Cerium trivalent

Cerous salts in general are colorless because Ce " has no absorption bands in the visible. Trivalent cerium, however, is one of the few lanthanide ions in which parity-allowed transitions between 4f and Sd configurations can take place and as a result Ce(III) compounds absorb in the ultraviolet region just outside the visible. 

The main usefulness of Eh-pH diagrams consists in the immediacy of qualitative information about the effects of redox and acid-base properties of the system on elemental solubility. Concerning, for instance, cerium, figure 8.20 immediately shows that, within the stability field of water, delimited upward by oxidation boundary curve o and downward by reduction boundary curve r, the element (in the absence of other anionic ligands besides OH groups) is present in solution mainly as trivalent cerium Ce and as soluble tetravalent hydroxide Ce(OH)2. It is also evident that, with increasing pH, cerium precipitates as trivalent hydroxide Ce(OH)3. 

The main processes occurring in this system are the following [219] bromate oxidizes trivalent cerium to tetravalent cerium Ce4+ oxidizes bromomalonic acid, and is reduced to Ce3+. The bromide ion, which inhibits the reaction, is isolated from the oxidation products of bromomalonic acid. During the reaction, the concentration of the Ce4+ ions (and Ce3+) oscillates several times, passing through a maximum and a minimum. The shape of the peaks of concentrations and the frequency depend on the reaction conditions. The autooscillation character of the kinetics of the cerium ions disappears if Ce4+ or Br are continuously introduced with a low rate into the reaction mixture. The autooscillation regime of the reaction takes place only in a certain interval of concentrations of the reactants [malonic... 

After filtering off the solid residue, the cold solution is treated with sodium sulphate. The precipitated double sulphate of the rare earths is washed with 0.3N sodium sulphate, and then boiled with excess (10%) sodium hydroxide to convert the double sulphate into a hydroxide. The rare earths hydroxides are filtered off and dried at 120° C to oxidize trivalent cerium into the tetravalent state. The dried material contains about half of the original thorium coprecipitated with rare earth double sulphates. 

Trivalent cerium bands observed and their assignment is given below. 

The first Ce(IV) complex stabilized by an alkoxo functionalized Ai-heterocyclic carbene anion has recently been reported. The complex is made by oxidation of the corresponding trivalent cerium complex using benzoquinone (Figure 8.36). The cerium cation is coordinated by two bidentate ligands and two monodentate ligands, in which the NHC groups are unbound [123],... 

The berkelium (IV) extraction coefficients have been determined by stripping solvents previously loaded with tetravalent cerium and berkelium in the presence of sodium bismuthate. Sodium bismuthate has been found to be an efficient oxidizing agent for trivalent cerium. Because of its small solubility it does not affect the distribution coefficients of tetravalent cerium. These two properties have been demonstrated by comparing the distribution coefficients of cerium (IV) measured by spectrophotometry with those of cerium oxidized by sodium bismuthate and measured by beta counting of the cerium isotope tracer. The data are summarized in Table I and indicate no real difference in the distribution coefficients of cerium obtained by these two methods when using trilaurylmethylammonium salts-carbon tetrachloride as solvent. 

Yttria-doped( 20 mol% Y2O3) cerium oxide also has a higher 0 ion conductivity than yttria-stabilized zirconia ( factors of 11-18 at 600°C), which would make it an attractive choice for an electrolyte at lower temperatures (< 800 C) However, doped cerium oxides tend to undergo reduction, with formation of trivalent cerium ions and oxygen ion vacancies, V 6 leading to the onset of electronic conductivity according to ... 

IIIC) Zhabotinskii, A. M., Zaikin, A. N., Rovinskii, A. B. Auto-Oscillations in the Oxidation 1982 of Trivalent Cerium by Bromate with a Controlled Supply of Bromide into the Reactor. 

A structure similar to that of LaY zeolites has been suggested for CeY zeolites (3,7). However, structural x-ray studies of CeX zeolites have shown (9) that the presence of trivalent and especially tetravalent- cerium results in a considerable distortion of the 6-membered ring. Such a distortion could explain the lower hydrothermal stability and stronger dealumination of CeY zeolites vs LaY zeolites. Indeed, the loss in crystallinity and surface area observed for steamed CeY zeolites as compared to corresponding LaY zeolites (Table I) is indicative of significant structural collapse. Furthermore, the paramagnetism of trivalent cerium ions and the local framework distortions, caused primarily by tetravalent cerium ions, will result in a deterioration of spectral resolution. 

Table 6.18 summarizes distribution coefficients of hexavalent uranium, thorium, and trivalent cerium (representative of rare earths) for four different types of long-chain amines, in sulfate solution with phosphate ion absent. Primary amines have the highest coefficient for thorium and the lowest for uranium, with the converse true of tertiary amines such as were cited for uranium extraction in Chap. 5. Secondary amines extract both metals, with thorium extraction favored by branching distant from the nitrogen. Either primary or secondary amines provide good separation of thorium from cerium. 

If one were to assign oxidation states to the cerium pnictides, a formulation of trivalent cerium and also P , As , Sb , and Bi would be straight-... 

Cerium(IV) trifluoromethanesulfonate [cerium triflate, Ce(0S02CF3)4 H2O, Ce(OTf)4 H2O] [698999-65-4] M 736.4 (anhydrous), slowly decomposes above 120 to give trivalent cerium species. 

CejRhSij is isostructural with the structure type of ErjRhSij (Chevalier et al., 1984) crystal data as derived from X-ray powder diffraction of arc-melted samples annealed at 800°C, 4 d, were as follows P62c, a = 8.210(5), c = 8.410(5). Cc2RhSi3 is antiferromagnetic below = 6 K paramagnetic susceptibilities (1.5-300 K) correspond to trivalent cerium jaff = 2.40 gg, 6p= — 83 K (Chevalier et al., 1984). 

Trivalence cerium ion Ce has been also widely used in phosphor materials as an activator for white LEDs. Recentiy, many Ce Lactivated phosphors with novel longer-wavelength emission over yellow emission have been reported. In this chapter, we discuss the phosphors including an octahedral site as a dopant site for Ce in the crystal lattice. The luminescence properties of the Ba3Sc409 Ce phosphor were recendy reported by Hasegawa et al. in 2014 [61]. 

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