Synthesis, Structure and Magnetic Properties of NiFe3O5

A new CaFe3O5-type phase NiFe3O5 (orthorhombic Cmcm symmetry, cell parameters a = 2.89126(7), b = 9.71988(21) and c = 12.52694(27) Å) has been synthesised under pressures of 12-13 GPa at 1200 °C. NiFe3O5 has an inverse cation site distribution and reveals an interesting evolution from M2+(Fe3+ )2Fe2+O5 to Fe2+(M2+ 0.5Fe3+ 0.5)2Fe3+O5 distributions over three distinct cation sites as M2+ cation size decreases from Ca to Ni. Magnetic susceptibility measurements show successive transitions at 275, ~150, and ~20 K and neutron diffraction data reveal a series of at least three spin-ordered phases with evolving propagation vectors k = [0 0 0] [0 ky 0]  [½ ½ 0] on cooling. The rich variety of magnetically ordered phases in NiFe3O5 likely results from frustration of Goodenough-Kanamori exchange interactions between the three spin sublattices, and further interesting magnetic materials are expected to be accessible within the CaFe3O5-type family.

Synthesis and structure determination of racemic (Δ/Λ)-tris(ethylenediamine)cobalt(III) trichloride hemi(hexaaquasodium chloride)

The synthesis and crystal structure of the title racemic compound, [Co(C2H8N2)3]Cl3.{[Na(H2O)6]Cl}0.5, are reported. The trivalent cobalt atom, which resides on a crystallographic threefold axis, is chelated by a single ethylene diamine (en) ligand and yields the tris-chelate [Co(en)3]3+ cation with distorted octahedral geometry after the application of crystal symmetry. The sodium cation (site symmetry \overline{3}), has a single water molecule bound to it in the asymmetric unit and yields a distorted, octahedrally coordinated hydrated [Na(H2O)6]+ cation after the application of symmetry. One of the chloride ions lies on a general position and the other has \overline{3} site symmetry. An extensive array of C—H...O, N—H...Cl and O—H...Cl hydrogen bonds exists between the ethylene diamine ligands, the water molecules of hydration, and the anions present, thereby furnishing solid-state stability.

Ferro-fluoro-edenite, a new amphibole endmember from Vulcano Island (Sicily, Italy)

ABSTRACT Ferro-fluoro-edenite, ideally NaCa2Fe2+5(Si7Al)O22F2, was found as prismatic crystals up to 1.00 mm inside cavities in ejecta of the 1873 eruption at La Fossa crater, Vulcano Island, Aeolian Archipelago, Sicily, Italy. It is associated with quartz, magnetite, and vonsenite. Crystals are dark brown to black, transparent or semitransparent with vitreous luster, and non fluorescent. The Mohs hardness is 5–6. Cleavage is fair on {110} and fracture is uneven. Density (calc.) is 3.358 g cm–3 using the empirical formula and single-crystal cell data. The mineral is biaxial negative, α = 1.629(2), β = 1.659(2), γ = 1.667(2), 2V (calc.) = –53.8°, Y = b. Dispersion is weak to very weak, r < v, pleochroism not visible. Ferro-fluoro-edenite is monoclinic, space group C2/m, a = 9.9132(10), b = 18.1736(19), c = 5.2943(6) Å, β = 104.85(1)°, V = 922.0(2) Å3, Z = 2. The strongest X-ray diffraction peaks in the powder pattern are [d(I, hkl)]: 8.54(100, 1 1 0), 4.506(16, 0 4 0), 3.154(52, 3 1 0), 2.833(43, 3 3 0), 2.057(14, 2 0 2), 1.910(12, 5 1 0), 1.662(15, 4 6 1). The FTIR spectrum shows a broad band at about 950 cm–1 and no bands in the OH stretching region. The structure refinement led to a final R = 0.0210 for 1444 observed reflections with I > 2σ(I) and allowed cation site assignment and ordering. Microprobe analysis gave the following empirical formula calculated on the basis of 24 (O + F + Cl) apfu: (Na0.69K0.23□0.08)(Ca1.69Mg0.16Mn0.10Na0.05)Σ2(Fe2+2.86Mg2.04Ti0.10)Σ5(Si6.93Al1.05Ti0.02)Σ8O22(F1.89Cl0.09OH0.02)Σ2.

High Temperature Electrical Properties of Co-Substituted La4BaCu5O13+δ Thin Films Fabricated by Sputtering Method

The high-temperature conductivity of the perovskite oxides of a La4BaCu5O13+δ (LBCO) thin film prepared by RF sputtering deposition and thermal annealing has been studied. While the bulk LBCO compound was metallic, the LBCO film deposited on a Si substrate by sputtering and a post annealing process showed semiconductor-like conduction, which is considered to be due to the defects and poor grain connectivity in the LBCO film on the Si substrate. The LBCO film deposited on a SrTiO3 substrate was of high film quality and showed metallic conduction. When the cation site Cu was substituted by Co, the electrical conductivity of the LBCO film increased further and its temperature dependence became smaller. The transport properties of LBCO films are investigated to understand its carrier generation mechanism.

