Microstructure and Electrical Properties of Eu-Doped K0.5Na0.5NbO3 Ceramics

(K0.5Na0.5)(1-3x)EuxNbO3 (0 <= x <= 0.05) lead-free ceramics have been prepared by a conventional solid state reaction. XRD show that the ceramics possess a pure perovskite structure with orthorhombic symmetry. Dopant Eu restrains the grain growth, decreases the ferroelectric-paraelectric phase transition temperature and leads to a diffuse phase transition. With the increase of Eu, the observed remanent polarization (Pr) decreases while the coercive field (E-c) remains almost unchanged. Nevertheless, for the increase in relative permittivity, the sample with x = 0.005 exhibits the optimum piezoelectric properties, giving a large piezoelectric coefficient (d(33) = 121 pC/N) and a high planar electromechanical coupling coefficient (kp D 0.41).