The accidental discovery of glass–ceramics by S. Donald Stookey in 1953 revolutionized the glass industry by enabling new properties, such as exceptionally high fracture toughness and low thermal expansion coefficient compared with traditional glasses. Although glassy materials are noncrystalline by definition, glass–ceramics are based on controlled nucleation and growth of crystallites within a glassy matrix. Concentration, size, and chemistry of the crystallites can be controlled through careful design of the base glass chemistry and the heat-treatment cycle used for nucleation and crystal growth. These composition and process parameters give new dimensions for optimizing the properties of industrial glass–ceramics.

Table 1 provides an excellent summary of commercialized glass–ceramic products. The success of these products is based on achieving unique combinations of attributes, including appropriate optical, thermal, mechanical, and biological properties, often which cannot be achieved by an “ordinary” noncrystalline glass. For many of these products, such as MACOR and dental glass–ceramics, forming and machining behavior of the glass–ceramic materials are also of critical concern.