Fluorescence of Eu sup 3 sup + in lithium tungstate borate glasses

(Li sub 2 B sub 4 O sub 7 ) sub 9 sub 0 sub - sub x (WO sub 3 ) sub x (Eu sub 2 O sub 3 ) sub 1 glasses are investigated. Fluorescence of the sup 5 D sub 0 approaches sup 7 Fe sub 2 hypersensitive transition of Eu sup 3 sup + increases to x=20 at.%, probably due to the increasing dielectric inhomogeneity of the glass matrix and reduction of Eu nearest-neighbor distances. For x > 20 at.%, resonant energy transfer fluorescence quenching occurs, which is assisted by WO sub 3 clusters that tend to appear for higher WO sub 3 contents.