Microstructure and piezoelectric properties of 0.95(Na0.5K0.5)NbO3-0.05BaTiO3 ceramics

For 0.95(Na0.5K0.5)NbO3-0.05BaTiO(3) (0.95NKN-0.05BT) ceramics sintered at 1040-1075 degrees C, abnormal grain growth occurred but the grain size decreased when the sintering temperature exceeded 1075 degrees C. The dielectric constant (epsilon(T)(3)/epsilon(3)), electromechanical coupling factor (k(p)), and piezoelectric constant (d(33)) were considerably increased with increasing relative density and grain size. Evaporation of Na2O deteriorated the piezoelectric properties by decreasing the resistivity. To minimize Na2O evaporation, specimens were muffled with 0.95NKN-0.05BT powders during the sintering. Improved piezoelectric properties of d(33)=225 pC/N, k(p)=36%, and epsilon(T)(3)/epsilon(3)=1058 were obtained for specimen sintered at 1060 degrees C for 2 h with muffling. (c) 2006 American Institute of Physics.