Chemischer Transport ternärer Cadmiummolybdate

Chemical Vapor Transport of Ternary Cadmium Molybdates The ternary phase diagram Cd/Mo/O at 923 K have been investigated. Single crystals of CdMoO₄ and Cd₂Mo₃O₈ have been obtained via chemical vapor transport using X₂ and NH₄X (X = Cl, Br, I) as transport agent. Deposition rates are very different: up to 10 mg/h for CdMoO₄, maximum 10^–3 mg/h for Cd₂Mo₃O₈. The observed transport behaviour is compared with results of thermodynamical model calculations. The influence of source composition, transport agent and temperature gradient is described in detail.     

Zum Chemischen Transport im System Mg/Mo/O ‐ Experimente und Modellrechnungen

On the Chemical Vapour Transport in the Mg/Mo/O System ‐ Experiments and Model Calculations Single crystals of MgMoO₄ and Mg₂Mo₃O₈ have been obtained via chemical vapour transport in a temperature gradient 1273 to 1173 K using Cl₂ and Br₂ as transport agents. Pure powders of the ternary compounds have been used as starting materials as well as mixtures of three coexisting phases. The observed transport behaviour is compared with results of thermodynamical model calculations. The influence of source composition, transport agent and the moisture contents is described in detail.     

Chemischer Transport ternärer Oxide in den Systemen Ca/Mo/O und Sr/Mo/O

Chemical Vapour Transport of Ternary Oxides in the Systems Ca/Mo/O and Sr/Mo/O The chemical vapour transport behaviour of ternary phases in the Ca/Mo/O and Sr/Mo/O systems has been investigated using Cl₂ as transport agent in a temperature gradient 1423 to 1323 K. MMoO₄ (M= Ca, Sr) migrate in the above‐mentioned temperature gradient with rates of 0.1 to 0.2 mg/h. Starting from three phase mixtures crystals of the compounds MMo₅O₈ have been grown (migration rates: M = Ca 0.1 mg/h, M = Sr 0.01 mg/h). The observed transport behaviour is compared with predictions given by thermo dynamical model calculations and the influences of source composition and the moisture contents are described in detail.     

Synthesen,IR- und 15N-Kernresonanzspektren isotopen-markierter Nitridokomplexe des Wolframs

Isothermal Section at 1273 K in the System Ti? Si? O The isothermal section at 1273 K of the system Ti? Si? O has been investigated by means of phase analysis in quenched samples as well as by the investigation of the phase sequence in chemical vapour transport experiments. In equilibrium with SiO₂ only TiSi₂, TiSi, and Ti₅Si₃(O), respectively, can coexist as Si-containing compounds. Only Ti₅Si₃(O) can coexist with titanium oxides (Ti₂O₃ or TiO, respectively). Ti₅Si₄ is stable only if oxygen is absent.     

Zum Chemischer Transport ternärer Übergangsmetall‐ und Erdalkaliwolframate MWO4 mit Chlor

On the Chemical Vapor Transport of Ternary Transition Metal‐ and Earth Alkaline Tungstates MWO₄ with Chlorine The chemical vapor transport of transition metal tungstates MWO₄ (M=Mn, Co, Ni, Cu, Zn, Cd) was investigated in dependence on mean transport temperature (923 K to 1223 K) and amount of transport agent Cl₂. All tungstates migrate in a temperature gradient ΔT = 100 K from the region of higher temperature to the lower temperature with migration rates of 0.5 to 8 mg/h depending on experimental conditions. The transport behaviour was determined by continuous measurement of mass change during the transport experiments. The results were compared to thermo chemical calculations and the influence of moisture content discussed in detail. MgWO₄ migrates under the influence of Cl₂ in a temperature gradient 1273 K to 1173 K (migration rate 0.7 mg/h), CaWO₄ and SrWO₄ in a temperature gradient 1423 K to 1323 K (migration rate <0.1 mg/h).     

