Structure and electrical properties' investigation of (K0.5Na0.5)NbO₃–(Bi0.5Na0.5)TiO₃lead-free piezoelectric ceramics

Lead-free piezoelectric ceramics (1 − x)(K0.5Na0.5)NbO3–x(Bi0.5Na0.5)TiO3 [(1 − x)KNN–xBNT] were synthesized by conventional solid-state sintering. The phase structure and electrical properties of (1 − x)KNN–xBNT ceramics are investigated. The polymorphic phase transition (from the orthorhombic to the tetragonal phase) (PPT) plays a very important role in (1 −x)KNN–xBNT ceramics. A PPT at room temperature in (1 − x)KNN–xBNT ceramics is identified for 0.02 < x ≤ 0.03. The (1 − x)KNN–xBNT (x = 0.025) ceramics show optimum electrical properties (d33 256 pC N−1, d31 = 85 pC N−1, kp = 0.48, kt = 0.52 and TC = 373 °C). The related mechanisms for high piezoelectric properties in (1 − x)KNN–xBNT (x = 0.025) ceramics are also discussed. These results indicate that the (1 − x)KNN–xBNT (x = 0.025) ceramic is a promising lead-free piezoelectric candidate material.