High-sensitivity piezoelectric response enabled by heterogeneous stress–electric field distribution in 3D interconnected porous ceramics

Porous piezoceramics are attractive for high-sensitivity sensing and energy conversion due to their low density, reduced dielectric constant (ε_r), and good mechanical compliance. However, increasing porosity is often accompanied by a significant reduction in the piezoelectric charge coefficient (d₃₃), creating an intrinsic trade-off that limits the practical use of porous structures in high-sensitivity piezoelectric devices and leaves their overall performance advantages under debate. In this work, we overcome this challenge by developing a fully open-cell, three-dimensionally interconnected PZT-PZN-PNN porous piezoceramic (3D-PPC). Despite an ultrahigh porosity of 92%, the material maintains a high d₃₃ of ~470 pC N⁻¹, about 90% of that of the dense ceramic. While its effective ε_r is reduced to ~140 (a 94% decrease), leading to an approximately 14-fold enhancement in the piezoelectric voltage constant g₃₃ (~380 × 10^-3 Vm/N). Combined microstructural characterization, domain analysis, defect studies, and multiphysics simulations show that the exceptional performance arises from synergistic effects of heterogeneous stress and electric fields, multiscale domain structures, and defect-mediated regulation within the three-dimensionally interconnected porous architecture. Finally, the material generates peak output voltages up to 200 V under subtle mechanical excitation and achieves an ultrahigh sensitivity of 38.7 V/kPa. These results show that three-dimensionally interconnected porous architectures are not merely passive means of reducing dielectric permittivity, but active structural strategies for tuning local fields and polarization behavior.