Complex alloy structures regarded as sphere packings. I. Definitions and basic principles

Frank, F. C.; Kasper, J. S.

doi:10.1107/s0365110x58000487

Cited by 1,256 publications

(738 citation statements)

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“…• ␤-Ta -the tetragonal tantalum modification whose structure belongs to the Frank-Kasper structures of -type [10], which are typical for binary intermetallic compounds such as Fe-Cr. Tantalum of this modification could be apparently prepared only in the presence on an electric field: by direct current magnetron sputtering [11] or using the electrodeposition from molten salts [12,13].…”

Section: Phase Composition Of Electrolysis Productsmentioning

confidence: 99%

Electrode and chemical reactions during electrodeposition of tantalum products in CsCl melt

Grinevitch

Kuznetsov

Arakcheeva

et al. 2006

Electrochimica Acta

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This work was accomplished in the context of systematic examination of a role played by electrolyte cation composition in electroreduction processes. The electrochemical behaviour of molten salts systems where CsCl was used as solvent for potassium and caesium oxyfluorotantalates was investigated. In particular, the influence of the electrolysis parameters, such as concentration of tantalum species in electrolyte, temperature and current density on the cathodic products phase composition was determined by X-ray diffraction and scanning electron microscopy. Several phases generally crystallized at the cathode simultaneously. Among identified phases were metallic tantalum in cubic (␣) and tetragonal (␤) crystal modifications and TaO. But the most characteristic phases for the melt under study were two isostructural compounds with pyrochlor type crystal lattice CsTa 2+z 5 O 5+y F 1−y and CsTa 2+z 5−x O 5+y F 1−y . The former deposited in the form of transparent dielectric crystals and the later -in the form of metal-like conductive ones. This latter compound seems to be synthesized for the first time. The peculiarities of its structure were described. Electrochemical redox processes in melts containing potassium oxyfluorotantalates dissolved in CsCl were studied by cyclic voltammetry. Three discharge peaks were detected on voltammograms in the temperature range 700-850 • C. They were associated with the discharge of TaOF 6 3− and TaO 2 F 4 3− complexes and alkali metal cations.

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Section: Phase Composition Of Electrolysis Productsmentioning

confidence: 99%

Electrode and chemical reactions during electrodeposition of tantalum products in CsCl melt

Grinevitch

Kuznetsov

Arakcheeva

et al. 2006

Electrochimica Acta

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“…ISRO especially prevails in liquid Al alloys that form iQC phase, e.g., Al-Pd-Mn [46], Al-Mn-Cr [6], Al 60 Cu 34 Fe 6 [47], decagonal QC phase, e.g., Al 65 Cu 25 Co 10 [48] and Al 74 Co 26 [49] and complex polytetrahedral phase, e.g., Al 13 (Co,Fe) 4 [49], as directly evidenced by neutron scattering studies. In an alloy system such as Al-Cr, the existence in the equilibrium phase diagram of intermetallic phases with a complex crystalline structure containing several icosahedral building blocks in their large unit cell is already a strong indication that ISRO of atoms is present in the liquid [12]. As can be seen in Fig.…”

Section: Discussionmentioning

confidence: 57%

“…Long before the discovery of quasicrystals, it was already known that hundreds of intermetallic crystalline compounds have complex structures containing icosahedral building blocks in their unit cell, thus demonstrating already a strong tendency for icosahedral clustering in the undercooled liquid [12]. During cooling, these crystals with large unit cells, which are now called "approximants" [13], preserve icosahedral arrangement of atoms at a local scale while establishing (unlike QC) long-range translation periodicity.…”

Section: Introductionmentioning

confidence: 99%

Influence of icosahedral short range order on diffusion in liquids: A study on Al-Zn-Cr alloys

