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1.
Janko Dimitriev Vesselin Dimitrov Michail Arnaoudov 《Monatshefte für Chemie / Chemical Monthly》1978,109(4):791-797
Glasses from the TeO2–VO2 system and - and -crystalline modifications of TeO2·VO2 (TeVO4) are studied by IR-spectroscopy in the 1400–400 cm–1 range. Similarity is established in the area near 970 cm–1 of the spectrum between TeVO4 glass and the -form. The continuous shift of the band from 970 cm–1 to 950 cm–1 with increasing TeO2 content in the glasses is connected with the indirect influence on the nonbridging V–O bond.It is shown that the local environment of the V in some glasses from TeO2–VO2 and TeO2–V2O5 system is similar: VO5 polyhedra. 相似文献
2.
3.
M. Ishaque Khan Thomas Hope Sabri Cevik Chong Zheng Douglas Powell 《Journal of Cluster Science》2000,11(3):433-447
The synthesis and crystal structures of [H3NCH2CH2NH3][V2O6] (1) and [HN(CH2CH2)3NH][VV
2VIV
4O14]·H2O (2) are described. The structure of the oxidized compound 1 consists of parallel stacks of vanadium oxide chains of corner sharing {VO4} tetrahedra. The chains are stabilized by extensive hydrogen bonding involving oxide ligands of the chains and ethylenediammonium ions which fill the space between the stacks of chains. The structure of compound 2 consists of vanadium oxide layers separated by doubly protonated 1,4-diazabicyclo[2.2.2]octane and lattice water. The vanadium oxide layers, containing mixed-valence vanadium (VV and VIV) centers, are composed of zigzag ribbons of edge-sharing {VO5} square pyramids interconnected by {VO4} tetrahedra. Crystal data. C2H10N2O6V2 , 1: monoclinic, space group P21/c (No. 14), a=5.5359(5), b=12.9430(12), c=5.6856(5) Å, =90, =97.460(2), =90°, V=403.93(6) Å3, Z=2. A total of 2506 reflections (
max=27.89°) was collected, of which 954 were used to resolve the structure. The structure was solved by direct methods and least-squares refinement converged at R=0.0592. C6H16N2O15V6, 2: monoclinic, space group C2 (No. 5), a=19.303(4), b=6.667(2), c=7.579(2) Å, =90, =111.31(2), =90°, V=908.4(4) Å3, Z=2. A total of 1779 reflections was collected, of which 1591 unique reflections were used for structural elucidation. The structure was solved by direct methods and least-squares refinement converged at R=0.0314. 相似文献
4.
L. Bonhomme-Coury N. Lequeux S. Mussotte P. Boch 《Journal of Sol-Gel Science and Technology》1994,2(1-3):371-375
Sol-gel routes in the ternary system Al2O3-TiO5-ZrO2 were investigated to prepare Al2TiO5-ZrO2 mixed powders. The preparation of ZrTiO4 and Al2TiO5 was studied before going on with the ternary system. Zirconium titanate precursor gels were prepared from Ti(OPri)4 and Zr(OPrn)4 mixtures. The crystallization of ZrTiO4 develops at T<700°C. Al2TiO5 was prepared by different ways, using mixtures of Al(OBus)2(C6H9O3) with Ti(OPr
i
)4 (i), or with acetic acid addition (ii). Route (i) leads to a separate crystallization of TiO2 and -Al2O3, with subsequent formation of -Al2TiO5 at T1360°C. Although the pseudobrookite -Al2TiO5 is thermodynamically unstable below 1280°C, route (ii) leads to the crystallization of metastable -Al2TiO5 at T800°C. At increasing temperature, -Al2TiO5 decomposes into TiO2 and -Al2O3, then the two compounds react to form stable -Al2TiO5. For the ternary system, all the preparation routes which were studied lead to ZrTiO4 and -Al2O3 with subsequent reaction (at T1500°C) to give -Al2TiO5 and ZrO2. 相似文献
5.
