Structural and spectroscopic analyses of europium doped yttrium oxyfluoride powders prepared by combustion synthesis

A facile widely spread technique employed to produce low-cost high-yield oxide powders, combustion synthesis, was used to prepare yttrium oxyfluoride crystalline ceramic powders. The structure of the powders was analyzed by X-ray powder diffraction and Rietveld refinement. Samples heat treated at 700°C had a predominance of vernier orthorhombic Y₆O₅F ₈ phase, while samples heat treated at 800°C crystallized in stoichiometric rhombohedral YOF phase. The samples were doped with luminescent europium trivalent ions (Eu³⁺) in different concentrations (1-15 wt.%) and Judd-Ofelt theory was used to probe the distortion from the inversion symmetry of the local crystal field and the degree of covalency between the rare-earth ion and the surrounding ligands. The luminescence lifetime was measured and the luminescence quantum efficiency (LQE) was estimated. We observed that Eu³⁺:Y₆O₅F₈ samples presented higher LQE in spite of the larger local crystal field anisotropy found for Eu³⁺:YOF samples.