Tuning the fluorescence of Dy3+ via the structure of borophosphate glasses

Abstract

The optical characteristics of Dy³⁺-doped phosphate and borophosphate glasses with different divalent network modifiers prepared by melt-quenching are studied. The glass sets (A) with a molar composition of 40MO-60P₂O₅ and (B) with a molar composition of 40MO-20B₂O₃-40 P₂O₅ are investigated, both with M = (Zn²⁺, Mg²⁺, Ca²⁺, Sr²⁺, or Ba²⁺) and all doped with 0.1 mol% Dy₂O₃. Raman and fluorescence spectroscopy are used to analyse the structure and optical characteristics of these glasses. Four typical Dy³⁺ emission bands in the yellow (572 nm), blue (483 nm) and red (633 and 752 nm) regions of the spectrum are observed in both sets. The fluorescence lifetimes in each glass set are correlated to the network modifier's ionic field strength. The Mg²⁺ and Zn²⁺ containing glasses have the longest fluorescence lifetimes. The yellow to blue emission intensity ratio of the respective bands can be used to indicate a symmetric environment around Dy³⁺ ions and varies with the ionic field strength of the modifier cations: a higher ionic field strength leads to a higher yellow to blue ratio, which in turn indicates a higher asymmetrical local coordination environment of Dy³⁺ ions in the glassy host network.