A study of phase formation in the subsolidus region of the system Na<Subscript>2</Subscript>MoO<Subscript>4</Subscript>-MnMoO<Subscript>4</Subscript>-Cr<Subscript>2</Subscript>(MoO<Subscript>4</Subscript>)<Subscript>3</Subscript>

Phase relationships in the subsolidus region of the system Na₂MoO₄-MnMoO₄-Cr₂(MoO₄)₃ were studied by means of X-ray diffraction and differential-thermal analyses. The possibility of obtaining a variablecomposition phase Na_1?x Mn_1?x Cr_1+x (MoO₄)₃ (0 ≤ x ≤ 0.5) and ternary molybdate NaMn₃Cr(MoO₄)₅ was examined. The temperature dependence of the conductivity of the phase Na_1?x Mn_1?x Cr_1+x (MoO₄)₃ was analyzed.     

New Phosphate-Sulfates with NZP Structure

NaZr_2–xB_x(PO₄)_3–2x(SO₄)_2x (0 ≤ x ≤ 1.25, B = Mg, Co, Ni, Cu, Zn), and NaZr_2–xR_x(PO₄)_3–x(SO₄)_x (0 ≤ x ≤ 1.25, R = Al, Fe) phosphate-sulfates series have been prepared by a sol–gel process. These compounds belong to the NaZr₂(PO₄)₃ (NZP) structure family and crystallize in hexagonal crystal system, space group R\(\bar 3\)c. Limited solid solution series were found to exist; their formation temperatures and thermal stability limits were determined. Particle sizes as determined by microstructure observation were 50–200 nm, and for Cu- and Zn-containing samples, 200–500 nm. The thermal expansion of phosphate-sulfate NaZr_1.25Cu_0.75(PO₄)_1.5(SO₄)_1.5 was studied in the range 25–700°C. Thermal expansion coefficients and thermal expansion anisotropy were found to be α_a =–5.40 × 10^–6 °C^–1, α_с = 18.88 × 10^–6 °C^–1, α_avg = 2.69 × 10^–6 °C^–1, and Δα = 24.28 × 10^–6 °C^–1.     

Synthesis,structure, and thermal expansion of sodium zirconium arsenate phosphates

Sodium zirconium arsenate phosphates NaZr₂(AsO₄) _x (PO₄)_3?x were synthesized by precipitation technique and studied by X-ray diffraction and IR spectroscopy. In the series of NaZr₂(AsO₄) _x (PO₄)_3?x , continuous substitution solid solutions are formed (0 ≤ x ≤ 3) with the mineral kosnarite structure. The crystal structure of NaZr₂(AsO₄)_1.5(PO₄)_1.5 was refined by full-profile analysis: space group R \(\bar 3\) c, a = 8.9600(4)Å, c = 22.9770(9) Å, V = 1597.5(1) ų, R _wp = 4.55. The thermal expansion of the arsenate-phosphate NaZr₂(AsO₄)_1.5(PO₄)_1.5 and the arsenate NaZr₂(AsO₄)₃ was studied by thermal X-ray diffraction in the temperature range of 20–800°C. The average linear thermal expansion coefficients (α_av = 2.45 × 10^?6 and 3.91 × 10^?6 K^?1, respectively) indicate that these salts are medium expansion compounds.     

Alkali (alkaline-earth) metal,aluminum, and titanium complex orthophosphates: Synthesis and characterization

Phase formation in the A_{1 + x} Al _x Ti_{2 ? x} P₃O₁₂ (A = Li, Na, K, Rb, or Cs; 0 ≤ x ≤ 2.0) and B_{0.5(l + x)}Al _x Ti_{2 ? x} P₃O₁₂ (B = Mg, Ca, Sr, or Ba; 0 ≤ x ≤ 2.0) systems was studied using X-ray powder diffraction, electron probe microanalysis, and IR spectroscopy. The following double and triple orthophosphates were found to exist: A_{1 + x} Al _x Ti_{2 ? x} (PO₄)₃ with A = Li (0 ≤ x ≤ 0.3), Na (0 ≤ x ≤ 1.0), K (x = 0, 1.0, or 2.0), Rb (x = 0, 1.0, or 2.0), or Cs (0 ≤ x ≤ 1.0) and B_{0.5(l + x)}Al _x Ti_{2 ? x} (PO₄)₃ with B = Mg and Ba (x = 0), Ca and Sr (0 ≤ x ≤ 0.2). These orthophosphates crystallize in the structure types of kosnarite, langbeinite, cesium titanium arsenate, potassium aluminum phosphate, or rubidium aluminum phosphate. Their crystal parameters were calculated. For CsTi₂(PO₄)₃ (x = 0), Rietveld refinement was carried out: space group Ia \(\bar 3\) d, Z = 32, a = 19.909(5) Å, V = 7892(1) ų. This compound has a framework structure. The framework is built of TiO₆ octahedra and PO₄ tetrahedra; eight- and 12-coordinated Cs⁺ cations populate interstices.     

