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 (d33 ～146 pC/N, kp ～51%, Tc ～405°C, To-t ～185 °C, er ～432, and tan θ～ 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