Optical and site-selective spectral studies of Eu3+-doped zinc oxyfluorotellurite glass

Abstract

The Eu3+-doped zinc oxyfluorotellurite (TZLFE) glass of molar composition 59TeO2–20ZnO–20LiF–1Eu2O3 has been prepared and studied by broadband, Raman, and fluorescence-line narrowing (FLN) spectral techniques to investigate the local environments of Eu3+ ions in this glass. From the vibronic spectra, different TeO groups coupled to Eu3+ ions have been identified. From the broadband excitation and emission spectra at RT, energy levels of the Eu3+ ion and the atomic parameters have been calculated. The D05 level of Eu3+ ions in the TZLFE glass has been selectively excited within the inhomogeneously broadened F07→D05 excitation spectrum at 15K. The resulting D05→F17 fluorescence spectra and the lifetimes of the D05 level have been obtained as a function of the excitation wavelength. From the FLN spectra, three Stark levels have been identified and crystal-field (CF) analysis has been carried out to calculate second rank CF parameters, by assuming C2v orthorhombic symmetry, as a function of the excitation wavelength. From the CF parameters, CF strength parameter has been calculated. The observed behavior suggests the existence of a unique kind of site for all the environments of Eu3+ ions in the TZLFE glass. The local structure of Eu3+ ions in the TZLFE glass is almost similar to sodium borosilicate glass but with a shorter distribution of environments.