Sol-Gel Synthesis of Magnesium Oxide-Silicon Dioxide Glass Compositions

MgO-SiO₂ glasses containing up to 15 mol% MgO, which could not have been prepared by the conventional glass-melting method because of the presence of stable liquid-liquid immiscibility, have been synthesized by the sol-gel technique. The gelling time decreased with increase in magnesium content, water: TEOS ratio, and reaction temperature. The gels were subjected to various thermal treatments and characterized using DTA, TGA, IR spectroscopy, XRD, and surfacearea- and port-size-distribution measurements. No organic groups could be detected in the glasses after heat treatments to ∼800°C, but trace amounts of hydroxyl groups were still present. The overall activation energy for gel formation in the 10MgO·90SiO₂ (mol%) system for the water: TEOS mole ratio of 7.5 was calculated to be 58.7 kJ/mol.