Structural and spectroscopic properties of LaOF:Eu3+ nanocrystals prepared by the sol-gel Pechini method.

A new method was used to obtain Eu(3+)-doped LaOF nanocrystals. The obtained nanocrystals were synthesized for the first time using a modified Pechini sol-gel method. The products were analyzed by X-ray powder diffraction and the Rietveld method. Optimal conditions for the synthesis were found. Luminescent properties of the tetragonal and rhombohedral LaOF:Eu(3+) nanocrystals were investigated by collecting excitation and luminescence spectra. The most effective dopant concentrations in both hosts were found. Luminescent lifetimes were also measured. The time-resolved luminescent traces showed both a growth and a decay, which pointed to energy transfer processes between Eu(3+) ions in the LaOF host. In order to explain these phenomena, an adequate mechanism has been proposed. Intensity parameters Ω(2), Ω(4) and quantum efficiencies were calculated using the Judd-Ofelt theory, allowing for an extensive study of the luminescent properties of Eu(3+) ion in the LaOF matrix.