Photocatalytic reduction of cadmium over CuFeO2 synthesized by sol–gel

The Cd²⁺ photo-electrodeposition was successfully carried out in air-equilibrated aqueous CuFeO₂ suspension. The delafossite CuFeO₂ is p-type semiconductor characterized by a low optical gap, properly matched to the sun spectrum, and a long term chemical stability in neutral solution. It has been elaborated by the sol–gel technique where the specific surface area is increased via the surface/bulk ratio. The TG/DSC plots and IR spectra show that the solid phases are formed only at temperatures exceeding 400 and at 700 °C, the system is mixed phases. When fired at 950 °C under nitrogen flow, the delafossite has been identified (CuO + CuFe₂O₄ → CuFeO₂ + ½O₂). All the XRD lines index in a hexagonal unit cell with the lattice constants a = 284.2 and c = 169.4 pm. The photocurrent onset potential (+0.35 V_SCE) is close to the flat band potential (+0.23 V_SCE) determined from the capacitance measurement. CuFeO₂/Cd²⁺ solution is a self photo-driven system, the absorption of light promotes electrons into CuFeO₂–CB with a potential (?0.93 V_SCE) sufficient to reduce Cd²⁺. This occurs because of the dark Cd²⁺ adsorption on the surface powder. The system was optimized with respect to the following physical parameters: pH 6.8, Cd²⁺ (100 ppm) and a mass concentration C_m (1 mg catalyst/ml solution). The hetero-system CuFeO₂/TiO₂ has been also reported for a comparative purpose. Prolonged irradiation (>50 min) was accompanied by a pronounced decrease in the rate of Cd-deposition owing to the competitive water reduction. Indeed, the generated bi-functional CuFeO₂/Cd particles account for the low over-potential of hydrogen and favour its evolution in aqueous solution.     

Crystallisation of some mixed Na/V and K/V fluorides by solvothermal methods

Single crystals of several phases in the Na–V–(O)F and K–V–(O)F systems have been grown using a mild solvothermal route in water/ethylene glycol. At a temperature of 100 °C the V⁴⁺-containing oxyfluoride phases Na₄V₂O₂F₈ and K₂VOF₄ are prepared, exhibiting dimeric and chain-like vanadium oxyfluoride units, respectively. On raising the reaction temperature to 220 °C reduction to V³⁺ occurs, and three different two-dimensional sheet structures are crystallised, NaVF₄, KVF₄ and K₅V₃F₁₄. Precise crystal structures are reported for the latter two, which represent members of the Dion–Jacobson and Chiolite families, respectively.     

Cation-deficient lanthanum manganite oxides: Experimental and theoretical studies

Cation-deficient lanthanum manganite oxides with 0.8 ≤ La/Mn ≤ 1.25 were synthesized using a multi-step decomposition of gel precursors and investigated from experimental and theoretical point of view. The XRD (X-Ray Diffraction) analysis of the mixed LaMnO₃ oxide crystal concludes to a hexagonal structure, space group R-3c, excluding the presence of pure oxides such as La₂O₃, Mn₂O₃, or MnO₂ whatever the ratio La/Mn is. Oxides with nominal formulae La_1?xMnO_3+y and LaMn_1?x′O_3+y contain more than one defect structure involving valence defect (holes h), anionic vacancies as well as cationic vacancies in A and B sublattices of the perovskite structure. With the increase of La or Mn non-stoichiometry, the oxygen content y decreases more with La-deficient compositions than with Mn-deficient ones. The La/Mn ratio influences strongly the relationship between [h], [V_O], [V_La^?] and [V_Mn^?].The DFT-GGA (Density functional Theory, Generalized-Gradient Approximation) simulation of these compounds using VASP (Vienna Ab-initio Simulation Package) concludes that the electronic structure for the optimized stoichiometric La₆Mn₆O₁₈ is not optimal, relative to that expected considering Mn(III) ions with four alpha electrons each. The non-stoichiometry is the easiest way of reducing the Jahn–Teller instability by depopulating the half-filled e_g orbitals. A partial oxidation is then stabilizing. Creation of defects, either an O insertion or a cationic vacancy, allows finding an ideal count. In the case of pure cationic defects (missing a La(III) or a Mn(III) cation), the amount of vacancies is one missing cation upon twelve. The compact nature of lanthanum manganite oxide does not allow oxygen insertion within the bulk structure and oxidation can only be achieved at the surface without O penetration. The formation of antisites is endothermic. The creation of mixed vicinal vacancies, one oxygen and one cationic vacancy (La or Mn), is exothermic for a concentration of defects of one defect per twelve cations.     

