Investigation of Eu3+ luminescence enhancement in LaOF powders codoped with Tb3+ and prepared by combustion synthesis

Lanthanum oxyfluoride (LaOF) nanocrystalline powders doped with Eu3+, Tb3+ and co-doped with both rare-earth elements were prepared by combustion synthesis. Surface morphology and structure of the powders were investigated by scanning electronic microscopy and X-ray powder diffraction. Luminescence experiments were performed with ultraviolet light (lambda = 254 nm and 355 nm). On the basis of the analysis of the luminescence spectra, these powders display the characteristic 4f-4f emissions of Tb3+ and Eu3+ ions with the most intense emission lines being D-5(4)-> F-7(5) (541 nm) from Tb3+ and D-5(0) -> F-7(2) (612 nm) from Eu3+. It was observed an enhancement of the red emission at 612 nm from Eu3+ ions in co-doped samples. From the analysis of Tb3+ emission decay curves it is deduced that Tb3+ transfers energy to Eu3+. The energy transfer mechanism was found to be of a resonant type via a dipole-dipole mechanism. The energy transfer efficiency and the critical transfer distance were estimated by the luminescence dynamics analysis. (C) 2014 Elsevier B.V. All rights reserved.