Exploring Aliovalent Substitutions in the Lithium Halide Superionic Conductor Li3-xIn1-xZrxCl6 (0 ≤ X ≤ 0.5)

<p>In recent years, ternary halides Li₃<i>MX</i>₆ (<i>M</i> = Y, Er, In; <i>X</i> = Cl, Br, I) have garnered attention as solid electrolytes due to their wide electrochemical stability window and favorable room-temperature conductivities. In this material class, the influences of iso- or aliovalent substitutions are so far rarely studied in-depth, despite this being a common tool for correlating structure and transport properties. In this work, we investigate the impact of Zr substitution on the structure and ionic conductivity of Li₃InCl₆ (Li_3-<i>x</i>In_1-<i>x</i>Zr<i>_x</i>Cl₆ with 0 ≤ <i>x</i> ≤ 0.5) using a combination of neutron diffraction, nuclear magnetic resonance and impedance spectroscopy. Analysis of high-resolution diffraction data shows the presence of an additional tetrahedrally coordinated lithium position together with cation site-disorder, both of which have not been reported previously for Li₃InCl₆. This Li⁺ position and cation disorder lead to the formation of a three-dimensional lithium ion diffusion channel, instead of the expected two-dimensional diffusion. Upon Zr⁴⁺ substitution, the structure exhibits non-uniform volume changes along with an increasing number of vacancies, all of which lead to an increasing ionic conductivity in this series of solid solutions.</p>

Exploring Aliovalent Substitutions in the Lithium Halide Superionic Conductor Li3-xIn1-xZrxCl6 (0 ≤ X ≤ 0.5)

<p>In recent years, ternary halides Li₃<i>MX</i>₆ (<i>M</i> = Y, Er, In; <i>X</i> = Cl, Br, I) have garnered attention as solid electrolytes due to their wide electrochemical stability window and favorable room-temperature conductivities. In this material class, the influences of iso- or aliovalent substitutions are so far rarely studied in-depth, despite this being a common tool for correlating structure and transport properties. In this work, we investigate the impact of Zr substitution on the structure and ionic conductivity of Li₃InCl₆ (Li_3-<i>x</i>In_1-<i>x</i>Zr<i>_x</i>Cl₆ with 0 ≤ <i>x</i> ≤ 0.5) using a combination of neutron diffraction, nuclear magnetic resonance and impedance spectroscopy. Analysis of high-resolution diffraction data shows the presence of an additional tetrahedrally coordinated lithium position together with cation site-disorder, both of which have not been reported previously for Li₃InCl₆. This Li⁺ position and cation disorder lead to the formation of a three-dimensional lithium ion diffusion channel, instead of the expected two-dimensional diffusion. Upon Zr⁴⁺ substitution, the structure exhibits non-uniform volume changes along with an increasing number of vacancies, all of which lead to an increasing ionic conductivity in this series of solid solutions.</p>

Crystal structure of levocetirizine dihydrochloride Form I, C21H27ClN2O3Cl2

The crystal structure of levocetirizine dihydrochloride Form I has been solved and refined using synchrotron X-ray powder diffraction data and optimized using density functional techniques. Levocetirizine dihydrochloride Form I apparently crystallizes in space group P21/n (#14) with a = 24.1318(21), b = 7.07606(9), c = 13.5205(7) Å, β = 97.9803(4)°, V = 2286.38(12) Å3, and Z = 4. The crystal structure consists of interleaved double columns of cations and anions along the short b-axis. The hydrogen bonds link the cations and anions along this axis. Each protonated nitrogen atom forms a strong N–H⋯Cl hydrogen bond to one of the chloride anions. The carboxylic acid group also forms an H-bond to Cl56, resulting in a ring with a graph set R1,2(10). The centrosymmetric P21/n model for the crystal structure of levocetirizine dihydrochloride is better than the non-centrosymmetric P21 model, even though levocetirizine is a chiral molecule; the sample exhibits weak second-harmonic generation, and three weak peaks which violate the glide plane are observed. The centrosymmetric model is better by statistical, graphical, and energetic measures, as well as by chemical reasonableness. To accommodate the chiral molecule in a centrosymmetric space group, the chiral central carbon atom was disordered over two half-occupied positions, so that each cation site could be occupied by a cation of the correct chirality. A powder pattern from a Le Bail extraction of this synchrotron data set is included in the Powder Diffraction File™ as entry 00-066-1627.

Occurrence and characterization of tremolite asbestos from the Mid Atlantic Ridge

Tremolite is one of the most common amphibole species and, in the fibrous form (i.e., characterized by crystals/particles consisting of fibres with length > 5 µm, width < 3 µm and aspect ratio > 3), one of the six asbestos minerals. Until now the attention of crystallographers has focused only on samples from continental environment. Here we report the first chemical and structural data of a tremolite asbestos found along the Mid Atlantic Ridge (MAR) at the eastern intersection of the Romanche Transform Fault (Equatorial MAR). Tremolite is associated with chlorite and lizardite and was formed through the green shale facies lower than zeolite in a predominantly fluid system. MAR tremolite asbestos shows very slight deviations from the ideal crystal structure of tremolite. Differences in cation site partitioning were found with respect to tremolite asbestos from ophiolitic complexes, attributed to the different chemical–physical conditions during the mineral formation. In particular, oceanic tremolite asbestos is enriched in Al and Na, forming a trend clearly distinct from the continental tremolites.