FLUORESCENCE-SPECTRA OF EU(II) IN BORATE AND ALUMINATE GLASSES

The fluorescence and Eu-151 Mossbauer spectra have been obtained for alkali borate, alkaline earth borate and rare-earth aluminate glasses containing Eu2+ ions. The Mossbauer spectra indicate that about 70 to 80% of the europium ions are present as Eu2+ ions in the borate glasses. As for the aluminate glasses, almost all of the europium ions are present as Eu2+ ions. The fluorescence spectra due to the 4f(6)5d1-->4f7 transition of the Eu2+ ion have been observed under excitation with UV radiation. There exists an empirical relationship that the emission energy decreases monotonically with an increase in the theoretical optical basicity of glass, irrespective of the glass systems. This relationship is explained in terms of simple crystal field theory by assuming that the splitting of the 5d levels mainly determines the emission energy of the Eu2+ ions. This empirical relationship also indicates that Eu2+ ions are distributed rather homogeneously in the present borate and aluminate glasses.