Verres du systeme La2S3La2O3Ga2O3Ga2S3

The extent of the glass forming region is described as a function of the composition and of the cooling speed. The shape of this region is explained from the previously described La₂S₃La₂O₃Ga₂O₃Ga₂S₃ phase diagram. Glasses are obtained after relatively slow cooling (5°/min), in a definite region of compositions, which coincides with a relatively large concentration of ternary invariants. The thermal properties (transition temperatures and crystallization temperatures) were measured by DTA. For a relatively large region of compositions, glasses return to the equilibrium conditions with intermediate formation of the La_3.33Ga₆S₁₂O₂ metastable crystalline phase. An approach to the structure of the glasses is made by comparison with the crystal structures of the numerous ternary and quaternary crystalline compounds observed in the system, and by the comparison of the Raman spectra. It appears that these gallium oxysulfide glasses have many structural analogies with germanium sulfide glasses.     

Phase equilibria in the ternary system: MgONa2OP2O5: Partial system: Mg3(PO4)2Mg4Na(PO4)3Na4P2O7Mg2P2O7

The partial system Mg₃(PO₄)₂Mg₄Na(PO₄)₃Na₄P₂O₇Mg₂P₂O₇ in the ternary system MgONa₂OP₂O₅ was investigated using thermal and X-ray diffraction analyses and microscopy, and its phase diagram has been determined. In this range of composition, two binary phosphates occur: Mg₄Na(PO₄)₃ and Mg₆Na₈(P₂O₇)₅. The former melts incongruently (at 1155°C) and the latter does congruently (at 808°C). In the partial system of interest, the two sections Mg₄Na(PO₄)₃Mg₂P₂O₇ and Mg₄Na(PO₄)₃Mg₆Na₈(P₂O₇)₅ are studied, and their phase diagrams are established. The partial system is divided into three partial ternary systems in which two ternary eutectics and one ternary peritectic occur.     

New oxyborates in the MgMnBO system

Two new oxyborate compounds were synthesized during a study of the phase relationships between the pinakiolite-ludwigite series of compounds. The structural topologies of these previously unreported materials have been determined experimentally by comparing calculated with observed electron microscope images. Both of these structures are very similar to each other, and also closely related to pinakiolite which consists of flat walls of edge-sharing octahedra connected to zigzag chains of octahedra by triangular BO₃ groups. The two new structures contain similar infinite walls which are separated by slabs of octahedra that are wider than the zigzag chains found in pinakiolite. A new series of structurally related oxyborate compounds can be envisaged and are described.     

The system YPO4Ca3(PO4)2Ca2P2O7

The ternary system YPO₄Ca₃(PO₄)₂Ca₂P₂O₇ has been investigated by differential thermal analysis, powder X-ray diffraction, and microscopy in reflected light. Its phase diagram and isothermal section at room temperature have been determined. The system contains only one double phosphate which is formed at the 1:1 molar ratio YPO₄:Ca₃(PO₄)₂, i.e., Ca₃Y(PO₄)₃.     

Phase diagram for the system Bi2O3CaOSrOCuO in the SrO-rich region

It has been found experimentally that phase diagram for the system Bi₂O₃CaOSrOCuO in SrO-rich region at 850°C in the open air includes three elementary tetrahedra: CaOSrOSr₆Bi₂O₁₁Sr₂CuO₃, CaOSr₂CuO₃Sr₆Bi₂O₁₁Sr_3,5Ca_0,5Bi₂O₇ and Sr₃Bi₂O₆Sr₆Bi₂O₁₁Sr_3,5Ca_0,5Bi₂O₇ Sr₂CuO₃. In the considered interval of corresponding oxide concentrations quaternary oxides are not formed under the above conditions.     

The oxygen potentials corresponding to the YBa2Cu3O6+x phase in the YBaCuO system

Phase relations in the vicinity of the YBa₂Cu₃O_6+x in the CuO-rich part of the YBaCuO system were studied by the equilibration and quenching technique. At 950°C, the system is characterized by the large number of solid four-phase combinations. The oxygen potential as a function of temperature for two four-phase combinations, i.e., YBa₂Cu₃O_6+x + BaCuO₂ + BaCu₂O₂ + Y₂BaCuO₅ and YBa₂Cu₃O_6+x + BaCu₂O₂ + Y₂BaCuO₅ + Cu₂O, were studied by means of solid state EMF measurements. At higher oxygen potentials the pair of YBa₂Cu₃O_6+x and Y₂BaCuO₅ is stable in contact with BaCuO₂. At lower oxygen pressures this pair coexists in equilibrium with BaCu₂O₂ or Cu₂O.     

The thermal transformation of Na LiA zeolites. A new polymorph in the system Li2OAl2O3SiO2

High-temperature phase transformations of A zeolite with various degrees of exchange of Na⁺ with Li⁺ ions were investigated. An increase in the number of Li⁺ ions per unit cell accelerates the thermal transformation of the zeolite framework to the amorphous state. Above 730°C, four phases (carnegieite, nepheline, β-eucryptite, and a new phase—γ-eucryptite) were identified. Only γ- and β-eucryptite phases were obtained from pure LiA zeolite. γ-eucryptite is a new metastable polymorph in the system Li₂OAl₂O₃SiO₂. γ-eucryptite a₀ = 7.231(3)Å, b₀ = 10.270(6) Å, c₀ = 12.054(7) Å) is transformed to β-eucryptite (a₀ = 10.533(5) Å, c₀ = 11.148(5) Å) above 840°C.     

