Oxygen-conducting compounds with La2Mo2O9 structure in the ternary system La2Mo2O9-Sm2W2O9-Sm2Mo2O 9 + : Synthesis and properties

Polycrystalline samples in the ternary system La₂Mo₂O₉-Sm₂W₂O₉-Sm₂Mo₂O ₉ ⁺ were synthesized in air. The region of the existence of compounds with the lanthanum molybdate (La₂Mo₂O₉) structure in this system was determined. The polymorphism of the synthesized compounds was studied. Doping with samarium or with samarium and tungsten was shown to lead to the suppression of the transition between the monoclinic and cubic phases α → β and the appearance of the transition β _ms → β between two cubic phases. In samples with a high samarium content, the phase transition β _ms → β manifests itself as significant anomalies in the temperature dependences of the dielectric permeability and electric conductivity. An increase in the concentration of samarium in the samples leads to a substantial decrease in the conductivity compared with the nondoped compound La₂Mo₂O₉.     

Single-crystal structure of vanadium-doped La2Mo2O9

A high-precision X-ray diffraction study of single crystals of two compositions—La₂Mo_1.78V_0.22O_8.89 and La₂Mo_1.64V_0.36O_8.82—was performed. In the vanadium-doped compounds, as in the structure of the metastable β_ms phase of pure La₂Mo₂O₉, the La and Mo atoms and one of the three oxygen atoms are displaced from the threefold axis, on which they are located in the high-temperature β phase. The structure contains two partially occupied oxygen sites. It was shown that molybdenum atoms are partially replaced by vanadium atoms, which are not involved in the disordering, are located on the threefold axis, and are shifted toward one of the oxygen atoms. This is consistent with the temperature-induced changes in the structure of La₂Mo₂O₉ and the changes in the properties of these crystals caused by the introduction of vanadium atoms into the structure.     

Simulation of ion transport in layered cuprate La2SrCu2O6

Oxygen diffusion in layered cuprate La₂SrCu₂O₆ has been simulated by the molecular dynamics method in the temperature range of 300–2500 K. The lattice is found to transform at temperatures above 1550 K; this transformation is accompanied by a change in the pair correlation functions. The abrupt change in the oxygen diffusion coefficient in the range of 1500–1550 K may indicate the presence of a phase transition to the superionic state. The motion of oxygen anions could be traced at the microscopic level. It has been proven for the first time that the La₂SrCu₂O₆ crystal lattice allows, along with displacements of O1 ions within the CuO₂ layer, their migration from the crystallographic positions to the intermediate unoccupied O3 positions. The motion of O2 anions is also fairly complicated: they move not only in their layer over the O2 positions but they also jump to the neighboring layer to occupy the O1 positions. The oxygen diffusion coefficient in layered cuprate La₂SrCu₂O₆ exceeds that in cuprates with perovskite structure and structure of the K₂NiF₄ type (at the same temperatures), which indicates that this material has good prospects for electrodes with mixed ionic-electronic conductivity.     

钙钛矿型层状化合物K2Pr2Ti3O10的合成及XRD研究

在K2CO3-镧系元素氧化物(Pr2O3)-TiO2三元体系中,用固相反应法合成K2Pr2Ti3O10,利用X射线粉晶衍射仪对K2Pr2Ti3O10进行扫描测定,获得X射线衍射数据,进行指标化,得到其晶胞参数。XRD分析结果表明,K2Pr2Ti3O10为四方晶系,空间群I4/mmm。     

Synthesis,structure and optical properties of zinc oxide hexagonal microprisms

Zinc oxide (ZnO) pencil‐head‐like (PHL) microprisms were synthesized by a hydrothermal route using a zinc (Zn) plate as a source and substrate. The structural analysis confirmed the formation of ZnO with hexagonal wurtzite phase on the hexagonal Zn substrate and the growth of the ZnO microparticles along the [101] direction. The room temperature photoluminescence (PL) of the ZnO microprisms showed a sharp UV emission band located at around 380 nm, which is expected to originate from the radiative recombination of free excitons. The sharp UV emission band, with a full width at half‐maximum of about 15 nm and an extremely weak visible emission, confirms the high crystal quality of the synthesized ZnO microprisms. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Crystal structure and electrochemical properties of the supramolecular compound [Himi]6[As2Mo18O62]·11H2O