Koexistenzbeziehungen,Darstellung und Eigenschaften ternärer Phasen im System Cu/Mo/O

Coexistence Relations, Preparation and Properties of Ternary Compounds in the System Cu/Mo/O The phase diagram of the ternary system Cu/Mo/O is presented at 773 K. The compounds CuMoO₄, Cu₃Mo₂O₉, Cu₄Mo₅O₁₇, Cu₆Mo₅O₁₈, Cu_4–xMo₃O₁₂, and Cu_xMoO₃ are found to be thermodynamical stable. The homogeneity range of Cu_4–xMo₃O₁₂ runs to x = 0.1–0.2. Single crystals of CuMoO₄ and Cu₃Mo₂O₉ were grown by chemical transport reactions with TeCl₄, Cl₂, HCl, and Br₂ as transport agent. The results were compared with thermochemical calculations. The decomposition of CuMoO₄ and Cu₃Mo₂O₉ was investigated with thermal analysis and decompositon pressure measurements.     

Multi-component catalysts with spinel structure for the selective reduction of nitrogen oxide by ethylene in lean-exhaust gas streams

The Ga₂O₃-Al₂O₃-ZnO (GAZ) multi-component spinel powders with incorporated Cu²⁺, Co²⁺, Fe²⁺, Ni²⁺, Mn²⁺ and In²⁺ metal cations were synthesized by co-precipitation method from a mixed solution of nitrate salts. Spinel crystal structure of each composition was confirmed by XRD measurements. The multi-component oxide powders were tested in the reduction of nitrogen oxide (NO) under lean conditions. Among the catalysts tested, In₂O₃-containing GAZ with a pure spinel phase structure showed promising catalytic activity in the NO reduction in the presence of 10% H₂O vapor. In addition, the effect of H₂O vapor and SO₂ on the selective reduction of NO over In₂O₃-GAZ/cordierite and In₂O₃-GAZ/metal honeycombs catalysts has been investigated.     

Beiträge zur Kristallchemie und zum thermischen Verhalten von wasserfreien Phosphaten. XXXIII [1] In2P2O7, ein Indium(I)‐diphosphato‐indat(III) und In4(P2O7)3 — Darstellung,Kristallisation und Kristallstrukturen

Contributions on Crystal Chemistry and Thermal Behaviour of Anhydrous Phosphates. XXXIII [1] In₂P₂O₇ an Indium(I)‐diphosphatoindate(III), and In₄(P₂O₇)₃ — Synthesis, Crystallization, and Crystal Structure Solid state reactions via the gas phase lead to the new mixed‐valence indium(I, III)‐diphosphate In₂P₂O₇. Colourless single crystals of In₂P₂O₇ have been grown by isothermal heating of stoichiometric amounts of InPO₄ and InP (800 °C; 7d) using iodine as mineralizer. The structure of In₂P₂O₇ [P2₁/c, a = 7.550(1) Å, b = 10.412(1) Å, c = 8.461(2) Å, b = 105.82(1)°, 2813 independent reflections, 101 parameter, R1 = 0.031, wR2 = 0.078] is the first example for an In⁺ cation in pure oxygen coordination. Observed distances d(In^I‐O) are exceptionally long (d_min(In^I‐O) = 2.82 Å) and support assumption of mainly s‐character for the lone‐pair at the In⁺ ion. Single crystals of In₄(P₂O₇)₃ were grown by chemical vapour transport experiments in a temperature gradient (1000 → 900 °C) using P/I mixtures as transport agent. In contrast to the isostructural diphosphates M₄(P₂O₇)₃ (M = V, Cr, Fe) monoclinic instead of orthorhombic symmetry has been found for In₄(P₂O₇)₃ [P2₁/a, a = 13.248(3) Å, b = 9.758(1) Å, c = 13.442(2) Å, b = 108.94(1)°, 7221 independent reflexes, 281 parameter, R1 = 0.027, wR2 = 0.067].     

Chemischer Transport und Sauerstoffionenleitfähigkeit von Mischkristallen im System In2O3/SnO2

Chemical Transport of Solid Solutions. 8. Transport Phenomena and Ionic Conductivity in the In₂O₃/SnO₂ System Chemical transport reactions are a suitable pathway to the preparation of In₂O₃‐rich and SnO₂‐rich mixed crystals coexisting in the In₂O₃/SnO₂ system (Cl₂ as transport agent, 1050 → 900 °C). Experiments are consistent with thermodynamic calculations. The existence of other phases in the system In₂O₃/SnO₂ could not be confirmed. The ionic conductivity of In₂O₃(SnO₂) was investigated.     

