Solubility of YF<Subscript>3</Subscript>, CeF<Subscript>3</Subscript>, PrF<Subscript>3</Subscript>, NdF<Subscript>3</Subscript>, and DyF<Subscript>3</Subscript> in solutions containing sulfuric and phosphoric acids

The solubility of YF₃, CeF₃, PrF₃, NdF₃, and DyF₃ in solutions containing 0–4.496% mol/L (0–35 wt %) of H₂SO₄ and 0–27.6 g/L of H₃PO₄ (0–20 g/L of P₂O₅) at 20 °C was determined. Higher solubility in sulfuric acid solutions compared to that in hydrochloric and phosphoric acid solutions was attributed to the formation of fluorosulfate complexes M₂(SO₄)F₄(M = Y, Ce, Pr, Nd, Dy). The effect of minor concentrations of the phosphate ions on the solubility of YF₃, CeF₃, PrF₃, NdF₃, and DyF₃ in sulfuric acid solutions and the effect of fluoride ions on the recovery of lanthanides during sulfuric acid leaching from the phosphohemihydrate were discussed.     

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.     

Quantum-chemical study of ytterbium fluorides and of complex F<Subscript>2</Subscript>YbF<Subscript>2</Subscript>CeF<Subscript>2</Subscript>

The structural parameters of the (²Σ⁺//C_∞v)-YbF, (¹A₁//C_2v)-YbF2, (²A₂^′//D_3h)-YbF₃, (¹Ag//D_2h)-YbF₂Yb, (¹Ag//C_2h)-FYbF₂YbF, (¹A₁//C_2v)-FYbF₂YbF, (¹A₁//C_2v)-YbF₂YbF₂, (³B_3u//D_2h)-F₂YbF₂YbF₂, (²A′//C_s)-FYbF₂YbF₂, and (³B₂//С_2v)-F₂YbF₂CeF₂ molecules have been determined. Disproportionation of ytterbium monofluoride (2YbF → YbF₂ + Yb + 0.46 eV) is less exothermic than dimerization (2YbF → YbF₂Yb + 2.10 eV). The bond energy of the ytterbium difluoride molecules in the trans dimer (2.93 eV) exceeds those in the cis dimer (2.86 eV) and the coaxial dimer (1.66 eV). Ytterbium trifluoride dimerizes exothermically (2.95 eV) without spin pairing. The dipole and quadrupole moments of the molecules as well as the charges and spin populations of the atoms and the valence electron configurations of the lanthanides have been calculated.     

Phase equilibria in the system LaMnO<Subscript>3</Subscript>-SrMnO<Subscript>3</Subscript>-SrCrO<Subscript>4</Subscript>-LaCrO<Subscript>3</Subscript>

A continuous solid solution LaMn_1?y Cr _y O₃ with an orthorhombic structure is found to exist in the range of 0.0 ≤ y ≤ 1.0. An orthorhombic solid solution La_1?x Sr _x CrO₃ exists in the range of 0.0 ≤ x ≤ 0.1. The stability boundaries are determined for the perovskite phase La_1?x Sr _x Mn_1?y Cr _y O₃. An isobaric-isothermal section LaMnO₃-SrMnO₃-SrCrO₄-LaCrO₃ of the system La₂O₃-SrO-Mn₃O₄-Cr₂O₃ in air at 1100°C is designed.     

Glass formation in the Al(IO<Subscript>3</Subscript>)<Subscript>3</Subscript>-Al<Subscript>2</Subscript>(SO<Subscript>4</Subscript>)<Subscript>3</Subscript>-HIO<Subscript>3</Subscript>-H<Subscript>2</Subscript>O system

On the basis of experimental data obtained in the study of glass-formation boundaries in the Al₂(SO₄)₃-HIO₃-H₂O, Al(IO₃)₃-Al₂(SO₄)₃-H₂O, and Al(IO₃)₃-HIO₃-H₂O systems and using geometrical analysis, we predict the positions of glass-formation boundaries in the Al(IO₃)₃-Al₂(SO₄)₃-HIO₃-H₂O four-component system along 60, 40, and 25 wt % H₂O sections.     

