Luminescence properties of Eu3+ ions in phosphate-based bioactive glasses

Eu2O3-doped phosphate-based bioactive glasses have been prepared by varying the calcium/potassium to phosphate ratio and their luminescence properties have been studied through absorption and emission spectra and decay rate analysis. Second and fourth rank crystal-field (CF) parameters and the CF strength parameters have been calculated by assuming the C-2V symmetry for Eu3+ ions in the present glasses. Judd-Ofelt analysis has been used to derive radiative properties such as transition probabilities, branching ratios, radiative lifetimes and peak-stimulated emission cross-sections for D-5(0) -> F-7(J) (J = 0-4) transitions. The relative luminescence intensity ratio of D-5(0) -> F-7(2) and D-5(0) -> F-7(1) transitions has been evaluated to estimate the local site symmetry around Eu3+ ions. The observed D-5(0) -> F-7(0) transition for higher calcium content indicates two distinct sites for Eu3+ ion. Decay rates for the D-5(0) level of Eu3+ ions in these glasses have been measured by monitoring the D-5(0) -> F-7(2) transition. The lifetimes of the D-5(0) level are found to decrease with increase in calcium contents. (C) 2011 Elsevier Masson SAS. All rights reserved.