Probing the diffusion behavior of polymorphic phase transition in K0.5Na0.5NbO3 ferroelectric ceramics by Eu3+ photoluminescence

By studying the temperature-induced structural transition in Eu3+-doped K0.5Na0.5NbO3 (KNN) ferroelectric ceramics, as well as the evolution of photoluminescence, dielectric, and ferroelectric properties, we find that the photoluminescence performance of the Eu3+ ions could be employed in ferroelectric ceramics as a probe to investigate the phase structure transition from the crystal symmetry view. The polymorphic orthorhombic-to-tetragonal phase transition region is found to belong to the diffusive phase transition, which is caused by the structural disorder and ferroelectric distortion in KNN host. Photoluminescence properties of the Eu3+ ions are discussed based on the Judd-Ofelt and crystallographic symmetry theories. These results show a potential strategy for studying the phase structural transitions in ferroelectric materials.