On the crystallization of gel-derived albite (NaAlSi3O8): the most stable oxide glass

Some glass-forming oxides, such as unseeded B2O3 and albite (NaAlSi3O8), exhibit outstandingly high resistance to devitrification and have never been crystallized at ambient pressure. For instance, a classical study reported that an albite glass produced by melting was held at 1025 °C (close to the maximum growth rate predicted by a theoretical model) for 5 years without crystallizing. In this study, we tested the crystallization behavior of gel-derived albite glasses synthesized through two distinct and original routes and compared them with a melt-quenched sample because sol–gel glasses normally crystallize much faster than isochemical melt-derived glasses. Not only the melt-derived glass but also one of the gel samples (which contained much more OH− than its melted counterpart) remained amorphous in a differential scanning calorimetry experiment and after 12 h of heat treatment at 1000 and 1030 °C. The other gel-derived material contained residual carbon partially crystallized during the same thermal treatment at 1000 and 1030 °C. Therefore, in the absence of a suitable nucleating agent, crystallization does not occur, even in gel-derived albite glass with a high OH− content.