Phase formation in the Ag<Subscript>2</Subscript>MoO<Subscript>4</Subscript>-MgMoO<Subscript>4</Subscript>-Al<Subscript>2</Subscript>(MoO<Subscript>4</Subscript>)<Subscript>3</Subscript> system

The subsolidus region of the Ag₂MoO₄-MgMoO₄-Al₂(MoO₄)₃ ternary salt system has been studied by X-ray phase analysis. The formation of new compounds Ag_{1 ? x} Mg_{1 ? x} Al_{1 + x} (MoO₄)₃ (0 ≤ x ≤ 0.4) and AgMg₃Al(MoO₄)₅ has been determined. The Ag_{1 ? x} Mg_{1 ? x} Al_{1 + x} (MoO₄)₃ variable-composition phase is related to the NASICON type structure (space group R \(\bar 3\) c). AgMg₃Al(MoO₄)₅ is isostructural to sodium magnesium indium molybdate of the same formula unit and crystallizes in triclinic system (space group P \(\bar 1\), Z = 2) with the following unit cell parameters: a = 9.295(7) Å, b = 17.619(2) Å, c = 6.8570(7) Å, α = 87.420(9)°, β = 101.109(9)°, γ = 91.847(9)°. The compounds Ag_{1 ? x} Mg_{1 ? x} Al_{1 + x} (MoO₄)₃ and AgMg₃Al(MoO₄)₅ are thermally stable up to 790 and 820°C, respectively.     

Systems Li<Subscript>2</Subscript>O(Na<Subscript>2</Subscript>O)-CdO-V<Subscript>2</Subscript>O<Subscript>5</Subscript>: Phase composition and phase diagrams

The subsolidus phase composition of the M₂O-CdO-V₂O₅ systems with M = Li or Na is studied. Double orthovanadates MCdVO₄ and MCd₄(VO₄)₃ form solid solutions of composition Li_{1 ? 2x/3}Cd _x/3CdVO₄ (0 ≤ x ≤ 1, orthorhombic space group Cmcm, modulation at x = 0.6) and Na_{3 ? 2x} Cd_{3 + x} (VO₄)₃ (0 ≤ x ≤ 0.10 and 0.30 ≤ x ≤ 1, orthorhombic space group Cmcm and Pn2₁ a or Pnma, respectively). In the range 0.10 < x < 0.30, the end-members of the solid solutions coexist. Isothermal sections of the systems are mapped.     

Isomorphic substitution of neodymium and gadolinium for calcium in synthetic hydroxovanadate

Isomorphic substitution of neodymium and gadolinium for calcium in synthetic hydroxovanadate Ca_{5 ? x} M _x (VO₄)₃(OH)_{1 ? x} O _x (M = Nd, Gd) is studied in the range 700–1000°C using X-ray powder diffraction, single-crystal X-ray diffraction (Rietveld technique), and IR spectroscopy. Single-phase solid solutions at 800°C are formed with x ≤ 0.35 for M(III) = Nd and x ≤ 0.3 for M(III) = Gd. With high x, the apatite solid solution coexists with Ca₃(VO₄)₂, Nd₂O₃, and X phases. With increasing x in the homogeneous region, the intensity of the bands of stretching vibrations and librations of OH groups decrease. Single-crystal X-ray diffraction shows that neodymium and gadolinium substitute for calcium in solid solutions mostly in Ca(2) positions.     

Synthesis and study of solid solutions between cobalt and nickel phosphates with varied degree of anion protonation

Continuous substitutional solid solutions between cobalt and nickel phosphates with varied degree of anion protonation were obtained: Co_1?x Ni _x HPO₄·1.5H₂O and (Co_1?x Ni _x )₃(PO₄)₂·8H₂O, where 0 ≤ x ≤ 1.00. The thermolysis of the solid solutions was studied by the example of Co_1?x Ni _x HPO₄·1.5H₂O. The phases synthesized were compared with the previously described continuous solid solution Co_1?x Ni _x (H₂PO₄)₂·2H₂O.     

