Transmission electron microscopy of partially crystallised glasses

The early stages of crystallisation in a Li₂O-SiO₂-P₂O₅ glass were studied by transmission electron microscopy using thin sections prepared from the bulk material by chemical thinning. Small crystalline regions of lithium disilicate were formed, often as several small single crystals joined together around a central core. Possible explanations of the core are discussed in terms of a region of different chemical composition or a central region of disorder. The observations are also compared with the growth of crystal spherulites in polymers.