A supramolecular compound, [Himi]₆[As₂Mo₁₈O₆₂]·11H₂O ( 1 ) (imi = imidazole), has been synthesized and characterized by single crystal X‐ray analysis, IR spectra, thermal gravimetric analysis, electrochemical and elemental analysis. The crystals are monoclinic, P 2(1)/n, a = 14.9529(8) Å, b = 20.9521(11) Å, c = 25.2464(13) Å, β = 93.8130(10)°, V = 7892.1(7) ų, Z = 4. X‐ray diffraction indicated that protonated imidazole cation and polyanion were linked together through electrostatic interactions and intermolecular forces (hydrogen bonding). (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis and crystal structure of Li3.17(P0.69Ge0.24Mo0.07)O4

The crystal structure of Li_3.17(P_0.69Ge_0.24Mo_0.07)O₄, which was synthesized by the flux method under the action of an electric field with a potential difference of 0.8 V, was studied by X-ray diffraction on a Nonius Kappa CCD diffractometer (MoK _α radiation, λ = 0.71073 Å, R = 0.0137). The crystal structure is based on a tetrahedral framework typical of γ-Li₃PO₄. The framework of the new compound is formed by (P,Ge,Mo)O₄ and LiO₄ tetrahedra. The positions of additional Li atoms in the structure of Li_3.17(P_0.69Ge_0.24Mo_0.07)O₄ are found to be different from those in the structure of Li_3.31(P_0.69Ge_0.31)O₄, which is synthesized in the absence of an electric field and also belongs to the γ-Li₃PO₄ structure type.     

Preparation and properties of La2O3–Ga2S3 glass-ceramics for IR materials

IR transmitting glass-ceramics were prepared by isothermal treatments of La₂O₃–Ga₂S₃ glasses. The glass-ceramics were characterized by crystalline phases, microstructure, Vickers hardness and mid (3–5 μm) IR transmittance. The Nd₂S₃-doped La₂O₃–Ga₂S₃ glass-ceramics consisting of a large numbers of (LaO)₄Ga_1.72S_4.58, α-(LaO)GaS₂ and α-Ga₂S₃ crystals with <1 μm in size exhibit a high hardness of 5.3 GPa and a mid IR transparency of >60%.     

Synthesis and crystal structure study of Y2O3 high-pressure polymorph

Single crystal high pressure polymorph of yttria was synthesized for the first time using a link–type cubic anvil apparatus. Crystal structure was refined from single crystal data. High pressure polymorph was confirmed as a monoclinic phase. Lattice parameters of the high pressure polymorph at room temperature and ambient pressure were determined as follows: a = 13.8714 Å, b = 3.4487 Å, c = 8.5862 Å, β = 100.12°.     

Single-crystal structure of vanadium-doped Nd5Mo3O16

The single-crystal structures of the oxygen-ion-conducting fluorite-type compounds Nd₅Mo_2.90V_0.10O_15.3 and Nd₅Mo_2.76V_0.24O_15.5 were determined by X-ray diffraction. It was found that the displacements of atoms in the structure are retained after the doping of these compounds with vanadium. The dopant atoms occupy the molybdenum sites. The X-ray diffraction data were used to calculate the activation energies and analyze the possible pathways for the oxygen ion migration in the structures.     

Single crystal growth of La2(SO4)3 · 9 D2O

Single crystals of La₂(SO₄)₃ · 9 D₂O were grown from saturated D₂O solutions. According to X-ray diffraction measurements, the crystals have a hexagonal structure with unit cell parameters a = 10.996 Å and c = 8.077 Å (space group C–P6₃/m). Several physical properties were also determined (density, refractive indices, dielectric constants, specific heat, coefficient of linear expansion, microhardness).     

Crystal structure of Pr2B5 boride

The crystal structure of Pr₂B₅ boride of a new type was established by single-crystal X-ray diffraction analysis; sp. gr. C2/c, a = 15.1603(4) Å, b = 7.2771(2) Å, c = 7.3137(2) Å, β = 109.607(2)°, 2068 reflections, R _F = 0.041, R _w = 0.055. The Pr₂B₅ structure is similar to the Gd₂B₅ structure.     