The role of ligand coordination on the spectral features of Yb3+ ions in lead aluminum silicate glasses

The glasses of the composition (40 ? x)PbO–(5 + x)Al₂O₃–54SiO₂:1.0Yb₂O₃ (in mol%) with x ranging from 5 to 10 have been synthesized. The IR spectral studies of these glasses have indicated that there is a gradual transformation of Al³⁺ ions from tetrahedral to octahedral coordination with increase of Al₂O₃ content in the glass network. The optical absorption and luminescence spectra have exhibited bands originating from ²F_7/2 → ²F_5/2 and ²F_5/2 → ²F_7/2 transitions, respectively. From these spectra, the absorption and emission cross-sections and fluorescence lifetime of Yb³⁺ ions have been evaluated. Quantitative analysis of these data indicated a decreasing radiative trapping and increasing fluorescence lifetime of Yb³⁺ ions with increasing Al₂O₃ content. This may be explained by structural variations in the vicinity of Yb³⁺ ions due to variation in the concentration of Al₂O₃ in the glass network.     

Nd6Li(BO3)3O4F2: A novel neodymium oxyborate fluoride containing two-dimensional Nd layers

Crystal of a new neodymium oxyborate fluoride Nd₆Li(BO₃)₃O₄F₂ was grown by the flux method. Its structure, determined by single crystal x-ray diffraction, belongs to the space group C2/c with cell parameters of a = 12.0629(2) Å, b = 6.94650(10) Å, c = 16.0528(3) Å, β = 104.5360(10)°. In the structure, Nd atoms coordinate to oxygen or fluorine atoms to yeild 7 or 8 coordinated Nd(O,F)n polyhedra. Those polyhedra are edge-shared to form a double layer of (Nd₁₂O₂₃F₄)^14? fluorite blocks. The blocks are linked by oxygen atoms of planar BO₃ groups in the c direction into a 3-dimensional network. Another novel element in the structure is that Li coordinates to 6 oxygen atoms from three BO₃ groups forming a propeller like arrangement, and theoretical calculation shows that such arrangement should give 3/4 that of BO₃ contribution to second harmonic effect. The crystal shows deep violet color with typical Nd³⁺ optical absorption and a UV transmission cut-off of 260 nm.     

Coordination asymmetry in μ-oxido divanadium complexes: Development of synthetic protocols

This brief review deals with the development of a general protocol for the synthesis of μ-oxido divanadium(V) compounds [LOV^V-(μ-O)-V^VO(Salen)] (L = L¹–L⁵) (1–5) incorporating coordination asymmetry. One of the vanadium centers in these compounds has an octahedral environment, completed by tetradentate Salen ligand, while the other center has a square pyramidal geometry, made up of tridentate biprotic Schiff-base ligands (H₂L^1–5) with ONO (1–3) and ONS (4, 5) type donor combinations. Single crystal X-ray diffraction, ESI-MS, and multi-nuclear NMR (¹H and ⁵¹V) spectroscopy have been used extensively for the characterization of these compounds. The V₂O₃ core in these compounds, save 3, has a rare type of twist-angular structure. The V(1)?V(2) separations (3.7921(7)–3.3084(6) Å) are by far the largest in these compounds compared to their peers containing a V₂O₃ core. The molecules retain their unsymmetrical binuclear structures also in solution as established by NMR spectroscopy. The mixed-oxidation compound (ImH)[L⁴OV^IV-(μ-O)-V^VOL⁵] 7 containing two dissimilar ligands has a V₂O₃ core with a syn-angular structure and exhibits crystallographically imposed mirror symmetry due to static disorder. In solution of donor solvents, this angular core structure changes into a linear one (anti-linear) by accepting solvents in to the vacant coordination site of the metal centers. Finally, the protocol for the synthesis of heterobimetallic compounds with vanadium(V) and Re(VII) combination flanked by a single μ-oxido bridge has been developed in which the precursor complexes [V^IVOL^6,7] (H₂L^6,7 are Salen type of ligands) are allowed to oxidize aerially in the presence of added perrhenate anion. The oxidized [V^VOL^6,7]⁺ species hold the ReO₄^? anion in the vacant coordination site of the metal ion, trans to the terminal oxido group, thus generating the V^V–O–Re^VII moiety in the heterobimetallic compounds (9 and 10). Both X-ray crystallography and ¹H NMR spectroscopy have been used to establish the identities of these compounds. In compound 9, the Re(1)–O(11)–V(1) bridge angle is barely linear (170.2(3)°) with a Re?V separation of 3.9647(9) Å. The redox behavior of 9 and 10 are quite interesting, each undergoing two reductions both in the positive potential range at E_1/2 = 0.59 and 0.16 V vs. Ag/AgCl reference and have single-electron stoichiometry, confirmed by constant potential coulometry.     

