Ultrahigh Piezoelectricity in Truss‐Based Ferroelectric Ceramics Metamaterials

Abstract Conventional porous ferroelectric materials sacrifice their piezoelectric constants for improving various figures of merit due to a rapidly decreased dielectric constant. Here, novel truss‐based ferroelectric metamaterials that simultaneously offer ultrahigh piezoelectric constants and ultralow dielectric constants, originating from the unique combination of truss loading states and polarization direction, are discovered. The homogenization method alongside an analytical model is proposed to predict and elucidate their extraordinary properties, while a customized ferroceramic additive manufacturing platform is resorted to fabricate them. Unlike porous ferroelectrics, ultrahigh piezoelectric constants at low relative densities ( ρ _r ≈0.1) are attained. For example, with appropriate scaling, the experimental values of d ₃₁ , d ₃₃ , and d ₄₂ for a ferroelectric octet truss with ρ _r = 0.1, can reach 849, −659, and 836 pC N ⁻¹ , respectively, which are 3.14, 6, and 2 times higher than the counterpart of bulk BaTiO ₃ ceramics. Combined with the ultralow dielectric constant, extremely high ferroelectric figures of merit, e.g., piezoelectric voltage constant of 11.098 Vm N ⁻¹ , piezoelectric energy harvesting figure of merit 9422 × 10 ⁻¹² m ² N ⁻¹ , and pyroelectric voltage sensitivity of 56.7 × 10 ⁻³ m ² C ⁻¹ , are also observed. The multifunctional ferroelectric metamaterials open new avenues for their applications in self‐powered ultrasensitive accelerometers, high‐performance noncontact sensors, and wearable input devices.