Pure ZrO2 is white, yellow or gray when containing impurities, generally containing HfO2, not easy to separate. The world's proven zirconium resources are about 19 million tons, and zirconia is usually made from zirconium ore. There are three kinds of crystalline forms of pure ZrO2 under normal pressure: monoclinic zirconia (m-ZrO2), tetragonal (zitragonal) zirconia (t-ZrO2) and cubic (cubic) zirconia (c-ZrO2). The three crystal forms exist in different temperature ranges and can be converted into each other:
Temperature density
Monoclinic zirconia (m-ZrO2) <950 ° C 5.65 g / cc
Tetragonal zirconia (t-ZrO2) 1200-2370°C 6.10g/cc
Cubic zirconia (c-ZrO2) > 2370 ° C 6.27 g / cc
The above three crystalline states have different physical and chemical properties. In practical applications, in order to obtain the desired crystal form and performance, different types of stabilizers are usually added to make different types of Zirconia Ceramics, such as partially stabilized zirconia (partially stabilized zirconia, PSZ), when the stabilizer is CaO, MgO, or Y2O3, it is represented by Ca-PSZ, Mg-PSZ, Y-PSZ, and the like, respectively. Tetragonal zirconia consisting of metastable t-ZrO2 is called tetragonal zirconia polycrystal (TZP). When the stabilizers added are Y2O3 or CeO2, they are represented by Y-TZP, Ce-TZP, and the like, respectively.
