Glass Formation in the Al<Subscript>2</Subscript>(SO<Subscript>4</Subscript>)<Subscript>3</Subscript>–(CH<Subscript>3</Subscript>)<Subscript>2</Subscript>SO–H<Subscript>2</Subscript>O System

The glass formation in the Al₂(SO₄)₃–(CH₃)₂SO–H₂O system was found for the first time. The competitive ability of ligands, dimethyl sulfoxide and water (which are strong donors), for entering the first coordination sphere of aluminum is considered. The possibility of mixed coordination of (CH₃)₂SO (via sulfur and oxygen atoms) in the first coordination sphere of aluminum with retention of the glass-forming ability of the sample was suggested on the basis of IR spectral study.     

High-temperature reactions in the Co<Subscript>3</Subscript>Cr<Subscript>4</Subscript>(PO<Subscript>4</Subscript>)<Subscript>6</Subscript>–Cr(PO<Subscript>3</Subscript>)<Subscript>3</Subscript> system

A new dichromium(III) cobalt(II) diphosphate(V) of the formula CoCr₂(P₂O₇)₂ was detected in the Co₃Cr₄(PO₄)₆–Cr(PO₃)₃ system. The new compound was obtained as a result of high-temperature solid-state reactions between CoCO₃, Cr₂O₃ and (NH₄)₂HPO₄ as well as between Cr(PO₃)₃ and Co₃Cr₄(PO₄)₆. CoCr₂(P₂O₇)₂ was characterized using XRD, DTA and IR methods. Results demonstrated that CoCr₂(P₂O₇)₂ crystallizes in the triclinic system and its unit cell parameters were calculated. Its infrared spectrum was presented. CoCr₂(P₂O₇)₂ melts incongruently at 1270±10 °C with a formation of solid α-CrPO₄. The compound Co₃Cr₄(PO₄)₆, component of the system under study, was obtained for the first time as a pure phase. Its thermal stability was also investigated. Co₃Cr₄(PO₄)₆ is stable in air up to 1410 ± 20 °C.     

Thermal studies of ZnO–B<Subscript>2</Subscript>O<Subscript>3</Subscript>–P<Subscript>2</Subscript>O<Subscript>5</Subscript>–TeO<Subscript>2</Subscript> glasses

The effect of TeO₂ additions on the thermal behaviour of zinc borophosphate glasses were studied in the compositional series (100 − x)[0.5ZnO–0.1B₂O₃–0.4P₂O₅]–xTeO₂ by differential scanning calorimetry, thermodilatometry and heating microscopy thermal analysis. The addition of TeO₂ to the starting borophosphate glass resulted in a linear increase of glass transition temperature and dilatometric softening temperature, whereas the thermal expansion coefficient decreased. Most of glasses crystallize under heating within the temperature range of 440–640 °C. The crystallization temperature steeply decreases with increasing TeO₂ content. The lowest tendency towards crystallization was observed for the glasses containing 50 and 60 mol% TeO₂. X-ray diffraction analysis showed that major compounds formed by annealing of the glasses were Zn₂P₂O₇, BPO₄ and α-TeO₂. Annealing of the powdered 50ZnO–10B₂O₃–40P₂O₅ glass leads at first to the formation of an unknown crystalline phase, which is gradually transformed to Zn₂P₂O₇ and BPO₄ during subsequent heating.     

Phase Transitions and Ionic Mobility in Solid Solutions in the System (NH<Subscript>4</Subscript>)<Subscript>2</Subscript>ZrF<Subscript>6</Subscript>–InF<Subscript>3</Subscript>

¹H and ¹⁹F NMR, XRD, and DTA methods are used to study thermal properties, ion mobility, and phase transitions (PT) in solid solutions obtained by doping anion-cationic conductor (NH₄)₂ZrF₆ with indium trifluoride. The types of ionic mobility are determined in the fluorine and ammonium sublattices of synthesized solid solutions at 150–450 K, their activation energies are estimated. A phase transition associated with formation of high-temperature modifications is registered at 400–413 K; ionic mobility in these modifications is mostly due to the diffusion of fluorine and ammonium ions.     

