Cerium(IV) oxide, ceric oxide, ceria, or sometimes simply cerium oxide or cerium dioxide, is a pale yellow-white powder, CeO₂. It is used in ceramics, to polish glass, and to sensitize photosensitive glass. It is also used in lapidary as "jeweller's rouge"; it is also known as "optician's rouge".^[1] Ceria is used in the walls of self-cleaning ovens as a hydrocarbon catalyst during the high-temperature cleaning process. The flash point of a flammable liquid is the lowest temperature at which it can form an ignitable mixture with air. ... Risk and Safety Statements, also known as R/S statements, R/S numbers, R/S phrases, and R/S sentences, is a system of hazard codes and phrases for labeling dangerous chemicals and compounds. ... R-phrases are defined in Annex III of European Union Directive 67/548/EEC: Nature of special risks attributed to dangerous substances and preparations. ... S-phrases are defined in Annex IV of European Union Directive 67/548/EEC: Safety advice concerning dangerous substances and preparations. ... RTECS, also known as Registry of Toxic Effects of Chemical Substances, is a database of toxicity information compiled from the open scientific literature that is available for charge. ... The refractive index (or index of refraction) of a material is the factor by which the phase velocity of electromagnetic radiation is slowed in that material, relative to its velocity in a vacuum. ... The dielectric constant εr (represented as or K in some cases) is defined as the ratio: where εs is the static permittivity of the material in question, and ε0 is the vacuum permittivity. ... Ultraviolet-Visible Spectroscopy or Ultraviolet-Visible Spectrophotometry (UV/ VIS) involves the spectroscopy of photons (spectrophotometry). ... IR spectrum of a thin film of liquid ethanol. ... It has been suggested that NMR Data Processing be merged into this article or section. ... Mass spectrometry (also known as mass spectroscopy (deprecated)[1] or in common speech mass-spec) is an analytical technique used to measure the mass-to-charge ratio of ions. ... Multivalent redirects here. ... Multivalent redirects here. ... In chemistry, the standard state of a material is its state at 1 bar (100 kilopascals) and 25 degrees Celsius (298. ... Fixed Partial Denture, or Bridge The word ceramic is derived from the Greek word κεραμικός (keramikos). ... A lapidary (the word means concerned with stones) is an artisan who practices the craft of working, forming and finishing stone, mineral, gemstones, and other suitably durable materials (amber, shell, jet, pearl, copal, coral, horn and bone, glass and other synthetics) into functional and/or decorative, even wearable, items (e. ... Rouge means red in French and it can refer to: A fine powder of iron(III) oxide, used for polishing or cosmetics. ... A self-cleaning oven is an oven which uses high temperature (approximately 900 degrees Fahrenheit or 500 degrees Celsius) to burn off leftovers from baking, without the use of any chemical agents. ...

It is slightly hygroscopic and will also absorb a small amount of carbon dioxide from the atmosphere. A hygroscopic substance is a substance that absorbs water readily from its surroundings. ... Carbon dioxide is a chemical compound composed of one carbon and two oxygen atoms. ... Layers of Atmosphere (NOAA) Air redirects here. ...

Note that cerium also forms cerium(III) oxide, Ce₂O₃. General Name, Symbol, Number cerium, Ce, 58 Chemical series lanthanides Group, Period, Block n/a, 6, f Appearance silvery white Atomic mass 140. ...

As a fuel cell electrolyte

In the doped form, ceria has seen interest as a material for solid oxide fuel cells or SOFCs because of its relatively high oxygen ionic conductivity (i.e. oxygen atoms readily move through it) at intermediate temperatures (500-800℃). Undoped and doped ceria also exhibit high electronic conductivity at low partial pressures of oxygen due to the formation of small polarons. However, doped ceria has an extended electrolytic region (area of predominant ionic conductivity), over that of ceria, that allows its use as an electrolyte in SOFCs. Substituting a fraction of the ceria with gadolinium or samarium will introduce oxygen vacancies in the crystal without adding electronic charge carriers. This increases the ionic conductivity and results in a better electrolyte. Solid oxide fuel cells, or SOFC, are intended mainly for stationary applications with an output of 1 kW and larger (power plants). ... An electrolyte is a substance containing free ions which behaves as an electrically conductive medium. ... General Name, Symbol, Number gadolinium, Gd, 64 Chemical series lanthanides Group, Period, Block n/a, 6, f Appearance silvery white Atomic mass 157. ... General Name, Symbol, Number samarium, Sm, 62 Chemical series lanthanides Group, Period, Block n/a, 6, f Appearance silvery white Atomic mass 150. ...

Under reducing conditions, those experienced on the anode side of the fuel cell, a large amount of oxygen vacancies within the ceria electrolyte can be formed. This results in the normally pale yellow ceria to turn black or grey as the result of color center formation. Some of the cerium(IV) oxide is also reduced to cerium(III) oxide under these conditions which consequently increases the electronic conductivity of the material. Finally, ceria undergoes what is described as a chemical expansion under reducing conditions as a result of reduction of the cerium cation from a 4+ to a 3+ state in order to charge compensate for oxygen vacancy formation. Semi-accurate illustration of a redox reaction Redox reactions include all chemical processes in which atoms have their oxidation number (oxidation state) changed. ... Diagram of a zinc anode in a galvanic cell. ... A fuel cell is an electrochemical device similar to a battery, but differing from the latter in that it is designed for continuous replenishment of the reactants consumed; i. ... Hotels, motels, inns, apartments, or business suites could have vacancies, i. ... The colour centre is a region in the human brain responsible for processing colour. ... Semi-accurate illustration of a redox reaction Redox reactions include all chemical processes in which atoms have their oxidation number (oxidation state) changed. ... Semi-accurate illustration of a redox reaction Redox reactions include all chemical processes in which atoms have their oxidation number (oxidation state) changed. ...

As a catalyst

Ceria has been used in catalytic converters in automotive applications. Since ceria can become non-stoichioimetric in oxygen content (i.e. it can give up oxygen without decomposing) depending on its ambient partial pressure of oxygen, it can release or take in oxygen in the exhaust stream of a combustion engine. In association with other catalysts, ceria can effectively reduce NOx emissions as well as convert harmful carbon monoxide to the less harmful carbon dioxide.

Defects

In the fluorite structure, ceria exhibits several defects depending on partial pressure of oxygen. The primary defects of concern are oxygen vacancies and small polarons (electrons localized on cerium cations) because these two are located in the "useful" range of ceria.

References

1. ^ http://home.thezone.net/~dbourgeo/feb/feb-2001-talk.html

• Webelements at University of Sheffield
• Center for Advanced Microstructures and Devices at Louisiana State University