Characterization of solid solutions composed of oxides of Cu,Zn, and Cr for methanol synthesis

Solid solutions of Cu₂O alone and Cu₂O with ZnO or Cr₂O₃ in ZnO · Cr₂O₃ as well as solid solutions of ZnO in Cu₂O · Cr₂O₃ have activities and selectivities for methanol synthesis comparable to solid solutions of Cu₂O in ZnO. Addition of a secondary phase to these solid solutions limits the grain growth and produces higher surface areas.     

Solid Solutions of Europium(III) and Gadolinium(III) Trifluoroacetate Trihydrates as Precursors of Solid Solutions of Europium and Gadolinium Trifluorides

The system Eu(CF₃CO₂)₃-Gd(CF₃CO₂)₃-H₂O, which forms solid solutions Eu_xGd₁-x(CF₃CO₂)₃ · 3H₂O, was studied. The thermolysis of these solutions at 350-360°C yields solid solutions of lanthanide trifluorides. X-ray examination showed that these solid solutions are formed on the basis of the predominantly rhombic phase of Eu(III) and Gd(III) trifluorides.     

Electron spin resonance of diluted solid solutions of Gd2O3 in CeO2

Electron spin resonance spectra of Gd³⁺ in diluted solid solutions of Gd₂O₃ in CeO₂ have been studied at room temperature for Gd concentrations between 0.01 and 1.00 mol%. While in the case of Mn²⁺:CeO₂ samples, both the linewidth and the line intensity go through a maximum between 0.2 and 0.4% Mn and then start to decrease, in the case of Gd³⁺:CeO₂ samples the linewidth and the line intensity increase monotonically with the dopant concentration. This as taken as evidence that in Gd₂O₃-CeO₂ diluted solid solutions there are no clustering effects similar to the ones observed in Mn:CeO₂ solid solutions. It is not clear why clustering effects are present in Mn:CeO₂ solid solutions and not in Gd:CeO₂ solid solutions; however, it seems reasonable to assume that this is due to the fact that the ionic radius of Mn²⁺ (81 pm) is about 25% smaller that that of Gd³⁺ (107.8 pm). In any case, the fact that Gd:CeO₂ solid solutions do not exhibit clustering effects means that ESR linewidth data can be used to estimate the concentration of Gd in CeO₂ samples, as it is possible to do in several solid solutions of paramagnetic ions in ceramic materials. The results also suggest that the range of the exchange interaction between Gd³⁺ ions in CeO₂ is about 0.89 nm.     

Magnetic studies on (U,La)O2+x solid solutions

Magnetic susceptibilities of La_yU_1−yO_2+x solid solutions with fluorite structure were measured from 4.2 K to room temperature. An antiferromagnetic transition was observed for the solid solutions with lanthanum concentration0 ≤ y ≤ 0.3 in both stoichiometric (x = 0) and hypostoichiometric oxygen range (x < 0). From comparison of the magnetic properties of solid solutions with different oxygen amounts (x < 0, x = 0, x > 0), both oxygen vacancies and interstitial oxygens were found to weaken the magnetic exchange interactions between uranium ions. The Ne´el temperature decreased with decreasing uranium concentration. The variation of the Ne´el temperature of (U, La)O₂ solid solutions with uranium concentration was different from that of (U, Th)O₂ solid solutions. The magnetic moment decreased with decreasing uranium concentration. Its rate was larger than that of (U, Th)O₂ solid solutions and was comparable with that of (U, Y)O₂ solid solutions. The oxidation state of uranium in the solid solutions was examined from the magnetic susceptibility data. The uranium ions were found to be in either the tetravalent or the pentavalent state. The effect of magnetic dilution was larger with La₂O₃ than with Y₂O₃ and/or Sc₂O₃.     

A study of the preparation of solid solutions in the system α-Fe2O3Al2O3

In order to elucidate the formation of precipitated iron catalysts for ammonia synthesis, the formation of solid solutions between α-Fe₂O₃ and Al₂O₃ was studied in the temperature range 500–950°C. The Al₂O₃ content in the solid solutions was found to be below 15 mole%. At temperatures of 800–950°C, solid solutions are formed at an appropriate rate. Specimens with relatively large specific surface areas are obtained at 800°C.     

