Cerium(III) oxide

Cerium(III) oxide, also known as cerium sesquioxide, is a chemical compound with the formula Ce₂O₃. It is one of the principal oxides of cerium, a rare earth element. Cerium(III) oxide is a pale yellow-white powder that is insoluble in water but soluble in acids. It is an important material in various industrial applications, particularly in the field of catalysis and as a precursor to other cerium compounds.

Structure and Properties

Cerium(III) oxide adopts a hexagonal crystal structure, similar to that of lanthanum(III) oxide. The compound is characterized by its high melting point and stability under a range of conditions. It is a basic oxide and can react with acids to form cerium salts.

Synthesis

Cerium(III) oxide can be synthesized by the thermal decomposition of cerium(IV) oxide (CeO₂) in a reducing atmosphere. The reduction process typically involves heating CeO₂ in the presence of hydrogen gas or carbon monoxide, which reduces the cerium from the +4 to the +3 oxidation state:

CeO₂ + H₂ → Ce₂O₃ + H₂O

Alternatively, it can be prepared by the direct reduction of cerium(IV) compounds in an appropriate reducing environment.

Applications

Cerium(III) oxide is used in a variety of applications:

• Catalysis: It is used as a catalyst in various chemical reactions, including the oxidation of carbon monoxide and the reduction of nitrogen oxides in automotive catalytic converters.
• Glass Polishing: Cerium(III) oxide is used as a polishing agent for glass and other materials due to its abrasive properties.
• Ceramics: It is used in the production of ceramics and as a dopant in the manufacture of solid oxide fuel cells.
• Optical Coatings: Due to its optical properties, it is used in coatings for lenses and other optical components.

Safety and Handling

Cerium(III) oxide is generally considered to be of low toxicity, but as with all chemical compounds, it should be handled with care. Appropriate safety measures, such as the use of gloves and eye protection, should be employed when handling the material.

Also see

• Cerium(IV) oxide
• Rare earth elements
• Catalysis
• Solid oxide fuel cell