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

For 0.95(Na_0.5K_0.5)NbO₃-0.05Ba_{TiO3 (0.95NKN-0.05BT) ceramics sintered at 1040-1075°C, abnormal grain growth occurred but the grain size decreased when the sintering temperature exceeded 1075°C. The dielectric constant (ɛ3^T/ɛ3), electromechanical coupling factor (kp), and piezoelectric constant (d33}) 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 d₃₃=225pC/N, k_p=36%, and ɛ₃^{T_/ɛ3=1058 were obtained for specimen sintered at 1060°C for 2h with muffling.}