increasing demand for thermal management arises from the need for highly efficient energy use and harvesting. Precise control of heat flow in materials is required to enhance device performance. Lattice vibrations, a major contributor to heat transfer in solids, can be altered intrinsically or through external stimuli. However, altering phonons to manipulate the thermal conductivity is challenging due to their weak and complicated interactions with external fields. From inelastic neutron scattering experiments we have observed significant change in phonon scattering rates in [100]-poled (1-x)[Pb(Mg_1/3Nb_2/3)O₃]-xPbTiO₃(x = 30). The phonon linewidths are sharper in the direction of applied field than in the direction perpendicular to the poling, and this comes with a two times higher thermal conductivity along the poling direction. We argue that this decrease in phonon scattering with the application of electric field is caused by an observed suppression of antiferroelectric fluctuations at zone boundary M points in the direction of the electric field.