PHASE STRUCTURE, PIEZOELECTRIC AND MULTIFERRIOC BEHAVIOR OF (K0.48Na0.52) NbO3-Co2O3 PIEZOELECTRIC CERAMICS

(K0.48Na0.52) NbO3-x%Co2O3 (x = 0, 0.03 and 0.05) (KNN-x%Co2O3) lead-free piezoelectric ceramics were prepared by the conventional solid-state sintering method. An orthorhombic phase was observed for all KNN-x%Co2O3 ceramics at room temperature, and two phase transitions were confirmed by the high temperature X-ray diffraction and the temperature dependence of the dielectric constant. The Co2O3 greatly improves the density and decreases the sintering temperature of KNN ceramics. The KNN-0.05 mol%Co2O3 ceramic exhibits good properties (d(33) = 120 pC/N, k(p) = 0: 41, Q(m) = 213 and T-c = 407 degrees C) and a good age stability. The multiferroic behavior was also observed at room temperature for the KNN-0.05 mol%Co2O3 ceramic, as confirmed by P-E loops and magnetic behavior.