Ceramics might be thought of as the close cousin of glass. Both materials are inorganic. Both have many useful physical properties and are formed via high-temperature processes. And with the right composition and forming, both can be extremely hard and resistant to thermal shock, suitable for use in harsh environments like outer space.  

The primary difference between glass and ceramics, though, centers on the chemical bonds that hold the internal structure of the material together. Unlike glass, in which atoms are arranged in a random order, linkages in ceramic materials happen when positive and negative ions bond to form a regular pattern of crystals — which, in turn, can scatter the light to which they are exposed. This phenomenon usually results in an opaque material, rather than transparent, although there are examples of transparent ceramics.

Halfway between the two materials is glass-ceramics, which start life as a glass and then transform into a nearly completely crystalline, or ceramic, substance. This happens under an intense application of carefully controlled heat and the addition of a nucleating agent — silver or titanium, for example — that forms “seeds” around which crystals can grow.

As with glass, materials scientists can manipulate the formulas of ceramics and glass-ceramics to achieve a wide variety of properties. Some ceramics are virtually impervious to electricity and heat, making them ideal for applications ranging from insulators in household wiring to re-entry heat shields for spacecraft.

Other ceramics have highly conductive properties and have formed a new and growing category called electroceramics. These materials are finding application in energy-saving ultracapacitors, wireless communications, and other breakthrough innovations.

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