Extended electron energy loss fine structure simulation of the local boron environment in sodium aluminoborosilicate glasses containing gadolinium

Electron energy loss boron K-edge spectra of gadolinium-bearing sodium aluminoborosilicate glasses were acquired. Extended electron energy loss fine structure studies were performed in both extended and near edge region. Using Gd-metaborate, GdB3O6, as a model, we fitted the experimental B K-edge spectra of the glasses containing 30 and 47 mass% Gd2O3 in r-space with a non-linear least-square fitting method. Based on the results obtained from the current study, the majority of borate units appear to react with Gd cations and the local environment of Gd cations resembles that of the Gd-metaborate structure. Therefore, a distorted Gd-metaborate-like local atomic structure is proposed, in which each Gd cation is stabilized by one tetragonal BO4 unit and two trigonal BO3 units. The similarity of the chemical environment between the two high Gd-bearing glasses implies that the local Gd-metal borate environment, 1BO4:Gd:2BO3, is stable. When the Gd to B ratio in the glasses exceeded 1 to 3 ratio, according to the model, excess Gd cations should form bonds with silicate units. The modeling results are further supported by the energy loss near edge spectra data and previously results obtained from Raman and laser fluorescence deduced phonon side band studies.