A partially magnesia stabilised zirconia ceramic material is claimed having a cubic zirconia phase content of 25-70 vol.% and a MgO content of 3.0-3.65 wt.% of the ceramic. The material contains an additive metal oxide which forms an insol. zirconate that does not combine with MgO, in an amt. of 0.05-1.00 wt.%. The microstructure consists of grains of cubic ZrO2, each grain contg. pptes. of tetragonal ZrO2 transformable on application of tensile stress or heat treatment into monoclinic ZrO2. The pptes. are lenticular in shape and have an ave. length of about 150 nm in their longest dimension. Each grain contains grain matrix monoclinic ZrO2 as transformed tetragonal ZrO2 in a first specified range of monoclinic ZrO2 content. A ground surface and a polished surface of the material each contains monoclinic ZrO2 in second and third specified ranges of content, the specified ranges of content being different for ceramics to be used in different ranges. Also claimed is a method of mfg. the ZrO2. ZrO2 based materials can be provided for different temp. range uses, with appropriate combinations of the properties, thermal shock resistance, strength and wear resistance, without trying to obtain the optimum of each of these properties for use at all temps.
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