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Sample records for tc superconducting oxides

  1. Oxygen stoichiometry and the high Tc superconducting oxides

    International Nuclear Information System (INIS)

    Tarascon, J.M.; Bagley, B.G.

    1989-01-01

    Methods for determining the oxygen content in high Tc materials, such as thermogravimetric analysis and chemical analysis, are discussed. Consideration is given to La-based cuprates, Y-based cuprates, and Bi-based cuprates. Superconducting transition temperatures are analyzed as a function of the Cu(1)-O(4) bond lengths for several different compositions in the Y-based system. 28 references

  2. Raman scattering and luminescence of high-Tc superconducting oxides

    International Nuclear Information System (INIS)

    Eremenko, V.V.; Gnezdilov, V.P.; Fomin, V.I.; Fugol', I.Ya.; Samovarov, V.N.

    1989-01-01

    Raman and luminescence spectra of high-T c superconducting oxides are summarized, mainly YBa 2 Cu 3 O 7-σ and partly La 2-x Ba x CuO 4-σ . In raman spectra we succeeded to distinguish electron scattering to define the energy gap Δ in the superconducting state. The luminescence spectra are due to the emission of oxygen and interaction with conduction electrons. 70 refs.; 13 figs

  3. Critical currents and superconductivity ferromagnetism coexistence in high-Tc oxides

    CERN Document Server

    Khene, Samir

    2016-01-01

    The book comprises six chapters which deal with the critical currents and the ferromagnetism-superconductivity coexistence in high-Tc oxides. It begins by gathering key data for superconducting state and the fundamental properties of the conventional superconductors, followed by a recap of the basic theories of superconductivity. It then discusses the differences introduced by the structural anisotropy on the Ginzburg-Landau approach and the Lawrence-Doniach model before addressing the dynamics of vortices and the ferromagnetism-superconductivity coexistence in high-Tc oxides, and provides an outline of the pinning phenomena of vortices in these materials, in particular the pinning of vortices by the spins. It elucidates the methods to improve the properties of superconducting materials for industrial applications. This optimization aims at obtaining critical temperatures and densities of critical currents at the maximum level possible. Whereas the primary objective is the basic mechanisms pushing the superco...

  4. Upper critical field measurements in high-Tc superconducting oxides

    Science.gov (United States)

    Ousset, J. C.; Bobo, J. F.; Ulmet, J. P.; Rakoto, H.; Cheggour, N.

    We present upper critical field measurements on the superconducting oxides RE Ba2Cu3O7-δ (RE = Y, Gd) performed in a pulsed magnetic field up to 43 T. Values for Hc2 as high as 52 T and 77 T for Y and Gd respectively, are expected at 77 K. However, in order to observe no resistive behaviour up to 43 T the temperature must be decreased down to 50 K. In the case of oxygen deficient systems the magnetoresistance reveals two superconducting phases wich could be related to two different orders of oxygen vacancies. Nous présentons des mesures de champ critique Hc2 sur les supraconducteurs TR Ba 2Cu3O7-δ (TR = Y, Gd) réalisées en champ magnétique pulsé jusqu'à 43 T. Elles permettent de prévoir des valeurs de H c2 de 52 T et 77 T respectivement pour Y et Gd à 77 K. Cependant, pour ne pas observer de comportement résistif jusqu'au champ maximum, il est nécessaire de refroidir l'échantillon jusqu'à 50 K. Dans le cas des systèmes déficients en oxygène (δ important) nous mettons en évidence l'existence de deux phases supraconductrices qui pourraient être dues à deux ordres différents des lacunes d'oxygène.

  5. The stress-strain relationship for multilayers of the high Tc superconducting oxides

    International Nuclear Information System (INIS)

    Hidaka, H.; Yamamura, H.

    1988-01-01

    This paper reports the calculation of the stress-strain relationship for multilayers of the high Tc superconducting oxides. The elucidation of this relationship is expected quite helpful for the preparation of high-quality multilayers of these materials. This calculation is possible to do in the same way of Timoshenko's bi-metal treatment. The authors did computation of the residual stress and strain, and the state of stress and strain for these multilayers has been acquired in detail by this calculation

  6. Physical properties of high-Tc superconducting oxides. Modification of tc using organic dopants. Final report. Proprietes physiques d'oxydes supraconducteurs a haute Tc. Modification de tc sous l'effet de dopants organiques

    Energy Technology Data Exchange (ETDEWEB)

    Brau, A

    1993-01-01

    An attempt was made to significantly modify the Tc transition temperature of certain copper-based superconducting oxides by introducing organic or mineral dopants, and to study the mobility of 300K-carriers in crystallized tallium-base superconducting oxides. Since the critical transition temperature of superconducting oxides is highly influenced by the density of the free carriers they contain, the authors tried making superconducting powders react with either an organic electron acceptor or a mineral compound. The goal was to increase the density of the holes by altering the copper's degree of oxidation. Their preparatory work showed a direct charge-transfer reaction between the electron-donor copper and the acceptor TCNQ and studied the degree to which the electron acceptor can alter the copper's oxidation. Initial results also showed that dopants can affect superconducting Tc and the course of R(T) curves.

  7. Hyperfine interactions in iron substituted high-Tc superconducting oxides

    International Nuclear Information System (INIS)

    Ellis, D.E.; Saitovitch, E.B.; Lam, D.J.

    1991-01-01

    The hyperfine interactions in Fe substituted copper oxide ternary and quaternary compounds with perovskite-related structures are studied, using the Local Density theory in an embedded cluster approach. The self-consistent electronic structure is examined for Cu and Fe sites in a number of plausible local geometries representative of La 2 Cu O 4 , YBa 2 Cu 3 O 7-δ and related materials. Moessbauer isomer shifts, electric fields gradients, magnetic moments, and contact hyperfine fields are presented for comparison with experiment and discussed in light of lattice structure data. (author)

  8. Phases and structural characteristics of high Tc superconducting oxide in (Bi, Pb)-Sr-Ca-Cu-O system

    International Nuclear Information System (INIS)

    Chen, Zuyano; Li, Zhengrong; Qian, Yitai; Zhou, Quien; Cheng, Tingzhu

    1989-01-01

    The various phases, which are responsible for variant maximum d-value including 18.5 angstrom, 15.4 angstrom, 12.2 angstrom, 6.2 angstrom, 3.2 angstrom and possible 9.1 angstrom respectively, observed in high Tc superconducting complex oxide of (Bi,Pb)-Sr-Ca-Cu-O system are reported in this paper according to the result of X-ray diffraction on platelike crystals or crystallites synthesized under different preparation conditions. The phase of tetragonal system with c=3.21 angstrom, a=3.86 angstrom is possible parent structural unit and it is of great significance to the structure constitution of various phases with large lattice parameter c and structural characteristics of superconducting oxide. In view of the above a model of two-dimension stack-up which causes a stack in variant styles along c-axis and constitute various phases with different lattice parameter c is proposed and discussed

  9. On the superconducting phase diagram of high Tc superconductors

    International Nuclear Information System (INIS)

    de la Cruz, F.

    1990-01-01

    The tendency of oxide superconductors to show granularity has been pointed out since the beginning of research on superconductivity in this type of materials. Nevertheless, only very recently the full phase diagram and characteristics of the grains have been determined. In this paper, the authors review and discuss the different critical fields and their relation to the transport of superconducting current. The superconducting response of single crystals of High Tc superconductors is discussed. Special attention is devoted to the behavior of the vortex lattice and, in particular, to the recent discovery of the quenching of H c1 in YBaCuO, several degrees below Tc

  10. Theory of novel normal and superconducting states in doped oxide high-Tc superconductors

    International Nuclear Information System (INIS)

    Dzhumanov, S.

    2001-10-01

    A consistent and complete theory of the novel normal and superconducting (SC) states of doped high-T c superconductors (HTSC) is developed by combining the continuum model of carrier self-trapping, the tight-binding model and the novel Fermi-Bose-liquid (FBL) model. The ground-state energy of carriers in lightly doped HTSC is calculated within the continuum model and adiabatic approximation using the variational method. The destruction of the long-range antiferromagnetic (AF) order at low doping x≥ x cl ≅0.015, the formation of the in-gap states or bands and novel (bi)polaronic insulating phases at x c2 ≅0.06-0.08, and the new metal- insulator transition at x≅x c2 in HTSC are studied within the continuum model of impurity (defect) centers and large (bi)polarons by using the appropriate tight-binding approximations. It is found that the three-dimensional (3d) large (bi)polarons are formed at ε ∞ /ε 0 ≤0.1 and become itinerant when the (bi)polaronic insulator-to-(bi)polaronic metal transitions occur at x x c2 . We show that the novel pseudogapped metallic and SC states in HTSC are formed at x c2 ≤x≤x p ≅0.20-0.24. We demonstrate that the large polaronic and small BCS-like pairing pseudogaps opening in the excitation spectrum of underdoped (x c2 BCS =0.125), optimally doped (x BCS o ≅0.20) and overdoped (x>x o ) HTSC above T c are unrelated to superconductivity and they are responsible for the observed anomalous optical, transport, magnetic and other properties of these HTSC. We develop the original two-stage FBL model of novel superconductivity describing the combined novel BCS-like pairing scenario of fermions and true superfluid (SF) condensation scenario of composite bosons (i.e. bipolarons and cooperons) in any Fermi-systems, where the SF condensate gap Δ B and the BCS-like pairing pseudogap Δ F have different origins. The pair and single particle condensations of attracting 3d and two- dimensional (2d) composite bosons are responsible for

  11. Mechanisms of conventional and high Tc superconductivity

    International Nuclear Information System (INIS)

    Kresin, V.L.; Morawitz, H.; Wolf, S.A.

    1993-01-01

    This book gives a careful and objective review of theories of superconductivity in traditional superconductors, organics, and high Tc cuprates. Of course, the authors do still present their own theories of cuprate superconductivity, but only in the final chapter after other possibilities have been discussed. The book should be especially useful for researchers entering the field of high Tc superconductivity. The reviews of photon mediated pairing and strong coupling theory are very welcome, since much of this material has not been reviewed since the classic 1969 volume edited by Parks. In particular the authors dispel the various myths that phonon mediated pairing leads to upper bounds on Tc. In addition to phonon mediated pairing the book discussed in detail pairing due to exchange of acoustic (demon) plasmons, excitons, or magnetic fluctuations. There have been so many diverse mechanisms based on strong correlation and large U Hubbard models that a book like this can only discuss a limited selection of the main contenders. In particular here the emphasis on Fermi liquid based models no doubt reflects the authors' own point of view. A whole chapter discusses the concepts of induced superconductivity, in the proximity effect, and its application to materials with several different electronic subsystems

  12. Superconductivity in the W-Tc and W2C-Tc systems

    International Nuclear Information System (INIS)

    Giorgi, A.L.

    1985-01-01

    A series of compositions in the W-Tc, W 2 C-Re and W 2 C-Tc systems were prepared and examined for superconductivity. The crystal structure, lattice parameters and superconducting transition temperatures of the W 2 C-Tc are reported for the first time. Similar measurements were made on the W-Tc and W 2 C-Re systems and the results compared with previous published results for these systems. 7 refs., 2 figs., 2 tabs

  13. The Mercereau effect as a guide to the theory of high-Tc superconductivity in rare earth oxide ceramics

    International Nuclear Information System (INIS)

    Chela-Flores, J.; Martin, P.; Rodriguez-Nunez, J.

    1988-08-01

    We emphasize the importance of performing definite experiments on quantum interferometers, basing our work on a phenomenological theory of high-T c superconductivity co-existing with antiferromagnetism. The theory satisfies all the general requirements of previous models, including minimal gauge invariant coupling terms. Yet, since no doping-dependent displacements are implied in the Mercereau diffraction pattern, this phenomenological approach underlines the urgency of performing new experiments in order to guide the theory. (author). 21 refs, 1 fig

  14. High Tc superconducting energy storage systems

    Energy Technology Data Exchange (ETDEWEB)

    Werfel, Frank [Adelwitz Technologiezentrum GmbH (ATZ), Arzberg-Adelwitz (Germany)

    2012-07-01

    Electric energy is basic to heat and light our homes, to power our businesses and to transport people and goods. Powerful storage techniques like SMES, Flywheel, Super Capacitor, and Redox - Flow batteries are needed to increase the overall efficiency, stability and quality of electrical grids. High-Tc superconductors (HTS) possess superior physical and technical properties and can contribute in reducing the dissipation and losses in electric machines as motors and generators, in electric grids and transportation. The renewable energy sources as solar, wind energy and biomass will require energy storage systems even more as a key technology. We survey the physics and the technology status of superconducting flywheel energy storage (FESS) and magnetic energy storage systems (SMES) for their potential of large-scale commercialization. We report about a 10 kWh / 250 kW flywheel with magnetic stabilization of the rotor. The progress of HTS conductor science and technological engineering are basic for larger SMES developments. The performance of superconducting storage systems is reviewed and compared. We conclude that a broad range of intensive research and development in energy storage is urgently needed to produce technological options that can allow both climate stabilization and economic development.

  15. Metallorganic precursors route for high Tc superconducting materials and related phases

    International Nuclear Information System (INIS)

    Beltran-porter, D.; Gonzalez, A.; Sanchis, M.J.; Beltran-porter, A.; Ibanez, R.; Sapina, F.

    1991-01-01

    The adequacy of the precursors approach for high Tc superconducting materials is validated by means of three examples of a new synthesis of mixed oxides which are directly related to the high Tc superconductors. The synthesis temperature is lowered significantly, and the need for extending the classic 'building block' approach is shown. The hypothesis that topochemical reactions from molecular to extended solids are posssible is proven. 28 refs

  16. The Goettingen high-Tc superconductivity research pool: the effects of structure and structural defects on the performance of high-Tc superconductors. Final reports

    International Nuclear Information System (INIS)

    1992-02-01

    The compilation presents the final reports prepared by the various teams of the Goettingen research pool for high-Tc superconductivity. The reports are entitled: Structure and phase transition in high-Tc superconductors (Krebs/Freyhardt). Preparation and critical properties of high-Tc superconductors (Freyhardt/Heinemann/Zimmermann). EMC measurements in high-Tc superconductors (Bormann/Noelting). Phase analysis of the various phases observed in the preparation of high-Tc superconductors (Faupel/Hehenkamp). Positron annihilation in high-Tc superconductors (Hehenkamp). Preparation and characterization of thin films consisting of superconducting oxide ceramics (v. Minnigerode/Samwer). High-Tc superconductivity in monocrystals (Winzer/Beuermann). Microwave conductivity in high-Tc superconductors (Helberg). High-resolution structural analyses in high-Tc superconductors (Kupcik/Bente). Synthesis, structural analyses and spectroscopy of high-Tc superconductors (Bente). Synthesis, monocrystal growing, crystal structure of high-Tc superconductors (Schwarzmann). Ion-beam-aided studies in high-Tc superconductors (Uhrmacher). (orig./MM) [de

  17. High-Tc superconducting electric motors

    International Nuclear Information System (INIS)

    Schiferl, R.; Stein, J.

    1992-01-01

    In this paper, the advantages and limitations of using superconductors in motors are discussed. A synchronous motor with a high temperature superconducting field winding for pump and fan drive applications is described and some of its unique design features are identified. A 10,000 horsepower superconducting motor design is presented. The critical field and current density requirements for high temperature superconducting wire in motors is discussed. Finally, recent progress in superconducting wire performance is presented

  18. Gauge Model of High-Tc Superconductivity

    International Nuclear Information System (INIS)

    Ng, Sze Kui

    2012-01-01

    A simple gauge model of superconductivity is presented. The seagull vertex term of this gauge model gives an attractive potential between electrons for the forming of Cooper pairs of superconductivity. This gauge model gives a unified description of superconductivity and magnetism including antiferromagnetism, pseudogap phenomenon, stripes phenomenon, paramagnetic Meissner effect, Type I and Type II supeconductivity and high-T c superconductivity. The doping mechanism of superconductivity is found. It is shown that the critical temperature T c is related to the ionization energies of elements and can be computed by a formula of T c . For the high-T c superconductors such as La 2-x Sr x CuO 4 , Y Ba 2 Cu 3 O 7 , and MgB 2 , the computational results of T c agree with the experimental results.

  19. Unconventional superconductivity in heavy fermionic and high-Tc superconductors

    International Nuclear Information System (INIS)

    Volovik, G.E.

    1989-01-01

    Splitting of the superconducting transition and glass spectrum in heavy fermion companies and oxide superconductors are discussed. The multicomponent order parameter leads to splitting of transition due to magnetic field, impurities, orthorhombic distortion, etc... Linear specific heat in oxide superconductors may be explained in terms of the Fermi-surface arising in superconducting state if interband is pairing strong enough

  20. Critical current of high Tc superconducting Bi223/Ag tapes

    NARCIS (Netherlands)

    Huang, Y.; ten Haken, Bernard; ten Kate, Herman H.J.

    1998-01-01

    The magnetic field dependence of the critical current of various high Tc superconducting Bi2223/Ag tapes indicates that the transport current is carried through two paths: one is through weakly-linked grain boundaries (Josephson junctions); another is through well-connected grains. The critical

  1. Pressure and high-Tc superconductivity in sulfur hydrides.

    Science.gov (United States)

    Gor'kov, Lev P; Kresin, Vladimir Z

    2016-05-11

    The paper discusses fundamentals of record-TC superconductivity discovered under high pressure in sulfur hydride. The rapid increase of TC with pressure in the vicinity of Pcr ≈ 123GPa is interpreted as the fingerprint of a first-order structural transition. Based on the cubic symmetry of the high-TC phase, it is argued that the lower-TC phase has a different periodicity, possibly related to an instability with a commensurate structural vector. In addition to the acoustic branches, the phonon spectrum of H3S contains hydrogen modes with much higher frequencies. Because of the complex spectrum, usual methods of calculating TC are here inapplicable. A modified approach is formulated and shown to provide realistic values for TC and to determine the relative contributions of optical and acoustic branches. The isotope effect (change of TC upon Deuterium for Hydrogen substitution) originates from high frequency phonons and differs in the two phases. The decrease of TC following its maximum in the high-TC phase is a sign of intermixing with pairing at hole-like pockets which arise in the energy spectrum of the cubic phase at the structural transition. On-pockets pairing leads to the appearance of a second gap and is remarkable for its non-adiabatic regime: hydrogen mode frequencies are comparable to the Fermi energy.

  2. Bec Model of HIGH-Tc Superconductivity in Layered Cuprates

    Science.gov (United States)

    Lomnitz, M.; Villarreal, C.; de Llano, M.

    2013-11-01

    High-Tc superconductivity in layered cuprates is described in a BCS-BEC formalism with linearly-dispersive s- and d-wave Cooper pairs moving in quasi-2D finite-width layers around the CuO2 planes. This yields a closed formula for Tc involving the layer width, the Debye frequency, the pairing energy and the in-plane penetration depth. The new formula has no free parameters and reasonably reproduces empirical values of superconducting Tcs for 11 different layered superconductors over a wide doping regime including YBCO itself as well as other compounds like LSCO, BSCCO and TBCCO. In agreement with the London formalism, the formula also yields a fair description of the Tc dependence of the lower critical magnetic field in highly underdoped YBCO.

  3. Superconductivity of high Tc Scientific revolution?

    International Nuclear Information System (INIS)

    Marquina, J.E.; Ridaura, R.; Gomez, R.; Marquina, V.; Alvarez, J.L.

    1997-01-01

    A short history of superconductivity, since its discovery by Bednorz and Muller to the development of new materials with high transition temperatures, is presented. Further evolvements are analyzed in terms of T.s. Kuhn conceptions expressed in his book. The Structure of Scientific Revolutions. (Author) 4 refs

  4. Electronic properties of high-Tc superconductors. The normal and the superconducting state of high-Tc materials. Proceedings

    International Nuclear Information System (INIS)

    Kuzmany, H.; Mehring, M.; Fink, J.

    1993-01-01

    The International Winter School on Electronic Properties of High-Temperature Superconductors, held between March 7-14, 1992, in Kirchberg, (Tyrol) Austria, was the sixth in a series of meetings to be held at this venue. Four of the earlier meetings were dedicated to issues in the field of conducting polymers, while the winter school held in 1990 was devoted to the new discipline of high-Tc superconductivity. This year's meeting constituted a forum not only for the large number of scientists engaged in high-Tc research, but also for those involved in the new and exciting field of fullerenes. Many of the issues raised during the earlier winter schools on conducting polymers, and the last one on high-Tc superconductivity, have taken on a new significance in the light of the discovery of superconducting C 60 materials. The Kirchberg meetings are organized in the style of a school where experienced scientists from universities, research laboratories and industry have the opportunity to discuss their most recent results, and where students and young scientists can learn about the present status of research and applications from some of the most eminent workers in their field. In common with the previous winter school on high-Tc superconductors, the present one focused on the electronic properties of the cuprate superconductors. In addition, consideration was given to related compounds which are relevant to the understanding of the electronic structure of the cuprates in the normal state, to other oxide superconductors and to fulleride superconductors. Contributions dealing with their preparation, transport and thermal properties, high-energy spectroscopies, nuclear magnetic resonance, inelastic neutron scattering, and optical spectroscopy are presented in this volume. The theory of the normal and superconducting states also occupies a central position. (orig.)

  5. High {Tc} superconductivity: Symmetries and reflections

    International Nuclear Information System (INIS)

    Zhang, S.C.

    1999-01-01

    This is a talk given at the Symposium Symmetries and Reflections, dedicated to Prof. C.N. Yang's retirement. In this talk, the author reflects on his personal interaction with Prof. Yang since his graduate career at SUNY Stony Brook, and his profound impact on his understanding of theoretical physics. He also reviews the SO(5) theory of high T c superconductivity and shows how his collaboration with Prof. Yang in 1990 lead to the foundation of this idea

  6. Optically activated high Tc superconducting microbolometer

    International Nuclear Information System (INIS)

    Yefremenko, V; Gordiyenko, E; Shustakova, G; Bader, S D; Karapetrov, G; Novosad, V

    2006-01-01

    A laser beam, precisely focused on the patterned superconducting structure, was used to nucleate a resistive area that is sensitive to external thermal effects. The electron beam lithography and wet chemical etching were applied as pattern transfer processes in epitaxial Y-Ba-Cu-O films. Two different sensor designs were tested: (i) 3 millimeters long and 40 micrometers wide stripe and (ii) 1.25 millimeters long, and 50 micron wide meander -like structure. It is shown experimentally that scanning the laser beam along the stripe leads to physical displacement of the sensitive area and, therefore may be used as a basis for imaging over a broad spectral range. For example, patterning the superconducting film into a meander structure is equivalent to a two-dimensional detector array. In additional to the simplicity of the detector fabrication sequence (one step mask transfer), a clear advantage of this approach is the simplicity of the read-out process: an image is formed by registering the signal with only two electrical terminals. The proposed approach can be extended for imaging over a wide spectral range

  7. Superatom representation of high-TC superconductivity

    International Nuclear Information System (INIS)

    Panas, Itai

    2012-01-01

    A “super-atom” conceptual interface between chemistry and physics is proposed in order to assist in the search for higher T C superconductors. The plaquettes generating the checkerboard superstructure in the cuprates, the C 60 molecules in K 3 C 60 , and the Mo 6 S 8 2- clusters in Chevrel phase materials offer such candidate super-atoms. Thus, in the present study high-T C superconductivity HTSC is articulated as the entanglement of two disjoint electronic manifolds in the vicinity of a common Fermi energy. The resulting HTSC ground state couples near-degenerate protected local super-atom states to virtual magnons in an antiferromagnetic AFM embedding. The composite Cooper pairs emerge as the interaction particles for virtual magnons mediated “self-coherent entanglement” of super-atom states. A Hückel type resonating valence bond RVB formalism is employed in order to illustrate the real-space Cooper pairs as well as their delocalization and Bose Einstein condensation BEC on a ring of super-atoms. The chemical potential μ BEC for Cooper pairs joining the condensate is formulated in terms of the super-exchange interaction, and consequently the T C in terms of the Neél temperature. A rationale for the robustness of the HTSC ground state is proposed: achieving local maximum “electron correlation entropy” at the expense of non-local phase rigidity.

  8. Solubility study of Tc(IV) oxides

    International Nuclear Information System (INIS)

    Liu, D.J.; Fan, X.H.

    2005-01-01

    The deep geological disposal of the high level radioactive wastes is expected to be a safer disposal method in most countries. The long-lived fission product 99 Tc is present in large quantities in nuclear wastes and its chemical behavior in aqueous solution is of considerable interest. Under oxidizing conditions technetium exists as the anionic species TcO 4 - whereas under the reducing conditions, expected to exist in a deep geological repository, it is generally predicted that technetium will be present as TcO 2 ·nH 2 O. Hence, the mobility of Tc(IV) in reducing groundwater may be limited by the solubility of TcO 2 ·nH 2 O under these conditions. Due to this fact it is important to investigate the solubility of TcO 2 ·nH 2 O. The solubility determines the release of radionuclides from waste form and is used as a source term in radionuclide migration analysis in performance assessment of radioactive waste repository. Technetium oxide was prepared by reduction of a technetate solution with Sn 2 + . The solubility of Tc(IV) oxide has been determined in simulated groundwater and redistilled water under aerobic and anaerobic conditions. The effects of pH and CO 3 2- concentration of solution on solubility of Tc(IV) oxide were studied. The concentration of total technetium and Tc(IV) species in the solutions were periodically determined by separating the oxidized and reduced technetium species using a solvent extraction procedure and counting the beta activity of the 99 Tc with a liquid scintillation counter. The experimental results show that the rate of oxidation of Tc(IV) in simulated groundwater and redistilled water is about (1.49-1.86) x 10 -9 mol/(L·d) under aerobic conditions, but Tc(IV) in simulated groundwater and redistilled water is not oxidized under anaerobic conditions. Under aerobic or anaerobic conditions the solubility of Tc(IV) oxide in simulated groundwater and redistilled water is equal on the whole after centrifugation or ultrafiltration. The

  9. Internal friction around Tc connected with superconductivity in high Tc superconductors

    International Nuclear Information System (INIS)

    Wang Yening

    1993-01-01

    Internal friction and ultrasonic measurements show that there always exists a phase-like transition (PLT) characterized by the jump of lattice parameters at tens degrees above Tc in superconducting YBaCuO, BiSrCaCuO and TlBaCaCuO. Ferroelastic loops and shape memory effect associated with elastic softening invariably occur at the PLT temperature, showing the characteristics of thermoelastic martensitic transition. Internal frictions in KHz of Bi(Pb)SrCaCuO reveal a static hysteretic plateau (Qp -1 ) above Tc that drops linearly with temperature below Tc. The Qp -1 of YBaCuO decreases with decreasing oxygen content. The origin of the hysteretic Qp -1 is attributed to the lattice distortions around the carriers. (orig.)

  10. Muon spin rotation studies of magnetic order and strong magnetic correlations in magnetic and superconducting systems based on the high Tc copper oxide structures

    International Nuclear Information System (INIS)

    Rudnick, J.J.; Filipkowski, M.E.; Tan, Z.; Chamberland, B.; Niedermayer, C.; Weidinger, A.; Golnik, A.; Simon, R.; Rauer, M.; Recknagel, E.; Gluckler, H.; Baines, C.

    1990-01-01

    In this paper the authors review results of a series of muon spin rotation (μSR) studies extending down to milli Kelvin temperatures in order to explore the existence of magnetic correlations below T C in the La 2-x Sr x CuO 4 system. Evidence is presented for the existence of local magnetic fields thought to originate from Cu electronic moments in both superconducting La 2-x Sr x CuO 4 and in superconducting oxygen deficient YBa 2 Cu 3 O 6.6 . μSR results are also presented for oxygen deficient and superconducting GdBa 2 Cu 3 O 6+x samples. Some discussion of the relevance of these results to recent proposals for pairing mechanisms is presented

  11. Solubility of Tc(IV) oxides

    International Nuclear Information System (INIS)

    Liu, D.J.; Fan, X.H.

    2005-01-01

    Full text of publication follows: The deep geological disposal of the high level radioactive wastes is expected to be a safer disposal method in most countries. The long-lived fission product 99 Tc is present in large quantities in nuclear wastes and its chemical behavior in aqueous solution is of considerable interest. Under the reducing conditions, expected to exist in a deep geological repository, it is generally predicted that technetium will be present as TcO 2 .nH 2 O. The solubility of Tc(IV) is used as a source term in performance assessment of radioactive waste repository. Technetium oxide was prepared by reduction of a technetate solution with Sn 2+ . The solubility of Tc(IV) oxide has been determined in simulated groundwater and re-distilled water under aerobic and anaerobic conditions. The effects of pH and CO 3 2- concentration of solution on solubility of Tc(IV) oxide were studied. The concentration of total technetium and Tc(IV) species in the solutions were periodically determined by separating the oxidized and reduced technetium species using a solvent extraction procedure and counting the beta activity of the 99 Tc with a liquid scintillation counter. The experimental results show that the rate of oxidation of Tc(IV) in simulated groundwater and re-distilled water is about (1.49∼1.86) x 10 -9 mol/(L.d) under aerobic conditions, but Tc(IV) in simulated groundwater and re-distilled water is not oxidized under anaerobic conditions. Under aerobic or anaerobic conditions the solubility of Tc(IV) oxide in simulated groundwater and re-distilled water is equal on the whole after centrifugation or ultrafiltration. The solubility of Tc(IV) oxide decreases with the increase of pH at pH 10 and is pH independent in the range 2 -8 to 10 -9 mol/L at 2 3 2- concentration. These data could be used to estimate the Tc(IV) solubility for cases where solubility limits transport of technetium in reducing environments of high-level waste repositories. (authors)

  12. High-Tc superconducting microbolometer for terahertz applications

    Science.gov (United States)

    Ulysse, C.; Gaugue, A.; Adam, A.; Kreisler, A. J.; Villégier, J.-C.; Thomassin, J.-L.

    2002-05-01

    Superconducting hot electron bolometer mixers are now a competitive alternative to Schottky diode mixers in the terahertz frequency range because of their ultra wideband (from millimeter waves to visible light), high conversion gain, and low intrinsic noise level. High Tc superconductor materials can be used to make hot electron bolometers and present some advantage in term of operating temperature and cooling. In this paper, we present first a model for the study of superconducting hot electron bolometers responsivity in direct detection mode, in order to establish a firm basis for the design of future THz mixers. Secondly, an original process to realize YBaCuO hot electron bolometer mixers will be described. Submicron YBaCuO superconducting structures are expitaxially sputter deposited on MgO substrates and patterned by using electron beam lithography in combination with optical lithography. Metal masks achieved by electron beam lithography are insuring a good bridge definition and protection during ion etching. Finally, detection experiments are being performed with a laser at 850 nm wavelength, in homodyne mode in order to prove the feasibility and potential performances of these devices.

  13. Magnetic levitation systems using a high-Tc superconducting bulk magnet

    Energy Technology Data Exchange (ETDEWEB)

    Ohsaki, Hiroyuki [Dept. of Electrical Engineering, Univ. of Tokyo (Japan); Kitahara, Hirotaka [Dept. of Electrical Engineering, Univ. of Tokyo (Japan); Masada, Eisuke [Dept. of Electrical Engineering, Univ. of Tokyo (Japan)

    1996-12-31

    Recent development of high-performance high-Tc bulk superconductors is making their application for electromagnetic force use feasible. We have studied electromagnetic levitation systems using high-Tc bulk superconducting material. In this paper, after an overview of superconducting magnetic levitation systems, with an emphasis on high-Tc bulk superconductor applications, experimental results of a high-Tc bulk EMS levitation and FEM analysis results of magnetic gradient levitation using bulk superconductor are described. Problems to be solved for their application are also discussed. (orig.)

  14. High Tc Superconducting Magnet Excited by a Semiconductor Thermoelectric Element

    Science.gov (United States)

    Kuriyama, T.; Ono, M.; Tabe, S.; Oguchi, A.; Okamura, T.

    2006-04-01

    A high Tc superconducting (HTS) magnet excited by a thermal electromotive force of a thermoelectric element is studied. This HTS magnet has the advantages of compactness, lightweight and continuous excitation in comparison with conventional HTS magnets, because this HTS magnet does not need a large external power source. In this system, a heat input into the cryogenic environment is necessary to excite the thermoelectric element for constant operation. This heat generation, however, causes a rise in temperature of an HTS coil and reduces the system performance. In this paper, a newly designed magnet system which adopted a two-stage GM cryocooler was investigated. It enabled us to control the temperature of a thermoelectric element and that of an HTS coil independently. The temperature of the HTS coil could be kept at 10-20 K at the second stage of the GM cryocooler, while the thermoelectric element could be excited at higher temperature in the range of 50-70 K at the first stage, where the performance of the thermoelectric element was higher. The experimental results on this HTS magnet are shown and the possibility of the thermoelectric element as a main power source of the HTS magnets is discussed.

  15. A novel propulsion method for high- Tc superconducting maglev vehicle

    Science.gov (United States)

    Ma, Guangtong; Wang, Jiasu; Wang, Suyu; Liu, Minxian; Jing, Hua; Lu, Yiyun; Lin, Qunxu

    2008-01-01

    High-Tc superconducting (HTS) maglev is considered as a perfect transportation type because of its unique inherent stability. A direct current (DC) linear motor using the permanent magnet guideway (PMG) as the stator and the on-board coil as the rotor instead of the present inductive or synchronous alternate current (AC) linear motor which has an economic disadvantage due to the necessity to lay primary coil along the guideway is proposed in this paper. In order to modulate the magnetic field under the PMG, an inverse E shape ferromagnetic device (IESFD) core is designed. The possible winding method for the on-board coil is listed, and the analytical result shows that a considerable net ampere force and thus the propulsion force can be generated by this special structure. The influence of the concentrated effect of the IESFD on the maglev performance of HTS bulk is studied by a numerical program, and the results show that the levitation force with the IESFD is 90% of that without. It is also indicated that the load capability and lateral performance of the maglev vehicle combined this propulsion method can be improved thanks to the attractive effect between the IESFD and PMG. The cost of the HTS maglev vehicle will be remarkably reduced and then shorten the distance to practical application with this propulsion method.

  16. Superconducting fluctuations and pseudogap in high-Tc cuprates

    Directory of Open Access Journals (Sweden)

    Alloul H.

    2012-03-01

    Full Text Available Large pulsed magnetic fields up to 60 Tesla are used to suppress the contribution of superconducting fluctuations (SCF to the ab-plane conductivity above Tc in a series of YBa2Cu3O6+x. These experiments allow us to determine the field Hc’(T and the temperature Tc’ above which the SCFs are fully suppressed. A careful investigation near optimal doping shows that Tc’ is higher than the pseudogap temperature T*, which is an unambiguous evidence that the pseudogap cannot be assigned to preformed pairs. Accurate determinations of the SCF contribution to the conductivity versus temperature and magnetic field have been achieved. They can be accounted for by thermal fluctuations following the Ginzburg-Landau scheme for nearly optimally doped samples. A phase fluctuation contribution might be invoked for the most underdoped samples in a T range which increases when controlled disorder is introduced by electron irradiation. Quantitative analysis of the fluctuating magnetoconductance allows us to determine the critical field Hc2(0 which is found to be be quite similar to Hc’ (0 and to increase with hole doping. Studies of the incidence of disorder on both Tc’ and T* allow us to to propose a three dimensional phase diagram including a disorder axis, which allows to explain most observations done in other cuprate families.

  17. Oxide superconducting ribbon and its fabrication process

    International Nuclear Information System (INIS)

    Belouet, C.

    1990-01-01

    A film without cavities, of perovskite type superconducting oxide is deposited by melting on a metal or composite flexible substrate with a rectangular cross section. The film thickness is comprised between 1 and 100 micrometers and orientation of C axis of superconducting crystals is perpendicular to the subtrate [fr

  18. 2005 annual report of MEXT specially promoted research, 'Development of the 4D Space Access Neutron Spectrometer (4SEASONS) and elucidation of the Mechanism of Oxide High-Tc superconductivity'

    International Nuclear Information System (INIS)

    Arai, Masatoshi; Kajimoto, Ryoichi; Nakajima, Kenji; Shamoto, Shin'ichi; Soyama, Kazuhiko; Nakamura, Mitsutaka; Aizawa, Kazuya; Asaoka, Hidehito; Kodama, Katsuaki; Inamura, Yasuhiro; Imai, Yoshinori; Yokoo, Tetsuya; Ino, Takashi; Yamada, Kazuyoshi; Fujita, Masaki; Ohoyama, Kenji; Hiraka, Haruhiro

    2006-11-01

    A research project entitled 'Development of the 4D Space Access Neutron Spectrometer (4SEASONS) and Elucidation of the Mechanism of Oxide High-T c Superconductivity' has started in 2005 (repr. by M. Arai). It is supported by MEXT, Grant-in-Aid for Specially Promoted Research and is going to last until fiscal 2009. The goal of the project is to elucidate the mechanism of oxide high-T c superconductivity by neutron scattering technique. For this purpose, we will develop an inelastic neutron scattering instrument 4SEASONS (4d SpacE AccesS neutrON Spectrometer) for the spallation neutron source in Japan Proton Accelerator Research Complex (J-PARC). The instrument will have 100 times higher performance than existing world-class instruments, and will enable detailed observation of anomalous magnetic excitations and phonons in a four-dimensional momentum-energy space. This report summarizes the progress in the research project in fiscal 2005. (author)

  19. A study on the development of high Tc superconducting materials

    International Nuclear Information System (INIS)

    Won, D. Y.; Hong, G. Y.; Lee, H. G.; Lee, H. J.; Kim, C. J.; Kwon, S. C.; Kim, K. B.; Kang, Y. H.; Chang, I. S.; Choi, M. J.

    1992-01-01

    The major work of this project aims to develop the frictionless superconducting bearing with a high speed. The high magnetization YBaCuO bulk superconductor was prepared by Quasi-melt process. The frictionless superconducting magnetic bearing standed a rotating bar with a speed of 75,000 rpm, which were operated by an electric controller. The low temperature chemical vapor deposition technique was developed. YBaCuO superconducting film showing a superconductivity above 77K was successfully prepared at 650 deg C. Effect of oxygen partial pressure, substrate, deposition temperature on the film properties were also investigated. (Author)

  20. Quasiparticles in the superconducting state of high-Tc metals

    International Nuclear Information System (INIS)

    Amusia, M.Ya.; Shaginyan, V.R.

    2003-01-01

    The behavior of quasiparticles in the superconducting state of high-T c metals within the framework of the theory of superconducting state based on the fermion condensation quantum phase transition is considered. It is shown that the behavior coincides with the behavior of Bogoliubov quasiparticles, whereas the maximum value of the superconducting gap and other exotic properties are determined by the presence of the fermion condensate. If at low temperatures the normal state is recovered by the application of a magnetic field suppressing the superconductivity, the induced state can be viewed as Landau-Fermi liquid. These observations are in good agreement with recent experimental facts [ru

  1. Structural, electronic, superconducting and mechanical properties of ReC and TcC

    Energy Technology Data Exchange (ETDEWEB)

    Kavitha, M.; Priyanga, G. Sudha; Rajeswarapalanichamy, R., E-mail: rajeswarapalanichamy@gmail.com; Santhosh, M. [Department of Physics, N.M.S.S.V.N College, Madurai, Tamilnadu-625019 (India)

    2015-06-24

    The structural, electronic, superconducting and mechanical properties of ReC and TcC are investigated using density functional theory calculations. The lattice constants, bulk modulus, and the density of states are obtained. The calculated lattice parameters are in good agreement with the available results. The density of states reveals that ReC and TcC exhibit metallic behavior at ambient condition. A pressure-induced structural phase transition is observed in both materials.

  2. High-Tc cuprate superconductivity in a nutshell

    International Nuclear Information System (INIS)

    Won, Hyekyung; Haas, Stephan; Parker, David; Maki, Kazumi

    2005-01-01

    Since the discovery of high-T c cuprate superconductivity in 1986 many new experimental techniques and theoretical concepts have been developed. In particular it was shown that the BCS theory of d-wave superconductivity describes semi-quantitatively the high-T c superconductivity. Furthermore, it was demonstrated that Volovik's approach is extremely useful for finding the quasiparticle properties in the vortex state. Here we survey these developments and forecast future directions. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  3. Introduction to superconductivity and high-Tc materials

    International Nuclear Information System (INIS)

    Cyrot, M.; Pavuna, D.

    1991-01-01

    What sets this book apart from other introductions to superconductivity and high-T c materials is its pragmatic approach. In this book the authors describe all relevant superconducting phenomena and rely on the macroscopic Ginzburg-Landau theory to derive the most important results. Examples are chosen from selected conventional superconductors like NbTi and compared to those high-T c materials. The text should be of interest to non-specialists in superconductivity either as a textbook for those entering the field (one semester course) or as researchers in advanced technologies and even some managers of interdisciplinary research projects

  4. Second international Israeli conference on High Tc Superconductivity

    International Nuclear Information System (INIS)

    1993-01-01

    The superconductivity fields covered in this conference are: theory, applications, devices, flux properties high frequencies, Josephson junctions, magnetism, material sciences and physical properties of superconductors, spectroscopy and resonances and thin films

  5. A study on the development of high Tc superconducting materials

    International Nuclear Information System (INIS)

    Won, Dong Yeon; Lee, Hee Gyoun; Kim, Chan Joong

    1990-01-01

    The microstructure, crystal structure and formation kinetics for the superconducting phases were studied in the lead-doped BiSrCaCuO system. The formation kinetics was also investigated in the samples with different Pb/Bi ratio and it was observed that the 30 % Pb addition is most perferable for the formation of the high T c phase. The formation of the high T c phase was delayed by the excessive addition of Pb. The lattice parameter (c) of the unit cell of both low T c and high T c phases increased with increasing Pb content. Superconducting thin film was sucessfully prepared by chemical vapor deposition (CVD). Film deposited on MgO substrate showed a T c , onset of 85 K and did not reach to zero resistivity down to 77 K. Superconducting 124 phase in Y-system, which is more stable than 123 phase at high temperature showed a T c , onser of 84 K. Additionally, 0.1 mole of Pb, Sn and Ca was substituted for yttrium in 124 phase, respectively. For Pb and Sn-subsituted specimens, 124 phase was formed and for Ca substituted specimen, 124 phase was not formed and revealed no superconductivity down to 77 K. For Sn-substituted specimens, 124 phase was formed but showed no superconductivity down to 77 K. (author)

  6. Modal bifurcation in a high-Tc superconducting levitation system

    International Nuclear Information System (INIS)

    Taguchi, D; Fujiwara, S; Sugiura, T

    2011-01-01

    This paper deals with modal bifurcation of a multi-degree-of-freedom high-T c superconducting levitation system. As modeling of large-scale high-T c superconducting levitation applications, where plural superconducting bulks are often used, it can be helpful to consider a system constituting of multiple oscillators magnetically coupled with each other. This paper investigates nonlinear dynamics of two permanent magnets levitated above high-T c superconducting bulks and placed between two fixed permanent magnets without contact. First, the nonlinear equations of motion of the levitated magnets were derived. Then the method of averaging was applied to them. It can be found from the obtained solutions that this nonlinear two degree-of-freedom system can have two asymmetric modes, in addition to a symmetric mode and an antisymmetric mode both of which also exist in the linearized system. One of the backbone curves in the frequency response shows a modal bifurcation where the two stable asymmetric modes mentioned above appear with destabilization of the antisymmetric mode, thus leading to modal localization. These analytical predictions have been confirmed in our numerical analysis and experiments of free vibration and forced vibration. These results, never predicted by linear analysis, can be important for application of high-T c superconducting levitation systems.

  7. Spin dynamics in high-TC superconducting cuprates

    International Nuclear Information System (INIS)

    Bourges, Ph.

    2003-07-01

    This work is dedicated to the detailed investigations of the magnetic resonance peak in the superconducting state of cuprates. The existence of such a peak could be the signature of a mechanism linked to magnetism that could explain high critical temperature superconductivity. Inelastic neutron scattering is an adequate tool for the understanding of cuprate properties because it reveals magnetic fluctuations whose behaviour and variety depend strongly on temperature and on the level of doping. The last part of this work is dedicated to the study of spin dynamics in YBa 2 Cu 3 O 6+x system

  8. High-Tc superconductivity in the d-p electron system

    International Nuclear Information System (INIS)

    Ivanov, V.A.; Zaitsev, R.A.

    1991-01-01

    The relaxation time with spin flip τ s and the parameters ξ, δ, χ of superconducting phase have been calculated on the basis of the kinematical mechanism of superconductivity in strongly correlated oxide models. An inter-relation between the superconducting gap Δ o and the specific heat jump Δ c allowing the experimental verification was obtained and the Ginsburg-Landau equation derived. (author). 8 refs., 2 figs

  9. Laser patterning of superconducting oxide films

    International Nuclear Information System (INIS)

    Gupta, A.; Hussey, B.W.; Koren, G.; Cooper, E.I.; Jagannathan, R.

    1988-01-01

    The focused output of an argon ion laser (514.5 nm) has been used for wiring superconducting lines of Y/sub 1/Ba/sub 2/CU/sub 3/O/sub 7-δ/ using films prepared from nitrate and trifluoroacetate solution precursors. A stoichiometric solution of the precursors is sprayed or spun on to the substrate to form a film. The film is patterned by irradiating in selected areas to convert the irradiated layers to an intermediate oxide or fluoride state, the nonirradiated areas being unchanged. The nonirradiated areas are then dissolved away, leaving a pattern of the oxide or fluoride material. This patterned layer is converted to the superconducting 1-2-3 oxide in a subsequent annealing step. Maskless patterning of superconducting films has also been demonstrated by laser-assisted etching of the films in aqueous KOH solution. Although superconductivity is destroyed when the films are placed in solution, it can be restored after a brief anneal in oxygen

  10. Processing of flexible high-Tc superconducting wires

    International Nuclear Information System (INIS)

    Lee, B.I.; Modi, V.

