Pore-mediated multiscale regulation enables decoupled dielectric and piezoelectric responses in PZNNT ceramics

Abstract

To address the challenge of synergistically achieving a high piezoelectric voltage constant (g 33 ) and strong piezoelectric response at high porosity for highly sensitive piezoelectric sensors, three-dimensionally interconnected PZNNT porous piezoceramics with a porosity of 70%-90% were fabricated via a foam gel-casting technique. By tailoring the solid content, the pore structure, crystal structure, ferroelectric domain configuration, and defect states were synergistically regulated. Combined with multiscale structural characterization and finite-element simulations, the underlying mechanism responsible for the enhanced piezoelectric response was elucidated. The results demonstrate that the introduction of the air phase reduces the average dielectric constant from 2160 for the dense ceramic to 153, retaining only approximately 7% of its original value. Meanwhile, the continuous piezoelectric skeleton and pore-induced local strain fields synergistically regulate the crystal phases, ferroelectric domains, and polarization configuration, thereby effectively maintaining the polarization state and piezoelectric performance at high porosity. Consequently, an average of 478 pC/N was achieved, corresponding to 520 pC/N that of the dense ceramic, together with a high g 33 of 354 × 10 -3 V•m/N. The fabricated devices exhibited excellent voltage output characteristics, with a maximum voltage sensitivity of 42.6 V/kPa. This work provides a new materials strategy for the synergistic regulation of dielectric and piezoelectric properties in highly porous piezoelectric ceramics and the design of highly sensitive piezoelectric sensors.