Concentration Space of Homogeneous Garnet in the System Ga<Subscript>2</Subscript>O<Subscript>3</Subscript>–(Y,Bi)<Subscript>3</Subscript>(Fe,Ga)<Subscript>5</Subscript>O<Subscript>12</Subscript>–Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>

The concentration space of homogeneous garnet in the system Ga₂O₃–(Y, Bi)₃(Fe, Ga)₅O₁₂–Fe₂O₃ was determined by X-ray powder diffraction analysis. The obtained results expand the knowledge of the possible variations of cation ratios Y : Bi : Fe : Ga in garnet, which can be used for searching for and creating new stable magneto-optical materials.     

Reduction of Oxide Mixtures of (Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> + CuO) and (Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> + Co<Subscript>3</Subscript>O<Subscript>4</Subscript>) by Low-Temperature Hydrogen Plasma

The paper presents experimental results pertaining to the reduction of oxide mixtures namely (Fe₂O₃ + CuO) and (Fe₂O₃ + Co₃O₄), by low-temperature hydrogen plasma in a microwave hydrogen plasma set-up, at microwave power 750 W and hydrogen flow rate 2.5 × 10^?6 m³ s^?1. The objective was to examine the effect of addition of CuO or Co₃O₄, on the reduction of Fe₂O₃. In the case of the Fe₂O₃ and CuO mixture, oxides were reduced to form Fe and Cu metals. Enhancement of reduction of iron oxide was marginal. However, in the case of the Fe₂O₃ and Co₃O₄ mixture, FeCo alloy was formed within compositions of Fe₇₀Co₃₀, to Fe₃₀Co₇₀. Since the temperature was below 841 K, no FeO formed during reduction and the sequence of Fe₂O₃ reduction was found to be Fe₂O₃ → Fe₃O₄ → Fe. Reduction of Co₃O₄ preceded that of Fe₂O₃. In the beginning, the reduction of oxides led to the formation of Fe–Co alloy that was rich in Co. Later Fe continued to enter into the alloy phase through diffusion and homogenization. The lattice strain of the alloy as a function of its composition was measured. In the oxide mixture in which excessive amount of Co₃O₄ was present, all the Co formed after reduction could not form the alloy and part of it appeared as FCC Co metal. The crystallite size of the alloy was in the range of 22–30 nm. The crystal size of the Fe–Co alloy reduced with an increase in Co concentration.     

Formation of solid solutions of multiferroics in the Bi<Subscript>2</Subscript>O<Subscript>3</Subscript>–Nd<Subscript>2</Subscript>O<Subscript>3</Subscript>–Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> system

The sequence of phases appearance during the formation of Bi_1–xNd_xFeO₃ solid solutions in powder oxides mixtures of bismuth, neodymium, and iron has been determined. It has been shown that the closeness of the reaction mixture composition to that of the individual compound (BiFeO₃ or NdFeO₃) is essential for the realization of the series of phase transformations yielding solid solutions of multiferroics Bi_1–xNd_xFeO₃ as the final product, due to the prevalence of various interphase contacts in the starting reaction zone.     

Structural and Temperature Dependent Electrical Conductivity Properties of Dy<Subscript>2</Subscript>O<Subscript>3</Subscript>–Sm<Subscript>2</Subscript>O<Subscript>3</Subscript> CO-Doped Bi<Subscript>2</Subscript>O<Subscript>3</Subscript>

In the present work, Dy₂O₃ and Sm₂O₃ double-doped Bi₂O₃-based materials are synthesized by exploiting the solid-state synthesis method. The structural and temperature dependent electrical properties of these ternary ceramic samples, which are candidate materials for solid oxide fuel cell (SOFCs) electrolyte, are determined by means of a powder X-ray diffractometer (XRD), the four point-probe method (FPPM), and the thermal-gravimetry/differential thermal analysis (TG/DTA). As a result of the XRD measurements, the fluorite-type fcc δ-phase with a stable structure is obtained for higher values of the dopant oxide material, which are the samples with the maximum content of fixed 20% Dy₂O₃ and 15% and 20% Sm₂O₃. The samples with the stable δ-phase structure have higher conductivities. The highest electrical conductivity is found for the (Bi₂O₃)0.6(Dy₂O₃)_0.2(Sm₂O₃)_0.2 sample, which was 2.5×10^–2 (Ohm cm)^–1 at 750 °C. The activation energies are also calculated from the Arrhenius charts, which were determined from the FPPM measurements. The lowest activation energy is found as 0.85 eV for the sample with the highest electrical conductivity.     

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.     

Cationic (metallic) “Memory” in double condensed phosphates: Metals Ln-oxides Ln<Subscript>2</Subscript>O<Subscript>3</Subscript>-phosphates MLn(PO)<Subscript>3</Subscript>)<Subscript>4</Subscript> and MLnP<Subscript>4</Subscript>O<Subscript>12</Subscript>

The cationic networks that fix the distribution of cations in planar sections parallel to basis planes of the unit cell of crystal structures have been studied. Topologically identical cationic networks have been shown to be the carriers of deep structure-forming “memory” that successively relates the structures of rare earth metals (La ST) and oxides Ln₂O₃ (A-and B-Ln₂O₃ ST) to the structures of double condensed phosphates MLn(PO₃)₄ and MLnP₄O₁₂.     

