Fluorescence line narrowing spectroscopy of Eu3+ doped sodium germanate glasses

Sodium germanate glasses of compositions (x − 0.5)Na2O–(100 − x)GeO2–0.5Eu2O3 with x = 10, 16, and 22 were studied using laser-induced fluorescence line narrowing (FLN) techniques. From the site selective luminescence spectra of Eu3+ at 20 K, the energies of the Stark components of the 7F1 and 7F2 states were obtained, and a crystal field (CF) analysis was carried out assuming a C2v site symmetry. The dependence of the CF parameters Bkq on the excitation wavenumber was similar to that observed in other oxide glasses. The behavior of the CF ratios B22/B20 and B44/B40 appears to be consistent with that calculated using the geometric model proposed by Brecher and Riseberg. The behavior of the CF strength parameter S suggests that the amount of network modifier in the glass host does not influence the CF at the Eu3+ sites. No evidence was found in the FLN spectra of the influence of 6-coordinated germanium.