Origin of large intrinsic flexoelectric coefficients near curie temperature of BaTiO₃

Large effective flexoelectric coefficients have been experimentally obtained near the Curie temperature of many ferroelectric materials, which could greatly accelerate applications of flexoelectricity on actuators and sensors. However, it is still unclear why ferroelectric materials exhibit largest flexoelectric coefficient near their Curie temperatures. Here we employ a modified phenomenological Landau theory to estimate the intrinsic flexoelectric coefficient of BaTiO₃ near Curie temperature. It is found that the intrinsic flexoelectric coefficients is largest and reach 1.3 μC/m at T_C of its paraelectric phase. The large intrinsic flexoelectric coefficient of paraelectric BaTiO₃ is found to correlate with the strong lattice instability of paraelectric phase near T_C. This work could help unravel the origin of the large flexoelectric coefficients near T_C of ferroelectric materials and would stimulate new research interest into designing ferroelectric materials with high flexoelectric coefficients utilizing phase transitions.