Effect of mutual modification by BaO and BaF2 on the structure and properties of BaO–BaF2–B2O3 glasses

Oxy-fluoroborate glasses of the composition x BaF 2 ·(45- x )BaO·55B 2 O 3 (0 ≤ x ≤ 45 mol%) have been prepared by the normal melt-quenching technique. X-ray diffraction (XRD) and transmission electron microscopy (TEM) confirm that the glassy matrix contains amorphous and/or crystalline phases depending on BaF 2 concentration. Scanning electron microscopy (SEM) shows agglomerates consisting of clusters in micro-scale separated from the amorphous phase. Fourier-transform infrared (FTIR) spectra reveal that BaF 2 partially modifies the borate matrix as in the binary BaF 2 –B 2 O 3 glasses. Values of fraction N 4 of four coordinated boron atoms calculated from FTIR spectra agree with nuclear magneitic resonance (NMR) data. N 4 increases at the expense of non-bridging planar trigonal (BO 3 ) units at low concentrations of BaF 2 while at higher concentrations, N 4 increases at the expense of tetrahedral BO 4 units. Density seems to be constant while molar volume increases from 27.51 to 30.31 cm −1 with increasing BaF 2 content. It is found that the volume of structural units by BaF 2 is greater than those related to BaO. T g have a linear decrease from 580 to 485 °C with increasing BaF 2 concentration. A structural view is presented for the role of BaF 2 , obtained based on N 4 data obtained from NMR and FTIR analysis.