A structural interpretation of B10 and B11 NMR spectra in sodium borate glasses

It is shown that the B10 spectra for sodium borate glasses are sensitive to the different structural groups in the glasses. Five boron sites are inferred from the data: two 4-coordinated sites and three 3-coordinated sites. The two 4-coordinated boron sites are identified as BO4 units connected to all BO3 units, and BO4 units connected to one BO4 unit and three BO3 units. The three 3-coordinated boron sites are identified as BO3 units connected to: (1) all BO3 units; (2) a mixture of BO3 and BO4 units; and (3) all BO4 units. These five sites can be interpreted in terms of Krogh-Moe's structural model of alkali borate glasses, wherein the fraction of each structural group can be determined for eight sodium borate glasses spanning the compositional range from 0 to 35 mol% Na2O. The resulting fractions are consistent with Krogh-Moe's structural model. (Auth.)