Lithium-ion mobility in layered oxides Li2Ca1.5Nb3O10,Li2Ca1.5TaNb2O10 and Li2Ca1.5Ta2NbO10,enhanced by supercell formation

The formation of a supercell and its impact on lithium-ion conductivity have been studied through syn-thesis of three layered oxides,Li2Ca1.5Nb3O10,Li2Ca1.5TaNb...     

Crystal structure of a new lithium indium borate Li3InB2O6

Single crystals of synthetic Li₃InB₂O₆ were obtained by heating a mixture of Li₂CO₃, In₂O₃ and B₂O₃; its formula was determined by the resolution of the structure from X-ray diffraction data. The compound is monoclinic, space group P2₁/n; the unit cell parameters are a=5.168(5) Å, b=8.899(9) Å, c=10.099(10) Å, β=91.112(17)°; Z=4. The crystal structure was solved from 669 reflections until R=0.0249; it exhibits a three-dimensional framework of vertex-sharing InO₅ trigonal bipyramids and BO₃ triangles, which isolates Li ions in channels. This structure is characterized by unusual oxygenated environments of In cations and of one of the three Li cations, which are forming more or less regular trigonal bipyramids. This compound melts incongruently at 827 °C; the powder may be obtained by annealing at 750 °C a mixture of Li₂CO₃, In₂O₃ and B₂O₃.     

Hydrothermal synthesis and crystal structure of two new hydrated alkaline earth metal borates Sr3B6O11(OH)2 and Ba3B6O11(OH)2

Two new hydrated borates Sr(3)B(6)O(11)(OH)(2) (1) and Ba(3)B(6)O(11)(OH)(2) (2) were hydrothermally synthesized. Their structures were determined by single-crystal X-ray diffraction and further characterized by IR, powder XRD, and DSC/TGA. Compound 1 crystallizes in the triclinic space group P-1 with unit cell parameters of a = 6.6275(13) ?, b = 6.6706(13) ?, c = 11.393(2) ?, α = 91.06(3)°, β = 94.50(3)°, and γ = 93.12(3)°, while compound 2 crystallizes in the noncentrosymmetric monoclinic space group Pc with a = 6.958(14) ?, b = 7.024(14) ?, c = 11.346(2) ?, and β = 90.10(3)°. In spite of the differences in symmetry and packing of the borate chains, both structures consist of the same fundamental building block (FBB) of a [B(6)O(11)(OH)(2)](-6) unit and three unique alkaline earth metal atoms.     

Crystal growth and structure determination of oxygen-deficient Sr6Co5O15

Large single crystals of oxygen-deficient Sr6Co5O(15-delta) compounds, i.e., Sr6Co5O14.70 and Sr6Co4.9Ni0.1O14.36, were obtained by using K2CO3 flux in the presence of additives of transition metal oxides. The single-crystal structure determination shows that the structures of Sr6Co5O14.70 and Sr6Co4.9Ni0.1O14.36 crystallize in the space group R and can be described as one-dimensional face-sharing CoO3 polyhedral chains and Sr cation chains. Unlike the other known 2H-perovskite-related oxides in which the polyhedral chains consist of octahedra (Oh) and trigonal prism (TP), the structure of Sr6Co5O14.70 and Sr6Co4.9Ni0.1O14.36 contain Oh and intermediate polyhedra (IP) and can be attributed to a general structure formula A6A'2B3O(15-delta), which is closely related to the known A6A'B4O15 phases by shifting of a B atom and the O3 triangle along the c axis. Further study on O3 reveals that this oxygen position splits into two independent positions, corresponding to polyhedral geometry of IP and TP, respectively. Therefore, the polyhedral chain in the structure should be more precisely described as a random composite of the 4Oh + TP and 3Oh + 2IP. This model is used to interpret the magnetic properties, although not quantitatively. The 4-D structure analysis was also conducted for both Sr6Co5O14.70 and Sr6Co4.9Ni0.1O14.36 with a commensurate modulated structure in a 4-D superspace group, R3m(00gamma)0s, gamma = p/k = 3/5. By considering the same 4-D superspace group R3m(00gamma)0s but different t-phases, one can understand the structure relationship between Sr6Co5O14.70 and Sr6Rh5O15.     

