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Sodium-vanadium bronze Na9V14O35: An electrode material for na-ion batteries
Na9V14O35 (η-NaxV2O5) has been synthesized via solid-state reaction in an evacuated sealed silica ampoule and tested as electroactive material for Na-ion batteries. According to powder X-ray diffraction, electron diffraction and atomic resolution scanning transmission electron microscopy, Na9V14O35 adopts a monoclinic structure consisting of layers of corner-and edge-sharing VO5 tetragonal pyramids and VO4 tetrahedra with Na cations positioned between the layers, and can be considered as sodium vanadium(IV,V) oxovanadate Na9V104.1+O19 (V5+O4)4. Behavior of Na9V14O35 as a positive and negative electrode in Na half-cells was investigated by galvanostatic cycling against metallic Na, synchrotron powder X-ray diffraction and electron energy loss spectroscopy. Being charged to 4.6 V vs. Na+/Na, almost 3 Na can be extracted per Na9V14O35 formula, resulting in electrochemical capacity of ~60 mAh g?1. Upon discharge below 1 V, Na9V14O35 uptakes sodium up to Na:V = 1:1 ratio that is accompanied by drastic elongation of the separation between the layers of the VO4 tetrahedra and VO5 tetragonal pyramids and volume increase of about 31%. Below 0.25 V, the ordered layered Na9V14O35 structure transforms into a rock-salt type disordered structure and ultimately into amorphous products of a conversion reaction at 0.1 V. The discharge capacity of 490 mAh g?1 delivered at first cycle due to the conversion reaction fades with the number of charge-discharge cycles.
Abakumov, Artem M.,Akmaev, Alexey S.,Gorbunov, Mikhail V.,Kirsanova, Maria A.,Mikhailova, Daria
(2021/12/29)

High-performance NaVO3 with mixed cationic and anionic redox reactions for Na-ion battery applications
Sodium-ion batteries (NIBs) are a potential low-cost alternative to lithium-ion batteries for large-scale energy storage, but many high-capacity NIB cathode materials undergo irreversible structural changes during charge and discharge, leading to fast capacity fading. Herein, monoclinic NaVO3 exhibits good cycle performance with high capacity as a cathode material for NIBs. In situ synchrotron X-ray diffraction studies show that the material structure is virtually invariant during Na+ (de)intercalation, with the a and b lattice parameters changing only by 0.13 and 0.19%, respectively. The material undergoes an oxygen redox reaction during initial charge while delivering a remarkable specific capacity of 245 mAh g-1 (1.2-4.7 V) with contributions from cationic (V4+/V5+) and anionic (O2-/O-) redox couples during discharge. The stable VO4 tetrahedral framework also enables the material to give superior rate and cycle capabilities, with a capacity of 164 mAh g-1 (67% utilization) at a current of 1000 mA g-1 (about 5C) and a capacity retention of 90% after 50 cycles. Density functional theory calculations further verify the stability of the material and the charge-discharge mechanism. This work can broaden the horizon for designing high-energy cathode materials with enhanced structural stability for sodium-ion batteries.
Su, Bizhe,Wu, Shuilin,Liang, Hanqin,Zhou, Wenchong,Liu, Junnan,Goonetilleke, Damian,Sharma, Neeraj,Sit, Patrick H.-L.,Zhang, Wenjun,Yu, Denis Y.W.
p. 8836 - 8844
(2020/11/24)

Synthesis, Characterization, and Photocatalytic Activities of BiVO4 by Carbon Adsorption Hydrothermal Method
A new idea of prepared method for BiVO4 nano-powders hydrothermal synthesis process was developed to avert the existent shortcomings of hydrothermal method. The thermal stability, phase structure, light absorption property, and morphology of the catalyst prepared were characterized by thermogravimetric analyzer (TG), X-ray diffraction (XRD), ultraviolet visible spectrophotometer (UV/Vis), and transmission electron microscopy (TEM), respectively. Using methyl orange (MO) as the target degradation material and a 500-W dysprosium lamp as the visible light source to investigate photocatalytic performance of BiVO4. We successfully prepared BiVO4 powders with small particle size, less agglomeration and uniform distribution by carbon adsorption hydrothermal method, and the absorption wavelength of light was red-shifted, these all rendered the absorption capacity of visible light region enhancing with 94 % high photocatalytic degradation rate of methyl orange at 60 min. And the possible mechanism was also discussed in this study.
Niu,Guo
p. 1661 - 1665
(2020/08/19)

Stability of Polar Structure in Filling-Controlled Giant Tetragonal Perovskite Oxide PbVO3
The crystal structure and stability of a giant tetragonal phase in electron-doped Pb1-xBixVO3 (x = 0.1, 0.2, and 0.3) and hole-doped Pb1-xNaxVO3 (x = 0.1, 0.2, and 0.3) were studied. Electron doping effectively destabilized the tetragonal structure. The c/a ratio, spontaneous polarization, and tetragonal-to-cubic phase transition pressure systematically decreased with increasing Bi3+ substitution. In contrast, hole doping hardly affected the tetragonal distortion and structural stability. We showed that electron doping is an effective way to control the stability of the tetragonal phase of PbVO3 with a 3d1 electronic configuration.
Yamamoto, Hajime,Ogata, Takahiro,Sakai, Yuki,Azuma, Masaki
p. 2755 - 2760
(2019/02/19)

