On the local structure of Eu3+ ions in oxyfluoride glasses. Comparison with fluoride and oxide glasses

Broadband and fluorescence line narrowing optical spectroscopic studies hav e been used to investigate the local environments of Eu3+ ions in lithium f luoroborate glasses. From the vibronic spectra, different borate groups cou pled with the Eu3+ ions have been identified. A pulsed tunable dye laser ha s been used to selectively excite the D-5(0) level of the Eu3+ ion and the subsequent D-5(0)--> F-7(1) fluorescence spectra have been monitored as a f unction of the exciting wavelength. From these FLN studies, three F-7(1) St ark levels have been identified and a C-2v orthorhombic symmetry has been a ssumed in the subsequent calculation of the crystal-field parameters for th e different environments occupied by the Eu3+ ions in the glass. The second rank crystal-field parameters have been systematically analyzed for the Eu 3+:lithium fluoroborate glass from the site dependent behavior of the F-7(1 ) level splitting. The importance of the J-mixing in the crystal-field anal ysis has been emphasized. An appropriate method for comparing the crystal-f ield interactions in different glasses has been proposed by analyzing the F -7(1) level. Thus, results obtained for the Eu3+:fluoroborate have been com pared with recalculated results in other Eu3+ doped fluoride, borate, silic ate, and borosilicate glasses. An intermediate behavior between Eu3+:oxide and Eu3+:fluoride glasses is observed for the local structure of the Eu3+ i ons in the fluoroborate glass, indicating the active participation of fluor ine ions in the immediate environments of the lanthanide ion in this glass. (C) 2001 American Institute of Physics.