Transparent thin films of Bi2WO6, Bi4Ti3O12 and Sr0.75Ba0.25Nb2O6

Transparent thin films were prepared by a sol–gel method starting from precursor formation in solution, subsequent spin coating followed by a heating ramp up to a maximum of 700 °C. Starting from a Bi₂MoO₆ synthesis route, the phase formation and thin film processing of the bismuth containing materials Bi₂WO₆, Bi₃Ti₄O₁₂ and additionally of the tungsten–bronze structure Sr_0.75Ba_0.25Nb₂O₆ were studied. Spin coating was used to adjust the film thickness in a wide range from 6 to 200 nm. All films were obtained as multicrystalline pure phases according to X-ray diffraction analyses. Scanning electron micrographs revealed homogeneous coatings composed of nanoparticles with a crystallite size varying between 20 and 100 nm, furthermore the UV–VIS spectra demonstrated a high transparency of the films, 80–90% at 600 nm.     

Neue Phasen in den Systemen Nb2O5-WO3 und Ta2O5-WO3

Zusammenfassung Bei Untersuchungen im WO₃-ärmeren Bereich der Systeme Nb₂O₅-WO₃ und Ta₂O₅-WO₃ bis zum Molverhältnis Me₂O₅:WO₃=1:2 wurden folgende Phasen neu gefunden: 40 Nb₂O₅·WO₃–20 Nb₂O₅·WO₃ (Phasenbreite), 13 Nb₂O₅· ·4 WO₃, 9 Nb₂O₅·8 WO₃ (Tieftemperaturphase), 9 Ta₂O₅· ·8 WO₃; ferner eine Mischphase des T-Ta₂O₅, die bis zur Zusammensetzung 13 Ta₂O₅·4 WO₃ (bei 1300° C) reicht. Weitere Phasen wurden im System Nb₂O₅-WO₃ bei den Molverhältnissen 8:1–6: 1, 7:3, 8:5 und 9:8 (Hochtemperaturphase) beobachtet.49. Mitt.:H. Schäfer, R. Gruehn undF. Schulte, Angew. Chemie, im Druck.     

Perovskite related phases in the Sr5Nb4O15 - SrTiO3 - Sr4Nb2O9 system

Phase relations have been investigated within the Sr₅Nb₄O₁₅−SrTiO₃−Sr₄Nb₂O₉ region of the SrO−Nb₂O₅−TiO₂ system with a view to clarifying the occurrence of fully oxidised perovskite related phases. Overall phase analysis was carried out by powder X-ray diffraction and microstructures were clarified by transmission electron microscopy. There is only one main composition triangle in this area at 1350°C. The tie-line between Sr₅Nb₄O₁₅ and SrTiO₃ contains a homologous series of hexagonal layered perovskite phases including Sr₆Nb₄TiO₁₈ and Sr₇Nb₄Ti₂O₂₁. The phase Sr₄Nb₂O₉ is a nonstoichiometric phase with a disordered perovskite structure. There is some extension of this phase along the Sr₄Nb₂O₉−SrTiO₃ tie-line, but SrTiO₃ does not show a significant composition range. Samples with a composition Sr₄Nb₂O₉, when heated at 900°C show several ordered modifications. Samples along the Sr₄Nb₂O₉−SrTiO₃ tie-line which are annealed at 900°C contain these ordered materials together with samples showing considerable short range order which increases as the Ti content increases.     

Sr3Mn2O6 and Sr3FeMnO6 for oxygen and hydrogen evolution electrocatalysis

Journal of Solid State Electrochemistry - Quasi-two-dimensional oxides Sr3Mn2O6 and Sr3FeMnO6 have been synthesized and their bifunctional electrocatalytic activity toward both half-reactions of...     

Oxygen ionic transport in Bi2O3-based oxides: The solid solutions Bi2O3–Nb2O5

The minimum concentration of niobium to stabilize the fluorite-type f.c.c. phase in the Bi₂O₃–Nb₂O₅ oxide system at temperatures below 996 K was ascertained to be about 10 mol%. Thermal expansion, electrical conductivity and crystal lattice parameters of the Bi(Nb)O_1.5+δ solid solutions decrease with increasing niobium content. Thermal expansion coefficients were calculated from the dilatometric data to be (10.314.5)×10⁻⁶ K⁻¹ at temperatures in the range 300–700 K and (17.526.0)×10⁻⁶ K⁻¹ at 700–1100 K. The conductivity of the Bi_{1− x} Nb _x O_1.5+δ ceramics is predominantly ionic. The p-type electronic transference numbers of the Bi(Nb)O_1.5+δ solid solutions in air were determined to be less than 0.1. Annealing at temperatures below 900 K results in a sharp decrease in conductivity of the Bi_{1− x} Nb _x O_1.5+δ ceramics. Received: 18 August 1997 / Accepted: 20 October 1997     

Synthesis and research of phase composition of alloys Nb2O5: Fe3+ and Ta2O5: Fe3+

The conditions were studied for the synthesis of niobium and tantalum pentoxide containing iron impurity introduced into the strip liquor after extraction separation of niobium and tantalum and subsequent precipitation of metal hydroxides with ammonia. A phase composition of the synthesized alloys was examined by X-ray diffraction and infrared spectroscopy.     

