Structure and electrical properties' investigation of (K0.5Na0.5)NbO3-(Bi0.5Na0.5)TiO3 lead-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 deg. 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