Non-Stoichiometric Effect in (K,Na)NbO₃-Based Perovskite Ceramics

Abstract

We prepared Li0.04(K0.5Na0.5) x (Nb y Sb0.06)O3 ceramics using the conventional solid-state sintering method and investigated the non-stoichiometric effect on sintering behavior and electrical properties in these material systems. The deficiency of B-site ions gave rise to poor densities, while the densification was improved by adding excess Nb2O5. As the vacancy concentration in the A-site of the perovskite structure increased, the diffuse phase transition was enhanced and the transition temperature (T o–t) was lowered. Furthermore, high deficiency in the A-site with x=0.90 and y=0.98 promoted a second phase formation. An increase of alkali cation vacancies led to large remnant polarization and enhanced a pinched hysteresis loop, while the remnant polarization decreased due to a second phase formation. The electro-mechanical coupling factors were significantly influenced by density and second phase formation, not non-stoichiometry, while dielectric constants were influenced by non-stoichiometry, not second phase formation.