Crystal structure and ionic conductivity of AgCr2(PO4)(P2O7)

Single crystals of a new phosphate AgCr₂(PO₄)(P₂O₇) have been prepared by the flux method and its structural and the infrared spectrum have been investigated. This compound crystallizes in the monoclinic system with the space group C2/c and the parameters are, a = 11.493 (3) Å, b = 8.486 (3) Å, c = 8.791 (2) Å, β = 114.56 (2)°, V = 779.8 (3) ųand Z = 4. Its structure consists of CrO₆ octahedra sharing corners with P₂O₇ units to form undulating chains extending infinitely along the [110] direction. These chains are connected by the phosphate tetrahedra giving rise to a 3D framework with six-sided tunnels parallel to the [101] direction, where the Ag⁺ ions are located. The infrared spectrum of this compound was interpreted on the basis of P₂O₇^4? and PO₄^3? vibrations. The appearance of ν_sP–O–P in the spectrum suggests a bent P–O–P bridge for the P₂O₇^4? ions in the compound, which is in agreement with the X-ray data. The electrical measurements allow us to obtain the activation energy of (1.36 eV) and the conductivity measurements suggest that the charge carriers through the structure are the silver captions.     

Structural investigation and electron paramagnetic resonance of vanadyl doped alkali niobium borate glasses

Glasses with compositions xNb₂O₅·(30 ? x)M₂O·69B₂O₃ (where M = Li, Na, K; x = 0, 4, 8 mol%) doped with 1 mol% V₂O₅ have been prepared using normal melt quench technique. The IR transmission spectra of the glasses have been studied over the range 400–4000 cm^?1. The changes caused by the addition of Nb₂O₅ on the structure of these glasses have been reported. The electron paramagnetic resonance spectra of VO²⁺ ions in these glasses have been recorded in X-band (9.14 GHz) at room temperature (300 K). The spin Hamiltonian parameters, dipolar hyperfine coupling parameter and Fermi contact interaction parameter have been calculated. It is observed that the resultant resonance spectra contain hyperfine structures (hfs) due to V⁴⁺ ions which exist as VO²⁺ ions in octahedral coordination with a tetragonal compression in the present glasses. The tetragonality of V⁴⁺O₆ complex decreases with increasing concentration of Nb₂O₅. The 3d_xy orbit contracts with increase in Nb₂O₅:M₂O ratio. Values of the theoretical optical basicity, Λ_th, have also been reported.     

Solid state coordination chemistry of the copper(II)/bisterpy/vanadate system: The structures of [Cu2(bisterpy)V4O12]·2H2O and [Cu2(bisterpy)V4F2O11] (bisterpy = 2,2′:4′,4′′:2′′,2′′′-quarter-pyridyl, 6′,6′′-di-2-pyridine)

Hydrothermal methods were exploited in the preparation of bimetallic organic–inorganic hybrid materials of the metal-bisterpy/vanadate class. [Cu₂(bisterpy)V₄O₁₂]·2H₂O exhibits a two-dimensional structure constructed from {Cu₂V₄O₁₂}_n chains linked through bisterpy ligands. The isomorphous materials [M₂(bisterpy)V₄F₂O₁₁] (M = Cu, Zn) are also two-dimensional. In these cases, {M₂V₄F₂O₁₁}_n chains are linked through bisterpy ligands to generate the two-dimensional network.     

Spin dimer analysis of the magnetic structures of A2V3O9 (A = Ba,Sr) and η-Na9V14O35: Importance of the V4+–O⋯O–V4+ super-superexchange interactions mediated by the O–V5+–O bridges

Spin dimer analysis was carried out for the magnetic oxides of V⁴⁺ (d¹) ions, A₂V₃O₉ (A = Ba, Sr) and η-Na₉V₁₄O₃₅, to account for their magnetic structures. After identifying the V(O_eq)₄ square planes containing the magnetic orbitals of the V⁴⁺ (d¹) ions, we analyzed the relative strengths of the various V–O_eq–V and V–O_eq⋯O_eq–V spin exchange interactions. The V–O_eq⋯O_eq–V spin exchange interactions mediated by O_eq–V⁵⁺–O_eq bridges are found to be crucial in determining the magnetic structures of A₂V₃O₉ (A = Ba, Sr) and η-Na₉V₁₄O₃₅. Our analysis suggests that η-Na₉V₁₄O₃₅ should have two different spin gaps.     

