O4 Layers Research Articles

Design and Construction of Carbon-Coated Fe3 O4 /Cr2 O3 Heterostructures Nanoparticles as High-Performance Anodes for Lithium Storage.

Transition metal oxides, highly motivated anodes for lithium-ion batteries due to high theoretical capacity, typically afflict by inferior conductivity and significant volume variation. Architecting heterogeneous structures with distinctive interfacial features can effectively regulate the electronic structure to favor electrochemical properties. Herein, an engineered carbon-coated nanosized Fe3 O4 /Cr2 O3 heterostructure with multiple interfaces is synthesized by a facile sol-gel method and subsequent heat treatment. Such ingenious components and structural design deliver rapid Li+ migration and facilitate charge transfer at the heterogeneous interface. Simultaneously, the strong coupling synergistic interactions between Fe3 O4 , Cr2 O3 , and carbon layers establish multiple interface structures and built-in electric fields, which accelerate ion/electron transport and effectively eliminate volume expansion. As a result, the multi-interface heterostructure, as a lithium-ion battery anode, exhibits superior cycling stability maintaining a reversible capacity of 651.2 mAh g-1 for 600 cycles at 2 C. The density functionaltheorycalculations not only unravel the electronic structure of the modulation but also illustrate favorable lithium-ion adsorption kinetics. This multi-interface heterostructure strategy offers a pathway for the development of advanced alkali metal-ion batteries.

A New Lithium‐Rich Zeolitic 10‐MR Zincolithosilicate MZS‐1 Hydrothermally Synthesized under High Pressure and Characterized by 3D Electron Diffraction

AbstractWe report the structure of a new high lithium content zincolithosilicate (MZS‐1) obtained after hydrothermal treatment under high pressure from a glass precursor. After synthesis microcrystalline mixture of phases was obtained among which the main phase was unknown. Due to the sub micrometric size of the crystallites its structure was determined from precession‐assisted 3D electron diffraction measured at 100 K and refined using the dynamical theory of diffraction. More accurate lattice parameters are obtained from Rietveld refinement of synchrotron powder data collected at the ambient temperature. The characteristic framework is described at the ambient temperature using an average unit cell a0=8.57999(5) Å, b0=14.12332(8) Å, c0=4.96827(3) Å in the space group Ccc2. The structure of the new zeolitic 10‐membered ring zincosilicate with chemical formula per unit cell (SiO2)2Zn0.408LiO(OH)2(Li,H)2.184 (Z=4) is composed of undulated silicate layers made of fused 6‐membered rings connected via vertices of (Zn,Li)O4 tetrahedra. A weak superstructure doubling the a0 parameter is observed and is explained by a Zn/Li ordering within the (Zn,Li)O4 layers.

In1-xGa1+xO3(ZnO)0.5: Synthesis, structure and cation distribution

Crystals of the quaternary compound In1-xGa1+xO3(ZnO)0.5 were grown by the optical floating-zone method using a mirror furnace with halogen lamps as heat source. X-ray diffraction (XRD) and electron diffraction yielded a hexagonal crystal system and the space group P63/mmc (No. 194). Structure refinement from single crystal XRD data at −90 °C (a ​= ​3.3137(1) Å; c ​= ​29.523(1) Å; wR2: 0.054) revealed a structure isotypic to YbFeO3(FeO)0.5 and consists of three different alternating layers: (i) layer of edge-sharing InO6 octahedra, (ii) a pair of two layers of corner-sharing (Ga/Zn)O4 tetrahedra corresponding to wurtzite structure type, and (iii) a layer of GaO5 trigonal-bipyramids (tbp). The polyhedra of layers (ii) and (iii) share corners with the InO6 octahedra, resulting in inverted orientations of the two (Ga/Zn)O4 layers in the wurtzite type region. Additionally, atomic resolution imaging in the electron microscope proves a perfect periodic stacking of the atomic layers. The analysis of individual crystals revealed an excess of Ga expressed by the composition range In1-xGa1+xO3(ZnO)0.5 with 0.20 ​≤ ​x ≤ 0.82, determined by energy dispersive X-ray spectroscopy (EDXS). Consequently, the octahedral site is occupied with In and Ga in a ratio of In:Ga ​= ​0.80:0.20 to 0.18:0.82, assuming that the tbp sites are only occupied by Ga. The transparent crystals as-received from floating-zone growth had a blueish color and became colorless after annealing at 1000 ​°C for 10 ​h in air. The as-prepared crystals are oxygen deficient and contain unpaired electrons (color centers) at vacant oxide sites proven by electron paramagnetic resonance with g-value of ca. 2.