Crystals of the -complex [C4H8N2(C3H5)4]2+[CuCl2]–
2 (I) were prepared by ac electrochemical synthesis from copper and N,N,N,N-tetraallylpiperasinium chlorides in alcohol solution. Similar synthesis with the use of the metal and N,N,N,N-tetraallylpiperasinium bromides yielded the complex [C4H8N2(C3H5)4]2+[CuBr3]2– (II). Structures I and II were studied by X-ray diffraction (DARCh automated single-crystal diffractometer, MoK
radiation). Crystals of I are triclinic, space group P1¯, a = 8.650(3) Å, b = 7.572(2) Å, c = 8.095(3) Å, = 100.45(2)°, = 83.91(2)°, = 99.89(2)°, V = 512.1(6) Å3, Z = 1. Crystals of II are orthorhombic, space group Pn21
a, a = 17.673(3) Å, b = 14.369(6) Å, c = 8.244(2) Å, V = 2093(2) Å3, Z = 4. In structure I, the potentially tetradentate N,N,N,N-tetraallylpiperasinium cation uses two centrosymmetric allyl groups for bonding with copper atoms, whose environment is completed to the trigonal-planar coordination with the chlorine atoms. The [C4H8N2(C3H5)4]2+[CuCl2]–
2 groups are joined into a three-dimensional framework by weak hydrogen bonds. The inorganic fragment CuCl–
2 is partially disordered, which appears as splitting of the positions of the copper atom and one of the chlorine atom. In compound II, the inorganic fragment occurs as an unusual trigonal-planar CuBr2–
3 anion; the N,N,N,N-tetraallylpiperasinium cation is not involved in metal coordination. 相似文献
6.
A room temperature water solution of (I) crystallizes as a racemate, space groupP2
1/n with lattice constantsa=7.737(6),b=10.694(5),c=15.097(6) Å, and=102.83(5)°;V=1218.05 Å3 andd (calc; M.W.=337.24, Z=4) = 1.642 g cm–3. A total of 2381 data were collected over the range 4° 2 < 50°; of these, 1452 (independent and withI 3(I)) were used in the structural analysis. Data were corrected for absorption ( = 15.76 cm–1), and the relative transmission coefficients ranged from 0.8976 to 0.9984. Refinement led to the finalR(F) andR
w(F) residuals of 0.0858 and 0.1116. A room temperature water solution of (II) crystallizes as a racemate in space group P21/c with lattice constantsa=6.638(3),b=11.425(8),c=15.147(16) Å, and=93.27(6)°; F=1146.8 Å andd (calc; M.W.=323.2,Z=4) = 1.872 g cm–3. A total of 2200 data were collected over the range 4° 2 < 50°; of these, 1918 (independent and withI 3(I)) were used in the structural analysis. Data were corrected for absorption (=16.94 cm–1), and the relative transmission coefficients ranged from 0.9049 to 0.9967. Refinement led to the finalR(F) andR
w(F) residuals of 0.0231 and 0.0279. The chirality symbol for the particular enantiomer of (I) refined here is (), while for (II) the chirality symbol is (), which means that in the latter compound one of the en rings is in a higher energy conformation. We attribute this result to competitive intramolecular hydrogen-bonded interactions between the — NH2 hydrogens of the en ligands and the oxygens of the -NO2 and -SO3 ligands, strengths which are enhanced by coercing a change in sign of the torsional angle of one en ringa motion which permits both oxo ligands to form stronger hydrogen bonds while retaining proper O O contacts. This phenomenon is not observed in (I) since the azide ligand does not compete with -SO3 for such hydrogen-bonded interactions, and nonbonded pair repulsions can be minimized without affecting the ability of — SO3 oxygens to form strong intramolecular hydrogen bonds. 相似文献
7.