Glass formation in the Al<Subscript>2</Subscript>(SO<Subscript>4</Subscript>)<Subscript>3</Subscript>-Al(NO<Subscript>3</Subscript>)<Subscript>3</Subscript>-H<Subscript>2</Subscript>O system

Glass formation boundaries in the Al₂(SO₄)₃-Al(NO₃)₃-H₂O system were determined. IR spectra were studied. Schemes of structural rearrangements within the boundaries of a second glass formation region in the Al(NO₃)₃-H₂O binary subsystem are suggested. A structure is suggested for glassy Al(NO₃)₃H₂O.     

Projection of the liquidus surface of the Sb<Subscript>2</Subscript>Te<Subscript>3</Subscript>-Gd<Subscript>2</Subscript>Te<Subscript>3</Subscript>-Bi<Subscript>2</Subscript>Te<Subscript>3</Subscript> system

Phase equilibria in the Sb₂Te₃-Gd₂Te₃-Bi₂Te₃ ternary system have been studied using differential thermal analysis, namely, X-ray powder diffraction, microstructure examination, thermodynamic analysis, and microhardness and alloy density measurements. Phase diagrams of some polythermal joins and liquidus surface have been constructed. The regions of primary crystallization of phases and the coordinates of all invariant and univariant equilibria in the system under investigation have been established.     

The La(CCl<Subscript>3</Subscript>COO)<Subscript>3</Subscript>-NaCCl<Subscript>3</Subscript>COO-H<Subscript>2</Subscript>O system at 298 K

The ternary lanthanum trichloroacetate-sodium trichloroacetate-water system was studied by the isothermal solubility method at 298 K. The compositions of solid phases were established by the Schkreinemakers’ wet residue method. The liquid refractive indexes, specific volumes, and viscosities were determined. The system was found to be eutonic.     

Glass formation in the system Al(IO<Subscript>3</Subscript>)<Subscript>3</Subscript>-HIO<Subscript>3</Subscript>-H<Subscript>2</Subscript>O

Glass-formation features in the system Al(IO₃)₃-HIO₃-H₂O are discussed, and the boundaries of the glass field are determined.     

Phase relations in the MgO-Bi<Subscript>2</Subscript>O<Subscript>3</Subscript>-Bi<Subscript>2</Subscript>O<Subscript>3</Subscript> system

Phase relations in the MgO-Bi₂O₃-B₂O₃ system have been investigated by X-ray powder diffraction analysis and DTA. No ternary compounds have been found in the system. Quasi-binary sections have been the 600°C determined and isothermal section of the system has been constructed.     

Solid solutions in the MgO-Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-Cr<Subscript>2</Subscript>O<Subscript>3</Subscript> system

Coexisting solid solutions with spinel and corundum structure were synthesized at 1773 K and two pressures, 1 bar and 25 kbar. Samples were analyzed by electron microprobe analysis and X-ray powder diffraction. Pressure and temperature were shown to affect the properties of the solid solutions in different ways. Pressure governs the composition of the defect spinel Mg_1−xAl₂O₄, and temperature changes the cation distribution between coexisting phases. This allows one to separate the effects of cation exchange and magnetic contribution to the heat capacity in thermodynamic modeling. The defect spinel itself can form only because γ-Al₂O₃ exists, polymorph with spinel structure.     

Phase formation in the LiCl-LiNO<Subscript>3</Subscript>-KCl-Sr(NO<Subscript>3</Subscript>)<Subscript>2</Subscript> system

The LiCl-LiNO₃-KCl-Sr(NO₃)₂ four-component system was studied for the first time by a complex of physicochemical analysis methods, including differential thermal analysis, X-ray diffraction, visual-polythermal, and projection thermographic methods. Eutectic and peritectic invariant point characteristics were determined, and the phase diagram of the system was constructed.     

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 %.     

Behavior of silver sulfide in the system Ag<Subscript>2</Subscript>S-Fe(NO<Subscript>3</Subscript>)<Subscript>3</Subscript>-HNO<Subscript>3</Subscript>-H<Subscript>2</Subscript>O

Behavior of silver sulfide in the system Ag₂S-Fe(NO₃)₃-HNO₃-H₂O was studied at 25, 55, and 80°C using the method of the simplex-lattice experiment design. The quantitative dependences of Ag₂S oxidation on the concentrations of the acid and Fe³⁺ were determined. The isoconcentration diagrams were obtained.     

