Synthesis and Structural Probing of Eu³⁺ Doped BaYF₅ Nano-Crystals in Transparent Oxyfluoride Glass-Ceramics

Transparent oxyfluoride glass-ceramics containing Eu:BaYF₅ nano-crystals in the newly developed SiO₂–K₂CO₃–BaF₂–YF₃–Sb₂O₃ glass system are synthesized by melt quenching method followed by optimized ceramization process. The X-ray diffraction, transmission electron microscopy, and field emission scanning electron microscopy confirmed the precipitation of tetragonal BaYF₅ nano-crystals in glass matrix. The coexistence of Eu²⁺ and Eu³⁺ ions in both glass and glass-ceramics are ascertained from their emission and excitation spectra. The in situ formation of divalent europium (Eu²⁺) along with Eu³⁺ during high temperature synthesis under ambient atmosphere is explained through optical basicity model. The Eu³⁺ emission from upper excitation states (⁵D₃₋₁) and reduced asymmetry ratio (R = I_ED/I_MD) in glass-ceramics have established the dopant ion incorporation into fluoride nano-crystalline environment. The observed luminescence properties of Eu:BaYF₅ are compared with that of Eu:BaYF₅ nanocrystals containing transparent glass-ceramics and their marked differences are discussed.