Effects of low concentration BiFeO3 additions on microstructure and piezoelectric properties of (K0.5Na0.5)NbO3 ceramics

(1-x) K0.5Na0.5NbO3-x BiFeO3 lead-free piezoelectric ceramics were prepared by the conventional ceramic processing. The compositional dependence of the phase structure and the electrical properties of the ceramics were studied. A morphotropic phase boundary (MPB) between the orthorhombic and tetragonal phases was identified in the composition range of x = 0.01. The ceramics exhibit a strong compositional dependence and enhanced piezoelectric properties. The ceramics with 0.6 mol.% BF exhibit good electrical properties (d(33) similar to 146 pC/N, k(p) similar to 51%, T-c similar to 405 degrees C, To-t similar to 185 degrees C, epsilon(r) similar to 432, and tan theta similar to 4.60 %. The related mechanism of the enhanced electrical properties of the ceramics was also discussed. These results show that the air-sintered (1-x) KNN-x BF (0.006 < x < 0.01) ceramic is a promising lead-free piezoelectric material.