Influence of tungsten on the emission features of Nd 3+, Sm 3+ and Eu 3+ ions in ZnF 2–WO 3–TeO 2 glasses

Abstract

The glasses of the composition (45− x)ZnF 2– xWO 3–49TeO 2:1.0Nd 2O 3/Sm 2O 3/Eu 2O 3 with x varying from 5 to 20 mol% were synthesized. Optical absorption, fluorescence spectra (in the spectral range 400–2300 nm) and also fluorescence decay were studied at ambient temperature. The Judd–Ofelt theory analysis was applied to characterize the absorption and luminescence spectra of Ln 3+ ions in these glasses. Following the luminescence spectra, various radiative properties like transition probability A, branching ratio β and the radiative life time τ for 4F 3/2 → 4I 11/2, 4G 5/2 → 6H 7/2, 5D 0 → 7F 2 emission levels respectively for Nd 3+, Sm 3+ and Eu 3+ doped glasses of these glasses have been evaluated. The variations observed in these parameters were discussed following of varying co-ordinations (tetrahedral and octahedral positions) and the valence states of tungsten ions in the glass network. A significant enhancement in the intensities of 4F 3/2 → 4I 11/2 (Nd 3+), 4G 5/2 → 6H 7/2 (Sm 3+) and 5D 0 → 7F 2 (Eu 3+) emission lines has been observed with increase of WO 3 content; this is attributed to the increase in the concentration W 5+ ions in the glass network that acts as modifiers. The quantitative analysis of these results (with the aid of the data on ESR, IR and Raman spectral studies) has indicated that the glasses mixed with around 15 mol% of WO 3 have the optimum concentration for yielding the highest quantum efficiency with low phonon losses for the above-mentioned principal transitions.