Interchain Coupling in Quasi-One-Dimensional Superconductors: Homogeneous Coupling and Cross-Linking

In quasi-one-dimensional superconductors a finite amount of electron tunneling between chains is essential to couple the superconducting order parameters on adjacent chains and to obtain thereby a nonzero transition temperature. This paper uses a microscopically derived Ginzburg-Landau theory to investigate the relation between the electron interchain tunneling and the order parameter coupling. Both a homogeneously coupled system and chains cross-linked by randomly distributed short circuits are considered. Application of the theory to (TMTSF) ₂PF₆, shows that a reasonable concentration of short circuits may considerably increase the interchain coupling and may therefore explain the large increase of the transition temperature observed in recent experiments with GaSb-contacts.     

Principal Electrical Conductivities in the Organic Conductors TEA.(TCNQ)2 and TTF.TCNQ: The Microwave Approach

Abstract

We describe a microwave technique to measure the directions and magnitude of the principal electrical conductivities and permittivities of organic conductors. The method is applied to single crystals of triethylammonium-bis 7,7,8,8-tetracyano-p-quinodimethane (TEA.(TCNQ)₂) and of tetrathiafulvalenium-7,7,8,8-tetracyano-p-quinodimethane (TTF.TCNQ). For the former, the apriori set of principal axes (a*, (a*∧c), c) is confirmed with principal conductivities of 430, 5.3 and 0.41–0.77 Ω^?1m^?1 respectively. The room temperature permittivities have been measured for the first time (ε*_α ～ 5.4–5.5, ε*_α∧c ～ 7.5). For the latter it is clearly shown that the principal electrical axes are (a, b, c*) and, in contrary to earlier d.c data, we observe σ_c· < σ<a which is more consistent with the anisotropy of interchain interactions in this compound. The observed transverse and longitudinal anisotropies (～3.3 10² and 2.8 10⁴ respectively) are larger than believed up to now.     

纳米二氧化钛的光催化机理及其在有机废水处理中的应用

本文分析了二氧化钛光催化降解环境污染物的典型催化机理,论述了通过表面改性特别是非金属掺杂后,二氧化钛对自然光响应范围显著提高的一些理论观点.对近年来二氧化钛在主要污染源工业有机废水净化处理中的应用成果进行了评述,对二氧化钛光催化材料的发展趋势进行了展望.     

Charge Transfer in Misfit Layer Chalcogenides, [(MX)n]1+x(TX2)m: a Key for Understanding their Stability and Properties

Abstract

Stability of misfit layer chalcogenides (M.L.C.) is always governed by a charge transfer (C.T.) mechanism. A comparison between M.L.C. and parent intercalated layered binary systems shows comparable characteristics, which illustrate the role of electron donor for the MX part (or its corresponding A-intercalant species) towards the TX² acceptor part. In that way, intercalation chemistry within the vdW gap of multilayered TX² misfit derivatives is also considered. The donor character of the MX part, easy to understand when trivalent M cations are present, can be also assumed if a divalent M cation is partly substituted for a trivalent one, as revealed from precise electron microprobe analysis. Examples of M.L.C. with enlarged MX part (with mixed M^+II, M^+III) emphasize the reality of the C.T. This M-to-T donor effect necessarily controls the transport and intercalation properties.     

Superconductivity in the Organic Charge Transfer Salts: (TMTSF)2X and (TMTTF)2X

Abstract

We report pressure dependent studies of the a-axis resistivity as a function of temperature for several members of the isostructural families of organic charge transfer salts, (TMTSF)₂X and (TMTTF) ₂X. For a typical (TMTSF)₂X material the low temperature metal-insulator transition seen at 1 bar is suppressed above some critical pressure, P_c, where a superconducting transition is observed near 1 K. We find a correlation between P_c and the ambient pressure c lattice parameter which reflects the anion size. The (TMTTF) _cX salts exhibit very different ambient pressure behaviour but we find that with the application of sufficiently high pressures (～30 kbar) their behaviour resembles that seen in the (TMTSF)₂X family but at lower pressures. In particular we find evidence of a possible superconducting transition near 4 K in (TMTTF)₂Br at 25 kbar. At this pressure the conductivity near 4 K is extremely high with a value approaching 10⁶ (Ωcm)^?1 and the resistivity ratio is about 400.     

生物质炭的制备、功能改性及去除废水中有机污染物研究进展

生物质炭具有原材料来源广泛、比表面积大、孔隙结构丰富、表面官能团易调控等优势,在有机污染废水处理领域展现良好的应用前景。然而,生物质炭的不同原材料、制备方法、改性措施等在很大程度上影响着生物质炭的物化性质,从而对有机污染废水表现出不同的性能和作用机制。本文主要基于生物质炭结构特性,针对其制备方法、改性手段和措施展开叙述,并总结了生物质炭用于有机污染废水处理的现状和未来发展机遇。     

Transport and Magnetotransport in the New Quasi-Two-Dimensional Organic Metal (BETS)2ZnBr4(C6H4Cl2) with Different Electron Structure of Neighboring Cation Layers

Intralayer and interlayer transports and Shubnikov – de Haas oscillations are investigated in the new dual-layered organic metal (BETS)₄ZnBr₄(C₆H₄Cl₂). It is shown that: a) the interlayer resistance behavior corresponds to incoherent transport; b) the behavior of quantum oscillations is well described by the model of a coherent network of magnetic breakdown orbits. Both the interlayer transport and quantum oscillations are in a good agreement with the theoretical calculation of the zone structure.     

Correlation Between the Impurity Content,the Average Charge State of Chromium Cations and Optical Absorption in Sillenite Crystals Doped by Chromium in Wide Range of Concentrations

Single crystals of sillenites (Bi₁₂SiO₂₀, Bi₁₂TiO₂₀) doped with chromium in a wide range of concentrations from 1 x 10^‐5 up to 1.8 x 10^‐2 wt. % were grown by the Czochralski and top‐seed solution growth (TSSG) techniques. To estimate the content and the average charge state of chromium in the grown crystals the chemical analysis by the modified diphenylcarbazide method was applied. The dependencies of the chromium distribution coefficient, the average charge state of Cr cations, and optical absorption on the Cr concentration were found. Both the shift of the absorption edge toward lower frequencies and the appearance of an additional absorption band in the near IR were observed when the chromium concentration in the crystals was increased. The experimental data suggest that chromium has at least two charge states and occupies probably different positions in the sillenite unit cell.