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.     

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 properties of γ-Ga<Subscript>2</Subscript>O<Subscript>3</Subscript>–Al<Subscript>2</Subscript>O<Subscript>3</Subscript> solid solutions

The textural and structural properties of mixed oxides Ga₂O₃–Al₂O₃, obtained via impregnating γ-Al₂O₃ with a solution of Ga(NO₃)₃ and subsequent heat treatment, are studied. According to the results from X-ray powder diffraction, gallium ions are incorporated into the structure of aluminum oxide to form a solid solution of spinel-type γ-Ga₂O₃–Al₂O₃ up to a Ga₂O₃ content of 50 wt % of the total weight of the sample, accompanied by a reduction in the specific surface area, volume, and average pore diameter. It is concluded that when the Ga₂O₃ content exceeds 50 wt %, the β-Ga₂O₃ phase is observed along with γ-Ga₂O₃–Al₂O₃ solid solution. ⁷¹Ga and ²⁷Al NMR spectroscopy shows that gallium replaces aluminum atoms from the tetrahedral position to the octahedral coordination in the structure of γ-Ga₂O₃–Al₂O₃.     

New continuous solid solution in the Zn<Subscript>2</Subscript>InV<Subscript>3</Subscript>O<Subscript>11</Subscript>–Mg<Subscript>2</Subscript>InV<Subscript>3</Subscript>O<Subscript>11</Subscript> system

In this study, mechanical activation process was used for intimate mixing as well as producing finely ground particles, increased surface area and improved chemical reactivity of milled materials for producing SrTiO₃ from commercially pure strontium carbonate and TiO₂ as a contributive process. Characterization of milled powder mixture by X-ray diffraction analysis showed that disappearing, decreasing and/or shifting of the patterns occurred with mechanical activation that means amorphization was taken place. Amorphization was also demonstrated by FT-IR analysis where shift of band centers as well as the decrement of transmittance related to CO₃ was observed. Advantage of amorphization was established with high-temperature XRD analysis which showed 1300 °C was not enough for non-activated mixture to form SrTiO₃, whereas structure only composed of SrTiO₃ at 1000 °C for activated ones. The reason for this phenomenon was investigated by DTA-TG analysis, and it was based on energy accumulation originated from mechanical activation that corresponds to peak temperature shifting to the lower temperatures and CO₂ liberation at mechanical activation step arising from local temperature rising at the vial during high-energy milling that was understood from peak temperature, and area decrement of endothermic peak corresponds to decomposition of SrCO₃.     

Modifying additives affect the properties of Y<Subscript>2</Subscript>O<Subscript>3</Subscript>–Al<Subscript>2</Subscript>O<Subscript>3</Subscript>–SiO<Subscript>2</Subscript> system

The effects caused by modifying additives, namely nonionic surfactants (Tween 80 and Neonol AF 9-6) and oxides (B₂O₃ and HfO₂), on the rheology, film formation, and phase formation in the yttrium aluminum silicate system prepared by sol–gel technology were studied. The effect of 1 wt % HfO₂ additions on the activation energy of crystallization was studied.     

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.     

Atmospheric control of gel-oxide transformation in sol–gel derived Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-Y<Subscript>2</Subscript>O<Subscript>3</Subscript> fibers

Via sol–gel processing metal–organic fibers were produced and dried up to 140 °C. For these gel fibers the influence of a treatment in different atmospheres was investigated for the temperature range of 200–850 °C. The atmospheres were nitrogen, water vapor, evaporated nitric and hydrochloric acid and evaporated hydrogen peroxide. In the presence of moisture and especially with acidic moisture fibers were transformed almost completely to their oxide composition (82 mol% Al₂O₃·18 mol% Y₂O₃). In these inorganic amorphous structures considerable differences were observed on several structural levels. On the atomic scale, the coordination of Al ions was investigated by ²⁷Al MAS NMR and skeletal density by He-pycnometry. Porosity in the nm scale was characterized by N₂-sorption. As a macroscopic effect of different treatment atmospheres, the longitudinal shrinkage was observed. For fibers treated at 500 °C the relative shrinkage varied by 100% (comparing water vapor and nitrogen atmosphere). No simple correlation between the release of organic constituents, the formation of porosity and the shrinkage could be found. These aspects were controlled by the rigidity of the inorganic network against atomic reconstitution. The kind of atmosphere was found to be an effective parameter to control various aspects of the xerogel structure.     

