Fully stabilized zirconia ceramics belong to the cubic fluorite structure. Due to the existence of oxygen octahedral voids in the fluorite structure, this relaxed structure is conducive to the diffusion and migration of cations, and has strong solid electrolyte conductivity, especially solid solution After adding the stabilizer, a large number of oxygen vacancies are formed, and a good oxygen ion conductivity is formed.
At present, the fully stabilized zirconia oxygen sensor doped with yttrium oxide has been used as the basic means of oxygen quantitative analysis in many work analysis processes, and the operating temperature is between room temperature and 900°C. The particularity of working conditions requires the material to have certain thermal shock resistance. However, the fully stabilized zirconia ceramic itself has a large thermal expansion coefficient and low thermal conductivity. After being impacted, the strength decreases rapidly. After microcracks or macro cracks appear inside, the product will fail. Generally, oxygen sensors for automobiles are replaced once a year, and some industrial oxygen sensors for measuring molten steel fail even after one use. Therefore, the development of fully stabilized zirconia with high thermal shock resistance is extremely important.
A brief introduction to the preparation process of a fully stabilized zirconia ceramic material with high thermal shock resistance. The main feature of the fully stabilized zirconia product prepared by this process is that the product includes a matrix and whiskers distributed throughout the matrix. The matrix is fully stabilized zirconia doped with yttria. The whiskers mentioned above are alpha alumina whiskers with an average length of 1-50μm. The doped mole percentage of yttria (accounting for the total matrix) is 4- 12mol%, the weight percentage of alumina whiskers is 5-25wt%. In addition, the ceramic material may also contain 0-3wt% of one or more sintering aid components of MgO, SiO2, CaO and Al2O3.
The process mainly includes the following three steps:
1. Ingredients: The matrix, alpha alumina whiskers and adhesive are mechanically mixed in proportion. The mixing equipment can be a stirring ball mill, a V-type mixer, a planetary ball mill, etc.
2. Forming: In the forming machine, the mixed ingredients are made into a green body. The molding method can be compression molding, isostatic pressing molding, hot die casting molding, injection molding, slurry molding, etc.
3. Sintering: Put the green body in a sintering furnace at 1300-1800°C for 1-3 hours. It can be sintered under vacuum, partial pressure, pressureless or pressurized environment. The sintering atmosphere can be air or nitrogen. Generally, air atmosphere pressureless sintering can be used, and the sintering temperature is between 1550-1670°C.
