Solid state MAS-NMR and FTIR study of barium containing alumino-silicate glasses

The glass based on a 1.5SiO(2)-Al2O3-0.5P(2)O(5)-CaO-0.67CaF(2) composition was produced and substituted gradually by barium. The structure of the glasses was studied by multinuclear Magic Angle Spinning Nuclear Magnetic Resonance (MAS-NMR) and Fourier Transform Infrared Spectroscopy (FTIR). It was indicated by Si-29 and P-31 MAS-NMR spectra that silicon was present as Q(4) (4Al) and Q(3) (3Al) species and phosphorus was in a Q(1) pyrophosphate environment. Al-29 MAS-NMR spectra showed that four fold coordinated aluminum Al (IV) was the dominant species with a second peak assigned to octahedral aluminum Al (VI). The F-19 spectra suggested that the barium addition caused the formation of Al-F-Ba(n) and F-Ba(n) species. Furthermore, a distribution of silicate network including Si-O-Si stretching (Q(4) and Q(3)) and Si-O-[NBO] (Q(3)) per SiO4 was reflected by the FTIR study.