Self-assembled epitaxial BiFeO3-Ni0.65Zn0.35Al0.8Fe1.2O4 nanobelt heterostructures on SrTiO3: Control of magnetic anisotropy, easy axis, and coercivity

Two-phase epitaxial Ni0.65Zn0.35Al0.8Fe1.2O4 (NZAFO) and BiFeO3 layers were deposited as self-assembled nanobeltlike heterostructures on (110) SrTiO3 single crystal substrates by switching pulsed laser deposition. The magnetic anisotropy and coercivity of the low loss high magnetostriction NZAFO phase were altered by the large shape anisotropy of this nanostructure relative to that of single crystal layers. The self-assembled heterostructures exhibited strong magnetic anisotropy along the in-plane direction, resulting in an ability to tune the coercivity from 2 Oe (single crystal NZAFO layers) to ∼650Oe (nanobelt heterostructure). The geometry of the nanobelt shape has a reflection on magnetic anisotropy: the orientation of the easy axis was altered from the in-plane direction. Rotation of the sample about its [11¯0] direction revealed that the hard magnetic axis was along the [001] with two easy directions at θ=±30°. In-plane rotation about the [110] revealed a strong magnetic anisotropy along [11¯0] and [001], which are the two directions that defined the rectangular shape of the nanobelts. Our findings demonstrate a self-assembled nanobelt heterostructural layer whose spinel ferrite phase coercivity and easy axes can be controlled by nanostructural features, which, in turn, modify the magnetic properties.

Meieranite, Na2Sr3MgSi6O17, a New Mineral from the Wessels Mine, Kalahari Manganese Fields, South Africa

Abstract A new mineral species, meieranite, ideally Na2Sr3MgSi6O17, has been found in the Wessels mine, Kalahari Manganese Fields, Northern Cape Province, South Africa. It occurs in isolated aggregates embedded in a matrix mainly of sugilite, along with minor aegirine and pectolite. Crystals of meieranite are up to 0.5 × 0.5 × 0.4 mm in size. No twinning is observed. The mineral is light blue to blue in transmitted and under incident lights, transparent with white streak, and has vitreous luster. It is brittle and has a Mohs hardness of 5.5; cleavage is good on {010} and no parting was observed. The measured and calculated densities are 3.41(3) and 3.410 g/cm3, respectively. Optically, meieranite is biaxial (–), with α = 1.610(1), β = 1.623(1), γ = 1.630(1) (white light), 2V (meas.) = 70(1)°, 2V (calc.) = 72°. The calculated compatibility index based on the empirical formula is –0.007 (superior). An electron microprobe analysis yields an empirical formula (based on 17 O apfu) of Na1.96(Sr2.91Ba0.03Ca0.03Pb0.02)Σ2.99(Mg0.62Mn0.28Co0.07Fe0.01)Σ0.98Si6.03O17, which can be simplified to Na2Sr3MgSi6O17. Meieranite is orthorhombic, with space group P21nb and unit-cell parameters a 7.9380(2), b 10.4923(3), c 18.2560(6) Å, and V 1520.50(8) Å3. Its crystal structure is characterized by two kinds of layers that alternate along [010]: layers of corner-sharing SiO4 and M2+O4 tetrahedra (M2+ = Mg, Mn, Co, Fe) and layers of NaO6 and SrO8 polyhedra. The tetrahedral layers consist of eight-, five-, and four-membered rings and are composed of [Si6O17] ribbons (parallel to [101]) linked together by MO4 tetrahedra. Most remarkably, the structure of meieranite is topologically identical to that of the nordite group of minerals, which has the general chemical formula Na3SrR3+M2+Si6O17, where R = Ce and La and M = Zn, Fe, and Mn. Accordingly, chemically, meieranite may be obtained through the coupled substitution of 2Sr2+ for (Na+ + R3+) in nordite.

