Wide visible-range fluorescence of Eu³⁺ located in the macroscopic bi-layer ceramic/glass composite

The Eu³⁺doped fluoride bi-layer ceramic/glass composite (GC_ZBL-Eu) was prepared by a one-step method and the effective wide visible-range fluorescence was recorded. The de-population rates of the⁵D₀⁵D₁⁵D₂, and⁵D₃multi-levels in the glass layer (G_ZBL-Eu) were estimated to be 214, 746, 1163, and 680 s^-1, respectively, and that in the ceramic layer (C_ZBL-Eu) were 211, 730, 1075, and 654 s^-1, which implies multi-channel radiative transitions due to the non-radiative relaxation limitation of low OH content and low phonon energy. Simultaneously, the quantum efficiencies of the⁵D₀levels in G_ZBL-Eu and C_ZBL-Eu were as high as 98.5% and 94.8%, respectively, thus demonstrating the effectiveness of the radiative transition emissions from Eu³⁺. Besides, GC_ZBL-Eu with the glass forming layer increases the emission intensity by 24% compared to C_ZBL-Eu, which is attributed to the multiple-cycle reflection in the composite structure of the glass-ceramic transition region, and the color coordinates of C_ZBL-Eu (0.483, 0.385) and GC_ZBL-Eu (0.469, 0.389) show that they can release yellowish-white light. The hetero-structured GC_ZBL-Eu provides a new approach for laser lighting, fluorescent display, and up-conversion applications.