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Structure of β-SrRh<sub>2</sub>O<sub>4</sub> from X-ray and neutron powder diffraction
No full textβ-SrRh2O4, a novel high temperature phase, is prepared as black powder by solid state reaction of SrCO3 with Rh in air. The compound crystallises in the space group P63c, Z = 1, with a = 3.0626(2) Å and c = 11.3996(7) Å. The structure consists of CdI2-type layers of edge sharing RhO6 octahedra with an AABB oxygen layer sequence. Strontium is found in partial occupation of both available interlayer sites, in trigonal prismatic coordination.</p
High-throughput methods to optically functional oxide and oxide-nitride materials
No full textHigh-throughput methods have been used for the synthesis and preliminary characterisation of optically functional ceramic oxide and oxide-nitride materials on an alumina substrate. Gel routes have been investigated for their viability when used with a Teflon masking system. Three different systems and deposition methodologies have been studied. The first system uses a polymer complex method based on citric acid and ethylene glycol in aqueous media to create arrays of the formula Ca1-xSrxZr1-yCryO3 (0≤x≤1, in 0.2 steps; 0≤y≤0.24, in 0.03 steps) annealed at temperatures of 600, 800, 1000 and 1200 degrees C. A metal alkoxide sol-gel method using an acetic acid-acetic anhydride solvent has been employed to produce arrays of oxides and oxide nitrides with the general formulae SrZr1-xTaxO3 and SrZr1-xTaxO2+xN1-x (0≤x≤1, in 0.2 steps). Arrays of aluminium-doped zinc oxides, as potential transparent conducting oxides, have been produced through hydrolysis of a zinc acetate-ethylene glycol precursor using aluminium nitrate solutions while tin-doped indium oxides were obtained by direct evaporation and calcination of indium and tin solutions. Conversion of these oxide arrays to oxide-nitride arrays was carried out by reaction of the deposited SrZr1-xTaxO3 materials under high purity flowing ammonia. Initial characterisation of arrays has been undertaken using powder X-ray diffraction, scanning electron microscopy and UV-vis spectroscopy
The introduction of palladium into superconducting cuprate materials
No full textA series of doped parent compounds of the form Sr2CuχM1-χO3 (M=Pd, Ni) have been prepared, and successfully fluorinated, forming Sr2CuχM1-χO2F 2+δ. Rietveld refinement of powder x-ray diffraction data indicates expanding cell parameters with dopant level, as expected with the introduction of a larger cation. Investigation into the YBa2Cu4O8 system has shown very little palladium doping can be achieved.</p
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
[{Cp2(tBuSe)Nb}2E] (E= O and Se) with bridging oxide or selenide ligands
No full textThe title compounds, -oxido-bis[(tert-butylselenolato)bis(5-cyclopentadienyl)niobium(IV)] toluene solvate, [Nb2(C5H5)4(C4H9Se)2O]·C7H8, and -selenido-bis[(tert-butylselenolato)bis(5-cyclopentadienyl)niobium(IV)], [Nb2(C5H5)4(C4H9Se)2Se], consist of niobium(IV) centres each bonded to two 5-coordinated cyclopentadienyl groups and one tert-butylselenolate ligand and are the first organometallic niobium selenolates to be structurally characterized. A bridging oxide or selenide completes the niobium coordination spheres of the discrete dinuclear molecules. In the oxide, the O atom lies on an inversion centre, resulting in a linear Nb-O-Nb linkage, whereas the selenide has a bent bridging group [Nb-Se-Nb = 139.76 (2)°]. The difference is attributable to strong bonding in the oxide case, although the effects on the Nb-C and Nb-SetBu bond lengths are small
mu-1,2-Bis(diphenylphosphino)ethane-kappa P-2 : P-bis[trichloridogallium(III)]
No full textThe centrosymmetric molecule of the title compound, [(GaCl3)2(C26H24P2)] or [(GaCl3)2{[mu]-Ph2P(CH2)2PPh2}], consists of two pseudo-tetrahedral Ga centres coordinated by three Cl atoms [Ga-Cl = 2.1608 (8)-2.1648 (8) Å] and bridged by the diphosphane ligand [Ga-P = 2.3854 (8) Å]
Preparation, characterization, and structural systematics of diphosphane and diarsane complexes of gallium(III) halides
No full textThe diphosphane o-C6H4(PMe2)2 reacts with GaX3 (X = Cl, Br, or I) in a 1:1 molar ratio in dry toluene to give trans-[GaX2{o-C6H4(PMe2)2}2][GaX4], the cations of which contain the first examples of six-coordinate gallium in a phosphane complex. The use of a 1:2 ligand/GaCl3 ratio produced [GaCl2{o-C6H4(PMe2)2}][GaCl4], containing a pseudotetrahedral cation, and similar pseudotetrahedral [GaX2{o-C6H4(PPh2)2}][GaX4] complexes are the only products isolated with the bulkier o-C6H4(PPh2)2. On the other hand, Et2P(CH2)2PEt2, which has a flexible aliphatic backbone, formed [(X3Ga)2{-Et2P(CH2)2PEt2}], in which the ligand bridges two pseudotetrahedral gallium centers. The diarsane, o-C6H4(AsMe2)2, formed [GaX2{o-C6H4(AsMe2)2}][GaX4], also containing pseudotetrahedral cations, and in marked contrast to the diphosphane analogue, no six-coordinate complexes form; a very rare example where these two much studied ligands behave differently towards a common metal acceptor. The complexes [(I3Ga)2{-Ph2As(CH2)2AsPh2}] and [GaX3(AsMe3)] are also described. The X-ray structures of trans-[GaX2{o-C6H4(PMe2)2}2][GaX4] (X = Cl, Br or I), [GaCl2{o-C6H4(PPh2)2}][GaCl4], [GaX2{o-C6H4(AsMe2)2}][GaX4] (X = Cl or I), [(I3Ga)2{-Ph2As(CH2)2AsPh2}], and [GaX3(AsMe3)] (X = Cl, Br or I) are reported, and the structural trends are discussed. The solution behavior of the complexes has been explored using a combination of 31P{1H} and 71Ga NMR spectroscopy
Synthesis, spectroscopic and structural systematics of complexes of germanium(IV) halides (GeX4, X = F, Cl, Br or I) with phosphane oxides and related oxygen donor ligands
No full textThe first series of phosphane oxide complexes of germanium(IV) halides have been prepared, including trans-[GeF4(R3PO)2] (R = Me, Et or Ph), trans-[GeCl4(Et3PO)2], fac-[GeCl3(Me3PO)3]2[GeCl6] and cis-[GeX2(Me3PO)4]X2 (X = Cl or Br) and characterised by IR and multinuclear NMR (1H, 19F{1H} and 31P{1H}) spectroscopy. Crystal structures of all the above (except trans-[GeCl4(Et3PO)2]) are described. Remarkably, under mild conditions Me3PO displaces halide ligands from GeX4 (X = Cl, Br) to form the cationic species above. Ph3AsO forms trans-[GeF4(Ph3AsO)2], but reaction of Ph3AsO or Me3AsO with GeCl4 leads to the corresponding R3AsCl2. The complexes [GeF4(MeCN)2], [GeF4(thf)2] and [GeF4(MeOCH2CH2OMe)] are also described and the relative Lewis acidities of GeX4 established
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