B. Samuneva V. Dimitrov Y. Dimitriev V. Chernev G. Gochev 《Journal of Sol-Gel Science and Technology》1994,2(1-3):913-915
Blue-coloured gels have been prepared in the VO2-SiO2 system up to 80 mol% VO2 by sol-gel technology using TEOS and aqueous solutions of VOSO4·5H2O. It is established by means of VIS and ESR spectra that at low temperatures VO2+ complexes are formed. An oxidation of V4+ has taken place with increasing temperature, and V2O5 and cristobalite have been separated. Silica gel glasses stable up to 800°C have been obtained from gels containing 1–3 mol% VO2. 相似文献
8.
Abdeljalil Assoud 《Journal of solid state chemistry》2006,179(8):2707-2713
The title compounds were prepared from the elements in the stoichiometric ratio at 800 °C under exclusion of air. Tl6Si2Te6 crystallizes in the space group P1¯, isostructural with Tl6Ge2Te6, with , , , α=89.158(2)°, β=96.544(2)°, γ=100.685(2)°, (Z=2). Its structure is composed of dimeric [Si2Te6]6− units with a Si-Si single bond, while the Tl atoms are irregularly coordinated by five to six Te atoms. Numerous weakly bonding Tl-Tl contacts exist. Both title compounds are black semiconductors with small band gaps, calculated to be 0.9 eV for Tl6Si2Te6 and 0.5 eV for Tl6Ge2Te6. The Seebeck coefficients are +65 μV K−1 in case of Tl6Si2Te6 and +150 μV K−1 in case of Tl6Ge2Te6 at 300 K, and the electrical conductivities are 5.5 and 3 Ω−1 cm−1, respectively. 相似文献
9.
Angela Šurca Vuk Sandra Benčič Boris Orel Franco Decker 《Journal of Sol-Gel Science and Technology》2002,23(1):53-66
Electrochemical properties of amorphous and crystalline V2O5 films, dip-coated from V-oxoisopropoxide sols and thermally treated at various temperatures (100, 150, 200 and 300°C), have been studied in extended potential range, i.e. from 1.4 to –1.6 V vs. Ag/AgCl in 1M LiClO4/propylen carbonate (PC) electrolyte. The formation of various lithiated (-, -, - and -Li
x
V2O5) phases was correlated with the values of insertion coefficient x obtained from cyclic voltammograms (CV) of crystalline V2O5 films (300°C). Reversible charging was observed when films were cycled up to –1.0 V vs. Ag/AgCl, while the extension of the potential to –1.3 V vs. Ag/AgCl change the CV of films irreversibly. Charging of crystalline V2O5 films was followed by the help of in-situ UV-visible spectroscopy, that revealed the intensity variations of the polaron absorption above 600 nm and the presence of the absorbing V3+ species between 550 and 650 nm. Ex-situ IR spectra of the crystalline films charged/discharged at –1.6V/1.4V vs. Ag/AgCl confirmed the amorphisation of the films' structure. 相似文献
10.
We have made calorimetric measurements leading to apparent molal heat capacities of pyridine and four methyl-substituted pyridines in aqueous solution at 25.0°C. Measurements of densities of the same solutions have led to apparent molal volumes. The results are as follows: pyridine,
C
°
= 305.7 J–°K–1-mole–1 and
V
°
= 77.5 cm3-mole–1; 2-methylpyridine,
C
°
= 370.0 J–°K–1-mole–1 and
V
°
= 94.3 cm3-mole–1; 3-methylpyridine,
C
°
= 380.2 J–°K–1-mole–1 and
V
°
= 93.7 cm3-mole–1; 4-methylpyridine,
C
°
= 378.9 J–°K–1-mole–1 and
V
°
= 94.3 cm3-mole–1; 2,6-dimethylpyridine,
C
°
= 441.8 J–°K–1-mole–1 and
V
°
= 109.9 cm3-mole–1. These
C
°
and
V
°
values are discussed in terms of effects of substitution of CH3-for H– in the various solute molecules.The research reported here was carried out in the Department of Chemistry, University of Lethbridge, Lethbridge, Alberta, Canada T1K 3M4. 相似文献
11.