2016

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a b s t r a c tIt has been shown recently that minute additions of Cr in Al-Zn alloys refine the solidified grain structure and induce multiply-twinned grains which can only be explained if the icosahedral symmetry is considered (Kurtuldu et al., 2013). It has been suggested that Cr addition to Al-Zn alloys promotes the formation of icosahedral short-range order (ISRO) in the liquid, leading to the formation of icosahedral quasicrystals (iQC) acting then as a template for the nucleation of the fcc Al-phase. If ISRO exists in liquid Al-Zn-Cr alloys, this should influence diffusion of solute elements in the liquid. The present study focuses on the effect of Cr addition on Zn diffusion in liquid Al-Zn-Cr alloys. The solute diffusion coefficients of Zn and Cr in the liquid were deduced from the solute profiles in the quenched liquid ahead of a planar solidliquid interface. By comparison with the same measurement in Al-Zn alloys, it is shown that Cr indeed slows down the diffusion (and mobility) of Zn atoms, an effect which reinforces the hypothesis of ISRO in Al-Zn liquid induced by Cr.

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“…The original binary skutterudite formula can be written as T X 3 which, with the existence of voids in the original Im3 structure, may adopt a general formula R 2 M 8 X 24 or RM 4 X 12 . The cubic RT 2 Al 20 , known as the Frank Kasper compounds, provide another example of the caged-structure compounds similar to the filled-skutterudites, and have a large coordination number of atoms constructing the cage around the R atom [4]. They crystallize in the space group F d3m (#227) with the R ion surrounded by neighboring 16 atoms and the R site is of a cubic point symmetry.…”

Section: Introductionmentioning

confidence: 99%

Pr-magnetism in the quasi-skutterudite compound PrFe₂Al₈

Nair¹,

Ogunbunmi²,

Kumar³

et al. 2017

J. Phys.: Condens. Matter

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The intermetallic compound PrFe2Al8 that possesses a three-dimensional network structure of Al polyhedra centered at the transition metal element Fe and the rare earth Pr is investigated through neutron powder diffraction and inelastic neutron scattering in order to elucidate the magnetic ground state of Pr and Fe and the crystal field effects of Pr. Our neutron diffraction study confirms long-range magnetic order of Pr below TN = 4.5 K in this compound. Subsequent magnetic structure estimation reveals a magnetic propagation vector k = ( 1 2 0 1 2 ) with a magnetic moment value of 2.5 µB/Pr along the orthorhombic c-axis and evidence the lack of ordering in the Fe sublattice. The inelastic neutron scattering study reveals one crystalline electric field excitation near 19 meV at 5 K in PrFe2Al8. The energy-integrated intensity of the 19 meV excitation as a function of |Q|(Å −1 ) follows the square of the magnetic form factor of Pr 3+ thereby confirming that the inelastic excitation belongs to the Pr sublattice. The second sum rule applied to the dynamic structure factor indicates only 1.6(2) µB evolving at the 19 meV peak compared to the 3.58 µB for free Pr 3+ , indicating that the crystal field ground state is magnetic and the missing moment is associated with the resolution limited quasi-elastic line. The magnetic order occurring in Pr in PrFe2Al8 is counter-intuitive to the symmetry-allowed crystal field level scheme, hence, is suggestive of exchange-mediated mechanisms of ordering stemming from the magnetic ground state of the crystal field levels.

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Complex alloy structures regarded as sphere packings. I. Definitions and basic principles

Cited by 1,256 publications

References 0 publications

Electrode and chemical reactions during electrodeposition of tantalum products in CsCl melt

Electrode and chemical reactions during electrodeposition of tantalum products in CsCl melt

Influence of icosahedral short range order on diffusion in liquids: A study on Al-Zn-Cr alloys

Pr-magnetism in the quasi-skutterudite compound PrFe₂Al₈

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Complex alloy structures regarded as sphere packings. I. Definitions and basic principles

Cited by 1,256 publications

References 0 publications

Electrode and chemical reactions during electrodeposition of tantalum products in CsCl melt

Electrode and chemical reactions during electrodeposition of tantalum products in CsCl melt

Influence of icosahedral short range order on diffusion in liquids: A study on Al-Zn-Cr alloys

Pr-magnetism in the quasi-skutterudite compound PrFe2Al8

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Pr-magnetism in the quasi-skutterudite compound PrFe₂Al₈