A Ca substitution study of NaV2O4: High-pressure synthesis of the Na1−xCaxV2O4 solid solution

Ambient pressure CaV₂O₄ and high-pressure NaV₂O₄ crystallize in the CaFe₂O₄ structure type containing double chains of edge-sharing VO₆ octahedra. Recent measurements on NaV₂O₄ reveal low-dimensional metallicity and evidence of half-metallic ferromagnetism. In contrast, CaV₂O₄ is an antiferromagnetic insulator. To explore the evolution of these ground-state behaviors, we have prepared a series of Ca-doped NaV₂O₄ compounds with the formula Na_1?xCa_xV₂O₄ (x = 0–1) using high-pressure synthesis. Samples at the Na end (x = 0–0.07) show a broad antiferromagnetic transition in the 120–160 K range in accordance with earlier reports. Transport measurements show an insulator–metal transition at x ～ 0.2. Samples with higher Ca concentrations (x = 0.4–0.7) exhibit a metal–insulator transition around 150 K. The results for the Na_1?xCa_xV₂O₄ solid solution is discussed in comparison to existing studies at the Ca- and Na-rich ends.     

On the kinetics of thermal electron attachment to perfluoroethers

In this Letter we report the results of the measurements of the rate coefficients for thermal attachment to several perfluoroethers namely perfluorodiglyme (C₆F₁₄O₃), perfluorotriglyme (C₈F₁₈O₄), perfluoropolyether (CF₃–(OCF(CF₃)CF₂)_n–(OCF₂)_m–OCF₃) and perfluorocrownether ((C₂F₄O)₅). Rate coefficients were obtained under thermal conditions in the temperature range 298–378 K. The increase of the rates with temperature follows the Arrhenius law and the activation energies have been obtained from the slope of the ln(k) vs. 1/T. The respective values of the rate coefficients (at 298 K) and activation energies are as follows: 7.7 ± 1.2 × 10^?11 cm³ s^?1 (0.18 ± 0.005 eV), 6.7 ± 2.1 × 10^?11 cm³ s^?1 (0.25 ± 0.004 eV), 2.1 ± 0.2 × 10^?10 cm³ s^?1 (0.16 ± 0.010 eV), 3.1 × 10^?11 cm³ s^?1 (0.27 ± 0.003 eV) for C₆F₁₄O₃, C₈F₁₈O₄, CF₃–(OCF(CF₃)CF₂)_n–(OCF₂)_m–OCF₃ and (C₂F₄O)₅.     

Comparative study on energetic distortions of SO42− ions matrix-isolated in compounds with kröhnkite-type chains,K2Me(CrO4)2·2H2O and Na2Me(SeO4)2·2H2O (Me = Mg,Co, Ni,Zn, Cd)

