Ionic conductivity of Li2B4O7

The formation and mobility of Li point defects in Li(2)B(4)O(7) are investigated theoretically with periodic quantum chemical calculations. Calculated defect formation energies obtained with a density functional theory/Hartree-Fock hybrid method and with the Perdew-Wang density functional method are compared. The basis set effect is investigated by comparison of results obtained with atom-centered basis functions and plane waves. With both methods only a moderate relaxation is observed for the atoms surrounding the Li defect position. The defect-induced change of electronic properties is investigated by calculating the density of states for the stoichiometric and defective supercells. The activation energy for the movement of a Li(+) ion along the (001) direction is calculated. It is observed that Li(+) ion migrates through a one-dimensional channel formed by the five-vertex lithium-oxygen (LiO(5)) polyhedra. The calculated activation energies are in excellent accord with experiment.     

Thermoluminescence and linear thermal expansion of MgAl2O4

The co-efficient of linear thermal expansion (α _av) and dose dependence of thermoluminescence (TL) in MgAl₂O₄(s) were measured. The change in length per unit length was recorded as a function of temperature between room temperature to 1,273 K at a heating rate of 8 K min^?1, in flowing argon atmosphere. The average of three measurements was quoted as the α _av for MgAl₂O₄(s). The linear thermal expansion was measured to an accuracy of ±3 %. The dose dependence of the TL was found to be super linear in the dose range of 0–10 kGy with a k value of 0.503 indicating that the MgAl₂O₄(s) ceramic is ideally suited for the dose estimation of self-irradiated inert matrix fuel in a once through fuel cycle for actinide burning.     

Gibbs energies of formation of MoO2 and Mo4O11

The Gibbs energies of formation of MoO₂ and Mo₄O₁₁ have been determined by means of e.m.f. measurements using the cells Mo, MoO₂/ZrO₂· CaO or ThO₂· Y₂O₃/Fe_0.95O, Fe and Fe, Fe_0.95O/ZrO₂· CaO/Mo₄O₁₁, MoO₂. The data may be represented by the equations ^f ΔG⁰ 〈MoO₂〉 = −571.8 + 0.1662T ± 1.1 (kJ mol⁻¹) between 1070 and 1320 K and ^fΔG^o〈Mo₄O₁₁〉 = −2743 + 0.853T ± 5 (kJ mol⁻¹) between 840 and 1090 K. The enthalpies of formation and standard entropies of MoO₂ and Mo₄O₁₁ at 298 K are calculated by second law evaluations. ^fΔH⁰₂₉₈ 〈MoO₂〉 = −(586 ± 3) kJmol⁻¹S⁰₂₉₈ 〈MoO₂〉 = (49 ± 2) JK⁻¹mol^−1fΔH⁰₂₉₈〈Mo₄O₁₁〉 = −(2807 ± 12) kJmol⁻¹S⁰₂₉₈〈Mo₄O₁₁〉 = (290 ± 15) JK⁻¹mol⁻¹ The Gibbs energies of formation of MoO₂ and Mo₄O₁₁ are given by ^fΔG⁰〈MoO₂〉 = −592 − 0.0387TlogT + 0.303T (kJmol⁻¹) between 298 and 2000 K and ^fΔG⁰〈Mo₄O₁₁〉 = −2776 + 0.886T (kJmol⁻¹) between 298 and 1091 K.     

Chemischer Transport ternärer Oxide in den Systemen Ca/Mo/O und Sr/Mo/O

Chemical Vapour Transport of Ternary Oxides in the Systems Ca/Mo/O and Sr/Mo/O The chemical vapour transport behaviour of ternary phases in the Ca/Mo/O and Sr/Mo/O systems has been investigated using Cl₂ as transport agent in a temperature gradient 1423 to 1323 K. MMoO₄ (M= Ca, Sr) migrate in the above‐mentioned temperature gradient with rates of 0.1 to 0.2 mg/h. Starting from three phase mixtures crystals of the compounds MMo₅O₈ have been grown (migration rates: M = Ca 0.1 mg/h, M = Sr 0.01 mg/h). The observed transport behaviour is compared with predictions given by thermo dynamical model calculations and the influences of source composition and the moisture contents are described in detail.     

