Synthesis of complex sulfide phases BaSm<Subscript>2</Subscript>S<Subscript>4</Subscript>-Tm<Subscript>2</Subscript>S<Subscript>3</Subscript> and studies of their electrolytic properties

The possibility of synthesizing complex sulfide phases in the BaSm₂S₄-Tm₂S₃ system has been studied. Tm₂S₃ solid solutions were obtained with BaSm₂S₄ (CaFe₂O₄ structural type). The samples were identified by X-ray diffraction analysis and electron microscopy. The range of the solid solutions was determined. The total conductance was studied, and the conductance activation energy was calculated for samples with different dopant contents. The electrolytic properties of basic ternary sulfide and complex sulfide phases in the BaSm₂S₄-x mol % Tm₂S₃ system were investigated. A possible mechanism of defect formation was proposed.     

The 3Ga<Subscript>2</Subscript>S<Subscript>3</Subscript>-EuLaGa<Subscript>3</Subscript>S<Subscript>7</Subscript> system

The La₂S₃-Ga₂S₃-EuS system has been investigated along the 3Ga₂S₃-EuLaGa₃S₇ join by physicochemical methods (DTA, X-ray powder diffraction, microstructural analysis). is a quasi-binary eutectic-type section of the ternary system. Solubility on the base of both components has been revealed in the system. Solubility at room temperature is 3 mol % EuLaGa₃S₇ on the Ga₂S₃ side 1.5 mol % Ga₂S₃ and on the base of the EuLaGa₃S₇ compound. The coordinates of the eutectic point are 80 mol% EuLaGa₃S₇ and 1020 K.     

Synthesis of complex sulfide phases on the CaYb<Subscript>2</Subscript>S<Subscript>4</Subscript>-Y<Subscript>2</Subscript>S<Subscript>3</Subscript> quasibinary section and investigation of their structural and electrolytic properties

The possibility of synthesizing sulfide-conducting solid electrolytes in the CaYb₂S₄-Y₂S₃ quasibinary system is tested for the first time. The system is characterized by the X-ray diffraction analysis and the electron microscopy. The total conductivity of specimens is found by the conductometric method. The ionic and electronic transport numbers are determined based on the modified versions of the emf method and the Hebb-Wagner polarization method. The possible mechanism of defect formation is discussed.     

Phase equilibria in the La<Subscript>2</Subscript>S<Subscript>3</Subscript>-Bi<Subscript>2</Subscript>S<Subscript>3</Subscript>-La<Subscript>2</Subscript>O<Subscript>3</Subscript> ternary system

Phase equilibria in the La₂S₃-Bi₂S₃-La₂O₃ ternary system were studied by differential thermal, X-ray powder diffraction, and microstructure analyses. Phase diagrams of five vertical sections and a liquidus surface projection were plotted for the La₂S₃-Bi₂S₃-La₂O₃ system. The regions of primary crystallization of phases and coordinates of non- and monovariant equilibria were determined for the system.     

MnS-Pr<Subscript>2</Subscript>S<Subscript>3</Subscript> phase diagram

The MnS-Pr₂S₃ phase diagram is of the eutectic type with incomplete solubility based on the starting sulfides (MnS and Pr₂S₃). The extent of the MnS-based solid solution at 1470 K is 1 mol % Pr₂S₃. γ-Pr₂S₃ at 1470 K dissolves 23 mol % MnS, α-Pr₂S₃ at 1170 K dissolves 6 mol % MnS. The eutectic composition (30 mol % Pr₂S₃ at 1550 K) coincides with the value calculated from the Schroeder equation for the liquidus branch descending from MnS. A value of 64 kJ/mol was calculated for the heat of melting of Pr₂S₃ using the Schroeder equation.     

