Thiourea complexes in synthesis of Cd1 ? xZnxS solid solutions

Solid solutions of the CdS-ZnS system deposited as polycrystalline films by aerosol pyrolysis from aqueous solutions of cadmium and zinc thiourea complexes have been studied. The phase composition and solid-phase solubility are dictated by the nature of initial complexes. From solutions of [M(thio)₂(CH₃COO)₂] complexes, sphalerite sulfides are precipitated, which form a continuous solid solution s-Cd_1−x Zn _x S, whereas the use of the [M(thio)₂Cl₂] precursor leads to crystallization of the wurtzite w-Cd_1−x Zn _x S solid solution based on CdS (the homogeneity range 0–20 mol % ZnS) and the s-Cd_1−x Zn _x S solid solution based on zinc sulfide (50–100 mol % ZnS). The structure of the solid phase in the sulfide system is attributed to the specific features of the stereochemistry of complex precursors.     

Combined adsorption of ammonia and oxygen on the surface of solid solutions of CdxHg1 ? xTe

The adsorption of ammonia, oxygen, and the NH₃ + O₂ mixture on solid solutions Cd _x Hg_{1 − x} Te is studied. The low adsorbability of the mixture, as compared to that of the individual components, is established. Conclusions are drawn as to the nature of its active centers. Schemes for the combined adsorption of ammonia and oxygen are proposed. The temperature areas of tentatively highest catalytic activity of CdTe and CdHgTe in the reaction of ammonia oxidation are established. The formation of gaseous nitrogen in the final products is demonstrated. The degree of ammonia’s transformation into nitrogen is 97–99%. It increased with a rise in temperature and did not depend on the initial ammonia concentration.     

Oxygen nonstoichiometry and the thermodynamic properties of manganites Ca1 ? x ? ySrxLayMnO3 ? δ

The content of oxygen in Ca_{0.6 − y} Sr_0.4La _y MnO_{3 − δ}, where y = 0 and 0.05, was determined by coulometric titration over the temperature range 650–950°C at oxygen partial pressure in the gas phase varied from 10⁻⁴ to 1 atm. The results were used to calculate the partial molar enthalpy, Δ$ \bar H $ \bar H _O(δ), and entropy, Δ$ \bar S $ \bar S _O(δ), of oxygen in manganites. Changes in the Δ$ \bar H $ \bar H _O(δ) and Δ$ \bar S $ \bar S _O(δ) dependences caused by the introduction of lanthanum are evidence of the formation of local clusters of the double perovskite type in the Ca_0.6Sr_0.4MnO_{3 − δ} matrix.     

The enthalpies of formation of Sm1 + xBa2 ? xCu3Oy substitution solid solutions

The enthalpies of reactions of Sm_{1 + x} Ba_{2 − x} Cu₃O _y substitution solid solutions (x = 0, 0.1, 0.2, 0.3, 0.7, and 0.8) with 1.07 N HCl were measured at 298.15 K in a hermetic isothermic-shell swinging calorimeter. The results and the literature data were used to calculate the standard enthalpies of their formation from simple substances and binary oxides (Δ_f H _298.15^o and Δ_ox H _298.15^o). The dependence of the enthalpy of formation on the degree of samarium substitution for barium was obtained.     

The enthalpies of formation of substitution solid solutions Pr1 + xBa2 ?xCu3Oy

The enthalpies of reactions of substitution solid solutions Pr_{1 + x} Ba_{2 − x}Cu₃O _y , where x = 0, 0.2, 0.4, 0.6, and 0.9, with 1.07 N HCl were measured at 298.15 K in a hermetic swinging isothermic-shell calorimeter. The results and the literature data were used to calculate the standard enthalpies of formation of solid solutions from the elements and oxides. The dependence of the enthalpy of solid solution formation on the degree of praseodymium substitution for barium (x) was revealed.     

Conductivity of La1 ? xSrxSc1 ? yMgyO3 ? α (x = y = 0.01–0.20) in reducing atmosphere

The ion and proton transfer numbers were measured by emf method in La_{1 − x} Sr _x Sc_{1 − y} Mg _y O_{3 − α} (x = y = 0.01–0.20) system in reducing hydrogen-containing atmosphere in the range of temperatures from 630 to 920°C and pH₂O from 0.61 to 2.65 kPa. Total ionic, proton, and oxygen conductivities of this system was measured as well. The electroconductivity measurements were carried out vs. pO₂ (from air to 10⁻¹⁴ Pa).     

