Toughening Method Of Zirconia Ceramics
Zirconia is a special material, toughening method, mainly using the phase transformation of zirconia to achieve.
Pure zirconia is a white solid, containing impurities will appear gray or light yellow, add chromogenic agent can also display a variety of other colors. The molecular weight of pure zirconia is 123.22, and the theoretical density is 5.89g/cm3, melting point is 2,715 ℃. Usually contains a small amount of hafnium oxide, difficult to separate, but the performance of zirconia has no obvious effect. Zirconia has three kinds of crystal morphology: single oblique, square, cubic crystalline phase. At room temperature, zirconium oxide only in a single oblique phase, heating to 1100 ℃ change to the four-phase, heating to higher temperature will be converted to cubic phase. Due to the transformation of the single oblique square phase will produce larger volume changes, cooling time will be in the opposite direction of a larger volume changes, easy to cause the product cracking, limiting the pure zirconia in the High-temperature field of application. However, after the addition of stabilizer, the quartet can be stable at room temperature, so after heating will not occur volume mutation, greatly expanding the scope of application of zirconia. The main ingredient used in the market for stabilizing agents is yttrium oxide.