Tailoring NaVO3 as a novel stable cathode for lithium rechargeable batteries
Vanadium-based compounds hold great promise as high capacity cathode candidate for future lithium rechargeable batteries. However, developing highly stable vanadium-based cathode materials with long cycle life remains a great challenge. Herein, we report a novel layered sodium vanadium oxide, NaVO3, as a promising cathode electrode contender. This material is capable of delivering a capacity of 224.8 mAh g?1 at the current density of 150 mA g?1, and a high rate capability of 85 mAh g?1 even at a high current density of 3 A g?1. Moreover, outstanding capacity retention of 77% after 1000 cycles is achieved. Ex situ characterizations verify that the excellent electrochemical performance of NaVO3 is attributed to superior structural stability and electrochemical reversibility upon long-term cycling. Furthermore, the lithium ion de/intercalation mechanism for NaVO3 is also revealed involving one electron transfer reaction between V5+ and V4+ redox couple. Considering the low cost and material sustainability as well as the outstanding electrochemical performances, we believe that NaVO3 is a highly promising cathode material for lithium rechargeable batteries and our findings may help to pave the way for developing vanadium-based layered structure materials for high-performance alkali and alkaline-earth ion batteries.
Chen, Long,Wu, Honglun,Wang, Huiming,Chen, Liang,Pu, Xiangjun,Chen, Zhongxue
p. 224 - 231
(2019/04/17)

Na1/2Bi1/2VO3 and K1/2Bi1/2VO3: New Lead-Free Tetragonal Perovskites with Moderate c/ a Ratios
New lead-free tetragonal perovskites Na1/2Bi1/2VO3 and K1/2Bi1/2VO3 were synthesized under high pressure (6 GPa) and high temperature (1473 K), based on the design of materials optimizing the lone pair effect of the A-site ion and utilizing the Jahn-Teller effect in the B-site V4+. The magnitudes of the c/a ratio and spontaneous polarization, PS, were 1.085 and 108 μC/cm2, respectively (73 μC/cm2 by the point charge model), for Na1/2Bi1/2VO3 and 1.054 and 92 μC/cm2, respectively (56 μC/cm2 by the point charge model), for K1/2Bi1/2VO3, which are comparable to the well-known lead-based ferroelectric PbTiO3. This approach can guide the design of new lead-free ferroelectric and piezoelectric materials.
Yamamoto, Hajime,Ogata, Takahiro,Patel, Satyanarayan,Koruza, Jurij,R?del, Jürgen,Paul, Atanu,Saha-Dasgupta, Tanusri,Sakai, Yuki,Itoh, Mitsuru,Azuma, Masaki
p. 6728 - 6736
(2018/10/02)

Vanadium(v) oxoanions in basic water solution: A simple oxidative system for the one pot selective conversion of l-proline to pyrroline-2-carboxylate
The unprecedented, direct chemical oxidation of l-proline to pyrroline-2-carboxylate was achieved in water (pH 9-10) by means of NH4VO3/NH3 or V2O5/MOH (K = Na, K), and the anion was fully characterized as ammonium or alkaline metal salts. Quantitative yield and higher atom economy performance were achieved with the latter system, the alkaline salts being more stable than the ammonium one. Different mixed valence V(iv)/V(v) compounds precipitated from the reaction mixtures depending on the nature of the employed base. A possible reaction mechanism is proposed according to DFT calculations. The analogous reaction of trans-4-hydroxy-l-proline with NH4VO3/NH3 afforded pyrrole-2-carboxylic acid in 81% yield, while sarcosine underwent prevalent decomposition under similar experimental conditions. Instead, no reaction was observed with primary (glycine, l-alanine, l-phenylalanine) and tertiary α-amino acids (N,N-dimethyl-l-phenylalanine, N,N-dimethylglycine).
Biancalana, Lorenzo,Tuci, Giada,Piccinelli, Fabio,Marchetti, Fabio,Bortoluzzi, Marco,Pampaloni, Guido
p. 15059 - 15069
(2017/11/14)

Bovine serum albumin binding, antioxidant and anticancer properties of an oxidovanadium(IV) complex with luteolin
Chemotherapy using metal coordination compounds for cancer treatment is the work of the ongoing research. Continuing our research on the improvement of the anticancer activity of natural flavonoids by metal complexation, a coordination compound of the natural antioxidant flavone luteolin (lut) and the oxidovanadium(IV) cation has been synthesized and characterized. Using different physicochemical measurements some structural aspects of [VO(lut)(H2O)2]Na·3H2O (VOlut) were determined. The metal coordinated to two cis-deprotonated oxygen atoms (ArO-) of the ligand and two H2O molecules. Magnetic measurements in solid state indicated the presence of an effective exchange pathway between adjacent vanadium ions. VOlut improved the antioxidant capacity of luteolin only against hydroxyl radical. The antitumoral effects were evaluated on MDAMB231 breast cancer and A549 lung cancer cell lines. VOlut exhibited higher viability inhibition (IC50 = 17 μM) than the ligand on MDAMB231 cells but they have the same behavior on A549 cells (ca. IC50 = 60 μM). At least oxidative stress processes were active during cancer cell-killing. When metals chelated through the carbonyl group and one adjacent OH group of the flavonoid an effective improvement of the biological properties has been observed. In VOlut the different coordination may be the cause of the small improvement of some of the tested properties of the flavonoid. Luteolin and VOlut could be distributed and transported in vivo. Luteolin interacted in the microenvironment of the tryptophan group of the serum binding protein, BSA, by means of electrostatic forces and its complex bind the protein by H bonding and van der Waals interactions.
Naso, Luciana G.,Lezama, Luis,Valcarcel, María,Salado, Clarisa,Villacé, Patricia,Kortazar, Danel,Ferrer, Evelina G.,Williams, Patricia A.M.
p. 80 - 93
(2016/02/05)

