Journal of the Less Common Metals (J Less Common Met )

Publisher: Elsevier

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Current impact factor: 2.73

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Website Journal of the Less-Common Metals website
Other titles Journal of the less-common metals, Journal of the less common metals
ISSN 0022-5088
OCLC 1782919
Material type Periodical, Internet resource
Document type Journal / Magazine / Newspaper, Internet Resource

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Elsevier

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Publications in this journal

  • [Show abstract] [Hide abstract]
    ABSTRACT: The problem of bonding in actinide solids has been approached through the establishment of semi-theoretical correlations between thermodynamic and structural properties and the degree of participation to the bond of the different electronic orbitals of the actinide atom. The first part of the chapter is devoted to an analysis of these correlations, as well as to the presentation of the most important experimental results. In a second part the following stage of development is reviewed, i.e. the introduction of more quantitative theories mostly based on bond structure calculations. These theories are given a thermodynamic form (equation of states at zero temperature), and explain the typical behaviour of such ground state properties as cohesive energies, atomic volumes, and bulk moduli across the series. They employ in their simplest form the Friedel model extended from the d- to the 5 f-itinerant state. The Mott transition (between plutonium and americium metals) finds a good justification within this frame. In actinide binary compounds an equation of state can also be developed on the same lines. The difference in electronegativity of the actinide and the non-actinide element plays an important role, determining the degree of mixing between the actinide orbitals (5 f and 6 d) and the orbitals of the ligand. A mixture of metallic, ionic and covalent bond is then encountered. In the chapter, two classes of actinide compounds are reviewed: NaCl-structure pnictides or chalcogenides, and oxides. In oxides a large departure from the stoichiometric composition is usually met. The importance of this phenomenon, also for the understanding of the oxide bond, is highlighted at the end of the chapter.
    08/2007: pages 75-126;
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    ABSTRACT: The dissociation kinetics of 1,7-diaza-4,10,13-trioxacyclopentadecane-N,N'-diacetic acid (K21DA) complexes of lanthanide(III) ions were studied in acetate-acetic acid buffer medium, over the acid concentration range of 8.4 x 10⁻⁶-2.5 x 10⁻⁴ M and at a constant ionic strength of 0.1 M (LiClOâ). Copper(II) was used as the scavenger of free ligand, and the rates of dissociation of these complexes have been found to be independent of (Cu/sup 2 +/). All the complexes exhibit acid-independent and acid-dependent pathways. Lighter lanthanide complexes display a first-order dependence upon (H/sup +/) in the pH range studied. The complexes of heavier lanthanides show (H/sup +/) dependence at low acid concentrations but become acid-independent at high acid concentrations. Influence of acetate content in the buffer and total electrolyte concentration on the rate of dissociation has also been investigated. The observed rate constants for erbium, ytterbium, and lutetium complexes do not show a significant dependence on acetate concentration, but lanthanum and europium complexes do exhibit a first-order dependence on (acetate). All the complexes under study respond similarly with change in electrolyte concentration; i.e., the rate constants decrease with increase in (electrolyte). Activation parameters for both self-dissociation and acid-catalyzed dissociation pathways have been obtained for lanthanum, europium, erbium, and lutetium complexes, from the temperature dependence of rate constants in the 15-45 °C range. The results are compared with those of the lanthanide-polyamino polycarboxylate systems, and possible mechanisms are discussed. 41 references, 4 figures, 6 tables.
    Journal of the Less Common Metals 04/2002; 25(12).
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    ABSTRACT: A combination of anion exchange separation, electrolytic extraction, floating zone refining and dry hydrogen treatment was used to purify cobalt. The effectiveness of each purification process was confirmed by measurements of the residual resistivity ratio (RRR) and activation analyses. Proton activation analysis revealed that all the main metallic impurities except iron were effectively removed by a combination of these processes. The effective removal of oxygen, nitrogen and carbon by dry hydrogen treatment was confirmed by activation analyses using 3He ion beams, proton beams and γ rays. It was found that the rate-controlling step in the decarburization process was a surface reaction. The maximum RRR obtained for the purified specimen was 334, which is higher than previously reported values.
    Journal of the Less Common Metals 01/2002; 105(2):211-220.
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    ABSTRACT: The PtGaAs solid state equilibrium phase diagram was determined at 600 °C with the use of X-ray powder diffraction, electron probe microanalysis (EPMA) and scanning electron microscopy (SEM). No ternary PtGaAs phases were found and limited solid solubility was measured in the constituent binary PtGa and PtAs compounds. GaAs, PtGa and PtAs2 form a region of three-phase equilibrium which dominates the GaAs side of the phase diagram. The phase diagram is in agreement with previous observations that PtGa and PtAs2 are the stable phases when platinum thin films are reacted to completion on GaAs.
