Fluorescence Line-Narrowing Study of Eu³⁺-Doped Sol−Gel Silica: Effect of Modifying Cations on the Clustering of Eu³⁺

Fluorescence line-narrowing spectroscopy is used to characterize the effect of metal cation codopants (Sr 2+, La 3+, Gd 3+, Y 3+, Lu 3+, Sc 3+, and Ga 3+ ) on the state of aggregation of Eu 3+ in sol−gel silica. Significant Eu 3+ clustering occurs in samples doped only with Eu 3+ . The addition of codopants inhibits the clustering of Eu 3+ and promotes better dispersion of Eu 3+ in the glasses. The extent of the inhibition of clustering increases with field strength of the codopant and levels off at high field strength. The inhibition of clustering is correlated with the generation of strong crystal field bonding sites for Eu 3+ in the presence of codopants. Characteristics of these sites include the presence of Eu−O−M (M = codopant) linkages and stronger interactions with the network-forming regions of the glass. Supporting luminescence decay and Raman spectroscopy measurements are also presented.