Flexure mode flexoelectric piezoelectric composites

We present a flexure mode composite design to generate steep transverse strain gradient to exploit large flexoelectric coefficient ${\mu }_{1122}$ of $\left(\text{Ba},\text{Sr}\right){\text{TiO}}_3$ (BST) ceramics. Very strong direct piezoelectric effect was observed in composites due to the flexoelectricity. In a single unit composite, sharp low frequency $\left(<300\text{Hz}\right)$ mechanical resonance leads to high effective $d_{33}>2000\text{pC}/\text{N}$ as the result of enhancement of strain gradient at resonance. Giant nonresonance $d_{33}$ well beyond piezoelectric single crystal about 4350 pC/N was measured at a temperature around Curie temperature of BST ceramic in a six unit three layer composite.