Structural and spectroscopic investigations on Eu~(3+)-doped alkali fluoroborate glasses

摘要

Eu~(3+)-doped alkali fluoroborate glasses B_2O_3-XCO_3-NaF-Eu_2O_3 (where X = Li_2, Na_2, K_2, and Ca, Mg) have been prepared using the conventional melting technique and their structural and optical properties have been evaluated. The XRD pattern of the glasses confirmed the amorphous nature and the FTIR spectra reveal the presence of BO_3 and BO_4 units as their local structures along with the strong OPT groups. From the absorption spectra the bonding parameters have been calculated and confirmed that the Eu-O bonds in the studied glasses are of covalent nature. Judd-Ofelt (JO) analysis has been carried out from the emission spectra. The JO parameters have been used to calculate transition probabilities (A), lifetime (TAU_R) and branching ratios (beta_R) and peak stimulated emission cross-section (sigma_P~E) for the ~5D_0 - > ~7F_J (J = 1, 2, 3 and 4) transitions of the Eu~(3+) ions. The decay from the ~4D_0 level of Eu~(3+) ions in the title glasses has been measured and analysed. The lifetime of the ~4D_0 level is found to be shorter than the reported glasses which may be due to the presence of OH~- groups.