Controlled synthesis and size-dependent thermal conductivity of Fe3O4 magnetic nanofluids

The effect of nanoparticle size (4~44 nm) on the thermal conductivities of heat transfer oils has been systematically examined using iron oxide nanoparticles. Such Fe(3)O(4) nanoparticles were synthesized by a simple one-pot pyrolysis method. The size (16~44 nm), shape and assembly patterns of monodisperse Fe(3)O(4) nanoparticles were modulated by only controlling the amount of Fe(acac)(3). After the as-prepared Fe(3)O(4) NPs were dispersed in heat transfer oils, the prepared magnetic nanofluids exhibit higher thermal conductivity than heat transfer oils, and the enhanced values increase with a decrease in particle size. In addition, the viscosities of all nanofliuids are remarkably lower than that of the base fluid, which has been found for the first time in the nanofluid field. The promising features offer potential application in thermal energy engineering.     

Synthesis, structure, negative thermal expansion, and photocatalytic property of Mo doped ZrV2O7

A new series of compounds identified in the phase diagram of ZrO(2)-V(2)O(5)-MoO(3) have been synthesized via the solution combustion method. Single crystals of one of the compounds in the series, ZrV(1.50)Mo(0.50)O(7.25), were grown by the melt-cool technique from the starting materials with double the MoO(3) quantity. The room temperature average crystal structure of the grown crystals was solved using the single crystal X-ray diffraction technique. The crystals belong to the cubic crystal system, space group Pa3 (No. 205) with a = 8.8969 (4) ?, V = 704.24 (6) ?(3), and Z = 4. The final R(1) value of 0.0213 was achieved for 288 independent reflections during the structure refinement. The Zr(4+) occupies the special position (4a) whereas V(5+) and Mo(6+) occupy two unique (8c) Wyckoff positions. Two fully occupied O atoms, (24d) and (4b), one partially occupied O atom (8c) have been identified for this molybdovanadate, which is a unique feature for these crystals. The structure is related to both ZrV(2)O(7) and cubic ZrMo(2)O(8). The temperature dependent single crystal studies show negative thermal expansion above 370 K. The compounds have been characterized by powder X-ray diffraction, solid-state UV-vis diffuse reflectance spectra, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The photocatalytic activity of these compounds has been investigated for the degradation of various dyes, and these compounds show specificity toward the degradation of non-azoic dyes.     

Ionic conductivity of Li2MgSn3O8 ramsdellite

The ionic conductivity of polycrystalline pellets of Li₂MgSn₃O₈ with ramsdellite-type structure was measured by complex impedance technique. The conductivity is 1.2 × 10^?8 (Ω cm)^?1 at 300°C and 2.3 × 10^?4 (Ω cm)^?1 at 450°C. The results are discussed in relation to structural properties.     

La1.95Sr0.05Mo2O9固体电解质的电性质

采用溶胶-凝胶法合成了La1.95Sr0.05Mo2O9固体电解质材料,采用SEM,XRD,交流阻抗谱、气体浓差电池、氧泵等方法对样品进行了表征.结果表明,制得的样品为立方结构;在600～1000℃下氧浓差电池电动势的实测值与理论值吻合得很好,氧离子迁移数为1,表明该陶瓷样品在该温度下氧气气氛中为一纯氧离子导体;离子电导率随温度升高而增大,1000 ℃时达到最大值0.12 S·cm-1.高于相同条件下母体的电导率(0.03 S·cm-1).     

ChemInform Abstract: Preliminary Crystal Structure of Mixed-Valency Sr4Ni3O9, the Actual Formula of the so-called Sr5Ni4O11.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.     

Thermal expansion and impurity effects on lattice thermal conductivity of solid argon

Thermal expansion and impurity effects on the lattice thermal conductivity of solid argon have been investigated with equilibrium molecular dynamics simulation. Thermal conductivity is simulated over the temperature range of 20-80 K. Thermal expansion effects, which strongly reduce thermal conductivity, are incorporated into the simulations using experimentally measured lattice constants of solid argon at different temperatures. It is found that the experimentally measured deviations from a T(-1) high-temperature dependence in thermal conductivity can be quantitatively attributed to thermal expansion effects. Phonon scattering on defects also contributes to the deviations. Comparison of simulation results on argon lattices with vacancy and impurity defects to those predicted from the theoretical models of Klemens and Ashegi et al. demonstrates that phonon scattering on impurities due to lattice strain is stronger than that due to differences in mass between the defect and the surrounding matrix. In addition, the results indicate the utility of molecular dynamics simulation for determining parameters in theoretical impurity scattering models under a wide range of conditions. It is also confirmed from the simulation results that thermal conductivity is not sensitive to the impurity concentration at high temperatures.     

