Structural implications of water and boron dissolution in albite glass

Abstract A combined nuclear magnetic resonance, infrared and Raman spectroscopic study on the effect of water dissolution on the structure of B-bearing aluminosilicate glasses is presented. The base composition was albite (NaAlSi3O8) to which different amounts of B2O3 (4.8, 9.1, 16.7 wt%) were added. Hydrous glasses containing 4.4 ± 0.1 wt% water were synthesized at pressures of 2000 bar. The results show that B dissolves in both dry and hydrous glasses by forming predominantly trigonal BO3 groups although some tetrahedral BO4 is also present. In anhydrous glasses prepared at high pressures (above 10 kbar) the fraction of BO4 increased. The hydrous glasses contain more BO4 groups compared to the dry counterparts, suggesting that this species is stabilized by water. The Raman and NMR (17O, 27Al, 29Si) spectra show that B interacts with the aluminosilicate network by formation of Si–O–B and probably Al–O–B units. In the hydrous glasses the water speciation changes significantly towards higher hydroxyl concentrations with increasing B-content. The NIR peaks, which are related to OH groups and molecular H2O, develop additional shoulders, suggesting that possibly B–OH complexes are formed.