Cerium(IV) oxide
Cubic
Ceria
Light yellow solid
Fixed
7.3 g · cm -3
About 2000 ° C.
Insoluble in water
- 338 mg · kg -1 ( LD50, mouse, ip)
- > 5000 mg · kg -1 ( LD50, rat, oral)
Template: Infobox chemical / molecular formula search available
Cerium ( IV) oxide or cerium oxide is an oxide of the rare earth metal cerium. Besides this also cerium (III ) oxide exists ( Ce.sub.2O.sub.3 ) and the dark blue mixed oxide of cerium (III, IV ) oxide ( Ce3O4 ). In 1808 the English chemist Sir Humphry Davy showed that the rare earth Cerit is not an element but a compound of metallic element, silicon, and oxygen. Between 1839 and 1843, Carl Gustav Mosander the separation and proof that it is a mixture of different metal oxides with silicon dioxide or an island silicate is ( (Ce, La, Ca ) 9 ( Fe 3 , Mg) [( OH) 3 | SiO3 (OH ) | ( SiO4) 6] ).
- 2.1 catalyst
- 2.2 Mantles
- 2.3 abrasives
- 2.4 Further
Properties
Like all rare earth oxides emitted cerium ( IV) oxide upon heating, a strong light. It crystallizes in the fluorite structure. In its purest form the oxide is cream to light yellow. Are therein impurities ( eg, neodymium, praseodymium ) as the oxide may also accept brown hues. The brown color is generally ceria, which is used for grinding and polishing purposes. Here is the purity of no importance.
Reactions
Cerium ( IV) oxide is formed by heating cerium ( III) nitrate, Ce (NO3) 3, or cerium (III) oxalate, Ce2 ( C2O4 ) 3
While heating occurs in the reaction of ceria with conc. Sulfuric acid cerium (IV ) sulfate:
Use
Catalyst
Cerium ( IV) oxide is used in catalysts for motor vehicles and is oxidized according to a shortage of oxygen and carbon monoxide excess hydrocarbons:
In excess oxygen in the exhaust gas, the catalyst can be reactivated again:
Nanocrystalline cerium ( IV) oxide tubes having a diameter of about 0.75 microns can be used for catalytic reactions, for example for direct carboxylation of methanol to dimethyl carbonate with carbon dioxide.
Mantles
An optimal luminous efficiency can be obtained from a mixture of about 99% of thorium ( IV) oxide, and 1% cerium ( IV) oxide. This is exploited in the production of mantles for gas lamps ( incandescent gaslight or Auer light) by being soaked in the corresponding nitrate solutions. When burning arise the oxides, which provide the high light output.
Abrasive
Cerium ( IV) oxide -based polishing agent is used as the opaline in the optical industry for polishing glass. It is normally supplied as a dry white powder and has a density of about 1.6 g / cc. The average grain size is about 1 micron. The polishing slurry, which is prepared with deionized water containing about 60 g per liter of water opaline.
Cerium ( IV) oxide -based polishing slurry is used in the semiconductor technique analogous thereto. They are used primarily in the chemical mechanical polishing ( CMP) of silicon dioxide used. However, the average grain size in this case is much lower, it is only at about 50 to 150 nm, since the cerium (IV ) oxide particles settle relatively rapidly, organic additives, such as polyelectrolytes, to the stabilization of the suspension are used. Further, there are commercial products which use other organic materials, such as certain amino acids, in order to achieve a higher material selectivity between the removal rates of silicon dioxide and nitride. The background is that silicon nitride are used in the SiO2 - CMP as a stop layer and are to be worn when polishing not possible.
More
For future production of hydrogen by means of solar energy, the cerium (IV ) oxide cerium ( III) oxide method is developed.
CeO2 also found in coatings as a UV absorber used. This serves to improve the light resistance of exposed surfaces; Coatings are otherwise degraded by UV radiation.