Improvement of (K, Na) NbO3-based lead-free piezoelectric ceramics by asymmetric octahedra

摘要

Due to their excellent piezoelectric properties, including a coupling factor k(p) = 0.55, dielectric constant epsilon(T)(33)/epsilon(0) = 2725, piezoelectric constant d(33) = 375 pC N-1, Q(m) = 60, and dielectric tan delta = 1.87%, 0.891( K0.37Na0.63)(0.86)Ca0.04Li0.02Nb0.85O3-delta-0.041K(0.85)Ti(0.85)Nb(1.15)O(5)-0.055BaZrO(3)-0.0016Co(3)O(4)-0.0025Fe(2)O(3)-0.0069ZnO ceramic without Ta, Sb, Bi, or Hf is promising as a lead-free piezoelectric ceramic. In this system, a solid solution of BaZrO3 into (K0.37Na0.63)(0.86)Ca0.04Li0.02Nb0.85O3-(delta) effectively contributes to both the piezoelectric properties and the stability around room temperature. The solid solution of BaZrO3 induces asymmetry in the BO6 octahedra in the c-axis direction, improving kp, steeply increasing epsilon(T)(33)/epsilon(0) at room temperature, while reducing the temperature dependence of epsilon(T)(33)/epsilon(0).