Zirconia, Zirconium Dioxide – ‘The Ceramic Steel’
The applications for this unique material are rapidly expanding. Unlike traditional ceramics that tend to be hard and fragile, stabilised zirconia has high strength, wear resistance, flexibility and a lifetime far beyond those of average ceramics.
Pure zirconia exists in 3 crystal phases at different temperatures – Cubic, Tetragonal and Monoclinic. The transformation between phases occurs during temperature change and can lead to structural failure in the material. A number of different oxides can be dissolved into the zirconia crystal structure to prevent or control these structural changes. Y2O3, MgO and CeO2 are the most common. The level of stabilisation and phase transformation is a complex subject and in simple terms this can be controlled by the grain size, thermal history and level of stabilisers added.
Partially Stabilised Zirconia (PSZ) can either be Tetragonal Zirconia Polycrystal (TZP) or Tetragonal Toughened Zirconia (TTZ). TZP is generally stabilised with Yttria and sometimes Ceria and TTZ is stabilised with Magnesia. Typical stabiliser levels are 3-6wt%.
Cubic zirconia (CZ) is a Full Stabilised Zirconia (FSZ) with higher levels of stabilisers which means it does not go through a destructive phase transition during heating or cooling. The cubic phase of high temperatures is maintained at room temperature. CZ is used in refractories, abrasives and artificial gems stones as a substitute for diamond.