Effects of A-Site Ionic Contents on Piezoelectric and Ferroelectric Properties of Lead-Free (K0.5Na0.5)NbO3-LiNbO3 Ceramics.

A-site non-stoichiometric lead-free 0.93(K0.5Na0.5)(1 + x)NbO3-0.07LiNbO3 (KNNL) piezoelectric ceramics were prepared by a solid state reaction. The contents of both K and Na were simultaneously controlled to -4 mol% deficient. The K3Li2Nb5O15 second phase was observed in most of the composition except for 0 mol%. The polymorphic phase transition (PPT) between the tetragonal and orthorhombic phases was found from X-ray diffraction and temperature-dependent dielectric constant at around -2 mol%. With increasing (K+Na) ion deficiency, the PPT temperature of KNNL ceramics increased but Curie temperature (TC) decreased. The piezoelectric constant was 155 pC/N for nominally stoichiometric KNNL and decreased as decreasing (K+Na) content. [ABSTRACT FROM AUTHOR]