Chemical properties of rare earth

Surface Chemical Properties of Rare Earth Sesquioxides... 

PHYSICAL AND CHEMICAL PROPERTIES OF RARE EARTH OXIDES... 

To better imderstand the physical nature of the rare earth perovskite materials availability of detailed information about their crystal structures is the key. The above-mentioned physical and chemical properties of rare earth aluminates... 

Therefore, our purpose is to demonstrate that the physical and chemical properties of rare earth metallic and rare earth alloy thin films or single-crystals must be cautiously analyzed. Particularly, the lack of crystallographic spectra (X-ray or electron diffraction), of chemical analyses (absorbed or adsorbed gases, surface contamination, impurities,...), of structural investigations (grain size, defects,. ..) for example, is truly detrimental to precise characterization of the materials. In this way one can claim that numerous... 

Physical and chemical properties of rare earth vanadates... 

RARE-EARTH ELEMENTS AND METALS. Sometimes referred to as the fraternal fifteen," because of similarities in physical and chemical properties, the rare-earth elements actually are not so rare. This is attested by Fig. 1, which shows a dry lake bed in California that alone contains well in excess of one million pounds of two of die elements, neodymium and praseodymium. The world s largest rare earth body and mine near Baotou, Inner Mongolia, China is shown in Fig. 2. It contains 25 million tons of rare earth oxides (about one quarter of the world s human reserves. The term rare arises from the fact that these elements were discovered in scarce materials. The term earth stems from die tact that the elements were first isolated from their ores in the chemical form of oxides and that the old chemical terminology for oxide is earth. The rare-earth elements, also termed Lanthanides, are similar in that they share a valence of 3 and are treated as a separate side branch of the periodic table, much like die Actinides. See also Actinide Contraction Chemical Elements Lanthanide Series and Periodic Table of the Elements. 

In addition to the orthophosphates, there are also a small number of reports on nanomaterials of other rare earth phosphate salts (Tang et al., 2005c). In this section, we will discuss the chemical synthesis of rare earth orthophosphates in aqueous solutions, nonaqueous solutions, and dry methods, together with the brief discussion of the luminescent properties, as well as the applications in biosensing. 

Rare-earth nanomaterials find numerous applications as phosphors, catalysts, permanent magnets, fuel cell electrodes and electrolytes, hard alloys, and superconductors. Yan and coauthors focus on inorganic non-metallic rare-earth nanomaterials prepared using chemical synthesis routes, more specifically, prepared via various solution-based routes. Recent discoveries in s)mthesis and characterization of properties of rare-earth nanomaterials are systematically reviewed. The authors begin with ceria and other rare-earth oxides, and then move to oxysalts, halides, sulfides, and oxysulfides. In addition to comprehensive description of s)mthesis routes that lead to a variety of nanoforms of these interesting materials, the authors pay special attention to summarizing most important properties and their relationships to peculiar structural features of nanomaterials s)mthesized over the last 10-15 years. 

There are many kinds of magnetic nanoparticles due to different chemical properties metals, rare earth metals, oxidation of metallic nanoparticles, and magnetic alloys. Since the metal nanoparticles include most of the metal magnetic materials and oxidation of metallic nanoparticles, the following section will focus... 

The information about nanocrystalline ferroic powders fabricated by various chemical synthesis technologies is reported in Table 5.2. Their possible applications are also listed. Powders of the same ferroics for two different applications might be obtained by different techniques since the requirements of size distribution, morphology, agglomeration and impurity composition are determined by different technological conditions. For example, barium titanate is a dielectric with high dielectric constant and it is widely used in multilayer ceramic capacitors, whereas semiconducting properties of rare-earth doped BaTiOs are important for thermistors. 

The chemical and spectroscopic properties of rare earths represent one extreme, to which (loosely said) organic chemistry constitutes the opposite, with the multi-... 

The fact that dielectric and structural properties of rare earth aluminates fulfil the demands of microwave engineering, even though some other properties (primarily the formation of twins and chemical purity of precursors) are unfavourable, should continue to support a considerable interest in the attempts to tailor new varieties of aluminate crystals. 

Scandium, yttrium, and the lanthanide mettils comprise 17 elements for which systematically-determined mechanical property data are sparse. Pioneering work on the mechanical properties of rare earth metals was done in the mid to late 1950 s and was conducted almost exclusively by three groups B. Love and associates at Research Chemicals, Inc. C.R. Simmons and associates at General Electric Co. and E.M. Savitskiy and associates in the USSR. Since that time the number of investigations has increased and the property values have changed considerably with improvements in metal purification methods. 

Selected properties of rare-earth elements and lanthanides are listed in Table 4.111, while for other properties it is recommended to consult the table of properties of the chemical elements in Section A.5. 

In contrast to other lasers where the active ion is dispersed in a crystalline or glassy host, stoichiometric materials are pure chemical compounds of rare earths. Therefore, there is no question of rare earth ion size, charge, or coordination to be considered as in other laser materials. Also, since the rare earth is not a dilute substitutional impurity, the inhomogeneous broadening is very small and there is no statistical distribution of ion-ion separations. Other spectroscopic properties, including intensities and cross sections, are similar to those in other crystalline hosts. 

Evdokimov, V.I., Baluev, A.V., Sapegin, A.M., 1984. Mass Spectrometric Investigation of Thermochemical Properties of Rare Earth Element Chlorides. Report No. 800 637, Institute of New Chemical Problems, Chemogolovka (in Russian). 

All REE have the same configuration of outer electrons and, as these electrons predominantly determine chemical properties, the rare earths possess similar chemical and physical attributes. The REE exhibit diamagnetism due to their completed subshells and successive filling of the 4f subshell gives rise to the characteristic paramagnetic properties of the middle and heavy rare earths. 

In the context of writing his Principles of Chemistry textbook, Mendeleev formulated his first version of the periodic system of chemical elements in the first two months of 1869. He would spend the next two years elaborating upon this system, expanding the scope and utility of the system in a variety of ways classification of peroxides, the properties of rare earth metals, and, especially, the detailed prediction of properties of three yet-undiscovered chemical elements, which he named eka-aluminum, eka-boron, and eka-silicon. After the publication of these predictions in his most detailed article on the chemistry of the periodic system in 1871 [Mendelejew, 1871], Mendeleev attempted briefly to experimentally discover these elements himself, but quickly abandoned the project by the end of that calendar year. 

Although rare-earth ions are mosdy trivalent, lanthanides can exist in the divalent or tetravalent state when the electronic configuration is close to the stable empty, half-fUed, or completely fiUed sheUs. Thus samarium, europium, thuUum, and ytterbium can exist as divalent cations in certain environments. On the other hand, tetravalent cerium, praseodymium, and terbium are found, even as oxides where trivalent and tetravalent states often coexist. The stabili2ation of the different valence states for particular rare earths is sometimes used for separation from the other trivalent lanthanides. The chemicals properties of the di- and tetravalent ions are significantly different. 

Lanthanides properties and general references. For a systematic treatment and general references of the physical and chemical properties of the rare earths and their compounds and alloys mention can be made to a periodical publication in which several contributions to these subjects are being collected. See for instance Gschneidner and Eyring (1978) and Gschneidner etal. (2005). We would also like to quote a sentence, included in the prefaces of all these books, which hints at the complexity and richness of the rare earth behaviour and the ever-increasing interest in their properties and applications. The mentioned sentence is as follows ... 

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