Physicochemical properties of (CH<Subscript>3</Subscript>)<Subscript>2</Subscript>NH<Subscript>2</Subscript>Cl–Al<Subscript>2</Subscript>O<Subscript>3</Subscript> composites

Composite solid electrolytes were synthesized from the organic salt dimethylammonium chloride (1–x)C₂H₈NCl–xAl₂O₃. Their physicochemical properties were studied. In the starting C₂H₈NCl salt, there is a phase transition at 39°C accompanied by an increase in conductivity by two orders of magnitude. The conductivity of the high-temperature phase is 9.3 × 10^–6 S/cm at 160°C. A differential scanning calorimetry study showed that the salt in the composites spreads over the oxide surface and at x > 0.6 the salt melting enthalpy decreases to zero. The conductivity of the resulting composites was studied by impedance spectroscopy. It was shown that heterogeneous doping leads to a sharp increase in ion conductivity to 7.0 × 10^–3 S/cm at 160°C and a decrease in the activation energy to 0.55 eV.     

Phase formation in the system Zn(VO<Subscript>3</Subscript>)<Subscript>2</Subscript>–HCl–VOCl<Subscript>2</Subscript>–H<Subscript>2</Subscript>O

The phase and chemical compositions of precipitates formed in the system Zn(VO₃)₂–HCl–VOCl₂–H₂O at pH 1?3, molar ratio V⁴⁺: V⁵⁺ = 0.1?9, and 80°C were studied. It was shown that, within the range 0.4 ≤ V⁴⁺: V⁵⁺ ≤ 9, zinc vanadate with vanadium in a mixed oxidation state forms with the general formula Zn_xV⁴⁺ _yV⁵⁺ _2-yO₅ ? nH₂O (0.005 ≤ x ≤ 0.1, 0.05 ≤ y ≤ 0.3, n = 0.5?1.2). Vanadate Zn_xV₂O₅ ? nH₂O with the maximum tetravalent vanadium content (y = 0.30) was produced within the ratio range V⁴⁺: V⁵⁺ = 1.5?9.0. Investigation of the kinetics of the formation of Zn_xV₂O₅ ? nH₂O at pH 3 determined that tetravalent vanadium ions VO2+ activate the formation of zinc vanadate, and its precipitation is described by a second-order reaction. It was demonstrated that, under hydrothermal conditions at pH 3 and 180°C, zinc decavanadate in the presence of VOCl₂ can be used as a precursor for producing V₃O₇ ? H₂O nanorods 50–100 nm in diameter.     

Crystal structure of [Pb<Subscript>3</Subscript>(OH)<Subscript>4</Subscript>Co(NO<Subscript>2</Subscript>)<Subscript>3</Subscript>](NO<Subscript>3</Subscript>)(NO<Subscript>2</Subscript>)·2H<Subscript>2</Subscript>O

The structure of [Pb₃(OH)₄Co(NO₂)₃](NO₃)(NO₂)·2H₂O is determined by single crystal X-ray diffraction. The crystallographic characteristics are as follows: a = 8.9414(4) Å, b = 14.5330(5) Å, c = 24.9383(9) Å, V = 3240.6(2) ų, space group Pbca, Z = 8. The Co(III) atoms have a slightly distorted octahedral coordination formed by three nitrogen atoms belonging to nitro groups (Co–N_av is 1.91 Å) and three oxygen atoms belonging to hydroxyl groups (Co–O_av is 1.93 Å). The hydroxyl groups act as μ₃-bridges between the metal atoms. The geometric characteristics are analyzed and the packing motif is determined.     

Separation of rare earth elements in the tributyl phosphate–Ln(NO<Subscript>3</Subscript>)<Subscript>3</Subscript>–Ca(NO<Subscript>3</Subscript>)<Subscript>2</Subscript> system in the counter current process

The 40-step extraction process to separate rare earth elements (RЕEs) according to the praseodymium–cerium line with the use of mixer–settler extractors in a 100% TBP–Ln(NO₃)₃–Ca(NO₃)₂ system is implemented. A lanthanum–cerium concentrate containing less than 0.03 wt % of the remaining REEs is obtained. The flow diagram of the separation process of a rare earth (RE) concentrate isolated from phosphogypsum is considered.     

