Zirconia (ZrO2)

Zirconia material: melting point 2715°C, yellow or grey in its purest form, white powder in its purest form. It has three crystalline forms: monoclinic, tetragonal and cubic. The transformation is reversible and the monoclinic to tetragonal transition is accompanied by volume contraction and density increase when heating up; the tetragonal to monoclinic transition and volume expansion when cooling down. Therefore, it is difficult to produce ceramics from simple zirconia. A stabilizer is added, commonly Y2O3 (yttrium oxide), which is stabilized to a tetragonal crystal.

Zirconia toughening: external forces induce a change to a more stable monoclinic crystalline form, which consumes some of the energy; at the same time, the increase in particle volume inhibits the development of cracks; the resulting microcracks are small and evenly distributed, which can play a role in dispersing stress, thus increasing the toughness of the material.

The disadvantage of zirconia ceramics is that it has a high specific gravity, which makes it less suitable for aerospace applications, followed by a high dielectric parameter, which makes it unsuitable for microwave and high frequency applications; however, it has high strength, high fracture toughness and flexural strength, high wear resistance, thermal insulation, high resistivity, high refractive index, corrosion resistance, good chemical stability, etc.; it can be used in a wide range of industries and can be customized according to customer requirements.