Densities and apparent molar volumes of aqueous 2-chloroethanol were determined at temperatures from 15.0 to 34.4°C using digital densimetry. The results of the volumetric measurements have been used to calculate the following thermodynamic quantites at 25°C: V
2
o = 55.05 ± 0.02 cm3-mol–1, (V
2
o/T)p = 0.01486 ± 0.00318 cm3-K–1-mol–1, and (2
V
2
o/T
2)p = 0.02972 ± 0.00318 cm3-K–2-mol–1. Partial molar volumes of transfer from water to 1 mol-dm–3 2-chloroethanol have also been determined for L-glycine, L-alanine, L-serine, L-glutamic acid, and L-aspartic acid at 35.0°C. The transfer results have been explained in terms of the nature of the interactions of the groups in the solute and solvent. Hydration numbers of L-glycine and L-alanine have also been calculated in aqueous 2-chloroethanol. 相似文献
12.
Hong Lin Hiromitsu Kozuka Toshinobu Yoko 《Journal of Sol-Gel Science and Technology》2000,19(1-3):529-532
In the present study n-type and p-type transparent conductive TiO2 films were prepared by using sol-gel method. The n-type TiO2 films were obtained by using Ti(OC3H
7
i
)4 solutions co-doped with Ru and Ta. The films were uniform and transparent in all the conditions, and their crystalline phases were anatase when HCl or HNO3 was used as a catalyst. The resistivity decreased with increasing Ta content and increased with increasing Ru content. Most of the films showed resistivity minima at a heat-treatment temperature of 700°C. The lowest resistivity of 101 102 cm was attained. The p-type TiO2 films were obtained by using Ti(OC3H
7
i
)4 solutions co-doped with Co and Nb (Sb). The films were also uniform and transparent when AcAc was used, while samples heat-treated at 800°C became opaque when HCl was added. Rutile single phase appeared when the films were heat-treated at 700°C. Logarithmic resistivity of films co-doped with Co and Nb was directly proportional to the reciprocal absolute temperature. On the other hand, the slopes for films co-doped with Co and Sb were different below and above 200°–220°C. The activation energy at the low-temperature region is as low as 0.17 eV, and the resistivity at room temperature is 104 105 cm. 相似文献
13.
Shahid P. Shafi Rylan J. Lundgren Lachlan M.D. Cranswick Mario Bieringer 《Journal of solid state chemistry》2007,180(12):3333-3340
We report the preparation and stability of ScVO3.5+x and the novel phase InVO3.5+x. AVO3.5+x (A=Sc, In) defect fluorite structures are formed as metastable intermediates during the topotactic oxidation of AVO3 bixbyites. The oxidation pathway has been studied in detail by means of thermogravimetric/differential thermal analysis and in-situ powder X-ray diffraction. The oxidation of the bixbyite phase follows a topotactic pathway at temperatures between 300 and 400 °C in air/carbon dioxide. The range of accessible oxygen stoichiometries for the AVO3.5+x structures following this pathway are 0.00x0.22. Rietveld refinements against powder X-ray and neutron data revealed that InVO3.54 and ScVO3.70 crystallize in the defect fluorite structure in space group Fm-3 m (227) with a=4.9863(5) and 4.9697(3)Å, respectively with A3+/V4+ disorder on the (4a) cation site. Powder neutron diffraction experiments indicate clustering of oxide defects in all samples. Bulk magnetic measurements showed the presence of V4+ and the absence of magnetic ordering at low temperatures. Powder neutron diffraction experiments confirmed the absence of a long range ordered magnetic ground state. 相似文献
14.
The stability constants of the systems dioxovanadium(V) with alanylalanine, alanylglycine, and alanine have been determined in aqueous solution in 0.8 pH 5 at 25°C and 0.1 mol-dm–3 (NaClO4), using a combination of potentiometric and spectrophotometric techniques. The compositions of the formed complexes were determined and it was shown that dioxovanadium(V) forms two mononuclear 1:1 and 1:2 species with alanine of the type VO2L and VO2L2
–, and two mononuclear 1:1 complexes with alanylpeptides of the type VO2HL and VO2L–. 相似文献
15.