Synthesis of (Ni<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>Co<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>)<Subscript>2</Subscript>P (0 ≤ <Emphasis Type="Italic">x</Emphasis> ≤ 0.65) substitution solid solution

The phosphides (Ni_{1 ? x} Co _x )₂P (0 ≤ x ≤ 0.65) crystallizing in the hexagonal system, space group P \(\bar 6\)2m, were synthesized in two steps starting from the continuous solid solution (Ni_{1 ? x} Co _x )₃(PO₄)₂ · 8H₂O. The initial phosphates were first completely dehydrated at 800°C and then reduced with hydrogen at 900–1000°C for 1–2 h.     

Glass-forming ability and thermal stability of Se<Subscript>100−x</Subscript>(Ge<Subscript>2</Subscript>Sb<Subscript>2</Subscript>Te<Subscript>5</Subscript>)<Subscript>x</Subscript> glassy alloys

Glassy Se_100?x(Ge₂Sb₂Te₅)_x (x?=?5, 10, 15 and 20) bulk alloys were prepared by melt-quenched technique and studied by using differential scanning calorimetry at different heating rates under non-isothermal condition. The detailed thermal analysis shows that the glass transition temperature (T_g) depends on heating rates and x content. In particular, it is found that the glass-forming ability, thermal stability (T_c???T_g) and crystallization activation energy (E_c) increase with increased x content in amorphous Se, whereas glass transition activation energy (E_g) and fragility index (F) decrease with increased x contents. Variation in these parameters can be explained on the basis of network-forming ability of Se and bonding arrangement among the constituent atoms of alloys.     

The effect of phosphate group replacement by sulfate groups on the phase formation in the synthesis of hydroxyapatite

Sulfate-substituted hydroxyapatite materials with a degree of substitution of up to 20 mol % (Ca₁₀(PO₄)_{(6 – 0.06x)}(SO₄)_0.09x (OH)₂, x = 0, 0.1, 0.5, 1, 5, 10, and 20) were synthesized. For substitutions of 0, 0.1, 0.5, and 1 mol %, a single-phase material with the apatite structure is formed. On further increase in the concentration of SO₄ ^2? groups up to 20 mol %, a second phase, CaSO₄, is formed; the amount of this phase increases for higher degrees of substitution. The unit cell parameters of hydroxyapatite-based materials change slightly upon the replacement of phosphate groups by sulfate groups: the parameter a tends to increase, while c tends to decrease. The introduction of sulfate groups results in decreasing particle size.     

Substitution of barium for strontium in hydroxovanadate structure

A possibility of substitution of barium for strontium in Sr₁₀(VO₄)₆(OH)₂ is studied by X-ray powder diffraction and IR spectroscopy. According to X-ray powder diffraction data, single-phase solid solutions Sr_{10 ? x} Ba _x (VO₄)₆(OH)₂ are formed with x = 0–2.5 with an increase in the unit cell parameters.     

Synthesis and heat capacity of NdVO<Subscript>4</Subscript> in the temperature range of 384–859 K

Heat capacity of NdVO₄ was determined in the temperature range of 384–859 K using differential scanning calorimetry. The thermodynamic functions (H°(T)–H°(384 K), S°(T)–S°(384 K), and Φ°) of neodymium orthovanadate were calculated using the experimental C_p = f(T) values. The structure of NdVO₄ was studied at 298 and 973 K.     

The thermochemical characteristics of solution of DL-α-alanylglycine and DL-α-alanylalanine in water-alcohol mixtures at 298.15 K

The integral enthalpies of solution of DL-α-alanylglycine and DL-α-alanylalanine in water-ethanol, water-n-propanol, and water-isopropanol mixtures were measured calorimetrically at alcohol concentrations x ₂ = 0?0.4 mole fractions. The standard enthalpies of solution (Δ_sol H°) of the peptides and their transfer (Δ_tr H°) from water into the mixed solvents were calculated. The influence of the structure and properties of the solutes and mixture composition on the enthalpy characteristics were considered. The Δ_sol H° = f(x ₂) and Δ_tr H° = f(x ₂) dependences were found to have extrema. The enthalpy coefficients of pair interactions (h _xy ) between the peptide and alcohol molecules were calculated. The coefficients were positive and increased in the series ethanol, n-propanol, isopropanol.     