Multi-component synthesis of highly substituted imidazoles catalyzed by nanorod vanadatesulfuric acid
Nanorod vanadatesulfuric acid (VSA NRs), as a recyclable and eco-benign catalyst, was used for one-pot synthesis of 2,4,5-trisubstituted imidazoles and 1,2,4,5-tetrasubstituted imidazoles using aldehydes, benzil, benzoin or 9,10-phenanthrenequinone and ammonium acetate or aniline under solvent-free conditions providing high to excellent yields. VSA is easily prepared by a simple reaction of chlorosulfonic acid and sodium metavanadate in high purity. As compared with the conventional procedures, the present protocol offers several advantages such as simplicity of procedure, short reaction time, high yields, easy workup, recoverability and reusability of the catalyst and simple purification of the products.
Nasr-Esfahani, Masoud,Montazerozohori, Morteza,Abdizadeh, Tooba
p. 1491 - 1499
(2015/09/15)

Amorphous sodium vanadate Na1.5 + yVO3, a promising matrix for reversible sodium intercalation
Sodium insertion into the vanadate NaVO3 shows the formation of an amorphous phase with the composition Na1.5 + yVO3. The latter phase exhibits reversible electrochemical sodium intercalation/de- intercalation properties through a solid solution-like process, for 0 +/Na and a capacity of 150 mAh/g. This result opens the route to the investigation of amorphous matrices involving transition metal oxides for sodium ion battery applications.
Venkatesh,Pralong,Lebedev,Caignaert,Bazin,Raveau
p. 100 - 102
(2014/02/14)

Chemical sodiation of V2O5by Na2S
Chemical sodiation of V2O5 at low temperatures allows to synthesize NaxV2O5 with 0≤ x≤ 1, while classic high temperature syntheses yield in either x≤ 0.02 (α-phase) or 0.7≤ x (α′-phase), or other phases (β-phase, δ-phase) or mixtures thereof. A suspension of V2O5 in acetonitrile and Na2S as sodiation agent were used. The maximum amount of sodiation was obtained by using an excess of Na2S, refluxing the acetonitrile during the reaction, and precedent ball milling of the V2O5. If only low amounts of Na2S were used as starting material, a mixture of fractions of NaxV2O5with different values of x was obtained. All these fractions belong to the α- or α′-phase, space group Pmmn.
Haberkorn, Robert,Bauer, Jessica,Kickelbick, Guido
p. 3197 - 3202
(2015/02/19)

Preparation, characterization and use of vanadatesulfuric acid as a new and eco-benign nanocatalyst for the synthesis of 14-aryl-14h-dibenzo[a,j] xanthenes under solvent-free conditions
Vanadatesulfuric acid (VSA) is a recyclable and eco-benign catalyst for the preparation of biologically active 14-aryl-14-H-dibenzo [a,j]xanthenes by a one-pot condensation reaction of 2-naphthol and aldehydes under solvent-free conditions in high to exce
Nasr-Esfahani, Masoud,Abdizadeh, Tooba
p. 27 - 35
(2014/01/06)

Vanadatesulfuric acid-catalyzed novel and eco-benign one-pot synthesis of polyhydroquinoline derivatives under solvent-free conditions
A novel and green approach for efficient and rapid synthesis of biologically active polyhydroquinoline derivatives via unsymmetric Hantzsch reaction using Vanadatesulfuric acid (VSA) as a new and recyclable catalyst under solvent-free conditions was repor
Nasr-Esfahani, Masoud,Abdizadeh, Tooba
p. 1249 - 1258
(2013/02/23)

XPS study of nanorods of doped vanadium oxide M x V 2O5 ? nH2O (M = Na, K, Rb, Cs)
Nanorods of vanadium oxide doped with alkali metal ions M x V2O5 ? nH2O (M = Na, K, Rb, Cs, x = 0.31-0.44) have been obtained under hydrothermal conditions. The particles are 30-80 nm in diameter and a few micro
Zakharova,Podval'Naya,Kuznetsov
p. 267 - 272
(2011/06/20)

Effect of alkali metal ion and hydrogen bonds on thermal stability of M[VO(O2)2bpy]·nH2O (M = Li +-Rb+) and Cs[VO(O2)2bpy] ·H2O2 complexes
The compounds M[VO(O2)2bpy]·nH2O (M = Li+-Rb+) and Cs[VO(O2)2bpy] ·H2O2 were characterized by thermogravimetry (TG). In the course of TG experiments, performed from 25 up to 550 °C, three main stages of decomposition were observed: (i) dehydration, (ii) releasing of the oxygen molecules and (iii) decomposition of bpy. The final product of decomposition is MVO3, with small amounts of paramagnetic vanadium(IV) species. Volatile products were detected on-line using mass spectrometer. Mechanism of the decomposition is discussed on the basis of crystal structures of complexes. The main role is played by hydrogen bonds involving peroxo ligands and polarising power of alkali metal ions.
Przybylski, Wojciech,Grybo?, Ryszard,Majda, Dorota,Szklarzewicz, Janusz T.
p. 32 - 36
(2011/03/21)

