Improved piezoelectricity and high strain response of (1 − x)(0.948K_0.5Na_0.5NbO₃ − 0.052LiSbO₃) − xBi₂O₃ ceramics

(1 − x)(0.948K_0.5Na_0.5NbO₃ − 0.052LiSbO₃) − xBi₂O₃ (x = 0.001 ~ 0.004) (abbreviated as KNN − 5.2LS − xBi) lead-free piezoelectric ceramics were prepared using conventional solid sintering method and the effect of bismuth oxide (Bi₂O₃)-doping on phase structure, microstructure and electric properties were investigated. It was found that Bi₂O₃-doping induces a phase transition from the tetragonal phases to a pseudocubic phase with a normal-relaxor ferroelectric transformation, and acts as grain growth inhibitor, which significantly decreases the grain size of the ceramics. The KNN − 5.2LS ceramic with 0.2 mol. % Bi₂O₃ exhibited the optimum electrical properties (d ₃₃ = 229 pC/N, k _p = 31.08 %), together with a low T _O–T of 77 °C. In addition, the highest T _C (∼355 °C), the highest S _max (∼0.20 %) and d ₃₃* (∼392 pm/V) values can be attained in the ceramics with x = 0.001, which is superior to those of the previously reported KNN-based ceramics. These results show that the KNN − 5.2LS − xBi ceramic is one of the most promising candidates for replacing PZT-based ceramics.