• • Reduction-sintered BaTiO3−δ ceramics achieve an effective flexoelectric coefficient μeff > 50 mC m−1, exceeding the highest reported value by more than 25 times; this order-of-magnitude improvement enables practical flexoelectric devices that previously suffered from insufficient electromechanical coupling.
• • The flexoelectric piezoelectric metamaterial (FPM) design yields a giant effective piezoelectric coefficient d33 > 20000 pC N−1, a fivefold increase over the best conventional single crystals (d33 ≈ 4000 pC N−1), directly addressing the sensitivity bottleneck in actuators and transducers.
• • No depoling is observed above the Curie temperature of BaTiO3, eliminating the operational temperature ceiling that restricts conventional ferroelectrics to below TC; this permits high-temperature sensing and actuation in aerospace, automotive, and industrial process control environments.
• • The giant response originates from spontaneously polarized surface layers and a negative capacitance amplification effect caused by defect inhomogeneity (oxygen vacancies) formed during reduction sintering; this provides a defect-engineering pathway for enhancing properties without complex crystal growth or epitaxial deposition.