Hardening characteristics and compositional dependence of piezoelectric properties in Cu2+ modified 0.52NaNbO3-(0.48 − x)KNbO3-xLiNbO3 ceramics

The phase transition and compositional dependence of piezoelectric properties were investigated for ternary lead-free NaNbO3-KNbO3-LiNbO3 system where Li+ is solely substituted for K+. An orthorhombic-tetragonal phase transition near room temperature was identified when 2-4 mol% K+ was replaced by Li+. The hardening behavior of piezoelectric properties was induced by adding a few amount of CuO, but remarkably influenced by the content of Li+ in the composition. Mechanisms concerning the phase transition diffuseness, grain morphology and defect dipoles were discussed in combination with the variation of electrical properties.