Synthesis and X-ray diffraction study of complex oxides of the Zn2 ? x(ZraSnb)1 ? xFe2xO4 composition

A multicomponent system of complex refractory oxides of the composition Zn_{2 − x} (Zr _a Sn _b )_{1 − x} Fe_2x O₄ (a + b = 1; a: b = 1: 5, 1: 4, 1: 3, 1: 2, 1: 1, 2: 1, 3: 1, 4: 1; x = 0−1.0; Δx = 0.05) was studied by X-ray diffraction. The samples were prepared from oxides of appropriate metals by low-temperature plasma synthesis (hydrogen-oxygen flame). Two phases with wide homogeneity ranges were identified: α phase crystallized in the crystal system of inverse cubic spinel and β phase with the structure of tetragonal spinel. The phase boundaries were found. Structural data are presented for about 100 solid solutions.     

Acid-base properties of the surfaces of CdxHg1–xTe solid solutions

The acid-base properties of actual CdTe and CdHgTe surfaces were investigated by means of non-aqueous conductometric titration for pHpzc determination, mechanochemistry, and UV spectroscopy. It was shown that the alkaline nature of their surface was due to the dissociative adsorption of atmospheric water flowing on the coordination-saturated surface atoms of cadmium with vacancy defects. The adsorbed water was involved in the formation of tellurium oxide TeO₂ and H₂TeO₃ tellurous acid in the dispersion of CdTe and CdHgTe.     

Effects of combined substitution of Dy and Mo or Si on the crystal structures and magnetic properties of Nd1?yDyyFe11?xTiMx (M = Mo, Si) compounds

A series of Nd_1−y Dy _y Fe_11−x TiM_x (M = Mo, Si) alloys have been prepared by arc melting and studied by X-ray diffraction and neutron diffraction. All samples are found to crystallize in the ThMn₁₂-type structure. The lattice parameters a and c and unit cell volume V of Nd_0.5Dy_0.5Fe_11−x TiMo _x alloys increase linearly with increasing content of Mo (x), while the lattice parameters a and c and unit cell volume V of Nd_0.5Dy_0.5Fe_11−x TiSi _x alloys decrease linearly with increasing content of Si(x). In Nd _y Dy_1−y Fe_11−x TiM _x (M = Mo, Si) compounds, Ti and Mo atoms preferentially occupy the 8i sites and Si atoms preferentially occupy the 8j and 8f sites. Magnetic measurements show that the substitution of Fe by either Mo or Si leads to a decrease in the Curie temperature. Supported by the National Natural Science Foundation of China (Grant No. 20775088) and the Foundation of State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences (Grant No. KF2008-06)     

Crystal structures of La1 ? xSr2 + x(GeO4)(V1 ? xMoxO4) (x= 0?0.4) solid solutions

The phase compositions of theLaVO₄-SrMoO₄(1) and Sr₂GeO₄-SrMoO₄ (2) binary systems, which bound the Sr₂GeO₄-LaVO₄-SrMoO₄ (3) ternary system, and the LaSr₂(VO₄)(GeO₄)-Sr₂GeO₄+SrMoO₄ section (4) of system 3 are studied at subsolidus temperatures. Systems 1 and 2 consist of a mixture of the initial compounds, and the La_{1 − x} Sr_{2 + x} (GeO₄)(V_{1 − x} Mo _x O₄) (where 0 ≤ x ≤ 0.4) region of substitutional solid solutions with a palmierite structure is formed in system 3. The unit cell parameters of the solid solutions are determined. The distribution of the lanthanum and strontium cations over two positions of the cationic sublattice is described. Original Russian Text ? V.D. Zhuravlev, V.G. Zubkov, A.P. Tyutyunnik, Yu.A. Velikodnyi, N.D. Koryakin, 2009, published in Zhurnal Neorganicheskoi Khimii, 2009, Vol. 54, No. 1, pp. 135–137.     

Synthesis and study of the properties of K2Y1 ? x ? yEuxTby(MoO4)(PO4) and K2Y1 ? x ? yEuxTby(MoO4)(PO4)1?δ(VO4)δ solid solutions

Al synthesized samples are isostructural and crystallize in the orthorhombic symmetry system, space group Ibca. Particles of the final product of ∼200 nm in size have been obtained. The introduction of the vanadate anion into the matrix composition leads to the lowering of the symmetry of the Eu³⁺ environment and to the rise of the defect luminescence at 450–550 nm because of the unit cell distortion. The luminescence of defects in terbium-europium-containing samples is determined by the sample surface area, which decreases on annealing. The τ, W ₀ and γ parameters of the luminescence kinetics of the samples have been determined.     