Character of interaction and glass formation in the TlAs<Subscript>2</Subscript>Se<Subscript>4</Subscript>-Tl<Subscript>3</Subscript>As<Subscript>2</Subscript>S<Subscript>3</Subscript>Se<Subscript>3</Subscript> system

The TlAs₂Se₄-Tl₃As₂S₃Se₃ system was investigated by physicochemical methods (DTA, X-ray powder diffraction, microstructural analysis), and its phase diagram was constructed. The TlAs₂Se₄-Tl₃As₂S₃Se₃ join is a quasi-binary internal section of the As-Tl-S-Se quaternary system. The solubility range of TlAs₂Se₄-based solid solutions is extended to 7 mol %, and the region of Tl₃As₂S₃Se₃-based solid solutions is extended to 15 mol %.     

Sm<Subscript>2</Subscript>S<Subscript>3</Subscript>-Sm<Subscript>2</Subscript>O<Subscript>3</Subscript> phase diagram

The Sm₂S₃-Sm₂O₃ phase diagram was studied by physicochemical methods of analysis from 800 K up to melting. Two oxysulfides are formed in the system: Sm₁₀S₁₄O with tetragonal crystal structure (space group I41/acd; unit cell parameters: a = 1.4860 nm, c = 1.9740 nm; microhardness: H = 4700 MPa; solid decomposition temperature: 1500 K) and Sm₂O₂S with hexagonal structure (space group P-3m1; a = 0.3893 nm, c = 0.6717 nm; H = 4500 MPa; congruent melting temperature: 2370 K). Within the extent of the Sm₂O₂S-based solid solution (61–70 mol % Sm₂O₃) at 1070 K, a singular point appears at the compound composition on property-composition curves. The eutectic coordinates: 23 mol % Sm₂O₃ and 1850 K; 80 mol % Sm₂O₃ and 2290 K.     

Determination of diffusion coefficients for sulfide ions in solid electrolytes on the basis of BaSm<Subscript>2</Subscript>S<Subscript>4</Subscript> and CaGd<Subscript>2</Subscript>S<Subscript>4</Subscript>

Coefficients of self-diffusion and coefficients of diffusion of the sulfur ion in solid electrolytes BaSm₂S₄ and CaGd₂S₄ are determined with recourse to methods of conductimetry and potentiostatic chronoamperometry. A vacancy mechanism for the defect formation in solid solutions on the basis of barium thiosamarate and calcium thiogadolynate is proposed.     

Kinetics and reaction mechanism of phenol hydroxylation catalyzed by La-Cu<Subscript>4</Subscript>FeAlCO<Subscript>3</Subscript>

The present work synthesizes La-Cu₄FeAICO₃ catalyst under microwave irradiation and characterizes its structure using XRD and IR techniques. The results show that the obtained La-Cu₄FeAICO₃ has a hydrotalcite structure. In the phenol hydroxylation with H₂O₂ catalyzed by La-Cu₄FeAICO₃, the effects of reaction time and phenol/H₂O₂ molar ratio on the phenol hydroxylation, and relationships between the initial hydroxylation rate with concentration of the catalyst, phenol, H₂O₂ and reaction temperature are also investigated in details. It is shown the phenol conversion can reach 50.09% (mol percent) in the phenol hydroxylation catalyzed by La-Cu₄FeAICO₃, under the reaction conditions of the molar ratio of phenol/H₂O₂1/2, the amount ratio of phenol/catalyst 20, reaction temperature 343 K, reaction time 120 min, 10 ml_ distilled water as solvent. Moreover, a kinetic equation of v = k[La-Cu₄FeAlCO₃][C₆H₅OH][H₂O₂]. and the activation energy of E _a=58.37 kJ/mol are obtained according to the kinetic studies. Due to the fact that the HO-Cu⁺-OH species are detected in La-Cu₄FeAICO₃/H₂O₂ system by XPS, the new mechanism about the generation of hydroxyl free radicals in the phenol hydroxylation is proposed, which is supposed that HO-Cu⁺-OH species are transition state in this reaction.     