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.     

Phase formation in the InPO<Subscript>4</Subscript>-Na<Subscript>3</Subscript>PO<Subscript>4</Subscript>-Li<Subscript>3</Subscript>PO<Subscript>4</Subscript> ternary system

The 950°C isothermal section of the InPO₄-Na₃PO₄-Li₃PO₄ ternary system was studied and constructed; one-, two, and three-phase fields are outlined. Five solid-solution regions exist in the system: solid solutions based on the complex phosphate LiNa₅(PO₄)₂ (olympite structure), the indium ion stabilized high-temperature Na₃PO₄ phase (Na_{3(1 − x)}In _x (PO₄); space group Fm [`3]\bar 3 m), the complex phosphate Na₃In₂(PO₄)₃, and the α and β phases of the compound Li₃In₂(PO₄)₃. A narrow region of melt was found in the vicinity of eutectic equilibria. All the phases detected in the system are derivatives of phases existing in the binary subsystems. Isovalent substitution of lithium for sodium in Na₃In₂(PO₄)₃ leads to a significant increase in the region of a NASICON-like solid solution.     

Solid solutions in the system Nd(CCl<Subscript>3</Subscript> COO)<Subscript>3</Subscript>-Y(CCl<Subscript>3</Subscript> COO)<Subscript>3</Subscript>-H<Subscript>2</Subscript> O at 298 K

The water-salt system consisting of neodymium and yttrium trichloroacetates is studied by the isothermal solubility method at 298 K. The compositions of solid phases are determined by the Schreinemakers wet residues technique. Refractive indices, specific volumes, and viscosities for liquid phases and refractive indices of crystals for solid phases are determined. Continuous solid solutions are found in the system; some their thermodynamic characteristics are calculated.     

Whitlockite solid solutions in the Ca<Subscript>3</Subscript>(VO<Subscript>4</Subscript>)<Subscript>2</Subscript>-K<Subscript>3</Subscript>VO<Subscript>4</Subscript>-NdVO<Subscript>4</Subscript> system

Phase equilibria in the Ca₃(VO₄)₂-K₃VO₄-NdVO₄ system have been studied. An extensive calcium orthovanadate-based solid solution was found to form with the boundary compositions as follows: Ca₃(VO₄)₂-Ca₉Nd(VO₄)₇-Ca_9.33K_2.33(VO₄)₇-Ca_7.88K_2.63Nd_0.87(VO₄)₇. The unit cell parameters of the whit-lockite vanadates synthesized increase as the potassium and neodymium contents increase. Phase transitions from the low-temperature β phase to the β′ centrosymmetrical structure in Ca_{9.33 − 5z} K_{2.33 + z} Nd_3z (VO₄)₇ vanadates have been studied dilatometrically. The increase in the β ai β′ transition temperature caused by potassium is interpreted as arising from the filling in of vacant cation positions M(4) and M(6).     

Phase relations in the CaO-Bi<Subscript>2</Subscript>O<Subscript>3</Subscript>-B<Subscript>2</Subscript>O<Subscript>3</Subscript> system in the subsolidus region

Phase relations in the CaO-Bi₂O₃-B₂O₃ system have been investigated by X-ray powder diffraction and differential thermal analyses, and the isothermal section at 600°C has been constructed. The formation of ternary compounds at the component ratios 1CaO: 1Bi₂O₃: 1B₂O₃ (CaBi₂B₂O₇) and 1CaO: 1Bi₂O₃: 2B₂O₃ (CaBi₂B₄O₁₀) has been established X-ray diffraction characteristics of these phases are presented.     

Synthesis of sodium tungstate from the system Na<Subscript>2</Subscript>C<Subscript>2</Subscript>O<Subscript>4</Subscript>-NaNO<Subscript>3</Subscript>-WO<Subscript>3</Subscript>

The physicochemical basis of the heterogeneous reaction between the components of the system (sodium oxalate)-(sodium nitrate)-(tungsten(VI) oxide) has been studied. The reaction of WO₃ with sodium oxalate-nitrate mixtures occurs at a lower temperature and at a higher rate than the reaction with pure sodium carbonate. A high-yield process for the synthesis of high-purity sodium tungstate has been developed on the basis of this study.