Improved piezoelectric and energy harvesting characteristics in lead-free Fe2O3 modified KNN ceramics

Abstract

Lead-free piezoelectric ceramics gained an increased attention due to their high piezoelectric properties combined with the absence of lead and other potentially hazardous elements. In this work, we used a unimorph cantilever beam arrangement to study piezoelectric energy harvesting in pristine K0.5Na0.5NbO3 (KNN) and Fe2O3 modified KNN (KNFN) ceramics that are potential candidates for PZT replacement. The piezoelectric ceramics were synthesized using conventional solid state reaction method. The KNFN ceramics exhibited a superior piezoelectric performance: d33 = 100 pC/N and mechanical quality factor (Qm = 135) as compared to KNN (d33 = 83 pC/N; Qm = 76). In addition, the planar electromechanical coupling factor kp was higher in case of KNFN having a value of 0.39 as compared to 0.34 for KNN. The KNFN harvester generated an output power of 0.38 mW/cm3 at a load resistance of 470 kΩ for a transverse displacement amplitude of 1.2 mm. The prospects of using lead-free ceramics for piezoelectric energy harvesting are discussed.