Dielectric and piezoelectric properties of CeO2-added nonstoichiometric (Na0.5K0.5)0.97(Nb0.96Sb0.04)O3 ceramics for piezoelectric energy harvesting device applications

In this study, nonstoichiometric (Na_0.5K_0.5)_0.97(Nb_0.96Sb_0.04)O₃ ceramics were fabricated and their dielectric and piezoelectric properties were investigated according to the CeO₂ addition. In this ceramic composition, CeO₂ addition improved sinterability, electromechanical coupling factor k_p, mechanical quality factor Q_m, piezoelectric constant d₃₃, and g₃₃. At the sintering temperature of 1100°C, for the 0.2wt% CeO₂ added specimen, the optimum values of density = 4.359 g/cm³, k_p = 0.443, Q_m = 588, ε_r = 444, d₃₃ = 159 pC/N, and g₃₃ = 35 × 10^¿3 V·m/N, were obtained. A piezoelectric energy harvesting device using 0.2wt% CeO₂- added lead-free (K_0.5Na_0.5)_0.97(Nb_0.96Sb_0.04)O₃ ceramics and a rectifying circuit for energy harvesting were fabricated and their electrical characteristics were investigated. Under an external vibration acceleration of 0.7g, when the mass, the frequency of vibration generator, and matching load resistance were 2.4 g, 70 Hz, and 721 Ω, respectively, output voltage and power of piezoelectric harvesting device indicated the optimum values of 24.6 mV_rms and 0.839 μW, respectively - suitable for application as the electric power source of a ubiquitous sensor network (USN) sensor node.