Abstract: Magnesia partially stabilized zirconia materials, having a cubic phase zirconia content in the range 70 to 25 percent (by volume) and a metal oxide additive which forms an insoluble zirconate, and a microstructure in the form of grains of stabilized cubic phase zirconia containing precipitates of tetragonal phase zirconia, are produced for use at low (less than 400.degree. C.) intermediate (between 400.degree. C. and 700.degree. C.), high (700.degree. C. to 1000.degree. C.) or very high (greater than 1000.degree. C.) temperatures. The higher the temperature of use of the ceramic material, the more the tetragonal precipitates need to be transformed into monoclinic phase zirconia. The extent to which the tetragonal precipitates are transformed is controlled by the way in which a fired, pressed mixture of the ceramic components is cooled from about 1400.degree. C. to about 1000.degree. C. An "ageing" of the ceramic material may be effected by an isothermal hold, preferably at 1350.degree. C. and then at 1100.

Abstract: A magnesia partially stabilized zirconia ceramic material possessing from about 2.8 to about 4.0 wt percent magnesia, and made from a zirconia powder containing no more than about 0.03 percent silica is described. The ceramic material has a microstructure, produced as a consequence of the method by which the material is made, which provides both high strength and good thermal shock resistance properties. This microstructure comprises grains of cubic stabilized zirconia within which are formed, during cooling from the firing temperature, precipitates of tetragonal zirconia. These precipitates are elliptical in shape, with a long axis of about 1500 Angstrom units. Additionally, some of the tetragonal zironcia precipitates are made to transform into a non-twinned microcrystalline monoclinic form of zirconia by reducing the temperature of the material to below 800.degree. C., then subsequently holding the material at a temperature in the range from 1000.degree. C. to about 1400.degree. C.