Crystal growth of two new photoluminescent oxides: Sr3Li6Nb2O11 and Sr3Li6Ta2O11

Single crystals of Sr3Li6M2O11 (M = Nb, Ta) were grown out of a high-temperature Sr(OH)2/LiOH/KOH flux. The single crystal X-ray diffraction data were indexed to the orthorhombic Pmma system, with a = 10.5834(15) A, b = 8.3103(13) A, c = 5.8277(8) A, V = 512.55(13) A(3), and Z = 2 for Sr3Li6Nb2O11 and a = 10.5936(6) A, b = 8.3452(5) A, c = 5.8271(4) A, V = 515.15(6) A(3), and Z = 2 for Sr3Li6Ta2O11. The crystal structure consists of sheets of interconnected SrO8 polyhedra that are separated by M-O layers and an intervening LiO(x) polyhedral framework, representing a new structural type. The M-O layers exhibit a rare occurrence of both five- and six-coordinated M(5+) ions in the same structure. The oxides, upon excitation at 250 nm, exhibit violet emission at room temperature.     

Crystal-structure refinement, thermal expansion, and chemical distortion of Bi2Ga4O9

Single crystals of Bi₂Ga₄O₉ are grown from a solution in a bismuth oxide melt. The structure (orthorhombic, space group Pbam, a = 7.918(2) Å, b = 8.299(2) Å, c = 5.894(2) Å, Z = 2) is refined to R = 0.052 in the anisotropic approximation based on single-crystal X-ray diffraction data. The structure is a framework. The bismuth(III) atoms are sixfold coordinated; gallium(III) exists in both tetrahedral and octahedral coordinations. The thermal expansion of Bi₂Ga₄O₉ is studied by high-temperature X-ray powder diffraction method and is found to be sharply anisotropic. A structural interpretation of the anisotropy is proposed. Chemical distortion in the Bi₂M₄O₉ compounds with M = Fe(III), Al, or Ga is analyzed and compared with the thermal expansion of Bi₂Ga₄O₉.     

Strandberg型杂多化合物(C_6H_(11)NH_3)_5H(P_2Mo_5O_(23))4H_2O的水热合成及结构

利用水热合成法合成了分子组成为(C6H11NH3)5H(P2Mo5O23)4H2O的杂多化合物, 用单晶X-ray衍射方法测定了它的结构,该晶体属于单斜晶系,空间群P21/c, a = 12.830(3), b = 14.848(3), c = 25.258(5) ? b = 92.95(3), Mr = 1483.62, V = 4805.1(17) 3, Z = 4, Dc = 2.051 g/cm3, m = 1.431 mm-1, F(000) = 3000, I >2s(I) 的可观察衍射点4426个, 最终结构偏差因子R = 0.0464, wR = 0.0801, S = 0.731。在[P2Mo5O23]6-杂多阴离子中5个MoO6八面体通过共边和共角相连, 形成1个近似的五角平面骨架, 2个PO4四面体加在五角平面的两侧。热性质研究表明杂多阴离子骨架在547.4 ℃左右分解。     

Ionic conductivity of multiarm star polymer/LiClO4 electrolytes

A series of polymer electrolytes based on multiarm polymers and lithium salt complexes were characterized by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and impedance measurement. The relationships of conductivity with salt concentration, temperature, and arm numbers are discussed. It is suggested that the star polymer has a higher solvency and ion transfer ability on lithium salts than on linear polymers. The conductivity maximum appeared at a higher salt concentration ([EO]/[Li] = 4). Impedance measurement suggested that the optimum conductivity was 2 × 10^?4 s · cm^?1. The conductivity increased with temperature and the dependence of ionic conductivity on temperature fits the Arrhenius equation. Among the studied systems, the star polymer with a five arm number performs better than other structures. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4195–4198, 2004     

Crystallization of ultraphosphates via the gas phase. The crystal structures of FeP4O11, ZnP4O11 and CdP4O11

The new ultraphosphates FeP₄O₁₁, ZnP₄O₁₁ and CdP₄O₁₁ of the CuP₄O₁₁ structure type were synthesized from the corresponding meta- or polyphosphates and P₄O₁₁. Crystallization via the gas phase has been achieved at elevated temperatures using a mixture of P (3 mg) and I₂ (50 mg) as mineralizer. The crystal structure consists of a two-dimensional phosphate network, built from four crystallographically independent 10-membered polyphosphate rings. Each ring contains four secondary and six tertiary PO₄-groups. Two crystallographically independent metal sites showing sixfold coordination by terminal oxygen atoms are located inbetween the phosphate layers. FeO₆-octahedra (2.028(3) Å < d̄ FeO₆ < 2.268(3) Å) and ZnO₆ octahedra (2.002(2) Å < d̄ ZnO₆ < 2.256(2) Å) exhibit slightly larger radial distortion than the CdO₆-octahedra (2.215(7) Å < d̄ CdO₆ < 2.383(3) Å).