Catalytic activity of V-substituted Cs2Te0.2H0.6 + xPMo12 ? xVxOn heteropoly compounds in selective oxidation of isobutane

A series of Cs₂Te_0.2H_{0.6 + x} PMo_{12 − x} V _x O _n (x = 0–3) heteropoly compounds has been prepared and tested in the partial oxidation of isobutane. Catalytic tests show that at 350°C very high selectivity to methacrylic acid (60.1%) can be achieved at isobutane conversion of 12.2% over a Cs_2.0Te_0.2H_1.6PMo₁₁VO _n catalyst with only one molybdenum atom per unit cell substituted by vanadium. The presence of Te⁴⁺ in the heteropoly compounds appears to interfere with the dehydrqgenation step and favor the formation of methacrolein and methacrylic acid.     

凝胶自燃法合成LaxSr1-x CoyFe1-y O3-α纳米粉体

用凝胶自燃法制备了La_xSr_1-x Co_yFe_1-y O_3-α纳米粉体，研究了粉体的元素组成和掺杂性能，表征了粉体的晶相结构，测试了其粒度和形貌。结果表明应用凝胶自燃工艺合成的La_xSr_1-x Co_yFe_1-y O_3-α粉体材料粒子大小非常均匀，元素掺杂性能好，晶相单一，不需经高温热处理便能直接形成钙钛矿型结构。     

纳米钙钛矿LaxSr1-xFe1-yCoyO3复合氧化物的制备和表征

用甘氨酸-硝酸盐燃烧合成法，制备La_xSr_1-xFe_1-yCo_yO₃复合氧化物的陶瓷粉末，对该钙钛矿型氧化物进行了XRD、IR、紫外漫反射光谱及循环伏安曲线分析。结果表明：该复合氧化物粉体平均晶粒为15.3～29.8 nm,为立方和正交晶系。该氧电极具有双功能催化特性，但不完全可逆。对水溶液染料进行光解实验，利用紫外-可见、人工神经网络光度法研究La_xSr_1-xFe_1-yCo_yO₃的催化性能。结果表明：CO²⁺的加入可使La_xSr_1-xFeO₃的光催化活性有所提高，B位离子(Fe³⁺，CO²⁺)改变与加入，使La_xSr_1-xFe_1-yCo_yO₃(x=0.7，0.3；y=0.3，0.9，1)光催化活性高于La_xSr_1-xFeO₃。同时，对5种染料进行紫外光解，在0.75 h，脱色率大于91%，并为动力学一级反应。     

Oxygen species and their reactivity in the mechanochemically prepared substituted perovskites La1 ? xSrxCoO3 ? y (x = 0–1)

The oxygen species and their reactivity in the mechanochemically prepared substituted perovskites La_{1 − x} Sr _x CoO_{3 − y} were studied using temperature-programmed reduction (TPR) of the samples with hydrogen. The experimental data were compared with data on the catalytic activity of the series of La_{1 − x} Sr _x CoO_{3 − y} catalysts in the oxidation of CO, as well as with the real structures and surface compositions of the samples, which were studied in detail previously. As the strontium content was increased, the degree of reduction of the samples increased in the course of TPR and the TPR peaks shifted to the region of lower temperatures, except for the last sample containing no lanthanum (x = 1). An increase in the calcination temperature and time resulted in a decrease in TPR peak intensities and in a shift of the peaks to the region of higher temperatures. A reaction scheme was proposed for the reduction. In accordance with this reaction scheme, Co⁴⁺ in substituted cobaltites was reduced to Co⁰ at temperatures lower than 400°C. In the temperature region of 400–500°C, the Co³⁺ → Co²⁺ bulk reduction, as well as the deep reduction processes Co³⁺ → Co⁰ and Co⁴⁺ → Co⁰, occurred; substitution facilitated the above processes. At temperatures higher than 500°C, Co²⁺ → Co⁰ bulk reduction occurred. The observed reduction of the mechanochemically prepared samples depended on their microstructure, which was described previously. It was found that the activity of the samples in the oxidation of CO depends on the amount of the most weakly bound reactive surface oxygen species, which were removed in TPR with hydrogen to 150°C. No correlation between the amount of strongly bound (lattice) oxygen removed upon TPR and the activity of La_{1 − x} Sr _x CoO_{3 − y} samples in the oxidation of CO was found. Original Russian Text ? I.S. Yakovleva, L.A. Isupova, V.A. Rogov, 2009, published in Kinetika i Kataliz, 2009, Vol. 50, No. 2, pp. 290–299.     