Infrared spectra of compounds with kröhnkite-type infinite octahedral–tetrahedral chains, K₂Me(CrO₄)₂·2H₂O and Na₂Me(SeO₄)₂·2H₂O (Me = Mg, Co, Ni, Zn, Cd), as well as infrared spectra of the title double salts containing matrix-isolated SO₄^2? guest ions are presented and discussed in the regions of the X–O stretching modes.The SO₄^2? guest ions matrix-isolated in selenate and chromate matrices exhibit four infrared bands corresponding to the four site-group components of the stretching modes in good agreement with the low site symmetry of the host ions (C₁ site symmetry). The values of Δν₃ (site-group splitting) and Δν_max (the difference between the highest and the lowest wavenumbered components of the stretching modes) are used as an adequate measure for the extent of energetic distortion of the matrix-isolated SO₄^2? guest ions.The influence of different crystal-chemical parameters (Me²⁺–OXO₃ bond strengths, sizes of the Me²⁺ and Me⁺ ions, electronic configurations of the Me²⁺ ions, hydrogen bond strengths, and unit-cell volumes of the host compounds) on the extent of energetic distortion of both the host SeO₄^2? and CrO₄^2? ions, and the SO₄^2? guest ions is analyzed. Correlations between the values of Δν₃ and Δν_max of the guest ions and both the degree of covalency of the respective Me²⁺–OXO₃ bonds and the electronic configurations of the Me²⁺ ions have been found and will be discussed. For example, the energetic distortion of SO₄^2? ions included in the chromate lattices decreases in the order Zn > Cd > Mg as a result of the decreasing covalency of the respective Me²⁺–O bonds in the same order (Δν₃ have values of 73, 58 and 36 cm^?1, respectively). Furthermore, the values of Δν₃ and Δν_max are larger when the metal ions have CFSE ≠ 0 (crystal field stabilization energy, Co²⁺, Ni²⁺). These cations are more resistant to angular deformations of the MeO₆ octahedra (i.e. changes in the O–Me–O bond angles), thus facilitating the extent of distortion of the matrix-isolated SO₄^2? ions as compared to those having CFSE = 0 (Mg²⁺, Zn²⁺ and Cd²⁺). For example, Δν₃ and Δν_max of SO₄^2? ions matrix-isolated in K₂Zn(CrO₄)₂·2H₂O have values of 73 and 163 cm^?1, and 116 and 207 cm^?1 in Na₂Zn(SeO₄)₂·2H₂O, whereas in the respective nickel lattices Δν₃ and Δν_max have values of 88 and 173 cm^?1 (K₂Ni(CrO₄)₂·2H₂O) and 127 and 212 cm^?1 (Na₂Ni(SeO₄)₂·2H₂O).The SO₄^2? guest ions included in selenate matrices, Na₂Me(SeO₄)₂·2H₂O, are remarkably much distorted than in chromate ones, K₂Me(CrO₄)₂·2H₂O, as deduced from the values of Δν₃ and Δν_max owing to a stronger static field caused by the smaller Na⁺ ions as compared to that caused by the larger K⁺ ions. The smaller unit-cell volumes of the selenate host compounds, i.e. the higher repulsion potential at the lattice sites at which the guest ions are situated additionally favor the extent of energetic distortion of the sulfate guest ions in the selenate matrices.     

Dielectric characteristics of a Ce3+-doped Sr0.61Ba0.39Nb2O6 single crystal with Cole–Cole plots technique

In this paper, we have investigated relaxation mechanisms and dielectric characteristics of an Sr_0.61−xBa_0.39Nb₂O₆Ce_x (abbreviated as SBN61 and x=0.0066) single crystal with dielectric spectroscopy measurements. The crystal undergoes a ferroelectric phase transition at 340 K. The temperature dependence of the real and imaginary part of the complex dielectric susceptibility in the vicinity of ferroelectric–paraelectric phase transition has been studied in the frequency region 100 Hz–10 mHz. The measurement of the dielectric constants of the real and imaginary parts shows strong frequency dependence. The investigations of the dielectric constant using Cole–Cole plots revealed a non-Debye-type dielectric relaxation for Ce⁺³-doped SBN61. It reveals the coexistence of the two dielectric relaxators in the vicinity of the phase transition.     

Kinetics and mechanism of the chromic oxidation of 3-O-methyl-d-glucopyranose

The oxidation of 3-O-methyl-d-glucopyranose (Glc3Me) by Cr^VI in acid medium yields Cr^III, formic acid and 2-O-methyl-d-arabinose as final products when a 50-times or higher excess of Glc3Me over Cr^VI is used. The redox reaction takes place through the combination of Cr^VI → Cr^IV → Cr^II and Cr^VI → Cr^IV → Cr^III pathways. Intermediacy of free radicals and Cr^II in the reaction was demonstrated by the observation of induced polymerization of acrylamide and detection of CrO₂²⁺ formed by reaction of Cr^II with O₂. Intermediate oxo-Cr^V–Glc3Me species were detected by EPR spectroscopy. In 0.3–0.5 mol/L HClO₄, intermediate Cr^V rapidly decompose to the reaction products, while, at pH 5.5–7.5, where the redox processes are very slow, five-coordinate Cr^V bis-chelates of the pyranose and furanose forms of Glc3Me remain more than 15 h in solution. The C1–C2 bond cleavage of Glc3Me upon reaction with Cr^VI distinguishes this derivative from glucose, which is oxidized to gluconic acid.     