    Journal of the Less Common Metals 01/1993; 146:233-239.
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    ABSTRACT: The electrochemical behaviour of hexavalent uranium is reported in various organic solvents at room temperature and also in hexamethylphosphoramide, dimethylsulphone, sulpholane between 310 and 400 K. The reduction of UO22+ proceeds in two steps, leading to tetravalent uranium. Depending on the solvent acidity, the tetravalent species is either soluble or precipitates as UO2(cr). Numerous additional kinetic phenomena are evidenced in all the reactions.Special attention is paid to the deposition of UO2(cr) in macroscopic quantities.
    Journal of the Less Common Metals 07/1992;
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    ABSTRACT: The solid solution system U(Mn1−xFex)2Si2 (0 ⩽ x ⩽ 1) was synthesized by direct melting of the UMn2Si2 and UFe2Si2 components and investigated by X-ray diffraction, magnetometric and Mössbauer effect methods. The series investigated behaves similarly in many respects to the isostructural ones formed with other elements. The values of the lattice constants obey Vegard's law. The isomer shift and quadrupole splitting vary gradually across the range of iron concentration. The quadrupole splitting reflects a deviation from the ideal tetrahedral coordination of iron site neighbours. The manganese-rich samples (x ⩽ 0.3) were found to be ferromagnets at 78 K while the others behave as Pauli paramagnets above 78 K. The Curie temperature and hyperfine magnetic field decrease strongly with increasing iron concentration. The composition dependence of the Curie temperature is well described by the Heisenberg model in which the magnetic interactions between nearest neighbours and the uniaxial magnetic anisotropy were taken into account.
    Journal of the Less Common Metals 10/1991; 175(2):259-265.
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    ABSTRACT: Previous observations have shown smaller grain sizes and higher strengths in W-Ni-Fe heavy alloys containing molybdenum. This study focuses on the microstructure and grain growth kinetics for the W-Mo-Ni-Fe system processed at 1500 °C. The initial rate of grain growth follows an approximate square root time dependence in contrast to the cube root dependence typical for W-Ni-Fe alloys. Microprobe measurements show that chemical gradients are present in the solid grains, with high molybdenum content cores. The retarded grain growth from molybdenum additions is the result of a decreased tungsten solubility in the liquid during the early stages of sintering.
    Journal of the Less Common Metals 10/1991;
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    ABSTRACT: The oxidation of ZrAl3 in dry oxygen in the temperature range 865–1073 K obeys a logarithmic rate law in the first period of reaction. An activation energy of 214 kJ mol−1 has been estimated. Some time after this first period, depending on the temperature, the protective oxide film transforms to a porous one and the reaction rate increases. The oxide layer consists of α-Al2O3, tetragonal ZrO2 and small amounts of monoclinic ZrO2, in contrast to the ZrO2 oxide layer formed during oxidation of other phases in the Zr-Al system, where the selective oxidation of zirconium takes place.
    Journal of the Less Common Metals 10/1991; 175(2):289–294.
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    ABSTRACT: Two types of lanthanide- acetate-chloride hydrates, [M(CH3COO)(H2O)6]Cl2 · H2O (M  La-Sm) and [M(CH3COO)2(H2O)3]Cl (M  Ce-Lu, Y), are obtained by the reaction of the chloride hydrates MCl3 · xH2O (x = 7, 6) and the oxychlorides MOCl respectively with and in acetic acid (solution). The first compound type contains cationic dimers o∞{[M(CH3COO)(H2O)6]2}4+ and is therefore called “type 0” (0 for zero dimensional). The characteristic structural feature of the latter is a cationic chain 1∞[M(CH3COO)2(H2O)3]+; it is a “type 1” compound (1 for one dimensional). All compounds were characterized by X-ray powder diffraction (Guinier method) and their thermal behaviour was investigated by thermal analysis.
    Journal of the Less Common Metals 10/1991; 175(2):301-308.
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    ABSTRACT: The magnetic properties and phase components of rapidly quenched Fe77.5Nd4B18.5 alloy as a function of quenching rate and heat treatment were studied. X-ray diffraction and thermomagnetic measurements show that the Fe77.5Nd4B18.5 ingot consists of Nd2Fe14B, Fe2B and α-Fe. The X-ray diffraction patterns of optimally annealed samples show only metastable Fe3B phase which decomposes into Fe2B and α-Fe at Ta > 850 °C, but the thermomagnetic curves show the presence of the Nd2Fe14B phase. In the sample annealed at 950 °C for 60 min, Nd1.1Fe4B4 appears in coexistence with Nd2Fe14B, Fe2B and α-Fe. The Fe77.5Nd4B18.5 alloy is found to have very good glass-forming ability. Samples prepared at quenching rates vs ⩾ 6.6 m s−1 are amorphous and magnetically soft. Annealing at about 650–670 °C gives the highest coercive field, which is nearly independent of quenching rate.
