Dielectric and piezoelectric properties of ZnO and SnO2 co-doping K0.5Na0.5Nbo3 ceramics

A series of (1−x)K0.5Na0.5NbO3−x(ZnO and SnO2) ceramics were prepared by solid state reaction method and their structures, dielectric and piezoelectric properties were investigated. All samples show pure perovskite phase with typical orthorhombic symmetry at x≤0.6%. However, a trace amount of ZnSnO3 was detected at x≥0.8%, in addition to the ZnSnO3, some Zn2SnO4 and SnO2 were presented at x≥1.0%. The phase transition temperature of orthorhombic–tetragonal (TO−T) and tetragonal–cubic (Tc), the remnant polarization (Pr) and the coercive field (Ec) decreased with increasing x. The dielectric constant (εr), piezoelectric constant (d33) and electromechanical coupling factor (kp) increased with increasing x until x=0.8%, and then decreased with further increasing x. And the optimum piezoelectric properties of εr=503, d33=124 pC/N and kp=0.398 were obtained. The increase in piezoelectric properties might be due to the increase in density and ZnSnO3 doping.