Structural and magnetic properties of metal telluromolybdates MxM′1−xTeMoO6 (M,M′ = Mn,Co, Cd)

Synthesis, crystal structures and magnetic properties of metal telluromolybdates M_xM′_1?xTeMoO₆ (M, M′ = Mn, Co, Cd) have been investigated. Their crystal structures have two-dimensional arrays of M and M′ atoms. From the powder X-ray diffraction measurements, Mn_xCo_1?xTeMoO₆ adopt an orthorhombic structure throughout the composition range (x = 0.0–1.0). On the other hand, Mn_xCd_1?xTeMoO₆ and Co_xCd_1?xTeMoO₆ adopt two types of structures corresponding to their end members (orthorhombic for Mn- or Co-rich solid solutions; tetragonal for Cd-rich ones). In the intermediate compositions, it was found that two phases coexist with different metal components. Magnetic properties of these solid solutions were investigated. All the Mn_xCo_1?xTeMoO₆ exhibits an antiferromagnetic transition at ～23 K. The antiferromagnetic transition was also observed in Mn_xCd_1?xTeMoO₆ and Co_xCd_1?xTeMoO₆. However, the Néel temperature rapidly decreases with increasing the concentration of Cd and disappeared below x = 0.6, which is characteristic for two-dimensional magnetic system.     

Synthesis,crystal structure and electrical characterization of Cs4[(UO2)2(V2O7)O2], a uranyl divanadate with chains of corner-sharing uranyl square bipyramids

A new cesium uranyl vanadate Cs₄[(UO₂)₂(V₂O₇)O₂] has been synthesized by solid-state reaction and its structure determined from single-crystal X-ray diffraction data. It crystallizes in the orthorhombic symmetry with space group Pmmn and following cell parameters: a=8.4828(15) Å, b=13.426(2) Å and c=7.1366(13) Å, V=812.8(3) Å³, Z=2 with ρ_mes=5.39(2) g/cm³ and ρ_cal=5.38(1) g/cm³. A full-matrix least-squares refinement on the basis of F² yielded R₁=0.027 and wR₂=0.066 for 62 parameters with 636 independent reflections with I⩾2σ(I) collected on a BRUKER AXS diffractometer with MoKα radiation and a charge-coupled device detector. The crystal structure is characterized by _∞²[(UO₂)₂(V₂O₇)O₂]⁴⁻ corrugated layers parallel to (001). The layers are built up from distorted (UO₂)O₄ octahedra and divanadate V₂O₇ units resulting from two VO₄ tetrahedra sharing corner. The distorted uranyl octahedra (UO₂)O₄ are linked by corners to form infinite _∞¹[UO₅]⁴⁻ chains parallel to the a-axis. These chains are linked together by symmetrical divanadate units sharing two corners with each chain, the two last corners being oriented towards the same interlayer. The cohesion of the structure is assured by interlayer Cs⁺ ions. Their mobility within the interlayer space gives rise to a cationic conductivity with an important jump between 635°C and 680°C. Cs₄[(UO₂)₂(V₂O₇)O₂] is readily decomposed by water at 60°C to form the Cs-carnotite analog Cs₂(UO₂)₂(V₂O₈) compound.     

Impact of Fe3+ on UV absorption of K2Al2B2O7 crystals

K₂Al₂B₂O₇ (KABO) is a new nonlinear optical crystal capable of laser harmonic generation in the UV range. However, abnormal UV absorption prevents its application in effectively generating UV light with wavelength shorter than 300 nm. The transmittance spectra of the grown crystals show distinct absorption bands at 216 nm and 264 nm. It is observed that the UV absorption is strongly correlated with iron impurity at a parts per million (ppm) level. Furthermore, electron paramagnetic resonance (EPR) spectra of the absorbing crystals show a strong signal at g = 2.00 position corresponding to a Fe³⁺ center. A new crystal growth method which reduces the iron content has been proposed and results show that the new KABO crystal is free from the Fe³⁺ UV absorptions.     

LixV2O5 nanobelts for high capacity lithium-ion battery cathodes

5–10 μm long, typically 200–300 nm wide, and several nanometers thick Li_xV₂O₅ (× ～ 0.8) nanobelts with the δ-type crystal structure were synthesized by a hydrothermal treatment of Li⁺-exchanged V₂O₅ gel. When dried at 200 °C under vacuum prior to electrochemical testing, the as-prepared nanobelts underwent the well-known δ → ε → γ-phase transition giving a mixture of ε and γ phases as a nanocomposite electrode material. Such a simple preparation procedure guarantees a yield of material with drastically enhanced initial discharge specific capacity of 490 mAh/g and great cyclability. The enhanced electrochemical performance is attributed to the complex of experimental procedures including post-synthesis treatment of the single-crystalline Li_xV₂O₅ nanobelts.