Ionic mobility and electrophysical properties of solid solutions in PbF<Subscript>2</Subscript>–SbF<Subscript>3</Subscript> and PbF<Subscript>2</Subscript>–SnF<Subscript>2</Subscript>–SbF<Subscript>3</Subscript> systems

Ionic mobility and electrical conductivity of solid solutions with fluorite structure, obtained with solid-state approach in PbF₂–SbF₃ and PbF₂–SnF₂–SbF₃ systems, are studied by 19F NMR and electrochemical impedance spectroscopy methods. The 19F NMR spectra parameters, types of ion motions in the fluoride sublattice, and the ionic conductivity magnitude are shown to be determined by the temperature and fluoride concentration in the solid solutions. The solid solution specific conductivity in the PbF₂–SbF₃ and PbF₂–SnF₂–SbF₃ systems at 420–450 K is as high as ~10^–2 S/cm, which allows accounting the solid solutions as a base for preparation of functional materials.     

Thermodynamic study of some solid solutions in the CaOZrO2 system by emf method

The thermodynamic properties of some solid solutions in the CaOZrO₂ system have been investigated by using solid electrolyte galvanic cells of the type: O₂, Pt|CaO, CaF₂|CaF₂ (t_F = 1)| δCaO(1 ? δ)ZrO₂, CaF₂|Pt, O₂. The influence of CaF₂ added in electrodes on the thermodynamic equilibrium was investigated. It was shown that the heterogeneous field with cubic solid solution reaches the composition x = 0.17 mole of CaO. The results indicate that addition of ZrO₂ to the saturated solid solution produces a significant decrease in the activity of CaO. Measured data were used to calculate thermodynamic parameters of reactions with saturated solid solutions Ca_0.17 Zr_0.83 O_1.83, ZrO₂, and CaZrO₃. At temperatures below 820°C, saturated solid solutions have a tendency to decompose into CaZrO₃ and ZrO₂. A comparison of the thermodynamic results with available data on phase relationships in the CaOZrO₂ system is presented. High thermodynamic stability of SrZrO₃ and BaZrO₃ is one of the reasons for the absence of cubic solid solutions in the system MeOZrO₂ (MeSr, Ba).     

Solubility in the NdCl3-LnCl3-HCl-H2O systems (Ln = Sm, Gd) at 25°C

The solubility at 25°C in the NdCl₃-SmCl₃-HCl-H₂O and NdCl₃-GdCl₃-HCl-H₂O quaternary water-salt systems has been studied in 40% hydrochloric acid sections. The NdCl₃-SmCl₃-HCl-H₂O system represents a continuous series of solid solutions (type I solid solutions). The NdCl₃-GdCl₃-HCl-H₂O system is a system with peritonic discontinuity (type V solid solutions). The discontinuity point of the peritonic solution has the following composition (wt %): NdCl₃ · 6H₂O, 1.13; GdCl₃ · 6H₂O, 0.11; HCl, 39.5; H₂O, 59.26.     

Phase equilibria in the systems ZnSMnS,ZnSCuInS2, and MnSCuInS2

Using high purity ZnS, MnS, Cu₂S, and In₂S₃, the binary systems were examined between 400 and 1300°C using evacuated fused silica capsules to contain intermediate mixtures. X-Ray and microscopic examination of samples at room temperature permitted the probable phase relations to be established. The extent of the very important stability regions for zinc blende and wurtzite solid solutions was firmly established and in the system MnSCuInS₂, the stability fields for the intermediate γ-MnS (wurtzite) solid solutions and CuInS₂ solid solutions were determined.     

纳米CexFe1-xO2固溶体的模板法制备及其乙醇水蒸气重整催化性能

以超高比表面炭材料为模板,硝酸盐为氧化物前体,通过改进的模板路线制备了具有较高比表面积的纳米CexFe1-xO2固溶体.采用X射线衍射、拉曼光谱、物理吸附和透射电镜对制备的样品进行了表征.结果表明,α-Fe2O3,CexFe1-xO2固溶体和CeO2的粒子尺寸为5~15nm,CeO2中部分Ce4 离子被Fe3 离子取代,从而形成了CexFe1-xO2固溶体.乙醇水蒸气重整反应结果显示,CexFe1-xO2固溶体比相应的α-Fe2O3和CeO2具有更高的催化活性和对氢气的选择性.     

