Phase formation in the V<Subscript>2</Subscript>O<Subscript>5</Subscript>-Ta<Subscript>2</Subscript>O<Subscript>5</Subscript>-MoO<Subscript>3</Subscript> system

Solid-phase interactions in the V₂O₅-Ta₂O₅-MoO₃ system were studied. The formation of com- pounds TaVO₅ and VTa₉O₂₅ in the V₂O₅-Ta₂O₅ binary system was verified. Tetragonal VTa₉O₂₅-base solid solutions of the general formula Ta_{5 + 4x} V_{5 − 4x} O₂₅ (x = 0.25–1) and TaVO₅-base solid solutions of the general formula Ta _x Mo_{1 − x} V_{2 − x} O_{8 − 3x} (x = 0.625–1) were found to form. Subsolidus phase equilibria in the V₂O₅-Ta₂O₅-MoO₃ were determined.     

The reactivity of SbVO<Subscript>5</Subscript> with T-Nb<Subscript>2</Subscript>O<Subscript>5</Subscript> in solid state in air

The reactivity of SbVO₅, a compound known since a short time, with T-Nb₂O₅ in solid state in air has been investigated over the whole component concentration range of a system built by these two reacting substances. The investigation results have shown that an equimolar mixture of SbVO₅ and T-Nb₂O₅ reacts with a subsequent formation of a hitherto unknown compound of the formula Nb₂VSbO₁₀. This compound has been characterized by the methods XRD, DTA/TG, and SEM. Its orthorhombic unit cell parameters have been calculated, and its stability in air up to 880 ± 10 °C has been proved. At this temperature, the compound melts incongruently with an accompanying deposition of solid Nb₉VO₂₅, i.e., of a compound that crystallizes in the binary oxide system V₂O₅–Nb₂O₅.     

Phase diagram of V<Subscript>2</Subscript>O<Subscript>5</Subscript>-MoO<Subscript>3</Subscript>-Ag<Subscript>2</Subscript>O system

The results concerning the synthesis, structure and thermal properties of V₂O₅-MoO₃-Ag₂O samples in the vanadium rich region of ternary system are presented in the form of quasi-binary phase diagrams in which at constant V₂O₅/MoO₃ molar ratios, equal 9:1, 7:3 and 1:1, the content of Ag₂O was variable. A new ternary phase isostructural with NaVMoO₆ has been detected in the investigated system.     

The phase diagram of V<Subscript>2</Subscript>O<Subscript>5</Subscript>-MoO<Subscript>3</Subscript>-Ag<Subscript>2</Subscript>O system

The results concerning the synthesis, structure and thermal properties of V₂O₅-MoO₃-Ag₂O samples in the molybdenum rich region of ternary system are presented in the form of quasi-binary systems: β-AgVO₃-β-Ag₂MoO₄, AgVMoO₆-MoO₃, AgVMoO₆-Ag₂Mo₄O₁₃, AgVMoO₆-Ag₂Mo₂O₇, AgVMoO₆-β-Ag₂MoO₄ and also of the system in which at V₂O₅/MoO₃ molar ratio 3:7 the content of Ag₂O was variable. The ternary phase AgVMoO₆ was not described earlier in the literature.     

Synthesis processes and transport properties of solid solutions in the Bi<Subscript>2</Subscript>O<Subscript>3</Subscript>-GeO<Subscript>2</Subscript>-V<Subscript>2</Subscript>O<Subscript>5</Subscript> system

The results of studies of solid solutions with the overall composition of Bi₄V_{2 ? x} Ge _x O_{11 ? δ} and Bi₄Ge_{3 ? x} V _x O_{12 + δ} are presented. The process of phase formation are studied during the synthesis of solid solution using the ceramic method and through liquid precursors. Crystallochemical parameters of the obtained compounds are determined. The size distribution of the particles is studied. Conductivity of annealed of polycrystalline samples as a function of temperature and composition is studied using the impedance spectroscopy method. The shape of impedance complex plane plots of the samples obtained in different ways is studied and analyzed.     

The phase diagram of V<Subscript>2</Subscript>O<Subscript>5</Subscript>-MoO<Subscript>3</Subscript>-Ag<Subscript>2</Subscript>O SYSTEM

The paper summarizes the results concerning the different parts of the ternary system V₂O₅-MoO₃-Ag₂O and presents projection of the diagram on the basal triangle as well as its three-dimensional presentation of the diagram drawn by the AutoCAD programme.     

