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.     

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.     

Cationic mobility in Li3?2xNbxFe2?x(PO4)3 complex phosphates

Synthesis and ionic conductivity of Li_3−2x Nb _x Fe_2−x (PO₄)₃ complex phosphates were studied by X-ray powder diffraction and impedance spectroscopy. These phosphates are formed only at 900–1000°C. Variations in their thermal expansivity and unit cell parameters induced by aliovalent doping were characterized. The conductivity of these materials increases monotonically in the series Li_0.5Nb_1.25Fe_0.75(PO₄)₃-LiNbFe(PO₄)₃ and Li_1.2Nb_0.9Fe_1.1(PO₄)₃-Li₃Fe₂(PO₄)₃, which is explained by consecutive occupation of the Li(1) and Li(2) positions in their structures. Original Russian Text ? A.R. Shaikhlislamova, I.A. Stenina, A.B. Yaroslavtsev, 2008, published in Zhurnal Neorganicheskoi Khimii, 2008, Vol. 53, No. 12, pp. 1957–1962.     

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.     

Cation mobility in modified Li1 ? xTi2 ? xNbx(PO4)3 lithium titanium NASICON phosphates

Li_{1 − x} Ti_{2 − x} Nb _x (PO₄)₃ NASICON materials are prepared and studied by X-ray diffraction, ⁷Li and ³¹P NMR spectroscopy, and impedance spectroscopy. Vacancy mobility in Li_{1 − x} Ti_{2 − x} Nb _x (PO₄)₃ is lower than interstitial lithium mobility. Nb⁵⁺ cations with low doping levels increase cation mobility in LiTi₂(PO₄)₃. Original Russian Text ? I.Yu. Pinus, I.A. Stenina, A.I. Rebrov, N.A. Zhuravlev, A.B. Yaroslavtsev, 2009, published in Zhurnal Neorganicheskoi Khimii, 2009, Vol. 54, No. 8, pp. 1240–1244.     

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.     

Conductivity and hydration of lanthanum-substituted barium calcium niobates Ba4 ? xLaxCa2Nb2O11 + 0.5x (x = 0.5; 1; 1.5)

A double perovskite Ba₄(Ca₂Nb₂)O₁₁ known as the oxygen-ionic and protonic conductor is modified by substitution of La atoms for Ba atoms in its composition. Three phases with different lanthanum contents Ba_{4 − x} La _x Ca₂Nb₂O_{11 + 0.5x} with x = 0.5; 1; 1.5 are studied. The temperature dependences of conductivity are measured and the thermogravimetric studies are carried out. The thermogravimetric curves of heating are close for all three compounds, whereas their curves of cooling strongly differ from one another. For compositions with x = 0.5 and 1.5, the dependences of conductivity on the partial oxygen pressure P_O2 P_{O_2 } and the partial water vapor pressure P_{H2 O}P_{H_2 O} are measured. The total transport numbers of ions and the transport numbers of protons are calculated. It is shown that the slope of the logs_tot ( logP_{H2 O} )_Tlog\sigma _{tot} \left( {logP_{H_2 O} } \right)_T dependence reaches 1/3 in the range of medium P_{H2 O}P_{H_2 O} under the condition of electroneutrality 2[O″ _V ] = [H* _i ], which coincides with the result obtained earlier for the Ba₄Ca₂Nb₂O₁₁ (x = 0) composition and the solid solutions on its basis with different Ba/Ca ratios. The obtained results are compared with the literature data describing the incorporation of water into Ba₂In₂O₅ and BaCe_0.89(Y_0.2)O_2.9.     

Ca0.8-2x(YbxTb0.1Na0.1+x)2xWO4近红外下转换荧光粉水热合成及发光性质

一种在近红外光谱(NIR)区域高效的量子剪裁现象已在Ca_0.8-2x(Yb_xTb_0.1Na_0.1+x)_2xWO₄(x=0~0.2)荧光粉中得到证实,该量子剪裁通过吸收紫外线光子发射近红外光子,能量传递包括两个协同过程,分别是WO₄^2-基团到Yb³⁺离子和WO₄^2-基团到Tb³⁺离子再到Yb³⁺离子,Yb³⁺离子的掺杂浓度对荧光粉在可见光和近红外光谱的发光,荧光寿命和量子效率的影响已进行了详细得研究。经计算,量子效率最大达到135.7%。铽与镱共掺钨酸钙的近红外量子剪裁,通过吸收太阳光谱的1个紫外光到2个1000nm光子(2倍光子数增加)的下转化机制实现高效率硅太阳能电池的途径。     

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.     

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.     

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).     