Li2MTi6O14 (M=Sr,Ba): new anodes for lithium-ion batteries

Isostructural Li₂MTi₆O₁₄ (M=Sr, Ba) materials, prepared by a solid state reaction method, have been investigated as insertion electrodes for lithium battery applications. These titanate compounds have a structure that consists of a three-dimensional network of corner- and edge-shared [TiO₆] octahedra, 11-coordinate polyhedra for the alkali-earth ions, and [LiO₄] tetrahedra in tunnels that also contain vacant tetrahedral and octahedral sites. Electrochemical data show that these compounds are capable of reversibly intercalating four lithium atoms in a three-stage process between 1.4 and 0.5 V vs. metallic lithium. The electrodes provide a practical capacity of approximately 140 mAh/g; they are, therefore, possible alternative anode materials to the lithium titanate spinel, Li₄Ti₅O₁₂. The lithium intercalation mechanism and crystal structure of Li₂MTi₆O₁₄ (M=Sr, Ba) electrodes are discussed and compared with the electrochemical and structural properties of Li₄Ti₅O₁₂. The area-specific impedance (ASI) of Li/Li₂SrTi₆O₁₄ cells was found to be significantly lower than that of Li/Li₄Ti₅O₁₂ cells.     

Crystal Structures of Na3PO2S2 · 11H2O and Na3POS3 · 11H2O

Summary.  Single crystals of sodium dithiophosphate undecahydrate (Na₃PO₂S₂ · 11H₂O) and sodium trithiophosphate undecahydrate (Na₃POS₃ · 11H₂O) were grown from aqueous solution. The crystal structures of Na₃PO₂S₂ · 11H₂O (P2₁2₁2₁; a = 1248.1(1), b = 945.2(1), c = 1383.1(1) pm; R ₁ = 0.0202, wR ₂ = 0.0502) and Na₃POS₃ · 11H₂O (Pna2₁; a = 1262.0(2), b = 947.6(2), c = 1431.5(2) pm; R ₁ = 0.0720, wR ₂ = 0.1371) are related to each other in a sense that all constituting units are arranged in similar positions and with similar orientations. The geometries of the anions were determined with high accuracy; thus, the structural parameters of the POS³⁻ ₃ anion were measured for the first time. Received September 25, 2001. Accepted January 21, 2002     

Kristallchemische Untersuchungen an den Phasen: (I) Zn(V0,12Nb0,88)2O6, (II) Zn(V0,28Ta0,72)2O6 und (III) Zn(Nb0,58Ta0,42)2O6

Crystal Chemistry Examinations of the Phases: (I) Zn(V_0.12Nb_0.88)₂O₆, (II) Zn(V_0.28Ta_0.72)₂O₆, and (III) Zn(Nb_0.58Ta_0.42)₂O₆ Single crystals of the quaternary phases ( I ), ( II ), and ( III ) were prepared by high temperature technique and investigated by X-ray single crystal methods. Phase ( I ) crystallizes in the columbite Structure. Phase ( II ) deviates from the ternary compounds (ZnV₂O₆, ZnTa₂O₆) and appears in trirutile type. In phase ( III ) the octahedra arrangement of the tri-α-PbO₂ Structure is realized.     

Determination of Impurity Cerium in K3Li2Nb5O15 Crystal by Inductively Coupled Plasma Mass Spectrometry

A method was presented for the determination by Inductively Coupled Plasma Mass Spectrometry (ICP-MS) of Impurity Cerium in Potassium Lithium Niobate (K₃Li₂Nb₅O₁₅) Crystal. A standard model Perkin-Elmer/SCIEX ELAN 5000 ICP Mass Spectrometer was used. The instrument was operated at a RF power setting of 1.05 kW. A standard demountable quartz torch with 1.2mm id alumina injector tube was used with the following argon gas flow rates:nebulizer 0.84L/min,auxiliary 0.80L/min,and coolant 15.0L/min.