Crystal structure of Na<Subscript>3</Subscript>(NH<Subscript>4</Subscript>)<Subscript>2</Subscript>[Ir(SO<Subscript>3</Subscript>)<Subscript>2</Subscript>Cl<Subscript>4</Subscript>]·4H<Subscript>2</Subscript>O

The complex Na₃(NH₄)₂[Ir(SO₃)₂Cl₄]·4H₂O was examined with single crystal X-ray diffraction and IR spectroscopy. Crystal data: a = 7.3144(4) Å, b = 10.0698(5) Å, c = 12.3748(6) Å, β = 106.203(1)°, V = 875.26(8) ų, space group P2₁/c, Z = 2, d _calc = 2.547 g/cm³. In the complex anion two trans SO ₃ ^2? groups are coordinated to iridium through the S atom. The splitting of O-H bending vibrations of crystallization water molecules and N-H ones of the ammonium cation is considered in the context of different types of interactions with the closest neighbors in the structure.     

Glass Formation in the Ternary System La<Subscript>2</Subscript>O<Subscript>3</Subscript>–As<Subscript>2</Subscript>S<Subscript>3</Subscript>–Er<Subscript>2</Subscript>O<Subscript>3</Subscript>

The boundaries of the glass formation region in the ternary system La₂O₃–As₂S₃–Er₂O₃ were found. Transparent glass of composition (La₂O₃)_0.03(As₂S₃)0.90(Er₂O₃)0.07 was studied by X-ray photoelectron and Raman spectroscopy. The intensities of the bands characterizing As–S, La–O, and Er–O bonds increased, and these bands were shifted toward higher energies. This was due to an increase in the covalence of these bonds and probably due to the formation of new bonds in the glasses. Samples in the glass formation region are resistant at 300 K to air, water, and organic solvents.     

Synthesis and study of uranyl arsenate (UO<Subscript>2</Subscript>)<Subscript>3</Subscript>(AsO<Subscript>4</Subscript>)<Subscript>2</Subscript> · 12H<Subscript>2</Subscript>O

A method for producing synthetic troegerite of composition(UO₂)₃(AsO₄)₂ · 12H₂. Owas developed. X-ray diffraction, IR spectrometry, X-ray fluorescence analysis, and scanning calorimetry were used to study its dehydration and thermal decomposition, to solve the structgure, and to determine X-ray diffraction and IR spectroscopic characteristics.     

Calorimetric studies on 2TeO<Subscript>2</Subscript>–V<Subscript>2</Subscript>O<Subscript>5</Subscript> glasses

Glasses of the composition 2TeO₂–V₂O₅ were fabricated via the conventional melt-quenching technique. The amorphous and the glassy nature of the as-quenched samples were confirmed by X-ray powder diffraction (XRD) and differential scanning calorimetry (DSC), respectively. The glass transition and crystallization parameters were evaluated under non-isothermal conditions using DSC. X-ray diffraction studies confirmed the presence of partially oriented crystallites in the heat-treated glasses. Kauzmann temperature (lower bound for the kinetically observed glass transition) was deduced from the heating rate dependent glass transition and crystallization temperatures.     

Simulating equilibrium processes in the Ga(NO<Subscript>3</Subscript>)<Subscript>3</Subscript>–H<Subscript>2</Subscript>O–NaOH system

Equilibrium processes in the Ga(NO₃)₃–H₂O–NaOH system are simulated with allowance for the formation of precipitates of various compositions using experimental data from potentiometric titration and theoretical studies. The values of the instability constants are calculated along with the stoichiometric compositions of the resulting compounds. It is found that pH ranges of 1.0 to 4.3 and 12.0 to 14.0 are best for the deposition of gallium chalcogenide films.     

A Raman Spectroscopic Study of Aqueous La(CH<Subscript>3</Subscript>CO<Subscript>2</Subscript>)<Subscript>3</Subscript> Solutions and La(CH<Subscript>3</Subscript>CO<Subscript>2</Subscript>)<Subscript>3</Subscript>·1.5 H<Subscript>2</Subscript>O(cr)

