Flexoelectric response of (1-x)BaTiO3-xSrTiO3 ceramics

The measured flexoelectric response of ferroelectric ceramics is usually several orders of magnitude larger than the theoretically calculated response, causing the controversy about the magnitude of the intrinsic response of flexoelectricity in the materials. In order to understand this issue, the temperature-dependent flexoelectric response of (1-x)BaTiO3-xSrTiO3 (BST) ceramics were measured. We show that near the Curie temperature (Tc), BST ceramics exhibit the highest flexoelectric response, which is much larger than the intrinsic response calculated theoretically. The response becomes lower at the temperature above or below Tc. The flexoelectric response that is consistent with the theoretical value can only be measured at a temperature much above Tc. Below Tc, the flexoelectric response is also much higher than the theoretical value because of the effect of some extrinsic mechanisms including the surface effect. Our study provides important experimental results to understand the mechanisms of flexoelectric response of ferroelectric ceramics and resolve the controversy about the magnitude of the intrinsic flexoelectric response of the materials.