Studies on the system V3O5 /1b Ti3O5

The system (V_1?xTi_x)₃O₅ has been studied by means of X-ray powder photography, DTA and magnetic susceptibility measurements. A continuous series of solid solutions has been found for samples prepared at 1175 K, while samples prepared at 1275 K showed the solid solubility in the V₃O₅ end phase to be limited by $\text{x}\text{< 0.7}$ DTA studies have shown that the peak associated with the V₃O₅(low) /1b V₃O₅(high) transition disappears at $\text{x}\text{= 0.024}$. The DTA studies have also confirmed the existence of a phase transition in γ-Ti₃O₅ ($\text{x}\text{= 1}$) at 227 K.     

Magnetic anisotropy of V3O5

The magnetic anisotropy of V₃O₅ was investigated by magneto-torque measurements in the temperature range from 4.2 to 300 K. It has been confirmed that the Néel temperature is about 75 K and that two of the three principal axes vary with temperature in both the paramagnetic and antiferromagnetic states. The results are explained on a simplified four-sublattice model.     

Phase transition in V3O5

A phase transition at 420°K previously unreported, has been discovered in V₃O₅. The transition is characterized by an endothermic DTA peak on heating and an abrupt change in the electrical resistivity at the same temperature. Results from X-ray analysis of the V₃O₅ samples exhibiting the transition agree very well with the values reported by Andersson (1). Powder diffraction analysis of the high temperature phase indicates that there is a small change in the cell volume but the crystal apparently conserves its symmetry through the transition.     

Hydrogen insertion compounds of V6O13 and V2O5

Hydrogen insertion compounds H_xV₆O₁₃ (0<x?7.3) have been synthesised and characterised. Unit-cell dimensions, determined from powder X-ray analysis, indicate that the hydrogen-insertion reaction proceeds topotactically. In addition, a low-hydrogen-content phase of H_xV₂O₅ of similar structure to V₂O₅ has been prepared.     

V3.2W1.8O13 and studies of the V2O5WO3VO2 ternary system

The tungsten/vanadium ratios for the known ternary compounds in the V₂O₅WO₃VO₂ chemical system are characterized. The compounds V_2.5W_.5O₇ and V₂WO_7.5 are the n = m = 3 and n = m = 4 members of a sreies of M-niobia like crystallographic shear structures. We have found the n = m = 5 member of the series at the composition V_3.2W_1.8O₁₃, and report its crystallographic unit cell, powder x-ray diffraction pattern and range of temperature stability.     

An ESR study of the heterogeneous system Cr2O3V2O5

An ESR study of the ‘products’ of the high temperature solid state reaction xCr₂O₃+yV₂O₅ ($\text{0.05≦(}\text{x}\text{y}\text{)≦2.0}$), aided by powder X-ray diffraction and IR spectra, has revealed (i) ‘unfamiliar’ paramagnetic intermediates Cr⁴⁺ and Cr⁵⁺, (ii) provided some clues to the oxidation of Cr³⁺ to Cr⁶⁺, and (iii) demonstrated a variety of exchange interactions involving V⁴⁺ and Cr³⁺.     

Microdurete de monocristaux de V2O5

Microhardness measurements of V₂O₅ single crystals were undertaken in order to study the anisotropy of their mechanical properties. Results are presented for both Vickers and Knoop hardness values on (100), (010) and (001) planes of orthorhombic V₂O₅ single crystals.A strong anisotropy is observed in each plane. As expected, hardness appears to be particularly small when the diamond indenter is parallel to the clivage directions in the (100) and (001) planes. A remarkably small value is observed along the [100] direction in the (001) plane, which could be related to the model proposed by Gillis in order to explain the structural charge into V₆O₁₃ occuring in non-stoichiometric V₂O₅.     

Growth and structure of electron beam evaporated V2O5 thin films

The growth, structure and room temperature electrical conductivity of electron beam evaporated V₂O₅ thin films were studied in detail as a function of deposition temperature. The films deposited at T_s≈553 K and subsequently annealed in oxygen atmosphere at 693 K exhibited orthorhombic layered structure.     