    1989-01-01

    Wires superconducting at temperatures above 77 K are produced by using YBa 2 Cu 3 O 7 materials. Flexibility was obtained by support from prefabricated fibers or a metallic coating on the extruded YBa 2 Cu 3 O 7 wires. The microstructure, the T c and the critical current densities of the wires were determined. Processing variables and steps are described

  11. Carbon-based superconductors towards high-Tc superconductivity

    CERN Document Server

    Haruyama, Junji

    2014-01-01

    Introduction of Condensed Matter Physics; Spin-state Crossover; Li Ion Battery; Huge Thermoelectric Power; Room-temperature Ferromagnetism; Partially Disordered Antiferromagnetic Transition; Superconductivity; Transport Properties Combined with Charge, Spin, and Orbital; Magnetoresistance and Spin Blocade; Intrinsic Inhomogeneity; Move/diffuse and Charge/discharge Effect.

  12. A high Tc superconducting liquid nitrogen level sensor

    International Nuclear Information System (INIS)

    Jin, J. X.; Liu, H. K.; Dou, S. X.; Grantham, C.; Beer, J.

    1996-01-01

    Full text: The dramatic resistance change in the superconducting-normal transition temperature range enables a high T c superconductor to be considered for designing a liquid nitrogen level sensor. A (Bi,Pb) 2 Sr 2 Ca 2 Cu 3 O 10+x Ag clad superconducting wire is selected and tested as a continuous liquid nitrogen level sensor to investigate the possibility for this application. The (Bi,Pb) 2 Sr 2 Ca 2 Cu 3 O 10+x Ag clad superconducting wire has approximately 110 K critical temperature, with more flexible and stable properties compared with bulk shape ceramic high T c superconductors. The voltage drops across the sensor are tested with different immersion lengths in liquid nitrogen. The accuracy of the HTS sensor is analysed with its dR/dT in the superconducting-normal transition range. The voltage signal is sensitive to liquid nitrogen level change, and this signal can be optimized by controlling the transport current. The problems of the Ag clad superconductor are that the Ag sheath thermal conductivity is very high, and the sensor normal resistance is low. These are the main disadvantages for using such a wire as a continuous level sensor. However, a satisfactory accuracy can be achieved by control of the transport current. A different configuration of the wire sensor is also designed to avoid this thermal influence

  13. Studies of the Tc oxidation states in humic acid solutions

    International Nuclear Information System (INIS)

    Wang Bo; Liu Dejun; Yao Jun

    2010-01-01

    The oxidation state is an important aspect of the speciation of Tc in groundwater that contained organic substances due to it control the precipitation, complexation, sorption and colloid formation behavior of the Tc under HWL geological disposal conditions. In present work, the oxidation states of Tc were investigated using the LaCl 3 coagulation method and solution extraction method in aqueous solutions in which the humic acid concentration range is from 0 to 20 mg L -1 and the Tc (Ⅶ) concentration range is about 10 -8 mol l -1 . The radiocounting of 99 Tc was determined using liquid scintillation spectrometry. The humic acid will influence the radiocounting ratio of 99 Tc apparently, however, the quenching effect can be restrained once keep the volume of the cocktail to about twenty times of the sample volume. The LaCl 3 coagulation methods were carried out for the investigation of Tc oxidation states in humic acid aqueous systems at about pH 8. The tetraphenylarsonium chloride (IPA)-chloroform extraction method was used also simultaneously to investigation the concentrations of Tc (Ⅳ) and Tc (Ⅶ) for the availability of the LaCl 3 precipitation method, and the experimental results demonstrate that tetravalent technetium and pertechnetate concentrations are well agreement with the LaCl 3 precipitation method. These two experimental results demonstrated that Tc (Ⅶ) is very stable in the Tc (Ⅶ)-humic acid system during a 350 days experimental period, and the Tc (Ⅳ) concentrations are very lower, that is indicate that there didn't oxidizing reactions between the Fluka humic acid and Tc (Ⅶ) in aqueous solutions under anaerobic conditions. That is means the presence of humic acids even in anaerobic groundwater is disadvantage for the retardance of radionuclides. (authors)

  14. Studies of Tc oxidation states in humic acid solutions

    International Nuclear Information System (INIS)

    Wang Bo; Liu Dejun; Yao Jun

    2011-01-01

    The oxidation state of Tc is an important aspect of the speciation in groundwater which contained organic substances due to it control the precipitation, complexation, sorption and colloid formation behavior of the Tc under HWL geological disposal conditions. In present work, the oxidation states of Tc were investigated using the LaCl 3 coagulation method and solution extraction method in aqueous solutions in which the humic acid concentration range is from 0 to 20 mg/L and the Tc (VII) concentration is about 10 -8 mol/L. The radiocounting of 99 Tc was determined using liquid scintillation spectrometry. The humic acid will influence the radiocounting ratio of 99 Tc apparently, however, the quenching effect can be restrained once keep the volume of the cocktail to about twenty times of the sample volume. The LaCl 3 coagulation method was carried out for the investigation of Tc oxidation states in humic acid aqueous systems at about pH 8. The tetraphenylarsonium chloride (TPA)-chloroform extraction method was used also simultaneously to investigation the concentrations of Tc (IV) and Tc (VII) for the availability of the LaCl 3 precipitation method, and the experimental results demonstrate that tetravalent technetium and pertechnetate concentration are well agreement with the LaCl 3 precipitation method. These two experimental results demonstrated that Tc (VII) is very stable in the Tc (VII)-humic acid system during a 350 days experimental period, and the Tc (IV) concentrations are very lower, that is indicate that there didn't oxidizing reactions between the Fluka humic acid and Tc (VII) in aqueous solutions under anaerobic conditions. That means the presence of humic acids even in anaerobic groundwater is disadvantage for the retardance of radionuclides. (authors)

  15. Analysis of eddy current loss in high-Tc superconducting power cables with respect to various structure of stabilizer

    International Nuclear Information System (INIS)

    Choi, S. J.; Song, M. K.; Lee, S. J.; Cho, J. W.; Sim, K. D.

    2005-01-01

    The High-Tc superconducting power cable consists of a multi-layer high-Tc superconducting cable core and a stabilizer which is used to bypass the current at fault time. Eddy current loss is generated in the stabilizer in normal operating condition and affects the whole system. In this paper, the eddy current losses are analyzed with respect to various structure of stabilizer by using opera-3d. Moreover, optimal conditions of the stabilizer are derived to minimize the eddy current losses from the analyzed results. The obtained results could be applied to the design and manufacture of the high-Tc superconducting power cable system.

  16. The stability of high-Tc BSCCO/Ag superconducting microcomposites in water, some inorganic solutions and organic solvents

    International Nuclear Information System (INIS)

    Gao, W.; Chen, J.; Yang, C.O.; McNabb, D.; Sande, J. vander

    1992-01-01

    Bi(Pb)-Sr-Ca-Cu-O/Ag (BSCCO/Ag) superconducting microcomposites with zero-resistance temperatures from 102 to 108 K and critical current densities of ∝600 A/cm 2 at 77 K were produced by oxidation and annealling of metallic precursor alloys. The stabilities and degradation behavior of BSCCO/Ag specimens in various environments were studied by a combination of mass loss measurement, electrical transport measurement and microstructural observation. The environmental conditions used in the present work were moist air, distilled water, aqueous solutions of NaCl, NaOH and acetic acid, and organic solvents methanol and acetone. Although there is a general tendency toward a decrease in critical current density after a long exposure to most of the testing conditions, the specimens containing a high percent of Ag (≥70 wt.%) showed very little decrease in Tc and J c up to 200 days of exposure in moist air and distilled water, and up to 20 days in NaCl solution, methanol and acetone. It was found that the superconducting ''2223'' phase is stable in water, neutral solutions and the organic solvents, reacts very slowly with basic solutions, and dissolves rapidly in acidic solutions. Some non-superconducting Ca-rich oxides dissolve in water and neutral and basic solutions and therefore damage the connection of the superconducting grains in low-Ag containing specimens. The excellent stability of the BSCCO/Ag superconducting microcomposites containing high Ag provides an important advantage for their potential industrial application. (orig.)

  17. Response of high Tc superconducting Josephson junction to nuclear radiation

    International Nuclear Information System (INIS)

    Ding Honglin; Zhang Wanchang; Zhang Xiufeng

    1992-10-01

    The development of nuclear radiation detectors and research on high T c superconducting nuclear radiation detectors are introduced. The emphases are the principle of using thin-film and thick-film Josephson junctions (bridge junction) based on high T c YBCO superconductors to detect nuclear radiation, the fabrication of thin film and thick-film Josephson junction, and response of junction to low energy gamma-rays of 59.5 keV emitted from 241 Am and beta-rays of 546 keV. The results show that a detector for measuring nuclear radiation spectrum made of high T c superconducting thin-film or thick-film, especially, thick-film Josephson junction, certainly can be developed

  18. Pulsed laser deposition of high Tc superconducting thin films

    International Nuclear Information System (INIS)

    Singh, R.K.; Narayan, J.

    1990-01-01

    This paper reports on the pulsed laser evaporation (PLE) technique for deposition of thin films characterized by a number of unique properties. Based on the experimental characteristics, a theoretical model is developed which considers the formation and anisotropic three dimensional expansion of the laser generated plasma. This model explains most of the experimental features observed in PLE. We have also employed the PLE technique for in-situ fabrication of YBa 2 Cu 3 O 7 superconducting thin films on different substrates in the temperature range of 500--650 degrees C. At temperatures below 600 degrees C, a biased interposing ring between the substrate and the target was found to significantly improve the superconducting properties. The minimum ion channeling yields were between 3--3.5% for films deposited on (100) SrTiO 3 and (100) LaAlO 3 substrates

  19. Theory of high-Tc superconducting cuprates based on experimental evidence

    International Nuclear Information System (INIS)

    Abrikosov, A. A.

    1999-01-01

    A model of superconductivity in layered high-temperature superconducting cuprates is proposed, based on the extended saddle point singularities in the electron spectrum, weak screening of the Coulomb interaction and phonon-mediated interaction between electrons plus a small short-range repulsion of Hund's, or spin-fluctuation, origin. This permits to explain the large values of Tc, features of the isotope effect on oxygen and copper, the existence of two types of the order parameter, the peak in the inelastic neutron scattering, the positive curvature of the upper critical field, as function of temperature etc

  20. Superconductive properties, interaction mechanisms, materials preparation and electronic transport in high-Tc superconductors

    International Nuclear Information System (INIS)

    Saemann-Ischenko, G.

    1993-01-01

    The final report is composed of eight chapters dealing with the following aspects: I. Mixed state, critical currents, anisotropy, intrinsic and extrinsic pinning. II. Microwave properties and far-infrared reflectivity of epitactic HTSC films. III. Hall effect at the states of normal conductivity and superconductivity, magnetoresistance, superconducting fluctuation phenomena. IV. Effects of the nuclear and the electronic energy loss. V. Scanning electron microscopy. VI. p- and n-doped high-Tc superconductors: Charge symmetry and magnetism. VII. Preparation methods. VIII. Electrochemical examinations of HTSC films and HTSC monocrystals at low temperatures. (orig./MM) [de

  1. High Tc superconducting three-terminal device under quasi-particle injection

    International Nuclear Information System (INIS)

    Hashimoto, K.; Kabasawa, U.; Tonouchi, M.; Kobayashi, T.

    1988-01-01

    A new type of the current injection type three terminal device was fabricated using the high Tc YBaCuO thin epitaxial films, wherein the hot quasi-particle injection effect on the superconducting current was closely examined. The zero bias drain current was efficiently suppressed by the injection of the hot quasi-particles through the gate electrode. Though it is speculative, a comparison of the experimental results and analyses based on the familiar BCS theory intimates that the main mechanism of the current modulation is the non-equilibrium superconductivity due to accumulation of the excess quasi-particles

  2. Dependence of the quasiparticle recombination rate on the superconducting gap and TC

    Science.gov (United States)

    Carr, G. L.; Xi, Xiaoxiang; Hwang, J.; Tashiro, H.; Reitze, D. H.; Tanner, D. B.

    2010-03-01

    The relaxation of excess quasiparticles in a BCS superconductor is known to depend on quantities such as the quasiparticle & phonon density of states, and their coupling (Kaplan et al, Phys. Rev. B 14 4854, 1976). Disorder or an applied field can disrupt superconductivity, as evidenced by a reduced TC. We consider some simple modifications to the quasiparticle density of states consistent with a suppressed energy gap and TC, leading to changes in the intrinsic and effective (measured) rates for excess quasiparticles to recombine into pairs. We review some results for disordered MoGe and discuss the magnetic-field dependence of the recombination process.

  3. Chemical casting of high-Tc superconducting BiSCCO

    International Nuclear Information System (INIS)

    Toth, L.E.; Das, B.N.; Rayne, R.J.; Bender, B.A.; Lechter, W.L.; Hoff, H.A.; Osofsky, M.S.; Soulen, R.J. Jr.

    1989-01-01

    BiSCCO has been successfully cast into a number of useful shapes. This casting process differs significantly from traditional casting in that the process includes a change in the oxygen content of the melt. A heat treatment is required to restore the original chemistry, properly form the BiSCCO crystal structure and develop the superconducting properties. This paper emphasizes the microstructures of as-cast and heat treated BiSCCO. Casting causes considerable grain alignment of the BiSCCO platelets. The platelets align preferentially along the thermal gradients which exist during the solidification process

  4. Spin-polarons and high-Tc superconductivity

    International Nuclear Information System (INIS)

    Wood, R.F.

    1994-03-01

    The spin-polaron concept is introduced in analogy to ionic and electronic polarons and the assumptions underlying the author's approach to spin-polaron mediated high-T c superconductivity are discussed. Elementary considerations about the spin-polaron formation energy are reviewed and the possible origin of the pairing mechanism illustrated schematically. The electronic structure of the CuO 2 planes is treated from the standpoint of antiferromagnetic band calculations that lead directly to the picture of holes predominantly on the oxygen sublattice in a Mott-Hubbard/charge transfer insulator. Assuming the holes to be described in a Bloch representation but with the effective mass renormalized by spin-polaron formation, equations for the superconducting gap, Δ, and transition temperature, T c , are developed and the symmetry of Δ discussed. After further simplifications, T c is calculated as a function of the carrier concentration, x. It is shown that the calculated behavior of T c (x) follows the experimental results closely and leads to a natural explanation of the effects of under- and over-doping. The paper concludes with a few remarks about the evidence for the carriers being fermions (polarons) or bosons (bipolarons)

  5. Superconductivity of high Tc Scientific revolution?; Superconductividad de alta Tc una revolucion cientifica?

    Energy Technology Data Exchange (ETDEWEB)

    Marquina, J E; Ridaura, R; Gomez, R; Marquina, V; Alvarez, J L

    1998-12-31

    A short history of superconductivity, since its discovery by Bednorz and Muller to the development of new materials with high transition temperatures, is presented. Further evolvements are analyzed in terms of T.s. Kuhn conceptions expressed in his book. The Structure of Scientific Revolutions. (Author) 4 refs.

  6. High-Tc superconducting antenna-coupled microbolometer on silicon

    Science.gov (United States)

    Rice, Joseph P.; Grossman, Erich N.; Borcherdt, L. J.; Rudman, D. A.

    1994-05-01

    A process is described for fabricating antenna-coupled resistive-edge microbolometers based on the high-Tc superconductor YBa2Cu3O7 (YBCO) on silicon. The YBCO and a buffer layer of yttria-stabilized zirconia (YSZ) were grown epitaxially on silicon to minimize excess electrical noise. A silicon-micromachined YBCO/YSZ air-bridge was incorporated to minimize the thermal conductance and the heat capacity. The thermal conductance of the air-bridge was measured to be 3 X 10-6 W/K at a temperature of 100 K. At an operating temperature of 89 K, the detector is estimated to have a response time of 2 microsecond(s) , a responsivity of the 1000 V/W range, and a noise-equivalent power in the 10-12 W/Hz1/2 range at 1000 Hz.

  7. High-{Tc} superconducting antenna-coupled microbolometer on silicon

    Energy Technology Data Exchange (ETDEWEB)

    Rice, J.P.; Grossman, E.N.; Borcherdt, L.J.; Rudman, D.A. [National Inst. of Standards and Technology, Boulder, CO (United States). Cryoelectronic Metrology Group

    1994-12-31

    A process is described for fabricating antenna-coupled resistive-edge microbolometers based on the high-{Tc} superconductor YBa{sub 2}Cu{sub 3}O{sub 7} (YBCO) on silicon. The YBCO and a buffer layer of yttria-stabilized zirconia (YSZ) were grown epitaxially on silicon to minimize excess electrical noise. A silicon-micromachined YBCO/YSZ air-bridge was incorporated to minimize the thermal conductance and the heat capacity. The thermal conductance of the air-bridge was measured to be 3 {times} 10{sup {minus}6} W/K at a temperature of 100 K. At an operating temperature of 89 K, the detector is estimated to have a response time of 2 {micro}s, a responsivity in the 1,000 V/W range, and a noise-equivalent power (NEP) in the 10{sup {minus}12} W/Hz{sup 1/2} range at 1,000 Hz.

  8. A phenomenological approach to high Tc oxide superconductors

    International Nuclear Information System (INIS)

    Chela-Flores, J.; Das, M.P.; Saif, A.G.

    1987-06-01

    Oxide superconductors are described in terms of macroscopic wave functions Ψ and Φ corresponding, respectively, to electron pairs of the superconducting and insulating states. In terms of the total free energy of the system, including the effect of interaction, we discuss the electrodynamic responses of the oxide superconductors in relation with the experiments to data. (author). 10 refs

  9. Finding new superconductors: the spin-fluctuation gateway to high Tc and possible room temperature superconductivity.

    Science.gov (United States)

    Pines, David

    2013-10-24

    We propose an experiment-based strategy for finding new high transition temperature superconductors that is based on the well-established spin fluctuation magnetic gateway to superconductivity in which the attractive quasiparticle interaction needed for superconductivity comes from their coupling to dynamical spin fluctuations originating in the proximity of the material to an antiferromagnetic state. We show how lessons learned by combining the results of almost three decades of intensive experimental and theoretical study of the cuprates with those found in the decade-long study of a strikingly similar family of unconventional heavy electron superconductors, the 115 materials, can prove helpful in carrying out that search. We conclude that, since Tc in these materials scales approximately with the strength of the interaction, J, between the nearest neighbor local moments in their parent antiferromagnetic state, there may not be a magnetic ceiling that would prevent one from discovering a room temperature superconductor.

  10. Superconductivity

    CERN Document Server

    Ketterson, John B

    2008-01-01

    Conceived as the definitive reference in a classic and important field of modern physics, this extensive and comprehensive handbook systematically reviews the basic physics, theory and recent advances in the field of superconductivity. Leading researchers, including Nobel laureates, describe the state-of-the-art in conventional and unconventional superconductors at a particularly opportune time, as new experimental techniques and field-theoretical methods have emerged. In addition to full-coverage of novel materials and underlying mechanisms, the handbook reflects continued intense research into electron-phone based superconductivity. Considerable attention is devoted to high-Tc superconductivity, novel superconductivity, including triplet pairing in the ruthenates, novel superconductors, such as heavy-Fermion metals and organic materials, and also granular superconductors. What’s more, several contributions address superconductors with impurities and nanostructured superconductors. Important new results on...

  11. Strong correlations and the search for high-Tc superconductivity in chromium pnictides and chalcogenides

    Science.gov (United States)

    Pizarro, J. M.; Calderón, M. J.; Liu, J.; Muñoz, M. C.; Bascones, E.

    2017-02-01

    Undoped iron superconductors accommodate n =6 electrons in five d orbitals. Experimental and theoretical evidence shows that the strength of correlations increases with hole doping, as the electronic filling approaches half filling with n =5 electrons. This evidence delineates a scenario in which the parent compound of iron superconductors is the half-filled system, in analogy to cuprate superconductors. In cuprates the superconductivity can be induced upon electron or hole doping. In this work we propose to search for high-Tc superconductivity and strong correlations in chromium pnictides and chalcogenides with n slave-spin and multiorbital random-phase-approximation calculations we analyze the strength of the correlations and the superconducting and magnetic instabilities in these systems with the main focus on LaCrAsO. We find that electron-doped LaCrAsO is a strongly correlated system with competing magnetic interactions, with (π ,π ) antiferromagnetism and nodal d -wave pairing being the most plausible magnetic and superconducting instabilities, respectively.

  12. Systematics in positron annihilation lifetime analysis of high Tc superconducting transitions

    International Nuclear Information System (INIS)

    Howell, R.H.; Radousky, H.B.; Wachs, A.L.; Fluss, M.J.; Turchi, P.E.A.; Jean, Y.C.; Sunder, C.S.; Chu, C.W.; Peng, J.L.; Folkerts, T.J.; Shelton, R.N.; Hinks, D.G.

    1989-01-01

    Values of the positron lifetime have previously been observed to change with temperature below T c in high T c superconducting oxides. The authors report new measurements on Ba .6 K .4 Bio 3 and Nd 1.85 Ce .15 CuO 4

  13. A study on the development of high Tc superconducting materials and on the effects of neutron irradiation

    International Nuclear Information System (INIS)

    Won, Dong Yeon; Chang, In Soon; Lee, Jong Min

    1990-08-01

    An Ag-sheathed (Pb,Bi)SrCaCuO superconducting tape was prepared by the cold rolling and post heat treatment method. The tape shows a c-oriented texture perpendicular to the rolling direction. The aligned grain structure may be resulted from the anisotropic grain growth of the high Tc superconducting phase. The bulk (Pb,Bi)SrCaCuO samples with (a) Tc=10lK and (b) 96K were prepared by the solid state reaction method and were neutron-irradiated up to 1.5 x 10 1 8 n/cm 2 . After irradiation the zero resistance temperature(Tc) of (a) was decreased to 96K but (b) did not show any change in Tc. The critical current density of (a) also decreased from 0.75A/cm 2 but (b) was constant as 1.5 A/cm 2 after irradiation. (Author)

  14. Internal resonance of an elastic body levitated above high-Tc superconducting bulks

    International Nuclear Information System (INIS)

    Kokuzawa, T; Toshihiko, S; Yoshizawa, M

    2010-01-01

    In high-Tc superconducting magnetic levitation systems, levitated bodies can keep stable levitation with no contact and no control and thus their damping is very small. Thanks to these features, their applications to various apparatus are expected. However, on account of their small damping, the nonlinearity of electromagnetic levitation force can give notable effects upon motion of the levitated bodies. Therefore this nonlinearity must be taken into account to accurately analyze the dynamical behavior of the levitated bodies. Structures of such a levitated body can show elastic deformation if the large electromagnetic force acts on it. Therefore, we need to deal with the model as an elastic body. As mentioned above, nonlinear characteristics easily appear in this elastic vibration on account of the small damping. Especially when the ratio of the natural frequencies of the eigenmodes is integer, internal resonance can occur. This nonlinear resonance is derived from nonlinear interactions among the eigenmodes of the elastic levitated body. This kind of internal resonance of an elastic body appearing in high-Tc superconducting levitation systems has not been studied so far. This research especially deals with internal resonance of a beam supported at both its ends by electromagnetic forces acting on permanent magnets. The governing equation with the nonlinear boundary conditions for the dynamics of a levitated beam has been derived. Numerical results show internal resonance of the 1st mode and the 3rd mode. Experimental results are qualitatively in good agreement with numerical ones.

  15. Prediction of high-Tc conventional superconductivity in the ternary lithium borohydride system

    Science.gov (United States)

    Kokail, Christian; von der Linden, Wolfgang; Boeri, Lilia

    2017-12-01

    We investigate the superconducting ternary lithium borohydride phase diagram at pressures of 0 and 200 GPa using methods for evolutionary crystal structure prediction and linear-response calculations for the electron-phonon coupling. Our calculations show that the ground state phase at ambient pressure, LiBH4, stays in the P n m a space group and remains a wide band-gap insulator at all pressures investigated. Other phases along the 1 :1 :x Li:B:H line are also insulating. However, a full search of the ternary phase diagram at 200 GPa revealed a metallic Li2BH6 phase, which is thermodynamically stable down to 100 GPa. This superhydride phase, crystallizing in a F m 3 ¯m space group, is characterized by sixfold hydrogen-coordinated boron atoms occupying the fcc sites of the unit cell. Due to strong hydrogen-boron bonding this phase displays a critical temperature of ˜100 K between 100 and 200 GPa. Our investigations confirm that ternary compounds used in hydrogen-storage applications should exhibit high-Tc conventional superconductivity in diamond anvil cell experiments, and suggest a viable route to optimize the superconducting behavior of high-pressure hydrides, exploiting metallic covalent bonds.

  16. High-temperature superconductivity

    International Nuclear Information System (INIS)

    Lynn, J.W.

    1990-01-01

    This book discusses development in oxide materials with high superconducting transition temperature. Systems with Tc well above liquid nitrogen temperature are already a reality and higher Tc's are anticipated. The author discusses how the idea of a room-temperature superconductor appears to be a distinctly possible outcome of materials research

  17. Analysis of the superconductivity in perovskite oxides using three ...

    Indian Academy of Sciences (India)

    2Institute of Theoretical Physics, University of Erlangen-Nürnberg, D-91058 Erlangen, Germany ... taining oxide superconductor with the transition temperature (Tc ≈ 30 K, for x = 0.4 ... high-frequency (energy) optical phonons, as the answer.

  18. High-Tc Superconducting Bolometer Noise Measurement Using Low Noise Transformers - Theory and Optimization

    Science.gov (United States)

    Aslam, Shahid; Jones, Hollis H.

    2011-01-01

    Care must always be taken when performing noise measurements on high-Tc superconducting materials to ensure that the results are not from the measurement system itself. One situation likely to occur is with low noise transformers. One of the least understood devices, it provides voltage gain for low impedance inputs (< 100 ), e.g., YBaCuO and GdBaCuO thin films, with comparatively lower noise levels than other devices for instance field effect and bipolar junction transistors. An essential point made in this paper is that because of the complex relationships between the transformer ports, input impedance variance alters the transformer s transfer function in particular, the low frequency cutoff shift. The transfer of external and intrinsic transformer noise to the output along with optimization and precautions are treated; all the while, we will cohesively connect the transfer function shift, the load impedance, and the actual noise at the transformer output.

  19. High Tc superconducting magnetic multivibrators for fluxgate magnetic-field sensors

    International Nuclear Information System (INIS)

    Mohri, K.; Uchiyama, T.; Ozeki, A.

    1989-01-01

    Sensitive and quick-response nonlinear inductance characteristics are found for high Tc superconducting (YBa 2 Cu 3 O 7-chi ) disk cores at 77K in which soft magnetic BH hysteresis loops are observed. Various quick response magnetic devices such as modulators, amplifiers and sensors are built using these cores. The magnetizing frequency can be set to more than 20 MHz, which is difficult for conventional ferromagnetic bulk materials such as Permalloy amorphous alloys and ferrite. New quick-response fluxgate type magnetic-field sensors are made using ac and dc voltage sources. The former is used for second-harmonic type sensors, while the latter is for voltage-output multivibrator type sensors. Stable and quick-response sensor characteristics were obtained for two-core type multivibrators

  20. Electrical Insulation of 500-m High-Tc Superconducting Power Cable

    International Nuclear Information System (INIS)

    Takahashi, T; Ichikawa, M; Suzuki, H; Okamoto, T; Akita, S; Mukoyama, S; Yagi, M; Maruyama, S; Kimura, A

    2006-01-01

    Electrical insulation is one of the essential technologies for the electric power apparatus. Determination of testing voltages and design method of the electrical insulation layer are inextricably linked each other, and are critical to developing and realizing a cold dielectric (CD) type high-Tc superconducting (HTS) power cable. The authors had proposed the electrical insulation design method with concepts of partial discharge-free designs for ac voltage condition. This paper discusses the testing voltages for a 77 kV 1000 A HTS power cable with a length of 500 m, and describes results of various voltage withstand test. As a result, it is concluded that the proposed electrical insulation design method is appropriate for the HTS power cable

  1. On the electronegativity of the high-Tc oxide superconductor

    International Nuclear Information System (INIS)

    Zhang Liyuan.

    1991-08-01

    We employ a very useful quantity, the electronegativity, to classify the superconductor. The value of the group average electronegativity to separate superconductor into two categories is 2. Each category has unique chemical bond features. The high-T c oxide superconductor belongs to the second category with group average electronegativity being larger than 2. Their unusual bond nature also gives new insight into some essential factors beneficial to enhance superconductivity. (author). 9 refs, 2 tabs

  2. New superconductors from granular to high T$_{c}$

    CERN Document Server

    Deutscher, Guy

    2018-01-01

    How new are the high Tc superconductors, as compared to the conventional low Tc ones? In what sense are these oxides different from regular metals in their normal state? How different is the mechanism for high Tc superconductivity from the well-known electron-phonon interaction that explains so well superconductivity in metals and alloys? What are the implications of the new features of the high Tc oxides for their practical applications? This interesting book aims to provide some answers to those questions, drawing particularly on similarities between the high Tc oxides and granular superconductors, which also present a short coherence length, a small superfluid density and an inhomogeneous structure.

  3. New superconductors from granular to high T$_{c}$

    CERN Document Server

    Deutscher, Guy

    2006-01-01

    How new are the high Tc superconductors, as compared to the conventional low Tc ones? In what sense are these oxides different from regular metals in their normal state? How different is the mechanism for high Tc superconductivity from the well-known electron-phonon interaction that explains so well superconductivity in metals and alloys? What are the implications of the new features of the high Tc oxides for their practical applications? This book aims to give some answers to those questions, drawing particularly on similarities between the high Tc oxides and granular superconductors, which also present a maximum of their critical temperature near the metal-insulator transition.

  4. Superconducting properties of the hexagonal-close-packed alloy system TcZr

    International Nuclear Information System (INIS)

    Chatterjee, P.

    1984-01-01

    The theoretical formula of McMillan, modified via the multiple-scattering theory of Gomersall and Gyorffy, is very successful in computing the electron-phonon coupling constant (lambda) and the superconducting transition temperature (T/sub c/) of elements and compounds from quantities readily obtainable from band structure work or approaches based on the scattering theory. However, for disordered solids this theory fails because of the breakdown of the translational symmetry used in the multiple scattering theory. In the particular case of substitutional alloys, the problem can still be solved however if, at each lattice point, the t-matrix of an individual scatterer is replaced by a configurational average of the t-matrices of the alloying materials (average t-matrix approximation). This modified theory, which has already been successfully applied to some cubic substitutional alloys, is herein used to predict lambda and T/sub c/ for the h.c.p. TcZr alloy system. The results indicate that this system has good superconducting properties. (author)

  5. Analysis of High Tc Superconducting Rectangular Microstrip Patches over Ground Planes with Rectangular Apertures in Substrates Containing Anisotropic Materials

    Directory of Open Access Journals (Sweden)

    Abderraouf Messai

    2013-01-01

    Full Text Available A rigorous full-wave analysis of high Tc superconducting rectangular microstrip patch over ground plane with rectangular aperture in the case where the patch is printed on a uniaxially anisotropic substrate material is presented. The dyadic Green’s functions of the considered structure are efficiently determined in the vector Fourier transform domain. The effect of the superconductivity of the patch is taken into account using the concept of the complex resistive boundary condition. The accuracy of the analysis is tested by comparing the computed results with measurements and previously published data for several anisotropic substrate materials. Numerical results showing variation of the resonant frequency and the quality factor of the superconducting antenna with regard to operating temperature are given. Finally, the effects of uniaxial anisotropy in the substrate on the resonant frequencies of different TM modes of the superconducting microstrip antenna with rectangular aperture in the ground plane are presented.

  6. Uniaxial strain orientation dependence of superconducting transition temperature (Tc) and critical superconducting pressure (Pc) in β-(BDA-TTP)2I3.

    Science.gov (United States)

    Kikuchi, Koichi; Isono, Takayuki; Kojima, Masayuki; Yoshimoto, Haruo; Kodama, Takeshi; Fujita, Wataru; Yokogawa, Keiichi; Yoshino, Harukazu; Murata, Keizo; Kaihatsu, Takayuki; Akutsu, Hiroki; Yamada, Jun-ichi

    2011-12-14

    Dependence of the superconducting transition temperature (T(c)) and critial superconducting pressure (P(c)) of the pressure-induced superconductor β-(BDA-TTP)(2)I(3) [BDA-TTP = 2,5-bis(1,3-dithian-2-ylidene)-1,3,4,6-tetrathiapentalene] on the orientation of uniaxial strain has been investigated. On the basis of the overlap between the upper and lower bands in the energy dispersion curve, the pressure orientation is thought to change the half-filled band to the quarter-filled one. The observed variations in T(c) and P(c) are explained by considering the degree of application of the pressure and the degree of contribution of the effective electronic correlation at uniaxial strains with different orientations parallel to the conducting donor layer. © 2011 American Chemical Society

  7. Determination of copper oxidizing power in superconducting yttrium ceramics

    International Nuclear Information System (INIS)

    Pontaler, R.P.; Lebed', N.B.

    1989-01-01

    A new photometric method for determining the formal copper degree of oxidation and oxygen deficiency in superconducting high-temperature oxides containing yttrium, barium and copper is developed. The method is based on oxidation of Co(2) complex with EDTA by Cu(3) ions in acetrate buffer solution with pH 4.2-4.7 and allows one to determine 1-10% of Cu(3). Relative standard deviation when determining Cu(3) makes up 0.03-0.05. Using a qualitative reaction with the application of sodium vanadate hydrochloride solution the absence of peroxide compound in superconducting yttrium ceramics is ascertained

  8. Superconducting oxide thin films by ion beam sputtering

    International Nuclear Information System (INIS)

    Kobrin, P.H.; DeNatale, J.F.; Housley, R.M.; Flintoff, J.F.; Harker, A.B.

    1987-01-01

    Superconducting thin films of ternary copper oxides from the Y-Ba-Cu-O and La-Sr-Cu-O systems have been deposited by ion beam sputtering of ceramic targets. Crystallographic orientation of the polycrystalline films has been shown to vary with substrate identity, deposition temperature and annealing temperature. The onset of the superconductive transition occurs near 90K in the Y-Ba-Cu-O system. Fe impurities of < 0.2% have been found to inhibit the superconducting transition, probably by migrating to the grain boundaries

  9. Analysis of thermodynamic properties for high-temperature superconducting oxides

    International Nuclear Information System (INIS)

    Kushwah, S.S.; Shanker, J.

    1993-01-01

    Analysis of thermodynamic properties such as specific heat, Debye temperature, Einstein temperature, thermal expansion coefficient, bulk modulus, and Grueneisen parameter is performed for rare-earth-based, Tl-based, and Bi-based superconducting copper oxides. Values of thermodynamic parameters are calculated and reported. The relationship between the Debye temperature and the superconducting transition temperature is used to estimate the values of T c using the interaction parameters from Ginzburg. (orig.)

  10. Quantum and superconducting fluctuations effects in disordered Nb 1- xTa x thin films above Tc

    Science.gov (United States)

    Giannouri, M.; Papastaikoudis, C.

    1999-05-01

    Disordered Nb 1- xTa x thin films are prepared with e-gun coevaporation. The influence of the β-phase of tantalum in the critical temperature Tc is observed as a function of the substrate temperature. The measurements of transverse magnetoresistance at various isothermals are interpreted in terms of weak-localization and superconducting fluctuations. From the fitting procedure, the phase breaking rate τφ-1 and the Larkin parameter βL are estimated as a function of temperature. Conclusions about the dominant inelastic scattering mechanisms at various temperature regions as well as for the dominant mechanism of superconducting fluctuations near the transition temperature are extracted.

  11. Microwave effective surface impedance of structures including a high-Tc superconducting film

    International Nuclear Information System (INIS)

    Hartemann, P.

    1992-01-01

    The microwave effective surface impedances of different stacks made of high-temperature superconducting films, dielectric materials and bulk normal metals were computed. The calculations were based on the two-fluid model of superconductors and the conventional transmission line theory. These effective impedances are compared to the calculated intrinsic surface impedances of the stacked superconducting films. The considered superconducting material has been the oxide YBa 2 Cu 3 O 7 epitaxially grown on crystalline substrates (MgO, LaAlO 3 , SrTiO 3 ), the film thickness ranging from a few nm to 1μm. Discrepancies between the effective surface resistances or reactances and the corresponding intrinsic values were determined at 10 GHz for non resonant or resonant structures. At resonance the surface resistance discrepancy exhibits a sharp peak which reaches 10 4 or more in relative value according to the geometry and the used materials. Obviously the effective surface reactance shows also huge variations about the resonance and may be negative. Moreover geometries allowing to obtain an effective resistance smaller than the film intrinsic value have been found. The effects of the resonance phenomenon on the electromagnetic wave reflectivity and reflection phase shift are investigated. Therefore the reported theoretical results demonstrate that the effective surface impedance of YBCO films with a thickness smaller than 500 nm can be very different from the intrinsic film impedance according to the structures. (Author). 3 refs., 10 figs., 2 tabs

  12. Quality criteria for high Tc superconductors and on the clarification of the superconducting mechanism

    International Nuclear Information System (INIS)

    Haase, E.L.; Ruzicka, J.

    1992-03-01

    After the successful basic solution of the Nb 3 Ge and Nb 3 Si problems, optimization strategies and quality criteria were developed for high Tc superconducting (HTCS) samples in analogy. After improvements of the sputtering system, the preparation parameters were tightly controlled, leading to samples with a reproducible linear slope of the specific resistance ρ(T). Further improvements by us and Poppe et al. lead to the preparation of 123 films with non-linear ρ(T) curves above 120K. A generalization to a T 2 behavior of ρ(T) leads to the further generalization that defect free HTCS are essentially two dimensional in nature, with all ensuing consequences. The momentum transport of the moving charge cariers requires, because of momentum conservation, a mechanism to transfer momentum to the lattice (momentum relaxation). The qualitative theory developed for two dimensional (2D) systems shows that the electron-phonon interaction is strongly suppressed and hence that the weaker electron-electron interaction dominates. That theory makes numerous predictions, which so far are confirmed by experiments. In particular, it accounts for the extreme temperature dependence of the mean free path and the Hall effect. It is inferred that the mechanism of HTCS is predominantly due to electron-electron interaction - probably of bipolaron nature, as indicated by experiment. At this point experiment meets just a few theories, that conform with the experimental facts and above theory, all based on the quasi-particle theory of electron-electron interaction. The theory of Newns, Pattnaik and Tsuei should have a T 2 shape of ρ(T) and, because E F lies near a nearly logarithmic van Hove singularity, accounts for the high Tc. Ruvalds and Virosztek's theory predicts the T 2 shape of ρ(T). (orig./GSCH)

  13. A novel propulsion method for high-Tc superconducting maglev vehicle

    International Nuclear Information System (INIS)

    Ma Guangtong; Wang Jiasu; Wang Suyu; Liu Minxian; Jing Hua; Lu Yiyun; Lin Qunxu

    2008-01-01

    High-Tc superconducting (HTS) maglev is considered as a perfect transportation type because of its unique inherent stability. A direct current (DC) linear motor using the permanent magnet guideway (PMG) as the stator and the on-board coil as the rotor instead of the present inductive or synchronous alternate current (AC) linear motor which has an economic disadvantage due to the necessity to lay primary coil along the guideway is proposed in this paper. In order to modulate the magnetic field under the PMG, an inverse E shape ferromagnetic device (IESFD) core is designed. The possible winding method for the on-board coil is listed, and the analytical result shows that a considerable net ampere force and thus the propulsion force can be generated by this special structure. The influence of the concentrated effect of the IESFD on the maglev performance of HTS bulk is studied by a numerical program, and the results show that the levitation force with the IESFD is 90% of that without. It is also indicated that the load capability and lateral performance of the maglev vehicle combined this propulsion method can be improved thanks to the attractive effect between the IESFD and PMG. The cost of the HTS maglev vehicle will be remarkably reduced and then shorten the distance to practical application with this propulsion method

  14. Spectroscopy of metal "superatom" nanoclusters and high-Tc superconducting pairing

    Science.gov (United States)

    Halder, Avik; Kresin, Vitaly V.

    2015-12-01

    A unique property of metal nanoclusters is the "superatom" shell structure of their delocalized electrons. The electronic shell levels are highly degenerate and therefore represent sharp peaks in the density of states. This can enable exceptionally strong electron pairing in certain clusters composed of tens to hundreds of atoms. In a finite system, such as a free nanocluster or a nucleus, pairing is observed most clearly via its effect on the energy spectrum of the constituent fermions. Accordingly, we performed a photoionization spectroscopy study of size-resolved aluminum nanoclusters and observed a rapid rise in the near-threshold density of states of several clusters (A l37 ,44 ,66 ,68 ) with decreasing temperature. The characteristics of this behavior are consistent with compression of the density of states by a pairing transition into a high-temperature superconducting state with Tc≳100 K. This value exceeds that of bulk aluminum by two orders of magnitude. These results highlight the potential of novel pairing effects in size-quantized systems and the possibility to attain even higher critical temperatures by optimizing the particles' size and composition. As a new class of high-temperature superconductors, such metal nanocluster particles are promising building blocks for high-Tc materials, devices, and networks.

  15. Y-Ba-Cu-O superconducting film on oxidized silicon

    International Nuclear Information System (INIS)

    Gupta, R.P.; Khokle, W.S.; Dubey, R.C.; Singhal, S.; Nagpal, K.C.; Rao, G.S.T.; Jain, J.D.

    1988-01-01

    We report thick superconducting films of Y-Ba-Cu-O on oxidized silicon substrates. The critical temperatures for onset and zero resistance are 96 and 77 K, respectively. X-ray diffraction analysis predicts 1, 2, 3 composition and orthorhombic phase of the film

  16. Superstrate loading effects on the resonant characteristics of high Tc superconducting circular patch printed on anisotropic materials

    Science.gov (United States)

    Bedra, Sami; Bedra, Randa; Benkouda, Siham; Fortaki, Tarek

    2017-12-01

    In this paper, the effects of both anisotropies in the substrate and superstrate loading on the resonant frequency and bandwidth of high-Tc superconducting circular microstrip patch in a substrate-superstrate configuration are investigated. A rigorous analysis is performed using a dyadic Galerkin's method in the vector Hankel transform domain. Galerkin's procedure is employed in the spectral domain where the TM and TE modes of the cylindrical cavity with magnetic side walls are used in the expansion of the disk current. The effect of the superconductivity of the patch is taken into account using the concept of the complex resistive boundary condition. London's equations and the two-fluid model of Gorter and Casimir are used in the calculation of the complex surface impedance of the superconducting circular disc. The accuracy of the analysis is tested by comparing the computed results with previously published data for several anisotropic substrate-superstrate materials. Good agreement is found among all sets of results. The numerical results obtained show that important errors can be made in the computation of the resonant frequencies and bandwidths of the superconducting resonators when substrate dielectric anisotropy, and/or superstrate anisotropy are ignored. Other theoretical results obtained show that the superconducting circular microstrip patch on anisotropic substrate-superstrate with properly selected permittivity values along the optical and the non-optical axes combined with optimally chosen structural parameters is more advantageous than the one on isotropic substrate-superstrate by exhibiting wider bandwidth characteristic.

  17. Relations between structural and superconducting properties of bulk and thin film high-Tc materials

    International Nuclear Information System (INIS)

    Hessel Andersen, N.

    1994-06-01

    The structural ordering of oxygen deficient and Co-doped YBCO (YBa 2 Cu 3-y Co y O 6+x ) have been studied experimentally, and by computer simulations of the oxygen ordering in the basal plane of the structure. The calculations are based on the two-dimensional ASYNNNI model and its modifications. Good agreement is established between the ASYNNNI calculations and the experimentally observed structural properties of the double cell ortho-II structure and the oxygen disordering process from Co-doping into the basal plane. A model that relates the superconducting transition temperature T c (x) of undoped YBCO and T c (y) of Co-doped YBCO to the formation of specific domains of the two orthorhombic ordered oxygen phases, ortho-I and ortho-II, shows a close agreement with experimental T c (x) and T c (y) data of samples prepared under equilibrium conditions. The structural changes as a result of metal ion substitutions and oxidation/reduction processes have been studied by neutron powder diffraction in Pb 2 Sr 2 Ln 1-x Ca x Cu 3 O 8+y (Ln = Y and Ho), Nd 1.85 Ce 0.15 CuO 4+y , and chemically oxidized La 2-x Sr x CuO 4+y 2 Cu 3-y Al y O 6+x (y 2 Cu 3 O 6+x and Bi 2 Sr 2 CaCu 2 O 8+x thin films deposited on SrTiO 3 (001), MgO (001), LaAlO 3 (001), and NdGaO 3 (001) substrates has been studied by x-ray diffraction, TEM and RBS, and the structural ordering has been analysed in relation to their superconducting properties. (au) (30 ills., 29 refs.)

  18. Conductive polymer/high-TC superconductor sandwich structures: An example of a molecular switch for controlling superconductivity

    International Nuclear Information System (INIS)

    McDevitt, J.T.; Haupt, S.G.; Lo, R.K.