A novel metal chalcogenide: HgCd<Subscript>4</Subscript>S<Subscript>5</Subscript>

A novel metal chalcogenide HgCd₄S₅ (1) was synthesized from solid-state reactions and structurally characterized. Compound 1 crystallizes in the space group C222₁ of the orthorhombic system with four formula units in a cell: a = 12.5661(5) Å, b = 7.2551(5) Å, c = 10.7520(7) Å, V = 980.2(1) ų, Cd₄HgS₅, M _r = 810.49, D _c = 5.492 g/cm³, S = 1.010, μ(MoK _α) = 25.128 mm^?1, F(000) = 1408, R = 0.0611 and wR = 0.1495. Compound 1 is characterized by a 3-D cadmium sulfide framework structure with the infinite mercury sulfide chains located in the cavities.     

Synthesis of hydroxyapatite by hydrolysis of α-Ca<Subscript>3</Subscript>(PO<Subscript>4</Subscript>)<Subscript>2</Subscript>

Conditions for hydroxyapatite (HAP) synthesis in aqueous solutions by hydrolysis of α-Ca₃(PO₄)₂ were studied. Temperature exerts a substantial effect on the rate of α-Ca₃(PO₄)₂ hydrolysis and also changes the morphology of the reaction products. At 40 °C, the plate-like intersecting (perpendicular to the surface of the initial particles) crystals of HAP grow. Their maximum size after the 24-h hydrolysis is 1–2 µm. Needle like HAP crystals are formed upon boiling of the suspension. The morphology observed for the HAP particles agrees well with the conclusions obtained by analysis of the kinetics of tricalcium phosphate hydrolysis.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 78–85, January, 2005.     

Phase diagrams of the systems Sc<Subscript>2</Subscript>S<Subscript>3</Subscript>-Ln<Subscript>2</Subscript>S<Subscript>3</Subscript> for Ln = La,Nd, or Gd

Phase diagrams have been designed for the systems Sc₂S₃-Ln₂S₃ where Ln = La, Nd, or Gd. In these systems, complex sulfides crystallize in orthorhombic space group Pnma. The sulfides melt congruently and have the following parameters; for LaScS₃, a = 0.718 nm, b = 0.654 nm, c = 0.960 nm, 2000 K, 3200 MPa; for NdScS₃, a = 0.712 nm, b = 0.646 nm, c = 0.952 nm, 1960 K, 3500 MPa; and for GdScS₃, a = 0.704 nm, b = 0.640 nm, c = 0.946 nm, 1900 K, 3400 MPa. The extents of the solid solutions based on the existing phases increase as the effective ion radii of Ln³⁺ approaches that of Sc³⁺. At 1670 K, the LnScS₃ homogeneity region is 48–52 mol % Nd₂S₃ and 46–54 mol % Gd₂S₃. Sc₂S₃ dissolves 3 mol % Nd₂S₃ and 6 mol % Gd₂S₃. γ-Nd₂S₃ dissolves 2 mol % Sc₂S₃, and γ-Gd₂S₃ dissolves 4 mol % Sc₂S₃. The subsystems Sc₂S₃-LnScS₃ and LnScS₃-Ln₂S₃ are of the eutectic type. The eutectic coordinates are, respectively, 27 mol % La₂S₃, 1880 K; 75 mol % La₂S₃, 1800 K; 30 mol % Nd₂S₃, 1850 K; 74 mol % Nd₂S₃, 1770 K; 33 mol % Gd₂S₃, 1800 K; and 74 mol % Gd₂S₃, 1730 K.     

Growth and properties of MnIn<Subscript>2</Subscript>S<Subscript>4</Subscript> single crystals

Homogeneous MnIn₂S₄ single crystals ∼14 mm in diameter and ∼40 mm long were grown by directional solidification of melt. For these MnIn₂S₄ single crystals, the composition was determined by electron probe microanalysis, structure by X-ray diffraction, and melting temperature by differential thermal analysis. Transmission spectra were studied in these single crystals, in the region of the intrinsic absorption edge within 10–300 K. The transmission spectra were used to determine the bandgap width, and it was plotted as a function of temperature. The thermal expansion of MnIn₂S₄ single crystals was studied dilatometrically in the range 80–700 K, and the thermal expansion coefficient was determined.     

