H-1 MAS NMR and IR studies on powdered alkali-lime-silica glasses

Powdered samples of glasses with the composition 16 R2O . 10 CaO . 74 SiO2 (R = Na, K, Cs) and a concentration of water in glass of about 0.03 mol.l ( 1) were studied by solid state H-1 MAS NMR (magic angle spinning nuclear ma gnetic resonance). Three superimposed NMR signals at about 6.3, 12.5 and 15 .6 ppm were recorded, which were assigned to three different proton sites i nvolved in weak, strong and very strong hydrogen bonds, respectively. The r elative intensity of the NMR signals depends on the type of alkali in the g lass. The amount of OH groups with strong and very strong hydrogen bonding increases in relation to the weakly bonded hydroxyl groups upon substitutio n of Na2O, K2O or Cs2O, respectively. The result is in good agreement with the earlier IR findings for these glasses. Thus, Scholze's interpretation [ 1 to 3] of the region of the OH stretching vibrations in the IR spectra cou ld be verified Firstly by NMR spectroscopy as an independent analytical met hod.