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

• Luminescence enhancement of Eu3+ was observed due to the presence of Tb3+.
• The Tb3+ → Eu3+ energy transfer process was investigated in LaOF powders.
• The energy transfer efficiency and the critical transfer distance were estimated.

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 (λ = 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 5D4 → 7F5 (541 nm) from Tb3+ and 5D0 → 7F2 (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.