Synthesis and characterization of the crystal structure and magnetic properties of the ternary manganese vanadate NaMnVO4
A new ternary manganese vanadate, NaMnVO4, was synthesized by solid state reaction route, and its crystal structure and magnetic properties were characterized by X-ray diffraction, magnetic susceptibility and specific heat measurements, and by density functional calculations. NaMnVO4 crystallizes in the maricite-type structure with space group Pnma, a = 9.563(1) A, b = 6.882(1) A, c = 5.316(1) A, and Z = 4. NaMnVO 4 contains MnO4 chains made up of edge-sharing MnO 6 octahedra, and these chains are interlinked by VO4 tetrahedra. The magnetic susceptibility has a broad maximum at Tmax = 24 K and follows the Curie-Weiss behavior above 70 K with θ = -62 K. NaMnVO4 undergoes a three-dimensional antiferromagnetic ordering at TN = 11.8 K. The spin exchanges of NaMnVO4 are dominated by the intrachain antiferromagnetic exchange, and the interchain spin exchanges are spin-frustrated. The most probable magnetic structure of the ordered magnetic state below TN was predicted on the basis of the extracted spin exchanges.
Ben Yahia, Hamdi,Gaudin, Etienne,Boulahya, Khalid,Darriet, Jacques,Son, Won-Joon,Whangbo, Myung-Hwan
p. 8578 - 8582
(2011/01/11)

Synthesis and physicochemical study of M4Na2V 10O28 · 10H2O (M = K, Rb, NH 4)
The formation conditions and physicochemical properties of binary decavanadates M4Na2V10O28 · 10H2O (M = K, Rb, NH4), synthesized by crystallization from saturated solutions of the NaVOsub
Krasil'nikov,Shtin,Perelyaeva,Baklanova,Tyutyunnik,Zubkov
p. 162 - 166
(2010/06/18)

The initial rate of solid-phase reaction and composition of the reaction product
Dependence of initial reaction rate on the initial composition of reaction mixture in the systems of Na2CO3-V2O 5, Na2CO3-Fe2O3, and Na2CO3-AgCl
Povarov,Sokolova
p. 2081 - 2086
(2010/02/16)

Investigation of the new P′3-Na0.60VO2 phase: Structural and physical properties
A new layered phase Na0.60VO2 was synthesized by chemical deintercalation of sodium from the pristine compound O3-NaVO 2. The Na0.60VO2 compound exhibits a distorted P′3;type oxygen stacking (AABBCC)
Szajwaj, Olivier,Gaudin, Etienne,Weill, Francois,Darriet, Jacques,Delmas, Claude
p. 9147 - 9154
(2009/12/25)

Phase equilibria in the V2O5-NaVO3- Ca(VO3)2-Mn2V2O7 system and interactions of phases with H2SO4 and NaOH solutions
Phase composition of the V2O5-NaVO 3-Ca(VO3)2-Mn2V2O 7 system was studied, and a subsolidus phase diagram constructed. The tetrahedration of the diagram is determined by the fact that the end-member of Ca1-x Mn x (VO3)2 solid solution is in equilibrium with all compounds of the system (V2O5, NaVO3, Ca(VO3)2), vanadium β-bronzes Na x V2O5 (0.22 ≤ x ≤ 0.40) and κ-bronzes (0.25 ≤ x ≤ 0.45, 0 ≤ y ≤ 0.16), Mn 2V2O7, and Na2Mn3(V 2O7)2 and with the end-members of reciprocal solid solutions based on calcium and sodium metavanadates. At 20°C, the degree of vanadium dissolution α for Na2Ca(VO3) 4 is 100% for 0.5 ≤ pH ≤ 10; for the other phases of the system, vanadium dissolution ranges from 100 to 10% for pH below 3.5; in the alkaline pH range, ≤ 10%. Sodium for calcium substitution in Ca(VO 3)2 increases α in aqueous NaOH to 20%. For Na 2Mn3(V2O7)2, α decreases from 92 to 80% as pH changes from 0.5 to 2.5; at pH above 4, α = 30%.
Krasnenko,Sirina,Rotermel'
p. 1489 - 1494
(2009/04/25)

Synthesis of sodium vanadate nanosized materials for electrochemical applications
Sodium vanadate nanomaterials with the shape of belts and flakes were prepared by simply controlling the pH from the alkaline solution of V2O5. Nanostructured materials have grown from the sol evaporated from the pH-controlled soluti
Subba Reddy,Yeo, In-Hyeong,Mho, Sun-il
p. 1261 - 1264
(2009/01/31)

