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.