    Journal of the Less Common Metals 10/1991; 175(2):199-204.
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    ABSTRACT: The system Ce-Sn has been reinvestigated in the temperature range from 400 to 800 °C using X-ray powder diffraction techniques. From a characterization of its crystal structures the existence of nine binary compounds has been confirmed.Magnetic investigation of the binary cerium stannides in the temperature range from 4.2 to 600 K revealed a systematic tendency for ferromagnetic ordering of the ceriumrich compounds up to a ratio Ce:Sn ≈ 1, followed by antiferromagnetism up to a ratio of Ce:Sn ≈ 0.4, towards interconfigurational fluctuation in the compound richest in tin, CeSn3. Candidates for heavy fermion behaviour found in the transition regions, besides CeSn3, are α-Ce5Sn3 and Ce11Sn10.
    Journal of the Less Common Metals 10/1991; 175(2):331-338.
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    ABSTRACT: The Invar alloy La(FexAlx−1)13 with NaZn13-type cubic structure was prepared. Using single crystals of CaF2 as solid electrolyte, the activity and the relative partial molar Gibbs free energy of lanthanum in La(FexAl1−x)13 alloys were determined by the e.m.f. method over the temperature range 983–1085 K. The melting point and the phase transition temperature of two La(FexAl1−x)13 alloys were measured by differential thermal analysis. The average molar heat capacity was measured using a high temperature microcalorimeter in the temperature range 416–610 K.
    Journal of the Less Common Metals 10/1991; 175(2):271-278.
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    ABSTRACT: For the first time, single crystals of SrHgO2 have been prepared by a high pressure oxidation technique. X-ray investigations indicate that the crystals have trigonal symmetry, space group D36-P3221 (no. 154), with , and Z = 3. Hg2+ has a coordination number of two, while Sr2+ is surrounded by six oxygen ions. Two-dimensional layers of edge-linked SrO6 octahedra are connected by O-Hg-O dumb-bells. SrHgO2 belongs to the delafossite-type structure.ZusammenfassungUnter hohem Sauerstoffdruck ist es erstmals gelungen, SrHgO2 einkristallin darzustellen und mit Röntgenmethoden die Kristallstruktur zu bestimmen. Es kristallisiert trigonal, Raumgruppe D36-P3221 (No. 154), mit den Achsen , und Z = 3. Hg2+ ist von O2− zweifach, Sr2+ sechsfach koordiniert. Lineare O-Hg-O-Hanteln verknüpfen zweidimensionale Schichten kantenverknüpfter SrO6-Oktaeder. SrHgO2 gehört zum Delafossittyp.
    Journal of the Less Common Metals 10/1991; 175(2):295-299.
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    ABSTRACT: Crystals of a new intermetallic compound, Ca7Ni4Sn13, have been prepared. The refined structure was solved in the P4/m space group, Z = 1 with lattice constants and , R = 2.8% and Rw = 2.4%. This new structure type consists of an Sn-Ni network forming channels parallel to the c axis which are filled with calcium atoms. Temperature-dependent magnetic and conductivity studies show Ca7Ni4Sn13 to be Pauli paramagnetic with simple metallic behavior.
    Journal of the Less Common Metals 10/1991; 175(2):339-346.
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    ABSTRACT: Dark red-brown CsUCl4 · 3H2O crystallizes in the monoclinic crystal system (a = 711.6(1) pm, b = 867.2(2) pm, c = 807.1(2) pm; β = 99.28(3)°, space group , Z = 2). Uranium has a coordination number of nine (tricapped trigonal prism) consisting of six chlorine atoms and three oxygen atoms (representing water) with mean distances of 295.7 and 255.2 pm respectively. Caesium is surrounded by eight chlorine atoms in the shape of a distorted cube which is capped by two water ligands, the mean Cs-Cl distance being 360.2 pm.
    Journal of the Less Common Metals 10/1991; 175(2):347-352.
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    ABSTRACT: The low temperature specific heats of C-15 structure UOs2 and UOsIR have been measured in order to compare them with the systems NpOs2, a ferromagnet with TCurie = 7.9 K, and NpOsIr, newly discovered to be a spin fluctuation system with a specific heat γ of 375 mJ mol−1 K−2. The uranium compounds, with U—U separations of 3.25 Å, less than the Hill limit of 3.4 Å, show normal metallic behavior, with γ(UOs2) = 20 ± 2 mJ mol−1K−2 and γ(UOsIr) = 33 ± 3 mJ mol−1 K−2.