Structure and electrical conductivity of cobalt-doped Bi<Subscript>26</Subscript>Mo<Subscript>10</Subscript>O<Subscript>69</Subscript>

The existence boundaries, structures, and transport parameters of Bi_{1 ? x} Co _x [Bi₁₂O₁₄]Mo₅O_{20 ± δ} and Bi[Bi₁₂O₁₄]Mo_{5 ? y} Co _y O_{20 ± δ} solid solutions, which have a unique columnar structure, were studied. Electrical conductivity in these solid solutions was studied by impedance spectroscopy.     

Phase relations in the CoO–V<Subscript>2</Subscript>O<Subscript>5</Subscript>–Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> system in subsolidus area

Thermal properties of Co₂FeV₃O₁₁ have been reinvestigated. It has been proved that this compound does not exhibit polymorphism. It melts incongruently at the temperature of 770±5°C and the phase with lyonsite type structure is the solid product of this melting. Phase relations in the whole subsolidus area of the CoO–V₂O₅–Fe₂O₃ system have been determined. The solidus area projection onto the component concentration triangle plane of this system has been constructed using the DTA and XRD methods. 15 subsidiary subsystems can be distinguished in this system.     

Formation and properties of the Fe<Subscript>8</Subscript>V<Subscript>10</Subscript>W<Subscript>16–x</Subscript>Mo<Subscript>x</Subscript>O<Subscript>85</Subscript> type solid solution

Solid solution phases of a formula Fe₈V₁₀W_16–xMo_xO₈₅ where 0≤x≤4, have been obtained, possessing a structure of the compound Fe₈V₁₀W₁₆O₈₅. It was found on the base of XRD and DTA investigations that these solution phases melted incongruently, with increasing the value of x, in the temperature range from 1108 (x=0) to 1083 K (x=4) depositing Fe₂WO₆ and WO₃. The increase of the Mo⁶⁺ ions content in the crystal lattice of Fe₈V₁₀W₁₆O₈₅ causes the lattice parameters a=b contraction with cbeing almost constant. IR spectra of the Fe₈V₁₀W_16–xMo_xO₈₅ solid solution phases have been recorded.     

The synthesis and selected properties of Co<Subscript>2</Subscript>InV<Subscript>3</Subscript>O<Subscript>11</Subscript>

It has been demonstrated that Co₂V₂O₇ and InVO₄ react with each other forming a new compound of the Co₂InV₃O₁₁ formula, when their molar ratio is equal to 1:1, or among CoCO₃, In₂O₃ and V₂O₅, mixed at a molar ratio of 4:1:3. This compound melts incongruently at the temperature of 960±5°C, depositing crystals of InVO₄. It crystallizes in the triclinic system and the unit cell parameters amount to: a=0.6524(6) nm, b=0.6885(5) nm, c=1.0290(4) nm, α=96.5°, β=104.1°, γ=100.9°, Z=2. The phase equilibria being established in the Co₂V₂O₇–InVO₄ system over the whole components concentration range up to the solidus line were described.     

Reinvestigation of system CdO-V<Subscript>2</Subscript>O<Subscript>5</Subscript> in the solid state

As a result of solid-state reactions three cadmium vanadates(V) have been obtained, i.e. CdV₂O₆, Cd₂V₂O₇ and Cd₄V₂O₉. Melting temperature and the product of melting has been determined for Cd4V2O9. Thermal properties of the obtained cadmium vanadates(V) have been reinvestigated. The phase equilibria being established in the CdO-V₂O₅ system over the whole components concentration range up to the solidus line were described.     

