Superconductors Chevrel phases

The situation is very similar in the Chevrel phases. These are ternary molybdenum chalcogenides A,.[Mo6Xg] (A = metal, X = S, Se) that have attracted much attention because of their physical properties, especially as superconductors. The parent compound is PbMo6Sg it contains Mo6Sg clusters that are linked with each other in such a way that the free coordination sites of one cluster are occupied by sulfur atoms of adjacent clusters (Fig. 13.9). The electric properties of Chevrel phases depend on the number of valence electrons. With 24 electrons per cluster (one electron pair for each edge of the... 

X-ray crystallography, 40 20-21 synthetic models, 40 23-48 xanthane oxidase, 40 21-23 chalcogenide halides, 23 370-377, 413 Chevrel phases, 23 376-377 metal-metal bonding, 23 330, 373 structural data, 23 373-376 as superconductors, 23 376 synthesis, 23 371-372 chloride, 46 4-24, 35-44 heterocations of, 9 290, 291 cluster compounds, 44 45-46 octahedral, 44 47-49, 53-63 electronic structure, 44 55-63 molecular structure, 44 53-54 synthesis, 44 47-49 rhomboidal, 44 75-82 solid-state clusters and, 44 66-72, 74-75, 80-82, 85-87 tetrahedral, 44 72-75 triangular, 44 82-87 cofactor, 40 2, 4-12 anaerobic isolation, 40 5 molybdopterin and, 40 4-8 reduced form, 40 12 synthesis, 40 8-12 xanthine oxidase, 45 60-63 complexes... 

In passing, it should be noted that Michel and Raveau had carried out electrical measurements on several alkaline-earth substituted La2Cu04 compounds and presented (140) their experimental results in a comprehensive review during 1984. Their work, however, was primarily structural with a focus on electrical and magnetic properties above 50 K for this reason they missed observing the superconducting transition at 30 K. It is this author s belief that these Cu-O phases should be called the "Raveau-Michel" phases in much the same way as the molybdenum sulfide superconductors are called the "Chevrel" phases. 

M MogSeg and related Chevrel phases High field superconductors ... 

H.-L.Luo Thin-Film Ternary Superconductors. - H.Nohl, W.Klose, O.K Andersen Band Structures of MxMogXg- and M2Mo6X6-Cluster Compounds. - S.D. Bader, S.K.Sinha, B.P.Schweiss, B.Renker Phonons in Ternary Molybdenum Chalcogenide Superconductors. -F.Pobell, D. Rainer, H. Wiihl Electron-Phonon Interaction in Chevrel-Phase Compounds. - Subject Index. 

Shortly after acceptance of my manuscripts on the Chevrel phases (15) and the lanthanide rhodium borides (16) the initial scientific reports on the high copper oxide superconductors... 

A class of metal cluster superconductors of particular Interest consists of ternary molybdenum chalcogenides, conmonly known as the Chevrel phases (13). These phases were the first type of superconducting ternary system found to have relatively high critical temperatures and exhibited the highest known critical magnetic fields (Hc2 before discovery of the copper oxide... 

There are a number of materials which have been studied but the two favorite ternary superconductors are the so called Chevrel phases, named after R. Chevrel (Universite de Rennes, France) who first prepared the MMo Sg or MMo Seg compounds (Chevrel et al. 1971), and the RRh4B4 compounds. In the Chevrel phases, M can be any number of metals including the rare earth metals, and in the latter compound R represents the rare earths and thorium. In both instances Matthias and his co-workers were the first to report the existence of superconductivity in the Chevrel phases (Matthias et al. 1972) and in RRh4B4 (Matthias et al. 1977),... 

In the Chevrel phases only HoMo Sg is a re-entrant type superconductor, while the RMOgSg phases, with R = Gd, Tb, Dy and Er, and the RMo Scg phases, with R = Gd, Tb and Er, are co-existing type materials. The rest of the RMo Sg and RMogScg phases are normal superconductors, except for the europium compounds, which are neither superconductors nor magnetic, and CeMo Sg and CeMogScg which are an antiferromagnet and a ferromagnet, respectively. 

The magnetic ordering of the lanthanide ions in superconducting systems has been a topic of active interest for many years. In conventional magnetic superconductors such as the Chevrel phase and related materials the lanthanide moments are coupled very weakly both to the metallic electrons and to each other, resulting in very low... 

Other ternary molybdenum sulfides known as Chevrel phases are recognized as high field superconductors (59), but recently these compounds were found to be active as hydrotreating catalysts. Ooi and co-workers (60) reported that supported cobalt Chevrel phase sulfide catalysts present higher HDS activity than commercial C0M0S/AI2O3 catalysts. 

H. (1991) Basic similarities among cuprate, bismuthate, organic, Chevrel-phase, and heavy-fermion superconductors shown by penetration-depth measurements. Phys. Rev. Lett., 66 (20), 2665-2668. 

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