    1994-01-01

    The preparation of a hybrid conducting polymer/high-temperature superconductor device consisting of a polypyrrole coated YBa 2 Cu 3 O 7-x microbridge is reported. Electrochemical techniques are exploited to alter the oxidation state of the polymer and, in doing so, it is found for the first time that superconductivity can be modulated in a controllable and reproducible fashion by a polymer layer. Whereas the neutral (insulating) polypyrrole only slightly influences the electrical properties of the underlying YBa 2 Cu 3 O 7- film, the oxidized (conductive) polymer depresses T c by up to 50K. In a similar fashion, the oxidation state of the polymer is found to modulate reversibly the magnitude of J c , the superconducting critical current. Thus, a new type of molecular switch for controlling superconductivity is demonstrated. Electrochemical, resistance vs. temperature, atomic force microscopy and scanning electron microscopy measurements are utilized to explore the polymer/superconductor interactions

  19. A study on the development of high-Tc superconducting wire

    International Nuclear Information System (INIS)

    Won, Dong Yeon; Chang, In Soon; Lee, Jong Min; Um, Tae Yoon; Hong, Kyae Won; Lee, Ho Jin; Lee, Hee Kwun; Kim, Chan Joong; Park, Soon Dong; Kim, Woo Gon; Kim, Ki Baek; Kwon, Sun Chil

    1992-10-01

    On this study Y-Ba-Cu-O was prepared by partial melt process and superconducting wire was fabricated by powder-in-tube method. First, mechancial properties, electrical properties, microstructure and oxygen diffusion behavior were observed. Second, through fabricated superconducting wire, conceptual design, composition and plasticity of filament superconducting wire were investigated. (Author)

  20. Structural phase transitions and superconductivity in lanthanum copper oxides

    International Nuclear Information System (INIS)

    Crawford, M.K.; Harlow, R.L.; McCarron, E.M.

    1996-01-01

    Despite the enormous effort expended over the past ten years to determine the mechanism underlying high temperature superconductivity in cuprates there is still no consensus on the physical origin of this fascinating phenomenon. This is a consequence of a number of factors, among which are the intrinsic difficulties in understanding the strong electron correlations in the copper oxides, determining the roles played by antiferromagnetic interactions and low dimensionality, analyzing the complex phonon dispersion relationships, and characterizing the phase diagrams which are functions of the physical parameters of temperature and pressure, as well as the chemical parameters of stoichiometry and hole concentration. In addition to all of these intrinsic difficulties, extrinsic materials issues such as sample quality and homogeneity present additional complications. Within the field of high temperature superconductivity there exists a subfield centered around the material originally reported to exhibit high temperature superconductivity by Bednorz and Mueller, Ba doped La 2 CuO 4 . This is structurally the simplest cuprate superconductor. The authors report on studies of phase differences observed between such base superconductors doped with Ba or Sr. What these studies have revealed is a fascinating interplay of structural, magnetic and superconducting properties which is unique in the field of high temperature superconductivity and is summarized in this paper

  1. An effective 2-band eg model of sulfur hydride H3S for high-Tc superconductivity

    Science.gov (United States)

    Nishiguchi, Kazutaka; Teranishi, Shingo; Miyao, Satoaki; Matsushita, Goh; Kusakabe, Koichi

    To understand high transition temperature (Tc) superconductivity in sulfur hydride H3S, we propose an effective 2-band model having the eg symmetry as the minimal model for H3S. Two eg orbitals centered on a sulfur S atom are chosen for the smallest representation of relevant bands with the van-Hove singularity around the Fermi levels except for the Γ-centered small hole pockets by the sulfur 3 p orbitals. By using the maximally localized Wannier functions, we derive the minimal effective model preserving the body-centered cubic (bcc) crystal symmetry of the H3S phase having the highest Tc ( 203 K under pressures) among the other polymorphs of H3S.

  2. Dependence of the residual surface resistance of superconducting radio frequency cavities on the cooling dynamics around Tc

    Science.gov (United States)

    Romanenko, A.; Grassellino, A.; Melnychuk, O.; Sergatskov, D. A.

    2014-05-01

    We report a strong effect of the cooling dynamics through Tc on the amount of trapped external magnetic flux in superconducting niobium cavities. The effect is similar for fine grain and single crystal niobium and all surface treatments including electropolishing with and without 120 °C baking and nitrogen doping. Direct magnetic field measurements on the cavity walls show that the effect stems from changes in the flux trapping efficiency: slow cooling leads to almost complete flux trapping and higher residual resistance, while fast cooling leads to the much more efficient flux expulsion and lower residual resistance.

  3. Microscopic Superconductivity and Room Temperature Electronics of High-Tc Cuprates

    International Nuclear Information System (INIS)

    Liu Fusui; Chen Wanfang

    2008-01-01

    This paper points out that the Landau criterion for macroscopic superfluidity of He II is only a criterion for microscopic superfluidity of 4 He, extends the Landau criterion to microscopic superconductivity in fermions (electron and hole) system and system with Cooper pairs without long-range phase coherence. This paper gives another three non-superconductive systems that are of microscopic superconductivity. This paper demonstrates that one application of microscopic superconductivity is to establish room temperature electronics of the high-T c cuprates

  4. Fabrication and characterizations of high-Tc superconducting ceramic/polymer 0--3 composites

    International Nuclear Information System (INIS)

    Du, J.; Unsworth, J.

    1994-01-01

    High-T c superconducting ceramic YBa 2 Cu 3 O 7-x /thermosetting plastic 0--3 composites were fabricated. The structure, physical property, magnetic susceptibility, levitation, and mechanical strength of the composites were accessed. The influence of filler content on these properties was also studied. Although the 0--3 composites lack an electrical superconducting path through materials, the intrinsic diamagnetic properties were preserved. The magnetic superconducting transition temperature was not degraded. The values of magnetic susceptibility and levitation force for the composites were basically proportional to the actual volume fraction of superconducting filler. These new composite materials are most suitable for the applications in levitating vehicles and mechanical bearings

  5. Possible universal cause of high-Tc superconductivity in different metals

    International Nuclear Information System (INIS)

    Amusia, M.Ya.; Shaginyan, V.R.

    2002-01-01

    Using the theory of the high temperature superconductivity based on the idea of the fermion condensation quantum phase transition (FCQPT) it is shown that neither the d-wave pairing symmetry, nor the pseudogap phenomenon, nor the presence of the Cu-O 2 planes are of decisive importance for the existence of the high-T c superconductivity. The analysis of recent experimental data on this type of superconductivity in different materials is carried out. It is shown that these facts can be understood within the theory of superconductivity based on the FCQPT. The main features of a room-temperature superconductor are discussed [ru

  6. Methods for forming complex oxidation reaction products including superconducting articles

    International Nuclear Information System (INIS)

    Rapp, R.A.; Urquhart, A.W.; Nagelberg, A.S.; Newkirk, M.S.

    1992-01-01

    This patent describes a method for producing a superconducting complex oxidation reaction product of two or more metals in an oxidized state. It comprises positioning at least one parent metal source comprising one of the metals adjacent to a permeable mass comprising at least one metal-containing compound capable of reaction to form the complex oxidation reaction product in step below, the metal component of the at least one metal-containing compound comprising at least a second of the two or more metals, and orienting the parent metal source and the permeable mass relative to each other so that formation of the complex oxidation reaction product will occur in a direction towards and into the permeable mass; and heating the parent metal source in the presence of an oxidant to a temperature region above its melting point to form a body of molten parent metal to permit infiltration and reaction of the molten parent metal into the permeable mass and with the oxidant and the at least one metal-containing compound to form the complex oxidation reaction product, and progressively drawing the molten parent metal source through the complex oxidation reaction product towards the oxidant and towards and into the adjacent permeable mass so that fresh complex oxidation reaction product continues to form within the permeable mass; and recovering the resulting complex oxidation reaction product

  7. The microscopic twins and their crystal phase in the high Tc Y-Ba-Cu-O and Dy-Ba-Cu-O superconductive ceramics

    International Nuclear Information System (INIS)

    Zu, Z.J.; Chen, Y.L.

    1988-01-01

    Most consider that the structure of Y-Ba- Cu-O and Dy-Ba-Cu-O stable superconductive crystals with high Tc is associated with the right-angled phase. The superconductivity is closely connected with the right-angled character of the crystalline texture; the better the right- angled character, the better the superconductivity. From statistical investigations of examples the authors have discovered that most of the Y-Ba-Cu-O and Dy-Ba-Cu-O superconductivity with high Tc ceramic crystals is in the monoclinic phase, which, consists of microscopic, lamellar, single twins. The long-columnar grains consisting of lamellar twin slabs show the optical characteristics of right-angled phase. The microscopic twinning and grain morphologies are summarized in this paper

  8. Production of superconducting ceramic oxides by coprecipitation

    International Nuclear Information System (INIS)

    Bizaio, L.R.; Lima, M.A.F. de; Figueiredo Jardim, R.de; Pinheiro, E.A.; Galembeck, F.

    1988-01-01

    An alternative method for production of ceramic oxides is described. The method consist in the coprecipitation reaction of metallic ions with oxalic acid. The obtainment samples present additional phases characterized by X-rays and optical microscopy. (C.G.C.) [pt

  9. Superconductivity

    International Nuclear Information System (INIS)

    Taylor, A.W.B.; Noakes, G.R.

    1981-01-01

    This book is an elementray introduction into superconductivity. The topics are the superconducting state, the magnetic properties of superconductors, type I superconductors, type II superconductors and a chapter on the superconductivity theory. (WL)

  10. Determination of the electromagnetic field in a high-Tc linear superconducting resonator

    International Nuclear Information System (INIS)

    Trotel, A.; Sautrot, S.; Pyee, M.

    1994-01-01

    In this paper, the electromagnetic field configuration in a linear SHTC resonator is described. Two areas are considered: 1) the superconducting strip, 2) the dielectric around the strip. The calculation is based on the current density given by Bowers for an infinite superconducting line. The current density in the resonator is defined by these relations and the resonance conditions. (orig.)

  11. Design and Characteristics Analysis of a Rod Type High-Tc Superconducting Fault Current Limiter through Electromagnetic Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Hyun, O.B. [Korea Electric Power Research Institute, Taejeon (Korea); Lee, C.J.; Lee, S.J.; Ko, T.K. [Yonsei University, Seoul (Korea)

    2001-07-01

    The existence of a large air gaps between a High-Tc Superconducting (HTS) tube and an iron core, or between a primary winding and a HTS tube possibly causes magnetic flux leaks, resulting in undesirable voltage drops under normal operation. For this reason optimization of air gaps is essential in designing a high-Tc superconducting fault current limiter (SFCL). In this paper we performed the electromagnetic analysis for the optimization. The inductance L decreases by 20% as the hight of the winding increases from 50 to 200 mm. But, L increases from 5.6 mH to 10.5 mH as the hight of the rod changes from 150 to 400 mm. L is found to be almost constant for the air gap between 5 to 10 mm, but L decreases by 20% as the gap increases from 10 to 20 mm. The computational and experimental results will bo compared. (author). 7 refs., 8 figs., 1 tab.

  12. Trapped magnetic field of a superconducting bulk magnet in high- Tc RE-Ba-Cu-O

    International Nuclear Information System (INIS)

    Fujimoto, Hiroyuki; Yoo, Sang Im; Higuchi, Takamitsu; Nakamura, Yuichi; Kamijo, Hiroki; Nagashima, Ken; Murakami, Masato

    1999-01-01

    Superconducting magnets made of high-T c superconductors are promising for industrial applications. It is well known that REBa 2 Cu 3 O 7-x and LRE (light rare-earth) Ba 2 Cu 3 O 7-x superconductors prepared by melt processes have a high critical current density, J c , at 77 K and high magnetic fields. Therefore, the materials are very prospective for high magnetic field application as a superconducting permanent/bulk magnet with liquid-nitrogen refrigeration. LREBaCuO bulks, compared with REBaCuO bulks, exhibit a larger J c in high magnetic fields and a much improved irreversibility field, H irr , at 77 K. In this study, we discuss the possibility and trapped field properties of a superconducting bulk magnet, as well as the melt processing for bulk superconductors and their characteristic superconducting properties. One of the applications is a superconducting magnet for the future magnetically levitated (Maglev) train

  13. Quantitative determination of high-Tc superconductivity from the lattice polarization, structure effect and approach to 300 K Tc

    International Nuclear Information System (INIS)

    Green, B.A.

    1997-01-01

    The quasiparticle state defined by the low temperature polar mobility is a large, quantized positive energy shift that is identical to the constant pairing energy (pseudogap and 2Λ) in the multi-plane high-T c superconductors, showing the lattice polarization produces the single-particle shift and pairing which then transfer to the superconducting state. The coupling-independence and state transfer follow from the nonlocality and action length of the polarization interaction, and the multiple plane requirement from the location of the polar mode. 2Δ is thereby obtained directly, without scaling, from the strong interaction on the plane. The interaction accordingly produces a dynamic, highly stable state, in contrast to BCS superconductors, and the zero-order state is the quantized energy shift. (orig.)

  14. Spin-polaron theory of high-Tc superconductivity: I, spin polarons and high-Tc pairing

    International Nuclear Information System (INIS)

    Wood, R.F.

    1993-06-01

    The concept of a spin polaron is introduced and contrasted with the more familiar ionic polaron picture. A brief review of aspects of ionic bipolaronic superconductivity is given with particular emphasis on the real-space pairing and true Bose condensation characteristics. The formation energy of spin polarons is then calculated in analogy with ionic polarons. The spin-flip energy of a Cu spin in an antiferromagnetically aligned CuO 2 plane is discussed. It is shown that the introduction of holes into the CuO 2 planes will always lead to the destruction of long-range AF ordering due to the formation of spin polarons. The pairing of two spin polarons can be expected because of the reestablishment of local (short-range) AF ordering; the magnitude of the pairing energy is estimated using a simplified model. The paper closes with a brief discussion of the formal theory of spin polarons

  15. High-Tc superconductivity of Tl-Ba-Ca-Cu-O samples

    International Nuclear Information System (INIS)

    Porjesz, T.; Kirschner, I.; Kovacs, G.

    1988-08-01

    A TlBaCaCuO 4.5+x compound has been investigated from the point of view of superconductivity. Depending on the heat treatment, one part of the sample exhibits superconductivity with an onset of 121 K and zero resistivity of 106 K and the other part of them shows a sharp drop in resistivity at 130 K which hints at an existence of superconducting grains. This picture was confirmed by magnetic and ESR measurements giving possibility for estimation of critical magnetic fields. (author). 5 refs, 6 figs

  16. Superconducting and Structural Transitions in the β-Pyrochlore Oxide KOs2O6 under High Pressure

    Science.gov (United States)

    Ogusu, Hiroki; Takeshita, Nao; Izawa, Koichi; Yamaura, Jun-ichi; Ohishi, Yasuo; Tsutsui, Satoshi; Okamoto, Yoshihiko; Hiroi, Zenji

    2010-11-01

    Rattling-induced superconductivity in the β-pyrochlore oxide KOs2O6 is investigated under high pressure up to 5 GPa. Resistivity measurements in a high-quality single crystal reveal a gradual decrease in the superconducting transition temperature Tc from 9.7 K at 1.0 GPa to 6.5 K at 3.5 GPa, followed by a sudden drop to 3.3 K at 3.6 GPa. Powder X-ray diffraction experiments show a structural transition from cubic to monoclinic or triclinic at a similar pressure. The sudden drop in Tc is ascribed to this structural transition, by which an enhancement in Tc due to a strong electron-rattler interaction present in the low-pressure cubic phase is abrogated as the rattling of the K ion is completely suppressed or weakened in the high-pressure phase of reduced symmetry. In addition, we find two anomalies in the temperature dependence of resistivity in the low-pressure phase, which may be due to subtle changes in rattling vibration.

  17. Understanding the superconductivity in copper oxides

    CERN Document Server

    2019-01-01

    The aim of this book is to clarify the situation by adopting a very different approach from the above electronic/magnetic models, where explicitly local dynamical distortions are considered. These are distinctly different from conventional phonons which are a property of the infinite translational invariant symmetric lattice. The local dynamical distortions are shown to account for bulk properties and provide consistent and quantitative agreement with experimental data together with explicit predictions. Selected published experimental and theoretical papers are presented which support the above arguments, but have been ignored on purpose by the originators of the RVB/t-J bubble. To summarize the scope of this book, comprising nine chapters, it is shown, that the phenomenon of HTS in copper oxides is much better understood than publically claimed by RVB/t-J followers. Using the words of B. Laughlin, the presence of the antiferromagnetism in HTS masks the underlying physics where vibronic bipolarons with spin...

  18. Effect of a pseudogap on Tc and on the superconducting order parameter

    International Nuclear Information System (INIS)

    Rodriguez Nunez, J.J.; Reimer Romero, J.J.; Valera, M.; Schmidt, A.A.

    2007-09-01

    We further develop the pseudogap model proposed by J.L. Tallon and J.W. Loram, Physica C 349, 53-68 (2001). For the pseudogap order parameter we choose a particular form which reproduces the main features of the high temperature superconductor (HTSC) phase diagram which depends on carrier number, n. For fitting the key features of the cuprate oxides we have sensible parameters at our disposal, namely, α, which fixes the density where the pseudogap order parameter is maximum, α' which allows us to display the T c vs n curve and E go which gives us the value of the pseudogap. We have reproduced in a qualitative fashion the main details of the experimental data given in the work of Suryadijaya, T. Sasaqawa, and H. Takagi, Physica C 426-431, 402-406 (2005). Our main results are the following: To have decreased the value of T c with respect to the 'free' case, namely, E go = 0, namely, when the pseudogap order parameter is not present. To have obtained the maximum of T c by choosing α' ≠ 0. To have chosen the minimum value of T c inside the pseudogap region, namely, in the region where the pseudogap parameter is a maximum. To have bounded the region of the superconducting dome by choosing the value of E g. In short, we have proposed a phenomenological form for the pseudogap energy, which depends on carrier number and which reproduces in a qualitative way the results of Suryadijaya, T. Sasaqawa and H. Takagi, Physica C 426-431, 402-406 (2005). Consequently, we conclude that the pseudogap is necessary for HTSC. (author)

  19. 99Tc and Re incorporated into metal oxide polyoxometalates: oxidation state stability elucidated by electrochemistry and theory.

    Science.gov (United States)

    McGregor, Donna; Burton-Pye, Benjamin P; Mbomekalle, Israel M; Aparicio, Pablo A; Romo, Susanna; López, Xavier; Poblet, Josep M; Francesconi, Lynn C

    2012-08-20

    The radioactive element technetium-99 ((99)Tc, half-life = 2.1 × 10(5) years, β(-) of 253 keV), is a major byproduct of (235)U fission in the nuclear fuel cycle. (99)Tc is also found in radioactive waste tanks and in the environment at National Lab sites and fuel reprocessing centers. Separation and storage of the long-lived (99)Tc in an appropriate and stable waste-form is an important issue that needs to be addressed. Considering metal oxide solid-state materials as potential storage matrixes for Tc, we are examining the redox speciation of Tc on the molecular level using polyoxometalates (POMs) as models. In this study we investigate the electrochemistry of Tc complexes of the monovacant Wells-Dawson isomers, α(1)-P(2)W(17)O(61)(10-) (α1) and α(2)-P(2)W(17)O(61)(10-) (α2) to identify features of metal oxide materials that can stabilize the immobile Tc(IV) oxidation state accessed from the synthesized Tc(V)O species and to interrogate other possible oxidation states available to Tc within these materials. The experimental results are consistent with density functional theory (DFT) calculations. Electrochemistry of K(7-n)H(n)[Tc(V)O(α(1)-P(2)W(17)O(61))] (Tc(V)O-α1), K(7-n)H(n)[Tc(V)O(α(2)-P(2)W(17)O(61))] (Tc(V)O-α2) and their rhenium analogues as a function of pH show that the Tc-containing derivatives are always more readily reduced than their Re analogues. Both Tc and Re are reduced more readily in the lacunary α1 site as compared to the α2 site. The DFT calculations elucidate that the highest oxidation state attainable for Re is VII while, under the same electrochemistry conditions, the highest oxidation state for Tc is VI. The M(V)→ M(IV) reduction processes for Tc(V)O-α1 are not pH dependent or only slightly pH dependent suggesting that protonation does not accompany reduction of this species unlike the M(V)O-α2 (M = (99)Tc, Re) and Re(V)O-α1 where M(V/IV) reduction process must occur hand in hand with protonation of the terminal M═O to

  20. Approaches to the high Tc superconductivity in β-(BEDT-TTF)2X structure

    International Nuclear Information System (INIS)

    Tokumoto, M.; Anzai, H.; Murata, K.; Bando, H.; Kajimura, K.; Morita, S.; Ishiguro, T.; Saito, G.

    1987-01-01

    Experimental strategies to realize a high T c superconductivity comparable with the high-T c state of β-(BEDT-TTF) 2 I 3 by means of modification of the β-(BEDT-TTF) 2 X structure are discussed. Some experimental results related to such trials are presented, including the effect of anion alloying and the effect of solvent used for crystal growth on the superconductivity in β-(BEDT-TTF) 2 I 3 . (orig.)

  1. Oxidative dissolution potential of biogenic and abiogenic TcO2 in subsurface sediments

    International Nuclear Information System (INIS)

    Fredrickson, J.K.; Zachara, J.M.; Plymale, A.E.; Heald, S.M.; McKinley, J.P.; Kennedy, D.W.; Liu, C.; Nachimuthu, P.

    2009-01-01

    Technetium-99 (Tc) is an important fission product contaminant associated with sites of nuclear fuels reprocessing and geologic nuclear waste disposal. Tc is highly mobile in its most oxidized state (Tc(VII)O 4 - ) and less mobile in the reduced form (Tc(IV)O 2 · nH 2 O). Here we investigate the potential for oxidation of Tc(IV) that was heterogeneously reduced by reaction with biogenic Fe(II) in two sediments differing in mineralogy and aggregation state; unconsolidated Pliocene-age fluvial sediment from the upper Ringold (RG) Formation at the Hanford Site and a clay-rich saprolite from the Field Research Center (FRC) background site on the Oak Ridge Site. Both sediments contained Fe(III) and Mn(III/IV) as redox active phases, but FRC also contained mass-dominant Fe-phyllosilicates of different types. Shewanella putrefaciens CN32 reduced Mn(III/IV) oxides and generated Fe(II) that was reactive with Tc(VII) in heat-killed, bioreduced sediment. After bioreduction and heat-killing, biogenic Fe(II) in the FRC exceeded that in RG by a factor of two. More rapid reduction rates were observed in the RG that had lower biogenic Fe(II), and less particle aggregation. EXAFS measurements indicated that the primary reduction product was a TcO 2 -like phase in both sediments. The biogenic redox product Tc(IV) oxidized rapidly and completely in RG when contacted with air. Oxidation, in contrast, was slow and incomplete in the FRC, in spite of similar molecular scale speciation of Tc compared to RG. X-ray microprobe, electron microprobe, X-ray absorption spectroscopy, and micro X-ray diffraction were applied to the whole sediment and isolated Tc-containing particles. These analyses revealed that non-oxidizable Tc(IV) in the FRC existed as complexes with octahedral Fe(III) within intra-grain domains of 50-100 (micro)m-sized, Fe-containing micas presumptively identified as celadonite. The markedly slower oxidation rates in FRC as compared to RG were attributed to mass

  2. Oxidative dissolution potential of biogenic and abiogenic TcO 2 in subsurface sediments

    Science.gov (United States)

    Fredrickson, James K.; Zachara, John M.; Plymale, Andrew E.; Heald, Steve M.; McKinley, James P.; Kennedy, David W.; Liu, Chongxuan; Nachimuthu, Ponnusamy

    2009-04-01

    Technetium-99 (Tc) is an important fission product contaminant associated with sites of nuclear fuels reprocessing and geologic nuclear waste disposal. Tc is highly mobile in its most oxidized state [Tc(VII)O4-] and less mobile in the reduced form [Tc(IV)O 2· nH 2O]. Here we investigate the potential for oxidation of Tc(IV) that was heterogeneously reduced by reaction with biogenic Fe(II) in two sediments differing in mineralogy and aggregation state; unconsolidated Pliocene-age fluvial sediment from the upper Ringold (RG) Formation at the Hanford Site and a clay-rich saprolite from the Field Research Center (FRC) background site on the Oak Ridge Site. Both sediments contained Fe(III) and Mn(III/IV) as redox active phases, but FRC also contained mass-dominant Fe-phyllosilicates of different types. Shewanella putrefaciens CN32 reduced Mn(III/IV) oxides and generated Fe(II) that was reactive with Tc(VII) in heat-killed, bioreduced sediment. After bioreduction and heat-killing, biogenic Fe(II) in the FRC exceeded that in RG by a factor of two. More rapid reduction rates were observed in the RG that had lower biogenic Fe(II), and less particle aggregation. EXAFS measurements indicated that the primary reduction product was a TcO 2-like phase in both sediments. The biogenic redox product Tc(IV) oxidized rapidly and completely in RG when contacted with air. Oxidation, in contrast, was slow and incomplete in the FRC, in spite of similar molecular scale speciation of Tc compared to RG. X-ray microprobe, electron microprobe, X-ray absorption spectroscopy, and micro X-ray diffraction were applied to the whole sediment and isolated Tc-containing particles. These analyses revealed that non-oxidizable Tc(IV) in the FRC existed as complexes with octahedral Fe(III) within intra-grain domains of 50-100 μm-sized, Fe-containing micas presumptively identified as celadonite. The markedly slower oxidation rates in FRC as compared to RG were attributed to mass

  3. Rapid solidification for preparation of high Tc superconductors

    International Nuclear Information System (INIS)

    Yavari, A.R.

    1988-01-01

    High Tc superconducting oxides are prepared in two different ways using rapid solidification: by oxidation of microcrystalline or amorphous tapes obtained by quenching the liquid alloy and via crystallisation of the amorphous oxide obtained by rapid quenching of the oxide melt. This technique is applied for the first time to the BiCaSrCuO family [fr

  4. Superconductivity

    CERN Document Server

    Poole, Charles P; Farach, Horacio A

    1995-01-01

    Superconductivity covers the nature of the phenomenon of superconductivity. The book discusses the fundamental principles of superconductivity; the essential features of the superconducting state-the phenomena of zero resistance and perfect diamagnetism; and the properties of the various classes of superconductors, including the organics, the buckministerfullerenes, and the precursors to the cuprates. The text also describes superconductivity from the viewpoint of thermodynamics and provides expressions for the free energy; the Ginzburg-Landau and BCS theories; and the structures of the high

  5. Oxidative Stability of Tc(I) Tricarbonyl Species Relevant to the Hanford Tank Waste

    Energy Technology Data Exchange (ETDEWEB)

    Chatterjee, Sayandev [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Hall, Gabriel B. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Levitskaia, Tatiana G. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Walter, Eric D. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Washton, Nancy M. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2015-12-17

    Technetium (Tc), which exists predominately in the liquid supernatant and salt cake fractions of the nuclear tank waste stored at the U.S. DOE Hanford Site, is one of the most difficult contaminants to dispose of and/or remediate. In the strongly alkaline environments prevalent in the tank waste, its dominant chemical form is pertechnetate (TcO4-, oxidation state +7). However, based on experimentation to-date, a significant fraction of the soluble Tc cannot be effectively separated from the wastes and may be present as a non-pertechnetate species. The presence of a non pertechnetate species significantly complicates disposition of low-activity waste (LAW), and the development of methods to either convert them to pertechnetate or to separate the non-pertechnetate species directly is needed. The challenge is the uncertainty regarding the nature and stability of the alkaline-soluble, low-valence, non pertechnetate species in the liquid tank waste. One objective of the Tc management project is to address this knowledge gap. This fiscal year (FY) 2015 report summarizes experimental work exploring the oxidative stability of model low-valence Tc(I) tricarbonyl species, derived from the [Tc(CO)3]+ moiety. These compounds are of interest due to their implied presence in several Hanford tank waste supernatants. Work in part was initiated in FY 2014, and a series of samples containing non-pertechnetate Tc generated ex situ or in situ in pseudo-Hanford tank supernatant simulant solutions was prepared and monitored for oxidation to Tc(VII) (Levitskaia et al. 2014). This experimentation continued in FY 2015, and new series of samples containing Tc(I) as [Tc(CO)3]+•Ligand was tested. The monitoring method used for these studies was a combination of 99Tc NMR and EPR spectroscopies.

  6. In-situ deposition of YBCO high-Tc superconducting thin films by MOCVD and PE-MOCVD

    International Nuclear Information System (INIS)

    Zhao, J.; Noh, D.W.; Chern, C.; Li, Y.Q.; Norris, P.E.; Kear, B.; Gallois, B.

    1991-01-01

    Metal-Organic Chemical Vapor Deposition (MOCVD) offers the advantages of a high degree of compositional control, adaptability for large scale production, and the potential for low temperature fabrication. The capability of operating at high oxygen partial pressure is particularly suitable for in situ formation of high temperature superconducting (HTSC) films. Yttrium barium copper oxide (YBCO) thin films having a sharp zero-resistance transition with T(sub c) greater than 90 K and J(sub c) of approximately 10(exp 4) A on YSZ have been prepared, in situ, at a substrate temperature of about 800 C. Moreover, the ability to form oxide films at low temperature is very desirable for device applications of HTSC materials. Such a process would permit the deposition of high quality HTSC films with a smooth surface on a variety of substrates. Highly c-axis oriented, dense, scratch resistant, superconducting YBCO thin films with mirror-like surfaces have been prepared, in situ, at a reduced substrate temperature as low as 570 C by a remote microwave-plasma enhanced metal-organic chemical vapor deposition (PE-MOCVD) process. Nitrous oxide was used as a reactant gas to generate active oxidizing species. This process, for the first time, allows the formation of YBCO thin films with the orthorhombic superconducting phase in the as-deposited state. The as-deposited films grown by PE-MOCVD show attainment of zero resistance at 72 K with a transition width of about 5 K. MOCVD was carried out in a commercial production scale reactor with the capability of uniform deposition over 100 sq cm per growth run. Preliminary results indicate that PE-MOCVD is a very attractive thin film deposition process for superconducting device technology

  7. Korea's developmental program for superconductivity

    Science.gov (United States)

    Hong, Gye-Won; Won, Dong-Yeon; Kuk, Il-Hyun; Park, Jong-Chul

    1995-04-01

    Superconductivity research in Korea was firstly carried out in the late 70's by a research group in Seoul National University (SNU), who fabricated a small scale superconducting magnetic energy storage system under the financial support from Korea Electric Power Company (KEPCO). But a few researchers were involved in superconductivity research until the oxide high Tc superconductor was discovered by Bednorz and Mueller. After the discovery of YBaCuO superconductor operating above the boiling point of liquid nitrogen (77 K)(exp 2), Korean Ministry of Science and Technology (MOST) sponsored a special fund for the high Tc superconductivity research to universities and national research institutes by recognizing its importance. Scientists engaged in this project organized 'High Temperature Superconductivity Research Association (HITSRA)' for effective conducting of research. Its major functions are to coordinate research activities on high Tc superconductivity and organize the workshop for active exchange of information. During last seven years the major superconductivity research has been carried out through the coordination of HITSRA. The major parts of the Korea's superconductivity research program were related to high temperature superconductor and only a few groups were carrying out research on conventional superconductor technology, and Korea Atomic Energy Research Institute (KAERI) and Korea Electrotechnology Research Institute (KERI) have led this research. In this talk, the current status and future plans of superconductivity research in Korea will be reviewed based on the results presented in interim meeting of HITSRA, April 1-2, 1994. Taejeon, as well as the research activity of KAERI.

  8. Origin of the pressure-dependent Tc valley in superconducting simple cubic phosphorus

    Science.gov (United States)

    Wu, Xianxin; Jeschke, Harald O.; Di Sante, Domenico; von Rohr, Fabian O.; Cava, Robert J.; Thomale, Ronny

    2018-03-01

    Motivated by recent experiments, we investigate the pressure-dependent electronic structure and electron-phonon (e-ph) coupling for simple cubic phosphorus by performing first-principles calculations within the full potential linearized augmented plane-wave method. As a function of increasing pressure, our calculations show a valley feature in Tc, followed by an eventual decrease for higher pressures. We demonstrate that this Tc valley at low pressures is due to two nearby Lifshitz transitions, as we analyze the band-resolved contributions to the e-ph coupling. Below the first Lifshitz transition, the phonon hardening and shrinking of the γ Fermi surface with s -orbital character results in a decreased Tc with increasing pressure. After the second Lifshitz transition, the appearance of δ Fermi surfaces with 3 d -orbital character generate strong e-ph interband couplings in α δ and β δ channels, and hence lead to an increase of Tc. For higher pressures, the phonon hardening finally dominates, and Tc decreases again. Our study reveals that the intriguing Tc valley discovered in experiment can be attributed to Lifshitz transitions, while the plateau of Tc detected at intermediate pressures appears to be beyond the scope of our analysis. This strongly suggests that aside from e-ph coupling, electronic correlations along with plasmonic contributions may be relevant for simple cubic phosphorus. Our findings hint at the notion that increasing pressure can shift the low-energy orbital weight towards d character, and as such even trigger an enhanced importance of orbital-selective electronic correlations despite an increase of the overall bandwidth.

  9. Interplay of CDW, SDW and superconductivity in high-Tc cuprates

    International Nuclear Information System (INIS)

    Panda, S.K.; Rout, G.C.

    2009-01-01

    We present a model calculation of the interplay of the charge density wave (CDW), spin density wave (SDW) and superconductivity in high temperature superconductors. In low doping situation the long range antiferromagnetic order is destroyed to give rise to SDW state accompanied by a CDW state in the system due to doping. For suitable doping the superconductivity appears in the system. The CDW state may describe the pseudogap phenomenon which co-exists with the superconducting phase and extends to normal phase in high-T c systems. These three competiting interactions co-exist together. These three gap parameters are calculated from the model Hamiltonian and solved self-consistently. By varying their coupling constants their interplay are investigated. Finally density of states is calculated for the conduction band which displays the experimental conductance data of Ekino et al. [T. Ekino, Y. Sezaki, H. Fujji, Phys. Rev. B 60 (1999) 6916].

  10. Noise and conversion performance of a high-Tc superconducting Josephson junction mixer at 0.6 THz

    Science.gov (United States)

    Gao, Xiang; Du, Jia; Zhang, Ting; Guo, Yingjie Jay

    2017-11-01

    This letter presents both theoretical and experimental investigations on the noise and conversion performance of a high-Tc superconducting (HTS) step-edge Josephson-junction mixer at the frequency of 0.6 THz and operating temperatures of 20-40 K. Based on the Y-factor and U-factor methods, a double-sideband noise temperature of around 1000 K and a conversion gain of -3.5 dB were experimentally obtained at 20 K. At the temperature of 40 K, the measured mixer noise and conversion efficiency are around 2100 K and -10 dB, respectively. The experimental data are in good agreement with the numerical analysis results using the three-port model. A detailed performance comparison with other reported HTS terahertz mixers has confirmed the superior performance of our presented mixer device.

  11. Superconductivity

    International Nuclear Information System (INIS)

    Langone, J.

    1989-01-01

    This book explains the theoretical background of superconductivity. Includes discussion of electricity, material fabrication, maglev trains, the superconducting supercollider, and Japanese-US competition. The authors reports the latest discoveries

  12. Plasma clearance and biodistribution of oxidatively modified 99mTc-ß-VLDL in rabbits

    Directory of Open Access Journals (Sweden)

    Silva E.L.

    1997-01-01

    Full Text Available The biodistribution and removal from plasma (measured as fractional clearance rate, FCR, per hour of native and oxidatively modified 99mtechnetium-labeled ß-very low density lipoprotein (99mTc-ß-VLDL were investigated in hypercholesterolemic (HC and control (C three-month old New Zealand rabbits. The intracellular accumulation of ß-VLDL labeled with 99mTc was studied in vitro in THP-1 cells and monocyte-derived macrophages isolated from rabbits. After intravenous injection into C rabbits, copper-oxidized ß-VLDL (99mTc-ox-ß-VLDL was cleared from the circulation faster (0.362 ± 0.070/h than native ß-VLDL (99mTc-nat-ß-VLDL, 0.241 ± 0.070/h. In contrast, the FCR of 99mTc-ox-ß-VLDL in HC rabbits was lower (0.100 ± 0.048/h than that of 99mTc-nat-ß-VLDL (0.163 ± 0.043/h. The hepatic uptake of radiolabeled lipoproteins was lower in HC rabbits (0.114 ± 0.071% injected dose/g tissue for 99mTc-nat-ß-VLDL and 0.116 ± 0.057% injected dose/g tissue for 99mTc-ox-ß-VLDL than in C rabbits (0.301 ± 0.113% injected dose/g tissue for 99mTc-nat-ß-VLDL and 0.305 ± 0.149% injected dose/g tissue for 99mTc-ox-ß-VLDL. The uptake of 99mTc-nat-ß-VLDL and 99mTc-ox-ß-VLDL by atherosclerotic aorta lesions isolated from HC rabbits (99mTc-nat-ß-VLDL: 0.033 ± 0.012% injected dose/g tissue and 99mTc-ox-ß-VLDL: 0.039 ± 0.017% injected dose/g tissue was higher in comparison to that of non-atherosclerotic aortas from C rabbits (99mTc-nat-ß-VLDL: 0.023 ± 0.010% injected dose/g tissue and 99mTc-ox-ß-VLDL: 0.019 ± 0.010% injected dose/g tissue. However, 99mTc-nat-ß-VLDL and 99mTc-ox-ß-VLDL were taken up by atherosclerotic lesions at similar rates. In vitro studies showed that both monocyte-derived macrophages isolated from rabbits and THP-1 macrophages significantly internalized more 99mTc-ox-ß-VLDL than 99mTc-nat-ß-VLDL. These results indicate that in cholesterol-fed rabbits 99mTc-ox-ß-VLDL is slowly cleared from plasma and accumulates in

  13. Superconductivity

    International Nuclear Information System (INIS)

    Onnes, H.K.

    1988-01-01

    The author traces the development of superconductivity from 1911 to 1986. Some of the areas he explores are the Meissner Effect, theoretical developments, experimental developments, engineering achievements, research in superconducting magnets, and research in superconducting electronics. The article also mentions applications shown to be technically feasible, but not yet commercialized. High-temperature superconductivity may provide enough leverage to bring these applications to the marketplace

  14. Study on magnetic separation system using high Tc superconducting bulk magnets for water purification technique

    International Nuclear Information System (INIS)

    Oka, T; Kanayama, H; Tanaka, K; Fukui, S; Ogawa, J; Sato, T; Ooizumi, M; Yamaguchi, M; Yokoyama, K; Noto, K

    2009-01-01

    The application of superconducting bulk magnets to the magnetic separation techniques has been investigated for the Mn-bearing waste water drained from the university laboratories. The research has been conducted in comparison with the electromagnets, and the cryo-cooled superconducting solenoid magnet. The separation ratios of ferrite precipitates including Mn element in the waste slurry were estimated by means of the high gradient magnetic separation method with ferromagnetic iron filters in the water channel and open gradient magnetic separation without them. As the magnetic force acting on the particles is given by the product of a magnetization of particles and a gradient of magnetic field, and a superconducting bulk magnet shows a sharp gradient of the magnetic field on the surface, the performances of the bulk magnet system were almost equivalent to those of the superconducting solenoid magnet with wide bore with respect to the magnetic separation ratios. The separation ratios for Mn have reached over 80 % for HGMS and 10 % for OGMS under the flow rates less than 3 liter/min.

  15. Impurity band Mott insulators: a new route to high Tc superconductivity

    Directory of Open Access Journals (Sweden)

    Ganapathy Baskaran

    2008-01-01

    Full Text Available Last century witnessed the birth of semiconductor electronics and nanotechnology. The physics behind these revolutionary developments is certain quantum mechanical behaviour of 'impurity state electrons' in crystalline 'band insulators', such as Si, Ge, GaAs and GaN, arising from intentionally added (doped impurities. The present article proposes that certain collective quantum behaviour of these impurity state electrons, arising from Coulomb repulsions, could lead to superconductivity in a parent band insulator, in a way not suspected before. Impurity band resonating valence bond theory of superconductivity in boron doped diamond, recently proposed by us, suggests possibility of superconductivity emerging from impurity band Mott insulators. We use certain key ideas and insights from the field of high-temperature superconductivity in cuprates and organics. Our suggestion also offers new possibilities in the field of semiconductor electronics and nanotechnology. The current level of sophistication in solid state technology and combinatorial materials science is very well capable of realizing our proposal and discover new superconductors.

  16. Models of high-Tc superconductivity and applications to electric generators and motors

    DEFF Research Database (Denmark)

    Sørensen, Mads Peter

    We present the Ginzburg Landau model for mesoscopic high-Tc superconductors of complex geometry. It is shown that giant vortices can form at boundary defects. The relation between total magnetic flux penetration through the superconductor and the externally applied field is established. This is i...

  17. Superconductivity

    International Nuclear Information System (INIS)

    Andersen, N.H.; Mortensen, K.

    1988-12-01

    This report contains lecture notes of the basic lectures presented at the 1st Topsoee Summer School on Superconductivity held at Risoe National Laboratory, June 20-24, 1988. The following lecture notes are included: L.M. Falicov: 'Superconductivity: Phenomenology', A. Bohr and O. Ulfbeck: 'Quantal structure of superconductivity. Gauge angle', G. Aeppli: 'Muons, neutrons and superconductivity', N.F. Pedersen: 'The Josephson junction', C. Michel: 'Physicochemistry of high-T c superconductors', C. Laverick and J.K. Hulm: 'Manufacturing and application of superconducting wires', J. Clarke: 'SQUID concepts and systems'. (orig.) With 10 tabs., 128 figs., 219 refs

  18. Separation of 99Tc from irradiated molybdenum oxide by extraction with trioctilamine

    International Nuclear Information System (INIS)

    Carvalho, O.G. de.

    1979-01-01

    A separation method of sup( 99 m)Tc, from irradiated molybdenum oxide, by extraction with trioctilamino in 1,2 dichloroethane, 2% v/v is studied. Two preliminary studies are done: 1) Stablishment of the shaking time necessary to reach the equilibrium between the organic and the aqueous phase; 2) Choice of the concentration of solution of TOA in 1,2 dichloroethane to obtain the best separation conditions of sup( 99 m)Tc. After stablishing these two parameters, the study of extraction in solutions of hydrochloric nitric and sulfuric acids in different concentrations is done, followed by the study of the variation of extraction percentage of sup( 99 m)Tc in relation to the molybdenum oxide mass and the back-extraction of sup( 99 m)Tc to the aqueous phase with solutions of perchloric acid 1,0 and 0,1 N and ammonium hydroxide 1,0 N. (Author) [pt

  19. Superconductivity

    International Nuclear Information System (INIS)

    Palmieri, V.

    1990-01-01

    This paper reports on superconductivity the absence of electrical resistance has always fascinated the mind of researchers with a promise of applications unachievable by conventional technologies. Since its discovery superconductivity has been posing many questions and challenges to solid state physics, quantum mechanics, chemistry and material science. Simulations arrived to superconductivity from particle physics, astrophysic, electronics, electrical engineering and so on. In seventy-five years the original promises of superconductivity were going to become reality: a microscopical theory gave to superconductivity the cloth of the science and the level of technological advances was getting higher and higher. High field superconducting magnets became commercially available, superconducting electronic devices were invented, high field accelerating gradients were obtained in superconductive cavities and superconducting particle detectors were under study. Other improvements came in a quiet progression when a tornado brought a revolution in the field: new materials had been discovered and superconductivity, from being a phenomenon relegated to the liquid Helium temperatures, became achievable over the liquid Nitrogen temperature. All the physics and the technological implications under superconductivity have to be considered ab initio

  20. Superconductivity

    CERN Document Server

    Thomas, D B

    1974-01-01

    A short general review is presented of the progress made in applied superconductivity as a result of work performed in connection with the high-energy physics program in Europe. The phenomenon of superconductivity and properties of superconductors of Types I and II are outlined. The main body of the paper deals with the development of niobium-titanium superconducting magnets and of radio-frequency superconducting cavities and accelerating structures. Examples of applications in and for high-energy physics experiments are given, including the large superconducting magnet for the Big European Bubble Chamber, prototype synchrotron magnets for the Super Proton Synchrotron, superconducting d.c. beam line magnets, and superconducting RF cavities for use in various laboratories. (0 refs).

  1. Preparation and characterization of high-Tc superconducting thin films with high critical current densities

    International Nuclear Information System (INIS)

    Vase, P.

    1991-08-01

    The project was carried out in relation to possible cable and electronics applications of high-T c materials. Laser ablation was used as the deposition technique because of its stoichiometry conservation. Films were made in the YBa 2 Cu 3 O 7 compound due to its relatively simple stoichiometry compared to other High-T c compounds. Much attention was paid to the critical current density. A very high critical current density was reached. By using texture analysis by X-ray diffraction, it was found that films with high critical current densities were epitaxial, while films with low critical current densities contained several crystalline orientations. Four techniques for patterning the films were used - photo lithography and wet etch, laser ablation lithography, laser writing and electron beam lithography and ion milling. Sub-micron patterning has been demonstrated without degradation of the superconducting properties. The achieved patterning resolution is sufficient for preparation of many superconducting components. (AB)

  2. Crystal layered structure and superconducting high-Tc behaviour of the mercurocuprates

    International Nuclear Information System (INIS)

    Kuzemsky, A.L.; Kuzemskaya, I.G.; Cheglokov, A.A.

    1998-10-01

    The high-T c superconducting behaviour of the mercurocuprate family HgBa 2 Ca n-1 Cu n O 2n+2+δ was analyzed from the point of view of their layered crystal structure. A dependence of superconducting critical temperature for different members of mercurocuprate family was studied in terms of phenomenological model of layered superconductors. The redistribution of charge was taken into account. This leads to an observable nonmonotonic ''bell''-shaped dependence of T c (n) with a maximum at n=3 and provides a quantitative explanation of the experiments. It was shown that the correlations between the copper valence, lattice parameters, extra oxygen contents and number of layers are essential factors for the physical behaviour and HTSC characterization of the mercurocuprates. (author)

  3. One- and two-dimensional sublattices as preconditions for high-Tc superconductivity

    International Nuclear Information System (INIS)

    Krueger, E.

