Rare earth physical characteristics

Characteristic initiation behavior of rare earth metals was also found in the polymerization of polar and nonpolar monomers. In spite of the accelarated development of living isotactic [15] and syndiotactic [16] polymerizations of methyl methacrylate (MMA), the lowest polydispersity indices obtained remain in the region of Mw/Mn = 1.08 for an Mn of only 21 200. Thus, the synthesis of high molecular weight polymers (Mn > 100 x 103) with Mw/Mn < 1.05 is still an important target in both polar and nonpolar polymer chemistry. Undoubtedly, the availability of compositionally pure materials is a must for the accurate physical and chemical characterization of polymeric materials. 

As the first element in the third series of the transition elements, hafnium s atomic number ( jHf) follows the lanthanide series of rare-earths. The lanthanide series is separated out of the normal position of sequenced atomic numbers and is placed below the third series on the periodic table ( La to 7,Li). This rearrangement of the table allowed the positioning of elements of the third series within groups more related to similar chemical and physical characteristics—for example, the triads of Ti, Zr, and Hf V, Nb, andTa and Cu, Ag, and Au. 

AH the isotopes of americium belonging to the transuranic subseries of the actinide series are radioactive and are artificially produced. Americium has similar chemical and physical characteristics and is hofflologous to europium, located just above it in the rare-earth (lanthanide) series on the periodic table. It is a bright-white malleable heavy metal that is somewhat similar to lead. Americiums melting point is 1,176°C, its boiling point is 2,607°C, and its density is 13.68g/cm. ... 

This type of research uses pulsed and tunable lasers as an excitation source. The rare-earth ion is excited selectively, and its decay is analyzed. The shape of the decay curve is characteristic of the physical processes in the compound under study (9). For a detailed review the reader is referred to the literature (S). Here we give some results for... 

The lanthanide series of metals includes the 15 elements with atomic numbers 57-71, plus yttrium (atomic number 39). The lanthanides occur in the earth s crust at concentrations exceeding some commonly used industrial elements making the term rare earths something of a misnomer. For example, yttrium, cerium, lanthanum, and neodymium are present in the earth s crust at higher concentrations than lead. Of the 15 lanthanides, only promethium does not occur in nature - it is a man-made element. All of the lanthanides have similar physical and chemical properties. Because of similarities in their chemistry and toxicity, the characteristics of the lanthanides are often described as a group. Within the lanthanide group, however, there are differences between the toxicity of the individual lanthanide elements and their compounds. 

The binary rare earth oxides bring us a variety of interesting characteristics and understanding of their fundamental mechanisms builds a bridge between solid state chemistry and materials science. This book is the first monograph to cover the whole aspects of the binary rare earth oxides, which provides a comprehensive introduction to the unique characteristics of the binary rare earth oxides with their chemistry, physics and applications. 

In the first half of this book, chemical stability, reactivity, structural features, and chemical bonding including band calculation of the rare earth oxides, have been examined from the viewpoints of the fundamental characterization and appearance mechanism of the properties. Particularly, further development of high resolution electron microscopy (HREM) and quantum band calculation will be of great aid for us to understand the unique characteristics of binary rare earth oxides from both the experimental and theoretical approaches. In addition, physical and chemical properties of the rare earth oxides such as electrical, magnetic, optical, and diffusion properties are also analyzed in details, leading to find relationships between basic science and applications in several functional materials. 

In order to detect small deviations from stoichiometric composition, physical properties such as electrical, magnetic, or optical characteristics provide us a valuable information. The measurements of physical properties described above are commonly used with many other systems where variations in stoichiometry appear in compounds as well as with rare earth oxides. 

In conclusion, it can be said that the rare earth diborodicarbides have a variety of peculiar physical properties because of their characteristic crystal or band structures and may be exploited as a new type of material. 

Perovskite-type rare earth aluminates are also prospective materials for deposition of GaN and AIN layers and manufacturing of blue light semiconductor lasers, as well as epitaxial layers of HTSC materials. LaAlOs and LSAT (Lai j Srj Ali yTay03) are well known in this respect. The application of a material as a substrate requires the knowledge of its physical characteristics and their temperature evolution in addition to the standard condition, which is the minimum mismatch between the cell parameters of the deposited film and the substrate. For details refer to O Bryan et al. (1990). 

Elastic properties serve an obvious utility in mechanics of materials, e.g., stress-strain relations and dislocation characteristics (Fisher and Dever, 1967 Fisher and Alfred, 1968). Moreover, elastic properties and their temperature dependencies provide important information and understanding of such physical characteristics as magnetic behavior, polymorphic transformations, and other fundamental lattice phenomena. In this section the elastic properties and their temperature dependencies are presented for all the rare earth metals except promethium, for which there is no data. To the writer s knowledge this is the first one-source compilation of the temperature dependencies of the elastic properties of the rare earth metals. 

In recent years a new class of materials rare earth compounds (RECs) has been investigated intensively. These materials possess nonstandard physical properties, including the thermal conductivity. New features were observed in Kl, and ic. Analysing data on the thermal conductivity of RECs, in this review we will try to attract more attention to nonstandard effects characteristic of the solids containing ions with f-electrons. 

The discovery of new physical effects in intermetallic compounds, such as intennediate valence, heavy fermions and Kondo systems, coexistence of magnetism and superconductivity, etc., has stimulated much interest in these materials. It is also necessary to mention the powerful permanent magnets based on rare-earth intermetallides. A complex approach to the investigation of the composition, crystal structure and properties of these intermetallic compounds has been outlined and gives the possibility of solving the important problem of the determination of correlations between these characteristics. 

In view of the importance of high-temperature superconductivity in the layered cuprates and the role played by the rare earths, it seemed appropriate to prepare these volumes of the Handbook on the Physics and Chemistry of Rare Earths on High-Temperature Superconductivity in Layered Cuprates . We believe that researchers already working in this field, as well as those intending to enter this field, will find valuable information in the review articles contained in these volumes. Since many of the cuprate superconductors do not contain rare-earth or actinide elements, yet have characteristics and properties similar to those that do, the range of materials considered in these volumes has been broadened to a limited extent to include all high-temperature cuprate superconductors, irrespective of whether they contain rare-earth or actinide elements. 

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