Image icon  Glass ceramic, heat treated at 900°C for 3 hours

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Description: Glass ceramics are materials that are cooled from the melt in the form of a glass, and then heat treated to induce controlled crystallisation of the glass. Heterogeneous nucleation is carried out at a temperature to maximise the nucleation rate (common nucleating agents include TiO2 and ZrO2), and the temperature is then raised sufficiently to cause the nuclei formed to grow rapidly.

Glass ceramics are strong, reasonably tough, transparent to IR radiation, have a low coefficient of thermal expansion, a high resistance to thermal shock and a low thermal conductivity, which makes them very useful in domestic applications such as cookware and cooker hobs.

The most common glass ceramic system is LAS (Li2O-Al2O3-SiO2), but others include MgO-Al2O3-SiO2, Na2O-BaO-Al2O3-SiO2, and Li2O-MgO-Al2O3-SiO2.
Keywords: ceramic • glass
Categories: Science approaches > Microstructure
Science approaches > Phase transformations
Materials > Ceramics & glasses > Glasses > Glass ceramic
Testing, analysis & experimentation > Metallography
Scale > Micro
Created by: DoITPoMS, University of Cambridge
Dr K M Knowles, Department of Materials Science and Metallurgy, University of Cambridge
Published by: DoITPoMS, University of Cambridge
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Date created: 09 August 2002
Date added: 21 August 2009
Resource ID: 1202