    1989-01-01

    In an earlier paper it was proposed describing superconductivity in the framework of a nonadiabatic Heisenberg model in order to interprete the outstanding symmetry proper ties of the (spin-dependent) Wannier functions in the conduction bands of superconductors. This new group-theoretical model suggests that Cooper pair formation can only be mediated by boson excitations carrying crystal-spin-angular momentum. While in the three-dimensionally isotropic lattices of the standard superconductors phonons are able to transport crystal-spin-angular momentum, this is not true for phonons propagating through the one- or two-dimensional Cu-O sublattices of the high-T c compounds. Therefore, if such an anisotropic material is superconducting, it is necessarily higher-energetic excitations (of well-defined symmetry) which mediate pair formation. This fact is proposed being responsible for the high transition temperatures of these compounds. (author)

  4. Microwave superconductivity for particle accelerators - How the high TC superconductors measure up

    International Nuclear Information System (INIS)

    Padamsee, H.; Green, K.; Gruschus, J.

    1988-01-01

    Application of superconducting niobium cavities to accelerators for high energy physics, nuclear physics and free electron laser is growing rapidly. Cornell has a long standing effort in the development of superconducting RF accelerator technology. Nb cavities developed here from the basis for constructing the world's highest energy electron accelerator for nuclear physics. These cavities have set a standard against which the behavior of the new superconductors must be compared. From available results on dc critical fields, and the energy gap, it appears that the new materials could make a significant impact on the capabilities of future accelerators. Crucial to this assessment, however, are direct microwave loss measurements, together with measurements of the energy gap and RF frequency dependence as well as the behavior at high RF fields. Latest results on these properties for bulk sintered ceramics, thin films and single crystals at RF frequencies of 1.5 and 6 Ghz are presented

  5. State of the art and trends of high-Tc superconductivity

    International Nuclear Information System (INIS)

    Barone, A.

    1990-01-01

    In this paper a brief account is given on some aspects of the development of high-T c Superconductivity since the last edition of the SATT Conference. This year significant results have been obtained in the challenging endeavor of increasing high critical current densities and in the context of high-T c junctions. The attention is confined to achievements and perspectives in these two topics

  6. 2+1 topological term, anyons and their possible application in high Tc superconductivity

    International Nuclear Information System (INIS)

    Zhu Chuanjie.

    1990-01-01

    I review pedagogically some aspects about the SO(3) non-linear σ-model and the topological Hopf term (or the abelian Chern-Simons term). I argue that the presence of the topological Chern-Simons term is irrelevant (for regular gauge field configurations). I also give a brief introduction to the ideal anyon gas approach to high T c superconductivity. (author). 18 refs

  7. An investigation in texturing high Tc superconducting ceramics by creep sintering

    International Nuclear Information System (INIS)

    Regnier, P.; Deschanels, X.; Maurice, F.; Schmirgeld, L.; Aguillon, C.; Senoussi, S.; Mac Carthy, M.; Tatlock, G.J.

    1991-01-01

    We study in detail the possibility of high-T c superconducting ceramics texturing by high pressing them during sintering. We show texture variations as a function of the applied load, of the deformation, of the temperature, and of the sintering stage length, of the rate of variation of temperature, of the material nature in contact with ceramic and of the original powder quality. We present results obtained by optical microscopy, electronic microscopy, X-rays, and local chemical analysis

  8. Observation of high Tc one dimensional superconductivity in 4 angstrom carbon nanotube arrays

    KAUST Repository

    Zhang, Bing; Liu, Yang; Chen, Qihong; Lai, Zhiping; Sheng, Ping

    2017-01-01

    The only known approach to fabricate large, uniform arrays of 4-Å single wall carbon nanotubes (SWNTs) is by using zeolite crystals as the template, in which the nanotubes are formed by chemical vapor deposition inside the linear channels of the AlPO-5 (AFI for short) zeolite. However, up to now the pore filling factor has been very low, as evidenced by the weight percentage of carbon in thermal gravimetric analysis (TGA) measurements. In this work, we show that by using a new, micro-platelet AFI crystals as the template, combined with the use of a new CVD process, we can increase the TGA result to 22.5wt%, which translates to a pore filling factor of 91%. We have observed one dimensional (1D) superconductivity in such samples. The temperature dependence of resistance shows a smooth decreasing trend below 60 K, and the differential resistance displays a gap that disappears above the 1D superconducting initiation temperature. The observed behaviour is shown to agree very well with the theoretical predictions of 1D superconductivity.

  9. Observation of high Tc one dimensional superconductivity in 4 angstrom carbon nanotube arrays

    KAUST Repository

    Zhang, Bing

    2017-02-14

    The only known approach to fabricate large, uniform arrays of 4-Å single wall carbon nanotubes (SWNTs) is by using zeolite crystals as the template, in which the nanotubes are formed by chemical vapor deposition inside the linear channels of the AlPO-5 (AFI for short) zeolite. However, up to now the pore filling factor has been very low, as evidenced by the weight percentage of carbon in thermal gravimetric analysis (TGA) measurements. In this work, we show that by using a new, micro-platelet AFI crystals as the template, combined with the use of a new CVD process, we can increase the TGA result to 22.5wt%, which translates to a pore filling factor of 91%. We have observed one dimensional (1D) superconductivity in such samples. The temperature dependence of resistance shows a smooth decreasing trend below 60 K, and the differential resistance displays a gap that disappears above the 1D superconducting initiation temperature. The observed behaviour is shown to agree very well with the theoretical predictions of 1D superconductivity.

  10. Rotational loss of a ring-shaped flywheel supported by high Tc superconducting levitation

    International Nuclear Information System (INIS)

    Teshima, Hidekazu; Tawara, Taichi; Shimada, Ryuichi.

    1997-01-01

    This paper describes the experimental results for the rotational loss of a ring-shaped flywheel supported by high T c superconducting levitation. Superconducting levitation is appropriate for rotating a ring-shaped flywheel which has neither shaft nor hub because it is a non-contact and automatically stable levitation without any control systems. The rotational loss has been investigated using a small-scaled experimental machine consisting of 16 bulk superconductors 46 mm in diameter and a ring-shaped flywheel about 300 mm in diameter. The rotational loss decreased as the levitation gap height increased. In low-speed rotational regions, the rotational loss was in proportion to the rotation speed and depended more on the levitation gap. In high-speed rotational regions, the rotational loss was in proportion to the third power of the rotation speed and depended less on the levitation gap. The cubic rotational loss in He was reduced to one-fifth of that in air. The magnetic field pinned in bulk superconductors induces a loss in the materials composing the ring-shaped flywheel. The rotational loss of a ring-shaped flywheel supported by superconducting levitation can be reduced by improving the uniformity of the magnetic fields along the ring, enlargement of the bulk superconductor(s), and densely arranging the bulk superconductors. (author)

  11. Levitation properties of a ring-shaped flywheel supported by high Tc superconducting levitation

    International Nuclear Information System (INIS)

    Teshima, Hidekazu; Tawara, Taichi; Shimada, Ryuichi.

    1997-01-01

    In this paper we propose a new combination of high T c superconducting levitation and ring-shaped flywheel energy storage systems. Superconducting levitation is appropriate for rotating a ring-shaped flywheel which has neither shaft nor hub, because it is a non-contact and automatically stable levitation without any control systems. The levitation properties such as static and dynamic lateral stiffnesses, lateral damping, and lateral vibration during rotation have been investigated using a small-scaled experimental machine consisting of 16 bulk superconductors 46 mm in diameter and a ring-shaped flywheel about 300 mm in diameter. The spring constant increased as the levitation gap height decreased, and the dynamic spring constant was slightly higher than the static constant. The damping coefficient increased as the gap height decreased and the vibration amplitude increased. The experimental critical speed was in good agreement with the calculated one using a one-degree of freedom model. Finally, the possibility of large-scaled practical systems is discussed from the viewpoint of superconducting levitation. (author)

  12. Assessment of potential advantages of high Tc-superconductors for technical application of superconductivity

    International Nuclear Information System (INIS)

    Schauer, F.; Juengst, K.P.; Komarek, P.; Maurer, W.

    1987-09-01

    A first assessment of the technical and economical consequences of liquid nitrogen cooling of new superconductors is given. For the investigation the applications of superconductivity are classified in two categories: First, systems where superconductors are practically indispensable for achieving the system's objectives; second, superconductor applications in competition with highly developed conventional technologies. Further development of those superconducting systems in the first category for which the cost of cryogenic equipment is a smaller fraction of the total system cost (e.g. fusion reactor or MHD generator) will hardly be affected. However, for systems like particle accelerators, research magnets, and NMR spectroscopy and imaging systems, the cryogenic equipment expenditures are significant and LN 2 cooling leads here to a reduction of investment and operating costs, to simplified handling and maintenance, to better reliability and availability, and will thereby improve the acceptance and further spread of these systems. In the second category each application of superconductivity has to be compared with its conventional counterpart, separately. Here, electonic components, power switches, resistive current limiters, and especially the power transmission cables are those applications which look most promising. For magnet applications the main advantageous arguments are less the cost saving aspect but more the higher reliability, simplicity, N 2 -availability, and ease of handling. (orig.) [de

  13. Performance prediction of high Tc superconducting small antennas using a two-fluid-moment method model

    Science.gov (United States)

    Cook, G. G.; Khamas, S. K.; Kingsley, S. P.; Woods, R. C.

    1992-01-01

    The radar cross section and Q factors of electrically small dipole and loop antennas made with a YBCO high Tc superconductor are predicted using a two-fluid-moment method model, in order to determine the effects of finite conductivity on the performances of such antennas. The results compare the useful operating bandwidths of YBCO antennas exhibiting varying degrees of impurity with their copper counterparts at 77 K, showing a linear relationship between bandwidth and impurity level.

  14. Hyperfine interactions associated with iron substitute superconducting oxides

    International Nuclear Information System (INIS)

    Ellis, D.E.; Dunlap, B.D.; Saitovitch, E.B.; Azevedo, I.S.; Scorzelli, R.B.; Kimball, C.W.

    1988-01-01

    Theoretical and experimental Moessbauer spectroscopy studies have been made concerning charge and spin densities and magnetic hyperfine fields (H hf in iron-substituted superconducting oxides. Calculations were carried out in the self-consistent-field embedded cluster model using local density theory (SCF-Xα) with a variational atomic orbital basis. Spectral densities and changes in charge and spin density were monitored around neighboring Cu sites, as well as Fe impurity site, in La 2 Cu 1-x Fe x O 4 and YBa 2 Cu 3-x Fe x O 7-y compounds. Moessbauer isomer shifts (IS), quadrupole splittings (QS) and H hf are obtained by fitting multiline models to the observed spectra and are compared with SCF-Xα results for specific lattice sites. The influence of oxygen vacancies and partial oxygen disorder is modelled and compared with the experimental data on variable oxygen content and disorder. (author)

  15. Separation of sup(99m)Tc from 99Mo through a hydrous zirconium oxide column

    International Nuclear Information System (INIS)

    Mengatti, J.

    1980-01-01

    The preparation of 99 Mo-,sup(99m)Tc generator based on the adsorption of 99 Mo on hydrous zirconium oxide column, employing the in exchange technique, is described. The adsorption of 99 Mo on hydrous zirconium oxide (HZO) and the separation of sup(99m)Tc, generated by the decay of 99 Mo with saline solution, are analised. The sup(99m)Tc separation yield, pH of the eluted solution, aspect of the elution curve and the adsorption of 99 Mo on hydrous zirconium oxide calcined at 800 0 C are studied. The chemical and radioactive purities of the final product are analysed and the variation of the elution yield for successive elutions is studied. (Author) [pt

  16. Magnetism and superconductivity of some Tl-Cu oxides

    Science.gov (United States)

    Datta, Timir

    1991-01-01

    Many copper oxide based Thallium compounds are now known. In comparison to the Bi-compounds, the Tl-system shows a richer diversity; i.e., High Temperature Superconductors (HTSC) can be obtained with either one or two Tl-0 layers (m = 1,2); also, the triple-digit phases are easier to synthesize. The value of d, oxygen stoichiometry, is critical to achieving superconductivity. The Tl system is robust to oxygen loss; Tl may be lost or incorporated by diffusion. A diffusion coefficient equal to 10 ms at 900 C was determined. Both ortho-rhombic and tetragonal structures are found, but HTSC behavior is indifferent to the crystal symmetry. This system has the highest T(sub c) confirmed. T(sub c) generally increases with p, the number of CuO layers, but tends to saturate at p = 3. Zero resistance was observed at temperatures as great as 125 K. Most of these HTSC's are hole type, but the Ce-doped specimens may be electronic. The magnetic aspects were studied; because in addition to defining the perfectly diamagnetic ground state as in conventional superconductors, magnetism of the copper oxides show a surprising variety. This is true of both the normal and the superconducting states. Also, due to the large phonon contribution to the specific heat at the high T(sub c) jump, electronic density of states, D(Ef), and coherence length are uncertain, and thus, are estimated from the magnetic results. Results from the Tl-system CuO, LaBaCuO,120 and the Bi-CuO compounds are discussed. The emphasis is on the role of magnetism in the Tl-CuO HTSC, but technological aspects are also pointed out.

  17. Superconductivity

    International Nuclear Information System (INIS)

    Kakani, S.L.; Kakani, Shubhra

    2007-01-01

    The monograph provides readable introduction to the basics of superconductivity for beginners and experimentalists. For theorists, the monograph provides nice and brief description of the broad spectrum of experimental properties, theoretical concepts with all details, which theorists should learn, and provides a sound basis for students interested in studying superconducting theory at the microscopic level. Special chapter on the theory of high-temperature superconductivity in cuprates is devoted

  18. Collective excitations and superconductivity in reduced dimensional systems - Possible mechanism for high Tc

    International Nuclear Information System (INIS)

    Santoyo, B.M.

    1989-01-01

    The author studies in full detail a possible mechanism of superconductivity in slender electronic systems of finite cross section. This mechanism is based on the pairing interaction mediated by the multiple modes of acoustic plasmons in these structures. First, he shows that multiple non-Landau-damped acoustic plasmon modes exist for electrons in a quasi-one dimensional wire at finite temperatures. These plasmons are of two basic types. The first one is made up by the collective longitudinal oscillations of the electrons essentially of a given transverse energy level oscillating against the electrons in the neighboring transverse energy level. The modes are called Slender Acoustic Plasmons or SAP's. The other mode is the quasi-one dimensional acoustic plasmon mode in which all the electrons oscillate together in phase among themselves but out of phase against the positive ion background. He shows numerically and argues physically that even for a temperature comparable to the mode separation Δω the SAP's and the quasi-one dimensional plasmon persist. Then, based on a clear physical picture, he develops in terms of the dielectric function a theory of superconductivity capable of treating the simultaneous participation of multiple bosonic modes that mediate the pairing interaction. The effect of mode damping is then incorporated in a simple manner that is free of the encumbrance of the strong-coupling, Green's function formalism usually required for the retardation effect. Explicit formulae including such damping are derived for the critical temperature T c and the energy gap Δ 0 . With those modes and armed with such a formalism, he proceeds to investigate a possible superconducting mechanism for high T c in quasi-one dimensional single-wire and multi-wire systems

  19. High Tc superconductivity in YBa2Cu3O7-x studied by PAC and PAS

    International Nuclear Information System (INIS)

    Zhu Shengyun; Li Anli; Zheng Shengnan; Huang Hanchen; Li Donghong; Din Honglin; Du Hongshan; Sun Hancheng

    1993-01-01

    High T c superconductivity has been investigated in YBaCuO by both perturbed angular correlation and positron annihilation spectroscopy techniques as a function of temperature from 77 to 300 K. An abrupt change has been observed in the positron lifetime and Doppler broadening and the electric field gradient and its asymmetry parameter across T c , indicating a transition of two- to one-dimensional Cu-O-Cu chain structure and a charge transfer from CuO layers to CuO chains. An anomaly of the normal state has been demonstrated around 125 K, which is attributed to the structural instability. (orig.)

  20. Electronic Instability at High Flux-Flow Velocities in High-Tc Superconducting Films

    DEFF Research Database (Denmark)

    Doettinger, S. G.; Huebener, R. P.; Gerdemann, R.

    1994-01-01

    At high flux-flow velocities in type-II superconductors the nonequilibrium distribution of the quasiparticles leads to an electronic instability and an aburpt switching into a state with higher electric resistivity, as predicted by Larkin and Ovchinnikow (LO). We report the first obervation...... of this effect in a high-temperature superconductor, namely in epitaxial c-axis oriented films of YBa(2)Cu3O(7)-(delta). Using the LO therory, we have extracted from out results the inelastic quasiparticle scattering rare tau(in)(-1), which strongly decreases with decreasing temperature below T-c...

  1. Spin-fluctuation mechanism of high-Tc superconductivity and order-parameter symmetry

    International Nuclear Information System (INIS)

    Izyumov, Yurii A

    1999-01-01

    The notion that electrons in high-T c cuprates pair via antiferromagnetic spin fluctuations is discussed and the symmetry of the superconducting order parameter is analyzed. Three approaches to the problem, one phenomenological (with an experimental dynamic magnetic susceptibility) and two microscopic (involving, respectively, the Hubbard model and the tJ-model) are considered and it is shown that in each case strong-coupling theory leads to a d-wave order parameter with zeros at the Fermi surface. The review then proceeds to consider experimental techniques in which the d-symmetry of the order parameter may manifest itself. These include low-temperature thermodynamic measurements, measurements of the penetration depth and the upper critical field, Josephson junction experiments to obtain the phase of the superconducting order parameter, and various spectroscopic methods. The experimental data suggest that the order parameter in cuprates is d x 2 -y 2 -wave. Ginzburg-Landau theory for a superconductor with a d-wave order parameter is outlined and both an isolated vortex and a vortex lattice are investigated. Finally, some theoretical aspects of the effects of nonmagnetic impurities on a d-wave superconductor are considered. (reviews of topical problems)

  2. Feshbach shape resonance for high Tc superconductivity in superlattices of nanotubes

    International Nuclear Information System (INIS)

    Bianconi, Antonio

    2006-01-01

    The case of a Feshbach shape resonance in the pairing mechanism for high T c superconductivity in a crystalline lattice of doped metallic nanotubes is described. The superlattice of doped metallic nanotubes provides a superconductor with a strongly asymmetric gap. The disparity and different spatial locations of the wave functions of electrons in different subbands at the Fermi level should suppress the single electron impurity interband scattering giving multiband superconductivity in the clean limit. The Feshbach resonances will arise from the component single-particle wave functions out of which the electron pair wave function is constructed: pairs of wave functions which are time inverse of each other. The Feshbach shape resonance increases the critical temperature by tuning the chemical potential at the Lifshitz electronic topological transition (ETT) where the Fermi surface of one of the bands changes from the one dimensional (1D) to the two dimensional (2D) topology (1D/2D ETT). (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (Abstract Copyright [2006], Wiley Periodicals, Inc.)

  3. Appearance of ferroelectricity by suppressing superconductivity in nanoparticle dispersed glassy precursor for high Tc superconductor

    International Nuclear Information System (INIS)

    Mukherjee, Soma; Chaudhuri, B.K.; Sakata, H.

    2003-01-01

    The multicomponent Bi 1.8 Pb 0.3 Sr 2 Ca 2 Cu 2.8 K 0.2 O δ (FG) glass is found to show ferroelectric (FE) transition around T fc = 530K. Microstructural (TEM) studies of these glasses indicated the presence of nano-crystalline particles/ clusters (∼10-30 nm size). In this glass-nanoparticle composite (GNC), presence of ferroelectric nano-particles/ islands is considered to be responsible for the FE behavior. The K-free FG type glasses showing no dielectric anomaly (or ferroelectricity) are precursors of high T c superconductors which become superconductors (T c ∼80K) by annealing around 840 degC. The K-doped (FG) GNC is, however, not superconducting in the corresponding annealed phase which indicates suppression of superconductivity due to the presence of K or by the appearance of ferroelectricity. Transport and dielectric properties of both K doped and undoped GNC have been studied and they are found to be semiconducting and follow non-adiabatic small polaron hopping conduction mechanism. (author)

  4. Lateral restorable characteristics of the high-Tc superconducting maglev vehicle above the permanent magnet guideway

    International Nuclear Information System (INIS)

    Ma, G.T.; Wang, J.S.; Lin, Q.X.; Liu, M.X.; Deng, Z.G.; Li, X.C.; Liu, H.F.; Zheng, J.; Wang, S.Y.

    2009-01-01

    The lateral restorable characteristics of a translational symmetry high-T c superconducting maglev system are investigated by measuring its resonant frequency (f RF ) after a lateral displacement. The difference between whether this lateral displacement is restorable, meaning elastic or inelastic, is determined by whether or not the maglev body returns to its original position after a lateral displacement. The maximum restorable lateral displacement (δ MRLD ) is determined by the sudden change of the f RF vs. the maximum lateral displacement (δ MLD ) curve. The f RF of the high-T c superconducting maglev system with different field-cooling height (FCH) and working height (WH) was obtained from the frequency domain vibration curve which was measured by a vibration measurement system. The results showed that, the δ MRLD was reduced when the WH was decreased. The maximum restorable guidance force (F MRGF ) was found to not always increase with the lowering of the WH for the same FCH. The lateral restorable stiffness (k LRS ) was always enhanced with the decrease of the WH. The decrease of the δ MRLD with the WH is interpreted by the fact that, the tangential field component (ΔH) across the surface of the high-T c superconductor (HTSC) is easier to exceed the J c λ value (J c is the critical current density and λ is the London penetration depth) when the WH is lowered, and this makes the trapped flux lines become more susceptible in escaping its pinning sites.

  5. Sonolytic Oxidation of Tc(IVO2nH2O Nanoparticles to Tc(VIIO4 in Aqueous Solution

    Directory of Open Access Journals (Sweden)

    M. Zakir

    2010-04-01

    Full Text Available Sonolysis of a hydrosol of TcO2nH2O was investigated in the Ar- or He- atmosphere. Colloidal TcO2nH2O nanoparticles were irradiated with a 200 kHz and 1.25 W/cm2 ultrasound. It was found that the TcO2nH2O colloids dispersed in an aqueous solution (under Ar or He atmosphere was completely dissolved by ultrasonic irradiation (200 kHz, 200 W. The original brownish black color of the suspension slowly disappeared leaving behind a colorless solution. This change suggests that oxidation of Tc(IV to Tc(VII takes place. The oxidation was almost complete during 30 minutes sonication time under argon atmosphere for initial concentration of 6.0E-5 M. Addition of t-butyl alcohol, an effective radical scavenger which readily reacts with OH radicals, supressed the dissolution of TcO2nH2O colloids. This reaction indicates that TcO2nH2O molecules are oxidized by OH radicals produced in cavitation bubbles.

  6. Quantification of oxygen and carbon in high Tc superconducting films by (α,α) elastic resonance technique

    International Nuclear Information System (INIS)

    Vizkelethy, G.; Revesz, P.

    1993-01-01

    The quantification of oxygen and carbon in high-temperature (T c ) superconducting oxide thin films was made by employing elastic resonance in He backscattering analysis. A method combining the oxygen resonance technique and channeling was presented for measuring the nature of the oxygen disorder near the surface and the interface in a YBCO superconducting film grown on an MgO substrate. The oxygen resonance technique was used to quantify the oxygen profiling in the metal/YBCO contacts, showing that Zr and Nb act as sinks to oxygen from YBCO films and are oxidized in the forms Zr/ZrO 2 /YBCO/MgO and Nb 0.2 O/YBCO/MgO after annealing in a vacuum at 350 o C. We combined the carbon and oxygen resonances to determine the carbon contamination and oxygen concentration changes on the YBCO surface after coating and baking the photoresist. Residual carbon on the surface and a thin layer of oxygen depletion near the YBCO surface have been observed. The residual carbon in Bi 2 Sr 2 CaCu 2 O 8 films made by the decomposition of metallo-organic precursors was quantified using carbon resonance. (author)

  7. Characterization of superconducting thin films by infrared reflection

    International Nuclear Information System (INIS)

    Gervais, F.

    1988-01-01

    Infrared reflectivity spectroscopy is shown to be a powerful tool to characterize the new high-Tc oxide superconductors since it gives information about the superconducting gap, phonons, plasmon and possibly low-energy electronic excitations such as excitons, information relevant to understand the mechanism of superconductivity [fr

  8. Superconductivity

    International Nuclear Information System (INIS)

    Caruana, C.M.

    1988-01-01

    Despite reports of new, high-temperature superconductive materials almost every day, participants at the First Congress on Superconductivity do not anticipate commercial applications with these materials soon. What many do envision is the discovery of superconducting materials that can function at much warmer, perhaps even room temperatures. Others hope superconductivity will usher in a new age of technology as semiconductors and transistors did. This article reviews what the speakers had to say at the four-day congress held in Houston last February. Several speakers voiced concern that the Reagan administration's apparent lack of interest in funding superconductivity research while other countries, notably Japan, continue to pour money into research and development could hamper America's international competitiveness

  9. Effect of superconducting transition on microcreep of high-TC ceramics

    International Nuclear Information System (INIS)

    Soldatov, V.P.; Natsik, V.D.; Chajkovskaya, N.M.

    1991-01-01

    Influence of N-S and S-N transition on microplastic deformation kinetics of YBa 2 Cu 3 O 7-δ ceramic samples by there deformation in liquid nitrogen under microscreep conditions is studied. Superconductivity disruption in the sample was achieved by critical value currents. It is shown, that N-S transition increases creep rate,whereas S-N transition slows it down. Microplastic deformation rate by sample state change may very by two-eight times. Influence of heat expansion on creep kinetics as probable associated effect is analyzed. Assumption is expressed, that stimulated transition effect on microplastic deformation of ceramic samples is related to change of their electron state in the area of Josephson contacts between grains

  10. Characteristic study of high-Tc superconducting maglev under side-loading

    International Nuclear Information System (INIS)

    Wang Wei; Wang Jiasu; Liu Wei; Zheng Jun; Lin Qunxu; Pan Siting; Deng Zigang; Ma Guangtong; Wang Suyu

    2009-01-01

    In practical application of High-T c Superconducting (HTS) maglev, slant is an observable defect. It was caused by constantly one side on and off the vehicle by passengers. So far, this phenomenon has not been reported yet. In order to understand its influence on the stability of the HTS maglev, we experimentally studied the dynamic characteristic and slant effect of HTS maglev under center-load and side-load. It was found that load destabilizes the vehicle, and the side-load can obviously slant the vehicle body. In the end, the pre-load method was proposed to enhance the dynamic stability and suppress the slant, which proved to be considerably effective. These results are critical in practical running of HTS maglev

  11. The design of high-Tc superconductors - Room-temperature superconductivity?

    International Nuclear Information System (INIS)

    Tallon, J.L.; Storey, J.G.; Mallett, B.

    2012-01-01

    This year is the centennial of the discovery of superconductivity and the 25th anniversary of the discovery of high-T c superconductors (HTS). Though we still do not fully understand how HTS work, the basic rules of design can be determined from studying their systematics. We know what to do to increase T c and, more importantly, what to do to increase critical current density J c . This in turn lays down a challenge for the chemist. Can the ideal design be synthesized? More importantly, what are the limits? Can one make a room-temperature superconductor? In fact fluctuations place strict constraints on this objective and provide important guidelines for the design of the ideal superconductor.

  12. Debye frequency and interplay of superconductivity and antiferromagnetism in high Tc superconductors

    International Nuclear Information System (INIS)

    Panigrahy, N.N.; Mahapatra, D.; Panda, B.N.; Rout, G.C.

    2006-01-01

    The interplay between superconductivity (SC) and antiferromagnetism (AFM) is studied in strongly correlated systems: R 2-x M x CuO 4 (R = Nd, La, Pr. Gd; M = Sr, Ce) due to electron-phonon interaction, It is assumed that SC arises due to BCS pairing mechanism in presence of AFM in Cu lattices of Cu-O planes, Debye frequency ω D dependence of high temperature SC gap as well as staggered magnetic field at different temperatures are calculated analytically and solved self-consistently with respect to half-filled band situation for different model parameters (temperature parameter θ and hybridization parameter ν, λ 1 and λ 2 being the SC and AF coupling parameters, respectively). The SC gap and AFM gap are studied in their coexistence phase for different Debye frequencies. (author)

  13. Biogeochemistry of Fe and Tc Reduction and Oxidation in FRC Sediment

    International Nuclear Information System (INIS)

    John M, Zachara; James K, Fredrickson; Ravi K, Kukkadapu; Steven C, Smith; David W, Kennedy

    2004-01-01

    The objectives are: (1) To rigorously characterize the distribution of Fe(II) and Fe(III) in FRC sediment. (2) To identify changes to Fe(II)/Fe(III) distribution and concentration resulting from DIRB activity. (3) To determine the dependence of Tc(VII) reduction rate on biogenic Fe(II) and it's forms. (4) To establish tendency of Tc(IV) and biogenic Fe(II) to oxidize and their effects on Tc immobilization. The mineralogic and chemical properties of the pristine, bioreduced, and chemically extracted FRC sediments were characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD), X-ray microscopy (XRM, at the PNC-CAT beamline at APS), Moessbauer spectroscopy, and scanning and transmission electron microscopy with lattice fringe imaging. Chemical extraction included dithionite-citrate-bicarbonate (DCB), acid ammonium oxalate (AAO), and hydroxylamine hydrochloride (HAH). The FRC sediment was incubated under anoxic conditions with the facultative dissimilatory metal-reducing bacterium Shewanella putrefaciens, strain CN32 in defined aqueous solutions/media with bicarbonate and PIPES buffers for time periods exceeding 75 d. Lactate was used as the electron donor. Aqueous and sorbed Fe(II) (ferrozine assay and 0.5 N HCl extraction) and Mn(II) (ICP-MS and 10 mM CuSO 4 extraction), and pH were monitored to define the reduction progress and extent. The bioreduced materials were characterized using the abovementioned techniques. Bioreduced (pasteurized) sediment or chemically extracted/reduced sediment spiked with Fe(II) was washed with a PIPES buffer/electrolyte solution, and spiked with NaTc(VII)O 4 to yield a concentration of 20 (micro)M. The Tc(VII)-spiked samples were agitated and equilibrated at 25 C and sampled over time to assess the Tc(VII) reduction rate. Selected sediment samples containing 20 (micro)M of reduced Tc [Tc(IV)] were subjected to oxidation by: (1) successive headspace replacements of air, and (2) open system equilibration with air. Removed aqueous

  14. Powder of a copper oxide superconductor precursor, fabrication process and use for the preparation of superconducting oxide

    International Nuclear Information System (INIS)

    Dehaudt, P.

    1990-01-01

    The precursor powder comprises at least a copper compound (hydroxide, oxide and hydroxynitrates), at least a rare earth and/or yttrium compound (nitrates, hydroxides and hydroxynitrates) or bismuth oxide and at least an alkaline earth nitrate. It can be prepared by atomization drying of a suspension a copper precipitate or coprecipitate and other elements of the superconducting oxide in solution [fr

  15. Low-frequency noise in high-Tc superconducting thick films

    International Nuclear Information System (INIS)

    Aponte, J.M.; Gutierrez, G.; Octavio, M.

    1990-01-01

    In this paper experimental results on the resistance noise in thick films of YBa 2 Cu 3 O 7-δ in the vicinity of the superconducting transition are reported. The measurements were performed in samples with broad resistive transitions and in the frequency range from 1Hz to 100 Hz. The power spectral density S v /V 2 of the excess noise is obtained by subtracting the current-independent background noise from the total measured noise. The authors observed that at the transition, the magnitude of S v /V 2 rises above its level at room temperature exhibiting peaks at the same temperatures at which R -1 dR/dT has maxima. The authors performed measurements of S v /V 2 as a function of the current through the sample and the authors found that it diverges as the critical current is approached from above and that it is zero below the critical current. This transition is found to be described quite well by a percolation model

  16. A magnetic levitation rotating plate model based on high-Tc superconducting technology

    Science.gov (United States)

    Zheng, Jun; Li, Jipeng; Sun, Ruixue; Qian, Nan; Deng, Zigang

    2017-09-01

    With the wide requirements of the training aids and display models of science, technology and even industrial products for the public like schools, museums and pleasure grounds, a simple-structure and long-term stable-levitation technology is needed for these exhibitions. Opportunely, high temperature superconducting (HTS) technology using bulk superconductors indeed has prominent advantages on magnetic levitation and suspension for its self-stable characteristic in an applied magnetic field without any external power or control. This paper explores the feasibility of designing a rotatable magnetic levitation (maglev) plate model with HTS bulks placed beneath a permanent magnet (PM) plate. The model is featured with HTS bulks together with their essential cryogenic equipment above and PMs below, therefore it eliminates the unclear visual effects by spray due to the low temperature coolant such as liquid nitrogen (LN2) and additional levitation weight of the cryogenic equipment. Besides that, a matched LN2 automation filling system is adopted to help achieving a long-term working state of the rotatable maglev plate. The key low-temperature working condition for HTS bulks is maintained by repeatedly opening a solenoid valve and automatically filling LN2 under the monitoring of a temperature sensor inside the cryostat. With the support of the cryogenic devices, the HTS maglev system can meet all requirements of the levitating display model for exhibitions, and may enlighten the research work on HTS maglev applications.

  17. Antiferromagnetic and superconducting gaps and their interrelation in high-Tc cuprates

    International Nuclear Information System (INIS)

    Arrigoni, E.; Zacher, M.G.; Eckl, T.; Hanke, W.

    2003-01-01

    We propose a phenomenological model, comprising a microscopic SO(5) model plus the on-site Hubbard interaction U (projected SO(5) model) to understand the interrelation between the d-wave-gap modulation observed by recent angle-resolved photoemission experiments in the insulating antiferromagnet Ca 2 CuO 2 Cl 2 and the d-wave gap of high-T c superconducting materials. The on-site interaction U is important in order to produce a Mott gap of the correct order of magnitude, which would be absent in an exact SO(5) theory. The projected SO(5)-model explains the gap characteristics, namely both the symmetry and the different order of magnitude of the gap modulations between the AF and the SCc phases. Furthermore, it is shown that the projected SO(5) theory can provide an explanation for a recent observation [E. Pavarini et al., Phys. Rev. Lett. 87, 47003 (2001)], i. e. that the maximum T c observed in a large variety of high-T c cuprates scales with the next-nearest-neighbor hopping matrix element t'. (Abstract Copyright [2003], Wiley Periodicals, Inc.)

  18. Nonlinear vibration behaviors of high-Tc superconducting bulks in an applied permanent magnetic array field

    Science.gov (United States)

    Li, Jipeng; Li, Haitao; Zheng, Jun; Zheng, Botian; Huang, Huan; Deng, Zigang

    2017-06-01

    The nonlinear vibration of high temperature superconducting (HTS) bulks in an applied permanent magnetic array (Halbach array) field, as a precondition for commercial application to HTS maglev train and HTS bearing, is systematically investigated. This article reports the actual vibration rules of HTS bulks from three aspects. First, we propose a new numerical model to simplify the calculation of levitation force. This model could provide precise simulations, especially the estimation of eigenfrequency. Second, an approximate analytic solution of the vibration of the HTS bulks is obtained by using the method of harmonic balance. Finally, to verify the results mentioned above, we measure the vertical vibration acceleration signals of an HTS maglev model, consisting of eight YBaCuO bulks, oscillating freely above a Halbach array with large displacement excitation. Higher order harmonic components, which indicate the nonlinear vibration phenomenon, are detected in the responses. All the three results are compared and agreed well with each other. This study combines the experimental and theoretical analyses and provides a deep understanding of the physical phenomenon of the nonlinear vibration and is meaningful for the vibration control of the relevant applications.

  19. A study on the development of high-Tc superconducting wire

    International Nuclear Information System (INIS)

    Won, Dong Yeon; Lee, Hee Gyoun; Kim, Chan Joong

    1991-09-01

    High magnetization YBaCuO superconductor was prepared with additions of BaSnO 3 , SnO 2 and SiC by partial melt processing. Addition of BaSnO 3 increased the magnetic property of YBaCuO by flux pinning action of finely dispersed BaSnO 3 particles, while addition of SnO 2 decreased the magnetic property, because the size of particle was larger than that of BaSnO 3 . BiPbSrCaCuO superconducting tape of single filament was prepared by powder-in-tube method using silver as a shearth material. The fabrication techniques involves powder packing, swaging, drawing and cold rolling/pressing method. The final dimension of wire after drawing is 1.2mm diameter. The wire was pressed into a tape form with a thickness of 70micron and a width of 3mm. The obtained critical current density of the prepared tape was 2000A/cm 2 at 77K. (Author)

  20. An investigation into texturing of high-Tc superconducting ceramics by creep-sintering

    International Nuclear Information System (INIS)

    Regnier, P.; Le Hazif, R.; Chaffron, L.

    1989-01-01

    The possibility of preparing highly textured samples of YBa 2 Cu 3 O 7-x high-Tc ceramics by creep-sintering under an uniaxial stress was investigated in detail. It is shown that the quality of the texture is sharply dependant on: the applied load, the temperature of the sintering dwell, the rate at which this dwell is reached, the exact instant at which the load is applied and the nature of the material in contact with the sample. It is also shown that further annealing without applied stress enhances the texture and considerably increases the grain size. Deformation, which was systematically recorded, occurs within a few minutes after the load is applied and exhibits a stress dependance typical of a viscous flow. Systematic examination by polarized light microscopy has indicated that the texture was homogeneous throughout the whole thickness of all the prepared samples. The resistivity versus temperature curves show that the transition is very sharp and well above 77 K

  1. Growth and characterization of high-Tc Y1Ba2Cu3O7-x superconducting thin films by chemical vapor deposition

    International Nuclear Information System (INIS)

    Feng, A.

    1992-01-01

    In chapter I, the current status of high-Tc superconductors (especially Y 1 Ba 2 Cu 3 O 7-x ), their microstructures and their unique physical properties are reviewed. An introduction to the potential and importance of those high-Tc superconductors in practical applications, especially for the application of YBCO thin films in microelectronics, is given. A general description of the common YBCO thin film fabrication and characterization techniques is also presented in this first chapter. Chapter II describes a new CVD process, temperature-controlled chemical vapor deposition (TC-CVD) for the growth of YBCO superconducting thin films on substrates of practical importance, such as sapphire (Al 2 O 3 ) and on substrates of lattice matched perovskite-type single crystals, such as LaAlO 3 . In order to verify the viability of this new CVD process the qualities of YBCO superconducting thin films were examined by various characterization methods, such as resistivity vs. temperature (R vs. T), scanning electron microscopy (SEM), X-ray diffraction (XRD), and magnetic susceptibility (x) measurements. Chapter III deals with the effect of substrate temperature on the properties of YBCO thin films made by TC-CVD. The principle objective of this study is to raise the transition temperature and critical current densities of CVD YBCO superconducting thin films. Understanding the relations between YBCO film growth process and varying substrate temperatures proved to be crucial in reaching this goal. The authors present the characterization results of YBCO thin films produced by different temperature schemes, to illustrate the importance of varying substrate temperature during the film growth. In chapter IV, the Rutherford backscattering (RBS) channeling technique is described. They have used RBS channeling to characterize the epitaxial YBCO thin film's crystallinity and lattice alignment. Transmission electron microscopy studies are also included

  2. Propagation of 1-THz bandwidth electrical pulses on high Tc superconducting transmission lines

    International Nuclear Information System (INIS)

    Nuss, M.C.; Mankiewich, P.M.; Howard, R.E.; Harvey, T.E.; Brandle, C.D.; Straugh, B.L.; Smith, P.R.

    1989-01-01

    The new high temperature superconductors have triggered enormous interest not only because of the unique physics involved but also because of their technical potentials, such as the promise for propagation of extremely short electrical pulses. Superconducting band caps of --20TH z are predicted assuming BCS theory for the superconductor, making lossless propagation of electrical pulses as short as 50 fs possible. Despite microwave measurements at low frequencies of several gigahertz first studies at higher frequencies by Dykaar et al have shown distortion-free propagation of 100-GHz electrical pulses on YBa 2 Cu 3 O 3 (YBCO) lines for --5-mm propagation distance. Results were also reported for aluminum coplanar lines and a YBCO ground plane. The authors report on the propagation of 1-ps electrical pulses (1-THz bandwidth) on YBCO coplanar transmission lines defined on lanthanum gallate (LaGaO 3 ) as a substrate. On LaGaO 3 , YBCO grows highly oriented as on SrTiO 3 . However, unlike SrTiO 3 , LaGaO 3 has a much lower dielectric constant and small losses in the terahertz frequency range. Electrical pulses of --750-fs duration are generated in a radiation-damaged silicon-on-sapphire photoconductive switch integrated into a 20-μm coplanar stripline with 10-μm spacing and excited with 100-fs optical pulses from a CPM laser. An μ1-THz bandwidth electrical contact is made to the YBCO coplanar stripline defined on LaGaO 3 using a flip-chip geometry. They find that electrical pulses broaden only from 750 fs to 1 ps with little loss in amplitude on traveling through their flip-chip input and propagated electrical pulses are probed by electooptic sampling in two small LiTaO 3 crystals separated by 3 mm

  3. Oxygen ordering and superconductivity in the high Tc superconductor YBa2Cu3O6+x

    International Nuclear Information System (INIS)

    Friis Poulsen, H.

    1991-12-01

    This report contains the result of an experimental and theoretical investigation of the oxygen ordering process in the High T c superconductor Y Ba 2 Cu 3 O 6+x . Neutron scattering is used in connection with in situ monitoring of the oxygen in-diffusion in a gas-volumetric equipment. Information on the variations of the structural phases, the twin domain sizes, the elastic forces, the chemical potential og oxygen as well as diffusion are provided. Using Monte Carlo simulations we find that a simple two-dimentional lattice gas model of the oxygen ordering process, the ASYNNNI model, gives an excellent description of the vast majority of these data. A systematic study of the relationship between the static and dynamic variations of the superconducting transition temperature, T c , and the corresponding variations of the low temperature oxygen ordering process is performed. Statistics from Monte Carlo simulations based on the ASYNNNI model are combined with experimental data from the literature. The combined static and dynamic analysis makes it evident that within a charge transfer model, a linear T c versus charge transfer relationship can only be rationalized if the description is based on extended coherent ordered domains and if the dynamic co-existence between the Ortho-I and the Ortho-II type of domains inherent to the ASYNNNI model is taken into account. A minimal model is proposed, where the total charge transfer is found as a weighted sum over the areas of the Ortho-I and the Ortho-II domains, and the minimal size of the two types of domains are given by a doubling og their unit cells in both directions. (au) 5 tabs., 35 ills., 108 refs

  4. Powder processing of high Tc oxide superconductors and their properties

    International Nuclear Information System (INIS)

    Vajpei, A.C.; Upadhyaya, G.S.

    1992-01-01

    Powder processing of ceramics is an established technology and in the area of high T c superconductors, its importance is felt even more significantly. The present monograph is an attempt in this direction to explore the perspectives and practice of powder processing routes towards control and optimization of the microstructure and pertinent properties of high T c oxide superconductors. The monograph consists of 6 chapters. After a very brief introduction (Chapter 1), Chapter 2 describes various classes of high T c oxide superconductors and their phase equilibria. Chapter 3 highlights the preparation of oxide superconductor powders through various routes and details their subtle distinctions. Chapter 4 briefly covers characterisation of the oxide superconductors, laying emphasis on the process-analysis and microstructure. Chapter 5 describes in detail various fabrication techniques for bulk superconductors through the powder routes. The last Chapter (Chapter 6) describing properties of bulk oxide superconductors, discusses the role of subtituents, compositional variations and processing methods on such properties. References are given at the end of each chapter. (orig.)

  5. Degradation of superconducting Nb/NbN films by atmospheric oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Henry, Michael David; Wolfley, Steven L.; Young, Travis Ryan; Monson, Todd; Pearce, Charles Joseph; Lewis, Rupert M.; Clark, Blythe; Brunke, Lyle Brent; Missert, Nancy A.

    2017-03-01

    Niobium and niobium nitride thin films are transitioning from fundamental research toward wafer scale manufacturing with technology drivers that include superconducting circuits and electronics, optical single photon detectors, logic, and memory. Successful microfabrication requires precise control over the properties of sputtered superconducting films, including oxidation. Previous work has demonstrated the mechanism in oxidation of Nb and how film structure could have deleterious effects upon the superconducting properties. This study provides an examination of atmospheric oxidation of NbN films. By examination of the room temperature sheet resistance of NbN bulk oxidation was identified and confirmed by secondary ion mass spectrometry. As a result, Meissner magnetic measurements confirmed the bulk oxidation not observed with simple cryogenic resistivity measurements.

  6. Preparation of textured high Tc superconducting films by CVD using halides on technical substrates with appropriate buffer layers. Final report

    International Nuclear Information System (INIS)

    Selbmann, D.; Balarin, M.; Klosowski, J.

    1993-01-01

    On the basis of a thermodynamical calculation of the system Y-Ba-Cu-O-Hal-C-H, Hal = I, Br, Cl the deposition conditions of the 123-phase and the other phases in this system was investigated. For the practical applications a reaction temperature higher 850 C and an oxidizer excesse higher 5 . 10 3 is necessary in order to deposit halid- and carbon free layers. A new Aerosol-CVD-process has been developed, which allows the reproducible preparation of superconducting YBa 2 Cu 3 O 7 thin films. The process uses a solution source of Y-, Ba-, Cu-bromide dissolved in suitable organic solvents. With the process the films consisting of the 123-phase, however the content of other phases is too high. With this composition it is not possible to deposit textured layers. This behaviour is due to flow technical problems. In order to avoid the formation of oxides in the evaporator it is necessary to mix the oxidizer directly near the substrate. Therefore the development of a new reactor and a process optimization is necessary. (orig.) [de

  7. High-Tc Superconducting Thick-Film Spiral Magnet: Development and Characterization of a Single Spiral Module

    National Research Council Canada - National Science Library

    McGinnis, W

    1997-01-01

    The objective of this project was to make characterized and numerically model prototype modules of a new type of superconducting electromagnet based on stacked spirals of superconducting thick films...

  8. On the combination of the Cooper pair and the Ogg pair in the high-Tc oxide superconductor

    International Nuclear Information System (INIS)

    Zhang Liyuan.

