Energy transfer between Eu3+ ions in sol-gel derived silica glasses

Time-resolved fluorescence line narrowing technique has been used to analyse the evolution of the D-5(0)--> F-7(0) emission of Eu3+ ions in sol-gel derived silica glasses. These samples were doped with 2.5 mol% of Eu3+ and heat treated at different temperatures. Background fluorescence, coming from Eu3+ ions excited by energy transfer processes, was observed in these experiments. Using a previously proposed equation model, a study of the multipole character of the interaction between Eu3+ ions was performed. The annealing process carried out in the samples causes important changes in the efficiency of energy transfer process and in its multipole character, varying from S = 6 (in a sample treated at 400 degreesC) to S = 10 (in a sample treated at 600 degreesC), indicating that the environment of Eu3+ ions has been modified. (C) 2001 Elsevier Science B.V. All rights reserved.