| 1. |
- Besnard, Céline, et al.
(författare)
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Re4As6S3, a thio-spinel-related cluster system.
- 2003
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Ingår i: Journal of Solid State Chemistry. - Elsevier. - 0022-4596. ; 172:2, s. 446-450
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Tidskriftsartikel (refereegranskat)abstract
- We have synthesized a new compound with formula Re4As6S3 and characterized its crystal structure by Rietveld powder diffraction methods. Re4As6S3 crystallizes in an face-centered cubic unit cell, space group F (4) over bar 3m (no. 216), with lattice constant a = 9.8608(1) Angstrom and Z = 4. The rhenium atoms form tetrahedral clusters linked via tetrahedral arsenic clusters to produce an NaCl-type arrangement. The oxidation state of rhenium is IV and the number of electrons shared by the rhenium atoms in the cluster is 12. The structure is based on an ordered defect thio-spinel A((1-x))B(2)X(4) where the B-type atoms form tetrahedral clusters. (C) 2003 Elsevier Science (USA). All rights reserved.
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| 2. |
- Liu, H.K., et al.
(författare)
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Cu valence states in superconducting BiPbSrCaCuO system
- 1990
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Ingår i: Journal of Solid State Chemistry. - Academic Press. - 0022-4596. ; 87:2
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Tidskriftsartikel (övrigt vetenskapligt)abstract
- The oxidation states of Bi, Pb, and Cu in the BiPbSrCaCuO (BPSCCO) system have been determined by a combination of volumetric measurement technique and iodometric titration. It was found that, in contrast to previous reports, the concentration of the Cu3+ ions decreased with increasing Pb content, and Cu3+ ions were absent in samples of Bi1.6Pb0.4Sr1.6Ca2Cu3O9.8, while a Tc at 108 K and a Jc of greater than 12,000 A/cm2 at 77 K were observed. The 110 K phase in BPSCCO was stabilized and showed a high tolerance to change in oxygen partial pressure during sintering. In Pb-doped materials, Bi appears to be trivalent while Pb was determined to be mixed-valence Pb4+ Pb2+. It is suggested that superconductivity in BPSCCO may result from a dynamic transfer of holes from Bi PbO layers toward CuO2 planes
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| 3. |
- Alkebro, Jesper, et al.
(författare)
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Modeling high-energy ball milling in the alumina-yttria system
- 2002
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Ingår i: Journal of Solid State Chemistry. - Academic Press. - 0022-4596. ; 164:1
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Tidskriftsartikel (övrigt vetenskapligt)abstract
- Experimental results from high-energy ball milling of alumina-yttria powder mixtures have been analyzed with models collected from the literature. Depending on the milling conditions, either there is formation of an intermediate phase in the alumina-yttria system (yttrium aluminum perovskite, YAP), or the sample becomes mostly amorphous. Variations due to milling tool material can be accounted for by local models based on the Hertzian theory of elastic bodies, but the effects of changing mills are poorly accounted for by published models. Therefore, the concept of an impact frequency distribution over the energy spectrum is introduced as a tool for studying the characteristics of the mills. The pressure on the powder trapped between two colliding bodies has been found to be the factor deciding the outcome of the process. The threshold behavior of the system yields an amorphous structure for low pressures, and formation of YAP when impact pressures exceed the threshold value.
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| 4. |
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| 5. |
- Baranov, A. I., et al.
(författare)
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2D metal slabs in new nickel-tin chalcogenides Ni(7-delta)SnQ(2) (Q=Se, Te) : average crystal and electronic structures, chemical bonding and physical properties
- 2004
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Ingår i: Journal of Solid State Chemistry. - 0022-4596. ; 177:10, s. 3616-3625
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Tidskriftsartikel (refereegranskat)abstract
- A systematic search for mixed low-valence, nickel-tin chalcogenides performed by establishing phase relations in the parts of Ni-Sn-Se and Ni-Sn-Te ternary systems resulted in the discovery of two new compounds, Ni5.62SnSe2 and Ni5.78SnTe2 Single crystals of both compounds were prepared by chemical transport with iodine and crystal structures were determined by single crystal X-ray investigation. The ED patterns for Ni5.78SnTe2 showed the presence of satellite reflections, which indicate a modulated structure with qapproximate to0.4a*. Average crystal structures of both compounds were determined to be of tetragonal symmetry (Sp.gr.I4/mmm, Z = 2) with a = 3.6890(8) Angstrom, c = 18.648(3) Angstrom, R-w = 0.0716 and a = 3.7680(5) Angstrom, c = 19.419(4) Angstrom, R-w, 0.0832, correspondingly, and are isostructural to known Ni5.72SbSe2 and Ni5.66SbTe2. Measurements were carried out for both compounds with respect to thermal, electrical and magnetic properties. Ab initio band structure calculations were also performed to take a first glance into the electronic structure of such type compounds. The anisotropy of their band structure was found. Physical property measurements showed both compounds to be the anisotropic metallic conductors and paramagnetics. Calculated difference charge density maps revealed pairwise covalent and multicenter metallic nature of the d-metal-chalcogen and d-metal-p-metal interactions, respectively.
