The preparation of zirconia powder can be divided into physical and chemical methods. Physical methods include mechanical grinding, solid phase method, etc. Chemical methods include wet chemical methods (including precipitation method, hydrothermal method, etc.), solvent evaporation method, etc. The following are some preparation techniques of zirconia powders:

1. Hydrothermal method
Hydrothermal method is an advanced and mature technology for the preparation of inorganic materials. This method is suitable for the preparation of metal oxide and composite metal oxide nano-ceramic powder.
In autoclave, zirconium salt (ZrOCl2) and yttrium salt (Y(NO3)3) solution were added with appropriate chemical reagents, and the reaction at high temperature and pressure directly generated nano-level zirconia particles, forming a yttrium-stable zirconia solid solution.
Advantages for powder particle size is very fine, can reach the nanometer level, particle size distribution is narrow. The disadvantage is that the equipment is complex and expensive, and the reaction conditions are harsh.

2. Co-precipitation method
The co-precipitation method is to add ammonia and other solutions in the mixed water solution of water-soluble zirconium salt and stabilizer. After the reaction, hydroxide, carbonate and sulfate, which are insoluble in water, are generated. Then the high-purity ultrafine powder is obtained by heat decomposition.
This method is widely used because of its simple equipment, low production cost and easy to obtain nanometer ultrafine powder with high purity. But the main disadvantage of coprecipitation method is that it does not solve the problem of hard agglomeration of ultrafine powder.

3. Sol-gel method
Sol-gel method is widely used to prepare ultrafine powders. It starts from the solution of metal compounds and hydrolyzes at a lower temperature to obtain uniform sols of metal oxides or hydroxides, and then condenses them into transparent gels. After drying and heat treatment, oxide ultrafine powders with particle sizes ranging from several to several hundred nanometers are obtained.
The process is simple and the reaction temperature is low.

4. Hydrolysis precipitation method
Oxide ultrafine powder can be formed by hydrolysis of alum salt solution, sulfate solution, chloride solution and nitrate solution at high temperature for a long time.
Hydrolysis precipitation method is divided into zirconium brine precipitation and zirconium alcohol brine precipitation two methods.

5. Metal alkyd method
Metal alkoxide method is to use some metal organic alkoxide can be dissolved in organic reagents and hydrolyzed in water to generate hydroxide or oxide precipitation characteristics and prepare ultrafine powder. When metal alkoxide is exposed to water, it is easy to decompose into alcohols and oxides or their hydrates, which can be precipitated by filtration, drying and roasting.
Due to the volatile nature of alcohol, the greatest advantage of this method is the fast reaction speed, which can be directly separated from the mixture of the obtained substance to prepare high-purity nanoparticles. The particles obtained are almost all primary particles with uniform size and shape.
The e disadvantage of this method is that it is expensive and easy to cause pollution problems. (source from Internet: small particle world)