Optical absorption and photoluminescence studies of Eu3+-doped phosphate and fluorophosphate glasses

Phosphate (P2O5 + K2O + BaO + Al2O3 + Eu2O3) and fluorophosphate (P2O5 + K2O + BaO + BaF2 + Al2O3 + Eu2O3) glasses with different Eu3+ ion concentrations have been prepared and characterized through optical absorption, photoluminescence and decay times. An intense red luminescence is observed from the 5 Do emitting level of Eu3+ ions in these glasses. The relative luminescence intensity ratio of D-5(0) -> F-7(2) -> D-5(0) -> F-7(1) transitions has been evaluated to estimate the local site symmetry around the Eu3+ ions. The emission spectra of these glasses show a complete removal of degeneracy for the D-5(0) -> F-7(1) and D-5(0) -> F-7(2) transitions. Second and fourth rank crystal-field (CF) parameters have been calculated together with the CF strength parameter by assuming the C-2v symmetry for the EU3+ ions in both the phosphate and fluorophosphate glasses. Judd-Ofelt parameters have been evaluated from the luminescence intensity ratios of D-5(1) -> F-7(J) (J = 2, 4 and 6) to D-5(o) -> F-7(1) transitions. These parameters have been used to derive radiative properties such as transition probabilities, branching ratios, radiative lifetimes and peak stimulated emission cross-sections for the D-5(0) -> F-7(J) transitions. Decay curves of the D-5(0) level of EU3+ ions in these two EU3+ :glass systems have been measured by monitoring the D-5(0) -> F-7(2) transition (611 nm) at room temperature. The experimental lifetime of the Do level in the title glasses is found to be higher than Eu3+-doped niobium phosphate glasses. The analysis indicates that the lifetime of the 5 Do level is found to be less sensitive to the EU3+ ion concentration and addition of BaF2 has no significant effect on the optical properties of Eu3+-doped phosphate glasses. (C) 2006 Elsevier B.V. All rights reserved.