Synthesis and Physicochemical Properties of a Lanthanum-Containing Analog of the Mineral Berthierite FeSb<Subscript>2</Subscript>S<Subscript>4</Subscript>

Phase equilibria in the FeSb₂S₄–FeLa₂S₄ system were studied by physicochemical analysis methods (differential thermal, X-ray powder diffraction, and microstructural analyses and microhardness and density measurements), and the phase diagram of the system was constructed. The formation of quaternary sulfide FeLaSbS₄ melting congruently at 1230 K, an analog of the mineral berthierite FeSb₂S₄, was detected. The X-ray powder diffraction analysis showed that FeLaSbS₄ belongs to the berthierite structural type and crystallizes in the orthorhombic system with the unit cell parameters a = 11.424 Å, b = 14.160 Å, c = 3.782 Å, Z = 4, and space group Pbam.     

Electrochemical properties of solid electrolytes based on BaSm<Subscript>2</Subscript>S<Subscript>4</Subscript>

Solid solutions based on BaSm₂S_{4 ? x} mol % BaS (Sm₂S₃) are obtained. Oxide intermediates were homogenized using chemical and mechanical mixing methods. The solid solution region is determined. Complex conductivity is studied and conductivity activation energy is calculated for samples with different history. Electrolytic properties of phases based on barium thiosamarate are studied. Vacancy mechanism of defect formation is suggested.     

Phase equilibria in the BaS-Cu<Subscript>2</Subscript>S-Gd<Subscript>2</Subscript>S<Subscript>3</Subscript> system

Phase equilibria in the BaS-Cu₂S-Gd₂S₃ system have been studied along the 800 K isothermal section and the CuGdS₂-BaS, Cu₂S-BaGdCuS₃, BaGdCuS₃-Gd₂S₃, and BaGdCuS₃-BaGd₂S₄ polythermal sections. Complex sulfide BaGdCuS₃ is formed in the title system; it has an orthorhombic KZrCuSe₃-type structure (space group Cmcm) with the unit cell parameters equal to a = 0.40529(2) nm, b = 1.34831(6) nm, c = 1.02940(5) nm. This sulfide melts congruently at 1685 K. BaGdCuS₃ is in equilibrium with sulfides Cu₂S, BaS, Gd₂S₃, CuGdS₂, BaGd₂S₄, BaCu₄S₃, and BaCu₂S₂ and with compositions in the C₀ solid-solution region of the Cu₂S-Gd₂S₃ system. Eutectics are formed between compounds CuGdS₂ and BaGdCuS₃ at 7.0 mol % BaS and T = 1325 K, between BaGdCuS₃ and BaS at 64.0 mol % BaS and T = 1625 K, between Cu₂S and BaGdCuS₃ at 8.0 mol % BaGdCuS₃ and T = 1125 K, between Gd₂S₃ and BaGdCuS₃ at 64.0 mol % Gd₂S₃ and 1495 K, and between BaGdCuS₃ and BaGd₂S₄ at 35 mol % BaGd₂S₄ and T = 1660 K.     

Chemical transformation of cluster osmium thioselenochloride Os<Subscript>3</Subscript>S<Subscript>7</Subscript>SeCl<Subscript>8</Subscript>

The binuclear osmium complex Os₃S₇SeCl₈ was prepared by the reaction of cluster chalcogen chloride K₆Os₂S₂O₆(CN)₈ with an aqueous KCN solution. In the complex, the distance between the osmium atoms is 2.85 Å, and they are linked by μ-SO ₂ ^2? bridges with the OsSOs angle of 75.9°. The osmium coordination number is 6. In the reaction with CN^? ligands under study, the individual fragments of the structure are retained; however, the trinuclear cluster skeleton of Os₃S₇SeCl₈ is destroyed.