Aqueous solutions of La(CH₃CO₂)₃, NaCH₃CO₂ and La(ClO₄)₃ were studied using Raman spectroscopy. In dilute NaCH₃CO₂ solution, acetate is fully hydrated and forms only minor amounts of ion pairs. The characteristic Raman bands are discussed and assigned. In fairly dilute La(ClO₄)₃ solutions, the La³⁺(aq) ion occurs as the nonahydrate. The separation of the carboxylate bands, ν_as – ν_s (Δ-value), in NaCH₃CO₂(cr) compared to La(CH₃CO₂)₃·1.5H₂O(cr) correlates with the bonding type of acetate which is “ionic” in the former but bidentate chelating/tridentate chelating in the latter. Other acetate bands such as the deformation mode of the CO₂ moiety, δ CO₂, and the two rocking vibrations (ρ), as well as the C–C stretch show marked differences in their band positions in NaCH₃CO₂(cr) compared to the ones in La(CH₃CO₂)₃·1.5H₂O(aq). In a ternary solution of La(CH₃CO₂)₃/LaCl₃ with a molar ratio La³⁺(aq): \( {\text{CH}}_{3} {\text{CO}}_{2}^{ - } \)(aq) = 3.87: 1.00), the bands of the bound acetate on La³⁺ were characterized and compared to those of fully hydrated acetate, \( {\text{CH}}_{3} {\text{CO}}_{2}^{ - } \left( {\text{aq}} \right) \). In this solution, almost all acetate is ligated to La³⁺ in a bidentate fashion and two complex species could be identified (molar ratios La³⁺: \( {\text{CH}}_{3} {\text{CO}}_{2}^{ - } \)  = 1:1 and 1:2, respectively). In La(CH₃CO₂)₃ solutions in H₂O and D₂O strong acetato complexes are formed and the bands of the bound acetate were characterized and compared with the ones of the fully hydrated acetate modes. A dilution series down to 0.0037 mol·L^?1 in La(CH₃CO₂)₃(aq) and to 0.0150 mol·L^?1 in La(CH₃CO₂)₃(D₂O) showed that two acetate complexes are formed in these solutions. Again, it was shown that in these solutions the bound acetates on La³⁺ exist as bidentate ligands. DFT frequencies of the acetate on clusters {La(OH₂)₇O₂CCH₃)}²⁺ and {La(OH₂)₅(O₂CCH₃)₂}⁺ compared well with the measured values. By determining the ligation number, \( \bar{n} \), it can be established that in dilute solutions, below 0.04 mol·L^?1, a complex with a 1:1 stoichiometry (La³⁺: \( {\text{CH}}_{3} {\text{CO}}_{2}^{ - } \)) exists in equilibrium with “free” acetate while in more concentrated solutions a 1:2 complex also forms. La³⁺(aq) hydrolysis is slight and very small equilibrium concentrations of CH₃COOH were detected (C–C stretch at 893 cm^?1). From quantitative Raman measurements, K ₁ was determined to be 160 ± 10 at 22 °C.     

Porous xerogels with a bifunctional surface layer of the composition ≡Si(CH<Subscript>2</Subscript>)<Subscript>3</Subscript>SH/≡Si(CH<Subscript>2</Subscript>)<Subscript>2</Subscript>H<Subscript>3</Subscript>

The sol-gel method with ethanol as a solvent and fluoride ion as a catalyst was used to prepare polysiloxane xerogels containing both 3-mercaptopropyl and n-propyl groups in the surface layer. An increase in the relative amount of n-propyltriethoxysilane in the initial reaction solution was found to result in the formation of xerogels with developed porous structures, which was accompanied by an increase in the specific surface area from 370 to 550 m²/g; simultaneously, other porous structure parameters such as sorption volume and pore size exhibited a tendency to increase. Atomic-force microscopy was used to show that the xerogels synthesized comprised aggregates of mean size 30 nm. An analysis of the IR and ¹³C cross-polarization magic angle spinning NMR data led us to conclude that the surface layer of bifunctional xerogels contained not only 3-mercaptopropyl and n-propyl groups but also silanol groups, part of nonhydrolyzed alkoxy groups, and H-bonded water molecules. The ²⁹Si cross-polarization magic angle spinning NMR spectra revealed the presence of structural units of the compositions T¹ [(≡SiO)Si(OR’)₂(CH₂CH₂CH₃) and/or (≡SiO)Si(OR’)₂(CH₂)₃SH, R’ = H, OCH₃, or OC₂H₅], T² [(≡SiO)₂Si(OR’)(CH₂CH₂CH₃) and (≡SiO)₂Si(OR’)(CH₂)₃SH], and T³ [(≡SiO)₃SiCH₂CH₂CH₃ and (≡SiO)₃Si(CH₂)₃SH] in the xerogels synthesized.     

