A Raman and MAS NMR study of mixed alkali Na–K and Na–Li aluminoborosilicate glasses

Structural studies of two types of aluminoborosilicate glasses (Na/K and Na/Li) using Raman and NMR spectroscopy are presented. Both types of glasses display a mixed alkali effect (MAE) according to electrical conductivity and Tg measurements. Concerning the glass structure and more particularly the silicate network, our results show that the MAE slightly affects the glass polymerization degree, which displays a maximum for intermediate Na/K and Na/Li range compositions. A non-linear variation of the BO4/BO3 ratio is also observed from 11B MAS NMR. Moreover, our results demonstrate that potassium favors the formation of danburite-type rings in the glassy matrix and the assignment of the 1400 cm−1 Raman band is revisited.