NOVEL OPPORTUNITIES OF STRUCTURAL INVESTIGATIONS OF GLASSES BY 2D NMR, MULTIPLE-QUANTUM NMR AND AL-27 MAS NMR LINESHAPE ANALYSIS

The recent progress in NMR of glasses is demonstrated using both tradi tional and improved two-dimensional (2D) NMR techniques. A novel appro ach for measuring connectivities Q(II) units in amorphous and polycrys talline solids is explained. Several examples of phosphate samples are presented to show e.g. how chain end groups can be distinguished from pyrophosphate units. Additionally, novel results of Al-27 NMR investi gations in mullites and Na2O-SiO2-Al2O3 glasses were obtained using a careful lineshape analysis. In mullites three different AlO4 units can be found including an estimation of the relative Al occupancy of the various groups. In ternary Na2O-Al2O3-SiO2 glasses we could prove the presence of two AlO4 sites with Al being surrounded by four Q(3) units or possibly one terminal oxygen instead of a Q(3) unit (60 ppm) and b y four Q(4) groups (53 ppm). Finally, two different Na sites have been detected for the first rime using Na-23 MQ NMR in a glass 22.7 Na2O 0 .7 B2O 69.8 SiO2.