Vapor pressure and dissociation energy of (In2O)

The vapor pressure of pure liquid indium, and the sum of pressures of (In) and (In₂O) species over the condensed phase mixture {In} + <In₂O₃>, contained in a silica vessel, have been measured by Knudsen effusion and Langmuir free vaporization methods in the temperatue range 600 to 950°C. Mass spectrometric studies reported in the literature show that (In) and (In₂O) are the important species in the vapor phase over the {In} + <In₂O₃ >; mixture. The vapor pressure of (In₂O) corresponding to the reaction,

deduced from the present measurements is given by the equation,

The “apparent evaporation coefficient” for the condensed phase mixture is approximately 0.8. The energy for the dissociation (In₂O) molecule into atoms calculated from the above equation is D°₀ = 180.0 (± 1.0) kcal mol^?1.     

Darstellung,Kristallstruktur und Eigenschaften des Kupfer(II)‐Indium(III)‐Orthophosphats Cu3In2[PO4]4

Contributions on Crystal Chemistry and Thermal Behaviour of Anhydrous Phosphates. XXIV. Preparation, Crystal Structure, and Properties of Copper(II) Indium(III) Orthophosphate Cu₃In₂[PO₄]₄ Crystals of Cu₃In₂[PO₄]₄ were grown by chemical vapour transport (temperature gradient 1273 K → 1173 K) using chlorine as transport agent. The mixed metal phosphate forms a new structure type (P2₁/c, Z = 2, a = 8.9067(6), b = 8.8271(5), c = 7.8815(5) Å, β = 108.393(5)°, 13 atoms in asymmetric unit, 2549 unique reflections with F_o > 4σ, 116 variables, R(F²) = 0.065). The crystal structure shows a hexagonal closest packing of [PO₄]^3– tetrahedra. Close‐packed layers parallel (1 0 –1) are stacked according to the sequence A, B, A′, B′, A. The octahedral interstices in this packing are completely occupied by two In³⁺, one (Cu1)²⁺ and a “dumb bell” (Cu2)₂⁴⁺. In the latter case four of the six phosphate groups that belong to this octahedral void act as bi‐dentate ligands, thus forming dimers [(Cu2)₂O₁₀] with d_Cu–Cu = 3.032 Å. Cu₃In₂[PO₄]₄ is paramagnetic (μ_eff = 1.89 μ_B, θ_P = –16.9 K). The infrared and UV/Vis reflectance spectra are reported. The observed d‐electron levels of the Cu²⁺ cations agree well with those obtained from angular overlap calculations.     

Thermodynamic Properties of silicate glasses and melts: VIII. System MgO-Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-SiO<Subscript>2</Subscript>

Vaporization of the system MgO-Al₂O₃-SiO₂ in the temperature range 1770–1890 K was studied and activities of MgO and SiO₂ were determined. Activities of the components, isothermal sections of the phase diagram, and the position of the liquidus line in the studied system were calculated using the Gay-Kapoor-Frohberg model. The correlation of the found values of thermodynamic properties and phase equilibriua in isothermal sections of the phase diagram of the studied system was illustrated.     

Thermal stability of In2(MoO4)3 and phase equilibria in the MoO3–In2O3 system

Thermal stability of a compound forming in a binary system MoO₃?CIn₂O₃ was investigated by DTA/TG, XRD and SEM methods in this study. For the first time, the diagram of phase equilibria established in the whole range of concentrations of this system's components has been constructed. The temperature and concentration ranges of the components of MoO₃?CIn₂O₃ system in which the compound In₂(MoO₄)₃ co-exists in solid state with MoO₃ or In₂O₃ or with the liquid were determined. The composition and melting point of the eutectic mixture consisting of In₂(MoO₄)₃ and MoO₃ were found.     