Sputtered LiMn1.5Ni0.5O4 thin films for Li-ion micro-batteries with high energy and rate capabilities

The fabrication of high energy density on chip Li-ion micro-battery with high power capabilities is still a major challenge. For planar micro-batteries, thick electrode is mandatory for the energy issue but the rate capability of such thick layer is limited by the kinetic of the lithium ion within the film. In this work, sputtered LiMn1.5Ni0.5O4 (LMNO) layers delivering a high discharge capacity (60 µAh cm−2 µm−1), close to the theoretical value, while sustain high rate solicitation up to 10 C (6 min discharging time) are successfully deposited on functional platinum based current collector. Ni, Mn cation ordering is carefully investigated to reach the formation of ordered and disordered spinel layers. The optimal, disordered, LMNO thin film maintains 97% of the initial capacity during the first hundredth cycles, and the discharge capacity is stable up to 10 C, with an exceptional retention of the initial capacity of 84% at such high rate cycling. While the thickness of the sputtered disordered LMNO layers is limited on Al2O3 / Pt collector due to mechanical stress issue, 7.4 µm-thick film deposited on Al2O3 / Cr / Pt current collector reaches a high surface capacity close to 0.375 mAh cm−2 at 1C. This study clearly demonstrates the outstanding performance of disordered LMNO thick films to deliver high volumetric and surface capacities while exhibiting high rate ability for high energy and high power micro-battery.

New oxygen-deficient cationic-ordered perovskites containing turquoise-coloring Mn5+O4 tetrahedral layers

Ba6Na2M2Mn2O17 (M=Nb, Ta) oxides were synthesized by high-temperature solid-state reaction. The compounds adopt 6-layer perovskite-related structure (referred to as 6C) in P3̅m1, analogous to Ba6Na2Nb2P2O17. The 6C structure consists of cubic (c) BaO3 layers and pseudo-cubic (c') oxygen-vacancy-ordered BaO2 layers stacked according to a sequence of c'ccccc. Ordering of oxygen vacancies in oxygen-deficient c'-BaO2 layers leads to two successive isolated tetrahedral layers, which stabilize an unusual +5 oxidation state for Mn cations in the tetrahedral sites. In Ba6Na2M2Mn2O17, these two Mn5+O4 layers are sandwiched by two single octahedral NaO6 layers that connected by two successive octahedral NbO6 layers, forming alternative 2:1-ordered (Ba3NaM2O9)- and (Ba3NaMn2O8)+ perovskite-like units along the stacking direction. The Mn5+O4 tetrahedral units act as a turquoise chromophore in Ba6Na2M2Mn2O17, making these two compounds potential turquoise-coloring materials for the cool pigments.

Homologous Compounds ZnnIn2O3+n (n = 4, 5, and 7) Containing Laminated Functional Groups as Efficient Photocatalysts for Hydrogen Production.

Strong visible light absorption and high charge mobility are desirable properties for an efficient photocatalyst, yet they are hard to be realized simultaneously in a single semiconductor compound. In this work, we demonstrate that these properties coexist in homologous compounds ZnnIn2O3+n (n = 4, 5, and 7) with a peculiar layered structure that combines optical active segment and electrical conductive segment together. Their enhanced visible light absorption originates from tetrahedrally or trigonal-bipyramidally coordinated In atoms in Zn(In)O4(5) layers which enable p-d hybridization between In 4d and O 2p orbitals so that valence band minimum (VBM) is uplifted with a reduced band gap. Theoretical calculations reveal their anisotropic features in charge transport and functionality of different constituent segments, i.e., Zn(In)O4(5) layers and InO6 layers as being for charge generation and charge collection, respectively. Efficient photocatalytic hydrogen evolution was observed in these compounds under full range (λ ≥ 250 nm) and visible light irradiation (λ ≥ 420 nm). High apparent quantum efficiency ∼2.79% was achieved for Zn4In2O7 under full range irradiation, which is almost 5-fold higher than their parent oxides ZnO and In2O3. Such superior photocatalytic activities of these homologous compounds can be understood as layer-by-layer packing of charge generation/collection functional groups that ensures efficient photocatalytic reactions.