Phase relations in the Zn<Subscript>2</Subscript>V<Subscript>2</Subscript>O<Subscript>7</Subscript>-Cu<Subscript>2</Subscript>V<Subscript>2</Subscript>O<Subscript>7</Subscript> system from room temperature to melting

Phase relations in the Zn₂V₂O₇-Cu₂V₂O₇ system were studied by high-temperature X-ray diffraction and differential thermal analysis. The major phase constituents of the system are solid solutions based on Zn₂V₂O₇ and Cu₂V₂O₇ polymorphs and their coexistence regions. The generation of α-Zn_{2 − 2x} Cu_2x V₂O₇ solid solution, where 0 ≤ x ≤ 0.30, leaves almost unchanged the stabilization temperature of the high-temperature zinc pyrovanadate phase. The α-Cu_{2 − 2x} Zn_2x V₂O₇ homogeneity range is 5 mol % Zn₂V₂O₇. In the range 0.050 ≤ x ≤ 0.09 from 20 to ∼ 620°C, there is the two-phase field of α-Cu₂V₂O₇ and β-Cu₂V₂O₇ base solid solutions. At still higher temperatures, β-Zn_{2 − 2x} Cu_2x V₂O₇ and α-Cu_{2 − 2x} Zn_2x V₂O₇ coexist in the mixed-phase region. β-Zn_{2 − 2x} Cu_2x V₂O₇ solid solution, where 0 ≤ x ≤ 0.30, exists above 610 ± 5°C. The extent of the β′-Cu₂V₂O₇-base solid solution is 9 to 65 mol % Zn₂V₂O₇ at 615 ± 5°C, expanding to 0 mol % Zn₂V₂O₇ with rising temperature. Original Russian Text ￠ T.I. Krasnenko, M.V. Rotermel’, S.A. Petrova, R.G. Zakharov, O.V. Sivtsova, A.N. Chvanova, 2008, published in Zhurnal Neorganicheskoi Khimii, 2008, Vol. 53, No. 10, pp. 1755–1762.     

Solid Solutions of the System V<Subscript>2</Subscript>O<Subscript>5</Subscript>-V<Subscript>2</Subscript>O<Subscript>4</Subscript>-TiO<Subscript>2</Subscript> in Air

Gravimetry in combination with X-ray phase analysis, X-ray crystallography, and X-ray densitometry were used to determine the contents of V⁵⁺, V⁴⁺, and Ti⁴⁺ ions and vacancies in solid solutions formed by the reaction of V₂O₅ with TiO₂ in air at atmospheric pressure.     

Structure of a new chelate complex MO<Subscript>2</Subscript>O<Subscript>3</Subscript>(dpm)<Subscript>4</Subscript>

A new Mo₂O₃(dpm)₄ compound (I) is synthesized by the interaction of Mo(CO)₆ with 2,2,6,6-tetramethylheptanedione-3,5 (dpm). The structure of complex I determined by the XRD method is as follows: triclinic crystal system, space group P–1, a = 10.1780(7) Å, b = 10.1817(6) Å, c = 13.3255(9) Å, α = 110.562(2)°, β = 102.233(2)°, γ = 93.9041(19)°, V = 1248.17(14) ų. The compound is characterized by IR spectroscopy, mass-spectrometry and thermogravimetric analysis (TGA).     

Crystal Structure of New One-Dimensional Triple Molybdate Na<Subscript>2</Subscript>K<Subscript>2</Subscript>Cu(MoO<Subscript>4</Subscript>)<Subscript>3</Subscript>

The title compound (disodium dipotassium copper(II) tris-[molybdate (VI)]) is prepared by form melt and characterized by single crystal X-ray diffraction and UV-vis spectroscopy. It crystallizes in the triclinic space group P-1 with a = 7.4946(8) Å, b = 9.3428(9) Å, c = 9.3619(9) Å, α = 92.591(7)°, β = 105.247(9)°, γ = 105.496(9)°, V = 604.7 ų, and Z = 2. Its structure is isotypic with that of Na₄Mn(MoO₄)₃. It is formed by Cu₂O₁₀ distorted bi-octahedral dimers linked by two bridging bidentate Mo₂O₄ tetrahedra and, additionally, two monodentate Mo₁O₄ tetrahedra to form Cu₂Mo₄O₂₀ units. These units are linked by the insertion of Mo₃O₄ tetrahedra to build infinite ribbons disposed along the c axis. All of these ribbons form a one-dimensional framework. Both K1 and K3 cations are located in the inversion center, and all the other atoms are at general positions. The structure model is supported by the bond valence sum (BVS) and charge distribution CHARDI methods. The Cu²⁺ cations adopt the [4+2] CuO₆ Jahn-Teller distortion giving rise to an intense d–d transition in the UV-vis absorption spectra.     

