Cerium oxides crystal structure

Powder XR diffraction spectra confirm that all materials are single phase solid solutions with a cubic fluorite structure. Even when 10 mol% of the cations is substituted with dopant the original structure is retained. We used Kim s formula (28) and the corresponding ion radii (29) to estimate the concentration of dopant in the cerium oxide lattice. The calculated lattice parameters show that less dopant is present in the bulk than expected. As no other phases are present in the spectrum, we expect dopant-enriched crystal surfaces, and possibly some interstitial dopant cations. However, this kind of surface enrichment cannot be determined by XR diffraction owing to the lower ordering at the surface. 

Nd2-xCexCu04, 112,427-45 band structure schematic, 717 cerium oxidation state, 431 comparison with La2CuO>4 systems, 320 composition range, 437 copper oxidation state, 427,442 crystal chemistry, 428-31 crystal growth, 244,436-7,442-4... 

Cerium oxide, or ceria (Ce02), is a component of an autoexhaust catalyst that crystallizes to the fluorite structure [45], In the fluorite structure of Ce02, a CCP framework of Ce4+ ions is formed, where the eight tetrahedral sites present in the FCC structure are occupied by O2 ions (see Figure 2.16, where the links between atoms to make the tetrahedral positions clear are shown) [52],... 

Boussie, T.R., Eisenberg, D.C., Rigsbee, J. et al. (1991) Structures of organo-f-element compounds differing in the oxidation state of the central metal crystal structures of bis([8]annulene) complexes of cerium(lV), ytterbium(III), and uranium(III). Organometallics, 10, 1922. 

Other oxygen ion conductors that have potential use as solid electrolytes in electrochemical devices are stabilized bismuth and cerium oxides and oxide compounds with the perovskite and pyrochlore crystal structures. The ionic conductivity and related properties of these compounds in comparison with those of the standard yttria-stabilized zirconia (YSZ) electrolyte are briefly described in this section. Many of the powder preparation and ceramic fabrication techniques described above for zirconia-based electrolytes can be adapted to these alternative conductors and are not discussed further. 

Cerium (IV) oxide is white with a slight yellow tinge the color is a function of particle size. Even slight contamination with Pr or Tb (0.005%) produces a distinct pink color higher amounts cause a red-brown color. The calcined material is soluble in acids only in the presence of reducing agents, d (x-ray) 7.172. Crystal structure type Cl (CaFg type). 

Cerium oxide, ceria, has a fluorite structure and shows oxide anion conducting behavior differ from other rare earth oxides. However, the O ionic conductivity of pure ceria is low because of a lack of oxide anion vacancies. For ion conduction, especially for anion, it is important to have such an enough vacancy in the crystal lattice for ion conduction. Therefore, the substitution of tetravalent Ce" by a lower valent cation is applied in order to introduce the anion vacancies. For the dopant cation, divalent alkaline earth metal ions and some rare earth ions which stably hold trivalent state are usually selected. Figure 9-28 shows the dopant ionic radius dependencies of the oxide ionic conductivity for the doped ceria at 800°C. In the case of rare earth doped Ce02, the highest O ion conductivity was obtained for... 

In situ IR investigations on ceria abrasives are challenging. Cerium(IV) oxide crystallized in a fluorite structure (space type Fm3m), which will only give three fundamental vibrational modes (2 x Fiu 1 x p2g) all located in the FIR range where only the TO mode of the threefold-degenerated Fiu vibration is IR active (Mochizuki,... 

Among the complex nitrates of tetravalent cerium the well-known compoimd (NH4)2[Ce(N03)g] has been structurally characterized by single crystal methods (Beineke and Delgaudio, 1968) (see fig. 82). This compound was earlier used in industrial separation processes aimed at the production of pure cerium oxide (Smith et al., 1936). It also is used in quantitative analytical determinations for the preparation of standard cerium solutions (Petzold, 1955). 

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