Spinel-structured surface layers for facile Li ion transport and improved chemical stability of lithium manganese oxide spinel

Li-ion conducting spinel-structured oxide layer with a manganese oxidation state close to being tetravalent was prepared on aluminum-doped lithium manganese oxide spinel for improving the electrochemical performances at the elevated temperatures. This nanoscale surface layer provides a good ionic conduction path for lithium ion transport to the core and also serves as an excellent chemical barrier for protecting the high-capacity core material from manganese dissolution into the electrolyte. In this work, a simple wet process was employed to prepare thin LiAlMnO4 and LiMg0.5Mn1.5O4 layers on the surface of LiAl0.1Mn1.9O4. X-ray absorption studies revealed an oxidation state close to tetravalent manganese on the surface layer of coated materials. Materials with these surface coating layers exhibited excellent capacity retentions superior to the bare material, without undermining the lithium ion transport characteristics and the high rate performances.

Orientation-Controlled Growth of LiNi0.5Mn1.5O4 Layers Directly Deposited on Current Collectors By Using Flux Coating and Their Electrochemical Properties

Newly developed cathode structures are strongly required for the improvement of LIB properties, including energy and power density, lifetime. Conventionally used cathodes consist of micrometer sized polycrystals of active materials, and additives that facilitate Li ion and electron transportation. Use of nanosized single crystals is expected to make huge improvements because those nanostructures might provide shorter diffusion pathways for ionic transportation. Here, we proposed fabrication of densely-packed orientationaly-controlled LiNi0.5Mn1.5O4 (LNMO) crystal layers directly onto a current collector using flux-coating. As shown in Figure 1, SEM observations revealed that those crystals have octahedral shape with well-developed facets. This shape reflected well the crystal structure of LiNi0.5Mn1.5O4, which belongs to cubic system with Fd-3m space group. Even though the filling rate of the LiNi0.5Mn1.5O4 crystal in the positive electrode reached more than 95% without any additives, the crystal layer exhibited excellent LIBs properties as same as conventionally used powdered electrode with an assistance of many additives. The first charge and discharge capacities of the LIB, containing 14 mm-thick LiNi0.5Mn1.5O4 crystal layer as a cathode were 111 and 105 mA∙h∙g-1 at 1 C. The retention rate after 30 cycles was 97% for each cycle at 0.3C. These results proved that the flux-coating offered growth of seamlessly connected layers of LNMO crystals on current correctors. Further detail crystallographic natures and electrochemical characteristics of other active material crystals will present in the ECS 227th Meeting.

Characterization of thin films of the solid electrolyte Li(x)Mg(1-2x)Al(2+x)O4 (x = 0, 0.05, 0.15, 0.25).

RF-sputtered thin films of spinel Li(x)Mg(1-2x)Al(2+x)O4 were investigated for use as solid electrolyte. The usage of this material can enable the fabrication of a lattice matched battery stack, which is predicted to lead to superior battery performance. Spinel Li(x)Mg(1-2x)Al(2+x)O4 thin films, with stoichiometry (x) ranging between 0 and 0.25, were formed after a crystallization anneal as shown by X-ray diffraction and transmission electron microscopy. The stoichiometry of the films was evaluated by elastic recoil detection and Rutherford backscattering and found to be slightly aluminum rich. The excellent electronic insulation properties were confirmed by both current-voltage measurements as well as by copper plating tests. The electrochemical stability window of the material was probed using cyclic voltammetry. Lithium plating and stripping was observed together with the formation of a Li-Pt alloy, indicating that Li-ions passed through the film. This observation contradicted with impedance measurements at open circuit potential, which showed no apparent Li-ion conductivity of the film. Impedance spectroscopy as a function of potential showed the occurrence of Li-ion intercalation into the Li(x)Mg(1-2x)Al(2+x)O4 layers. When incorporating Li-ions in the material the ionic conductivity can be increased by 3 orders of magnitude. Therefore it is anticipated that the response of Li(x)Mg(1-2x)Al(2+x)O4 is more adequate for a buffer layer than as the solid electrolyte.

Magnetically encoded luminescent composite nanoparticles through layer-by-layer self-assembly.