    1991-08-01

    In this paper it is argued that the superconductivity of the high-T c oxide superconductor (HTOS) can be explained by the combinating mechanism of the Cooper pair and the Ogg pair. The properties of the superconducting state of the HTOS have been calculated under this mechanism, and the theoretical results are overall consistent with the experiment. (author). 37 refs

  9. High-Tc superconductivity near the anion height instability in Fe-based superconductors: analysis of LaFeAsO(1-x)H(x).

    Science.gov (United States)

    Onari, Seiichiro; Yamakawa, Youichi; Kontani, Hiroshi

    2014-05-09

    The isostructural transition in the tetragonal phase with a sizable change in the anion height, is realized in heavily H-doped LaFeAsO and (La,P) codoped CaFe2As2. In these compounds, the superconductivity with higher Tc (40-50 K) is realized near the isostructural transition. To find the origin of the anion-height instability and the role in realizing the higher-Tc state, we develop the orbital-spin fluctuation theory by including the vertex correction. We analyze LaFeAsO(1-x)H(x) and find that the non-nematic orbital fluctuations, which induce the anion-height instability, are automatically obtained at x∼0.5, in addition to the conventional nematic orbital fluctuations at x∼0. The non-nematic orbital order triggers the isostructural transition, and its fluctuation would be a key ingredient to realize higher-Tc superconductivity of order 50 K.

  10. Superconductivity

    CERN Document Server

    Poole, Charles P; Creswick, Richard J; Prozorov, Ruslan

    2014-01-01

    Superconductivity, Third Edition is an encyclopedic treatment of all aspects of the subject, from classic materials to fullerenes. Emphasis is on balanced coverage, with a comprehensive reference list and significant graphics from all areas of the published literature. Widely used theoretical approaches are explained in detail. Topics of special interest include high temperature superconductors, spectroscopy, critical states, transport properties, and tunneling. This book covers the whole field of superconductivity from both the theoretical and the experimental point of view. This third edition features extensive revisions throughout, and new chapters on second critical field and iron based superconductors.

  11. A manufacturing process for a mixed-oxide type superconducting material

    International Nuclear Information System (INIS)

    Gendre, P.; Regnier, P.; Schmirgeld-Mignot, L.; Marquet, A.

    1995-01-01

    In order to produce high temperature superconducting materials such as YBaCuO and Bi 2 Sr 2 Ca Cu 2 O 8 , a process is presented which consists in an electrodeposition on a conductive substrate of successive layers made of the metallic elements composing the superconductor, with only one element in each layer; between each layer deposition, an intermediary oxide-reaction thermal treatment is carried out; a global oxidation thermal treatment is then finally conducted to produce the mixed oxide material. Narrow superconducting transitions and high critical current densities are possible. 3 refs., 4 figs

  12. Redox mechanisms and superconductivity in layered copper oxides

    International Nuclear Information System (INIS)

    Raveau, B.; Michel, C.; Hervieu, M.; Provost, J.

    1992-01-01

    Redox reactions in high T c superconductors cuprates are complex and play an important role in superconductivity: oxygen non-stoichiometry is influencing the critical temperature, and rock salt layers interact with copper layers. 25 refs., 7 figs

  13. An active magnetic bearing with high Tc superconducting coils and ferromagnetic cores

    International Nuclear Information System (INIS)

    Brown, G.V.; DiRusso, E.; Provenza, A.J.

    1996-01-01

    A proof-of-feasibility demonstration showed that high-T c , superconductor (HTS) coils can be used in a high-load, active magnetic bearing in LN 2 . A homopolar radial bearing with commercially wound HTS (Bi 2223) bias and control coils produced over 890 N (200 lb) radial load capacity (measured nonrotating) and supported a shaft to 14000 rpm. The goal was to show that HTS coils can operate stably with ferromagnetic cores in a feedback controlled system at a current density similar to that for Cu in LN 2 . The bias coil, wound with nontwisted, multifilament HTS conductor, dissipated negligible power for its direct current. The control coils, wound with monofilament HTS sheathed in Ag, dissipated negligible power for direct current. AC losses increased rapidly with frequency and quadratically with AC amplitude. Above about 2 Hz, the effective resistance of the control coils exceeds that of the silver which is in electrical parallel with the oxide superconductor. These results show that twisted multifilament conductor is not needed for stable levitation but may be desired to reduce control power for sizable dynamic loads

  14. Superconductivity

    International Nuclear Information System (INIS)

    Narlikar, A.V.

    1993-01-01

    Amongst the numerous scientific discoveries that the 20th century has to its credit, superconductivity stands out as an exceptional example of having retained its original dynamism and excitement even for more than 80 years after its discovery. It has proved itself to be a rich field by continually offering frontal challenges in both research and applications. Indeed, one finds that a majority of internationally renowned condensed matter theorists, at some point of their career, have found excitement in working in this important area. Superconductivity presents a unique example of having fetched Nobel awards as many as four times to date, and yet, interestingly enough, the field still remains open for new insights and discoveries which could undeniably be of immense technological value. 1 fig

  15. Superconductivity

    International Nuclear Information System (INIS)

    Anon.

    1988-01-01

    This book profiles the research activity of 42 companies in the superconductivity field, worldwide. It forms a unique and comprehensive directory to this emerging technology. For each research site, it details the various projects in progress, analyzes the level of activity, pinpoints applications and R and D areas, reviews strategies and provides complete contact information. It lists key individuals, offers international comparisons of government funding, reviews market forecasts and development timetables and features a bibliography of selected articles on the subject

  16. Superconductivity

    International Nuclear Information System (INIS)

    Buller, L.; Carrillo, F.; Dietert, R.; Kotziapashis, A.

    1989-01-01

    Superconductors are materials which combine the property of zero electric resistance with the capability to exclude any adjacent magnetic field. This leads to many large scale applications such as the much publicized levitating train, generation of magnetic fields in MHD electric generators, and special medical diagnostic equipment. On a smaller-scale, superconductive materials could replace existing resistive connectors and decrease signal delays by reducing the RLC time constants. Thus, a computer could operate at much higher speeds, and consequently at lower power levels which would reduce the need for heat removal and allow closer spacing of circuitry. Although technical advances and proposed applications are constantly being published, it should be recognized that superconductivity is a slowly developing technology. It has taken scientists almost eighty years to learn what they now know about this material and its function. The present paper provides an overview of the historical development of superconductivity and describes some of the potential applications for this new technology as it pertains to the electronics industry

  17. Synthesis, Structure Elucidation, and Redox Properties of (superscript 99)Tc Complexes of Lacunary Wells-Dawson Polyoxometalates: Insights into Molecular (superscript 99)Tc-Metal Oxide Interactions

    International Nuclear Information System (INIS)

    McGregor, Donna; Burton-Pye, Benjamin P.; Howell, Robertha C.; Mbomekalle, Israel M.; Lukens, Wayne W. Jr.; Bian, Fang; Mausolf, Edward; Poineau, Frederic; Czerwinski, Kenneth R.; Francesconi, Lynn C.

    2011-01-01

    The isotope 99 Tc (β max , 293.7; half-life, 2.1 x 10 5 years) is an abundant product of uranium-235 fission in nuclear reactors and is present throughout the radioactive waste stored in underground tanks at the Hanford and Savannah River sites. Understanding and controlling the extensive redox chemistry of 99 Tc is important in identifying tunable strategies to separate 99 Tc from spent fuel and from waste tanks and, once separated, to identify and develop an appropriately stable waste form for 99 Tc. Polyoxometalates (POMs), nanometer-sized models for metal oxide solid-state materials, are used in this study to provide a molecular level understanding of the speciation and redox chemistry of incorporated 99 Tc. In this study, 99 Tc complexes of the (α 2 -P 2 W 17 O 61 ) 10- and (α 1 -P 2 W 17 O 61 ) 10- isomers were prepared. Ethylene glycol was used as a 'transfer ligand' to minimize the formation of TcO 2 · xH 2 O. The solution structures, formulations, and purity of TcVO(α 1 /α 2 -P 2 W 17 O 61 ) 7- were determined by multinuclear NMR. X-ray absorption spectroscopy of the complexes is in agreement with the formulation and structures determined from 31 P and 183 W NMR. Preliminary electrochemistry results are consistent with the EXAFS results, showing a facile reduction of the TcVO(α 1 -P 2 W 17 O 61 ) 7- species compared to the TcVO(α 2 -P 2 W 17 O 61 ) 7- analog. The α 1 defect is unique in that a basic oxygen atom is positioned toward the α 1 site, and the Tc V O center appears to form a dative metal-metal bond with a framework W site. These attributes may lead to the assistance of protonation events that facilitate reduction. Electrochemistry comparison shows that the ReV analogs are about 200 mV more difficult to reduce in accordance with periodic trends.

  18. Synthesis, structure elucidation and redox properties of 99Tc complexes of lacunary Wells Dawson polyoxometalates: insights into molecular 99Tc - metal oxide interactions

    International Nuclear Information System (INIS)

    McGregor, Donna; Burton-Pye, Benjamin P.; Howell, Robertha C.; Mbomekalle, Israel M.; Lukens, Wayne W. Jr; Bian, Fang; Mausolf, Edward; Poineau, Frederic; Czerwinski, Kenneth R; Francesconi, Lynn C.

    2011-01-01

    The isotope 99 Tc (β max : 250 keV, half-life: 2 x 10 5 year) is an abundant product of uranium-235 fission in nuclear reactors and is present throughout the radioactive waste stored in underground tanks at Hanford and Savannah River. Understanding and controlling the extensive redox chemistry of 99 Tc is important to identify tunable strategies to separate 99 Tc from spent fuel and from waste tanks and once separated, to identify and develop an appropriately stable waste-form for 99 Tc. Polyoxometalates (POMs), nanometer sized models for metal oxide solid-state materials, are used in this study to provide a molecular level understanding of the speciation and redox chemistry of incorporated 99 Tc. In this study, 99 Tc complexes of the (α 2 -P 2 W 17 O 61 ) 10- and (α 1 -P 2 W 17 O 61 ) 10- isomers were prepared. Ethylene glycol was used as a 'transfer ligand' to minimize the formation of TcO 2 · xH 2 O. The solution structures, formulations, and purity of Tc V O(α 1 /α 2 -P 2 W 17 O 61 ) 7- were determined by multinuclear NMR. X-ray Absorption Spectroscopy of the complexes are in agreement with the formulation and structures determined from 31 P and 183 W NMR. Preliminary electrochemistry results are consistent with the EXAFS results, showing a facile reduction of the Tc V O(α 1 -P 2 W 17 O 61 ) 7- species compared to the Tc V O(α 2 -P 2 W 17 O 61 ) 7- analog. The α 1 -defect is unique in that a basic oxygen atom is positioned toward the α 1 -site and the Tc V O center appears to form a dative metal-metal bond with a framework W site. These attributes may lead to the assistance of protonation events that facilitate reduction. Electrochemistry comparison shows that the Re V analogs are about 200 mV more difficult to reduce in accordance with periodic trends.

  19. Electrical Transport Through Tunnel Barriers and Thin Dielectric Layers and Physical Properties of the High Tc Oxide Superconductors

    Science.gov (United States)

    1990-03-26

    Josephson Tipo Emparedado con Barrera de (Nb-Si)-Amorto," PhD. Thesis, Universidad Nacional Autonoma de Mexico, May 1989. 17. E.S. Hellman, D.G...A15 Nb-Sn," Phys. Rev. B 30, p. 2590 (1984). 4. S.J. Bending, R.H. Hammond, and M.R. Beasley, "Superconductivity in the High-Tc A15 V-6a System," Bull

  20. A new way for preparing superconducting materials: the electrochemical oxidation of La2CuO4

    International Nuclear Information System (INIS)

    Wattiaux, A.; Park, J.C.; Grenier, J.C.; Pouchard, M.

    1990-01-01

    The electrochemical oxidation in alkaline medium is described as a new way for preparing superconducting oxides at room temperature. The application of this method to La 2 CuO 4 gave rise to a metallic material with a superconducting behaviour below 39 K and whose physical and chemical features appear as quite promising [fr

  1. The Electrical Aspects of the choice of Former in a High T-c Superconducting Power Cable

    DEFF Research Database (Denmark)

    Däumling, Manfred; Kühle (fratrådt), Anders Van Der Aa; Olsen, Søren Krüger

    1999-01-01

    Centrally located in a superconducting power cable the former supplies a rigid means onto which to wind the superconducting tapes and enables a continuous supply of cooling power via a flow of liquid cryogen through it. Therefore, the choice of former has a broad impact on the construction and de...

  2. Influence of multiband sign-changing superconductivity on vortex cores and vortex pinning in stoichiometric high-Tc CaKFe4As4

    Science.gov (United States)

    Fente, Antón; Meier, William R.; Kong, Tai; Kogan, Vladimir G.; Bud'ko, Sergey L.; Canfield, Paul C.; Guillamón, Isabel; Suderow, Hermann

    2018-04-01

    We use a scanning tunneling microscope to study the superconducting density of states and vortex lattice of single crystals of CaKFe4As4 . This material has a critical temperature of Tc=35 K, one of the highest among stoichiometric iron based superconductors (FeBSCs), and is comparable to Tc found near optimal doping in other FeBSCs. We observe quasiparticle scattering from defects with a pattern related to interband scattering between zone centered hole sheets. We measure the tunneling conductance in vortex cores and find a peak due to Caroli-de Gennes-Matricon bound states. The peak is located above the Fermi level, showing that CaKFe4As4 is a clean superconductor with vortex core bound states close to the so-called extreme quantum limit. We identify locations where the superconducting order parameter is strongly suppressed due to pair breaking. Vortices are pinned at these locations, and the length scale of the suppression of the order parameter is of order of the vortex core size. As a consequence, the vortex lattice is disordered up to 8 T.

  3. Superconductivity

    International Nuclear Information System (INIS)

    2007-01-01

    During 2007, a large amount of the work was centred on the ITER project and related tasks. The activities based on low-temperature superconducting (LTS) materials included the manufacture and qualification of ITER full-size conductors under relevant operating conditions, the design of conductors and magnets for the JT-60SA tokamak and the manufacture of the conductors for the European dipole facility. A preliminary study was also performed to develop a new test facility at ENEA in order to test long-length ITER or DEMO full-size conductors. Several studies on different superconducting materials were also started to create a more complete database of superconductor properties, and also for use in magnet design. In this context, an extensive measurement campaign on transport and magnetic properties was carried out on commercially available NbTi strands. Work was started on characterising MgB 2 wire and bulk samples to optimise their performance. In addition, an intense experimental study was started to clarify the effect of mechanical loads on the transport properties of multi-filamentary Nb 3 Sn strands with twisted or untwisted superconducting filaments. The experimental activity on high-temperature superconducting (HTS) materials was mainly focussed on the development and characterisation of YBa 2 Cu 3 O 7-X (YBCO) based coated conductors. Several characteristics regarding YBCO deposition, current transport performance and tape manufacture were investigated. In the framework of chemical approaches for YBCO film growth, a new method, developed in collaboration with the Technical University of Cluj-Napoca (TUCN), Romania, was studied to obtain YBCO film via chemical solution deposition, which modifies the well-assessed metallic organic deposition trifluoroacetate (MOD-TFA) approach. The results are promising in terms of critical current and film thickness values. YBCO properties in films with artificially added pinning sites were characterised in collaboration with

  4. Abrupt onset of a second energy gap at the superconducting transition of underdoped Bi2212

    Energy Technology Data Exchange (ETDEWEB)

    Hussain, Zahid; Lee, W.S.; Vishik, I.M.; Tanaka, K.; Lu, D.H.; Sasagawa, T.; Nagaosa, N.; Devereaux, T.P.; Hussain, Z.; Shen, Z.-X.

    2007-05-26

    he superconducting gap--an energy scale tied to the superconducting phenomena--opens on the Fermi surface at the superconducting transition temperature (Tc) in conventional BCS superconductors. In underdoped high-Tc superconducting copper oxides, a pseudogap (whose relation to the superconducting gap remains a mystery) develops well above Tc (refs 1, 2). Whether the pseudogap is a distinct phenomenon or the incoherent continuation of the superconducting gap above Tc is one of the central questions in high-Tc research3, 4, 5, 6, 7, 8. Although some experimental evidence suggests that the two gaps are distinct9, 10, 11, 12, 13, 14, 15, 16, 17, 18, this issue is still under intense debate. A crucial piece of evidence to firmly establish this two-gap picture is still missing: a direct and unambiguous observation of a single-particle gap tied to the superconducting transition as function of temperature. Here we report the discovery of such an energy gap in underdoped Bi2Sr2CaCu2O8+delta in the momentum space region overlooked in previous measurements. Near the diagonal of Cu?O bond direction (nodal direction), we found a gap that opens at Tc and has a canonical (BCS-like) temperature dependence accompanied by the appearance of the so-called Bogoliubov quasi-particles, a classical signature of superconductivity. This is in sharp contrast to the pseudogap near the Cu?O bond direction (antinodal region) measured in earlier experiments19, 20, 21.

  5. The Geochemical Behaviour of Tc, Np, and Pu in Spent Nuclear Fuel in an Oxidizing Environment

    Energy Technology Data Exchange (ETDEWEB)

    Buck, Edgar C.; Hanson, Brady D.; McNamara, Bruce K.; R. Giere and P. Stille

    2004-10-01

    Studies at the Nopal and Shinkolowbwe uranium deposits show that the primary uraninite (UO2) altered to a suite of secondary uranyl minerals similar to those observed in corrosion tests with uranium oxide . Although the Nopal I deposit tells us something about the possible fate of uranium, it tells us little about the likely fate of the important long-lived radionuclides; iodine (129I), cesium (135Cs), technetium (99Tc), neptunium (237Np), and plutonium (239Pu). Most performance assessment (PA) models, assume conservatively, that as the UO2 matrix corrodes, the key radionuclides (129I, 99Tc, 237Np, and 239Pu) will be released congruently. In so doing, these PA models force increased reliance on human engineered barriers.

  6. The Geochemical Behavior of Tc, Np, and Pu in Spent Nuclear Fuel in an Oxidizing Environment

    International Nuclear Information System (INIS)

    Buck, Edgar C.; Hanson, Brady D.; McNamara, Bruce K.; R. Giere; P. Stille

    2004-01-01

    Studies at the Nopal and Shinkolowbwe uranium deposits show that the primary uraninite (UO2) altered to a suite of secondary uranyl minerals similar to those observed in corrosion tests with uranium oxide . Although the Nopal I deposit tells us something about the possible fate of uranium, it tells us little about the likely fate of the important long-lived radionuclides; iodine (129I), cesium (135Cs), technetium (99Tc), neptunium (237Np), and plutonium (239Pu). Most performance assessment (PA) models, assume conservatively, that as the UO2 matrix corrodes, the key radionuclides (129I, 99Tc, 237Np, and 239Pu) will be released congruently. In so doing, these PA models force increased reliance on human engineered barriers

  7. A new quantum interferometer effect in superconducting oxide ceramics

    International Nuclear Information System (INIS)

    Chela Flores, J.; Shehata, L.N.

    1987-08-01

    On the basis of a phenomenological approach to type II high T c superconductivity, we suggest that in the lanthanum compounds the Mercereau effect for a coupled junction pair should display and ex-dependent shift in the period of modulation of the tunnelling current. (author). 14 refs

  8. Tunnelling investigation of the phonon spectrum of superconducting Be. Implications for an eventual enhancement of T(c)

    International Nuclear Information System (INIS)

    Leger, A.; Klein, J.; Cheveigne, S. de; Belin, M.; Defourneau, D.

    1975-01-01

    Beryllium is an exciting superconductor in that the theoretical upper limit for its T(c) is 140K. The possibility of increasing the critical temperature of the vapour quenched phase whose T(c) is already 9.5K is discussed. Tunnelling into films of this phase indicates that it is a weak coupling superconductor (lambda [fr

  9. On the crystal growth and chemistry of the new electron-type superconducting oxides

    Energy Technology Data Exchange (ETDEWEB)

    Tarascon, J.M.; Wang, E.; Greene, L.H.; Ramesh, R.; Bagley, B.G.; Hull, G.W.; Miceli, P.F. (Bellcore, Red Bank, NJ (USA)); Wang, Z.Z.; Brawner, D.; Ong, N.P. (Dept. of Physics, Princeton Univ., NJ (USA))

    1989-12-01

    The effect on transport and superconducting properties produced by changes in x and y in the Nd{sub 2-x}Ce{sub x}CuO{sub y} compound were studied in both polycrystalline ceramics and single crystals. Thermogravimetric analysis shows that the total oxygen content y for the as-prepared samples is always greater than 4 (i.e. presence of interstitial oxygen) whereas for the reduced sample y becomes equal to or smaller than 4 only when x is 0.15 or greater. This is the range of Ce content for which the material superconducts. For a material with Ce x=0.15 the superconducting properties can be varied reversibly by changing the oxygen content. In addition, we propose that the oxygen in these materials can be either ordered or disordered, thereby affecting the transport properties. Platelet-like crystals of Nd{sub 2-x}Ce{sub x}CuO{sub y} with x=0 to 0.18, have been grown via a flux technique. Those having a Ce content between 0.14 and 0.17 are superconducting with the sharpest transitions (Tc=21{plus minus}1K) for x=0.14. Metallic-like behavior above Tc, with a linear temperature dependence above 150K was observed on all the crystals. Below 30K, the in-plane resistivity is independent of T. The Hall coefficient is sensitive to processing conditions but is usually negative above 100K. The upper critical field with field along the c-axis is 6T at 4.2K. (orig.).

  10. Synthesis of superconducting cobalt oxyhydrates using a novel method: Electrolyzed and oxidized water

    International Nuclear Information System (INIS)

    Liu, C.-J.; Wu, T.-H.; Hsu, L.-L.; Wang, J.-S.; Chen, S.-Y.

    2007-01-01

    By deintercalation of Na + followed by inserting bilayers of water molecules into the host lattice, the layered cobalt oxide of γ-Na 0.7 CoO 2 undergoes a topotactic transformation to a layered cobalt oxyhydrate of Na 0.35 (H 2 O) 1.3 CoO 2-δ with the c-axis expanded from c ∼ 10.9 A to c ∼ 19.6 A. In this paper, we demonstrate that the superconducting phase of c ∼ 19.6 A can be directly obtained by simply immersing γ-Na 0.7 CoO 2 powders in electrolyzed/oxidized (EO) water, which is readily available from a commercial electrolyzed water generator. We found that high oxidation-reduction potential of EO water drives the oxidation of the cobalt ions accompanying by the formation of the superconductive c ∼ 19.6 A phase. Our results demonstrate how EO water can be used to oxidize the cobalt ions and hence form superconducting cobalt oxyhydrates in a clean and simple way and may provide an economic and environment-friendly route to oxidize the transition metal of complex metal oxides

  11. Synthesis of superconducting cobalt oxyhydrates using a novel method: Electrolyzed and oxidized water

    Science.gov (United States)

    Liu, Chia-Jyi; Wu, Tsung-Hsien; Hsu, Lin-Li; Wang, Jung-Sheng; Chen, Shu-Yo

    2007-09-01

    By deintercalation of Na+ followed by inserting bilayers of water molecules into the host lattice, the layered cobalt oxide of γ-Na0.7CoO2 undergoes a topotactic transformation to a layered cobalt oxyhydrate of Na0.35(H2O)1.3CoO2-δ with the c-axis expanded from c ≈ 10.9 Å to c ≈ 19.6 Å. In this paper, we demonstrate that the superconducting phase of c ≈ 19.6 Å can be directly obtained by simply immersing γ-Na0.7CoO2 powders in electrolyzed/oxidized (EO) water, which is readily available from a commercial electrolyzed water generator. We found that high oxidation-reduction potential of EO water drives the oxidation of the cobalt ions accompanying by the formation of the superconductive c ≈ 19.6 Å phase. Our results demonstrate how EO water can be used to oxidize the cobalt ions and hence form superconducting cobalt oxyhydrates in a clean and simple way and may provide an economic and environment-friendly route to oxidize the transition metal of complex metal oxides.

  12. Synthesis of superconducting cobalt oxyhydrates using a novel method: Electrolyzed and oxidized water

    Energy Technology Data Exchange (ETDEWEB)

    Liu, C.-J. [Department of Physics, National Changhua University of Education, Changhua 50007, Taiwan (China)], E-mail: liucj@cc.ncue.edu.tw; Wu, T.-H.; Hsu, L.-L.; Wang, J.-S.; Chen, S.-Y. [Department of Physics, National Changhua University of Education, Changhua 50007, Taiwan (China)

    2007-09-01

    By deintercalation of Na{sup +} followed by inserting bilayers of water molecules into the host lattice, the layered cobalt oxide of {gamma}-Na{sub 0.7}CoO{sub 2} undergoes a topotactic transformation to a layered cobalt oxyhydrate of Na{sub 0.35}(H{sub 2}O){sub 1.3}CoO{sub 2-{delta}} with the c-axis expanded from c {approx} 10.9 A to c {approx} 19.6 A. In this paper, we demonstrate that the superconducting phase of c {approx} 19.6 A can be directly obtained by simply immersing {gamma}-Na{sub 0.7}CoO{sub 2} powders in electrolyzed/oxidized (EO) water, which is readily available from a commercial electrolyzed water generator. We found that high oxidation-reduction potential of EO water drives the oxidation of the cobalt ions accompanying by the formation of the superconductive c {approx} 19.6 A phase. Our results demonstrate how EO water can be used to oxidize the cobalt ions and hence form superconducting cobalt oxyhydrates in a clean and simple way and may provide an economic and environment-friendly route to oxidize the transition metal of complex metal oxides.

  13. Emerging boom in nano magnetic particle incorporated high-Tc superconducting materials and technologies - A South African perspective

    CSIR Research Space (South Africa)

    Srinivasu, VV

    2009-01-01

    Full Text Available With a strategy to establish and embrace the emerging nano particle incorporated superconductivity technology (based on the HTS materials and nano magnetic particles) in South Africa, the author has initiated the following research activity in South...

  14. Preparation and properties of high-Tc Bi-oxide superconductors

    International Nuclear Information System (INIS)

    Maeda, H.

    1989-01-01

    Bulk superconductors of Pb-doped Bi-oxide system (BSCCO) dominated with the high-Tc phase have the critical transition temperature, Tc of 110 K, and the upper critical fields, H c2 of 140 T at OK and 60 T at 77 K. A highly dense and a highly oriented microstructure is obtained by inserting an intermediate uniaxial pressing process. The critical current density, Jc at 77 K in zero field, Jc (77K,OT) of some 5000 A/cm 2 can be easily obtained by this process, and the field dependence of Jc is also improved. Flexible high-Tc BSCCO ribbons with a Jc (77K,Ot) of 1850 A/cm 2 have been successfully prepared by the combined process of doctor blade casting, cold rolling and sintering. Aq-sheeted multifilamentary wires with 1330 filaments and tapes with 30 filaments have also been successfully fabricated and the 36-filament tape shows a Jc(77K,OT) of 1050 A/cm 2 . (Auth.). 7 refs.; 7 figs

  15. Comparative evaluation of different nanostructured metal oxides for preparation of clinically useful 99Mo/99mTc generators

    International Nuclear Information System (INIS)

    Ram, Ramu; Chakravarty, Rubel; Dash, Ashutosh

    2015-01-01

    The potential of nanostructured metal oxides such as nanotitania, nanozirconia, nanoalumina and mesoporous alumina, as new generation sorbent materials for preparation of 99 Mo/ 99m Tc generator has recently been demonstrated. A comparative assessment of such materials is essential for determination of their suitability for preparation of clinically useful generators using (n,γ) 99 Mo. Characteristics which were compared included the sorption capacity, shelf-life of the generator, radioactive concentration and purity of 99m Tc for radiopharmaceutical applications. Mesoporous alumina was identified as the most suitable sorbent for ensuring sustainable production of clinical grade 99 Mo/ 99m Tc generators using low specific activity 99 Mo. (author)

  16. Superconductivity

    Energy Technology Data Exchange (ETDEWEB)

    Batistoni, Paola; De Marco, Francesco; Pieroni, Leonardo [ed.

    2005-07-01

    Research on superconductivity at ENEA is mainly devoted to projects related to the ITER magnet system. In this framework, ENEA has been strongly involved in the design, manufacturing and test campaigns of the ITER toroidal field model coil (TFMC), which reached a world record in operating current (up to 80 kA). Further to this result, the activities in 2004 were devoted to optimising the ITER conductor performance. ENEA participated in the tasks launched by EFDA to define and produce industrial-scale advanced Nb3Sn strand to be used in manufacturing the ITER high-field central solenoid (CS) and toroidal field (TF) magnets. As well as contributing to the design of the new strand and the final conductor layout, ENEA will also perform characterisation tests, addressing in particular the influence of mechanical stress on the Nb3Sn performance. As a member of the international ITER-magnet testing group, ENEA plays a central role in the measurement campaigns and data analyses for each ITER-related conductor and coil. The next phase in the R and D of the ITER magnets will be their mechanical characterisation in order to define the fabrication route of the coils and structures. During 2004 the cryogenic measurement campaign on the Large Hadron Collider (LHC) by-pass diode stacks was completed. As the diode-test activity was the only LHC contract to be finished on schedule, the 'Centre Europeenne pour la Recherche Nucleaire' (CERN) asked ENEA to participate in an international tender for the cold check of the current leads for the LHC magnets. The contract was obtained, and during 2004, the experimental setup was designed and realised and the data acquisition system was developed. The measurement campaign was successfully started at the end of 2004 and will be completed in 2006.

  17. Generic superconducting phase behavior in high-Tc cuprates: Tc variation with hole concentration in YBa2Cu3O7-δ

    International Nuclear Information System (INIS)

    Tallon, J.L.; Bernhard, C.; Shaked, H.; Hitterman, R.L.; Jorgensen, J.D.

    1995-01-01

    A direct determination of the relationship between T c and hole concentration p for Y 1-x Ca x Ba 2 Cu 3 O 7-δ is obtained by investigating the properties of the fully oxygen-deficient (δ∼1.0) compound for which p=x/2. Measurements of T c , the thermoelectric power S, and bond-valence sums calculated from neutron-diffraction refinements for various values of x and δ allow the full determination of the relations p=p(δ), T c =T c (p), and S=S(T,p) confirming that YBa 2 Cu 3 O 7-δ satisfies the same universal relations in these quantities as the other high-T c superconducting cuprates

  18. Thermoelectric Power and Normal State of the High - Tc Copper Oxides

    International Nuclear Information System (INIS)

    Goodenough, J.B.; Zhou, J.S.; Besuker, G.I.

    1995-01-01

    The temperature dependence of the thermoelectric power and resistance for the system La 2-x Sr x CuO 4 , 0≤ x ≤0.30, are presented and interpreted. The following model emerges: (1) In the underdoped region 0 2 sheets by Sr substitution form non-adiabatic large polarons containing 6 ± 1 Cu atoms; a cooperative pseudo Jahn-Teller vibronic coupling increases the size of the polaron, but a contraction of the equilibrium Cu-O distance inside the polaron limits the size. Polaron motion occurs via a tunneling of one Cu - O bond at a time. A dynamic segregation into a hole-poor parent phase and a hole-rich superconductive phase occurs below 150K. (2) The range 0.10 2 sheet. In the polaron liquid, pairs of polarons form zig-zag polaron chains; these chains form an ordered array of alternating polaron and parent-phase stripes. Complete ordering of the stripes occurs below Tc. (4) In the overdoped region x>0.27, polaron overcrowding suppresses polaron formation; however, the vibronic coupling stabilized by the dynamic pseudo Jahn -Teller deformations persists to give unusual properties to the overdoped metallic phase. (author)

  19. Investigating superconductivity by tunneling spectroscopy using oxide heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Fillis-Tsirakis, Evangelos

    2017-06-19

    Electronic systems which are as highly-functional as the LaAlO{sub 3}/SrTiO{sub 3} interface are rare, as the emergent high-mobility two-dimensional electron system (2DES) exhibits ferromagnetism, incipient ferroelectricity, piezoelectricity, Rashba spin-orbit coupling, superconductivity and high electronic correlations; properties that may also coexist with one another. The possibility of tuning its electrical properties by external parameters such as a gate-field, temperature, pressure and magnetic-field makes the LaAlO{sub 3}/SrTiO{sub 3}-2DES the scientific analogue of a multi-tool. LaAlO{sub 3}/SrTiO{sub 3} samples were grown by pulsed-laser-deposition. Using this system, planar tunnel junctions were constructed that allowed for tunneling spectroscopy measurements. The resemblance of the LaAlO{sub 3}/SrTiO{sub 3} 2DES to the high-temperature superconductors undoubtedly adds value to the findings of this work. Further investigation of its nature has revealed that by depleting from the optimally doped region, the electron-phonon coupling strength increases and accounts for the persisting superconducting behavior within the macroscopically resistive regime at very low doping. Transport measurements at T = 50 mK were performed while tuning the carrier concentration and sweeping magnetic fields in the perpendicular-to-interface orientation, to investigate the superconductor-to-insulator transition by carrier depletion. The transition in LaAlO{sub 3}/SrTiO{sub 3}, induced by tuning the carrier concentration, has thus been characterized as a superconductor-metal-insulator transition (SMIT). One aim of these measurements was to investigate the possible existence of the ''superinsulator'' phase, identified by several authors in thin metallic films. Such a phase has not been observed during transport measurements at the LaAlO{sub 3}/SrTiO{sub 3} 2DES. The nature of superconductivity in the entire phase diagram and particularly across the SMIT has

  20. Investigating superconductivity by tunneling spectroscopy using oxide heterostructures

    International Nuclear Information System (INIS)

    Fillis-Tsirakis, Evangelos

    2017-01-01

    Electronic systems which are as highly-functional as the LaAlO 3 /SrTiO 3 interface are rare, as the emergent high-mobility two-dimensional electron system (2DES) exhibits ferromagnetism, incipient ferroelectricity, piezoelectricity, Rashba spin-orbit coupling, superconductivity and high electronic correlations; properties that may also coexist with one another. The possibility of tuning its electrical properties by external parameters such as a gate-field, temperature, pressure and magnetic-field makes the LaAlO 3 /SrTiO 3 -2DES the scientific analogue of a multi-tool. LaAlO 3 /SrTiO 3 samples were grown by pulsed-laser-deposition. Using this system, planar tunnel junctions were constructed that allowed for tunneling spectroscopy measurements. The resemblance of the LaAlO 3 /SrTiO 3 2DES to the high-temperature superconductors undoubtedly adds value to the findings of this work. Further investigation of its nature has revealed that by depleting from the optimally doped region, the electron-phonon coupling strength increases and accounts for the persisting superconducting behavior within the macroscopically resistive regime at very low doping. Transport measurements at T = 50 mK were performed while tuning the carrier concentration and sweeping magnetic fields in the perpendicular-to-interface orientation, to investigate the superconductor-to-insulator transition by carrier depletion. The transition in LaAlO 3 /SrTiO 3 , induced by tuning the carrier concentration, has thus been characterized as a superconductor-metal-insulator transition (SMIT). One aim of these measurements was to investigate the possible existence of the ''superinsulator'' phase, identified by several authors in thin metallic films. Such a phase has not been observed during transport measurements at the LaAlO 3 /SrTiO 3 2DES. The nature of superconductivity in the entire phase diagram and particularly across the SMIT has been investigated by magnetic-field-dependent tunneling

  1. Effects of graphene oxide doping on the structural and superconducting properties of YBa2Cu3O7-δ

    Science.gov (United States)

    Dadras, S.; Falahati, S.; Dehghani, S.

    2018-05-01

    In this research we reported the effects of graphene oxide (GO) doping on the structural and superconducting properties of YBa2Cu3O7-δ (YBCO) high temperature superconductors. We synthesized YBCO powder by sol-gel method. After calcination, the powder mixed with different weight percent (0, 0.1, 0.3, 0.7, 1 wt.%) of GO. Refinement of X-ray diffraction (XRD) was carried out by material analysis using diffraction (MAUD) program to obtain the structural parameters such as lattice parameters, site occupancy of different atoms and orthorhombicity value for the all samples. Results show that GO doping does not change the structure of YBCO compound, Cu (1), Cu (2) and oxygen sites occupancy. It seems that GO remains between the grains and can play the role of weak links. We found that GO addition to YBCO compound increases transition temperature (TC). The oxygen contents of the all GO-doped samples are increased with respect to the pure one. The strain (ɛ) of the samples obtained from Williamson-Hall method, varies with increasing of GO doping. The scanning electron microscopy (SEM) images of the samples show better YBCO grain connections by GO doping.

  2. Ab initio molecular-orbital study on electron correlation effects in CuO6 clusters relating to high-Tc superconductivity

    International Nuclear Information System (INIS)

    Yamamoto, S.; Yamaguchi, K.; Nasu, K.

    1990-01-01

    Ab initio molecular-orbital calculations for CuO 6 clusters have been performed to elucidate the electronic structures of undoped and doped copper oxides, which are of current interest in relation to high-T c superconductivity. The electron correlation effects for these species are thoroughly investigated by the full-valence configuration-interaction method and the complete-active-space self-consistent-field method. The electron correlation effect is relatively simple for the A g state (σ hole), whereas pair excitations and spin-flip excitations give sizable contributions to the configuration-interaction wave function for the B state (in-plane π hole). Implications of these results are discussed in relation to the mechanisms of the high-T c superconductivity

  3. Atomic Layer Epitaxy of Superconducting Oxides and Heterostructures

    National Research Council Canada - National Science Library

    Chang, R

    1998-01-01

    ...) materials and insulating metal oxides. Improving the nature of such interfaces is a crucial barrier which must be surmounted before HTS materials can be successfully incorporated on a large scale into a myriad of advanced active...

  4. Plasma oxidation of the high T/sub c/ superconducting perovskites

    International Nuclear Information System (INIS)

    Bagley, B.G.; Greene, L.H.; Tarascon, J.; Hull, G.W.

    1987-01-01

    A near room-temperature plasma oxidation process is shown to restore superconductivity and metalliclike behavior in oxygen deficient La/sub 2-//sub x/ Sr/sub x/ CuO/sub 4-//sub y/ and YBa 2 Cu 3 O/sub 7-//sub x/ compounds. In the YBa 2 Cu 3 O/sub 7-//sub x/ compound the conversion from an oxygen deficient n-type tetragonal to the p-type orthorhombic phase with a concomitant factor of 5 x 10 5 increase in room-temperature conductivity is also accomplished. This process is of technological importance because oxygen can be restored in these materials at temperatures compatible with device processing. Of scientific interest, the process allows us to carefully control the oxidation state and thereby systematically study the 90 and 55 K superconducting transitions in YBa 2 Cu 3 O/sub 7-//sub x/

  5. Structural chemistry of superconducting pnictides and pnictide oxides with layered structures

    Energy Technology Data Exchange (ETDEWEB)

    Johrendt, Dirk [Ludwig-Maximilians-Univ. Muenchen (Germany). Dept. Chemie und Biochemie; Hosono, Hideo [Tokyo Institute of Technology, Yokohama (Japan). Frontier Research Center; Hoffmann, Rolf-Dieter; Poettgen, Rainer [Muenster Univ. (Germany). Inst. fuer Anorganische und Analytische Chemie

    2011-07-01

    The basic structural chemistry of superconducting pnictides and pnictide oxides is reviewed. Crystal chemical details of selected compounds and group subgroup schemes are discussed with respect to phase transitions upon charge-density formation, the ordering of vacancies, or the ordered displacements of oxygen atoms. Furthermore, the influences of doping and solid solutions on the valence electron concentration are discussed in order to highlight the structural and electronic flexibility of these materials. (orig.)

  6. Effect of external magnetic field on superconducting and spin density wave gaps of high-Tc superconductors

    International Nuclear Information System (INIS)

    Pradhan, B.; Raj, B.K.; Rout, G.C.

    2009-01-01

    A theoretical model is addressed here to study the interplay of the superconductivity (SC) and the spin density wave (SDW) long range orders in underdoped region in the vicinity of on-set of superconductivity in presence of an external magnetic field. The order parameters are calculated by using Zubarev's technique of Green's functions and determined numerically self-consistently. The gap parameters are found to be strongly coupled to each other through their coupling constants. The interplay displays BCS type two gaps in the quasi-particle density of states (DOS) which resemble the tunneling conductance of STM experiments. The gap edges in the DOS appear at ±(z+z 1 ) and ±(z-z 1 ). The applied magnetic field further induces Zeeman splitting which is explained on the basis of spin-filter effect of tunneling experiment.

  7. Femtosecond optical detection of quasiparticle dynamics in high-Tc YBa2Cu3O7-δ superconducting thin films

    International Nuclear Information System (INIS)

    Han, S.G.; Vardeny, Z.V.; Wong, K.S.; Symko, O.G.; Koren, G.

    1990-01-01

    Femtosecond dynamics of photogenerated quasiparticles in YBa 2 Cu 3 O 7-δ superconducting thin films shows, at T≤T c , two main electronic processes: (i) quasiparticle avalanche production during hot-carrier thermalization, which takes about 300 fsec; (ii) recombination of quasiparticles to form Cooper pairs, which is completed within 5 psec. In contrastr, nonsuperconducting epitaxial films such as PrBa 2 Cu 2 O 7 and YBa 2 Cu 3 O 6 show regular picosecond electronic response

  8. The study on a new superconductor (oxide Ba-Y-Cu) with high critical temperature Tc by positron annihilation

    International Nuclear Information System (INIS)

    Zhang Caigu; Yu Zhuxing; Wang Zhu; Huang Zhe; Zhou Jun

    1987-01-01

    The study on a new superconductor oxide Ba-Y-Cu with high critical temperature Tc is described. The experimental results show that positron lifetime reducing reflects variable curve of resistance with temperature. A peak of positron lifetime is appeared at critical temperature

  9. High-temperature superconducting oxide synthesis and the chemical doping of the Cu-O planes

    International Nuclear Information System (INIS)

    Tarascon, J.M.; Barboux, P.; Bagley, B.G.; Greene, L.H.; McKinnon, W.R.; Hull, G.W.

    1987-01-01

    Different synthesis techniques for the preparation of dense superconducting ceramics are discussed, and a sol-gel process is shown to be very promising. The effect of oxygen content, and the effect of substitution of Ni and Zn for copper, on the structural, transport and superconducting properties of the La-Sr-Cu-O and Y-Ba-Cu-O systems are presented. The authors find that substitution on the copper sites destroys T/sub c/ in the La-Sr-Cu-O system and decreases it in the Y-Ba-Cu-O system, and this effect is insensitive as to whether the 3d metal is magnetic (Ni) or diamagnetic (Zn). A detailed study of the YBa/sub 2/Cu/sub 3/O/sub 7-y/ system as a function of oxygen content (y) shows that superconductivity can be destroyed in these materials by the removal of oxygen and restored by reinjecting oxygen; either thermally at 500 0 C or at temperatures (80 0 C) compatible with device processing by means of a novel plasma oxidation process. Of scientific interest, the plasma process induces bulk superconductivity in the undoped La/sub 2/CuO/sub 4/

  10. Flux Flow, Pinning, and Resistive Behavior in Superconducting Networks

    International Nuclear Information System (INIS)

    Stephen Teitel

    2005-01-01

    Numerical simulators are used to study the behavior of interacting quantized vortices and vortex lines in superconducting networks, films, and three dimensional bulk samples. An emphasis is on the explanation of the phenomenological behavior of the ''high-Tc'' copper-oxide superconductors and related model systems

  11. Ion-channeling study of anomalous atomic displacements at the superconducting transition in high-Tc materials

    International Nuclear Information System (INIS)

    Rehn, L.E.; Sharma, R.P.; Baldo, P.M.

    1991-01-01

    Ion channeling along the [001] direction in high-quality single crystals of (Y/Er)Ba 2 Cu 3 O 7-x revealed an abrupt change in displace-ments in the a-b plane of the Cu and O atoms at the superconducting transition, T c ; normal 'Debye-like' vibrations were found for the Y/Er and Ba atoms. The anomalous change in Cu-O displacements was found to shift directly with stoichiometry-induced changes in T c , implying a direct link between the observed phonon anomaly and the superconducting transition. Recent measurements of ion-channeling along the [001] axis in (Bi 1.7 Pb 0.3 )Sr 2 Ca 1 Cu 2 O x single-crystals revealed a similar change at T c , suggesting that this phonon anomaly is a general feature of high-T c superconductivity. In order to identify more specifically the crystallographic directions and displacement amplitudes associated with the anomalous phonon behavior, axial channeling scans using RBS, as well as characteristic x-ray production, were taken at several temperatures between 30 and 300K along the [301] and [331] directions of YBa 2 Cu 3 O 7-x single crystals. Twins present in the specimens, and the existing static atomic displacements present along these directions, caused the channeling to be poorer along these axes compared to the (001) direction. Also, a much stronger dependence of the minimum yield on depth was observed. However, since only one twin variant generally dominated over sufficiently wide areas of the specimens, reasonably good (approx 10 percent) minimum yields could be obtained along the appropriate [331] axis, and detwinned crystals produced good results along [301]. (author). 27 refs.; 5 figs

  12. Impact of cool-down conditions at T_{c} on the superconducting rf cavity quality factor

    Directory of Open Access Journals (Sweden)

    J.-M. Vogt

    2013-10-01

    Full Text Available Many next-generation, high-gradient accelerator applications, from energy-recovery linacs to accelerator-driven systems (ADS rely on continuous wave (CW operation for which superconducting radio-frequency (SRF systems are the enabling technology. However, while SRF cavities dissipate little power, they must be cooled by liquid helium and for many CW accelerators the complexity as well as the investment and operating costs of the cryoplant can prove to be prohibitive. We investigated ways to reduce the dynamic losses by improving the residual resistance (R_{res} of niobium cavities. Both the material treatment and the magnetic shielding are known to have an impact. In addition, we found that R_{res} can be reduced significantly when the cool-down conditions during the superconducting phase transition of the niobium are optimized. We believe that not only do the cool-down conditions impact the level to which external magnetic flux is trapped in the cavity but also that thermoelectric currents are generated which in turn create additional flux that can be trapped. Therefore, we investigated the generation of flux and the dynamics of flux trapping and release in a simple model niobium-titanium system that mimics an SRF cavity in its helium tank. We indeed found that thermal gradients along the system during the superconducting transition can generate a thermoelectric current and magnetic flux, which subsequently can be trapped. These effects may explain the observed variation of the cavity’s R_{res} with cool-down conditions.

