Synthesis of the titanium phosphide telluride Ti2PTe2: A thermochemical approach

The phosphide telluride Ti₂PTe₂ can be synthesised from the elements or from oxides in a thermite type reaction. Both ways have been optimised by consideration of the thermodynamic behaviour of the compound. Hence, the investigation of phase equilibria in the ternary system Ti/P/Te and of the thermal decomposition of Ti₂PTe₂ was necessary. This investigation was performed by using different experimental approaches as total pressure measurements, thermal analysis and mass spectrometry. The results were supported and further analysed by thermodynamic modelling of the ternary system. It was shown that Ti₂PTe_2(s) decomposes to Ti₂P_(s) and Te_2(g) in six consecutive steps. The growth of single crystals of Ti₂PTe₂ is thermodynamically described as a chemical vapour transport with TiCl_4(g) acting as the transport agent.     

Zum magnetischen Verhalten von SmCl2

On the Magnetic Behaviour of SmCl₂ Crystals of SmCl₂ were prepared by chemical vapour transport from a mixture of SmCl₃, samarium powder, and AlCl₃. The dichloride was investigated by magnetic measurements in the temperature range of 2 K to 300 K. The magnetic data were interpreted theoretically with a previous developed model, where the influence of the crystal field is described by the angular overlap model.     

Zum chemischen Transport von Wolfram mit HgBr2 – Experimente und Modellrechnungen

On the Chemical Transport of Tungsten using HgBr₂ – Experiments and Thermochemical Calculations Using HgBr₂ as transport agent tungsten migrates in a temperature gradient from the region of higher temperature to the lower temperature (e.g. 1 000 → 900°C). The transport rates were measured for various transport agent concentrations (0.64 ? C(HgBr₂) ? 11.74 mg/cm³; T? = 950°C) and for various mean transport temperatures (800 ? T? ? 1 040°C). Under these conditions tungsten crystals were observed in the sink region. To observe the influence of tungsten dioxide (contamination of the tungsten powder) on the transport behaviour of tungsten, experiments with W/WO₂ as starting materials were performed. According to model calculations the following endothermic reactions are important for the migration of tungsten: In the presence of H₂O or WO₂ other equilibria play a role, too. Using a special “transport balance” we observed a delay of deposition of tungsten (e.g. T? = 800°C; 15 h delay of deposition) with W and W/WO₂ as starting materials. The heterogeneous and homogeneous equilibria will be discussed and an explanation for the non equilibrium transport behaviour of tungsten will be given.     

Zum chemischen Transport von Bismutoxidhalogeniden BiOX (X = Cl,Br, I) mit Halogen,Halogenwasserstoff sowie Wasser und Bestimmung der Molwärmen von BiOX

Chemical Transport of Bismuth Oxide Halides BiOX (X = Cl, Br, I) with X₂, HX and H₂O, and Determination of the Molar Enthalpies of BiOX By comparison of calculated and experimental chemical transport behaviour of BiOX (X = Cl, Br, I) with X₂, HX, and H₂O it was shown, that we understand the transport of BiOCl, BiOBr and BiOI with X₂ and HX in terms of the well known gaseous spezies in the systems. The existence of gaseous complexes Bi(OH)₂X is be concluded from high transport rates of BiOX with water, and their enthalpies and entropies were derived. The molar enthalpies and standard entropies of BiOX were determined by low temperature C_p measurements. (Data see Inhaltsübersicht)     

Greedy Ag(II) oxidizer: Can any inorganic ligand except fluoride endure its presence in ionic solids?

The available thermodynamic data for a variety of oxides, chlorides and fluorides of various elements and for the AgF₂/AgF, AgF₂/Ag₂O redox pairs are analyzed in detail. We show that AgF₂ is capable of oxidizing a vast majority of oxides and chlorides with the concomitant evolution of O₂ or Cl₂, respectively. Interesting cases are discussed of the inertness of sulfates, perchlorates and nitrates against AgF₂. In addition, perfluorinated amines should not be susceptible to oxidation and they might form complexes with Ag^II. The DFT calculations support the view that Ag^II transfers substantial share of d⁹ hole into the oxide and chloride bands in hypothetical model compounds.     

A Quantum Chemical Study of Bismuth Compounds Thermodynamic Properties and Configuration of Pentacoordinated Organobismuth Molecules

By the PM3 method, standard values of entropy, heats, and free energies of formation have been computed for a series of inorganic and organic bismuth compounds. Linear dependences P exper = b P theor (where P is any of the mentioned properties) have been stated, allowing a priori evaluation of thermodynamic characteristics of Bi-containing substances. A quantum chemical calculation reproduces well the adiabatic ionization potential of BiH 3 . Triphenyldichlorobismuth and triphenyldinitratobismuth existence in benzene solutions in the form of trigonal bipyramid with two axial chloro and nitrato ligands has been concluded.     

A new molecular precursor route for the synthesis of Bi-Y, Y-Nb and Bi-doped Y-Nb oxides at moderate temperatures

Yttrium-based multimetallic oxides containing bismuth and/or niobium were prepared by a method starting from pre-isolated stable water-soluble precursors which are complexes with the ethylenediaminetetraacetate ligand (edta). The cubic Bi_1−xY_xO_1.5 (x=0.22, 0.25 and 0.3) and Y₃NbO₇ oxides were obtained in a pure form in a range of moderate temperatures (600-650 °C). This preparation method also allowed to stabilize at room temperature, without quenching, the tetragonal YNbO₄ oxide in a distorted form (T′-phase) by calcining the precursor at 800 °C. When heated up to 1000 °C, this metastable T′-phase transforms into the metastable “high-temperature” T oxide, which converts on cooling down to room temperature into the thermodynamically stable monoclinic M oxide. Doping the YNbO₄ oxide with Bi³⁺ cations (0.5% and 1% Bi with respect to total Bi+Y amount) led at 800 °C to a mixture of the T′-phase and the thermodynamically stable monoclinic one. At 900 °C, the almost pure monoclinic structure was obtained.     

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.