Impact of magnesium on the structure of aluminoborosilicate glasses: A solid‐state NMR and Raman spectroscopy study

Seven magnesium- containing aluminoborosilicate glasses, with three to five oxides, have been studied through comprehensive multinuclear solid- state NMR ( 11 B, 27 Al, 29 Si, 23 Na, 17 O, and 25 Mg) and Raman spectroscopy. The progressive addition of cati- ons and the substitution of sodium and calcium by magnesium illuminate the impact of magnesium on the glass structure. The proportion of tri- coordinated boron drastically increased with magnesium addition, demonstrating the poor charge- compensating capabilities of magnesium in tetrahedral boron units. Oxygen- 17 NMR showed the formation of mixing sites containing both Na and Mg near nonbridging oxygen sites. Furthermore, a high magnesium content appears to result in the formation of two subnetworks (boron and silicon rich) with different polymerization degrees as well as to promote the formation of high- coordination aluminum sites (Al[V] and Al[VI]). Finally, magnesium coordination ranging from 4 to 6, with a mean value shifting from 5 to 6 along the series, suggests that magnesium might endorse an intermediate role in these glasses.