Sensitive and rapid detection of multiple analytes and the collection of components from complex samples are important in fields ranging from bioassays/chemical assays, clinical diagnosis, to environmental monitoring. A convenient strategy for creating magnetically encoded luminescent CdTe@SiO2 @n Fe3 O4 composite nanoparticles, by using a layer-by-layer self-assembly approach based on electrostatic interactions, is described. Silica-coated CdTe quantum dots (CdTe@SiO2 ) serve as core templates for the deposition of alternating layers of Fe3 O4 magnetic nanoparticles and poly(dimethyldiallyl ammonium chloride), to construct CdTe@SiO2 @n Fe3 O4 (n=1, 2, 3, …︁) composite nanoparticles with a defined number (n) of Fe3 O4 layers. Composite nanoparticles were characterized by zeta-potential analysis, fluorescence spectroscopy, vibrating sample magnetometry, and transmission electron microscopy, which showed that the CdTe@SiO2 @n Fe3 O4 composite nanoparticles exhibited excellent luminescence properties coupled with well-defined magnetic responses. To demonstrate the utility of these magnetically encoded nanoparticles for near-simultaneous detection and separation of multiple components from complex samples, three different fluorescently labeled IgG proteins, as model targets, were identified and collected from a mixture by using the CdTe@SiO2 @n Fe3 O4 nanoparticles.

Two-Dimensional Magnetic Correlations and Partial Long-Range Order in Geometrically FrustratedSr2YRuO6

Neutron diffraction on the double perovskite Sr(2)YRuO(6) with a quasi-fcc lattice of Ru moments reveals planar magnetic correlations that condense into a partial long-range ordered state with coupled alternate antiferromagnetic (AFM) YRuO(4) square layers coexisting with the short-range correlations below T(N1) = 32 K. A second transition to a fully ordered AFM state below T(N2) = 24 K is observed. The reduced dimensionality of the spin correlations is arguably due to a cancellation of the magnetic coupling between consecutive AFM square layers in fcc antiferromagnets, which is the simplest three-dimensional frustrated magnet model system.

Melilite-type blue chromophores based on Mn3+ in a trigonal-bipyramidal coordination induced by interstitial oxygen

A new, earth-abundant, environmentally benign, and stable inorganic blue chromophore series Sr2(Mg1−xMnx)Ge2O7+δ has been prepared and characterized by X-ray absorption spectroscopy, synchrotron X-ray diffraction, and ab initio total energy calculation. As the content of Mn in the compound was increased, the color changed from white (for x = 0.0) to sky blue, deep blue, and finally black body color (for x = 1.0). Sr2MgGe2O7 has the melilite-type structure comprising Mg(2+)O4 and GeO4 tetrahedra. On the other hand, it was found that the Mn ion in Sr2(Mg1−xMnx)Ge2O7+δ is mainly trivalent and that the additional oxygen atom infiltrates into the lattice to compensate for the excess positive charge. The additional oxygen atom occupies an interstitial site, leading to the formation of Mn(3+)O5 trigonal bipyramid and Ge(4+)O5 square pyramid. As the driving force for the Mn(3+)O5 formation, the tendency for improving the lattice coherency between BO4–B′O4 and AO8 layers in the melilite A2BB′2O7 is suggested.

Ba2Co9O14: New Inorganic Building Blocks with Magnetic Ordering through Super-Super Exchanges Only

Ba2Co2+3Co3+6O14 has been prepared by conventional solid-state reaction between BaO2 and CoO. Its crystal structure has been refined from single-crystal X-ray diffraction data and powder neutron diffraction, a = 5.6963(8) A, c = 28.924(6) A, space group R3m, Z = 3, R1 = 4.44%, wR2 = 10.96%. It shows evidence of new building blocks called T‘ (ch‘h‘c stacking sequence of cubic O4 and hexagonal BaO3 layers) by analogy with the related T-blocks (hh‘h‘h) of the barium hexaferrites. T‘ consists of CoII,IIIO2 brucite-like layers pillared by CoIIO4 tetrahedra and CoIII3O12 octahedral trimers. Below TN = 39 K, tetrahedral and octahedral high spin CoII (S = 3/2) diluted in the framework mainly containing low spin CoIII (S = 0) interact through CoII−O−O−CoII through super-super exchanges (SSE) only. The analysis of the competition between the multiple SSE paths has been performed through geometrical considerations. The magnetic moments are lying antiferromagnetically in the a,b plane in good agreement with the magn...

Pb3Mn5V2O16: A New Lead Manganese Vanadate with Double MnII/MnIV Valence.

AbstractFor Abstract see ChemInform Abstract in Full Text.