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Cerium(IV) oxide
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Cerium(IV) oxide
Cerium(IV) oxide, also known as ceric oxide, ceric dioxide, ceria, cerium oxide or cerium dioxide, is an oxide of the rare-earth metal cerium. It is a pale yellow-white powder with the chemical formula CeO2. It is an important commercial product and an intermediate in the purification of the element from the ores. The distinctive property of this material is its reversible conversion to a non-stoichiometric oxide.
Cerium occurs naturally as oxides, always as a mixture with other rare-earth elements. Its principal ores are bastnaesite and monazite. After extraction of the metal ions into aqueous base, Ce is separated from that mixture by addition of an oxidant followed by adjustment of the pH. This step exploits the low solubility of CeO2 and the fact that other rare-earth elements resist oxidation.
Cerium(IV) oxide is formed by the calcination of cerium oxalate or cerium hydroxide.
Cerium also forms cerium(III) oxide, Ce
2O
3, which is unstable and will oxidize to cerium(IV) oxide.
CeO2 is one of the most widely studied oxides of cerium and the most oxidized form of cerium. The 4f states strongly hybridize with the O 2p states, making the 4f electrons delocalized. These states form a wide dispersive band, extending over a region of some eV, which can be correctly detected using theoretical methods accurately.
Cerium oxide adopts the fluorite structure, space group Fm3m, #225 containing 8-coordinate Ce4+ and 4-coordinate O2−. At high temperatures it releases oxygen to give a non-stoichiometric, anion deficient form that retains the fluorite lattice. This material has the formula CeO(2−x), where 0 < x < 0.28. The value of x depends on both the temperature, surface termination and the oxygen partial pressure. The equation
has been shown to predict the equilibrium non-stoichiometry x over a wide range of oxygen partial pressures (103–10−4 Pa) and temperatures (1000–1900 °C).
The non-stoichiometric form has a blue to black color, and exhibits both ionic and electronic conduction with ionic being the most significant at temperatures > 500 °C.
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Cerium(IV) oxide
Cerium(IV) oxide, also known as ceric oxide, ceric dioxide, ceria, cerium oxide or cerium dioxide, is an oxide of the rare-earth metal cerium. It is a pale yellow-white powder with the chemical formula CeO2. It is an important commercial product and an intermediate in the purification of the element from the ores. The distinctive property of this material is its reversible conversion to a non-stoichiometric oxide.
Cerium occurs naturally as oxides, always as a mixture with other rare-earth elements. Its principal ores are bastnaesite and monazite. After extraction of the metal ions into aqueous base, Ce is separated from that mixture by addition of an oxidant followed by adjustment of the pH. This step exploits the low solubility of CeO2 and the fact that other rare-earth elements resist oxidation.
Cerium(IV) oxide is formed by the calcination of cerium oxalate or cerium hydroxide.
Cerium also forms cerium(III) oxide, Ce
2O
3, which is unstable and will oxidize to cerium(IV) oxide.
CeO2 is one of the most widely studied oxides of cerium and the most oxidized form of cerium. The 4f states strongly hybridize with the O 2p states, making the 4f electrons delocalized. These states form a wide dispersive band, extending over a region of some eV, which can be correctly detected using theoretical methods accurately.
Cerium oxide adopts the fluorite structure, space group Fm3m, #225 containing 8-coordinate Ce4+ and 4-coordinate O2−. At high temperatures it releases oxygen to give a non-stoichiometric, anion deficient form that retains the fluorite lattice. This material has the formula CeO(2−x), where 0 < x < 0.28. The value of x depends on both the temperature, surface termination and the oxygen partial pressure. The equation
has been shown to predict the equilibrium non-stoichiometry x over a wide range of oxygen partial pressures (103–10−4 Pa) and temperatures (1000–1900 °C).
The non-stoichiometric form has a blue to black color, and exhibits both ionic and electronic conduction with ionic being the most significant at temperatures > 500 °C.
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