Pure rare earth metals and

These problems have of course different weights for the different metals. The high reactivity of the elements on the left-side of the Periodic Table is well-known. On this subject, relevant examples based on rare earth metals and their alloys and compounds are given in a paper by Gschneidner (1993) Metals, alloys and compounds high purities do make a difference The influence of impurity atoms, especially the interstitial elements, on some of the properties of pure rare earth metals and the stabilization of non-equilibrium structures of the metals are there discussed. The effects of impurities on intermetallic and non-metallic R compounds are also considered, including the composition and structure of line compounds, the nominal vs. true composition of a sample and/or of an intermediate phase, the stabilization of non-existent binary phases which correspond to real new ternary phases, etc. A few examples taken from the above-mentioned paper and reported here are especially relevant. They may be useful to highlight typical problems met in preparative intermetallic chemistry. 

Industrial Applications of Pure Rare Earth Metals and Related Alloys... 

Several different processes have been studied with two different objectives in mind - preparation of pure rare earth metals and the preparation of master alloys. 

The rare earth metals exhibit a variety of ordered states from ferromagnetic to complicated antiferromagnetic structures collinear, spiral, helical, conical and fan structures, which can be altered by temperature, magnetic fields or by the application of pressure (Nikitin et al., 1972). These complicated arrangements of spins result from the balance in energy between magnetocrystalline anisotropy and exchange forces (Elliott, 1965). Much pressure work has been done on pure rare earth metals and alloys in the last decade especially, and measurements... 

Shiflet et al. (1979) combined the Kaufman approach with values of the enthalpies and entropies of melting and transformation of the pure rare earth metals and calculated the phase diagram for the Tb-Er system. The peritectic point in the... 

Metal catalysts are useful to increase EMF yields. Alloys containing both the target rare earth metal and nickel, such as YNi2 and GdNi2, are commonly used for production of EMFs with pure metals [65, 66]. Regarding the catalysts used to promote the yield of TNT EMFs, CoO was first adopted but no obvious enhancement was observed [50]. The addition of YNi2 alloy only improved the formation of carbon nanotubes. Recently, copper was found to be very effective for promotion of the overall yield of Sc3N C2n [67]. 

Suspensions of HTSC for the electrophoretic deposition of bismuth [403-409] and thallium [403] HTSC, various cuprates of rare-earth metals and barium [204, 407,410-414], and also silver HTSC [415,416] and PbO-HTSC [417] compositions have been used. These are prepared in acetone, acetonitrile, toluene, butanol, methylethylketone, or mixed solvents. They contain chemically pure materials (silver is introduced as AgaO) dispersed thoroughly, first mechanically and then in liquid) by ultrasonic treatment (in which case the particles became charged). The choice of solvent is by and large determined by its effect on the stability of the deposited oxide [417]. 

Zone melting causes impurities to migrate to one end of a cylindrical metal sample by generating a narrow molten zone and moving it repeatedly in one direction along the cylinder axis. Impurities more soluble in the liquid phase (metals, some halides, and carbon) move in the direction of zone travel, while those more soluble in the solid (interstitials) move in the opposite direction. This technique produces pure rare earth metals . ... 

The metallographic examination of the pure rare-earth metals must be differentiated from the examination of impure rare earth metals which have a large quantity of second phase impurities. The preparation of impure metals for metallographic examination must take into account second-phase particle retention, the reactivity of the second phase and its hardness in addition to the properties of the pure metal. 

Spedding, F.H., B.J. Beaudry, J.J. Croat and P.E. Palmer, 1968a, The properties, preparation and handling of pure rare earth metals, in Materials Technology - An Inter-american Approach (Am. Soc. Mech. Eng., New York) p. 151. 

The second difficulty was that it was difficult to obtain pure metal reductants, so that as the metal was reduced with potassium or calcium, all the impurities in these materials would end up in the rare earth metal, and finally it was difficult to get pure rare earth salts. The laborious process needed to isolate these elements meant that except for cerium and lanthanum, usually only small samples could be obtained. They were almost certain to contain several rare earths. As a result of these difficulties, most of the metal made in the earlier years was extremely impure and many of the properties reported for a particular rare earth were likely to be in error. 

The electron wave vectors at the Fermi level in metals are more likely, rather than the wave vectors of phonons, to make a significant contribution to the heat transport. These phonons can interact with electrons, and thus, an effect of phonon-electron scattering is to be expected in metals at all temperatures. One fails, however, to observe phonon-electron scattering in pure metals at high temperatures because of the complexity of the Kl separation. One can separate and and observe phonon-electron scattering in rare earth metals and metal-like compounds which contain rare earth elements, due to the low mobility of electrons which increases p considerably and hence decreases k ) (Oskotski and Smirnov 1971, Khusnutdinova et al. 1971, Luguev et al. 1975a). 

Crystal structures, lattice constants, atomic volumes and radii 1.2.1. Pure rare earth metals... 

Lattice spacings in the praseodymium-yttrium system have been measured by Harris et al. (1966). Their alloys were prepared from praseodymium and yttrium, which each contained less than 0.10 wt% other rare earth metals and 0.1 wt% Ta. Their praseodymium and yttrium contained 0.02 and 0.03 wt% total common metals, respectively. The weighed portions of the pure metals were arc-melted under purified argon, homogenized at 800°C and quenched. Filings for X-ray diffraction analysis were stress-relieved before exposure to Cu-, Co- or Cr-Ka radiation. Systematic errors were eliminated by use of the Nelson-Riley extrapolation function. 

Many recent developments in the investigation of rare earth intermetallic compounds have only been made possible either by the availability of pure rare earth metals, or of possibilities to prepare single phased intermetallic compounds. Also developments with respect to the determination of crystal structures etc. and new scientific and experimental techniques for investigations of magnetic properties, which are essential to our present knowledge of the magnetic properties of intermetallic compounds will not be mentioned explicitly. 

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