Optimization of Active Sites via Crystal Phase,Composition, and Morphology for Efficient Low-Iridium Oxygen Evolution Catalysts

Reducing the amount of iridium in oxygen evolution electrocatalysts without compromising their catalytic performances is one of the major requirements in proton-exchange-membrane water electrolyzers. Herein, with the help of theoretical studies, we show that anatase-type TiO₂-IrO₂ solid solutions possess more active iridium catalytic sites for the oxygen evolution reaction (OER) than IrO₂, the benchmark OER catalyst. Note that the same is not observed for their rutile-type counterparts. However, owing to their thermodynamic metastability, anatase-type TiO₂-IrO₂ solid solutions are generally hard to synthesize. Our theoretical studies demonstrate that such catalytically active anatase-type solid-solution phases can be created in situ on the surfaces of readily available SrTiO₃-SrIrO₃ solid solutions during electrocatalysis in acidic solution as the solution can etch away Sr atoms. We experimentally show this with porous SrTiO₃-SrIrO₃ solid-solution nanotubes synthesized by a facile synthetic route that contain 56 % less iridium than IrO₂ yet show an order of magnitude higher apparent catalytic activity for OER in acidic solution.     

Solid solutions in the Nd(CCl3COO)3-Sm(CCl3COO)3-H2O system at 298 K

The water-salt system of neodymium and samarium trichloroacetates, Nd(CCl₃COO)₃-Sm(CCl₃COO)₃-H₂O, has been investigated by the isothermal solubility method at 298 K. The composition of the solid phases is found by the Schreinemakers residues method. The refractive indices, specific volumes, and viscosities of the liquid phases and the refractive indices of the solid residues have been determined. Continuous solid solutions are found to form in the system. Some thermodynamic characteristics have been calculated for the solid solutions.     

Oxygen redistribution during crystal growth of ZrO<Subscript>2</Subscript>-R<Subscript>2</Subscript>O<Subscript>3</Subscript> solid solutions

This paper presents the results of our experimental studies of quantitative redistribution and isotope fractionation of oxygen during the crystal growth of cubic solid solutions based on ZrO₂. The single crystals were grown by directional crystallization of a melt in a cold container. As stabilizing oxides, we used Y₂O₃, Gd₂O₃, and Yb₂O₃ in concentrations of 8–40 mol %. The results showed that the oxygen isotopic growth effects changed depending on the type and content of the stabilizer in the crystals of ZrO₂-R₂O₃ solid solutions.     

Activities and their relation to cation distribution in NiAl2O4MgAl2O4 spinel solid solutions

The activity of NiAl₂O₄ in NiAl₂O₄MgAl₂O₄ solid solutions has been measured by using a solid oxide galvanic cell of the type, Pt, Ni + NiAl₂O₄ + Al₂O₃(α)/CaOZrO₂/Ni + Ni_xMg_1?xAl₂O₄ + Al₂O₃(α). Pt, in the temperature range 750–1150°C. The activities in the spinel solid solutions show negative deviations from Raoult's law. The cation distribution in the solid solutions has been calculated using site preference energies independent of composition for Ni²⁺, Mg²⁺, and Al³⁺ ions obtained from crystal field theory and measured cation disorder in pure NiAl₂O₄ and MgAl₂O₄, and assumi g ideal mixing of cations on the tetrahedral and octahedral positions. The calculated values correctly predict the decrease in the fraction, α, of Ni²⁺ ions on tetrahedral sites for 1>x>0.25, observed by Porta et al. [J. Solid State Chem.11, 135 (1974)] but do not support their tentative evidence for an increase in α for x < 0.25. The measured excess free energy of mixing can be completely accounted for by using either the calculated or the measured cation distributions. This suggests that the Madelung energy is approximately a linear function of composition in the solid solutions. The composition of NiOMgO solid solutions in equilibrium with NiAl₂O₄MgAl₂O₄ solid solutions has been calculated from the results and information available in literature.     

Synthesis and luminescent properties of rare-earth-doped CeO2–CaF2 solid solutions via chemical solution routes

CeO₂–CaF₂ solid solutions were synthesized by a chemical solution method starting from metal acetates, trifluoroacetic acid as a fluorine source, and anhydrous ethanol as a solvent. Precursor gels, which were obtained by drying the resultant ethanolic solution at 110 °C, were heat-treated at a temperature in the range 400–1000 °C in air to obtain powdery products. Elemental analysis by energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy revealed that heating products actually contained cerium, calcium, oxygen, and fluorine. According to X-ray diffraction analysis, possible reaction pathways under high-temperature treatments were considered as initial formation of fluorides (CeF₃ and CaF₂), subsequent oxidation of Ce³⁺ to Ce⁴⁺ in air, and final conversion to fluorite-type Ce–Ca–O–F solid solutions. Doping of Eu³⁺ or Sm³⁺ ions in the solid solutions led to occurrence of their characteristic photoluminescence due to intra-configurational f–f electronic transitions. Photo-excitation was achieved by irradiation with near ultraviolet light mainly through charge transfer from O²⁻ to Ce⁴⁺ in the solid solutions and subsequent energy transfer to the doped ions. Spectral structures of photoluminescence suggested the occupation of Eu³⁺ or Sm³⁺ in Ce⁴⁺ sites with inversion symmetry in the solid solutions.     

