Structure of heat-treated sol-gel SiO2 glasses containing silver

The crystallization of bulk amorphous SiO2 samples, prepared by the sol-gel method, was obtained by heat treatments in air at temperatures as low as 500 degreesC, This occurs when silver is added to the precursor solutions in an amount such that it forms aggregates embedded in the glass. Another requirement to observe the low-temperature glass crystallization is that the bulk samples must be prepared from precursor solutions with specific compositions. These compositions, have a high H2O/TEOS ratio, which produces an amorphous SiO2 structure with some structural similarities to cristobalite, the phase in which the SiO2 glass crystallizes.