Influence of K/Na ratio on phase structure and electrical properties of 0.96 (K x Na1-x ) NbO3-0.04 (Bi0.5Na0.5) ZrO3 lead-free ceramics

To investigate the influence of K/Na ratio on the phase structure and electrical properties, 0.96 (K (x) Na1-x ) NbO3-0.04 (Bi0.5Na0.5) ZrO3 lead-free piezoceramics with x = 0.35 0.60 were prepared by a conventional solid-state reaction method. The results indicate that a typical phase boundary of orthorhombic-tetragonal (O-T) exists at x = 0.39-0.55 by refining the K/Na ratio. The grain size of the ceramics becomes much larger as the K/Na increases, and the chemical compositions well keep in the ceramic matrix. The ceramics with x = 0.39 show enhanced electrical properties (e.g., d (33) = 275 pC/N, k (p) = 34.5 %, T (C) = 330 A degrees C,P (r) = 27.5 mu C/cm(2), and E (C) = 10.5 kV/cm). It is considered that the observed enhanced piezoelectricity should be ascribed to the phase coexistence of O and T phases of the ceramics.