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Lead-free piezoelectric ceramics, with the nominal composition of 0.948 (K 0.5 Na 0.5) Nb O 3–0.052 Li Sb O 3 (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 (T O-T) temperature at approximately∼ 35 C⁠. The room temperature dielectric permittivity (ε 33 T∕ ε 0) and loss were found to be 1380 and 2%, respectively, with piezoelectric properties of k 33∼ 62% and d 33∼ 265 pC∕ N and k 31∼ 30% and d 31∼− 116 pC∕ N⁠. The temperature dependence of the properties mimicked the compositional variation seen in the proximity of a morphotropic phase boundary [eg, lead zirconate titanate (PZT)], with a maxima in the dielectric and …