Glass has been an important material since the early stages of civilization. Glass–ceramics are polycrystalline materials obtained by controlled crystallization of certain glasses that contain one or more crystalline phases dispersed in a residual glass matrix. The distinct chemical nature of these phases and their nanostructures or microstructures have led to various unusual combinations of properties and applications in the domestic, space, defense, health, electronics, architecture, chemical, energy, and waste management fields.^1–3

In 1739, French chemist René-Antoine Ferchault de Réaumur was the first person known to produce partially crystallized glass.⁴ Réaumur heat-treated soda–lime–silica glass bottles in a bed of gypsum and sand for several days, and the process turned the glass into a porcelain-like opaque material. Although Réaumur had succeeded in converting glass into a polycrystalline material, unfortunately the new product sagged, deformed, and had low strength because of uncontrolled surface crystallization.^4,5