Toughening method of yttria-stabilized zirconia ceramics

Zirconium oxide is a special material. The toughening method is mainly achieved by using the phase change of zirconia! Pure zirconia is a white solid. When it contains impurities, it will appear gray or light yellow. Adding a color developer can also display various other colors. The molecular weight of pure zirconia is 123.22, the theoretical density is 5.89g/cm3, and the melting point is 2715°C. Usually contains a small amount of hafnium oxide, which is difficult to separate, but has no obvious impact on the properties of zirconium oxide. Zirconia has three crystal forms: monoclinic, tetragonal, and cubic phases.

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Zirconium Oxide only appears in the monoclinic phase, transforms into the tetragonal phase when heated to about 1100°C, and transforms into the cubic phase when heated to higher temperatures. Since a large volume change occurs when the monoclinic phase transforms into a tetragonal phase, and a large volume change occurs in the opposite direction during cooling, it is easy to cause cracking of the product, limiting the application of pure zirconia in high temperature fields. . However, after adding a stabilizer, the tetragonal phase can be stable at room temperature, so there will be no sudden change in volume after heating, which greatly expands the application range of zirconia. The raw material used as stabilizer on the market is mainly yttrium oxide.