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 (11B, 27Al, 29Si, 23Na, 17O, and 25Mg) and Raman spectroscopy. The progressive addition of cations 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. [ABSTRACT FROM AUTHOR]
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