High-Tc superconductivity in the ErBaCuO and related systems

ErBa₂Cu₃O₇ and Er_0.5Y_0.5Ba₂Cu₃O₇ are both high-T_c superconductors attaining zero resistance above 80 K. Preliminary studies indicate that Yb_1−xY_xBa₂Cu₃O₇ also exhibits zero resistance above 77 K.     

Phase equilibrium diagram of the system MnCrO

A hypothetical oxygen pressure-composition phase diagram and a projection of the oxygen pressure-temperature-composition diagram on the composition triangle were constructed from phase equilibria in the system MnCrO on the basis of the data available in literature. The temperature-composition phase equilibrium diagram of this same system in air was specified. Isomorphism of solid solutions with spinel and hausmannite structure and their intertransformation was studied. Two chemical compounds, MnCr₂O₄ and Cr₄Mn₂₈O₄₈, are supposed to exist in the system.     

Proton-ionizable crown compounds : 5. Macrocycle-mediated proton-coupled transport of alkali metal cations in H2OCH2Cl2H2O liquid membrane systems

Alkali cation transport is studied using proton-ionizable macrocycle carriers of the 4-hydroxypyridine and pyridone types in a bulk H₂OCH₂Cl₂H₂O liquid membrane system as a function of source and receiving phase pH. A pyridone crown-6 type macrocycle containing an octyl substituent (3) transports Li⁺, Na⁺, K⁺, Rb⁺ and Cs⁺ from MOH solutions by a proton-coupled mechanism in which no co-anion is transported. In these cases, alkali cation transport increases exponentially with increasing source phase pH above pH 12. Generally, alkali cation transport at source phase pH 14 is higher when nitric acid is present (receiving pH = 1.5) than when it is absent. In competitive transport experiments with macrocycle 3 involving K⁺) and one other alkali cation M⁺, K⁺ is transported selectively over M⁺ by 4.6 (Na⁺), 2.7 (Rb⁺) and 6.3 (Cs⁺) fold when the source and receiving phase pH values are 14 and 7, respectively.     

An investigation of the polythermal diagram of the H2ONa2HPO4Na2SO4 system

The polythermal diagram of the ternary system H₂ONa₂HPO₄Na₂SO₄ has been established, setting up nine isotherms obtained between 0 and 25°C by conductimetric analysis. The solubility domains of the various solid phases have been determined. One eutectic, three stable and one metastable transitional transformations have been observed. Temperature and composition of the eutectic point have been obtained by thermal analysis at constant flow.     

Importance of axial ligand in meso-tetraphenylporphinatoiron(III) promoted NO and OO bonds cleavages

Amines, especially imidazole, were found to be essential in the meso-tetraphenylporphinatoiron (III) promoted demethylation of N, N-dimethylaniline N-oxide through the Polonovski type reaction and in the cumene hydroperoxide dependent oxidative demethylation of N, N-dimethylaniline in dichloromethane. When benzenethoil was used instead of these amines, deoxygenation of N, N-dimethylaniline N-oxide took place very readily     

Magnetic susceptibilities of UO2ThO2ZrO2 solid solutions

Magnetic susceptibilities were measured from 2.2 K to room temperature for solid solutions of UO₂ThO₂ZrO₂ of which the lattice parameters are the same as that of UO₂, i.e., Th_0.7yZr_0.3yU_1−yO₂ solid solutions. The Néel temperature decreases linearly with decreasing uranium concentration, the critical concentration being 69 mole% UO₂. The Néel temperatures of the present solid solutions are nearly in the middle of UO₂ThO₂ solid solutions and UO₂ZrO₂ solid solutions, which indicates that the magnetic dilution effect of ZrO₂ is larger than that of ThO₂. The effective magnetic moment decreases with decreasing uranium concentration, which is due to a decrease in the magnetic interactions with adjacent uranium ions, not due to a change of the strength of crystalline field. The Weiss constant decreases almost linearly with decreasing uranium concentration.     

Phase diagram and IR spectral investigations of the 2TeO2 · V2O5Li2O · V2O5 · 2TeO2 system

By means of X-ray phase analysis, IR spectroscopy, and DTA, the system 2TeO₂ · V₂O₅Li₂O · V₂O₅ · 2TeO₂ was investigated and its phase diagram was constructed. The formation of a new compound with composition Li₂O · 3V₂O₅ · 6TeO₂, melting incongruently was documented. A comparison of the bands in the IR spectrum was made. Stable glasses in the whole range of concentrations were prepared. From the IR spectra of the glasses, the corresponding crystallization products, and the data of known crystal structures, a model of the short-range order in the glasses was proposed.     

Bubble-point pressures of the H2COCO2 system

Bubble-point pressures of the H₂COCO₂ system were measured at temperatures from 253.15 to 303.15 K and pressures up to 9 MPa. Multiple bubble-points were observed within certain limits of hydrogen compositions. The data have been compared with the calculated results by the Redlich-Kwong and the Peng-Robinson equations of state.     

Investigation of nonstoichiometry and ferroelectric properties in the ternary system Li2OTa2O5(WO3)2 at 1250°C under atmospheric pressure

X-ray crystallographic studies conducted at atmospheric pressure have allowed determination of the limits of solid solutions with LiTaO₃ structure in the ternary system Li₂OTa₂O₅(WO₃)₂. Stoichiometry analysis has shown that the prevailing type of nonstoichiometry of these phases is simultaneous cationic and anionic deficits. Dielectric measurements carried out on the ceramic samples showed a decrease in the ferroelectric Curie temperature as the composition deviates from that of pure LiTaO₃.