Michael A. McGuire Andrew F. May David J. Singh Mao-Hua Du Gerald E. Jellison 《Journal of solid state chemistry》2011,184(10):2744-2750
Experimental and theoretical studies of the electronic and optical properties of orthorhombic BaCu2Se2 and BaCu2Te2 are reported. Experimental data include the electrical resistivity, Hall coefficient, Seebeck coefficient, thermal conductivity, and lattice constants for , and optical transmission and diffuse reflectance data at room temperature. Nominally stoichiometric, polycrystalline samples form with hole concentrations inferred from Hall measurements of 2×1018 and 5×1019 cm−3 near room temperature for the selenide and telluride, respectively. The corresponding mobilities are near 15 cm2 V−1 s−1 for both materials. Optical measurements reveal a transition near 1.8 eV in BaCu2Se2, while no similar feature was observed for BaCu2Te2. First principles calculations indicate both materials are direct or nearly direct gap semiconductors with calculated gaps near 1.0 eV and 1.3 eV for the telluride and selenide, respectively, and predict weak absorption below about 2 eV. Transport properties calculated from the electronic structure are also presented. 相似文献
16.
L. Bapat 《Journal of Radioanalytical and Nuclear Chemistry》1987,117(4):217-232
Pellets of TiO2 thermally pretreated at 450 and 540°C and -irradiated were polarized by d. c. field. The depolarization curves were resolved into different first order components having two and three depolarization constants. By heating the polarized pellets the Current Glow Peak curves were recorded where there were only two peaks around 65 and 400°C in case of pellets heated at 450°C and heated at 540°C and irradiated; and one more additional peak around 20°C in case of pellets heated at 540°C and heated at 450°C and irradiated thereon. In addition to those signals of O
2
–
and Ti3+ reported earlier there were distinctly four more, signals at g 1.933 and g 2.03, 2.036 and 2.043 appeared in case of samples heated at 540°C and heated at 450°C and irradiated thereon. The signal at g1.933 is attributed to Ti3+ ions in new phase Ti4O7 developed in heating at 540°C or due to irradiation and the rest of the signals are due to O
2ad
–
or O
ad
–
over the new phase near anion vacancy created. 相似文献
17.
The organic-inorganic hybrid materials vanadium oxide [VIVO2(phen)2]·6H2O (1) and [(2,2′-bipy)2VVO2](H2BO3)·3H2O (2) have been conventional and hydrothermal synthesized and characterized by single crystal X-ray diffraction, elemental analyses, respectively. Although the method and the ligand had been used in the syntheses of the compounds (1) and (2) are different, they almost possess similar structure. They all exhibit the distorted octahedral [VO2N4] unit with organonitrogen donors of the phen and 2,2′-bipy ligands, respectively, which coordinated directly to the vanadium oxide framework. And they are both non-mixed-valence complexes. But the compound (1) is isolated, and the compound (2) consists of a cation of [(2,2′-bipy)2VVO2]+ and an anion of (H2BO3)−. So the valence of vanadium of (1) and (2) are tetravalence and pentavalence, respectively. Meanwhile it is noteworthy that π-π stacking interaction between adjacent phen and 2,2′-bipy groups in compounds 1 and 2 also play a significant role in stabilization of the structure. Thus, the structure of [VIVO2(phen)2]·6H2O and [(2,2′-bipy)2VVO2](H2BO3)·3H2O are both further extended into interesting three-dimensional supramolecular. Crystal data: (1) Triclinic, a=8.481(4), b=12.097(5), and α=66.32(2), β=82.97(3), and γ=82.59(4)°, Z=2, R1=0.0685, wR2=0.1522. (2) Triclinic, a=6.643(13), b=11.794(2), and α=101.39(3), β=101.59(3), and γ=97.15(3)°, Z=2, R1=0.0736, wR2=0.1998. 相似文献
18.
