Studying the roles of Cu and Sb in K0.48Na0.52NbO3 lead-free piezoelectric ceramics

The co-effects of Sb and Cu on crystal structure and electrical performance of K0.48Na0.52NbO3 were studied by respective doping in the composition. The introduction of Cu2+ showed occupying B-site at low concentration and substituting on A-site at high concentration without inducing phase transformation. The mechanical quality factor (Qm) was enhanced with adding 1.5 mol% CuO content resulted from the formation of oxygen vacancies, and the degradation of piezoelectric constant (d33) and the increase of internal bias field (Ei) were attributed to the “hard doping effect”. Antimony was selected to successfully weaken the Ei and improve the piezoelectricity by “soft doping effect”. Meanwhile, the addition of Sb resulted in shifting rhombohedral-orthorhombic phase transition around to room temperature and the appearance of ferroelectric relaxor behavior. In this work, the “hard doping effect” and “soft doping effect” can be modulated and interacted by doping relevant elements.