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| 6. |
- Becker, Richard, et al.
(författare)
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Crystal structure and magnetic properties of two new cobalt selenite halides : Co5(SeO3)4X2 (X=Cl, Br)
- 2007
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Ingår i: Journal of Solid State Chemistry. - 0022-4596. ; 180:3, s. 1051-1059
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Tidskriftsartikel (refereegranskat)abstract
- Two new isostructural cobalt selenite halides Co5(SeO3)4Cl2 and Co5(SeO3)4Br2 have been synthesized. They crystallize in the triclinic system space group P−1 with the following lattice parameters for Co5(SeO3)4Cl2: a=6.4935(8) Å, b=7.7288(8) Å, c=7.7443(10) Å, α=66.051(11)°, β=73.610(11)°, γ=81.268(9)°, and Z=1. The crystal structures were solved from single-crystal X-ray data, R1=3.73 and 4.03 for Co5(SeO3)4Cl2 and Co5(SeO3)4Br2, respectively. The new compounds are isostructural to Ni5(SeO3)4Br2.Magnetic susceptibility measurements on oriented single-crystalline samples show anisotropic response in a broad temperature range. The anisotropic susceptibility is quantitatively interpreted within the zero-field splitting schemes for Co2+ and Ni2+ ions. Sharp low-temperature susceptibility features, at TN=18 and 20 K for Co5(SeO3)4Cl2 and Co5(SeO3)4Br2, respectively, are ascribed to antiferromagnetic ordering in a minority magnetic subsystem. In isostructural Ni5(SeO3)4Br2 magnetically ordered subsystem represents a majority fraction (TN=46 K). Nevertheless, anisotropic susceptibility of Ni5(SeO3)4Br2 is dominated at low temperatures by a minority fraction, subject to single-ion anisotropy effects and increasing population of Sz=0 (singlet) ground state of octahedrally coordinated Ni2+.
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| 7. |
- Becker, Richard, et al.
(författare)
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Three new tellurite halides with unusual Te4+ coordinations and iron honeycomb lattice variants
- 2007
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Ingår i: Journal of Solid State Chemistry. - 0022-4596. ; 180:5, s. 1750-1758
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Tidskriftsartikel (refereegranskat)abstract
- The crystal structure of three new iron and copper-iron tellurite halides are presented; (I) Cu3Fe8Te12O32Cl10 that crystallizes in the orthorhombic space group Pmmn, (II) Fe8Te12O32Cl3Br3 that crystallizes in the monoclinic space group P21/c, and (III) Fe5(TeO3)6Cl2 that crystallizes in the triclinic space group P-1. The crystal structures were solved from single crystal X-ray diffraction data. All three compounds have layered crystal structures where the Fe atoms form variants of the honeycomb lattice. Highly unusual Te4+ coordination polyhedra are exemplified: [TeO3+1E], [TeO3XE], [TeO3+1XE], and [TeO3X2E] (X=halide ion, E=the lone–pair valence electrons). The crystal structures contain large non-bonding volumes occupied by the stereochemically active lone–pair electrons on Te4+.
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| 8. |
- Berastegui, P., et al.
(författare)
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A high temperature superionic phase of CsSn2F5
- 2010
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Ingår i: Journal of Solid State Chemistry. - 0022-4596. ; 183:2, s. 373-378
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Tidskriftsartikel (refereegranskat)abstract
- The compound CsSn2F5 has been investigated over the temperature range from ambient to 545 K using differential scanning calorimetry, impedance spectroscopy and neutron powder diffraction methods. A first-order phase transition is observed from DSC measurements at 510(2) K, to a phase possessing a high ionic conductivity (σ<img src="http://www.sciencedirect.com/scidirimg/entities/223c.gif" />2.5×10−2 Ω−1 cm−1 at 520 K). The crystal structure of the high temperature superionic phase (labelled α) has been determined to be tetragonal (space group I4/mmm, a=4.2606(10) Å, c=19.739(5) Å and Z=2) in which the cations form layers perpendicular to the [001] direction, with a stacking sequence CsSnSnCsSnSn… All the anions are located in two partially occupied sites in the gap between the Cs and Sn layers, whilst the space between the Sn cations is empty, due to the orientation of the lone-pair electrons associated with the Sn2+. The structure of α-CsSn2F5 is discussed in relation to two other layered F− conducting superionic phases containing Sn2+ cations, α-RbSn2F5 and α-PbSnF4 and, to facilitate this comparison, an improved structural characterisation of the former is also presented. The wider issue of the role of lone-pair cations such as Sn2+ in promoting dynamic disorder within an anion substructure is also briefly addressed.
