Microstructure and Piezoelectric Properties of ZnO-added (Na0.5K0.5)NbO3 Ceramics

The orthorhombic structure of (Na0.5K0.5)NbO3 (NKN) ceramics was maintained when ZnO was added. NKN ceramics have a porous microstructure and dissolve when they are exposed to water. However, as ZnO was added, a dense microstructure was developed and deliquescence was not observed. The mechanical quality factor (Qm) and coercive field (Ec) increased with the addition of ZnO, indicating that ZnO acted as a hardener in the NKN ceramics. The dielectric constant (eT3/eo), piezoelectric constant (d33) and electromechanical coupling factor (kp) increased when a small amount of ZnO was added, which might be due to the increase in density. The good dielectric and piezoelectric properties of eT3/eo = 500, d33 = 121 and kp=0.4 were obtained for the NKN ceramics with 1.0 mol% ZnO.