High pressure behavior of α-NaVO3: A Raman scattering study
The reported pressure-induced amorphization in α-NaVO3 has been re-investigated using Raman spectroscopy. Discontinuous changes are noted in the Raman spectrum above 5.6 GPa implying large structural changes across the transition. The decrease in frequency of the V-O stretching mode across the transition suggests that the vanadium atom may be in octahedral coordination in the high pressure phase. Excessive broadening of the internal modes is observed above 6 GPa. New peaks characteristic of a crystalline phase gain in intensity at higher pressures in the bending modes region; however, the transformation is not complete even at 13 GPa. Co-existence of phases is noted over a significant pressure range above the onset of transition. Pressure released spectrum is found to be a mixture of crystalline α-phase, traces of crystalline β-phase and highly disordered phase consisting of V-O units in five- and six-fold coordination.
Rao, Rekha,Sakuntala,Shaikh,Deb
p. 2824 - 2829
(2008/10/09)

Synthesis and study of sodium vanadomanganate
Sodium 13-vanadomanganate Na7[MnV13O 38]?5H2O (I) has been synthesized and studied by mass spectrometry, thermogravimetry, IR spectroscopy, and X-ray powder diffraction analysis. The crystals of compound I are monoclinic: a = 11.487 ?, b = 7.613 ?, c = 11.359 ?, β = 114.15°, V = 906.52 ?3, ρcalcd = 2.73 g/cm3, Z = 1.
Kaziev,Oreshkina,Holguin Quinones,Glazunova,Alekseev,Cruz Fernandez
p. 1864 - 1867
(2008/10/09)

High-pressure synthesis, crystal structures, and characterization of CdVO3-δ and solid solutions CdVO3-NaVO3
CdVO3-δ and solid solutions of Cd1-xNaxVO3 with the GdFeO3-type perovskite structure were prepared using a high-pressure (6 GPa) and high-temperature technique. No significant oxygen and cation deficiency was found in CdVO3. Cd1-xNaxVO3 are formed in the compositional range of 0 {less-than or slanted equal to} x {less-than or slanted equal to} 0.2. CdVO3 and Cd1-xNaxVO3 demonstrate metallic conductivity and Pauli paramagnetism between 2 and 300 K. A large electronic contribution to the specific heat ( γ = 13.4 and 11.2 mJ / ( mol K2) for CdVO3 and Cd0.8Na0.2VO3, respectively) was observed at low temperatures due to the strongly correlated electrons. Crystal structures of CdVO3 and Cd0.8Na0.2VO3 were refined by X-ray powder diffraction: space group Pnma; Z = 4; a = 5.33435 ( 7 ) A, b = 7.52320 ( 9 ) A, and c = 5.26394 ( 6 ) A for CdVO3 and a = 5.32056 ( 9 ) A, b = 7.50289 ( 13 ) A, and c = 5.25902 ( 8 ) A for Cd0.8Na0.2VO3.
Belik, Alexei A.,Takayama-Muromachi, Eiji
p. 1650 - 1658
(2008/10/09)

Rapid synthesis of size-controllable YVO4 nanoparticles by microwave irradiation
Sized-controlled YVO4 nanoparticles have been synthesized by a simple microwave irradiation processing. The products were characterized by X-ray diffraction, transmission electron microscopy, and ultraviolet-visible spectroscopy. The results showed that the size of as-synthesized YVO4 powders was in the range of 5-18 nm and was extremely dependent on the solution pH value. The optical measurements displayed the obvious quantum-size effect of the products.
Xu, HaiYan,Wang, Hao,Meng, YongQiang,Yan, Hui
p. 465 - 468
(2008/10/09)

KVTeO5 and a redetermination of the Na homologue
A single crystal of KVTeO5, potassium vanadium tellurite, was grown and a redetermination of the Na homologue was presented. The structure was determined with the refinement of the NaVTeO5 homologue, sodium vanadium tellurite. The network consisted of [VTeO5]n ribbons built up by VO4 tetrahedra linking centrosymmetric Te2O6 groups and stacked along the [010] direction. Results showed that the TeIV atom exhibited a typical onesided coordination number (CN) of 4.
Rozier, Patrick,Vendier, Laure,Galy, Jean
p. i111-i113
(2007/10/03)

Process for the preparation of amine oxides
The present invention provides a process for the preparation of high quality amine oxide by reacting a tertiary or secondary amine with hydrogen peroxide as an oxidant in presence of a recyclable heterogeneous layered double hydroxide exchanged with one of the anions of transition metal oxides as a catalyst in a solvent selected from the group consisting of water, water containing dodecylbenzenesulfonic acid sodium salt as additive, and a water miscible organic solvent.
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(2008/06/13)

Process for the preparation of amine oxides
The present invention provides a process for the preparation of high quality amine oxide by reacting a tertiary or secondary amine with hydrogen peroxide as an oxidant in presence of a recyclable heterogeneous layered double hydroxide exchanged with one of the anions of transition metal oxides as a catalyst in a solvent selected from the group consisting of water, water containing dodecylbenzenesulfonic acid sodium salt as additive, and a water miscible organic solvent.
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(2008/06/13)