  13. High-pressure effects on the superconductivity of β-pyrochlore oxides AOs2O6

    International Nuclear Information System (INIS)

    Muramatsu, Takaki; Takeshita, Nao; Terakura, Chikeko; Takagi, Hidenori; Tokura, Yoshinori; Yonezawa, Shigeki; Muraoka, Yuji; Hiroi, Zenji

    2006-01-01

    High-pressure effects on the superconducting transitions of β-pyrochlore oxide superconductors AOs 2 O 6 (A=Cs, Rb, K) are studied by measuring resistivity under high pressures up to 16 GPa. The superconducting transition temperature T c first increases with increasing pressure in all the compounds and then exhibits a broad maximum at 7.6 K (6 GPa), 8.2 K (2 GPa) and 10 K (0.6 GPa) for A=Cs, Rb and K, respectively. Finally, the superconductivity is suppressed completely at a critical pressure near 7 and 6 GPa for A=Rb and K and probably above 10 GPa for A=Cs. Characteristic changes in the temperature dependence of resistivity of RbOs 2 O 6 under high pressure. The residual resistivity largely increases with pressure above 4 GPa and, as a result, resistivity indicates small temperature dependence down to 4.2 K at 7 GPa and application of further pressure up to 10 GPa indicates that temperature dependence of resistivity decrease below 100 K. This characteristic behavior in the β-pyrochlore oxides may originate from the nesting of nearly octahedron shape of Fermi surface

  14. Simulation of Field Dependence of Critical Current Densities of Bulk High Tc Superconducting Materials regarding Thermally Activated Flux Motion

    Science.gov (United States)

    Santosh, M.; Naik, S. Pavan Kumar; Koblischka, M. R.

    2017-07-01

    In the upcoming generation, bulk high temperature superconductors (HTS) will play a crucial and a promising role in numerous industrial applications ranging from Maglev trains to magnetic resonance imaging, etc. Especially, the bulk HTS as permanent magnets are suitable due to the fact that they can trap magnetic fields being several orders of magnitude higher than those of the best hard ferromagnets. The bulk HTS LREBa2Cu3O7-δ (LREBCO or LRE-123, LRE: Y, Gd, etc.,) materials could obtain very powerful compact superconducting super-magnets, which can be operated at the cheaper liquid nitrogen temperature or below due to higher critical temperatures (i.e., ∼90 K). As a result, the new advanced technology can be utilized in a more attractive manner for a variety of technological and medical applications which have the capacity to revolutionize the field. An understanding of the magnetic field dependence of the critical current density (J c(H)) is important to develop better adapted materials. To achieve this goal, a variety of Jc (H) behaviours of bulk LREBCO samples were modelled regarding thermally activated flux motion. In essence, the Jc (H) curves follows a certain criterion where an exponential model is applied. However, to fit the complete Jc (H) curve of the LRE-123 samples an unique model is necessary to explain the behavior at low and high fields. The modelling of the various superconducting materials could be understood in terms of the pinning mechanisms.

  15. Splitting of the resistive transition of copper oxide superconductors: Intrinsic double superconducting transitions versus extrinsic effects

    International Nuclear Information System (INIS)

    Pomar, A.; Curras, S.R.; Veira, J.A.; Vidal, F.

    1996-01-01

    To prove the possible existence of an intrinsic double superconducting transition in the high-temperature copper oxide superconductors (HTSC), an effect recently attributed by various groups to different intrinsic properties of these materials (including unconventional wave pairing), we present in this paper high resolution data of the electrical resistivity, ρ(T), around the superconducting transition of different single crystal and polycrystal YBa 2 Cu 3 O 7-δ samples. The analysis of the temperature derivative of these ρ(T) data strongly suggests that (i) with a temperature resolution well to within 20 mK, the intrinsic resistive transition of the HTSC does not present any double transition anomaly and (ii) the double peak structure observed in dρ(T)/dT by some authors is probably an extrinsic effect (associated with stoichiometric inhomogeneities in some cases, and with experimental artifacts in other cases). copyright 1996 The American Physical Society

  16. Moessbauer studies of 57Fe substitution of Cu ions in superconducting oxides

    International Nuclear Information System (INIS)

    Saitovitch, E.B.

    1988-01-01

    Since the discovery of high-T c superconductivity in YBa 2 Cu 3 O 7 oxides several studies of metal ions substitutions were reported. The observed depression on T c without a systematic correlation with the charge and magnetic moment of Cu substituents claims for more detailed information about its local properties as can be revealed by 57 Fe Moessbauer spectroscopy. The results for different iron concentrations combined with modifications of the superconducting transition are discussed concerning the presence of magnetic moments on the Fe ions and the preferential occupation of Cu(1) sites, recently confirmed by neutron and electron diffraction experiments. The oxygen coordination for the different iron species are proposed on the basis of their dependence on Fe concentration, their behavior at high temperatures as well as the electron diffraction and electron microscopy measurements reported for Fe: YBa 2 Cu 3 O 7 samples. (author) [pt

  17. Crystalline phases and electronic structures in superconducting Bi endash Sr endash Ca endash Cu oxides

    International Nuclear Information System (INIS)

    Giardina, M.D.; Feduzi, R.; Inzaghi, D.; Manara, A.; Giori, C.; Sora, I.N.; Dallacasa, V.

    1997-01-01

    Two classes of samples, designated A and B, of layered Bi endash Sr endash Ca endash Cu oxides having the same nominal composition 4:3:3:4, but different thermal histories, were investigated by using field modulated microwave absorption (ESR), powder x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), and x-ray absorption near the edge structure (XANES). Previous electrical resistivity measurements showed that the B samples only presented two superconducting phases with midpoints of the transition temperatures at ∼80K and ∼105K. The microwave absorption technique indicated instead the presence of islands which became superconducting at the above-mentioned temperatures also in the A samples. The crystalline and electronic structures of the two types of samples are illustrated and discussed. A plausible theoretical interpretation of the experimental results, based on a quantum percolation model with Coulomb interaction, is also given. copyright 1997 Materials Research Society

  18. Improving superconducting properties of YBCO high temperature superconductor by Graphene Oxide doping

    Energy Technology Data Exchange (ETDEWEB)

    Dadras, S., E-mail: dadras@alzahra.ac.ir; Dehghani, S.; Davoudiniya, M.; Falahati, S.

    2017-06-01

    In this research, we report the synthesis and characterization of YBa{sub 2}Cu{sub 3}O{sub 7-δ} (YBCO) high temperature superconductor prepared by sol-gel method and doped with Graphene Oxide (GO) in different weight percentages, 0, 0.1, 0.7 and 1 % wt. The x-ray diffraction (XRD) analysis confirms the formation of orthorhombic phase of superconductivity for all the prepared samples. We found that GO doping reduces the crystalline size of the samples. We evaluated the effects of GO doping on the normal state resistivity (ρ), superconducting transition temperature (T{sub c}) and critical current density (J{sub c}). The results show that the GO doping has a positive effect on these properties. Also, the highest J{sub c} is obtained for the 0.7 %wt GO doped YBCO compound that its critical current density is about 15 times more than the J{sub c} of pure one in 0.4 T magnetic field. The scanning electron microscope (SEM) analysis shows that there are better connections between the grains of GO doped samples. - Highlights: • Graphene Oxide doping increased the YBCO critical current density. • Graphene Oxide creates a better connection between the YBCO grains. • The normal resistivity of samples were decreased by GO doping to YBCO compounds. • Graphene Oxide doping has a positive effect on the critical transition temperature.

  19. Evolution of magnetic and superconducting fluctuations with doping of high-Tc superconductors. An electronic Raman scattering study

    International Nuclear Information System (INIS)

    Blumberg, G.

    1998-01-01

    For YBa 2 Cu 3 O 6+δ and Bi 2 Sr 2 CaCu 2 O 3±δ superconductors, electronic Raman scattering from high- and low-energy excitations has been studied in relation to the hole doping level, temperature, and energy of the incident photons. For underdoped superconductors, it is concluded that short range antiferromagnetic (AF) correlations persist with hole doping and doped single holes are incoherent in the AF environment. Above the superconducting (SC) transition temperature T c the system exhibits a sharp Raman resonance of B 1g symmetry and about 75 meV energy and a pseudogap for electron-hole excitations below 75 meV, a manifestation of a partially coherent state forming from doped incoherent quasi-particles. The occupancy of the coherent state increases with cooling until phase ordering at T c produces a global SC state

  20. Spin dynamics in the metallic state of the high Tc superconducting system YBa2Cu3O6+x

    International Nuclear Information System (INIS)

    Bourges, P.; Sidis, Y.; Regnault, L.P.; Henry, J.Y.; Burlet, P.

    1994-01-01

    The spin dynamics in single-crystals of YBa 2 Cu 3 O 6+x has been successfully investigated, by inelastic neutron scattering (INS) experiments, as a function of temperature in the metallic state over the whole doping range from the weakly-doped to the heavily-doped and the over-doped regimes. Dynamical AF-correlations persist in all the metallic states. The imaginary part of the magnetic susceptibility, χ '' , consists of two contributions which have different doping and temperature dependences. At low temperature, χ '' exhibits an energy gap in any superconducting samples which becomes much weaker close to the insulating-metallic transition. To emphasize the characteristic features of the spin dynamics in YBCO, INS results obtained elsewhere are compared with the experiments. Several theoretical approaches, which intend to describe the energy lineshape of the dynamical magnetic susceptibility, are also discussed. (authors). 6 figs., 51 refs

  1. Composite superconducting wires produced by rapid coating in Bi-Sr-Ca-Cu-O metal oxide system

    International Nuclear Information System (INIS)

    Grozav, A.D.; Konopko, L.A.; Leoporda, N.I.

    1989-01-01

    Method for producing superconducting composite wires by dip coating of copper wires in metal-oxide BiSrCaCu 2 O x melt is developed. The thickness of the coating is regulated by the change of dip rate, melt viscosity and by the number of passages through the melt. Wire annealing at 700-800 deg C leads to the production of two phases, one of them being superconducting with T c =80K

  2. Simple method for resistance measurements on thin films and bulk of high T_c superconducting materials

    Science.gov (United States)

    Alzetta, G.; Arimondo, E.; Celli, R. M.; Fuso, F.

    1994-08-01

    Two experimental techniques for measuring resistivity behaviour of high T_c ceramic superconductors in bulk or thin films are described. Particular attention has been given to the development of a four point contact system, easy to use for reliable resistance measurements under repeated, wide thermal cycles. On expose deux méthodes de mesure de la résistivité des supraconducteurs HTc en forme de couches minces déposées sur un substrat ou des céramiques frittées. Le dispositif de mesure, qui a été réalisé avec quatre contacts élastiques, permet d'obtenir des résultats reproductibles dans de très larges intervalles de température.

  3. Silica-gel modified with zirconium oxide as a novel 99Mo adsorbent 99mTc generators

    International Nuclear Information System (INIS)

    Salehi, H.; Mollarazi, E.; Abbasi, H.

    2010-01-01

    A new 99 Mo adsorbent has been prepared with modified silica gel with zirconium oxide (SiO 2 /ZrO 2 :Na 2 MoO 4 ) and used in technetium-99m generator. The adsorption behaviors of 99 Mo in the form of molybdate and 99m Tc in the form of pertechnetate on the new adsorbent was investigated showed that the adsorption capacity of molybdate on this generator was considerably higher than the usual generator with alumina column. Coating zirconium oxide on the surface of silica gel resulted in higher 99 Mo adsorption of this compound. 99m Tc is eluted with 0.9% NaCl, and the radionuclidic, radiochemical and chemical purities of the eluate were checked. This generator has a great potential as compared to the traditional alumina generators.

  4. Alternating current loss calculation in a high-TC superconducting transmission cable considering the magnetic field distribution

    International Nuclear Information System (INIS)

    Noji, H; Haji, K; Hamada, T

    2003-01-01

    We have calculated the alternating current (ac) losses of a 114 MVA high-T C superconducting (HTS) transmission cable using an electric-circuit (EC) model. The HTS cable is fabricated by Tokyo Electric Power Company and Sumitomo Electric Industries, Ltd. The EC model is comprised of a resistive part and an inductive part. The resistive part is obtained by the approximated Norris equation for a HTS tape. The Norris equation indicates hysteresis losses due to self-fields. The inductive part has two components, i.e. inductances related to axial fields and those related to circumferential fields. The layer currents and applied fields of each layer were calculated by the EC model. By using both values, the ac losses of the one-phase HTS cable were obtained by calculation considering the self-field, the axial field and the circumferential field of the HTS tape. The measured ac loss transporting 1 kA rms is 0.7 W m -1 ph -1 , which is equal to the calculation. The distribution of each layer loss resembles in shape the distribution of the circumferential field in each layer, which indicates that the circumferential fields strongly influence the ac losses of the HTS cable

  5. Lanthanide gallate perovskite-type substrates for epitaxial, high-Tc superconducting Ba2YCu3O7-δ films

    International Nuclear Information System (INIS)

    Giess, E.A.; Sandstrom, R.L.; Gallagher, W.J.; Gupta, A.; Shinde, S.L.; Cook, R.F.; Cooper, E.L.; O'Sullivan, E.M.J.; Roldan, J.M.; Segmuller, A.D.; Angilello, J.

    1990-01-01

    This paper reports on the use of lanthanide gallate perovskite-type substrates for the deposition of epitaxial, high-T c superconducting Ba 2 YCu 3 O 7-δ (BYCO) films. They were also found to have moderate dielectric constants (∼25 compared to ∼ 277 for SrTiO 3 ). This study was undertaken to further explore the use of LaGaO 3 , NdGaO 3 , SrTiO 3 , MgO, and Y-stabilized ZrO 2 substrates, prepared from single-crystal joules grown by several suppliers using the Czochralski method. Films were prepared by cylindrical magnetron sputtering and laser ablation. Substrate evaluations included measurement of dielectric constant and loss, thermal expansion, and mechanical hardness and toughness. In addition to their moderate dielectric constants, they were found to have satisfactory mechanical properties, except for the twinning tendency of LaGaO 3 . Lattice mismatch strains were calculated for orthorhombic BYCO films on a number of substrates. NdGaO 3 was found to have the best lattice match with BYCO, and is now available twin-free

  6. Linearity of high-Tc dc superconducting quantum interference device operated in a flux-locked loop

    International Nuclear Information System (INIS)

    Nichols, D.G.; Dantsker, E.; Kleiner, R.; Mueck, M.; Clarke, J.

    1996-01-01

    Measurements have been made of the linearity of a high transition temperature dc superconducting quantum interference device (SQUID) operated at 77 K with 130 kHz flux modulation in a flux-locked loop. The degree of nonlinearity was determined from harmonic generation. A sinusoidal magnetic flux with harmonic content less than -130 dB was applied to the SQUID, which was cooled in a magnetic field below 10 -7 T, and the harmonics at the output of the flux-locked loop were measured with a spectrum analyzer. For input signals at frequencies up to 248 Hz and amplitudes up to 20Φ 0 rms (Φ 0 is the flux quantum), the second, third, and fourth harmonics were each at least 115 dB below the fundamental. At higher frequencies the harmonic content began to increase because of the reduction in the open-loop gain of the flux-locked loop. The magnitude of the harmonics was not measurably changed when the SQUID was cooled in a field of 100 μT. The amplitudes of the even harmonics depended critically on the amplitude of the 130 kHz flux modulation, and became zero when its peak-to-peak value was precisely Φ 0 /2. copyright 1996 American Institute of Physics

  7. High-efficiency and low-cost permanent magnet guideway consideration for high-Tc superconducting Maglev vehicle practical application

    International Nuclear Information System (INIS)

    Deng, Z; Wang, J; Zheng, J; Jing, H; Lu, Y; Ma, G; Liu, L; Liu, W; Zhang, Y; Wang, S

    2008-01-01

    In order to improve the cost performance of the present high-T c superconducting (HTS) Maglev vehicle system for practical application, the multi-pole permanent magnet guideway (PMG) concept was introduced. A well-known double-pole Halbach PMG was chosen as a representative of multi-pole PMGs to compare with traditional monopole PMGs from the point of view of levitation efficiency and cost. Experimental results show that YBCO bulks above the double-pole Halbach PMG can exhibit better load capability and guidance performance as well as dynamics stability at the applied working height between the bulk HTSC and the PMG due to a more reasonable magnetic field distribution at the working range of bulk HTSC. Furthermore, the double-pole PMG configuration can play a more important role in improving guidance performance due to the potential-well field configuration. By comparing with former 'century' PMGs, the double-pole Halbach PMG shows another remarkable advantage in reducing the cost of levitation. As another necessary issue, magnetic field homogeneity and the corresponding magnetic drag force of a double-pole Halbach PMG has been considered by experiment in spite of the above highlights. Synthetically, the multi-pole Halbach PMG design is concluded to be one important choice for future HTS Maglev vehicle applications because of its high efficiency and low cost.

  8. Anisotrophic currents and flux jumps in high-Tc superconducting films with self-organized arrays of planar defects

    International Nuclear Information System (INIS)

    Yurchenko, V.V.; Qviller, A.J.; Mozhaev, P.B.; Mozhaeva, J.E.; Hansen, J.B.; Jacobsen, C.S.; Kotelyanskii, I.M.; Pan, A.V.; Johansen, T.H.

    2010-01-01

    Regular arrays of planar defects with a period of a few nanometers can be introduced in superconducting YBa 2 Cu 3 O 7-δ (YBCO) thin films by depositing them on vicinal (also called miscut or tilted) substrates. This results in the anisotropy of critical currents flowing in the plane of the film. We present results of real-time magneto-optical imaging (MOI) of magnetic flux distribution and dynamics in a series of YBCO thin films deposited on NdGaO 3 substrates with different miscut angles θ. MOI allows reconstructing the current flow profiles. From the angle formed between domains with different directions of the current flow we determine the anisotropy parameter of the in-plane current, as well as its field and temperature dependences. The artificially introduced defects also have a dramatic effect on the dynamics of the flux propagation: for 10 o o the magnetic flux propagates along the easy channels intermittently, i.e. in a form of flux jumps. This behavior is indicative of thermo-magnetic instability in superconductors, but we argue that this effect can be of a different nature.

  9. Experimental study of {sup 99m}Tc-aluminum oxide use for sentinel lymph nodes detection

    Energy Technology Data Exchange (ETDEWEB)

    Chernov, V. I., E-mail: Chernov@oncology.tomsk.ru; Sinilkin, I. G.; Zelchan, R. V.; Medvedeva, A. A. [Tomsk Cancer Research Institute, Kooperativny Street 5, Tomsk, 634050 (Russian Federation); Tomsk Polytechnic University, Lenin Avenue 30, Tomsk, 634050 (Russian Federation); Lyapunov, A. Yu., E-mail: Lyapunov1720.90@mail.ru [Tomsk Cancer Research Institute, Kooperativny Street 5, Tomsk, 634050 (Russian Federation); Bragina, O. D.; Varlamova, N. V.; Skuridin, V. S. [Tomsk Polytechnic University, Lenin Avenue 30, Tomsk, 634050 (Russian Federation)

    2016-08-02

    The purpose of the study was a comparative research in the possibility of using the radiopharmaceuticals {sup 99m}Tc-Al{sub 2}O{sub 3} and {sup 99m}Tc-Nanocis for visualizing sentinel lymph nodes. The measurement of the sizes of {sup 99m}Tc-Al{sub 2}O{sub 3} and {sup 99m}Tc-Nanocis colloidal particles was performed in seven series of radiopharmaceuticals. The pharmacokinetics of {sup 99m}Tc-Al{sub 2}O{sub 3} and {sup 99m}Tc-Nanocis was researched on 50 white male rats. The possibility of the use of {sup 99m}Tc-Al{sub 2}O{sub 3} and {sup 99m}Tc-Nanocis for lymphoscintigraphy was studied in the experiments on 12 white male rats. The average dynamic diameter of the sol particle was 52–77 nm for {sup 99m}Tc-Al{sub 2}O{sub 3} and 16.7–24.5 nm for {sup 99m}Tc-Nanocis. Radiopharmaceuticals accumulated in the inguinal lymph node in 1 hour after administration; the average uptake of {sup 99}mTc-Al{sub 2}O{sub 3} was 8.6% in it, and the accumulation of {sup 99m}Tc-Nanocis was significantly lower—1.8% (p < 0.05). In all study points the average uptake of {sup 99m}Tc-Al{sub 2}O{sub 3} in the lymph node was significantly higher than {sup 99m}Tc-Nanocis accumulation. The results of dynamic scintigraphic studies in rats showed that {sup 99m}Tc-Al{sub 2}O{sub 3} and {sup 99m}Tc-Nanocis actively accumulated into the lymphatic system. By using {sup 99m}Tc-Al{sub 2}O{sub 3} inguinal lymph node was determined in 5 minutes after injection and clearly visualized in all the animals in the 15th minute, when the accumulation became more than 1% of the administered dose. Further observation indicated that the {sup 99m}Tc-Al{sub 2}O{sub 3} accumulation reached a plateau in a lymph node (average 10.5%) during 2-hour study and then its accumulation remained practically at the same level, slightly increasing to 12% in 24 hours. In case of {sup 99m}Tc-Nanocis inguinal lymph node was visualized in all animals for 15 min when it was accumulated on the average 1.03% of the administered dose

  10. Influence of ion beam mixing on the growth of high temperature oxide superconducting thin film

    International Nuclear Information System (INIS)

    Bordes, N.; Rollett, A.D.; Cohen, M.R.; Nastasi, M.

    1989-01-01

    The superconducting properties of high temperature superconductor thin films are dependent on the quality of the substrate used to grow these films. In order to maximize the lattice matching between the superconducting film and the substrate, we have used a YBa 2 Cu 3 O 7 thin film deposited on left-angle 100 right-angle SrTiO 3 as a template. The first film was prepared by coevaporation of Y, BaF 2 and Cu on left-angle 100 right-angle SrTiO 3 , followed by an anneal in ''wet'' oxygen at 850 degree C. This film showed a sharp transition at about 90 K. A thicker layer of about 5000 A was then deposited on top of this first 2000 angstrom film, using the same procedure. After the post anneal at 850 degree C, the transition took place at 80 K and no epitaxy of the second film was observed. Ion beam mixing at 400 degree C, using 400 keV O ions was done at the interface of the two films (the second one being not annealed). After the post anneal, the film displayed an improved Tc at 90K. Moreover, epitaxy was shown to take place from the interface SrTiO 3 -123 film towards the surface and was dependent of the dose. These results will be discussed from the data obtained from Rutherford backscattering spectroscopy (RBS) combined with channeling experiments, x-ray diffraction (XRD) and scanning electron microscopy (SEM) observations. 8 refs., 2 figs., 2 tabs

  11. Characterization of transparent superconductivity Fe-doped CuCrO{sub 2} delafossite oxide

    Energy Technology Data Exchange (ETDEWEB)

    Taddee, Chutirat [Materials Science and Nanotechnology Program, Faculty of Science, Khon Kaen University, Khon Kaen 40002 (Thailand); Kamwanna, Teerasak, E-mail: teekam@kku.ac.th [Department of Physics, Faculty of Science, Khon Kaen University, Khon Kaen 40002 (Thailand); Nanotec-KKU Center of Excellence on Advanced Nanomaterials for Energy Production and Storage, Khon Kaen 40002 (Thailand); Integrated Nanotechnology Research Center (INRC), Khon Kaen University, Khon Kaen 40002 (Thailand); Amornkitbamrung, Vittaya [Department of Physics, Faculty of Science, Khon Kaen University, Khon Kaen 40002 (Thailand); Nanotec-KKU Center of Excellence on Advanced Nanomaterials for Energy Production and Storage, Khon Kaen 40002 (Thailand); Integrated Nanotechnology Research Center (INRC), Khon Kaen University, Khon Kaen 40002 (Thailand)

    2016-09-01

    Graphical abstract: - Highlights: • Effect of Fe substitution on the physical properties in CuCrO{sub 2} is studied. • The substitution of Cr{sup 3+} by Fe{sup 3+} produces a mixed effect on the magnetic properties. • CuCr{sub 1−x}Fe{sub x}O{sub 2} delafossite oxides show transparent superconductivity. - Abstract: Delafossite CuCr{sub 1−x}Fe{sub x}O{sub 2} (0.0 ≤ x ≤ 0.15) semiconductors were synthesized using a self-combustion urea nitrate process. The effects of Fe concentration on its microstructural, optical, magnetic, and electrical properties were investigated. X-ray diffraction (XRD) analysis results revealed the delafossite structure in all the samples. The lattice spacing of CuCr{sub 1−x}Fe{sub x}O{sub 2} slightly increased with increasing substitution of Fe at the Cr sites. The optical properties measured at room temperature using UV–visible spectroscopy showed a weak absorbability in the visible light and near IR regions. The corresponding direct optical band gap was about 3.61 eV, exhibiting transparency in the visible region. The magnetic hysteresis loop measurements showed that the Fe-doped CuCrO{sub 2} samples exhibited ferromagnetic behavior at room temperature. This indicated that the substitution of Fe{sup 3+} for Cr{sup 3+} produced a mixed effect on the magnetic properties of CuCrO{sub 2} delafossite oxide. The temperature dependent resistivity measurements clearly revealed the presence of superconductivity in the CuCr{sub 1−x}Fe{sub x}O{sub 2} with a superconducting transition up to 118 K.

  12. Spectroscopic Imaging Scanning Tunneling Microscopy Studies of Electronic Structure in the Superconducting and Pseudogap Phases of Cuprate High-Tc Superconductors

    Science.gov (United States)

    Fujita, Kazuhiro; Schmidt, Andrew R.; Kim, Eun-Ah; Lawler, Michael J.; Lee, Dung Hai; Davis, J. C.; Eisaki, Hiroshi; Uchida, Shin-ichi

    2012-01-01

    phase diagram and the mechanism of high-Tc superconductivity, represents one of a key challenges for cuprate studies.

  13. Superconducting materials

    International Nuclear Information System (INIS)

    Kormann, R.; Loiseau, R.; Marcilhac, B.

    1989-01-01

    The invention concerns superconducting ceramics containing essentially barium, calcium and copper fluorinated oxides with close offset and onset temperatures around 97 K and 100 K and containing neither Y nor rare earth [fr

  14. High-Tc copper oxide superconductors and related novel materials dedicated to prof K. A. Müller on the occasion of his 90th birthday

    CERN Document Server

    Keller, Hugo; Bianconi, Antonio

    2017-01-01

    Authored by many of the world's leading experts on high-Tc superconductivity, this volume presents a panorama of ongoing research in the field, as well as insights into related multifunctional materials. The contributions cover many different and complementary aspects of the physics and materials challenges, with an emphasis on superconducting materials that have emerged since the discovery of the cuprate superconductors, for example pnictides, MgB2, H2S and other hydrides. Special attention is also paid to interface superconductivity. In addition to superconductors, the volume also addresses materials related to polar and multifunctional ground states, another class of materials that owes its discovery to Prof. Müller's ground-breaking research on SrTiO3.

  15. Solid-state ionics: Studies of lithium-conducting sulfide glasses and a superconducting oxide compound

    International Nuclear Information System (INIS)

    Ahn, Byung Tae.

    1989-01-01

    The first part of this work studies lithium-conducting sulfide glasses for battery applications, while the second part studies the thermodynamic properties of a superconducting oxide compound by using an oxide electrolyte. Lithium conducting glasses based on the SiS 2 -Li 2 S system are possible solid electrolytes for high-energy-density lithium batteries. The foremost requirement for solid electrolytes is that they should have high ionic conductivities. Unfortunately, most crystalline lithium conductors have low ionic conductivities at room temperature. However, glass ionic conductors show higher ionic conductivities than do crystalline forms of the same material. In addition to higher ionic conductivities, glasses appear to have several advantages over crystalline materials. These advantages include isotropic conductivity, absence of grain boundary effects, ease of glass forming, and the potential for a wide range of stability to oxidizing and reducing conditions. Using pyrolitic graphite-coated quartz ampoules, new ternary compounds and glasses in the SiS 2 -Li 2 S system were prepared. Several techniques were used to characterize the materials: powder x-ray diffraction, differential thermal analysis, differential scanning calorimetry, and AC impedance spectroscopy. The measured lithium conductivity of the sulfide glasses was one of the highest among the known solid lithium conductors. Measuring the equilibrium open circuit voltages assisted in determining the electrochemical stabilities of the ternary compounds and glasses with respect to pure Li. A solid-state ionic technique called oxygen coulometric titration was used to measure the thermodynamic stability, the oxygen stoichiometry, and the effects of the oxygen stoichiometry, and the effects of the oxygen stoichiometry and the cooling rate on superconductivity of the YBa 2 Cu 3 O 7-x compound were investigated

  16. Oxygen hole mechanism of superconductivity in cuprates and other metal oxides

    International Nuclear Information System (INIS)

    Rao, C.N.R.

    1989-01-01

    Several theoretical models have been proposed to explain high-temperature superconductivity in cuprates. An issue that is central to any model is the nature of copper and oxygen species in the cuprates since superconductivity clearly owes its origin to the Cu-O sheets universally present in all the cuprate families. Thus, the five families of cuprate superconductors, La 2 - x M x CuO 4 (M = Ca, Sr or Ba) of the K 2 NiF 4 structure, LnBa 2 Cu 3 O 7 - δ (Ln = Y or rare earth), Bi 2 (Ca, Sr) n + 1 Cu n O 2n + 4 , Tl 2 (Ca, Ba) n + 1 Cu n O 2n + 4 and Tl (Ca, Ba) n + 1 Cu n O 2n + 3 , all contain two-dimensional Cu-O sheets. The Cu-O chains additionally present in the 123 compounds do not seem to play any crucial role. It has been generally believed that magnetic, superconducting and related properties of cuprates have some thing to do with the mixed valency of copper. For example, the resonating valence bond (RVB) model requires the presence of holes on Cu sites (Cu 3 + species). There are also a few models, however, based on the presence of holes on oxygen sites (O - species); dimerization of oxygen holes has also been suggested to occur by a few workers. It is the purpose of this article to briefly present the available experimental evidence for the presence of oxygen holes and to discuss their role in high-temperature conductivity. It will be shown that these holes play a role in other oxide materials as well as including the Cu-free Ba 1 - x K x BiO 3 superconductor

  17. Introducing Barium in Transition Metal Oxide Frameworks: Impact upon Superconductivity, Magnetism, Multiferroism and Oxygen Diffusion and Storage.

    Science.gov (United States)

    Raveau, Bernard

    2017-06-01

    The role of barium in the structural chemistry of some transition metal oxides of the series "Cu, Mn, Fe,Co" is reviewed, based on its size effect and its particular chemical bonding. Its impact upon various properties, superconductivity, magnetism, multiferroism, oxygen storage is emphasized. © 2017 The Chemical Society of Japan & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. High-temperature superconductivity

    International Nuclear Information System (INIS)

    Ginzburg, V.L.

    1987-07-01

    After a short account of the history of experimental studies on superconductivity, the microscopic theory of superconductivity, the calculation of the control temperature and its possible maximum value are presented. An explanation of the mechanism of superconductivity in recently discovered superconducting metal oxide ceramics and the perspectives for the realization of new high-temperature superconducting materials are discussed. 56 refs, 2 figs, 3 tabs

  19. Contribution of nuclear microanalysis and of 18O tracer technique to study the oxygen sublattice in high Tc superconducting thin films

    International Nuclear Information System (INIS)

    Siejka, J.

    1994-01-01

    At first a short review of IBA contribution to the determination of composition and structure, including phonon properties of high T c superconducting oxides is presented. In the second part, IBA contribution to the elucidation of the mechanisms of thin film growth is presented. The emphasis is on the complementarity of IBA, Raman spectroscopy and XRD techniques to characterize thin films of high T c superconducting oxides. In the third part, some recent results related mainly to YBaCuO films grown on (100) oriented single crystalline bulk materials (MgO, LaAlO 3 , SrTiO 3 ) is discussed. In these experiments, IBA, XRD and Raman spectroscopies were used to study the oxygen content in a series of YBaCuO films prepared in different conditions of pressure and temperature. In the case of c-axis oriented films a good agreement between these three methods was found for the films cooled down at high oxygen pressure and a significant disagreement for the films cooled down at low oxygen pressure, showing structures with anomalous c-axis parameter. In the case of a-axis oriented films grown on SrTiO 3 substrates it was found that the low T c values (∼ 70-80 K) are not correlated with the oxygen content but rather with a disorder in the oxygen sublattice. The disorder in the oxygen sublattice was studied using the 16 O(α, α) 16 O resonance in random and channeling geometry. These results are correlated with the data provided by Raman spectroscopy. The 18 O tracer technique was used to estimate the diffusion coefficient in the a-axis oriented YBaCuO films showing a huge anisotropy of the 18 O labelling. Combining Raman and IBA techniques, the selective 18 O labelling of the CuO chain-planes was evidenced. The defects in the 18 O enriched CuO chain-planes were studied using the 18 O(p, α) 15 N nuclear resonant reaction in random and channeling geometries. Some preliminary results related to roughness of YBaCuO films are also discussed. The physical implications of these

  20. Hole superconductivity

    International Nuclear Information System (INIS)

    Hirsch, J.E.; Marsiglio, F.

    1989-01-01

    The authors review recent work on a mechanism proposed to explain high T c superconductivity in oxides as well as superconductivity of conventional materials. It is based on pairing of hole carriers through their direct Coulomb interaction, and gives rise to superconductivity because of the momentum dependence of the repulsive interaction in the solid state environment. In the regime of parameters appropriate for high T c oxides this mechanism leads to characteristic signatures that should be experimentally verifiable. In the regime of conventional superconductors most of these signatures become unobservable, but the characteristic dependence of T c on band filling survives. New features discussed her include the demonstration that superconductivity can result from repulsive interactions even if the gap function does not change sign and the inclusion of a self-energy correction to the hole propagator that reduces the range of band filling where T c is not zero

  1. Five-fold way to new high Tc superconductors

    Indian Academy of Sciences (India)

    shook the foundation of phonon-mediated pairing mechanism. In fact, certain in- ...... of superconducting Tc in doped cuprates below optimal doping. ...... ductor transition, the following are the minimal requirements for superconductivity:.

  2. Superconductivity at 43K in SmFeAsO1-xFx

    Science.gov (United States)

    Chen, X. H.; Wu, T.; Wu, G.; Liu, R. H.; Chen, H.; Fang, D. F.

    2008-06-01

    Since the discovery of high-transition-temperature (high-Tc) superconductivity in layered copper oxides, extensive effort has been devoted to exploring the origins of this phenomenon. A Tc higher than 40K (about the theoretical maximum predicted from Bardeen-Cooper-Schrieffer theory), however, has been obtained only in the copper oxide superconductors. The highest reported value for non-copper-oxide bulk superconductivity is Tc = 39K in MgB2 (ref. 2). The layered rare-earth metal oxypnictides LnOFeAs (where Ln is La-Nd, Sm and Gd) are now attracting attention following the discovery of superconductivity at 26K in the iron-based LaO1-xFxFeAs (ref. 3). Here we report the discovery of bulk superconductivity in the related compound SmFeAsO1-xFx, which has a ZrCuSiAs-type structure. Resistivity and magnetization measurements reveal a transition temperature as high as 43K. This provides a new material base for studying the origin of high-temperature superconductivity.

  3. A contribution to the study of high Tc superconducting coatings and multi-layer coatings electromagnetic properties: surface impedance measurement with a tunnel diode oscillator

    International Nuclear Information System (INIS)

    Omari, A.

    1993-01-01

    A surface impedance measurement system for conducting or superconducting thin films have been developed through the electromagnetic coupling of these films to a tunnel diode oscillator. The electromagnetic response of YBa 2 Cu 3 O 7-δ superconducting films and of id/La 2-x Sr x Cu O 4 multilayers, is studied, showing the 'granular' type of these materials. The intergranular coupling is of the SIS type for the films and of the SNS type for the multilayers. A resistance increase is observed when the temperature decreases in the superconducting phase. 120 p., 45 fig., 60 ref

  4. Long-term research in Japan: amorphous metals, metal oxide varistors, high-power semiconductors and superconducting generators

    Energy Technology Data Exchange (ETDEWEB)

    Hane, G.J.; Yorozu, M.; Sogabe, T.; Suzuki, S.

    1985-04-01

    The review revealed that significant activity is under way in the research of amorphous metals, but that little fundamental work is being pursued on metal oxide varistors and high-power semiconductors. Also, the investigation of long-term research program plans for superconducting generators reveals that activity is at a low level, pending the recommendations of a study currently being conducted through Japan's Central Electric Power Council.

  5. Josephson plasma resonance in superconducting multilayers

    DEFF Research Database (Denmark)

    Pedersen, Niels Falsig

    1999-01-01

    We derive an analytical solution for the josephson plasma resonance of superconducting multilayers. This analytical solution is derived mainly for low T-c systems with magnetic coupling between the superconducting layers, but many features of our results are more general, and thus an application...... to the recently derived plasma resonance phenomena for high T-c superconductors of the BSCCO type is discussed....

  6. Enhanced99Tc retention in glass waste form using Tc(IV)-incorporated Fe minerals

    OpenAIRE

    Um, W; Luksic, SA; Wang, G; Saslow, S; Kim, DS; Schweiger, MJ; Soderquist, CZ; Bowden, ME; Lukens, WW; Kruger, AA

    2017-01-01

    © 2017 Elsevier B.V. Technetium ( 99 Tc) immobilization by doping into iron oxide mineral phases may alleviate the problems with Tc volatility during vitrification of nuclear waste. Because reduced Tc, Tc(IV), substitutes for Fe(III) in the crystal structure by a process of Tc reduction from Tc(VII) to Tc(IV) followed by co-precipitation of Fe oxide minerals, two Tc-incorporated Fe minerals (Tc-goethite and Tc-magnetite/maghemite) were prepared and tested for Tc retention in glass melt sample...

  7. Exact mapping of the dx2-y2 Cooper-pair wavefunction onto the spin fluctuations in cuprates: the Fermi surface as a driver for 'high Tc' superconductivity

    International Nuclear Information System (INIS)

    McDonald, Ross D; Harrison, Neil; Singleton, John

    2009-01-01

    We propose that the extraordinarily high superconducting transition temperatures in the cuprates are driven by an exact mapping of the d x 2 -y 2 Cooper-pair wavefunction onto the incommensurate spin fluctuations observed in neutron-scattering experiments. This is manifested in the direct correspondence between the inverse of the incommensurability factor δ seen in inelastic neutron-scattering experiments and the measured superconducting coherence length ξ 0 . Strikingly, the relationship between ξ 0 and δ is valid for both La 2-x Sr x CuO 4 and YBa 2 Cu 3 O 7-x , suggesting a common mechanism for superconductivity across the entire hole-doped cuprate family. Using data from recent quantum-oscillation experiments in the cuprates, we propose that the fluctuations responsible for superconductivity are driven by a Fermi-surface instability. On the basis of these findings, one can specify the optimal characteristics of a solid that will exhibit 'high T c ' superconductivity. (fast track communication)

  8. Surface damage mitigation of TC4 alloy via micro arc oxidation for oil and gas exploitation application: Characterizations of microstructure and evaluations on surface performance

    Science.gov (United States)

    Xie, Ruizhen; Lin, Naiming; Zhou, Peng; Zou, Jiaojuan; Han, Pengju; Wang, Zhihua; Tang, Bin

    2018-04-01

    Because of its excellent corrosion resistance, high specific strength and high tensile strength, TC4 titanium alloys used as petroleum tubes have received wide interest from material engineers after many technical investigations and estimations. However, because of its low surface hardness values, high coefficient of friction and poor wear resistance, the TC4 alloy is seldom adopted in tribological-related engineering components. In this work, micro-arc oxidation (MAO) coatings were fabricated on TC4 alloys in NaAlO2 and (NaPO3)6 electrolytes with and without ultrasonic assistance. The microstructural characterizations of the produced MAO coatings were investigated. Comparative estimations of electrochemical corrosion in CO2-saturated simulated oilfield brine and tribological behaviours on MAO coatings and TC4 alloys were conducted. The results showed that the introduction of ultrasound increased the thickness of the MAO coatings. The thickness increased by 34% and 15% in the NaAlO2 and (NaPO3)6 electrolytes, respectively. There was no significant discrepancy in phase constitutions when the MAO processes were conducted with and without ultrasonic assistance. Both MAO coatings obtained with and without ultrasonic assistance were found to improve the corrosion and wear resistance of the TC4 alloy. MAO treatments made it possible to ensure the working surface of a TC4 alloy with an enhanced surface performance for oil and gas exploitation applications.

  9. Nanostructured metal oxides: promise opportunity and challenge to develop clinically useful 99Mo/99mTc generators using (n, gamma)99Mo

    International Nuclear Information System (INIS)

    Dash, Ashutosh

    2014-01-01

    The role of 99m Tc diagnostic nuclear medicine needs hardly to be reiterated. Today, it is the most widely used radionuclide for single photon emission computed tomography (SPECT) imaging procedures. The current strategy of availing 99m Tc is ensured from column chromatographic 99 Mo/ 99m Tc generators using a bed of acidic alumina. While the column chromatographic 99 Mo/ 99m Tc generator constitute a successful exemplar of availing 99m Tc, the limited capacity of alumina (2-20 mg Mo per g of alumina) for taking up molybdate ions necessitates the use of 99 Mo of the highest specific activity available, as can be found in fission produced 99 Mo (F 99 Mo). In order to reduce dependence of F 99 Mo, the scope of using low specific activity (n,γ) 99 Mo along with high capacity adsorbent is an interesting prospect. In this context, the scope of using nanomaterials as a viable adsorbent seemed attractive by virtue of their huge surface to volume ratios, altered physical properties, tailored surface chemistry, favorable adsorption characteristics, and enhanced surface reactivity resulting from the nanoscale dimensions. This emerging class of adsorbent represents an innovative paradigm and is expected to play an important role in the development of 99 Mo/ 99m Tc generators adaptable to the existing and foreseeable demands. This talk outlines a critical assessment on the role of nanostructured metal oxides, recent developments, the contemporary status, and key challenges and apertures to the near future. (author)

  10. Thermodynamic behavior of high-Tc oxide systems via EMF and related measurements

    International Nuclear Information System (INIS)

    Tetenbaum, M.; Tumidajaski, P.; Bloom, I.D.; Brown, D.L.; Blander, M.

    1991-01-01

    EMF measurements of oxygen fugacities as a function of stoichiometry have been made in the YBa 2 Cu 3 O x , and NdBa 2 Cu 3 O x , and Nd 1.81 Ce 0.19 CuO x superconducting systems in the temperature range 400--750 degree C by means of an oxygen titration technique with an yttria-stabilized zirconia electrolyte. The object of our current measurements is to investigate the effect of ionic size of Y, Gd and Nd on the thermodynamic behavior and structural transition in the LnBa 2 Cu 3 O x system. The shape of the 400 degree C isotherm for NdBa 2 Cu 3 O x suggests the presence of a miscibility gap at lower temperatures, at values of x that are higher than those in the YBa 2 Cu 3 O x system. The locations of the miscibility gaps are consistent with the effects of ionic radii on the composition dependence of T c for these systems. Our results explain the two plateaus in measured value of T c as a function of composition for the YBa 2 Cu 3 O x system and appear to be consistent with the less pronounced T c plateaus found for the NdBa 2 Cu 3 O x system higher stoichiometry values. For a given oxygen stoichiometry, partial pressures of oxygen above NdBa 2 Cu 3 O x are higher than for the YBa 2 Cu 3 O x system in accord with calculated partial molar thermodynamic quantities. The results of limited measurements on the n-type (electron-doped) superconducting Nd 1.81 Ce 0.19 CuO x system will be presented. A thermodynamic assessment and intercomparison of our oxygen partial pressure measurements with the results of other measurements will be presented. 34 refs., 9 figs., 1 tab

  11. Oxidation of methionine - is it limiting the diagnostic properties of 99mTc-labeled Exendin-4, a Glucagon-Like Peptide-1 receptor agonist?

    Science.gov (United States)

    Janota, Barbara; Karczmarczyk, Urszula; Laszuk, Ewa; Garnuszek, Piotr; Mikołajczak, Renata

    2016-01-01

    Preliminary clinical evaluation of 99mTc-EDDA/HYNIC-Met14-Exendin-4 showed that the complex offers new diagnostic possibilities for insulinoma and MTC. Exendin-4 contains methionine at position 14 in the amino acid chain, which may be oxidized to methionine sulfoxide and, from the pharmaceutical point of view, the oxidized moiety becomes an undesired impurity in the final radioactive preparation. Therefore, the aim of this study was to investigate the influence of commonly used methods to eliminate the effect of methionine oxidation in peptides, i.e. the replacement of methionine by norleucine (Nle) and the addition of L-methionine, on the in vitro stability and the biodistribution. 99mTc-EDDA/HYNIC-Met14-Exendin-4, 99mTc-EDDA/HYNIC-Nle14-Exendin-4, 99mTc-EDDA/HYNIC-Met14-Ex-endin-4 with the addition of L-methionine and an oxidized form of Exendin-4, i.e. 99mTc-EDDA/HYNIC-Met14(ox)-Exendin-4 were compared in vivo with 68Ga-NODAGA-Nle14-Exendin-4 in normal Wistar rats. The stability and lipophilicity were determined in vitro. Biodistribution studies confirmed the specific uptake of all tested complexes in the GLP-1 positive organs: lungs, pancreas and stomach. The uptake of 99mTc-EDDA/HYNIC-Met14-Exendin-4 with the addition of L-methionine and for 68Ga-NODAGA-Nle14-Exendin-4 at 1h p.i. was around 2-fold higher than that of 99mTc-EDDA/HYNIC-Met14-Exendin-4 and 99mTc-EDDA/HYNIC-Nle14-Exendin-4. Although the substitution of methionine by norleucine in the HYNIC-Exendin-4 did not result in improved bio-distribution, the use of L-methionine, as the excipient that inhibits the oxidation of methionine in the peptide chain resulted in higher lung/blood and stomach/blood uptake ratios. Our results confirmed that methionine at position 14 of amino acid chain of Exendin-4 plays an important role in the interaction with GLP-1 receptor positive tissue.

