Influence of K/Na ratio on phase structure and electrical properties of 0.96 (KxNa1−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 (KxNa1−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., d33 = 275 pC/N, kp = 34.5 %, TC = 330 °C,Pr = 27.5 μC/cm2, and EC = 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.