Optical properties of nanocomposites with iron core-iron oxide shell structure

Iron nanoparticles of diameter ∼5 nm were produced within a gel-derived silica glass by reducing a suitable gel composition. By heating these composites in the temperature range 573-973 K, Fe₃O₄ shells of a few nanometer thickness were grown around the iron nanoparticles. Three peaks were observed in the optical absorption spectra of the nanocomposites when they were dispersed in ethyl alcohol. The first one around 300 nm was caused by plasma resonance absorption of unoxidized iron particles; the second was shown to be due to the core-shell structure with different permittivities of the two regions and the third one was ascribed to a d-d transition. Detailed analyses of the second peak showed that the extracted values of electrical conductivity were below Mott’s minimum metallic conductivity for iron in the case of particles with diameters below ∼2.5 nm.     

Dielectric properties of ion plated titanium oxide thin films

Titanium oxide thin films have been deposited by an ion plating technique under rf glow. The structure of the deposited film has been found to be amorphous and the composition has been analysed by IR spectrum. Aging and annealing studies of the titanium oxide capacitors have been made. The dielectric constant of the film at 1 kHz has been estimated to be 12.4. The dependence of the capacitance and dielectric loss on frequency and temperature have been studied, and the results are discussed. The temperature coefficient of the capacitance has also been calculated.     

Synthesis and crystal structure of [Nd(H2O)2]2(C2O4)3

Some crystals of [Nd(H₂O)₂]₂(C₂O₄)₃ were synthesized hydrothermally by heating at 200°C for 8 days an aqueous suspension of neodymium oxalate decahydrate in presence of terephthallic acid and guanidinium carbonate. They crystallize in the orthorhombic system, space group P2₁2₁2₁, with a = 8.6702(7) Å, b = 9.558(2) Å, and c = 17.009(2) Å. The structure of this complex is built up by two independent neodymium atoms, three bischelating oxalate ligands, and four water molecules forming a rectangle building unit of 6-membered ring, [Ln(H₂O)₂(C₂O₄)]₆. The packing of these units leads to a layer parallel to the plane (001). However, the neodymium atoms of two neighbor layers share an edge of oxalato oxygen atoms thus giving a double-layer. The three dimensionality between these double-layers is insured by hydrogen bonds of water molecules which are bound to the neodymium atoms. There is no zeolitic water molecule. The two neodymium atoms are nine-coordinated. In both cases, the coordination polyhedron can be described as a distorted tricapped trigonal prism.     

熔盐法合成SrBi2Nb2O9粉体

以分析纯的Bi2O3,Nb2O5 和 SrCO3为原料,以KCl和NaCl为熔盐,采用熔盐法在800～1000 ℃合成了片状SrBi2Nb2O9粉体.研究了熔盐含量及合成温度对晶体定向生长和粉体形貌的影响.结果表明:与固相法相比,熔盐法是一种有效的晶粒定向生长的方法.制备的粉体呈明显的片状和高度的各向异性,且无团聚现象产生.沿(00l)面择优生长适合的熔盐含量为60;质量分数,随着熔盐含量的增加,晶粒尺寸逐渐增大.合成温度在900 ℃为最优,可获得较大尺寸和高度各向异性的SrBi2Nb2O9粉体.     

Synthesis and structure of nanocrystalline La0.50Ba0.50MnO3

Nanocrystalline manganite La_0.50Ba_0.50MnO₃ was synthesized by the soft-chemical method. For this purpose, the sol-gel method was modified and improved. A trihydric saturated alcohol, e.g., glycerol, was suggested as a new organic matrix. The crystal structure of the composite was studied by X-ray powder diffraction at room temperature. A La_0.50Ba_0.50MnO₃ powder annealed in air at T = 500°C is characterized by a perovskite-like cubic structure with the unit-cell parameter a = 3.869 Å. The chemical composition of the sample was studied by electron-probe X-ray microanalysis. The La: Ba: Mn cation ratio in the material was 1: 1: 2. The surface topography was examined with a scanning electron microscope. The crystallite size was ～30 nm. The dependence of the crystal structure and the surface topology on the annealing temperature was studied. The high-temperature treatment in air resulted in the growth of larger, micrometer-size, crystallites.