  12. Superconductivity: Is there a problem in transuranics?

    International Nuclear Information System (INIS)

    Colineau, Eric; Griveau, Jean-Christophe; Eloirdi, Rachel; Hen, Amir; Caciuffo, Roberto

    2014-01-01

    Superconductivity was first reported in 1942 for uranium metal (¡-U) and in 1958 for U compounds: UCo, U6Mn, U6Fe, and U6Co, with critical temperatures Tc, of 1.7, 2.3, 3.9, and 2.3K, respectively. A new class of U superconductors emerged in the early 1980’s with the discovery of U heavy fermion superconductors : UBe13 (Tc = 0.85K), UPt3 (Tc = 0.53K), URu2Si2 (Tc = 1.5K) , UPd2Al3 (Tc = 1.9K) … Furthermore, in most of these systems, the superconducting phases coexist with antiferromagnetic (AF) correlations which have characteristic temperatures, usually the Néel temperature TN, that are typically one order of magnitude greater than the corresponding superconducting critical temperatures Tc. Superconductivity was even shown to co-exist with ferromagnetism in e.g. UGe2 (Tc ï» 0.8K, TC ï» 30K at p ï» 1.2GPa) and URhGe (Tc = 0.25K, TC = 9.5K). Heavy fermion superconductors still remain a major challenge for condensed matter physics. The existence of heavy fermion superconductivity and its coexistence or proximity with magnetic order suggests that the conventional mechanism of phonon-mediated superconductivity is inappropriate and that alternative mechanisms, like spin fluctuations, should be considered for Cooper pairing

  13. Superconductivity: materials and applications

    International Nuclear Information System (INIS)

    Duchateau, J.L.; Kircher, F.; Leveque, J.; Tixador, P.

    2008-01-01

    This digest paper presents the different types of superconducting materials: 1 - the low-TC superconductors: the multi-filament composite as elementary constituent, the world production of NbTi, the superconducting cables of the LHC collider and of the ITER tokamak; 2 - the high-TC superconductors: BiSrCaCuO (PIT 1G) ribbons and wires, deposited coatings; 3 - application to particle physics: the the LHC collider of the CERN, the LHC detectors; 4 - applications to thermonuclear fusion: Tore Supra and ITER tokamaks; 5 - NMR imaging: properties of superconducting magnets; 6 - applications in electrotechnics: cables, motors and alternators, current limiters, transformers, superconducting energy storage systems (SMES). (J.S.)

  14. Spectral investigation of hot-spot and cavity resonance effects on the terahertz radiation emitted from high-Tc superconducting Bi2Sr2CaCu2O8+δ single crystal mesa structures

    Science.gov (United States)

    Kadowaki, Kazuo; Watanabe, Chiharu; Minami, Hidetoshi; Yamamoto, Takashi; Kashiwagi, Takanari; Klemm, Richard

    2014-03-01

    Terahertz (THz) electromagnetic radiation emitted from high-Tc superconducting Bi2Sr2CaCu2O8+δ mesa structures in the case of single mesa and series-connected mesas is investigated by the FTIR spectroscopic technique while observing its temperature distribution simultaneously by a SiC photoluminescence technique. Changing the bias level, sudden jumps of the hot-spot position were clearly observed. Although the radiation intensity changes drastically associated with the jump of the hot spot position, the frequency is unaffected as long as the voltage per junction is kept constant. Since the frequency of the intense radiation satisfies the cavity resonance condition, we confirmed that the cavity resonance is of primarily importance for the synchronization of whole intrinsic Josephson junctions in the mesa for high power radiation. This work was supported in part by the Grant-in-Aid for challenging Exploratory Research, the Ministry of Education, Culture, Sports, Science & Technology (MEXT).

  15. Application of in-beam perturbed angular distribution to the study of high-Tc oxides

    International Nuclear Information System (INIS)

    Komori, Fumio; Katsumoto, Shingo; Kobayashi, Shun-ichi; Ikehata, Seiichiro; Ikeda, Nobuo; Hashimoto, Osamu; Fukuda, Tomokazu; Nomura, Toru; Yamazaki, Toshimitsu.

    1990-04-01

    The time differential perturbed angular distribution method was applied to the study of high-T c oxides. Spin rotation signals of the 19 F isomer (τ = 128 nsec) produced from oxygen nuclei via 16 O(α,p) 19 F were observed in various high-T c oxides above T c . The internal field was determined with the accuracy of about 1%. This method is an alternative to the 17 O substituted NMR. (author)

  16. Fabrication of superconducting wire using organometallic precursors and infiltration

    International Nuclear Information System (INIS)

    Lee, Y.J.

    1991-01-01

    Organometallic precursors from naphthenic acid and metal nitrates were used for the synthesis of YBCO oxide superconducting compounds. The characteristics of metal naphthenates as organometallic precursors were investigated by IR spectra, viscosity measurements, and infiltration. 123 superconducting compound obtained from 123 naphthenate showed a Tc of 90 degree K and a rather dense and elongated microstructure. Also, the melting behavior of Ba-cuprates which were used for 123 making was studied. A low-temperature melting process was developed to fabricate silver-sheathed superconducting wire with the powder-in-tube method; flowing argon gas is introduced to the system at 930-945 degree C to reduce the melting temperature of the 123 compound without silver sheath melting. It resulted in a 90 degree K Tc superconducting core with dense and locally aligned microstructure. SEM-EDS and XRD analysis, 4-probe resistance and Jc measurements, and carbon-content determinations were carried out to characterize the microstructure, grain alignment, and superconducting properties of the samples

  17. Enhanced 99 Tc retention in glass waste form using Tc(IV)-incorporated Fe minerals

    Energy Technology Data Exchange (ETDEWEB)

    Um, Wooyong; Luksic, Steven A.; Wang, Guohui; Saslow, Sarah; Kim, Dong-Sang; Schweiger, Michael J.; Soderquist, Chuck Z.; Bowden, Mark E.; Lukens, Wayne W.; Kruger, Albert A.

    2017-11-01

    Technetium (99Tc) immobilization by doping into iron oxide mineral phases may alleviate the problems with Tc volatility during vitrification of nuclear waste. Reduced Tc, Tc(IV), substitutes for Fe(III) in the crystal structure by a process of Tc reduction from Tc(VII) to Tc(IV) followed by co-precipitation of Fe oxide minerals. Two Tc-incorporated Fe minerals (Tc-goethite and Tc-magnetite/maghemite) were prepared and tested for Tc retention in glass melt samples at temperatures between 600 – 1,000 oC. After being cooled, the solid glass specimens prepared at different temperatures were analyzed for Tc oxidation state using Tc K-edge XANES. In most samples, Tc was partially oxidized from Tc(IV) to Tc(VII) as the melt temperature increased. However, Tc retention in glass melt samples prepared using Tc-incorporated Fe minerals were moderately higher than in glass prepared using KTcO4 because of limited and delayed Tc volatilization.

  18. Microstructure and critical current density in high-Tc metal oxide superconductors

    International Nuclear Information System (INIS)

    Johnson, S.M.; Gusman, M.I.

    1992-03-01

    Superconductor powders in the U-Ba-Cu-O (YBCO) and Bi-Pb-Sr-Ca-Cu-O (BSCCO) systems were synthesized by freeze-drying. Powders were characterized, and processed into samples for evaluation of superconducting behavior. Freeze-drying is attractive because the powders have high purity, are homogeneous, have a small size and are active. YBCO powders can be sintered to high density at 890 degrees C. Many compositions, processing approaches and heat treatments were explored in an effort to understand relations between microstructure and critical density, and to improve the critical current density. Powders were also formed into sputtering targets for coating preparation at Stanford University. The highest critical current density achieved with the YBCO powders was ∼15,000 A/cm 2 at 4.2K and 0.5T using powders treated to prevent carbon contamination. The BSCCO materials with the highest critical current density, ∼30,000 A/cm 2 at the same conditions were formed by heat treating melted and quenched samples. All critical current density measurements were made by Stanford University, a subcontractor to this effort. Stanford University also prepared coatings by off-axis magnetron sputtering

  19. The Rashba spin-orbit coupling for superconductivity in oxide interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Beyl, Stefan; Orth, Peter P.; Schmalian, Joerg [Institut fuer Theorie der Kondensierten Materie, Karlsruher Institut fuer Technologie, Karlsruhe (Germany)

    2014-07-01

    We investigate the role of the Rashba spin-orbit coupling on the superconducting order parameter and the phase stiffness at the interface of LaAlO{sub 3} and SrTiO{sub 3}. In particular, we analyze the gate controlled crossover between BCS superconductivity and Bose-Einstein condensation of Cooper pairs, amplified by the Rashba coupling and the possibility of a phase fluctuation induced quantum critical point.

  20. Trinitromethyl Heterocyclic Oxidizers as a Solid Propellant Ingredient Final Report CRADA No TC02146.0

    Energy Technology Data Exchange (ETDEWEB)

    Pagoria, P. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Racoveanu, A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2017-08-15

    This was a collaborative effort between Lawrence Livermore National Security, LLC as manager and operator of Lawrence Livermore National Laboratory (LLNL) and Physical Sciences, Inc. (PSI), to develop a synthesis of two novel energetic heterocyclic oxidizers as possible replacements for ammonium perchlorate (AP) in rocket propellant formulations. This CRADA resulted from the award of the Phase I Small Business Technology Transfer (STTR) from DOD. The CRADA consisted of two phases. The goal for Phase 1 was to produce a new oxidizer called TNMDNP. Phase 2 is optional (based on the success of Phase 1) and the goal of Phase 2 (optional) was to produce a new oxidizer called TNMDNT. Phase 2 tasks would be performed based on the successful results of Phase 1.

  1. Reactive nanophase oxide additions to melt-processed high-{Tc} superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Goretta, K.C.; Brandel, B.P.; Lanagan, M.T.; Hu, J.; Miller, D.J.; Sengupta, S. [Argonne National Lab., IL (United States); Parker, J.C.; Ali, M.N. [Nanophase Technologies Corp., Darien, IL (United States); Chen, Nan [Illinois Superconductor Corp., Evanston, IL (United States)

    1994-10-01

    Nanophase TiO{sub 2} and Al{sub 2}O{sub 3} powders were synthesized by a vapor-phase process and mechanically mixed with stoichiometric YBa{sub 2}Cu{sub 3}O{sub x} and TlBa{sub 2}Ca{sub 2}Cu{sub 3}O{sub x} powders in 20 mole % concentrations. Pellets produced from powders with and without nanophase oxides were heated in air or O{sub 2} above the peritectic melt temperature and slow-cooled. At 4.2 K, the intragranular critical current density (J{sub c}) increased dramatically with the oxide additions. At 35--50 K, effects of the oxide additions were positive, but less pronounced. At 77 K, the additions decreased J{sub c}, probably because of inducing a depresion of the transition temperature.

  2. High temperature superconductivity the road to higher critical temperature

    CERN Document Server

    Uchida, Shin-ichi

    2015-01-01

    This book presents an overview of material-specific factors that influence Tc and give rise to diverse Tc values for copper oxides and iron-based high- Tc superconductors on the basis of more than 25 years of experimental data, to most of which the author has made important contributions. The book then explains why both compounds are distinct from others with similar crystal structure and whether or not one can enhance Tc, which in turn gives a hint on the unresolved pairing mechanism. This is an unprecedented new approach to the problem of high-temperature superconductivity and thus will be inspiring to both specialists and non-specialists interested in this field.   Readers will receive in-depth information on the past, present, and future of high-temperature superconductors, along with special, updated information on what the real highest Tc values are and particularly on the possibility of enhancing Tc for each member material, which is important for application. At this time, the highest Tc has not been...

  3. Quasiparticle self-consistent GW study of cuprates: electronic structure, model parameters, and the two-band theory for Tc.

    Science.gov (United States)

    Jang, Seung Woo; Kotani, Takao; Kino, Hiori; Kuroki, Kazuhiko; Han, Myung Joon

    2015-07-24

    Despite decades of progress, an understanding of unconventional superconductivity still remains elusive. An important open question is about the material dependence of the superconducting properties. Using the quasiparticle self-consistent GW method, we re-examine the electronic structure of copper oxide high-Tc materials. We show that QSGW captures several important features, distinctive from the conventional LDA results. The energy level splitting between d(x(2)-y(2)) and d(3z(2)-r(2)) is significantly enlarged and the van Hove singularity point is lowered. The calculated results compare better than LDA with recent experimental results from resonant inelastic xray scattering and angle resolved photoemission experiments. This agreement with the experiments supports the previously suggested two-band theory for the material dependence of the superconducting transition temperature, Tc.

  4. High temperature superconducting material: Bismuth strontium calcium copper oxide. (Latest citations from the Aerospace database). Published Search

    International Nuclear Information System (INIS)

    1993-11-01

    The bibliography contains citations concerning the development, fabrication, and analysis of a high temperature superconducting material based on bismuth-strontium-calcium-copper-oxides (Bi-Sr-Ca-Cu-O). Topics include the physical properties, structural and compositional analysis, magnetic field and pressure effects, and noble metal dopings of Bi-Sr-Ca-Cu-O based systems. The highest transition temperature recorded to date for this material was 120 degrees Kelvin. Fabrication methods and properties of Bi-Sr-Ca-Cu-O films and ceramics are also considered. (Contains 250 citations and includes a subject term index and title list.)

  5. Superconductivity in nanostructured lead

    Science.gov (United States)

    Lungu, Anca; Bleiweiss, Michael; Amirzadeh, Jafar; Saygi, Salih; Dimofte, Andreea; Yin, Ming; Iqbal, Zafar; Datta, Timir

    2001-01-01

    Three-dimensional nanoscale structures of lead were fabricated by electrodeposition of pure lead into artificial porous opal. The size of the metallic regions was comparable to the superconducting coherence length of bulk lead. Tc as high as 7.36 K was observed, also d Tc/d H was 2.7 times smaller than in bulk lead. Many of the characteristics of these differ from bulk lead, a type I superconductor. Irreversibility line and magnetic relaxation rates ( S) were also studied. S( T) displayed two maxima, with a peak value about 10 times smaller than that of typical high- Tc superconductors.

  6. The interaction between ApoA2 -265T>C polymorphism and dietary fatty acids intake on oxidative stress in patients with type 2 diabetes mellitus.

    Science.gov (United States)

    Zamani, Elham; Sadrzadeh-Yeganeh, Haleh; Sotoudeh, Gity; Keramat, Laleh; Eshraghian, Mohammadreza; Rafiee, Masoumeh; Koohdani, Fariba

    2017-08-01

    Apolipoprotein A2 (APOA2) -265T>C polymorphism has been studied in relation to oxidative stress and various dietary fatty acids. Since the interaction between APOA2 polymorphism and dietary fatty acids on oxidative stress has not yet discussed, we aimed to investigate the interaction on oxidative stress in type 2 diabetes mellitus (T2DM) patients. The subjects were 180 T2DM patients with known APOA2 genotype, either TT, TC or CC. Superoxide dismutase (SOD) activity was determined by colorimetric method. Total antioxidant capacity (TAC) and serum level of 8-isoprostane F2α were measured by spectrophotometry and ELISA, respectively. Dietary intake was collected through a food frequency questionnaire. Based on the median intake, fatty acids intake was dichotomized into high or low groups. The interaction between APOA2 polymorphism and dietary fatty acids intake was analyzed by ANCOVA multivariate interaction model. Higher than median intake of omega-6 polyunsaturated fatty acids (n-6 PUFA) was associated with increased serum level of 8-isoprostane F2α in subjects with TT/TC genotype (p = 0.004), and higher than median intake of omega-3 polyunsaturated fatty acids (n-3 PUFA) was associated with increased serum SOD activity in CC genotype (p fatty acids intake on oxidative stress. More investigations on different populations are required to confirm the interaction.

  7. Superconductivity mediated by anharmonic phonons: application to β-pyrochlore oxides

    Science.gov (United States)

    Hattori, Kazumasa; Tsunetsugu, Hirokazu

    2010-03-01

    We investigate three dimensional anharmonic phonons under tetrahedral symmetry and superconductivity mediated by these phonons. Three dimensional anharmonic phonon spectra are calculated directly by solving Schr"odinger equation and the superconducting transition temperature is determined by using the theory of strong coupling superconductivity assuming an isotropic gap function. With increasing the third order anharmonicity b of the tetrahedral potential, we find a crossover in the energy spectrum to a quantum tunneling regime. We obtain strongly enhanced transition temperatures around the crossover point. The first order transition observed in KOs2O6 is discussed in terms of the first excited state energy δ, and the coupling constant λ in the strong coupling theory of superconductivity. Our results suggest that the decrease of λ and increase of δ below the first order transition temperature. We point out that the change in the oscillation amplitude and characterizes this isomorphic transition. The chemical trends of the superconducting transition temperature, λ, and δ in the β-pyrochlore compounds are also discussed.

  8. Conductus makes high-Tc integrated circuit

    International Nuclear Information System (INIS)

    Anon.

    1991-01-01

    This paper reports that researchers at Conductus have successfully demonstrated what the company says is the world's first integrated circuit containing active devices made from high-temperature superconductors. The circuit is a SQUID magnetometer made from seven layers of material: three layers of yttrium-barium-copper oxide, two layers of insulating material, a seed layer to create grain boundaries for the Josephson junctions, and a layer of silver for making electrical contact to the device. The chip also contains vias, or pathways that make a superconducting contact between the superconducting layers otherwise separated by insulators. Conductus had previously announced the development of a SQUID magnetometer that featured a SQUID sensor and a flux transformer manufactured on separate chips. What makes this achievement important is that the company was able to put both components on the same chip, thus creating a simple integrated circuit on a single chip. This is still a long way from conventional semiconductor technology, with as many as a million components per chip, or even the sophisticated low-Tc superconducting chips made by the Japanese, but the SQUID magnetometer demonstrates all the elements and techniques necessary to build more complex high-temperature superconductor integrated circuits, making this an important first step

  9. Tc enhancement and superconducting properties of a YBa[sub 2]Cu[sub 3]O[proportional to]6. 5 thin film after fluorine insertion

    Energy Technology Data Exchange (ETDEWEB)

    Pena, O.; Mokhtari, M.; Perrin, C.; Thivet, C.; Guilloux-Viry, M.; Perrin, A.; Sergent, M. (Lab. de Chimie du Solide et Inorganique Moleculaire, Univ. de Rennes 1, 35 (France))

    1993-02-10

    An oxygen-deficient YBa[sub 2]Cu[sub 3]O[sub x] thin film (Tc=54 K, [Delta]Tc>8K) was treated under a diluted (3% in N[sub 2]) NF[sub 3] gas flow at temperatures not exceeding 280degC. AC induction measurements show a substantial increase of Tc up to about 86 K and a clear improvement of the [chi]''[sub AC] dissipation component (FWHM=1.2 K), as a function of the reaction time. The film was further studied at the end of the reaction by the AC-field dependence and by DC magnetization measurements, including ZFC/FC and magnetization cycles. It was found that granular effects are not important, meaning that the crystalline properties of the film are not degraded by the fluorination process, in good agreement with the X-ray diffraction data. The sharpness of the [chi]''[sub AC] peak, the low M[sub FC]/M[sub ZFC] ratio and the large hysteresis of the magnetization cycle indicate that the critical current densities are high (of the order of 10[sup 6] A/cm[sup 2] at 5 K) and comparable to reasonably good YBa[sub 2]Cu[sub 3]O[sub 7] thin films. The usefulness of the fluorination method and a comparison with halogenated YBa[sub 2]Cu[sub 3]O[sub x] ceramics are also presented. (orig.).

  10. Microwave plasma CVD of oxide films relating to high Tc Bi-Sr-Ca-Cu-O superconductor

    International Nuclear Information System (INIS)

    Hashimoto, T.; Kosaka, T.; Yoshida, Y.; Yoshimoto, M.; Koinuma, H.

    1989-01-01

    Microwave plasma CVD was applied to the synthesis of Bi, Sr, Ca, and Cu oxide films at relatively low temperatures. Gas source materials used were Bi(C 6 H 5 ) 3 , Sr(PPM) 2 , Ca(PPM) 2 , and Cu(HFA) 2 , where PPM and HFA represent C 2 F 5 COCHCOC(CH 3 ) 3 and CF 3 COCHCOCF 3 , respectively. Films were deposited on MgO (100) substrate at temperatures between 200 C and 400 C under an atmosphere of 1000mTorr Ar-O 2 (50/100) mixture which was partially excited by plasma. From Bi(C 6 H 5 ) 3 , Bi 2 O 3 was formed at 200 C without containing carbon above the detection level by XPS analysis. From Cu(HFA) 2 , CuO was prepared at 400 C by increasing oxygen partial pressure to 0.1Torr. (At lower oxygen partial pressure, CuF 2 or amorphous films were deposited.) From Sr(PPM) 2 and Ca(PPM) 2 , SrF 2 and CaF 2 were obtained at 400 C. The attempt to fabricate superconducting films is also reported

  11. Similarity in the superconducting properties of chalcogenides, cuprate oxides and fullerides

    International Nuclear Information System (INIS)

    Tsendin, K.D.; Popov, B.P.; Denisov, D.V.

    2004-01-01

    The idea of Anderson pairs has been put forward for explanation of many extraordinary properties of chalcogenides glassy semiconductors. Recent decades made obvious that these pairs localized on the centers with negative effective correlation energy (negative-U centers) really exist in chalcogenides. If the concentration of negative-U centers is enough to create the pair band states, this can lead to superconductivity because Anderson pairs are Bose particles. In the present paper we show that several puzzling superconductivity properties of chalcogenides, high-temperature cuprate superconductors and fullerides are similar for these three groups of materials and can be naturally explained in the frame of negative-U centers model of superconductivity

  12. Structural studies of metal oxides related to High-Tc superconductors

    International Nuclear Information System (INIS)

    Hjorth, M.

    1990-02-01

    The project was started in order to investigate metal oxide structures related in some way to high-T c superconductors, using the crystallographic methods available; and in order to be able to use crystallographic methods in ways that go beyond routine applications in order to contribute to the crystallographic knowledge concerning these oxides. The project goes a step outside the boarders normally defined by using the term ''high-T c superconductors'', thus studying metal oxides from a more general crystallographic viewpoint. The methods used are the expansions of the spherical atom model, and of the thermal probability density function, and combination of X-ray work with high resolution electron microscopy. The use of the expanded diffraction models presents problems such as bad convergence in least squares refinement, physical unreasonable parameters, problems with interpretation of the results and difficulties due to missing or insufficient computer programs. The use of these models is discussed. Dynamical theory is applied when considering electron diffraction results. The theory is presented, focusing on the modifications of the standard theory used for some of the structures considered in the thesis, and in overview on other theoretical topics is given. A presentation is given of the structures which have been considered and of earlier work on related compounds, of the problems and solutions applied to the compound discussed and of the results obtained. The results are discussed. The appendices describe published papers and the work not directly connected to the main topics, e.g. implementation and development of computer programs. (AB) 172 refs

  13. Magnetically-related properties of bismuth containing high Tc superconductors

    Science.gov (United States)

    Vezzoli, Gary C.; Chen, M. F.; Craver, F.; Safari, A.; Moon, B. M.; Lalevic, B.; Burke, Terence; Shoga, M.

    1990-08-01

    The effect of magnetic fields to 15 T on electrical resistance has been measured for the BiSrCaCuO superconductor at precise temperatures during the transition to the superconducting state from pre-onset conditions to essentially zero resistance conditions. The results show that the temperature at which the magnetic field causes a divergence in the resistance versus 1000/ T curve is approximately the same temperature as the value at which, during cooling, the positive Hall coefficient begins its abrupt descent to zero. This temperature gives the best measure of Tc. It is also shown that small oscillations of low frequency start near onset conditions, the amplitude of which at a given temperature is B-field dependent. Additionally, Hall effect studies as a function of temperature at 4 T in three separate experiments (including high Tc BiSrCaCu PbO of > 90% theoretical density) show that sharp delta-function-like peaks in + RH are observed near Tc and are superimposed on a broader maximum. The Hall data are explicable in terms of exciton formation and ionization. The bound holes associated with these excitons are believed to be the mediators producing Cooper-pairing, and scale very well with Tc for all the known high Tc oxides.

  14. Magnetic levitation and superconductivity

    International Nuclear Information System (INIS)

    Albrecht, C.

    1989-01-01

    The paper explains the impressive advances made in the development of superconducting magnets, in cryogenic engineering, and in the development of drive and vehicle concepts in Japan in the period following termination of West German development work for the electrodynamical system (MLU 001, MLU 002). The potentials engineering due to the development of high-Tc superconductors are discussed. (orig./MM) [de

  15. High Density, Insensitive Oxidizer With RDX Performance Final Report CRADA No. TC02178.0

    Energy Technology Data Exchange (ETDEWEB)

    Pagoria, P. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Preda, D. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2017-08-25

    This was a collaborative effort between Lawrence Livermore National Security, LLC as manager and operator of Lawrence Livermore National Laboratory (LLNL) and Physical Sciences, Inc. (PSI), to develop a synthesis and evaluate a novel high density, insensitive oxidizer with RDX performance. This CRADA resulted from the award of a Phase I STTR ("STTR") from DOD. In recent years, the synthesis of new energetic heterocyclic compounds to replace the energetic materials currently in the stockpile has received a great amount of attention. The Office of the Secretary of Defense has identified that there is a need to incorporate new energetic materials in current and future weapon systems in an effort to increase performance and decrease sensitivity. For many of the future weapon systems, incorporation of energetic compounds currently in the stockpile will not provide the desired performance and sensitivity goals. The success of this CRADA may lead to a Phase I option STTR from DOD and to a Phase II STTR from DOD. The goal of this CRADA was to produce and test a novel oxidizer, 2,5,8-trinitroheptazine (TNH).

  16. Maskless X-Ray Writing of Electrical Devices on a Superconducting Oxide with Nanometer Resolution and Online Process Monitoring.

    Science.gov (United States)

    Mino, Lorenzo; Bonino, Valentina; Agostino, Angelo; Prestipino, Carmelo; Borfecchia, Elisa; Lamberti, Carlo; Operti, Lorenza; Fretto, Matteo; De Leo, Natascia; Truccato, Marco

    2017-08-22

    X-ray nanofabrication has so far been usually limited to mask methods involving photoresist impression and subsequent etching. Herein we show that an innovative maskless X-ray nanopatterning approach allows writing electrical devices with nanometer feature size. In particular we fabricated a Josephson device on a Bi 2 Sr 2 CaCu 2 O 8+δ (Bi-2212) superconducting oxide micro-crystal by drawing two single lines of only 50 nm in width using a 17.4 keV synchrotron nano-beam. A precise control of the fabrication process was achieved by monitoring in situ the variations of the device electrical resistance during X-ray irradiation, thus finely tuning the irradiation time to drive the material into a non-superconducting state only in the irradiated regions, without significantly perturbing the crystal structure. Time-dependent finite element model simulations show that a possible microscopic origin of this effect can be related to the instantaneous temperature increase induced by the intense synchrotron picosecond X-ray pulses. These results prove that a conceptually new patterning method for oxide electrical devices, based on the local change of electrical properties, is actually possible with potential advantages in terms of heat dissipation, chemical contamination, miniaturization and high aspect ratio of the devices.

  17. The Role of ?786T/C Polymorphism in the Endothelial Nitric Oxide Synthase Gene in Males with Clinical and Biochemical Features of the Metabolic Syndrome

    OpenAIRE

    Misiak, Blazej; Krolik, Marta; Kukowka, Anna; Lewera, Anna; Leszczynski, Przemyslaw; Stankiewicz-Olczyk, Joanna; Slezak, Ryszard

    2011-01-01

    Background. Extensive evidence, arising from models of endothelial nitric oxide synthase gene (NOS3)-knockout mice supports the role of endothelial malfunction in the pathogenesis of the metabolic syndrome (MS). Aims. The aim of this study was to evaluate the role of −786T/C polymorphism in the etiology of MS and assess previously reported interaction with cigarette smoking. Methods. Based on International Diabetes Federation 2005 criteria, we recruited randomly 152 subjects with MS and 75 su...

  18. The potential of large critical currents in the high Tc oxides

    International Nuclear Information System (INIS)

    Deutcher, G.

    1993-01-01

    The potential for high critical current densities is examined. on a thermodynamical basis, the energy scale for vortex pinning can be derived for instance from a measurement of the width of the critical region. This energy scale is of the order of 0.2 eV in YBCO, which is sufficient for practical applications. Another important parameter is the short coherence length. The inner plane length, of the order of a few lattice spacing, is favorable for pinning by point defects. But the very short outer plane length gives rise to anomalous magnetic behavior, unfavorable for high-field applications at high temperature; this is true in particular in most anisotropic oxides, such as the Bi compounds (author)

  19. Synthesis of high-temperature superconducting oxides and chemical alloying in Cu-O planes

    International Nuclear Information System (INIS)

    Tarascon, J.M.; Barboux, P.; Bagley, B.G.; Green, L.H.; Mckinnon, W.R.; Hull, G.W.

    1988-01-01

    Some methods for synthesis permitting to fabricate dense superconducting ceramics are considered. The Zole-Hell method is the most perspective one among them. Effect of oxygen content in a sample and copper substitution for nickel and zinc on structural, transition and superconducting properties of samples of the La-Sr-Cu-O(1) and Y-Ba-Cu-O(2) systems is studied. Copper substitution is established to suppress superconductivity in system 1 and to decrease T c in system 2, and this effect doesn't depend on the fact whether the substituting 3d-metal is magnetic (nickel) or diamagnetic (zinc). Detailed study of YBa 2 Cu 3 O 7-y properties as a function of oxygen content has shown that superconductivty in this composition can be suppressed as a result of oxygen removal and it can be reduced with its interoduction. The possibility to prepare nonalloyed La 2 CuO 4 in superconducting state as a result of plasma treatment comprises a scientific interest. 27 refs.; 5 figs.; 1 tab

  20. Application of high-pressure techniques: stabilization and oxidation-state control of novel superconductive and related multi-layered copper oxides

    International Nuclear Information System (INIS)

    Yamauchi, H.; Karppinen, M.

    2000-01-01

    Copper oxide superconductors possess multi-layered structures with a layer sequence of -CuO 2 -(Q-CuO 2 ) n-1 -AO-(MO 1±δ ) m -AO- or -CuO 2 -B-(O 2 -B) s-1 -CuO 2 -AO-(MO 1±δ ) m -AO- along the elongated c axis. Based on this layer sequence, the known copper oxide structures are categorized as members of the homologous series, M m A r Q n-1 Cu n O m+r+2 +n ±δ (M-mr(n-1)n ; category A) or M m A 2k B s Cu 1+k O m +4k +2s±δ (M-m(2k)s (1+k ); category B). Stabilization of such structures especially in the case of high values of the n /s parameter, i.e. the higher members of the homologous series, has been demonstrated to be apparently promoted under high pressures and/or strongly oxidizing conditions. Consequently, techniques for applying both high oxygen gas pressures (10-2000 atm) and ultra-high solid-medium pressures (2-8 GPa) have been advantageously utilized in synthesizing various superconductive copper oxide phases. Especially the ultra-high solid-medium pressure synthesis carried out in the so-called cubic-anvil/belt-type apparatus has proven to be extremely successful in synthesizing novel superconductive phases. In order to achieve high partial pressures of oxygen in the solid-medium environment, 'external' oxygen-generating oxides such as KClO 4 , KClO 3 and Ag 2 O 2 are commonly added to the precursor mixtures. It is emphasized that in some cases it is possible to utilize 'internal' oxidizing agents alone, i.e. highly oxidized precursors such as BaCuO 2+δ and Ba 2 Cu 3 O 5+δ containing metal constituents common with the desired copper oxide phase only. In the present paper, the potential and applications of high-pressure techniques in synthesizing multi-layered copper oxides and related structures are reviewed and discussed with emphasis on the important 'historical' discoveries of novel phases and the present status of controlled production of high-quality samples of such phases. (author)

  1. On the superconducting state in Ba0.6K0.4BiO3 perovskite oxide

    Science.gov (United States)

    Szcześniak, D.; Kaczmarek, A. Z.; Drzazga, E. A.; Szewczyk, K. A.; Szcześniak, R.

    2018-05-01

    We report study on the superconducting state in Ba0.6K0.4BiO3 (BKBO) perovskite oxide, motivated by the inconclusive results on the pairing mechanism in this compound. Our investigations are conducted within the Migdal-Eliashberg formalism, to account for the phonon-mediated superconducting phase. The considered doping level of the discussed material corresponds to the highest critical temperature in this compound, and allows simultaneous analysis of the oxygen isotope effect, for the O16 and O18 isotopes, respectively. We found that such effect is particularly visible for the critical values of the Coulomb pseudopotential (μC⋆) , which equals to 0.18 for the O16 and 0.16 for the O18 isotope in BKBO. Moreover, we determine the size of the superconducting energy band gap (Δg) and note that obtained values (9.68 meV and 9.55 meV for the O16 and O18, respectively) are in good agreement with the experimental predictions which give Δg ∼ 8.68 meV . Finally, we calculate the characteristic dimensionless parameters, such as the zero-temperature energy gap to the critical temperature, the ratio for the specific heat, as well as the ratio associated with the zero-temperature thermodynamic critical field, which suggest occurrence of the strong-coupling and retardation effects within the phonon-mediated scenario in the analyzed material. Where possible the dimensionless ratios are compared to the experimental estimates, and agrees with these which account for the strong-coupling character of the BKBO superconductor.

  2. The separation of sup(99m)Tc from 99Mo through an aluminium oxide chromatographic columm

    International Nuclear Information System (INIS)

    Imoto, S.T.

    1980-01-01

    The separation of sup(99m)Tc from 99 Mo using the chromatographic method is studied. Alumina is used as adsorbent. The pH values for adsorption of carrier-free 99 Mo on columns filled with ordinary alumina and with that thermically treated at 1000 0 C for five hours, and the separation conditions of sup(99m)Tc using physiologic solution as eluent are determined. The sup(99m)Tc separation yields of both columns are compared and the quality of the products obtained by successive elutions for 10 days is analyzed. (Author) [pt

  3. Structural and superconducting properties of La2−xNdxCuO4+y (0≤x≤0.5) prepared by room temperature chemical oxidation

    DEFF Research Database (Denmark)

    Rial, C.; Morán, E.; Alario-Franco, M.A.

    1997-01-01

    The systematic characterization of the structural and superconducting properties of room temperature chemically oxidized T/O La2-xNdxCuO4+y (0 less than or equal to x less than or equal to 0.5) has been performed by neutron powder diffraction and magnetic susceptibility measurements. Similarities...

  4. Synthesis and study of electrical properties of nonsuperconducting and low-Tc phases of Tl-Ba-Ca-Cu-O (TBCCO) superconducting materials

    International Nuclear Information System (INIS)

    Ahmed, F.; Samadder, A.M; Sultana, H.R.; Abul Hossain, M.; Khan, A.H.

    2005-09-01

    Samples of Tl-Ba-Ca-Cu-O system having nominal compositions of Tl 2 Ba 2 Ca 2n Cu 3+n O y (n=1, 2) have been synthesized. Sintering under different conditions were carried out to study their effect on the formation of superconductivity. In the present study it is found that all the samples prepared at temperature >850 deg. C show the dominance of nonsuperconducting phases. One sample prepared at well below the conventional sintering temperatures (655 deg. C) shows the formation of the low-T c phase of TBCCO system with T c =80K. In two samples simultaneous presence of two values of a∼b∼ namely 5.45A and 3.84A has been identified. (author)

  5. Non-invasive and high-sensitivity scanning detection of magnetic nanoparticles in animals using high-Tc scanning superconducting-quantum-interference-device biosusceptometry.

    Science.gov (United States)

    Chieh, J J; Hong, C Y

    2011-08-01

    Although magnetic nanoparticles (MNPs) have been widely applied to animals in biomedicine, MNPs within animals should be examined in real time, in vivo, and without bio-damaged possibility to evaluate whether the bio-function of MNPs is valid or to further controls the biomedicinal process because of accompanying complex problems such as MNPs distribution and MNPs biodegradation. The non-invasive and high-sensitivity scanning detection of MNPs in animals using ac susceptometry based on a high-T(c) superconducting quantum interference device (SQUID) is presented. The non-invasive results and biopsy results show good agreement, and two gold-standard biomedicine methods, Prussian blue stain and inductively coupled plasma, prove the magnetic results. This confirms that the future clinical diagnosis of bio-functional MNPs could be operated by using scanning SQUID biosusceptometry as conveniently as an ultrasonic probe.

  6. Microstructures and superconducting properties of Y-Ba-Cu and Bi-Sr-Ca-Cu oxide wires and coils prepared by the explosive compaction technique

    International Nuclear Information System (INIS)

    Hagino, S.; Suzuki, M.; Takeshita, T.; Takashima, K.; Tonda, H.

    1989-01-01

    It has been shown that explosive compaction technique can be used to densify metal, and ceramics powders and their mixtures. The authors discuss how they applied this technique to produce silver sheathed superconducting oxide wires and coils (Y-B-Cu-O and Bi-Sr-Ca-Cu-O). The wires and coils to be compacted were placed into metal tube and the tube was filled with SiC powder as a pressure propagating medium and the tube was compacted by a cylindrically axisymmetric method. The wires and coils compacted were then heat-treated in order to improve grain boundary connections of superconducting oxide crystalline grains. The oxide cores heat-treated were seen to be very dense, and a part of a Y-Ba-Cu oxide coil which was heat-treated optimally was found to have a critical current density higher than 13,000A/cm 2 at 77K

  7. Method of producing superconducting fibers of bismuth strontium calcium copper oxide (Bi(2212) and Bi(2223))

    Science.gov (United States)

    Schwartzkopf, Louis A.

    1991-10-01

    Fibers of Bi(2212) have been produce by pendant drop melt extraction. This technique involves the end of a rod of Bi(2212) melted with a hydrogen-oxygen torch, followed by lowering onto the edge of a spinning wheel. The fibers are up to 15 cm in length with the usual lateral dimensions, ranging from 20 um to 30 um. The fibers require a heat treatment to make them superconducting.

  8. Experimental investigations of superconductivity in quasi-two-dimensional epitaxial copper oxide superlattices and trilayers

    International Nuclear Information System (INIS)

    Lowndes, D.H.; Norton, D.P.

    1993-01-01

    Epitaxial trilayer and superlattice structures grown by pulsed laser ablation have been used to study the superconducting-to-normal transition of ultrathin (one and two c-axis unit cells) YBa 2 Cu 3 O 7-x layers. The normalized flux-flow resistances for several epitaxial structures containing two-cell-thick YBa 2 Cu 3 O 7-x films collapse onto the ''universal'' curve of the Ginzburg-Landau Coulomb Gas (GLCG) model. Analysis of normalized resistance data for a series of superlattices containing one-cell-thick YBa 2 Cu 3 O 7-x layers also is consistent with the behavior expected for quasi-two-dimensional layers in a highly anisotropic, layered three-dimensional superconductor. Current-voltage measurements for one of the trilayer structures also are consistent with the normalized resistance data, and with the GLCG model. Scanning tunneling microscopy, transmission electron microscopy, and electrical transport studies show that growth-related steps in ultrathin YBa 2 Cu 3 O 7-x layers affect electrical continuity over macroscopic distances, acting as weak links. However , the perturbation of the superconducting order parameter can be minimized by utilizing hole-doped buffer and cap layers, on both sides of the YBa 2 Cu 3 O 7-x layer, in trilayers and superlattices. These results demonstrate the usefulness of epitaxial trilayer and superlattice structures as tools for systematic, fundamental studies of high-temperature superconductivity

  9. Obtention of superconductivity by room temperature electrochemical oxidation of La2CuO4

    International Nuclear Information System (INIS)

    Casan-Pastor, N.; Fuertes, A.; Gomez-Romero, P.

    1993-01-01

    The undoped oxide La2CuO4 has required traditionally synthesis under high pressure of oxygen (and high temperatures) to incorporate excess oxygen into its structure and become a superconductor. The electrochemical oxidation of this same oxide at room temperature and pressure constitutes a striking example of the use of an alternative driving force for the oxidation of oxides to become superconductors. Electrochemical treatment of oxides has been frequently applied to their reduction with cationic intercalation. Oxidations of these solid with the concomitant intercalation of anions into their lattice shows also great promises. The paper reports recent results in the electrochemical oxidation of La2CuO4 and other cuprates, showing also the important role of post-oxidation thermal treatments on the properties of the resulting solids

  10. Superconductivity in power engineering

    International Nuclear Information System (INIS)

    1989-01-01

    This proceedings volume presents 24 conference papers and 15 posters dealing with the following aspects: 1) Principles and elementary aspects of high-temperature superconductivity (3 plenary lectures); 2) Preparation, properties and materials requirements of metallic or oxide superconductors (critical current behaviour, soldered joints, structural studies); 3) Magnet technology (large magnets for thermonuclear fusion devices; magnets for particle accelerators and medical devices); 4) Magnetic levitation and superconductivity; 5) Cryogenics; 6) Energy storage systems using superconducting coils (SMES); 7) Superconducting power transmission cables, switches, transformers, and generator systems for power plant; 8) Supporting activities, industrial aspects, patents. There are thirty-eight records in the ENERGY database relating to individual conference papers. (MM) [de

  11. Dependence of trapped-flux-induced surface resistance of a large-grain Nb superconducting radio-frequency cavity on spatial temperature gradient during cooldown through Tc

    Science.gov (United States)

    Huang, Shichun; Kubo, Takayuki; Geng, R. L.

    2016-08-01

    Recent studies by Romanenko et al. revealed that cooling down a superconducting cavity under a large spatial temperature gradient decreases the amount of trapped flux and leads to reduction of the residual surface resistance. In the present paper, the flux expulsion ratio and the trapped-flux-induced surface resistance of a large-grain cavity cooled down under a spatial temperature gradient up to 80 K /m are studied under various applied magnetic fields from 5 to 20 μ T . We show the flux expulsion ratio improves as the spatial temperature gradient increases, independent of the applied magnetic field: our results support and enforce the previous studies. We then analyze all rf measurement results obtained under different applied magnetic fields together by plotting the trapped-flux-induced surface resistance normalized by the applied magnetic field as a function of the spatial temperature gradient. All the data can be fitted by a single curve, which defines an empirical formula for the trapped-flux-induced surface resistance as a function of the spatial temperature gradient and applied magnetic field. The formula can fit not only the present results but also those obtained by Romanenko et al. previously. The sensitivity rfl of surface resistance from trapped magnetic flux of fine-grain and large-grain niobium cavities and the origin of d T /d s dependence of Rfl/Ba are also discussed.

  12. Motion stability of the magnetic levitation and suspension with YBa2Cu3O7-x high-Tc superconducting bulks and NdFeB magnets

    Science.gov (United States)

    Li, Jipeng; Zheng, Jun; Huang, Huan; Li, Yanxing; Li, Haitao; Deng, Zigang

    2017-10-01

    The flux pinning effect of YBa2Cu3O7-x high temperature superconducting (HTS) bulk can achieve self-stable levitation over a permanent magnet or magnet array. Devices based on this phenomenon have been widely developed. However, the self-stable flux pinning effect is not unconditional, under disturbances, for example. To disclose the roots of this amazing self-stable levitation phenomenon in theory, mathematical and mechanical calculations using Lyapunov's stability theorem and the Hurwitz criterion were performed under the conditions of magnetic levitation and suspension of HTS bulk near permanent magnets in Halbach array. It is found that the whole dynamical system, in the case of levitation, has only one equilibrium solution, and the singular point is a stable focus. In the general case of suspension, the system has two singular points: one is a stable focus, and the other is an unstable saddle. With the variation of suspension force, the two first-order singular points mentioned earlier will get closer and closer, and finally degenerate to a high-order singular point, which means the stable region gets smaller and smaller, and finally vanishes. According to the center manifold theorem, the high-order singular point is unstable. With the interaction force varying, the HTS suspension dynamical system undergoes a saddle-node bifurcation. Moreover, a deficient damping can also decrease the stable region. These findings, together with existing experiments, could enlighten the improvement of HTS devices with strong anti-interference ability.

  13. High-frequency properties of superconducting Y-Ba-Cu-oxide thin films

    International Nuclear Information System (INIS)

    Ramakrishnan, E.S.; Su, M.; Howng, W.

    1992-01-01

    rf and microwave properties of superconducting YBa 2 Cu 3 O 7-x thin films were measured and analyzed using a coplanar resonator structure. The films were developed by sequential electron-beam evaporation of the metals followed by postanneal processing. dc properties of the films were obtained from resistance-temperature and current-voltage measurements to evaluate the transition temperature and current densities. High-frequency properties were measured from 70 to 10 K and in the frequency range 1--3 GHz to determine the film characteristics as compared to pure copper films on the same substrates

  14. Flux pinning by voids in surface-oxidized superconducting niobium and vanadium

    International Nuclear Information System (INIS)

    Meij, G.P. van der.

    1984-01-01

    This thesis describes a study of flux pinning by small voids (roughly 10 nm) in the type II superconductors niobium and vanadium. These voids were created in rectangular foils (with typical dimensions of 30x3x0.2 mm) during an irradiation with fast neutrons in the High Flux Reactor at Petten at temperatures between 400 and 1000 0 C. The pinning force per unit volume is determined from the magnetic properties of the superconducting samples. The experiments were carried out in a slowly ramped magnetic field, as well as in a combination of a static and a much smaller alternating field. (Auth.)

