To date, most of the reported piezoelectric energy harvesters (PEHs) use lead-based Pb(Zr,Ti)O₃ (PZT) piezoceramic family, which is obviously harmful to the environment. In recent years, the PEHs constructed with lead-free piezoceramics have been developed rapidly. However, their force-to-electric (F–E) output performances are still unsatisfactory. To address this issue, here we present a PEH assembled with lead-free potassium sodium niobate (KNN) based co-fired multilayered piezoceramics (MLPCs), which show a high output current and power. First, high-quality KNN-based MLPCs are prepared by tape-casting process. Each MLPC contains 11 piezoceramic layers, and the cross-section SEM image of the MLPC indicates that the ceramic layers are well connected with the Ag/Pd inner electrode layers. The d₃₃ of a single MLPC reaches up to 4675 pC/N. The F–E output performance of KNN-MLPC based PEH is then tested. The inherent advantages of multilayered ceramics enable the PEH to achieve a peak-to-peak output current of up to 1.48 mA and a peak-to-peak output power of 2.19 mW under a harmonic force load of 6 kN at 14 Hz. Finally, the PEH is tested to validate its practical application in real road environments, demonstrating its promising for the use of self-powered monitoring sensors for collecting traffic data.

Piezoelectric PZT ceramics with high piezoelectric properties and good thermal stability are urgently desired concerning the practical application. New compositions of LiNbO₃ modified Pb(Ni_1/3Nb_2/3)O₃PbZrO₃PbTiO₃ ceramics have been prepared in this study. The effects of the introduction of the LiNbO₃ on the system were comprehensively investigated in terms of the phase structure, microstructure, electric properties, and thermal stability behavior of the ceramics. All compositions are located in the morphotropic phase boundary (MPB) region, and the ratio of the rhombohedral (R) phase increases obviously with the increase of LiNbO₃ concentration. With increasing the LiNbO₃ content, the piezoelectric properties were significantly enhanced. The sample added with 2% (in mole) LiNbO₃ shows excellent electric properties, including T_m = 185 ℃, ε_r= 5,643, k_p = 0.626, Q_m = 51, d₃₃ = 902 pC/N. More importantly, no thermal depolarization behavior was observed in the temperature range of 25–100 ℃. For PNN-PZT-x%LN ceramics, which is mainly attributed to the pinning effect resulted by the (Li'_Pb - Nb_Zr=Ti^·) defect dipoles.