Cation mobility in modified Li1 + xTi2 ? xGax(PO4)3 lithium titanium NASICON phosphates

Li_{1 +x} Ti_{2 − x} Ga _x (PO₄)₃(x= 0−0.2) NASICON double phosphates are prepared and studied by high-temperature X-ray diffraction, ⁷Li NMR spectroscopy, impedance spectroscopy, and calorimetry. Doping with Ga³⁺ cations increases cation mobility in LiTi₂(PO₄)₃. Ion conductivity, NMR spectroscopy, and calorimetry data imply the occurrence of a phase transition in LiTi₂(PO₄)₃ and in products of partial gallium-for-titanium substitution. Original Russian Text ? I.Yu. Pinus, I.V. Arkhangel’skii, N.A. Zhuravlev, A.B. Yaroslavtsev, 2009, published in Zhurnal Neorganicheskoi Khimii, 2009, Vol. 54, No. 8, pp. 1235–1239.     

Ca0.8-2x(YbxTb0.1Na0.1+x)2xWO4近红外下转换荧光粉水热合成及发光性质

一种在近红外光谱(NIR)区域高效的量子剪裁现象已在Ca0.8-2x(Ybx Tb0.1Na0.1+x)2x WO4(x=0～0.2)荧光粉中得到证实,该量子剪裁通过吸收紫外线光子发射近红外光子,能量传递包括两个协同过程,分别是WO42-基团到Yb3+离子和WO42-基团到Tb3+离子再到Yb3+离子,Yb3+离子的掺杂浓度对荧光粉在可见光和近红外光谱的发光,荧光寿命和量子效率的影响已进行了详细的研究。经计算,量子效率最大达到135.7%。铽与镱共掺钨酸钙的近红外量子剪裁,通过吸收太阳光谱的1个紫外光子到2个1 000 nm光子(2倍光子数增加)的下转化机制实现高效率硅太阳能电池的途径。     

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.     

The conditions of formation and physicochemical properties of Nd1 ? xBaxMn1 ? yFeyO3 phases

The homogeneity regions of Nd_{1 − x} Ba _x MnO₃ (0.0 ≤ x ≤ 0.25) and NdMn_{1 − y} Fe _y O₃ (0.0 ≤ y ≤ 1.0) orthorhombic solid solutions in air at 1373 K were determined. The region of the existence of Nd_{1 − x} Ba _x Mn_{1 − y} Fe _y O₃ orthorhombic solid solutions in air at 1373 K was studied. A fragment of the phase diagram of the NdMnO₃-BaMnO₃-BaFeO_2.5-NdFeO₃ quasi-quaternary complex oxide system in air at 1373 K was suggested. The mechanothermal properties of Nd_0.75Ba_0.25MnO₃, Nd_0.8Ba_0.2Mn_0.9Fe_0.1O₃, Nd_0.8Ba_0.2Mn_0.7Fe_0.3O₃, and Nd_0.8Ba_0.2Mn_0.5Fe_0.5O₃ doped neodymium manganates were studied.     

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.     

Region of homogeneity for Lu2 ? xMnxO3 ± δ solid solution in air

The solubility boundaries for Lu₂O₃ and Mn₃O₄ oxides and LuMn₂O₅ manganate in LuMnO_{3 ± δ} are determined on the basis of an X-ray phase analysis of homogeneous solid solutions and heterogeneous compositions with molecular formula Lu_{2 − x} Mn _x O_{3 ± δ} (0.90 ≤ x ≤ 1.16; Δx = 0.02) obtained by ceramic synthesis in air in a temperature range of 900–1400°C. It is found that the solubility of Lu₂O₃ in LuMnO_{3 ± δ} corresponds to the composition of Lu_1.03Mn_0.97O_{3 ± δ} and remains invariable over the investigated range of temperatures, while the solubility of Mn₃O₄ (which corresponds to the composition of Lu_0.91Mn_1.09O_{3 ± δ}) remains invariable in the temperature range of 995–1400°C. It is shown that lutetium manganate LuMn₂O₅ coexists with lutetium manganate LuMnO_{3 ± δ} at temperatures of less than 995°C in air, and its solubility in LuMnO_{3 ± δ} decreases as the temperature of 995°C (corresponding to the composition Lu_0.91Mn_1.09O_{3 ± δ}) falls to 900°C for Lu_0.97Mn_1.03O_{3 ± δ}.     

ZrxTixAl1-2xO2的制备及其在三效催化剂上的应用

Zr_0.5Ti_0.5O₂(ZT) and Zr_0.25Ti_0.25Al_0.5O₂(ZTA) mixed oxides were prepared by co-precipitation method and characterized by low temperature adsorption-desorption， XRD and NH₃-TPD. The activity of Pt/Zr_0.5Ti_0.5O₂ and Pt/ Zr_0.5Ti_0.5Al_0.5O₂ catalysts was evaluated using the simulated gases. The results show that ZTA samples exhibit higher specific surface area， larger pore volume and proper surface acidic amount and acidity in comparison with ZT. The results of the catalytic test indicate that Pt/ZT and Pt/ZTA catalysts exhibit excellent low-temperature catalytic activity and lower light-off temperatures of hydrocarbon， carbon monoxide and nitrogen oxides， especially better conversion for nitrogen oxides (NO_x). The addition of Al₂O₃ into ZT enhanced the anti-aging property of Pt/ ZTA catalysts due to the excellent textural， structural， surface acidity and thermal stability.     

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.