Optimized piezoelectric and structural properties of (Bi,Na)TiO3-(Bi,K)TiO3 ceramics for energy harvester applications

We investigated (1−x)(Bi,Na)TiO3-x(Bi,K)TiO3 (x=0, 0.14, 0.16, 0.18, 0.20, and 0.22) compositions of lead-free piezoelectric ceramics for potential energy harvester applications. Composition and sintering temperature of (1−x)(Bi,Na)TiO3-x(Bi,K)TiO3 were varied to extract the optimized processing temperature with each composition. We compared and analyzed sintering temperature-dependent surface morphologies and electrical properties. Maximum piezoelectric charge constant of 180 pC/N were obtained from the 0.8(Bi,Na)TiO3-0.2(Bi,K)TiO3composition at the sintering temperature of 1180 °C. Temperature dependent dielectric permittivity was measured to know the phase transition. We corresponded two different anomaly peaks, observed at 84 and 290 °C, as the rhombohedral-tetragonal and tetragonal-cubic phase transitions, respectively. Due to these phase transitions, different shapes of polarization-electric field loops (P-E loops) were measured and compared. Finally, output power of 42.39 nW/cm2 were obtained for the (1−x)(Bi,Na)TiO3-x(Bi,K)TiO3 lead free piezoelectric ceramics.