Physicochemical Analysis of the System Zr(SO<Subscript>4</Subscript>)<Subscript>2</Subscript>–Na<Subscript>2</Subscript>SO<Subscript>4</Subscript>–H<Subscript>2</Subscript>SO<Subscript>4</Subscript>–H<Subscript>2</Subscript>O at 25°С

The solubility in the quaternary water–salt system Zr(SO₄)₂ · 4Н₂О–Na₂SO₄–H₂SO₄–H₂O at 25°C was studied. It was found that, in the system, there is crystallization of not only Na₂SO₄ and Zr(SO₄)₄ · 4H₂O, but also sodium sulfate zirconates Na₂Zr(SO₄)₂(OH)₂ · 0.3H₂O, Na₄Zr(SO₄)₄ · 3H₂O, and Na₂Zr(SO₄)₂ · 3H₂O and two new compounds, S₁ and S₂, which are presumably Na₂ZrO(SO₄)₂ · 2H₂O and Na₂Zr₂O₂(SO₄)₃ · 6H₂O.     

Thermal analysis of the (Bi<Subscript>2</Subscript>O<Subscript>3</Subscript>)<Subscript>1−x</Subscript>(Y<Subscript>2</Subscript>O<Subscript>3</Subscript>)<Subscript>x</Subscript> pigments

The synthesis of new compounds based on Bi₂O₃ is investigated because they can be used as new ecological inorganic pigments. Chemical compounds of the (Bi₂O₃)_1−x(Y₂O₃)_x type were synthesized. The host lattice of these pigments is Bi₂O₃ that is doped by Y³⁺ ions. The incorporation of doped ions provides the interesting colours and contributes to a growth of the thermal stability of these compounds. The simultaneous TG-DTA measurements were used for determination of the temperature region of the pigment formation and thermal stability of pigments. This paper also contains the results of the pigment characterization by X-ray powder diffraction and their colour properties.     

Synthesis and structure of the complex [Mo<Subscript>3</Subscript>(μ<Subscript>3</Subscript>-S)(μ<Subscript>2</Subscript>-S<Subscript>2</Subscript>)<Subscript>3</Subscript>(Et<Subscript>2</Subscript>NCS<Subscript>2</Subscript>)<Subscript>3</Subscript>]I

The structure of tri-μ₂-disulfido-μ₃-thiotris(diethyldithiocarbamato)-S,S′-triangle-trimolybdenum iodide [Mo₃(μ₃-S)(μ₂-S₂)₃(Et₂NCS₂)₃]I was determined. The compound was characterized by differential thermal analysis and IR, Raman, and X-ray electronic spectroscopy.     

Thermal decomposition of praseodymium nitrate hexahydrate Pr(NO<Subscript>3</Subscript>)<Subscript>3</Subscript>·6H<Subscript>2</Subscript>O

The hexahydrate of praseodymium nitrate hexahydrate Pr(NO₃)₃·6H₂O does not show phase transitions in the range of 233–328 K when the compound melts in its own water of crystallization. It is suggested that the thermal decomposition is a complex step-wise process, which involves the condensation of 6 mol of the initial monomer Pr(NO₃)₃·6H₂O into a cyclic cluster 6[Pr(NO₃)₃·6H₂O]. This hexamer gradually loses water and nitric acid, and a series of intermediate amorphous oxynitrates is formed. The removal of 68% HNO₃–32% H₂O azeotrope is essentially a continuous process occurring in the liquid phase. At higher temperatures, oxynitrates undergo thermal degradation and lose water, nitrogen dioxide and oxygen, leaving behind normal praseodymium oxide Pr₂O₃. The latter absorbs approximately 1 mol of atomic oxygen from N₂O₅ disproportionation, giving rise to the non-stoichiometric higher oxide Pr₂O_3.33. All mass losses are satisfactorily accounted for under the proposed scheme of thermal decomposition.     

Physicochemical Interaction in the TlInSe<Subscript>2</Subscript>–TlInP<Subscript>2</Subscript>Se<Subscript>6</Subscript> System

Phase equilibria in the TlInSe₂–TlInP₂Se₆ system have been studied for the first time by classic physicochemical analysis methods (differential thermal analysis (DTA), X-ray diffraction, and microstructural analysis (MSA)), and its phase diagram has been plotted. The system belongs to the eutectic type (Rooseboom V type) and forms boundary solid solutions based on the initial complex selenides.