Crystallisation in oxide glasses - a tutorial review

Glasses and glass-ceramics have had a tremendous impact upon society and continue to have profound industrial, commercial and domestic importance. A remarkable number of materials, with exceptional optical and mechanical properties, have been developed and enhanced using the glass-ceramic method over many years. In order to develop glass-ceramics, glass is initially prepared via high temperature synthesis and subsequently heat treated, following a carefully designed and controlled process. A glassceramic system comprises crystalline and non-crystalline phases; in multicomponent systems these phases are significantly different from the initial glass composition. The properties of glass-ceramics are defined by microstructure, crystal morphology as well as the final chemical composition and physical properties of the residual glass. Knowing the mechanism of glass crystallisation, it is possible to predict and design a glass-ceramic system with near-ideal properties that exactly fulfil the requirements for a particular application. This tutorial review is a basic introduction to the crystallisation in glasses and mainly focuses on silicate and closely related oxide glasses. The review describes and discusses key learning points in five different sections, which facilitate the understanding of glass crystallisation and development of glass-ceramics.