Zur Kenntnis des quaternären Systems Zn?In?S?Se Der Schnitt ZnIn2S4?Znln2Se4?In2S3?In2Se3

The Quaternary System ZnIn₂S₄? ZnIn₂Se₄? In₂Se₃? In₂S₃ The title system has been investigated on the indium rich side (ratio In/Zn ≥ 2) on samples quenched from 800°C to room temperature using x-ray methods. In this section 7 different phases could be identified the phase borders of which are given. ZnIn₂S₄-type and thiogallate type mixed crystals only show a small region of homogeneity while the monophase region of spinel type mixed crystals in the indiumsulfide rich part of the phase diagram has a larger extension. There is a new trigonal compound ZnIn₂S₂Se₂ (a_hex = 3.937, c_hex = 31.97 Å) with a large region of homogeneity. In the indiumselenide rich part there are two new phases: (i) Zn_0.4In₂Se_3.4 with unknown structure and (ii) a ternary phase of unknown structure in the system In₂S_3?xSe_x for 2.1 ≤ x ≤ 2.7.     

Laux‐type Oxidation of In0 Nanoparticles to In2O3 Retaining Particle Size and Colloidal Stability

As a conceptual study, In⁰ nanoparticles are obtained by NaBH₄‐driven reduction of InCl₃ · 4H₂O and transferred from a polar/hydrophilic diethylene glycol phase to a non‐polar hydrophobic dodecane phase for purification and stabilization. Finally, the In⁰ nanoparticles are oxidized via a Laux‐like reaction with nitrobenzene to In₂O₃ nanoparticles. The challenge of the reaction is to perform the final oxidation to In₂O₃ under mild conditions with the colloidal stability, particle size and particle size distribution of the initial In⁰ nanoparticles retained. To this concern, the mean diameter of the initial In⁰ nanoparticles changed from 11(1) to 14(2) nm of the oxidized In₂O₃ nanoparticles. Such multi‐step reaction, including reduction, nucleation, phase transfer, exchange of surface capping and oxidation are of increasing importance for nanoparticles. Especially, Laux‐type conditions with nitrobenzene as a molecular oxidizing agent of nanoparticles have not been used till now. Particle size, size distribution and chemical composition of the In⁰ and In₂O₃ nanoparticles are analyzed by DLS, SEM, XRD, FT‐IR and HRTEM.     

Chemischer Transport fester Lösungen. 11 [1] Mischphasen und Chemischer Transport in den Systemen CrIII/InIII/GeIV/O,GaIII/InIII/GeIV/O,MnIII/InIII/GeIV/O und FeIII/InIII/GeIV/O

Chemical Vapor Transport of Solid Solutions. 11 Mixed Phases and Chemical Vapor Transport in the Systems Cr^III/In^III/Ge^IV/O, Ga^III/In^III/Ge^IV/O, Mn^III/In^III/Ge^IV/O und Fe^III/In^III/Ge^IV/O By means of chemical vapor transport methods the following mixed phases have been prepared: Cr_{0, 18}In_{1, 82}Ge₂O₇ (Cl₂, 950 → 850 °C), (Ga_{0, 6}In_{1, 4})₂Ge₂O₇ (Thortveitit‐type, Cl₂, 1050 → 950 °C), (Ga_{1, 9}In_{0, 1})₂Ge₂O₇ (Ga₂Ge₂O₇‐type, 1050 → 950 °C), (In_{1, 9}Mn_{0, 1})₂Ge₂O₇ (Thortveiti‐type, Cl₂, 1000 → 800 °C), mixed phase crystallizing in the Mn₂Ge₂O₇‐structure showing a composition near MnInGe₂O₇ (Cl₂, 1000 → 800 °C), Mn_{6, 5}In_{0, 5}GeO₁₂ (Braunit‐type, Cl₂, 1000 → 800 °C), (Fe_xIn_1‐x)Ge₂O₇ (Thortveitit‐type with x = 0…0, 94; Cl₂, 840 → 780 °C). Changing the compositions of the starting materials showed no effect on the composition of the deposit except for the system Fe₂O₃‐In₂O₃‐GeO₂.     