Interactions in the NdF<Subscript>3</Subscript>-Nd<Subscript>2</Subscript>O<Subscript>3</Subscript>-MF<Subscript>2</Subscript> (M = Ba,Sr) systems

Isothermal anneals (at 873 K) and powder X-ray diffraction were used to study isothermal sections of phase diagrams of the NdF₃-Nd₂O₃-MF₂ (M = Ba, Sr) systems. In studying the NdF₃-Nd₂O₃-BaF₂ system, classical solid-phase synthesis was supplemented with mechanochemical activation of feedstock mixtures or BaF₂ activated with gaseous hydrogen fluoride was used. In both systems, a solid solution with the fluorite structure based on MF₂ and NdOF phases, a solid solution with the tysonite structure based on NdF₃, and an ordered fluorite-related phase Ba₄Nd₃F₁₇ were found. The NdOF-based solid solutions were shown to have polymorphism: β_trig ai α_cub at ≈800 K; a new trigonal phase of these solid solutions has been discovered. The effect of a dimensional factor $\left( {R_{Ba^{2 + } } > R_{Sr^{2 + } } } \right)$\left( {R_{Ba^{2 + } } > R_{Sr^{2 + } } } \right) on phase formation and unit cell parameters of the solid solutions was traced.     

Ce1－xNdxO2－δ固溶体的电子顺磁共振谱和阻抗谱的研究

利用溶胶-凝胶方法在800 ℃焙烧10 h后, 合成了固溶体Ce_1－xNd_xO_2－δ (x＝0.05～0.55), X射线衍射(XRD)测试表明固溶体已经形成立方萤石结构; 电子顺磁共振谱(EPR)研究表明在固溶体Ce_1－xNd_xO_2－δ中随着掺杂量x的增大, Ce^3＋离子含量减少, 说明掺杂Nd^3＋离子可以抑制Ce^4＋的还原; 交流阻抗谱的测量表明固溶体Ce_0.9Nd_0.1O_2－d 具有离子导电特性, 600和700 ℃时的电导率分别为4.25×10^－3和1.12×10^－2 S•cm^－1, 活化能为0.68 eV.     

Vibrational analysis of chlorinated methylphosphonic acids: Part 2. Vibrational analysis of CHCl2PO3H2 and its anions

The vibrational spectra (IR and Raman) of CHCl₂PO₃H₂ and its anions in H₂O and D₂O solutions are reported. The IR spectra of the solid dibasic sodium and potassium salts, the solid normal and O-deuterated monobasic sodium and potassium salt and the solid normal and O-deuterated acid are discussed. The principal results of the normal coordinate analysis of the compounds are tabulated.     

Synthesis of Solid Solutions in the (1-x)PbZrO3-xK0.5Bi0.5TiO3 System

DTA, TG, XRD and IR methods were used to study the formation of solid solutions in the selected subsolidus range of the PbZrO₃-K_0.5Bi_0.5TiO₃ system by heating mixtures prepared using oxide substrates, i.e. PbO, Bi₂O₃, ZrO₂, TiO₂ and K₂CO₃. It was found that solid solutions are formed in the reaction of PbO and ZrO₂ with intermediate compound, i.e. K_0.5Bi_0.5TiO₃. PbZrO₃ was not found to be formed as an intermediate phase. This revised version was published online in August 2006 with corrections to the Cover Date.     

Stability and activity of Pd nanoparticles on silica and ultradispersed diamond

The influence of the nature of M_nO_m and treatment temperature of zirconia-based systems M_nO_m−ZrO₂ (M=Ca, Ba, Sm, Yb) of approximately equimolar composition on their phase composition and dispersity has been studied. The samples are shown to contain solid solutions based on cubic ZrO₂. Besides, CaZrO₃ perovskite is present in the CaO−ZrO₂ system, and a solid solution based on Sm₂O₃ is present in the Sm₂O₃−ZrO₂ system. The particle sizes in the corresponding solid solutions vary from 25 to 150 ?, while in the perovskite phase they are in the 300–500 ? range, with the treatment temperature increasing from 623 to 1273 K.