Rare earth metal compounds solutions

Yttrium is found together with other rare earth oxides inmonazite sands (Ce, La, etc.) PO4] and in bastnasite [(Ce, La, etc.)(C03)F] (see Section 1.7.1). Yttrium is extracted together with other rare earth elements in a concentrated solution of sodium hydroxide at 140-150 °C after cooling, the hydroxides of the rare earth elements are separated by filtration. Alternatively, bastnasite may be calcined to drive off CO2 and fluorine, and then leached with hydrochloric acid to dissolve the trivalent rare earth elements. The rare earth hydroxides and chlorides obtained in this way are further processed to produce individual rare earth metal compounds... 

Corrosion inhibition with rare earth metal compounds in aqueous solutions... 

The spectroscopic properties of lanthanide ions have already been the subject of several chapters in this series, The atomic lanthanide spectra and the theoretical methods for free-ion energy level calculation were reviewed by Goldschmidt (1978). Fulde (1979) considered the crystal fields in rare-earth metallic compounds. Attention was given to the determination of crystal-field parameters in opaque materials, for which no optical methods can be used. In a chapter concerning the complexes of the rare earths, Thompson (1979) paid attention to the spectroscopic properties of coordination compounds. Camall (1979) discussed the absorption and fluorescence spectra of rare-earth ions in solution. Weber s contribution (1979) treated rare-earth lasers and that of Blasse (1979) treated phosphors activated by lanthanide ions. Morrison and Leavitt (1982)... 

Related to these catalysts are the systems based on lanthanide metal systems or rare earth metal complexes [46, 47]. The main problem with these catalyst systems is their instability. When the catalyst solution is prepared by reachng a metallocene with an organolithium compound in a polar solvent, the prepared catalyst soluhon is unstable and decomposes quickly, even under a nitrogen atmosphere. The activity of these catalysts can be high only if the catalyst is added to the polymer soluhon immediately after preparation. Attempts have been made to overcome the stability problem by using an additive in the system to improve the stability and the activity of the catalyst [33-35, 41, 57, 58, 61]. Re-... 

Arsenites of the Rare Earth Metals.—When cerium dioxide is heated with arsenious oxide some oxidation of the latter occurs, but the product appears to be a mixture of oxides.5 Didymium hydrogen orthoarsenite, Di2(HAs03)3, has been obtained6 as a white, granular, insoluble powder by boiling didymium hydroxide with an aqueous solution of arsenious oxide. Lanthanum hydrogen orthoarsenite, La2(HAs03)3, has been prepared in a similar manner. The existence of these compounds needs confirmation, however.7... 

Solution grafting has been the predominant approach for the immobilization of rare-earth metal precatalyst components [288]. The identification of the catalytically active surface species, commonly formed upon interaction with organoaluminum compounds, is difficult and assisted by molecular model complexes. Several types of support materials including magnesium chloride [289], silica [290], and organic (co-)polymers [291,292], were examined both in the gas-phase and the slurry polymerization of 1,3-dienes. 

The merocyanine form of numerous BIPS compounds in solution complex with many transition and rare-earth metal ions. The complexation between 6-nitro-8-methoxyBIPS and several ions was studied by spectrophotometric, luminescent, stopped-flow, and nanosecond laser flash photolysis techniques. The absorption maximum of the dye, 580 nm, is shifted to the 480-500 nm region, and the relatively weak fluorescence shows a similar hypsochromic shift. The kinetics of the complexation involved a fast reaction between the components, followed by a slow equilibrium of the complex to its most stable isomer. The photoreactions of the complexes include formation of a short-lived triplet state (lifetime about 2 x 10 5 s,... 

Traditional Lewis acids such as AICI3 or BFj OEt2 catalyze key steps in many reactions involving carbonyl compounds, leading to carbon-carbon bond formation. Because of their reactivity and instability these catalysts cannot be used in aqueous solution. For this area of application, rare earth metal catalysts open up new perspectives. 

The conductivities of some ceria-containing compounds obtained from the literature have been compiled and shown as solid lines in Fig. 2.12. The main dopants for ceria belong to the alkaline earth or rare-earth metal series and the majority of doped samples exhibit conductivity values which fall into a rather limited band (gray band in Fig. 2.12), which points to a similar behaviour for all doped ceria samples. Exceptions are pure ceria and ceria doped with redox elements like Pr and Tb which give rise to electronic contribution to conductivity. An important requirement is that a homogeneous solid solution forms between the two oxides, which maintains the fluorite structure since the presence of a second phase or phase inhomogeneity due to insufficient solubility can affect ionic conductivity. The very low values of conductivity found for BaO and MgO-doped ceria were in fact attributed to the low solubility of these oxides into the lattice of When the... 

Carnall, W.T., 1979. The absorption and fluorescence spectra of rare earth ions in solution. In Gschneidner Jr., K.A., Eyring, L. (Eds.), Handbook on the Physics and Chemistry of Rare Earths Non-Metallic Compounds I, vol. 3. North-Holland, Amsterdam, pp. 171-208 (Chapter 24). 

As we shall see, there are now other rare-earth elements that are stable enough in the divalent state in solution, allowing for the successful isolation of molecular complexes that can be fully characterised, including structurally, and their reactivity studied. Recent reviews and highlights have partially addressed this topic (Bochkarev, 2004 Cassani et al., 2002 Evans, 2000, 2002a,b, 2007 Izod, 2002 Meyer, 2008). Eurthermore, there are a few reports on low-valent scandium complexes, and also a number of extremely reactive zero-valent rare-earth molecular compounds that could only be made via metal vapour techniques, which have been reviewed some time ago (Cloke, 1993). 

In the 1950s Huber and Holley and their co-workers carried out combustion calorimetry studies with most of rare earth metals. Later the same group re-studied some of the compounds with combustion calorimetry, but also used solution calorimetry to check their earlier combustion calorimetry results. 

Good, precise data on the thermodynamic and other properties of such solutions can give the theorists material for understanding the nature of electrolytes and this is extremely important, since the ocean is an electrolyte and electrolytes play a very important role in most life processes. To sum up, the properties of the various rare earth metals, alloys and compounds can vary widely so that it is possible to pick one of these materials which possesses almost... 

Another feature of the systems of this subgroup is the large extent of the limited solid solutions. Differences in the crystal chemistry characteristics of the rare-earth metals in the systems considered are insignificant, but they influence composition, structure and the number of ternary compounds. Ternary compounds with the composition Sco.3Ro.7Ge2 (R=Y, Dy) were found to exist for the Sc and Ge ternaries with Y and Dy on the digermanide section. They have no equivalent in other... 

As one can see from the present review, rare-earth metals show very similar crystal chemistry that is displayed in the formation of continuous solid solutions as well as substitutional solid solutions. On the other hand, differences in electron configuration of the rare-earth atoms influence the interactions in the ternary systems, as shown by different compositions, structures and the number of ternary compounds. 

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