Boosting Piezoelectric Voltage Constant in 3D-Interconnected PZNNT Porous Piezoceramics via Pore Architecture Engineering

In conventional piezoceramics, the coordinated change between the dielectric constant (ε_r) and the piezoelectric charge constant (d₃₃) usually limits the piezoelectric voltage constant g₃₃ (g₃₃ = d₃₃/ε_r), a critical figure of merit for piezoelectric sensors. In porous piezoceramics (PPCs), air as a secondary phase reduces ε_r, whereas controlling 3-dimensional (3D) pore structure through processing can enhance ceramic skeleton connectivity, thereby benefiting d₃₃ and enabling the decoupling of electrical parameters. In this work, we fabricate PPCs of PZT-PZN-PNN (PZNNT) via the gel-casting method with varying solid contents. The 5-vol% PZNNT 3D-PPC realizes an 84.5% sharp reduction in ε_r and a 55.2% retention of d₃₃ that synergistically elevates g₃₃ to 99.7 × 10⁻³ Vm N⁻¹, which is 3.7 times that of dense ceramic. Experimental and simulation results confirm that the low stiffness and large deformations of porous materials enable both stress absorption and amplification, thereby enhancing the electromechanical conversion efficiency of piezoelectric materials. Ultimately, the fabricated 3D porous piezoceramic demonstrates exceptional electrical output and sensitivity, whereas its low density and acoustic impedance synergistically position it as a highly competitive candidate for hydrophone and sensor applications.