Revealing the Chemical State of Palladium in Operating In2O3 Gas Sensors: Metallic Pd Enhances Sensing Response and Intermetallic InxPdy Compound Blocks It

The sensing response of metal oxides activated with noble metal nanoparticles is significantly influenced by changes to the chemical state of corresponding elements under operating conditions. Here, a PdO/rh-In₂O₃ consisting of PdO nanoparticles loaded onto rhombohedral In₂O₃ was studied as a gas sensor for H₂ gas (100–40000 ppm in an oxygen-free atmosphere) in the temperature range of 25–450 °C. The phase composition and chemical state of elements were examined by resistance measurements combined with synchrotron-based in situ X-ray diffraction and ex situ X-ray photoelectron spectroscopy. As found, PdO/rh-In₂O₃ undergoes a series of structural and chemical transformations during operation: from PdO to Pd/PdH_x and finally to the intermetallic In_xPd_y phase. The maximal sensing response (R_N2/R_H2) of ∼5 ⋅ 10⁷ towards 40000 ppm (4 vol %) H₂ at 70 °C is correlated with the formation of PdH_0.706/Pd. The In_xPd_y intermetallic compounds formed around 250 °C significantly decrease the sensing response.     

Untersuchungen zum chemischen Transport im System V2O3/VO2

Investigation of Chemical Transport in the V₂O₃/VO₂ System The suitability of the transport agent HgCl₂ for chemical transport experiments (temperature gradient 1 173/1 113 K) in the system V₂O₃/VO₂ has been investigated. For a constant admixture of transport agent it could be observed that the transport rate, starting with V₃O₅, increases with increasing ratio O/V for the Magnéli-phases V_nO_2n–1 of this system (n′(V₃O₅) = 6 mg/d to n′(V₉O₁₇) = 20 mg/d), while the values for n′ = 12 mg/d are even for V₂O₃ and VO₂.     

Über die Kristallstruktur von In3Mo11O17 sowie über physikalische Eigenschaften oligomerer Oxomolybdate

On the Crystal Structure of In₃Mo₁₁O₁₇ and the Physical Properties of Oligomeric Oxomolybdates In₃Mo₁₁O₁₇ is characterized by its molybdate framework Mo₂₂O₃₄^8? belonging to the general series Mo_4n+2O_6n+4^x? (with n = 5). The phase grows in star-like aggregates and crystallizes within the orthorhombic system (a = 988.0(2) pm, b = 951.2(2) pm, c = 3 176.7(4) pm). There are oligomeric clusters built from five trans edge-sharing Mo₆ octahedra, surrounded by O atoms over all empty edges according to the Aufbau principle Mo₂₂OOO. In the remaining structural channel one finds an In₆⁸⁺ polycation which is geometrically equivalent with the one of In₁₁Mo₄₀O₆₂. The Mo—O and Mo—Mo distances within the cluster are the same like in In₁₁Mo₄₀O₆₂, too, but there are shorter inter cluster distances (306 pm) in In₃Mo₁₁O₁₇. Disorder in the structure may be understood in terms of the presence of constitutional isomers. While the electrical resistivity of PbMo₅O₈ resembles the one of a strongly disturbed metal (with a local minimum around 120 K), the temperature characteristic of Tl_0.8Sn_0.6Mo₇O₁₁ is typical for a semiconductor. Oxomolybdates with even longer oligomers like In₁₁Mo₄₀O₆₂ and In₃Mo₁₁O₁₇ show metallic conductivity. This course corresponds with the sizes of the clusters and their electronic intercoupling which can be estimated from the specific lengths of the inter cluster distances. The effective magnetic moment grows with increasing cluster length from 0.97 μ_B (PbMo₅O₈) to 1.40 μ_B (In₁₁Mo₄₀O₆₂) per cluster (exception: In₃Mo₁₁O₁₂), and so does the contribution of the temperature-independent paramagnetism (from 890 to 2191 × 10^?6$ \frac{{{\rm emu}}}{{{\rm mol}}} $ per cluster). Thus, a single condensed octahedron carries roughly 440 × 10^?6$ \frac{{{\rm emu}}}{{{\rm mol}}} $ as a temperature-independent paramagnetism, similar to the M₆X₁₇ halide clusters. In₁₁Mo₄₀O₆₂ shows an interesting change in the temperature dependence of its magnetic suszeptibility.