An oxides-hydrothermal approach from bulky V2O5 powder to V3O7·H2O nanoribbons or V3O7 nanoflowers in various ethanol/water mixed solvent

V₃O₇·H₂O nanoribbons and V₃O₇ nanoflowers are firstly obtained via facile oxides-hydrothermal (O-HT) route. V₂O₅ bulk-phase powder is directly used as precursor. The 1:1 ethanol/water and absolute ethanol are made as solvent for obtaining nanomaterials of vanadium oxides with different morphologies and structures. Characterizations of the samples are carried out using XRD, TG, FTIR, Raman-Spectra, SEM, TEM, HRTEM, SAED, and UV-vis. The large-scale fine ribbon-like V₃O₇·H₂O nanobelts with thickness ca. 20 nm and length ca. 20-40 μm are obtained in 1:1 (v/v) ethanol/water mixed solvent. The V₃O₇ nanoflowers are constructed by numerous whisker-like nanocrystal or petal-like are obtained in absolute ethanol solvent with the thickness about 20 nm and the size ca. 2-3 μm. The formation mechanism of the sample is discussed.     

The crystal structure of Ni5TiB2O10

The crystal structure of Ni₅TiB₂O₁₀ was determined by single crystal X-ray analysis. The compound has the same structure as the mineral ludwigite. The orthorhombic celldimensions and space group are $\text{a}\text{=9.206(7)}\text{A}\text{?}$, $\text{b}\text{=12.224(9)}\text{A}\text{?}$, $\text{c}\text{=2.994(2)}\text{A}\text{?}$, Pbam z=2. Ti and Ni are disordered on one equipoint.     

Un oxyde de rhenium en relation de structure avec V2O5

The authors describe a rhenium oxide, Re₂O₅. It was revealed and investigated by means of transmission electron microscopy and single diffraction. The orthorhombic unic cell is related to the ReO₃ cubic cell in terms of: b=c=a_c= 3,747 A and a= 2 $\text{a}{}_{\mathrm{c}}\text{√2= 10,598}\text{A}\text{?}$. The crystal structure is explained from patterns, according to the structural scheme of Me₂O₅ and particularly to vanadium pentoxide structure. It is obvious that there exists a close relationship between them.     

The crystal structure of eulytite Pb3BiV3O12

The crystal structure of Pb₃BiV₃O₁₂ was solved using single-crystal X-ray diffraction technique. The compound crystallizes in the cubic system (No. 220) with eulytite structure with a = 10.7490(7) Å, V = 1241.95(14) Å³ and Z = 4. The final R₁ value of 0.0198 (wR₂=0.0384) was achieved for 359 independent reflections during the structure refinement. The Pb²⁺ and Bi³⁺ cations occupy the special position (16c) while the oxygen anions occupy the general position (48e) in the crystal structure. Unlike many other eulytite compounds, all the crystallographic positions are fully occupied. The structure consists of edge-shared Pb/Bi octahedra linked at the corners to independent [VO₄]³⁻ tetrahedra units, generating a eulytite-type network in the crystal lattice.     

Conversion of V2O5·xH2O into orthorhombic V2O5 single-crystalline nanobelts

Orthorhombic V₂O₅ single-crystalline nanobelts have been synthesized by hydrothermal treating V₂O₅·xH₂O precipitate derived from aqueous solution of V₂O₅ and H₂O₂. The synthetic method is facile, fast, environmental friendly, and easy to scale up. The V₂O₅ single-crystalline nanobelts are 30-80 nm in width, 30-40 nm in thickness, and lengths up to several tens of micrometers. The V₂O₅·xH₂O precursor is crucial for the formation of orthorhombic V₂O₅ single-crystalline nanobelts. The influences of synthetic parameters, such as reaction time and reaction temperature, on the crystal structures and morphologies of the resulting products have been investigated. Time-dependent experiments show that V₂O₅·xH₂O are dehydrated gradually and converted into orthorhombic V₂O₅ single-crystalline nanobelts. High reaction temperature also favors the formation of orthorhombic V₂O₅ nanobelts.     