Digamber G. Porob 《Journal of solid state chemistry》2004,177(12):4535-4541
Two new compounds Ca0.5Bi3V2O10 and Sr0.5Bi3V2O10 have been synthesized in the ternary system: MO-Bi2O3-V2O5 system (M=M2+). The crystal structure of Sr0.5Bi3V2O10 has been determined from single crystal X-ray diffraction data, space group and Z=2, with cell parameters a=7.1453(3) Å, b=7.8921(3) Å, c=9.3297(3) Å, α=106.444(2)°, β=94.088(2)°, γ=112.445(2)°, V=456.72(4) Å3. Ca0.5Bi3V2O10 is isostructural with Sr0.5Bi3V2O10, with, a=7.0810(2) Å, b=7.8447(2) Å, c=9.3607(2) Å, α=106.202(1)°, β=94.572(1)°, γ=112.659(1)°, V=450.38(2) Å3 and its structure has been refined by Rietveld method using powder X-ray data. The crystal structure consists of infinite chains of (Bi2O2) along c-axis formed by linkage of BiO8 and BiO6 polyhedra interconnected by MO8 polyhedra forming 2D layers in ac plane. The vanadate tetrahedra are sandwiched between these layers. Conductivity measurements give a maximum conductivity value of 4.54×10−5 and 3.63×10−5 S cm−1 for Ca0.5Bi3V2O10 and Sr0.5Bi3V2O10, respectively at 725 °C. 相似文献
19.
Spectroscopic study of polycrystalline TiO2 doped with vanadium 总被引:2,自引:0,他引:2
The structure of coordination sites (V4+ ions) and their spatial distribution in the polycrystalline titanium dioxide (rutile) lattice were studied by ESR. It was found that at low degrees of doping, at [V4+] < 0.5 at.%, the vanadium ions are isotropically distributed in the rutile lattice. At [V4+] > 0.5 at.% a new microphase with the mixed composition {TiO2—VO2} is formed. The mixed microphase has a noticeably narrower band gap than the initial TiO2. Comparison of the photocurrent spectra and the plots of the integral photocurrent vs. vanadium content with the structural data obtained using ESR spectroscopy showed that the formation of the {TiO2—VO2} microphases deteriorates the photoelectrochemical properties of the modified photoelectrodes. Synthetic procedures interfering the formation of such microphases in the doped rutile are discussed. 相似文献
20.
ZnO/TiO2/SnO2 mixture was prepared by mixing its component solid oxides ZnO, TiO2 and SnO2 in the molar ratio of 4?1?1, followed by calcining the solid mixture at 200-1300 °C. The products and solid-state reaction process during the calcinations were characterized with powder X-ray diffraction (XRD), thermogravimetric and differential thermal analysis (TG-DTA), UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS) and Brunauer-Emmett-Teller measurement of specific surface area. Neither solid-state reaction nor change of crystal phase composition took place among the ZnO, TiO2 and SnO2 powders on the calcinations up to 600 °C. However, formation of the inverse spinel Zn2TiO4 and Zn2SnO4 was detected at 700-900 and 1100-1200 °C, respectively. Further increase of the calcination temperature enabled the mixture to form a single-phase solid solution Zn2Ti0.5Sn0.5O4 with an inverse spinel structure in the space group of . The ZnO/TiO2/SnO2 mixture was photocatalytically active for the degradation of methyl orange in water; its photocatalytic mass activity was 16.4 times that of SnO2, 2.0 times that of TiO2, and 0.92 times that of ZnO after calcination at 500 °C for 2 h. But, the mass activity of the mixture decreased with increasing the calcination temperature at above 700 °C because of the formation of the photoinactive Zn2TiO4, Zn2SnO4 and Zn2Ti0.5Sn0.5O4. The sample became completely inert for the photocatalysis after prolonged calcination at 1300 °C (42 h), since all of the active component oxides were reacted to form the solid solution Zn2Ti0.5Sn0.5O4 with no photocatalytic activity. 相似文献