What Is Cerium Oxide?
Cerium oxide is a white or light yellow powder inorganic compound.
It is composed of cerium and oxygen, and has the chemical formula CeO2, molecular weight 172.11, and CAS number 1306-38-3. It is one of the rare earth oxides and is also called ceria. It has a melting point/freezing point of 2,600°C, a boiling point or first distillation point and boiling range of 3,285°C, and a density/relative density of 7.132. Regarding solubility, it is insoluble in hydrochloric acid andnitric acid and virtually insoluble in water.
Uses of Cerium Oxide
Cerium oxide has the same structure as fluorite, with 8-coordinated Ce4+ and 4-coordinated O2-, and the space group is Fm3m (#225).
Lattice defects are produced by oxygen partial pressure and mechanical loading, and polaron formation by oxygen defects and electrons localized on cerium ions is particularly noteworthy. Due to its ionic conductivity, which increases with the number of oxygen defects and the diffusion rate of oxide ions, cerium oxide is a promising candidate for solid-state electrodes in solid oxide fuel cells (SOFC).
Applications of Cerium Oxide
1. Abrasives
Cerium oxide is used as a raw material for abrasives for glass, optical lenses, and cathode ray tubes. Abrasives made from cerium oxide not only shave the surface, but also react chemically with silicon dioxide, a major constituent of glass, to make the surface smoother. Traditionally, oxides such as iron oxide and zirconia were used, but these have been replaced by cerium oxide in rapid succession.
2. UV Scattering Agent
Cerium oxide is used as an ultraviolet scattering agent to prevent ultraviolet rays from glass and cathode ray tube coloration, and is also used as an additive in cosmetics to cut ultraviolet rays. It is attracting attention as a substitute for titanium dioxide and zinc oxide.
3. Catalyst
Cerium oxide is used as a catalyst for oxidation reactions due to its property of reversibly changing composition. Cerium oxide-doped thorium oxide is used in the luminous part of white gasoline lanterns, and heat is generated by the air oxidation of fuel gas over a cerium oxide catalyst. It is also used in sensors for three-way catalysts that break down exhaust gases in automobiles, helping to regulate the air-fuel ratio and reduce NOx and carbon monoxide.
4. Optical Materials
Cerium oxide is also used as a highly refractive material with a transmission wavelength range from visible light to the infrared region. It forms crystalline films, has excellent chemical and thermal stability, and is considered to be lattice-matched with silicon. It is also characterized by evaporation at relatively low temperatures among high refractive index materials that have visible light in the transmission wavelength range.
5. Others
Cerium oxide is also used as a raw material for battery anode materials and fine ceramics. It is also used as a decolorizer for glass and can change greenish divalent iron impurities into nearly colorless trivalent iron oxide. Due to its excellent ionic and conductive properties, it is also expected to be used as a mixed ion-electron conductor.
Other Information on Cerium Oxide
1. Cerium Oxide Manufacturing Process
Cerium oxide can be obtained from natural cerium produced as a mixture with other rare earth elements from bastnaesite and monazite. After extraction in a basic aqueous solution, an oxidizing agent is added and the pH is adjusted to separate the cerium. This method takes advantage of the low solubility of cerium oxide and the fact that other rare earth elements are not oxidized.
2. Legal Information
Cerium oxide is not regulated by any major domestic laws such as the Fire Service Law, Poisonous and Deleterious Substances Control Law, Industrial Safety and Health Law, and PRTR Law.
3.Handling and Storage Precautions
Precautions for handling and storage are as follows
- Seal the container tightly and store in a dry, cool, and dark place.
- Use only outdoors or in well-ventilated areas.
- Take care not to scatter dust.
- Wear protective gloves and glasses when using.
- Wash hands thoroughly after handling.
- In case of skin contact, wash with soap and water.
- In case of eye contact, rinse cautiously with water for several minutes.