Catalytic dehydrogenation of cyclohexene over MoO<Subscript>3</Subscript>/γ-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalysts

A series of MoO₃/γ-Al₂O₃ catalysts with different Mo surface densities (Mo atoms/nm²) has been prepared by incipient wetness impregnation method. Structural characteristics of the prepared catalysts were investigated by atomic absorption spectroscopy, X-ray diffraction, Fourier Transform Infrared spectroscopy, N₂ adsorption at −196 °C, and temperature-programmed reduction (TPR). The catalytic activities of the prepared catalysts were tested by cyclohexene conversion between 200 and 400 °C. XRD results indicated that molybdenum oxide species were dispersed as a monolayer on the support up to 4.04 Mo atoms/nm², and the formation of crystalline MoO₃ was observed above this loading. FTIR and TPR results showed that molybdenum oxide species were present predominantly in tetrahedral form at lower loading, and polymeric octahedral forms were dominant at higher loading. Cyclohexene conversion reaction proceeded mainly through the simple dehydrogenation pathway in the studied temperature range 200–400 °C and was found to be highly dependent on MoO₃ dispersion.     

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.     

Thermal properties of Ga<Subscript>2</Subscript>O<Subscript>3</Subscript>–PbO–P<Subscript>2</Subscript>O<Subscript>5</Subscript> glass system

Thermal behavior of xGa₂O₃–(50 − x)PbO–50P₂O₅ (x = 0, 10, 20, and 30 mol.% Ga₂O₃) and xGa₂O₃–(70 − x)PbO–30P₂O₅ (x = 0, 10, 20, 30, and 40 mol.% Ga₂O₃) glassy materials were studied by thermo-mechanical analysis (TMA) and differential thermal analysis (DTA). Replacement of PbO for Ga₂O₃ is accompanied by increasing glass-transition temperature (263 ≤ T _g/°C ≤ 535), deformation temperature (363 ≤ T _d/°C ≤ 672), crystallization temperature (396 ≤ T _c/°C ≤ 640) and decreasing of coefficient of thermal expansion (5.1 ≤ CTE/ppm K⁻¹ ≤ 16.7). Values of Hruby parameter were determined (0.1 ≤ K _H ≤ 1.3). The thermal stability of prepared glasses increases with increasing of concentration of Ga₂O₃.     

Crystal structure and spectroscopic properties of ciprofloxacinium pentachloroantimonate(III) monohydrate (C<Subscript>17</Subscript>H<Subscript>19</Subscript>N<Subscript>3</Subscript>O<Subscript>3</Subscript>F)SbCl<Subscript>5</Subscript> · H<Subscript>2</Subscript>O

Synthesis, X-ray diffraction, IR and luminescence spectroscopic studies of the monohydrate of pentachloroantimonate(III) of doubly protonated ciprofloxacin (C₁₇H₁₉N₃O₃F)SbCl₅ · H₂O (I) were performed. The structure of I is formed by SbCl₆ octahedra combined into polymeric chains [SbCl₅] _n ^2n? through common vertices, ciprofloxacinium cations (CfH₃)²⁺, and water molecules linked by hydrogen bonds. CfH is protonated at the carbonyl oxygen atom and the terminal nitrogen atom of the piperazinyl group. The electronic and geometric aspects determining the luminescence properties of I and of related compounds are discussed.     

Adsorption of chlorobenzene vapor on V<Subscript>2</Subscript>O<Subscript>5</Subscript>/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalyst under dynamic conditions

Adsorption dynamics of chlorobenzene vapors on a 5% V₂O₅/Al₂O₃ catalyst has been investigated using the frontal chromatography technique. The uptakes of chlorobenzene have been measured as a function of vapor concentration and adsorption equilibrium has been found to follow formally the Langmuir isotherm. The breakthrough time proved to be a linear function of the column length as expected. Breakthrough profiles have been reported for different experimental conditions and quantitatively fitted by a reduced lumped diffusion model. This model provides an analytical solution that facilitates engineering calculations. Model parameters show complex behavior as functions of stream characteristics and depend on column length. When empirical expressions relating model mass transfer coefficients with influencing variables are found the model demonstrates good accuracy in predicting column performance.     

Crystal structure and thermal properties of [Au(en)<Subscript>2</Subscript>]<Subscript>2</Subscript>[Cu(C<Subscript>2</Subscript>O<Subscript>4</Subscript>)<Subscript>2</Subscript>]<Subscript>3</Subscript>·8H<Subscript>2</Subscript>O

The crystal structure of a double complex salt of the composition [Au(en)₂]₂[Cu(C₂O₄)₂]₃·8H₂O (en = ethylenediamine) at 150 K is determined by single crystal X-ray diffraction. The crystal data for C₂₀H₄₈Au₂Cu₃N₈O₃₂ are: a = 9.1761(3) Å, b = 16.9749(6) Å, c = 13.4475(5) Å, β = 104.333(1)°, V = 2029.43(12) ų, P2₁/c space group, Z = 2, d _x = 2.450 g/cm³. It is demonstrated that the thermal decomposition of the double complex salt in a helium or hydrogen atmosphere affords the solid solution Au_0.4Cu_0.6.