Charge order and quasi-one-dimensional behavior in β(β′)-AxV2O5
Quasi-one-dimensional conductor β(β′)-AxV2O5 (A=Li, Na, Ag, Ca, Sr, Cu) was investigated for its electric and magnetic properties. The β-A0.33V2O5 (A=Li, Na, Ag, Ca, Sr) phases show a phase transition accompanied by a charge separation and a charge order. The low temperature phase of β-A0.33+V2O5 shows a long-range magnetic order at lower temperature whereas β-A0.332+V2O5 shows a formation of spin gap without any magnetic order. The magnetic properties of the low temperature phases strongly suggest a linear chain for β-A0.33+V2O5 and a two-leg ladder chain for β-A0.332+V2O5 as a charge ordered pattern of magnetic V4+ ions. A quasi-one-dimensional conductor β′-Cu0.65V2O5 shows a superconducting transition under high pressure around 4 GPa at 5 K.
Ueda, Yutaka,Yamada, Hiroyuki,Isobe, Masahiko,Yamauchi, Toru
p. 109 - 114
(2008/10/08)

Process for the preparation of amine oxides
A process for the preparation of high quality amine oxides by reacting a tertiary or secondary amine with hydrogen peroxide as an oxidant in the presence of a recyclable heterogeneous layered double hydroxide exchanged with one of the anions of transition metal oxides as a catalyst in an organic solvent at a temperature ranging between 10-25° C. for a period of 1-6 hours under continuous stirring and separating the product by simple filtration and subsequently evaporation of solvents by known methods.
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(2008/06/13)

Synthesis of polyoxovanadates from aqueous solutions
Polyoxovanadates have been synthesized from aqueous solutions of Vv in the presence of inorganic Na+ and organic [N(CH3)4]+ cations. Decavanadate crystals are precipitated at room temperature around pH 7, whereas layered compounds Na[V3O8].H2O and N(CH3)4[V4O10] are formed at the same pH under hydrothermal conditions: In situ 51V NMR experiments show that upon heating solute decavanadate species are progressively transformed into cyclic metavanadates [V4O12]4-. A chemical mechanism is suggested for the formation of these layered vanadium oxides. It involves the ring-opening polymerization of cyclic metavanadates arising from co-ordination expansion favored by protonation or vanadium reduction.
Bouhedja,Steunou,Maquet,Livage
p. 315 - 321
(2008/10/08)

Multicomponent polyanions, 49: A potentiometric and (31P, 51V) NMR study of the aqueous molybdovanadophosphate system
The equilibrium speciation of the quaternary system H+/MoO42- /HVO42-/HPO42- in aqueous 0.600 M Na(Cl) at 25 °C and 90 °C was studied by pH potentiometry and 31P (202.5 MHz) and 51V (131.6 MHz) NMR spectrometry. The study focused on solutions containing the oxoanion components in the ratios (Mo + V)/P = 12:1 and Mo/V ≥ 3.8, in the pH range 0-5, wherein Keggin anions of the formula [H(z)Mo12-(x)V(x)PO40]((3+X- z)-) with x = 1-3 are the predominant species. Formation constants (log β and pK(a) values for Keggin anions with x = 1-3 were determined from 31P and 51V resonance chemical shift data, 31P resonance intensity data, and pH potentiometric data with the multidata least squares calculation program LAKE. The [Mo11VPO40]4- anion does not protonate, [Mo10V2PO40]5- anions can be monoprotonated, and [Mo9V3PO40]6- anions can be triprotonated. The six most intense 31P NMR resonances of [H(z)Mo9V3PO40]((6-z)-) could be followed over the pH range studied. It was also possible to assign some 31P resonances to a specific isomer of [Mo9V3PO40]6-.
Selling, Anna,Andersson, Ingegaerd,Grate, John H.,Pettersson, Lage
p. 1509 - 1521
(2007/10/03)

Magnetic, electric and structural properties of β-AxV2O5 (A - Na, Ag)
Physical properties of β-AxV2O5 (A = Na, Ag) have been systematically reconsidered from structural, electric, and magnetic points of view. We prepared samples, both powder and single crystal, with precise composition for this purpose. The single crystals have been successfully grown by a self flux method using NaV3O8 as a flux. The precise adjustment of x was performed by embedding the as-grown crystals in a large amount of powder and heating them. β-Na0.33V2O5 was not a conventional semiconductor but a possible anisctropic metal at higher temperatures. It exhibited a metal-insulator transition at 136 K, suggesting a charge ordering. The ordered structure underwent a magnetic ordering with Tc = 24 K. We also observed a development of 1 x 2 x 1 superstructure below 230K. suggesting an ordering of the intercalated ion. Those transitions similarly occurred in β-Ag0.33V2O5. The deviation from x = 0.33 drastically decreased the transition temperatures or magnitudes of anomalies at the transitions, and both metallic behavior in the high temperature phase and magnetic ordering were lost.
Yamada, Hiroyuki,Ueda, Yutaka
p. 2735 - 2740
(2008/10/08)

Crystal structures and electronic properties in the crossover region between the spin-gap system CaV2O5 and the linear-chain system NaV2O5
The structural and electronic properties of the Ca1-xNaxV2O5 system, where the composition CaV2O5 exhibits an isolated dimer-like spin-gap state, and NaV2O5 indicates a linear-chain magnetic behaviour and undergoes a spin-singlet transition at Tc = 34 K, have been explored by means of x-ray four-circle diffraction and through magnetization and electron paramagnetic resonance measurements. The crystal structures with 0 2O5, where the space group is Pmmn. The effective V valence is correlated with the V-O bond length in the VO5 pyramid, and the transfer integral for the next-nearest-neighbour V-V path is suggested to be larger than those for other paths, which may be consistent with the formation mechanisms of the dimer in the Ca-rich compounds and the V-O-V molecular orbital in the Na-rich compounds. The magnetic properties for 0 a large reduction of the exchange coupling constant disappears, and no magnetic ordering takes place. The characteristic spin dynamics for the Na-rich compounds is also discussed.
Onoda, Masashige,Kagami, Takeo
p. 3475 - 3488
(2008/10/08)

