Abstract
The 1950s saw the emergence of the group of materials originally referred to as ‘special ceramics'. These then became ‘engineering ceramics’, and more recently have been further subdivided into bioceramics, functional ceramics, and structural ceramics. These materials demonstrate excellent properties for the application areas indicated, and share the common feature of not using clay as a starting material. In the early 1960s, it could not have been foreseen that electrical ceramics (including superconductors) would develop much more rapidly than the rest; of course this move was stimulated by concurrent developments in computing and electronic devices. In contrast, the more diverse, scientifically challenging structural ceramics have struggled to find niches in a very competitive marketplace, showing only modest growth over the last 30 years. Silicon carbide has been perhaps the least dramatic in its progress, whereas zirconia, stimulated by the toughening revolution, generated an explosion of interest in the early 1980s, though this has since moderated. In contrast, silicon nitride, with the associated family of sialon ceramics, has maintained an overall upward curve for some 40 years, punctuated by occasional spurts due either to new market opportunities or to materials developments, a good current example of the latter being the recent appearance of a group of ultrahard high pressure derivatives.
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