Cavitation-eroded piezoelectric ceramics as finite mechano-electrochemical transducers

Piezoelectric ceramics are being explored as mechanically powered materials for energy-environmental processes, but the relationship between energy transduction and material durability remains unclear. We examined four piezoelectric materials (BaTiO₃, ZnO, K_0.5Na_0.5NbO₃, and PbZr_0.53Ti_0.47O₃) under 40 kHz ultrasonic cavitation. The pressure criterion for reactive oxygen species (ROS) formation through water compression (2.8-8.1 GPa) exceeded the 1.13 GPa compressed-bubble pressure obtained from the bubble-collapse calculation. The electron-energy analysis provides a thermal-equilibrium reference rather than a prediction of plasma-derived ROS yields. The powder-free control showed only 0.7% and 1.9% tetracycline (TC) removal after 120 and 480 min, respectively. The open-circuit piezoelectric potentials calculated for 1 μm particles at the 1.13 GPa compressed-bubble pressure (9-210 V) exceeded the electrochemical thresholds (0.33-2.8 V), and the powders showed persistent contact-potential shifts up to - 318 mV and charge storage 32-55 times beyond the electrical double-layer limit. Cavitation-induced irreversible lattice strain and selective A-site ion leaching were accompanied by elbow-shaped TC degradation kinetics with performance declining from approximately 67% to 1-3% over five cycles. Mott-Schottky and impedance analyses indicated that interfacial electrochemical states were irreversibly altered. The tested powders are described here as finite mechano-electrochemical transducers whose operation is accompanied by irreversible material changes and declining activity. The relevant design criterion for sustainable piezoelectric environmental applications should include redox output, material lifetime, recoverability, and ion-release risk as well as the first-cycle activity.