IR spectra of VO2 and V2O3

IR spectra of the tetragonal modification of VO₂ and of the trigonal form of V₂O₃ are recorded at room temperature and compared with that of V₂O₅. The investigated samples of the two lower-valent vanadium oxides, obtained on temperature-programmed reduction treatment, were also characterized with diffuse reflectance and electron-paramagnetic resonance spectra. The effect of atmospheric oxygen on these materials was revealed with XPS measurements and also studied with IR spectra.     

Synthesis and crystal structure of triphosphate RbPrHP3O10

Crystals of RbPrHP₃O₁₀ have been grown by the flux technique and characterized by single-crystal X-ray diffraction. RbPrHP₃O₁₀ crystallizes in the triclinic space group with lattice parameters: a = 7.0655(5), b = 7.7791(4), c = 8.6828(6) Å, α = 74.074(3), β = 74.270(3), γ = 82.865(2)°, V = 441.09(5) ų, Z = 2. The crystal structure has been solved yielding a final R(F²) = 0.0443 and R_w(F²) = 0.1426 for 1955 independent reflections (F_o² ≥ 2σ(F_o²)). The structure of RbPrHP₃O₁₀ consists of PrO₈ polyhedra and P₃O₁₀⁵⁻ groups sharing oxygen atoms to form a two-dimensional framework; the PrO₈ polyhedra form infinite chains by edge-sharing. Each Rb⁺ ion is bonded to 10 oxygen atoms, these ions are located between chains formed of (HP₃O₁₀)⁴⁻. The energies of the vibrational modes of the crystal were obtained from measurements of the infrared spectrum.     

Magneto-torque measurement on V6O13

Magnetic anisotropy of V₆O₁₃ was investigated by the magneto-torque and the magnetic susceptibility measurement in the temperature range from 4 to 300 K. It has been clarified that V₆O₁₃ is antiferromagnetic below about 50 K and the direction of antiferromagnetic spin is parallel to the $\text{b}$-axis.     

Hydratation et texture fibreuse de V2O5 amorphe

Reversible hydration of amorphous V₂O₅ has been performed in order to study the effect of water upon the properties of the oxide. A drastic change of the ESR spectrum is observed, which turns from anisotropic to isotropic upon hydration. This has been interpreted in terms of a brownian motion which, by analogy with the V₂O₅ gels, is supposed to be due to the fibrous texture of the amorphous oxide.     

The crystal structures of the high and low temperature forms of rhombohedral Cr-doped V2O3

X-ray diffraction studies of single crystals of (Cr_0.01V_0.99)₂O₃ have shown that the transition from the low to high temperature rhombohedral forms of this material proceeds without changing the orientation of the unit cell axes. The structures of both the high and low temperature forms have been determined at 23°C using single crystal x-ray diffraction techniques. Both forms are isomorphous with V₂O₃, but upon heating the M-M distance across the shared octahedral face increases from 2.700(1) A to 2.747(1) A while the M-M distance across the shared edge increases from 2.884(1) A to 2.917(1) A. The M-O distances increase by a maximum of 0.011A. The low temperature form of (Cr_0.01V_0.99)₂O₃ is isostructural with V₂O₃ while the high temperature form is isostructural with (Cr_0.038V_0.962)₂O₃.     

The system Eu2O3SrOV2O3 at 1400°C

Phase relations in a portion of the system Eu₂O₃SrOV₂O₃ have been investigated at 1400°C and a reduced pressure (10^?4mmHg). On heating, part of the trivalent vanadium was oxidized to the tetravalent state by atomospheric oxygen. The following ternary-phase solid solutions were identified: Eu_1?xSr_xVO_3?0.1x, SrO·2Eu_1?x?Sr_xVO_3?0.1x and SrO·Eu_1?xSr_xVO_3?0.1x.     

The possibility of intercalating alkali metals in a glass of the system V2O5 - P2O5

A semi-conducting phosphovanadate glass was tested as a possible material for positive electrode in solid state batteries.O.c. voltage with alkali metal (3.6 V/Li and 3.4 V/Na) is higher than for crystallized vanadium oxides and chemical intercalation of sodium or lithium is obtained using halogenated salts dissolved in organic solvents.