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| 9. |
- Biendicho, Jordi Jacas, et al.
(författare)
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Synthesis and characterisation of perovskite SrxY1-xFeO3-d (=.63≤x<1) and Sr0.75Y0.25Fe1-yMyO3-d (M=Cr, Mn, Ni) (y= 0.2, 0.33, 0.5)
- 2013
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Ingår i: Journal of Solid State Chemistry. - 0022-4596. ; 200, s. 30-38
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Tidskriftsartikel (refereegranskat)abstract
- Oxygen-deficient ferrates with the cubic perovskite structure SrxY1-xFeO3-d were prepared in air (0.71 ≤ x ≤ 0.91) as well as in N2 (x=0.75 and 0.79) at 1573K. The oxygen content of the compounds prepared in air increases with increasing strontium content from 3-δ=2.79(2) for x=0.75 to 3-δ=2.83(2) for x=0.91. Refinement of the crystal structure of Sr0.75Y0.25FeO2.79 using TOF neutron powder diffraction (NPD) data shows high anisotropic atomic displacement parameter (ADP) for the oxygen atom resulting from a substantial cation and anion disorder. Electron diffraction (ED) and high-resolution electron microscopy (HREM) studies of Sr0.75Y0.25FeO2.79 reveal a modulation along <100>p with G± ~0.4<100>p indicating a local ordering of oxygen vacancies. Magnetic susceptibility measurements at 5-390K show spin-glass behaviour with dominating antiferromagnetic coupling between the magnetic moments of Fe cations. Among the studied compositions, Sr0.75Y0.25FeO2.79 shows the lowest thermal expansion coefficient (TEC) of 10.5 ppm K-1 in air at 298-673K. At 773-1173K TEC increases up to 17.2 ppm K-1 due to substantial reduction of oxygen content. The latter also results in a dramatic decrease of the electrical conductivity in air above 673K. Partial substitution of Fe by Cr, Mn and Ni according to the formula Sr0.75Y0.25Fe1-yMyO3-δ (y=0.2, 0.33, 0.5) leads to cubic perovskites for all substituents with y=0.2. Their TECs are higher in comparison with un-doped Sr0.75Y0.25FeO2.79. Only M=Ni has increased electrical conductivity compared to un-doped Sr0.75Y0.25FeO2.79.
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| 10. |
- Borg, S, et al.
(författare)
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Structure study of Bi2.5Na0.5Ta2O9 and B2.5Nam-1.5NbmO3m+3 (m=2-4) by neutron powder diffraction and electron microscopy
- 2002
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Ingår i: Journal of Solid State Chemistry. - Academic Press. - 0022-4596. ; 167:1, s. 86-96
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Tidskriftsartikel (refereegranskat)abstract
- The crystal structures of Bi2.5Na0.5Ta2O9 and Bi2.5Nam-1.5NbmO3m+3 (m = 3,4) have been investigated.ysis of their neutron powder diffraction by the Rietveld anal patterns (lambda = 1.470 Angstrom). These compounds belong to the Aurivillius phase family and are built up by (Bi2O2)(2+) fluorite layers and (A(m-1)BnO(3m+1))(2-) (m = 2-4) pseudo-perovskite slabs. Bi2.5Na0.5Ta2O9 (m = 2) and Bi2.5Na2.5Nb4O15 (m = 4) crystallize in the orthorhombic space group A2(1)am, Z = 4, with lattice constants of a = 5.4763(4), b = 5.4478(4), c 24.9710 (15) and a = 5.5095(5), b = 5.4783(5), c = 40.553(3) Angstrom, respectively. Bi2.5Na1.5Nb3O12 (m = 3) has been refined in the orthorhombic space group B2cb, Z = 4, with the unit-cell parameters a = 5.5024(7), b = 5.4622(7), and c = 32.735(4) Angstrom. In comparison with its isostructural Nb analogue, the structure of Bi2.5Na0.5Ta2O9 is less distorted and bond valence sum calculations indicate that the Ta-O bonds are somewhat stronger than the Nb-O bonds. The cell parameters a and h increase with increasing m for the compounds Bi2.5Nam-1.5NbmO3m+3 (m = 2-4), causing a greater strain in the structure. Electron microscopy studies verify that the intergrowth of mixed perovskite layers, caused by stacking faults, also increases with increasing m. (C) 2002 Elsevier Science (USA).
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