Microstructure, electrical properties of CeO₂-doped (K_0.5Na_0.5)NbO₃lead-free piezoelectric ceramics

CeO2-doped K0.5Na0.5NbO3lead-free piezoelectric ceramics have been fabricated by a conventional ceramic fabrication technique. The ceramics retain the orthorhombic perovskite structure at low doping levels (<1 mol.%). Our results also demonstrate that the Ce-doping can suppress the grain growth, promote the densification, decrease the ferroelectric-paraelectric phase transition temperature (TC), and improve the dielectric and piezoelectric properties. For the ceramic doped with 0.75 mol.% CeO2, the dielectric and piezoelectric properties become optimum: piezoelectric coefficient d33= 130 pC/N, planar electromechanical coupling coefficient kp= 0.38, relative permittivity εr= 820, and loss tangent tanδ = 3%.