    Journal of the Less Common Metals 10/1991; 175(2).
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    ABSTRACT: Oxidation of reduced chlorides (KM2Cl5; M  Nd, Sm) or chloride-hydrides (MClH0.67; M  La, Ce, Pr) of the lanthanides with sulphur in the presence of NaCl in the latter case (tantalum capsule, 850 °C, 7 days) results in the formation of binary sulphides and ternary chlorides with potassium and sodium respectively, both with trivalent cations (M3+), as the main products. Oxidic impurities (e.g. MOCl) react to yield M10S14O-type oxysulphides (M  La, Ce, Pr, Nd, Sm) in small amounts as bead-shaped single crystals of high quality (M10S14O, tetragonal, (no. 142), Z = 8; M  La: a = 1536.51(4) pm, c = 2037.85(9) pm, R = Rw = 0.028; M  Ce: a = 1521.24(4) pm, c = 2018.43(9) pm, R = 0.014, Rw = 0.013; M  Pr: a = 1511.63(4) pm, c = 2006.27(9) pm, R = 0.028, Rw = 0.029; M  Nd: a = 1503.80(4) pm, c = 1996.46(8) pm, R = 0.015, Rw = 0.014; M  Sm: a = 1485.96(4) pm, c = 1974.04(8) pm, R = 0.016, Rw = 0.014). Their crystal structure is built up from isolated O2−-centred tetrahedra [OM4]10+ which are surrounded by a “sea” of lanthanide sulphide according to the formulation [OM4]S7M6S7. Three crystallographically independent M3+ cations occur with coordination numbers of eight (M1: seven plus one S2−; M2: six plus one S2− and one O2−, both bicapped trigonal prisms; M3: eight S2−, trigonal dodecahedron). Four different S2− (coordination numbers from four plus one to six) provide for the necessary coupling of the isolated [O(M2)4] tetrahedra to their metal sulphide vicinity.
    Journal of the Less Common Metals 10/1991;
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    ABSTRACT: The kinetics of hafnium hydride formation were studied utilizing conventional rate measurements (Sieverts system) combined with metallographic examinations of partially hydrided samples. The rate measurements were performed at 700 TorrH2 over a temperature range 200–550 °C. Two types of hafnium samples (polycrystalline and crystal bar) were compared. The progression of the massive stage of the reaction is characterized by a contracting-envelope morphology with a constant hydride front velocity. The anisotropy in the reaction front velocity regarding different crystalline orientations of the metal is small, resulting in similar results for the different types of hafnium. The temperature dependence of the front velocity obeys an Arrhenius-type relation over the temperature range 250–450 °C, with an apparent activation energy of 0.50 ± 0.05 eV. Considering a diffusion-controlled model, a diffusion activation barrier of about 0.4 eV is evaluated, which agrees with the average reported value for the diffusion of hydrogen in hafnium hydride. At temperatures above about 500 °C, deviations from the Arrhenius relation are displayed, possibly owing to a change of mechanism.
    Journal of the Less Common Metals 10/1991; 175(2):219–234.
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    ABSTRACT: Mixed oxides MTe2O6 (M  Ce, Th) were prepared at a temperature of 973 K. Structural characterization of these materials has been carried out by X-ray and electron diffraction. The structures have been refined by Rietveld analysis of X-ray powder diffraction data recorded at room temperature. The structures have monoclinic symmetry, space group P21/n, and the lattice parameters are , , and β = 108.007(8)° for CeTe2O6 and , , and β = 108.063(3)° for ThTe2O6.
    Journal of the Less Common Metals 10/1991; 175(2):235-241.
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    ABSTRACT: The IR absorption spectra of tetragonal copper manganite CuxMn3−x O4 spinels (O < x < 1) have singled out a discontinuity in cation distribution to occur at x > 0.60 in conformity with that recorded by our previous measurements and have warranted the existence of a more complex cation distribution than that proposed earlier. It has been concluded from this study that the ionic configuration for x <0.60, i.e. (Cux+Mn1−x2+)A (Mn2−x3+Mnx4+)BO42−, changes for x > 0.60 to (Cux−y+Mn1−x+y2+)A(Cuy2+Mn2−x−y3+Mnx4+)BO42−, where y represents a low value (less than 0.20).When the oxidation of Mn2+ and Cu+ ions is achieved below 450 °C, IR absorption measurements confirm the formation of a cation-deficient metastable spinel phase Cu1.5Mn1.5O4+δ with a 1:3 octahedral superstructure.
    Journal of the Less Common Metals 10/1991; 175(2):279–287.