Semiconductive flexoelectric piezoelectric metamaterials with strong electromechanical response

Piezoelectric materials are widely utilized in sensors, actuators, and transducers for electro-mechanical conversion. Conventional materials have limited piezoelectric response (piezoelectric coefficient d₃₃ < 4000 pC N⁻¹), as well as a mutual restriction between properties and working temperature. Our research demonstrates that the limitation and restriction can be removed by designing piezoelectric metamaterials based on flexoelectricity. We enhance the flexoelectric response of BaTiO₃ ceramics by 25 times compared with the highest reported results via reduction sintering. The BaTiO₃ piezoelectric metamaterials exhibit a large effective d₃₃ > 20000 pC N⁻¹ and no depoling above Curie temperature. The giant μ_eff is generated by spontaneously polarized surface layers and a negative capacitance amplification effect, caused by the defect inhomogeneity formed during sintering. These findings open up new possibilities for designing high-performance piezoelectric materials with extended working temperatures.