Lead-free piezoelectric ceramics, with the nominal composition of 0.948(K0.5Na0.5)NbO3–0.052LiSbO3 (KNN-LS5.2), were synthesized by conventional solid-state sintering, and the piezoelectric and electromechanical properties were characterized as a function of temperature. The Curie temperature of the KNN based perovskite material was found to be 368°C with an orthorhombic-tetragonal polymorphic phase transition (TO-T) temperature at approximately ∼35°C. The room temperature dielectric permittivity (ε33T∕ε0) and loss were found to be 1380 and 2%, respectively, with piezoelectric properties of k33∼62% and d33∼265pC∕N and k31∼30% and d31∼−116pC∕N. The temperature dependence of the properties mimicked the compositional variation seen in the proximity of a morphotropic phase boundary [e.g., lead zirconate titanate (PZT)], with a maxima in the dielectric and piezoelectric properties and a corresponding “softening” of the elastic properties. Unlike that found for PZT-type materials, the modified KNN material exhibited characteristics of both “soft” and “hard” piezoelectricities owing to the distinctly different domain states associated with orthorhombic and tetragonal phases.

Piezoelectric properties in perovskite 0.948(K0.5Na0.5)NbO3–0.052LiSbO3 lead-free ceramics