Glass-Ceramics: Properties, Processing and Applications

What are glass-ceramics and how are they produced?

Glass-ceramics combine the properties of glasses with the benefits of conventional sintered ceramics.

Most commonly they are manufactured in a process in which a pre-manufactured glass is subjected to a specific heat treatment. This treatment results in a controlled nucleation and crystallisation of the glass. The glass partially crystallises, and the glass-ceramic develops a structure comprising an amorphous (glassy) phase and at least one embedded crystalline phase [1].

Properties of glass-ceramics

Glass-ceramics can range from highly crystalline to containing a more substantial glassy phase. As they contain crystalline phases and, therefore, also grain boundaries, glass-ceramics can range from transparent to opaque [1,2].

Depending on the microstructure and the chemical composition of glass-ceramics, their properties can be tuned to meet demanding requirements. In general, glass-ceramics exhibit almost zero thermal expansion and high toughness. In addition, they are resistant to thermal shock and have a high impact resistance [2].

Common examples of glass-ceramics

Glass-ceramics can be subdivided into two categories: oxide and non-oxide. Oxide glass-ceramics include silicate (SiO2), borate (B2O3), phosphate (P2O5) and germinate (GeO2) type materials. Non-oxide glass-ceramics include chalcogenide, halide and metallic type. [2]

Applications of glass-ceramics

With their thermal and mechanical characteristics, glass-ceramics have a range of applications, including:

• Cooktops (which you'll find in most modern kitchens)
• Household appliances including toasters and clothes irons
• Grills and BBQs
• Smartphone screens
• Infrared applications, such as in infrared heating elements
• In high-temperature furnaces as an insulation material, particularly due to their high thermal robustness
• Biomedical engineering
• Advanced optics, for example for thermal shock resistant colour filters.

Further Reading

If you would like to know more about glass ceramics, read this article: "Glass-ceramic for extreme conditions".

[1] W. Höland, G. H. Beall, Glass Ceramic Technology. John Wiley & Sons, 2012.

[2] B. Karmakar, Functional Glasses and Glass-Ceramics: Processing, Properties and Applications. Butterworth-Heinemann, 2017.