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 (Q(m)) and coercive field (E-c) increased with the addition of ZnO, indicating that ZnO acted as a hardener in the NKN ceramics. The dielectric constant (epsilon(3)(T)/epsilon(o)), piezoelectric constant (d(33)) and electromechanical coupling factor (k(p)) increased when a small amount of ZnO was added, which might be due to the increase in density. The good dielectric and piezoelectric proper-ties of epsilon(3)(T)/epsilon(o) = 500, d(33) = 121 and k(p) = 0.4 were obtained for the NKN ceramics with 1.0mol% ZnO.