Synthesis and Characterization of Eu-Doped (K0.5Na0.5)NbO3 Ceramics with Enhanced Ferroelectric, Photochromic, and Luminescent Properties

Abstract

The presence of secondary phases in rare-earth ion-doped potassium sodium niobate ((K_0.5Na_0.5)NbO₃, KNN) ceramics limit its electronic applications. To address this limitation, we investigated the electronic and luminescence properties of Eu³⁺-doped KNN (KNEN) ceramics. We synthesized a high-purity perovskite phase of KNEN without secondary phases by carefully adjusting the Na and K concentrations with 1 mol% Eu. KNEN ceramics demonstrated excellent ferroelectric and luminescent properties, including a photochromic effect that presented reversible color changes on exposure to ultraviolet light and X-rays. Further, we observed a strong correlation between the electric and luminescent properties near the orthorhombic-tetragonal phase transition at ~200 °C. These results suggest that KNEN ceramics are promising Pb-free luminescent piezoelectric materials.