Standard Thermodynamic Functions of Crystalline Arsenate Mg<Subscript>0.5</Subscript>Zr<Subscript>2</Subscript>(AsO<Subscript>4</Subscript>)<Subscript>3</Subscript> in the Range from <Emphasis Type="Italic">T</Emphasis> → 0 to 670 K

The temperature dependence of heat capacity C^° _p = f(T) of crystalline arsenate Mg_0.5Zr₂(AsO₄)₃ was studied by precision adiabatic vacuum and differential scanning calorimetry in the temperature range 8?670 K. The standard thermodynamic functions C^° _p (T), H°(T)–H°(0), S°(T), and G°(T)–H°(0) of the arsenate for the range from Т → 0 to 670 K and the standard formation entropy at Т = 298.15 K were calculated from the obtained experimental data. Based on the low-temperature capacity data (30–50 K) the fractal dimension D of the arsenate was determined, and the topology of its structure was characterized. The results were compared with the thermodynamic data for the structurally related crystalline phosphates M_0.5Zr₂(PO₄)₃ (M = Mg, Ca, Sr, Ba, Ni) and arsenate NaZr₂(AsO₄)₃.     

Synthesis,structural, spectral,thermal and comparative biological activity studies of [V<Subscript>2</Subscript>O<Subscript>2</Subscript>(SO<Subscript>4</Subscript>)<Subscript>2</Subscript>(H<Subscript>2</Subscript>O)<Subscript>6</Subscript>]

The hydrothermal reaction of a mixture of V₂O₅, VCl₃, 2,5-pyridinedicarboxylic acid and diluted H₂SO₄ for 68 h at 180°C gives a blue colored solution which yields prismatic blue crystals of IV ₂ ^IV O₂(SO₄)₂(H₂O)₆] (1) in 32% yield (based on V). Complex 1 was investigated by means of elemental analysis (C, H and S), TGA, FT-IR, manganometric titration, Single Crystal X-ray Diffraction Methods and also comparative antimicrobial activities. Crystal data for the compound: monoclinic space group P2₁/c and unit cell parameters are a = 7.3850(12) Å, b = 7.3990(7) Å, c = 12.229(2) Å, β = 108.976(12)° and Z = 2. Although structure of 1 as a natural mineral has been previously determined, this work covers new preparation method and full characterization of 1 along with comparison of antibacterial activity between 1 and the commercial vanadium(IV) oxide sulfate hydrate compounds, VOSO₄ · xH₂O (Riedel-de Haën and Alfa Aesar brand names). 1 was evaluated for the antimicrobial activity against gram-positive, gram-negative bacteria, yeasts and mould compared with the commercial VOSO₄ · xH₂O compounds. 1 showed weak activity against bacteria Bacillus cereus, Nocardia asteroides and yeast Candida albicans. A good antimicrobial activity was recorded against Cirtobacter freundii (15 mm). There are only a few reproducible well-defined vanadium(IV) starting materials to use for exploring the synthesis of new materials. VCl₄, VO(acac)₂, VOSO₄ · xH₂O and [V(IV)OSO₄(H₂O)₄] · SO₄ · [H₂N(C₂H₄)₂NH₂] are common starting materials for such applications. In addition to these compounds, 1 can be used as an oxovanadium precursor.     

Effects of Cr doping on the electrochemical performance of Li<Subscript>3</Subscript>V<Subscript>2</Subscript>(PO<Subscript>4</Subscript>)<Subscript>3</Subscript> cathode material for lithium ion batteries

A series of Cr-doped Li₃V_2???x Cr _x (PO₄)₃ (x?=?0, 0.1, 0.25, and 0.5) samples are prepared by a sol–gel method. The effects of Cr doping on the physical and chemical characteristics of Li₃V₂(PO₄)₃ are investigated. Compared with the XRD pattern of the undoped sample, the XRD patterns of the Cr-doped samples have no extra reflections, which indicates that Cr enters the structure of Li₃V₂(PO₄)₃. As indicated by the charge–discharge measurements, the Cr-doped Li₃V_2???x Cr _x (PO₄)₃ (x?=?0.1, 0.25, and 0.5) samples exhibit lower initial capacities than the undoped sample at the 0.2 C rate. However, both the discharge capacity and cycling performance at high rates (e.g., 1 and 2 C) are enhanced with proper amount of Cr doping (x?=?0.1). The highest discharge capacity and capacity retention at the rates of 1 and 2 C are obtained for Li₃V_1.9Cr_0.1(PO₄)₃. The improvement of the electrochemical performance can be attributed to the higher crystal stability and smaller particle size induced by Cr doping.     