Specific heat of α′-NaV2O5 at its spin-Peierls transition
We have measured the specific heats of small (≈1 mg) crystalline flakes of α′-NaV2O5. A large sharp peak is observed at its (33 K) spin-Peierls transition. The size of the peak (ΔcP≈R) is more than an order of magnitude greater than the value estimated from mean-field theory, consistent with large fluctuations expected from its one-dimensional magnetic structure. However, the peak is somewhat sample dependent and does not have the symmetry about Tc expected for either Gaussian or critical fluctuations, suggesting either that the samples are near a multicritical point or that there is some heterogeneous broadening, in which case we are underestimating the true size of the anomaly. The low-temperature behavior is consistent with a Debye temperature between 345 and 414 K, depending on the size of magnetic contributions to the specific heat.
Powell,Brill,Zeng,Greenblatt
p. R2937-R2940
(2008/10/08)

Reactions of FeVO4 with Sodium Salts
The mechanisms of reactions of the sodium salts Na2SO4, NaCl, Na2CO3, and NaNO3 with iron orthovanadate FeVO4 in air is studied by X-ray, DTA, and thermodynamic analyses.
Fotiev,Danilov,Surat
p. 972 - 976
(2008/10/08)

(NH4)0.67Na0.33[VO2(SO 4)(H2O)2]: Preparation and Properties
Formation conditions and properties of a new vanadium(V) compound of the composition (NH4)0.67Na0.33[VO2(SO 4)(H2O)2] were examined. This compound is a structural and chemical analogue of the previously prepared compounds M0.67Na0.33[VO2(SO4)(H 2O)n] (M = K, Rb, or Cs; n = 2). On heating in air, (NH4)0.67Na0.33[VO2(SO 4)(H2O)2] is decomposed without forming the corresponding anhydrous compound and completely loses SO3 at 900°C to yield the well-known polyvanadate NaV3O8.
Krasil'nikov,Galaktionov
p. 819 - 823
(2008/10/08)

Magnetic Susceptibility of Quasi-One-Dimensional Compound α'-NaV2O5 - Possible Spin-Peierls Compound with High Critical Temperature of 34 K -
Stoichiometric powder samples of α'-NaV2O5 were synthesized and the magnetic susceptibility was measured in the temperature range from 2K to 7000 K. The magnetic susceptibility has a good fit to the equation for an S = 1/2 antiferromagnetic Heisenberg linear chain with J/KB = 280 K and g = 2 above 34 K. Below 34 K the magnetic susceptibility rapidly decreases with decreasing temperature to a constant value of 1.49 × 10-4 emu/V4+ -mol which is reasonable for spin-singlet V4+-V4+ pairs. This rapid reduction of the spin susceptibility below 34 K suggests the existence of a spin-Peierls transition. α'-NaV2O5 is a possible spin-Peierls compound with the highest critical temperature yet observed.
Isobe, Masahiko,Ueda, Yutaka
p. 1178 - 1181
(2008/10/08)

Li3VO4(Na3VO4)-Pb 3(VO4)2-V2O5 Systems
Phase compositions of the systems Li3VO4-Pb3(VO4)2-V 2O5 and Na3VO4-Pb3(VO4)2-V 2O5 are studied. No double vanadates were found in the first system, whereas NaPbVO4, NaPb4(VO4)3, and Na5PbV3O11 compounds were identified in the latter. Diagrams of phase relations in the subsolidus regions (450-500°C) are constructed.
Slobodin,Maksimova
p. 1153 - 1155
(2008/10/08)

Vibrational spectra of NaVO3, KVO3 and the solid solutions (Na0.88K0.12)VO3 and (Na0.5K0.5)VO3
The phase transition in KVO3 involving changes in the dielectric properties was investigated by means of Raman spectroscopy. A temperature dependence study of the Raman active modes did not reflect the reported changes in the dielectric properties of the compound around 593 K. Infrared and Raman spectra of the two solid solutions, (Na0.88K0.12)VO3 and (Na0.5K0.5)VO3 are presented in comparison with those of KVO3 and α-NaVO3. The translational modes of the cations could accordingly be identified unambiguously. The frequency dependence of the various vibrational, rotational and translational modes of the VO3- chain on composition is also reported and compared to high-pressure behavior of some NH4VO3 vibrations.
de Waal,Heyns
p. 129 - 136
(2008/10/08)

High-temperature interactions of transition-metal carbides with Na2SO4
The high-temperature (900-1200 K) interaction of transition-metal carbides namely Cr7C3, Fe3C, TiC, ZrC, NbC, TaC, MoC, WC, VC and HfC with Na2SO4 has been studied in a stream of pure and dried oxygen gas. Thermogravimetric studies were carried out by measuring the weight change as a function of time and mole fraction of Na2SO4 in the reaction mixture. The presence of different constituents in the reaction products were identified by X-ray diffraction analysis and the morphologies of the reaction products were discussed on the basis of metallography, scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX). The quantitative determination of soluble metal species in the aqueous solutions of Na2SO4-transition-metal carbide products was carried out by atomic absorption spectroscopy. At high temperatures, transition-metal carbides interact with Na2SO4, forming metal oxides. The resulting metal oxide interacts with Na2SO4 forming a soluble sodium metal oxide or a metal sulphide depending upon the local condition prevailing during the reaction.
Mobin, M.,Malik, A. U.
p. 243 - 254
(2008/10/08)