Synthesis, crystal and electronic structures, and thermodynamic characteristics of BaCe1 ? xInxO3 ? x/2 solid solutions

New perovskite oxide phases BaCe_{1 − x} In _x O_{3 − x/2} (x = 0.1–0.8) (space group Pbnm) have been synthesized. The unit cell volume of the resulting solid solutions monotonically decreases with an increase in the degree of substitution of indium for cerium due to the contraction of octahedra in perovskite blocks. The thermodynamic stability of the compound BaCe_0.75In_0.25O_2.875 was studied by the solution calorimetry method, and barium cerates were shown to be thermodynamically stable with respect to binary oxides at room temperature. The structure of occupied and vacant states in BaCe_{1 − x} In _x O_{3 − x/2} was determined on the basis of X-ray emission, absorption, and photoelectron spectra, and the energy gap was estimated at ∼2 eV.     

Synthesis and study of the variable-composition phase Na1?xCo1?xFe1+x(MoO4)3, 0 ≤ x ≤ 0.4, with nasicon structure

The synthesis conditions for variable-composition phase Na_1−x Co_1−x Fe_1+x (MoO₄)₃, 0 ≤ x ≤ 0.4, crystallizing in the nasicon structure type (R $ \bar 3 $ \bar 3 c) were examined. For this phase, the crystallographic parameters were calculated, vibrational spectra were interpreted, and temperature dependence of electrical conductivity, dielectric constant, and dielectric loss tangent were examined.     

Rubidium-conducting solid electrolytes in Rb2 ? 2xFe2 ? xVxO4 system

New solid rubidium-conducting electrolytes based on rubidium monoferrite in the system of Rb_{2 − 2x} Fe_2−x V _x O₄ are synthesized and studied. It is found that introduction of V⁵⁺ ions causes a drastic decrease in the electronic conductivity component prevalent in pure RbFeO₂ with a simultaneous increase in the ionic conductivity. The latter becomes predominant at an increase in the concentration of vanadium. The optimum compositions of the studied electrolytes feature a very high cationic rubidium conductivity (∼1.8 × 10⁻² S cm⁻¹ at 200°C, more than 10⁻¹ S cm⁻¹ at 700°C). The results are compared with the data obtained earlier for similar systems based on RbGaO₂ and RbAlO₂.     

Quantum-chemical study of chlorophosphoranes: II. Structure of molecules of (Cl2)aP(ClnX3?n)e series, and mutual influence of axial and equatorial substituents

The quantum-chemical calculations of the (C₆H₅)₂PCl₃ molecule were performed by the methods RHF/6-31G(d) and MP2/6-31G(d) with complete and partial optimization of its geometry. The results of calculations were used for evaluating the NQR frequencies of ³⁵Cl and the parameters of asymmetry of the of electric field gradient on the ³⁵Cl nuclei of this molecule. According to the results of calculations with the partial optimization of geometry and to the experimental data of ³⁵Cl NQR the bond lengths were found of central atom P in the solid state of this compound. The mutual influence of its axial and equatorial bonds was studied. It is shown that in chlorophosphoranes the ³⁵Cl NQR frequencies of the axial and equatorial chlorine atoms decrease with the decrease in the bond lengths of phosphorus atom.     

Evaluation of specific heat and related thermodynamic properties of Ge1?xSnxSe2.5 (0?≤?x?≤?0.5) glasses

This paper presents the result of thermodynamic studies on Ge_1−x Sn _x Se_2.5 (0 ≤ x ≤ 0.5) glasses using differential scanning calorimetry. The obtained experimental results on phase transformations have been employed to obtain thermodynamic parameters like entropy difference between metastable states in the glassy region, difference of Gibbs free energy, specific heat, entropy between the glassy and the crystalline phase and the enthalpy released during phase transformation (glassy to crystalline). The results yield that, Ge_0.7Sn_0.3Se_2.5 sample is least stable among all the samples. The stability increases on addition of Sn beyond 0.3 at. mass% upto 0.5 at. mass%.