Thermal expansion of phases formed in the system Nb2O5-MoO3

Studies on thermal expansion of phases formed in the system Nb₂O₅-MoO₃ (WO₃) have been carried out in the high-temperature X-ray diffraction attachment. In the case of Nb₁₄Mo₃O₄₄, Nb₁₂MoO₃₃ and Nb₁₂WO₃₃ the structure that consists of ReO₃ type blocks, the direction of minimal thermal expansion is consistent with direction in which the chains of corner-sharing polyhedra spread to infinity. On the contrary, for Nb₂Mo₃O₁₄, the structure of which resembles the structure of tetragonal tungsten bronzes, the maximal thermal expansion direction is consistent with above mentioned direction. This revised version was published online in July 2006 with corrections to the Cover Date.     

Structure and properties of solid solutions based on bismuth niobate Bi<Subscript>3</Subscript>NbO<Subscript>7</Subscript>

Solid solutions Bi₃Nb_1–yW_yO_{7 ± δ}, Bi₃Nb_1–yV_yO_{7 ± δ}, Bi₃Nb_1–yFe_yO_{7 ± δ} (y = 0.1–0.5; Δy = 0.1), and Bi_3–xY_xNb_1–yW_yO_{7 ± δ} (x = 0.05, 0.1; y = 0–0.3; Δy = 0.1) have been studied. The homogeneity ranges of the solid solutions and crystal-chemical parameters have been determined by means of X-ray powder diffraction. The electrical conductivity of sintered samples has been studied by impedance spectroscopy. The joint introduction of yttrium and tungsten into the niobium sublattice does not lead to an increase in the conductivity of solid solutions, and the change of the dopant type has no noticeable effect on this conductivity.     

Subsolidus phase relations in the Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-Li<Subscript>2</Subscript>O-Ta<Subscript>2</Subscript>O<Subscript>5</Subscript> (Nb<Subscript>2</Subscript>O<Subscript>5</Subscript>) systems

The phase composition has been studied and an equilibrium phase diagram has been designed for the Al₂O₃-Li₂O-R₂O₅ (R = Ta or Nb) systems in the subsolidus region up to 1000°C and 85 mol % Li₂O. New phases with the composition Li_1+x Al_1?x O_2?x , where x = 0–0.67, have been found.     

A New Molybdophosphate Constructed From {Mo<Stack><Subscript>2</Subscript><Superscript>V</Superscript></Stack>O<Subscript>4</Subscript>(H<Subscript>2</Subscript>O)<Subscript>6</Subscript>}<Superscript>2+</Superscript> and 1-Hydroxyethylidenediphosphonate

A new molybdophosphate (NH₄)₈{Mo₂^VO₄[(Mo₂^VIO₆)CH₃C(O)(PO₃)₂]₂}·14H₂O (1), has been synthesized by the reaction of {Mo₂^VO₄(H₂O)₆}²⁺ fragments with 1-hydroxyethylidenediphosphonate (hedp HOC(CH₃)(PO₃H₂)₂), and it is characterized by ³¹P NMR, IR, UV, element analysis, TG and single-crystal X-ray analysis. The structure analysis reveals that the polyoxoanion can be described as two {(Mo₂^VIO₆)(CH₃C(O)(PO₃)₂} units connected by a {Mo₂^VO₄}²⁺ moiety. In the structure, the six Mo atoms are arranged into a new “W-shaped” structure, which represents a new kind of molybdophosphate.     

Crystal structure of a cobalt oxide LuBaCo<Subscript>4</Subscript>O<Subscript>7</Subscript>

Crystals of LuBaCo₄O_7+δ (114Lu) have been obtained by spontaneous crystallization of slowly cooled nonstoichiometric melt of the system Lu-Ba-Co-O. The crystals have been characterized by EDX microprobe and synchrotron radiation powder diffraction. Structure refinement has been carried out (automated diffractometer Bruker X8 APEX with a CCD detector, MoK _α, graphite monochromator, ?_max = 32.54°). Parameters of the hexagonal unit cell: space group P6₃ mc, a = 6.2601(1) Å c = 10.2017(3) Å V = 346.23(1) Å₃, Z = 2, d _calc = 6.331 g/cm₃. Framework structure of the wurtzite type has been refined anisotropically to R-factor 0.0174. Charge balance in the compound and geometrical matching of structural fragments are discussed.