Crystal structures of <Emphasis Type="Italic">trans</Emphasis>-[Re<Subscript>6</Subscript>S<Subscript>8</Subscript>(CN)<Subscript>2</Subscript>L<Subscript>4</Subscript>] complexes,L = pyridine or 4-methylpyridine

The structures of three novel octahedral rhenium cluster compounds [Re₆S₈(CN)₂(py)₄]·H₂O (1), [Re₆S₈(CN)₂(4-Mepy)₄] (2), [Re₆S₈(CN)₂(4-Mepy)₄]·4-Mepy (3) (py = pyridine, 4-Mepy = 4-methylpyridine) are determined by X-ray crystallography. Crystal data are: C2/m space group, a = 14.813(1) Å, b = 14.772(1) Å, c = 9.2122(6) Å, β = 119.085(2)°, V = 1761.7(2) ų, d _x = 3.318 g/cm³, R = 0.0585 (1); I4₁/amd space group, a = 16.0018(3) Å, c = 14.7186(5) Å, V = 3768.81(16) ų, d _x = 3.169 g/cm³, R = 0.0489 (2); P2₁/c space group, a = 9.0452(4) Å, b = 15.8065(7) Å, c = 15.2951(6) Å, β = 103.700(2)°, V = 2124.57(16) ų, d _x = 2.957 g/cm³, R = 0.0245 (3). Molecular cluster complexes interact via π-π stacking affording 3D frameworks in 1 and 2 and chains in 3.     

Two novel dinuclear iron(III) complexes containing <Emphasis Type="Italic">μ</Emphasis>-oxo-di-<Emphasis Type="Italic">μ</Emphasis>-carboxylato motif

Two novel μ-oxo-di-μ-carboxylato-bridged iron(III) complexes of [Fe₂(bpea)₂(PhCO₂)₂(μ-O)] (ClO₄)₂·C₂H₅OH (1) and [Fe₂(bpma)₂(ClCH₂COO)₂(μ-O)](ClO₄)₂· H₂O (2) (bpea = N,N-bis(2-pyridylmethyl)ethylamine, bpma = N,N-bis(2-pyridylmethyl)methylamine), have been synthesized and determined by X-ray diffraction. Complex (1) crystallizes in the Orthorhombic space group P _nma with d(Fe···Fe) of 3.094 Å and average d(Fe–Ob_bridge) of 1.805 Å; Complex (2) crystallizes in the Monoclinic space group C ₂/c, with d(Fe···Fe) of 3.109 Å and average d(Fe–Ob_bridge) of 1.794 Å. The magnetic studies indicate a stronger antiferromagnetic interaction between iron(III) ions through μ-oxo-di-μ-carboxylato-bridge for complex (1), with J = ? 141.6 cm^?1.     

Study of the effect of methods for liquid-phase synthesis of nanopowders on the structure and physicochemical properties of ceramics in the CeO<Subscript>2</Subscript>–Y<Subscript>2</Subscript>O<Subscript>3</Subscript> system

Two alternative chemical synthesis methods—cryotechnological coprecipitation of hydroxides and cocrystallization of salts—were used for preparing (CeO₂)_1–x (Y₂O₃) _x nanopowders (x = 0.10, 0.15, 0.20) with a mean coherent scattering domain size of ~7–11 nm and S _sp = 2.1–97.5 m²/g. From these nanopowders, ceramic nanomaterials with mean coherent scattering domain sizes of ~61–85 nm were synthesized. It was studied how the phase composition, microstructure, and electrical transport properties of the produced samples depend on the Y₂O₃ content of a CeO₂-based solid solution and on the synthesis method. It was shown that, in the series (CeO₂)_1–x (Y₂O₃) _x (x = 0.10, 0.15, 0.20), the solid solution (CeO₂)_0.90(Y₂O₃)_0.10 has the highest ionic conductivity with the ion transport number t _i = 0.73 (600°C). In its physicochemical characteristics, this ceramic can be used as a solid electrolyte of intermediate-temperature fuel cells.