IR Matrix Isolation Study of Alkali-Metal Metavanadate Monomers and Dimers
In this paper are reported the results of matrix-isolation IR studies of lithium, sodium, potassium, and rubidium metavanadates.A critical analysis of these results in comparison with those of previous studies on the cesium metavanadate allows one to assume the existence of stable gaseous XVO3 monomer and dimer species, both of importance in the equilibrium vapors, as definitely proved for X = K, Rb, and Cs, while reasonably inferred for X = Li and Na.Moreover, a C2v symmetry can be reasonably assumed for the dimeric species.Mixed gaseous dimers with differentalkali-metal atoms in their frame, like KCs(VO3)2 and RbCs(VO3), have been also, for the first time, identified.
Guido, Marcella,Cesaro, Stella Nunziante
p. 2836 - 2839
(2007/10/02)

STUDY ON THE PREPARATION AND PHYSICAL PROPERTY DETERMINATION OF NaVO2.
Stoichiometric and near-stoichiometric NaVO//2 phases have been prepared by the hydrogen reduction of NaVO//3 or mixtures of Na//2CO//3 and V//2O//5 at 650 degree C. The black reduction products react instantly with air to generate nonstoichiometric Na//xVO//2 phases with the formation of NaOH. Stoichiometry of the compound could be maintained by working in a dry box under a gettered argon atmosphere. Pure NaVO//2 was characterized by X-ray diffraction studies, thermoanalytical methods, and magnetic measurements. The semireversible crystallographic transition was noted at 115 degree C by means of a differential scanning calorimetry experiment. This transition, however, is very weak and quite broad. At room temperature, NaVO//2 appears to be orthorhombic, but above the transition temperature, it adopts the alpha -NaFeO//2 structure. The magnetic properties indicate a moderate interaction between vanadium centers.
Chamberland,Porter
p. 398 - 404
(2008/10/08)

SODIUM SULFATE DOPED WITH SODIUM VANADATE AND RARE EARTH SULFATE AS A SOLID ELECTROLYTE FOR A SULFUR DIOXIDE GAS DETECTOR.
Sodium sulfate doped with NaVO//3 and Ln//2(SO//4)//3 (Ln EQUVLNT Eu, Pr, and Y) show higher electrical conductivity for Na** plus ions and maintains a high temperature phase, Na//2SO//4-I, without showing phase transformation. The electromotive force (EMF) using solid solutions, Na//2SO//4-NaVO//3-Ln//2(SO//4)//3 (Ln equals Pr and Y), as solid electrolytes exhibits good agreement with the calculated value, the temperature as low as 673 K which is approximately 300 K lower than pure sodium sulfate can be.
Imanaka,Adachi,Shiokawa
p. 687 - 691
(2007/10/02)

THE INFRARED AND RAMAN SPECTRA OF MATRIX-ISOLATED M-V-O SYSTEMS. THE CHARACTERIZATION OF MVO3 AND MVO2 MOLECULES
Gaseous alkali vanadates MVO3 and MVO2 have been identified by means of IR matrix isolation spectroscopy and their spectra interpreted on the basis of C2v ring structures.Raman spectra have been obtained for matrix-isolated CsVO3 and CsVO2.The
Bencivenni, L.,Gingerich, K. A.
p. 197 - 202
(2007/10/02)

ELECTROCHEMICAL STUDY OF THE MIXED BETA-VANADIUM BRONZES LiyNaxV2O5 AND LiyKxV2O5.
It has been found that lithium may be rapidly inserted into beta -phase sodium and potassium vanadium bronzes to yield phases of composition Li//yNa//xV//2O//5 and Li//yK//xV//2O//5. For (x plus y) values less than about 2/3, a single-phase region is found. For higher lithium contents two additional narrow phases are formed; the maximum alkali metal content appears to correspond to a vanadium oxidation state of 4. The reversibility of the insertion reactions and X-ray powder diffraction indicate that the structures of the higher-lithium-content phases are closely related to the beta -phase. Thermodynamic data have been derived from the electrochemical results.
Raistrick,Huggins
p. 337 - 346
(2008/10/08)

PROPERTIES OF Na2SO4 DOPED WITH NaVO3 AND Pr2(SO4)3 AS A SOLID ELECTROLYTE
Sodium sulfate doped with both sodium vanadate and praseodymium sulfate has been investigated as solid electrolyte for SO2 detecting device.Na2SO4-NaVO3-Pr2(SO4)3 (91.1:3.9:5.0) shows higher electric conductivity than pure Na2SO4.The measured EMF for an SO2 concentration cell using this electrolyte is in good accord with the calculated one.NaVO3 stabilizes a high temperature phase, Na2SO4-I.
Imanaka, Nobuhito,Adachi, Gin-ya,Shiokawa, Jiro
p. 287 - 288
(2007/10/02)