  15. Superconducting Technology Assessment

    National Research Council Canada - National Science Library

    2005-01-01

    This Superconducting Technology Assessment (STA) has been conducted by the National Security Agency to address the fundamental question of a potential replacement for silicon complementary metal oxide semiconductor (CMOS...

  16. Novel interplay between high-Tc superconductivity and antiferromagnetism in Tl-Based Six-CuO2-layered cuprates. 205Tl- and 63Cu-NMR probes

    International Nuclear Information System (INIS)

    Mukuda, Hidekazu; Shiki, Nozomu; Kimoto, Naoki; Yashima, Mitsuharu; Kitaoka, Yoshio; Tokiwa, Kazuyasu; Iyo, Akira

    2016-01-01

    We report 63 Cu- and 205 Tl-NMR studies on six-layered (n = 6) high-T c superconducting (SC) cuprate TlBa 2 Ca 5 Cu 6 O 14+δ (Tl1256) with T c ∼ 100 K, which reveal that antiferromagnetic (AFM) order takes place below T N ∼ 170 K. In this compound, four underdoped inner CuO 2 planes [n(IP) = 4] sandwiched by two outer planes (OPs) are responsible for the onset of AFM order, whereas the nearly optimally-doped OPs responsible for the onset of bulk SC. It is pointed out that an increase in the out-of-plane magnetic interaction within an intra-unit-cell causes T N ∼ 45 K for Tl1245 with n(IP) = 3 to increase to ∼170 K for Tl1256 with n(IP) = 4. It is remarkable that the marked increase in T N and the AFM moments for the IPs does not bring about any reduction in T c , since T c ∼ 100 K is maintained for both compounds with nearly optimally doped OP. We highlight the fact that the SC order for n ≥ 5 is mostly dominated by the long-range in-plane SC correlation even in the multilayered structure, which is insensitive to the magnitude of T N and the AFM moments at the IPs or the AFM interaction among the IPs. These results demonstrate a novel interplay between the SC and AFM orders when the charge imbalance between the IPs and OP is significantly large. (author)

  17. Infrared studies of the superconducting energy gap and normal-state dynamics of the high-Tc superconductor YBa2Cu3O7

    International Nuclear Information System (INIS)

    Schlesinger, Z.; Collins, R.T.; Holtzberg, F.; Feild, C.; Koren, G.; Gupta, A.

    1990-01-01

    A detailed study of infrared properties (reflectivity, conductivity, and dielectric response), emphasizing reproducible results from fully oxygenated YBa 2 Cu 3 O 7 crystals (T c congruent 93 K) and films, is presented. The extrapolated values of σ 1 (ω) at low frequency are roughly consistent with the measured temperature-dependent dc resistivity. Although not well understood, this infrared conductivity can be interpreted in terms of a frequency-dependent scattering rate of ∼kT+ℎω, with a low-frequency mass enhancement of roughly 2 to 4 associated with a carrier-spin related interaction. Infrared measurements polarized along the c axis suggest a conductivity anisotropy of roughly 40:1 near T c in the normal state. In the superconducting state an energy scale of 2Δ c congruent 3kT c is suggested by c-axis polarized measurements, while a much larger characteristic energy of 2Δ a-b congruent 8kT c is evident in the (a-b)-plane conductivity. From the area missing from the conductivity up to this very large gap, a reasonable estimate (congruent 1700 A) for the (a-b)-plane penetration depth is obtained. Evidence for non-BCS temperature dependence, strong pair breaking scattering, and possible fluctuation effects is discussed. A comparison to infrared data from Bi 2 Sr 2 CaCu 2 O 8-y shows a similarly large energy scale, 2Δ a-b congruent 8kT c ; for the cubic Ba 0.6 K 0.4 BiO 3 superconductor a more conventional energy scale, 2Δ congruent 4kT c is observed

  18. The Role of −786T/C Polymorphism in the Endothelial Nitric Oxide Synthase Gene in Males with Clinical and Biochemical Features of the Metabolic Syndrome

    Directory of Open Access Journals (Sweden)

    Blazej Misiak

    2011-01-01

    Full Text Available Background. Extensive evidence, arising from models of endothelial nitric oxide synthase gene (NOS3-knockout mice supports the role of endothelial malfunction in the pathogenesis of the metabolic syndrome (MS. Aims. The aim of this study was to evaluate the role of −786T/C polymorphism in the etiology of MS and assess previously reported interaction with cigarette smoking. Methods. Based on International Diabetes Federation 2005 criteria, we recruited randomly 152 subjects with MS and 75 subjects without MS. Results. Allelic and genotype frequencies did not differ significantly between both groups. Total cholesterol level (CHOLT and intima-media thickness of carotid arteries were significantly higher in −786CC homozygotes, in comparison with −786TC and −786TT patients. Regarding current smoking status, −786C allele was associated with higher CHOLT than −786T allele. Conclusion. Our study indicates the putative role of −786T/C polymorphism in the development of hypercholesterolemia, in patients with MS, which might be enhanced by cigarette smoking.

  19. The Role of −786T/C Polymorphism in the Endothelial Nitric Oxide Synthase Gene in Males with Clinical and Biochemical Features of the Metabolic Syndrome

    Science.gov (United States)

    Misiak, Blazej; Krolik, Marta; Kukowka, Anna; Lewera, Anna; Leszczynski, Przemyslaw; Stankiewicz-Olczyk, Joanna; Slezak, Ryszard

    2011-01-01

    Background. Extensive evidence, arising from models of endothelial nitric oxide synthase gene (NOS3)-knockout mice supports the role of endothelial malfunction in the pathogenesis of the metabolic syndrome (MS). Aims. The aim of this study was to evaluate the role of −786T/C polymorphism in the etiology of MS and assess previously reported interaction with cigarette smoking. Methods. Based on International Diabetes Federation 2005 criteria, we recruited randomly 152 subjects with MS and 75 subjects without MS. Results. Allelic and genotype frequencies did not differ significantly between both groups. Total cholesterol level (CHOLT) and intima-media thickness of carotid arteries were significantly higher in −786CC homozygotes, in comparison with −786TC and −786TT patients. Regarding current smoking status, −786C allele was associated with higher CHOLT than −786T allele. Conclusion. Our study indicates the putative role of −786T/C polymorphism in the development of hypercholesterolemia, in patients with MS, which might be enhanced by cigarette smoking. PMID:22164159

  20. The Role of -786T/C Polymorphism in the Endothelial Nitric Oxide Synthase Gene in Males with Clinical and Biochemical Features of the Metabolic Syndrome.

    Science.gov (United States)

    Misiak, Blazej; Krolik, Marta; Kukowka, Anna; Lewera, Anna; Leszczynski, Przemyslaw; Stankiewicz-Olczyk, Joanna; Slezak, Ryszard

    2011-01-01

    Background. Extensive evidence, arising from models of endothelial nitric oxide synthase gene (NOS3)-knockout mice supports the role of endothelial malfunction in the pathogenesis of the metabolic syndrome (MS). Aims. The aim of this study was to evaluate the role of -786T/C polymorphism in the etiology of MS and assess previously reported interaction with cigarette smoking. Methods. Based on International Diabetes Federation 2005 criteria, we recruited randomly 152 subjects with MS and 75 subjects without MS. Results. Allelic and genotype frequencies did not differ significantly between both groups. Total cholesterol level (CHOLT) and intima-media thickness of carotid arteries were significantly higher in -786CC homozygotes, in comparison with -786TC and -786TT patients. Regarding current smoking status, -786C allele was associated with higher CHOLT than -786T allele. Conclusion. Our study indicates the putative role of -786T/C polymorphism in the development of hypercholesterolemia, in patients with MS, which might be enhanced by cigarette smoking.

  1. Electronic properties of high Tc superconductors

    International Nuclear Information System (INIS)

    Rojo, A.G.

    1989-01-01

    Using analytical and numerical methods, the electronic properties of the copper-oxygen plane in the normal phase of high Tc superconductors are described. Using the slave-boson technique in the saddle point, a theory of the metal insulator transition which generalizes the notions of a Mott insulator to the case of more than a single band for those planes is presented. A phase-diagram is obtained in the parameter space and effective masses, optical gaps and metallization are calculated as a function of the number of carriers. Based on the experimental evidence, the theory permits classification of superconducting compounds as charge transfer insulators in the stoichiometric case. The insulator state is characterized by a non-zero optical gap and a divergent effective mass which corresponds to the breakage of a Fermi-liquid scheme. The results obtained are applicable to metal-transition-oxides whose behaviour has been traditionally controversial and it is concluded that it is necessary to broaden the meaning of a Mott insulator to the case of more than a single band to better understand them. Based on the ideas of group renormalization in a real space, a lattice approximation is presented, which allows: a) To complement the treatment of slave-bosons in phase diagrams and optical gaps; b) Identification of an attraction mechanism between carriers originating from purely repulsive interactions. Numerical calculations in small clusters show the existence of a pairing mechanism showing a superconducting instability from a charge transfer insulator. (Author) [es

  2. Orbital Kondo effect due to assisted hopping: Superconductivity, mass enhancement in Cooper oxides with apical oxygen

    International Nuclear Information System (INIS)

    Zawadowski, A.; Penc, K.; Zimanyi, G.

    1991-07-01

    Orbital Kondo effect is treated in a model, where additional to the conduction band there are localized orbitals with energy not very far from the Fermi energy. If the hopping between the conduction band and the localized heavy orbitals depends on the occupation of the conduction band orbital then orbital Kondo correlation occurs. The assisted hopping vertex is enhanced due to the Coulomb interaction between the heavy orbital and the conduction band. The enhanced hopping results in mass enhancement and attractive interaction in the conduction band. The superconductivity transition temperature is calculated. The models of this type can be applied to the high-T c superconductors where the non-bonding oxygen orbitals of the apical oxygens play the role of heavy orbitals. For an essential range of the parameters the T c obtained is about 100K. (author). 22 refs, 9 figs

  3. Optical properties of copper-oxygen planes in superconducting oxides and related materials

    International Nuclear Information System (INIS)

    Kelly, M.K.; Barboux, P.; Tarascon, J.; Aspnes, D.E.

    1989-01-01

    The optical spectra of YBa 2 Cu 3 O 7-x and other Cu-O-based superconductors have several common features in the visible and near uv. Chemical changes that affect the conductivity of these materials also have a strong effect on some of these features. By comparing the spectra of many materials containing similar Cu-O structures, we have determined that some of the optical features are associated with specific local structures within the unit cell. Of particular interest is a sharp feature at 1.7 eV that appears for nonmetallic compositions of many of the materials and is removed by the introduction of carriers. Similar features in materials not yet showing superconductivity encourage further investigation of them

  4. Variable temperature superconducting microscope

    Science.gov (United States)

    Cheng, Bo; Yeh, W. J.

    2000-03-01

    We have developed and tested a promising type of superconducting quantum interference device (SQUID) microscope, which can be used to detect vortex motion and can operate in magnetic fields over a large temperature range. The system utilizes a single-loop coupling transformer, consisting of a patterned high Tc superconducting thin film. At one end of the transformer, a 20 μm diam detecting loop is placed close to the sample. At the other end, a large loop is coupled to a NbTi coil, which is connected to a low Tc SQUID sensor. Transformers in a variety of sizes have been tested and calibrated. The results show that the system is capable of detecting the motion of a single vortex. We have used the microscope to study the behavior of moving vortices at various positions in a YBa2Cu3O7 thin film bridge.

  5. Superconductivity and spin fluctuations

    International Nuclear Information System (INIS)

    Scalapino, D.J.

    1999-01-01

    The organizers of the Memorial Session for Herman Rietschel asked that the author review some of the history of the interplay of superconductivity and spin fluctuations. Initially, Berk and Schrieffer showed how paramagnon spin fluctuations could suppress superconductivity in nearly-ferromagnetic materials. Following this, Rietschel and various co-workers wrote a number of papers in which they investigated the role of spin fluctuations in reducing the Tc of various electron-phonon superconductors. Paramagnon spin fluctuations are also believed to provide the p-wave pairing mechanism responsible for the superfluid phases of 3 He. More recently, antiferromagnetic spin fluctuations have been proposed as the mechanism for d-wave pairing in the heavy-fermion superconductors and in some organic materials as well as possibly the high-Tc cuprates. Here the author will review some of this early history and discuss some of the things he has learned more recently from numerical simulations

  6. Theoretical analyses of superconductivity in iron based ...

    African Journals Online (AJOL)

    This paper focuses on the theoretical analysis of superconductivity in iron based superconductor Ba1−xKxFe2As2. After reviewing the current findings on this system, we suggest that phononexciton combined mechanism gives a right order of superconducting transition temperature (TC) for Ba1−xKxFe2As2 . By developing ...

  7. Applied superconductivity

    CERN Document Server

    Newhouse, Vernon L

    1975-01-01

    Applied Superconductivity, Volume II, is part of a two-volume series on applied superconductivity. The first volume dealt with electronic applications and radiation detection, and contains a chapter on liquid helium refrigeration. The present volume discusses magnets, electromechanical applications, accelerators, and microwave and rf devices. The book opens with a chapter on high-field superconducting magnets, covering applications and magnet design. Subsequent chapters discuss superconductive machinery such as superconductive bearings and motors; rf superconducting devices; and future prospec

  8. Alternating current loss characteristics in (bismuth,lead)SCCO and yttrium barium copper oxide superconducting tapes

    Science.gov (United States)

    Nguyen, Doan Ngoc

    Alternating current (AC) loss and current carrying capacity are two of the most crucial considerations in large-scale power applications of high temperature superconducting (HTS) conductors. AC losses result in an increased thermal load for cooling machines, and thus increased operating costs. Furthermore, AC losses can stimulate quenching phenomena or at least decrease the stability margin for superconducting devices. Thus, understanding AC losses is essential for the development of HTS AC applications. The main focus of this dissertation is to make reliable total AC loss measurements and interpret the experimental results in a theoretical framework. With a specially designed magnet, advanced total AC loss measurement system in liquid nitrogen (77 K) has been successfully built. Both calorimetric and electromagnetic methods were employed to confirm the validity of the measured results and to have a more thorough understanding of AC loss in HTS conductors. The measurement is capable of measuring total AC loss in HTS tapes over a wide range of frequency and amplitude of transport current and magnetic field. An accurate phase control technique allows measurement of total AC loss with any phase difference between the transport current and magnetic field by calorimetric method. In addition, a novel total AC loss measurement system with variable temperatures from 30 K to 100 K was successfully built and tested. Understanding the dependence of AC losses on temperature will enable optimization of the operating temperature and design of HTS devices. As a part of the dissertation, numerical calculations using Brandt's model were developed to study electrodynamics and total AC loss in HTS conductors. In the calculations, the superconducting electrical behavior is assumed to follow a power-law model. In general, the practical properties of conductors, including field-dependence of critical current density Jc, n-value and non-uniform distribution of Jc, can be accounted for in

  9. Electrochemistry of high-tc superconductors

    International Nuclear Information System (INIS)

    Petrij, O.A.; Tsirlina, G.A.

    1993-01-01

    The review deals with the problems of formation of a new section in modern electrochemistry related to various electrochemical aspects of high-temperature superconductivity. Specific properties of multicomponent oxides as electrode materials are pointed out. The data of experimental works on the study of degradation of superconducting ceramics, electroanalysis of complex oxide systems, electric deposition of metals and polymer films upon them are described. Special attention is paid to electrochemical approaches to electrosynthesis of films, possessing high-temperature superconductivity

  10. Dynamics of correlation-frozen antinodal quasiparticles in superconducting cuprates

    Science.gov (United States)

    Cilento, Federico; Manzoni, Giulia; Sterzi, Andrea; Peli, Simone; Ronchi, Andrea; Crepaldi, Alberto; Boschini, Fabio; Cacho, Cephise; Chapman, Richard; Springate, Emma; Eisaki, Hiroshi; Greven, Martin; Berciu, Mona; Kemper, Alexander F.; Damascelli, Andrea; Capone, Massimo; Giannetti, Claudio; Parmigiani, Fulvio

    2018-01-01

    Many puzzling properties of high–critical temperature (Tc) superconducting (HTSC) copper oxides have deep roots in the nature of the antinodal quasiparticles, the elementary excitations with wave vector parallel to the Cu–O bonds. These electronic states are most affected by the onset of antiferromagnetic correlations and charge instabilities, and they host the maximum of the anisotropic superconducting gap and pseudogap. We use time-resolved extreme-ultraviolet photoemission with proper photon energy (18 eV) and time resolution (50 fs) to disclose the ultrafast dynamics of the antinodal states in a prototypical HTSC cuprate. After photoinducing a nonthermal charge redistribution within the Cu and O orbitals, we reveal a dramatic momentum-space differentiation of the transient electron dynamics. Whereas the nodal quasiparticle distribution is heated up as in a conventional metal, new quasiparticle states transiently emerge at the antinodes, similarly to what is expected for a photoexcited Mott insulator, where the frozen charges can be released by an impulsive excitation. This transient antinodal metallicity is mapped into the dynamics of the O-2p bands, thus directly demonstrating the intertwining between the low- and high-energy scales that is typical of correlated materials. Our results suggest that the correlation-driven freezing of the electrons moving along the Cu–O bonds, analogous to the Mott localization mechanism, constitutes the starting point for any model of high-Tc superconductivity and other exotic phases of HTSC cuprates. PMID:29507885

  11. Theoretical band structure of the superconducting antiperovskite oxide Sr3-xSnO

    Science.gov (United States)

    Ikeda, Atsutoshi; Fukumoto, Toshiyuki; Oudah, Mohamed; Hausmann, Jan Niklas; Yonezawa, Shingo; Kobayashi, Shingo; Sato, Masatoshi; Tassel, Cédric; Takeiri, Fumitaka; Takatsu, Hiroshi; Kageyama, Hiroshi; Maeno, Yoshiteru

    2018-05-01

    In order to investigate the position of the strontium deficiency in superconductive Sr3-xSnO, we synthesized and measured X-ray-diffraction patterns of Sr3-xSnO (x ∼ 0.5). Because no clear peaks originating from superstructures were observed, strontium deficiency is most likely to be randomly distributed. We also performed first-principles band-structure calculations on Sr3-xSnO (x = 0, 0.5) using two methods: full-potential linearized-augmented plane-wave plus local orbitals method and the Korringa-Kohn-Rostoker Green function method combined with the coherent potential approximation. We revealed that the Fermi energy of Sr3-xSnO in case of x ∼ 0.5 is about 0.8 eV below the original Fermi energy of the stoichiometric Sr3SnO, where the mixing of the valence p and conduction d orbitals are considered to be small.

  12. CO2-laser ablation of Bi-Sr-Ca-Cu oxide by millisecond pulse lengths

    Science.gov (United States)

    Meskoob, M.; Honda, T.; Safari, A.; Wachtman, J. B.; Danforth, S.; Wilkens, B. J.

    1990-03-01

    We have achieved ablation of Bi-Sr-Ca-Cu oxide from single targets of superconducting pellets by CO2-laser pulses of l ms length to grow superconducting thin films. Upon annealing, the 6000-Å thin films have a Tc (onset) of 90 K and zero resistance at 78 K. X-ray diffraction patterns indicate the growth of single-phase thin films. This technique allows growth of uniform single-phase superconducting thin films of lateral area greater than 1 cm2.

  13. Effects of weak magnetic fields on post-implantation damage in superconducting oxides

    International Nuclear Information System (INIS)

    Khait, Y.L.

    1996-01-01

    Experimentally verifiable effects of weak permanent magnetic fields (PMF's) acting during ion implantation in high-T c superconducting (HTSC) materials at T∼300 K on post-implantation damage (PID) and material parameters are considered. The presence of PMF's of H∼10 3 Oe during ion implantation can enlarge substantially the PID in HTSC materials implanted with ions of moderate energies (e.g. 200-400 keV) and dosage (10 11- 10 12 cm -3 ) at room temperature. The PMF-induced increase in the radiation damage causes the corresponding enhancement in the material resistivity R and reduction in the critical current j cir (measured after the cooling of the HTSC material down to T (L) c after the ion implantation). This is an extension of the PMF effects found experimentally (and explained theoretically) in semiconductors in our previous work. The experimentally verifiable PMF effects on the defect (atomic) migration and radiation damage is a generic consequence of the kinetic electron-related theory of atomic rate processes in solids. The theory links the PMF effects with electron transitions occurring in the nanometer vicinity of atoms overcoming energy barriers which affect exponentially rates of atomic (defect) diffusion. The magnetic field can enhance the number of downward electron transitions that accompany atomic (defect) jumps over energy barriers and synchronize with the jumps. This enhances exponentially the rates of defect migration out of thermal spikes that prevents the defects from fast recombination, and thus, the PMF increases the PID and changes correspondingly R and j cir . (orig.)

  14. Advances in superconducting materials and electronics technologies

    International Nuclear Information System (INIS)

    Palmer, D.N.

    1990-01-01

    Technological barriers blocking the early implementation of ceramic oxide high critical temperature [Tc] and LHe Nb based superconductors are slowly being dismantled. Spearheading these advances are mechanical engineers with diverse specialties and creative interests. As the technology expands, most engineers have recognized the importance of inter-disciplinary cooperation. Cooperation between mechanical engineers and material and system engineers is of particular importance. Recently, several problems previously though to be insurmountable, has been successfully resolved. These accomplishment were aided by interaction with other scientists and practitioners, working in the superconductor research and industrial communities, struggling with similar systems and materials problems. Papers published here and presented at the 1990 ASME Winter Annual Meeting held in Dallas, Texas 25-30 November 1990 can be used as a bellwether to gauge the progress in the development of both ceramic oxide and low temperature Nb superconducting device and system technologies. Topics are focused into two areas: mechanical behavior of high temperature superconductors and thermal and mechanical problems in superconducting electronics

  15. Effects of extra oxygen on the structure and superconductivity of La2-xCaxCuO4+y prepared by chemical oxidation

    DEFF Research Database (Denmark)

    Rial, C.; Moran, E.; Alario Franco, M.A.

    1998-01-01

    are strongly conditioned by the smaller size of Ca2+ with respect to La3+. Indeed, this peculiarity clearly differentiates the oxidized La2-xCaxCuO4+y series from the Sr2+ and the Ba2+ substituted systems, where the size of the dopant is larger than that of La3+. In the present work the analogies...... and the differences concerning the insertion of oxygen and the modifications induced in La2-xMxCuO4+y (M = Ca, Sr, Ba) are presented and discussed. (C) 1998 Elsevier Science B.V....... improve considerably upon oxidation. The oxidized Ca-doped materials with x less than or equal to 0.08 show an almost constant T-c of similar to 38 K, close to that corresponding to the optimum hole-doping in La2-xMxCuO4; however, the oxidized samples with higher Ca contents present slightly lower T...

  16. High-Tc superconductor applications

    International Nuclear Information System (INIS)

    Anon.

    1988-01-01

    There has been much speculation about new products and business opportunities which high-Tc superconductors might make possible. However, with the exception of one Japanese survey, there have not been any recognized forecasts suggesting a timeframe and relative economic impact for proposed high-Tc products. The purpose of this survey is to provide definitive projections of the timetable for high-Tc product development, based on the combined forecasts of the leading U.S. superconductivity experts. The FTS panel of experts on high-Tc superconductor applications, representing both business and research, forecast the commercialization and economic impact for 28 classes of electronic, magnetic, communications, instrumentation, transportation, industrial, and power generation products. In most cases, forecasts predict the occurrence of developments within a 90% statistical confidence limit of 2-to-3 years. The report provides background information on the 28 application areas, as well as other information useful for strategic planners. The panel also forecast high-Tc research spending, markets, and international competitiveness, and provide insight into how the industry will evolve

  17. SPIN SUSCEPTIBILITY IN HIGH - TC SUPERCONDUCTIVITY

    African Journals Online (AJOL)

    USER

    2012-07-05

    Jul 5, 2012 ... remains unchanged as a result of which the oxygen site will remain deficient ... kinetic energy, a hole's spin hooks up with the random Cu moment to form a ... reach out to each other magnetically to form spin singlet pairs with ...

  18. Superconductivity applications for infrared and microwave devices; Proceedings of the Meeting, Orlando, FL, Apr. 19, 20, 1990

    Science.gov (United States)

    Bhasin, Kul B.; Heinen, Vernon O.

    1990-10-01

    Various papers on superconductivity applications for IR and microwave devices are presented. The individual topics addressed include: pulsed laser deposition of Tl-Ca-Ba-Cu-O films, patterning of high-Tc superconducting thin films on Si substrates, IR spectra and the energy gap in thin film YBa2Cu3O(7-delta), high-temperature superconducting thin film microwave circuits, novel filter implementation utilizing HTS materials, high-temperature superconductor antenna investigations, high-Tc superconducting IR detectors, high-Tc superconducting IR detectors from Y-Ba-Cu-O thin films, Y-Ba-Cu0-O thin films as high-speed IR detectors, fabrication of a high-Tc superconducting bolometer, transition-edge microbolometer, photoresponse of YBa2Cu3O(7-delta) granular and epitaxial superconducting thin films, fast IR response of YBCO thin films, kinetic inductance effects in high-Tc microstrip circuits at microwave frequencies.

  19. Lighting up superconducting stripes

    Science.gov (United States)

    Ergeçen, Emre; Gedik, Nuh

    2018-02-01

    Cuprate superconductors display a plethora of complex phases as a function of temperature and carrier concentration, the understanding of which could provide clues into the mechanism of superconductivity. For example, when about one-eighth of the conduction electrons are removed from the copper oxygen planes in cuprates such as La2‑xBaxCuO4 (LBCO), the doped holes (missing electrons) organize into one-dimensional stripes (1). The bulk superconducting transition temperature (Tc) is greatly reduced, and just above Tc, electrical transport perpendicular to the planes (along the c axis) becomes resistive, but parallel to the copper oxygen planes, resistivity remains zero for a range of temperatures (2). It was proposed a decade ago (3) that this anisotropic behavior is caused by pair density waves (PDWs); superconducting Cooper pairs exist along the stripes within the planes but cannot tunnel to the adjacent layers. On page 575 of this issue, Rajasekaran et al. (4) now report detection of this state in LBCO using nonlinear reflection of high-intensity terahertz (THz) light.

  20. Possible influence of surface oxides on the optical response of high-purity niobium material used in the fabrication of superconducting radio frequency cavity

    Science.gov (United States)

    Singh, Nageshwar; Deo, M. N.; Roy, S. B.

    2016-09-01

    We have investigated the possible influence of surface oxides on the optical properties of a high-purity niobium (Nb) material for fabrication of superconducting radio frequency (SCRF) cavities. Various peaks in the infrared region were identified using Fourier transform infrared and Raman spectroscopy. Optical response functions such as complex refractive index, dielectric and conductivity of niobium were compared with the existing results on oxides free Nb and Cu. It was observed that the presence of a mixture of niobium-oxides, and probably near other surface impurities, appreciably influence the conducting properties of the material causing deviation from the typical metallic characteristics. In this way, the key result of this work is the observation, identification of vibrational modes of some of surface complexes and study of its influences on the optical responses of materials. This method of spectroscopic investigation will help in understanding the origin of degradation of performance of SCRF cavities.

  1. Possible influence of surface oxides on the optical response of high-purity niobium material used in the fabrication of superconducting radio frequency cavity

    International Nuclear Information System (INIS)

    Singh, Nageshwar; Deo, M.N.; Roy, S.B.

    2016-01-01

    We have investigated the possible influence of surface oxides on the optical properties of a high-purity niobium (Nb) material for fabrication of superconducting radio frequency (SCRF) cavities. Various peaks in the infrared region were identified using Fourier transform infrared and Raman spectroscopy. Optical response functions such as complex refractive index, dielectric and conductivity of niobium were compared with the existing results on oxides free Nb and Cu. It was observed that the presence of a mixture of niobium-oxides, and probably near other surface impurities, appreciably influence the conducting properties of the material causing deviation from the typical metallic characteristics. In this way, the key result of this work is the observation, identification of vibrational modes of some of surface complexes and study of its influences on the optical responses of materials. This method of spectroscopic investigation will help in understanding the origin of degradation of performance of SCRF cavities.

  2. Possible influence of surface oxides on the optical response of high-purity niobium material used in the fabrication of superconducting radio frequency cavity

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Nageshwar [Magnetic and Superconducting Materials Section, Raja Ramanna Centre for Advanced Technology, Indore 452013, M.P. (India); Deo, M.N. [High Pressure & Synchrotron Radiation Physics Division, BARC, Mumbai 400085 (India); Roy, S.B. [Magnetic and Superconducting Materials Section, Raja Ramanna Centre for Advanced Technology, Indore 452013, M.P. (India)

    2016-09-11

    We have investigated the possible influence of surface oxides on the optical properties of a high-purity niobium (Nb) material for fabrication of superconducting radio frequency (SCRF) cavities. Various peaks in the infrared region were identified using Fourier transform infrared and Raman spectroscopy. Optical response functions such as complex refractive index, dielectric and conductivity of niobium were compared with the existing results on oxides free Nb and Cu. It was observed that the presence of a mixture of niobium-oxides, and probably near other surface impurities, appreciably influence the conducting properties of the material causing deviation from the typical metallic characteristics. In this way, the key result of this work is the observation, identification of vibrational modes of some of surface complexes and study of its influences on the optical responses of materials. This method of spectroscopic investigation will help in understanding the origin of degradation of performance of SCRF cavities.

  3. Superconductivity - applications

    International Nuclear Information System (INIS)

    The paper deals with the following subjects: 1) Electronics and high-frequency technology, 2) Superconductors for energy technology, 3) Superconducting magnets and their applications, 4) Electric machinery, 5) Superconducting cables. (WBU) [de

  4. Influence of various parameters on the elaboration of superconducting oxides. Influence de divers parametres sur la synthese d'oxydes supraconducteurs

    Energy Technology Data Exchange (ETDEWEB)

    Remy, F; Monnereau, O; Vacquier, G; Sorbier, J P; Fournel, A [Aix-Marseille-1 Univ., 13 - Marseille (FR); Mokrani, R [Aix-Marseille-3 Univ., 13 - Marseille (FR)

    1989-01-01

    Several oxides able to give rise to a high T{sub c} superconductivity have been studied. Samples were prepared in both series: La(Ba{sub 2-x}La{sub x}) Cu{sub 3}O{sub 7+y} and YBa{sub 2} (Cu{sub 3-x}Ag{sub x})O{sub 7-y}. The evolution of the resistance versus the composition has been studied on sintered samples. The results assess the importance of the experimental conditions of the synthesis. In the system La(Ba{sub 2-x}La{sub x})Cu{sub 3}O{sub 7+y} our results complete the work of Segre et al. and precise composition at which the superconductivity transition disappear for the profit of the semiconductive behaviour. The samples YBa{sub 2}(Cu{sub 3-x}Ag{sub x})O{sub 7-y} has for x = 0 electrical properties very dependent of the thermal treatment. Some characteristic data are shown. The partial substitution of Cu by Ag for x {ge} 1 enables to keep the superconducting behaviour.

  5. Superconductivity in bundles of double-wall carbon nanotubes.

    Science.gov (United States)

    Shi, Wu; Wang, Zhe; Zhang, Qiucen; Zheng, Yuan; Ieong, Chao; He, Mingquan; Lortz, Rolf; Cai, Yuan; Wang, Ning; Zhang, Ting; Zhang, Haijing; Tang, Zikang; Sheng, Ping; Muramatsu, Hiroyuki; Kim, Yoong Ahm; Endo, Morinobu; Araujo, Paulo T; Dresselhaus, Mildred S

    2012-01-01

    We present electrical and thermal specific heat measurements that show superconductivity in double-wall carbon nanotube (DWCNT) bundles. Clear evidence, comprising a resistance drop as a function of temperature, magnetoresistance and differential resistance signature of the supercurrent, suggest an intrinsic superconducting transition below 6.8 K for one particular sample. Additional electrical data not only confirm the existence of superconductivity, but also indicate the T(c) distribution that can arise from the diversity in the diameter and chirality of the DWCNTs. A broad superconducting anomaly is observed in the specific heat of a bulk DWCNT sample, which yields a T(c) distribution that correlates well with the range of the distribution obtained from the electrical data. As quasi one dimensionality of the DWCNTs dictates the existence of electronic density of state peaks, confirmation of superconductivity in this material system opens the exciting possibility of tuning the T(c) through the application of a gate voltage.

  6. A new way for preparing superconducting materials: the electrochemical oxidation of La sub 2 CuO sub 4. Une nouvelle voie d'acces aux oxydes supraconducteurs: l'oxydation electrochimique de La sub 2 CuO sub 4

    Energy Technology Data Exchange (ETDEWEB)

    Wattiaux, A; Park, J C; Grenier, J C; Pouchard, M [Bordeaux-1 Univ., 33 - Talence (FR)

    1990-04-01

    The electrochemical oxidation in alkaline medium is described as a new way for preparing superconducting oxides at room temperature. The application of this method to La{sub 2}CuO{sub 4} gave rise to a metallic material with a superconducting behaviour below 39 K and whose physical and chemical features appear as quite promising.

  7. Superconductivity and fast proton transport in nanoconfined water

    Science.gov (United States)

    Johnson, K. H.

    2018-04-01

    A real-space molecular-orbital density-wave description of Cooper pairing in conjunction with the dynamic Jahn-Teller mechanism for high-Tc superconductivity predicts that electron-doped water confined to the nanoscale environment of a carbon nanotube or biological macromolecule should superconduct below and exhibit fast proton transport above the transition temperature, Tc ≅ 230 K (-43 °C).

  8. A universal order underlying the pseudogap regime of the underdoped high Tc cuprates

    Science.gov (United States)

    Harrison, Neil

    2014-03-01

    A major achievement in condensed matter physics in the last quarter century has been a step towards the understanding of the unconventional d-wave superconducting state in the copper-oxide materials. Surprisingly, the normal state out of which the superconducting state emerges remains a mystery at low charge carrier densities, i.e., in the underdoped regime. This regime is of particular interest because it is characterised by an unusual momentum dependent energy pseudogap in the excitation spectrum that has defied explanation and is key to a full understanding of the unconventional d-wave superconducting state. I will present new quantum oscillation experimental results within the pseudogap regime of the high Tc superconductors YBa2Cu3O6+x and YBa2Cu4O8 which now extend up to the optimally-doped regime. These data reveal the evolution of the Fermi surface approaching the putative quantum critical point under the superconducting dome. A comprehensive angle-resolved study of the Fermi surface enables us to unambiguously identify a specific form of order that accounts for the observed quantum oscillations as well as other spectroscopic, transport and thermodynamic probes within the pseudogap regime. The author would like to thank B. Ramshaw, S. Sebastian, F. Balakirev, C. Mielke, M. Altarawneh, P. Goddard, S. Sabok, B. Babrowski, D. Bonn, W. Hardy, R. Liang and G. Lonzarich. This work was supported by the DOE BES ``Science of 100 tesla'' project and by the NSF and Florida State.

  9. What is the role of Pb(II) in high Tc superconductors

    International Nuclear Information System (INIS)

    Raveau, B.; Hervieu, M.; Michel, C.; Groult, D.; Provost, J.

    1990-01-01

    An overview of the layered lead cuprates is presented here. The structure of these oxides and their non-stoichiometry are studied in connection with their superconducting properties. The phenomena involving a modulation of the structure, characterized by the presence of satellites on E.D. patterns are described and the particular role of the 6s 2 lone pair of Pb(II) is discussed. Divalent lead is, owing to its size intermediate between that of strontium and barium, a potential cation for superconductive cuprates. Moreover, this interest for Pb(II), is supported by its electronic structure which involves an electronic 6s 2 lone pair well known for its ability to form layered structures. In spite of these characteristics, few superconductive layered suprates were isolated at the beginning of the rush to high Tc superconductors. This is probably due to the possibility of existence of redox reactions involving the couple Pb(II)/Pb(IV), which require very particular experimental conditions. The authors report here on the recent development of the crystal chemistry of those materials and on their corresponding superconducting properties

  10. Electron density distribution in BaPb1−xSbxO3 superconducting oxides studied by double nuclear magnetic resonance methods

    International Nuclear Information System (INIS)

    Piskunov, Yu. V.; Ogloblichev, V. V.; Arapova, I. Yu.; Sadykov, A. V.; Gerashchenko, A. P.; Verkhovskii, S. V.

    2011-01-01

    The effect of charge disorder on the formation of an inhomogeneous state of the electron system in the conduction band in BaPb 1−x Sb x O 3 superconducting oxides is investigated experimentally by NMR methods. The NMR spectra of 17 O are measured systematically, and the contributions from 17 O atoms with different cation nearest surroundings are identified. It is found that microscopic regions with an elevated spin density of charge carriers are formed within two coordination spheres near antimony ions. Nuclei of the superconducting phase of the oxide (regions with an elevated antimony concentration) microscopically distributed over the sample are detected in compounds with x = 0.25 and 0.33. Experiments in which a double resonance signal of the spin echo of 17 O- 207 Pb and 17 O- 121 Sb are measured in the metal phase of BaPb 1−x Sb x O 3 oxides are carried out for the first time. The constants of indirect heteronuclear spin-spin 17 O- 207 Pb interaction are determined as functions of the local Knight shift 207 Ks. The estimates of the constants of the indirect interaction between the nuclei of the nearest neighbors (O-Pb and Pb-Pb atoms) and analysis of evolution of the NMR spectra of 17 O upon a change in the antimony concentration are convincing evidence in favor of the development of a microscopically inhomogeneous state of the electron system in the metal phase of BaPb 1−x Sb x O 3 oxides.

  11. Superconductivity in single wall carbon nanotubes

    Directory of Open Access Journals (Sweden)

    H Yavari

    2009-08-01

    Full Text Available   By using Greens function method we first show that the effective interaction between two electrons mediated by plasmon exchange can become attractive which in turn can lead to superconductivity at a high critical temperature in a singl wall carbon nanotubes (SWCNT. The superconducting transition temperature Tc for the SWCNT (3,3 obtained by this mechanism agrees with the recent experimental result. We also show as the radius of SWCNT increases, plasmon frequency becomes lower and leads to lower Tc.

  12. Soil-to-plant transfer of 99mTc: how to determine Tc-species in uptake and transport processes?

    International Nuclear Information System (INIS)

    Krijger, G. C.; Van Elswijk, D. A.; Wolterbeek, H. Th.

    1995-01-01

    Selective extraction, filtration and capillary electrophoresis were used to recognize problems dealing with complexation, oxidation and ligand-exchange processes during collection and analysis of Tc-species in xylem exudates, while 99m Tc-citrate was used as a marker complex. Relatively unstable Tc-species were synthesized in xylem exudates. Oxidation of relative unstable Tc-species during the collection of xylem exudates was suggested, requiring new, better procedures to recognize Tc-species representative for the plant interior. (author)

  13. Influence of KMnO4 Concentrationon Infrared Emissivity of Coatings Formed on TC4 Alloys by Micro-Arc Oxidation

    Science.gov (United States)

    Li, Ying; Li, Chaozhong; Hu, Dan; Li, Zhengxian; Xi, Zhengping

    2017-01-01

    Ceramic coatings with high emissivity were fabricated on TC4 alloys by micro-arc oxidation technique (MAO) in mixed silicate and phosphate electrolytes with varying KMnO4 addition. The microstructure, phase and chemical composition were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS), and the infrared emissivity of the MAO coatings was measured in a waveband of 5–20 μm. The results show that the thickness of the coatings increased with the addition of KMnO4, but the roughness of the coatings first decreased and then increased slightly due to the inhibitory effect of KMnO4 on Na2SiO3 deposition. The main phase composition of the coatings was anatase and rutile TiO2, amorphous form of SiO2 and MnO2. The infrared emissivity value of the coatings strongly depended on KMnO4 concentration, the coating formed at the concentration of 0.8 g/L KMnO4 reached the highest and an average of up to 0.87 was observed. PMID:29137192

  14. Magnetic order close to superconductivity in the iron-based layered LaO1-xFxFeAs systems

    Science.gov (United States)

    de La Cruz, Clarina; Huang, Q.; Lynn, J. W.; Li, Jiying; , W. Ratcliff, II; Zarestky, J. L.; Mook, H. A.; Chen, G. F.; Luo, J. L.; Wang, N. L.; Dai, Pengcheng

    2008-06-01

    Following the discovery of long-range antiferromagnetic order in the parent compounds of high-transition-temperature (high-Tc) copper oxides, there have been efforts to understand the role of magnetism in the superconductivity that occurs when mobile `electrons' or `holes' are doped into the antiferromagnetic parent compounds. Superconductivity in the newly discovered rare-earth iron-based oxide systems ROFeAs (R, rare-earth metal) also arises from either electron or hole doping of their non-superconducting parent compounds. The parent material LaOFeAs is metallic but shows anomalies near 150K in both resistivity and d.c. magnetic susceptibility. Although optical conductivity and theoretical calculations suggest that LaOFeAs exhibits a spin-density-wave (SDW) instability that is suppressed by doping with electrons to induce superconductivity, there has been no direct evidence of SDW order. Here we report neutron-scattering experiments that demonstrate that LaOFeAs undergoes an abrupt structural distortion below 155K, changing the symmetry from tetragonal (space group P4/nmm) to monoclinic (space group P112/n) at low temperatures, and then, at ~137K, develops long-range SDW-type antiferromagnetic order with a small moment but simple magnetic structure. Doping the system with fluorine suppresses both the magnetic order and the structural distortion in favour of superconductivity. Therefore, like high-Tc copper oxides, the superconducting regime in these iron-based materials occurs in close proximity to a long-range-ordered antiferromagnetic ground state.

  15. Effective valence as the control parameter of the superconducting ...

    African Journals Online (AJOL)

    One approach to investigating the superconductivity in the ironbased materials is understanding the chemical and structural parameters that can be used to tune their remarkably high Tc. In this paper, we have demonstrated that the effective valence of iron can be used as the control parameter to tune the Tc of this family of ...

  16. Syntheses of the Bi(Pb)-2212 high-Tc superconductor through a novel oxide nitrate route

    International Nuclear Information System (INIS)

    Gibson, K; Ziegler, P; Meyer, H-J

    2004-01-01

    A novel route is presented for the syntheses of Bi 2 Sr 2 CaCu 2 O x (Bi-2212) and (Bi,Pb) 2 Sr 2 CaCu 2 O x (Bi,Pb-2212). Mixtures of oxides, nitrates and carbonates with approximate 2:2:1:2 metal ion compositions are dissolved in HNO 3 and dried at 200 deg. C in air. Afterwards they are reacted under their in situ generated NO x atmosphere in a closed reactor (Staurohr). This reaction forces the system to form the nitrate precursors (Bi,Sr,Ca) 2 O 2 NO 3 /CuO and (Bi,Pb,Sr,Ca) 2 O 2 NO 3 /CuO, respectively. In the final reaction stage these mixtures are converted into Bi(Pb)-2212 under NO x discharge in air. All important reaction stages and phase compositions are analysed by means of powder XRD

  17. Superconducting Electronic Film Structures

    Science.gov (United States)

    1991-02-14

    Segmuller, A., Cooper, E.I., Chisholm, M.F., Gupta, A. Shinde, S., and Laibowitz, R.B. Lanthanum gallate substrates for epitaxial high-T superconducting thin...M. F. Chisholm, A. Gupta, S. Shinde, and R. B. Laibowitz, " Lanthanum Gallate Substrates for Epitaxial High-T c Superconducting Thin Films," Appl...G. Forrester and J. Talvacchio, " Lanthanum Copper Oxide Buffer Layers for Growth of High-T c Superconductor Films," Disclosure No. RDS 90-065, filed

  18. Superconductivity in doped semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Bustarret, E., E-mail: Etienne.bustarret@neel.cnrs.fr

    2015-07-15

    A historical survey of the main normal and superconducting state properties of several semiconductors doped into superconductivity is proposed. This class of materials includes selenides, tellurides, oxides and column-IV semiconductors. Most of the experimental data point to a weak coupling pairing mechanism, probably phonon-mediated in the case of diamond, but probably not in the case of strontium titanate, these being the most intensively studied materials over the last decade. Despite promising theoretical predictions based on a conventional mechanism, the occurrence of critical temperatures significantly higher than 10 K has not been yet verified. However, the class provides an enticing playground for testing theories and devices alike.

  19. Superconductivity revisited

    CERN Document Server

    Dougherty, Ralph

    2013-01-01

    While the macroscopic phenomenon of superconductivity is well known and in practical use worldwide in many industries, including MRIs in medical diagnostics, the current theoretical paradigm for superconductivity (BCS theory) suffers from a number of limitations, not the least of which is an adequate explanation of high temperature superconductivity. This book reviews the current theory and its limitations and suggests new ideas and approaches in addressing these issues. The central objective of the book is to develop a new, coherent, understandable theory of superconductivity directly based on molecular quantum mechanics.

  20. {mu}SR studies of the interplay of magnetic spin stripe order with superconductivity in transition metal oxides

    Energy Technology Data Exchange (ETDEWEB)

    Klauss, Hans-Henning, E-mail: h.klauss@physik.tu-dresden.de [Institute for Solid State Physics, TU Dresden, D-01069 Dresden (Germany)

    2012-11-01

    In this work we review muon spin relaxation experiments on the layered La{sub 2-x}Sr{sub x}NiO{sub 4} nickelate as well as La{sub 2-x}Ba{sub x}CuO{sub 4} and La{sub 2-x}Sr{sub x}CuO{sub 4} cuprate systems to examine spin stripe order. In particular, the interplay of stripe order with superconductivity in Nd and Eu doped La{sub 2-x}Sr{sub x}CuO{sub 4} cuprates is discussed. Detailed studies of the electronic phase diagrams as well as the magnetic and superconducting order parameters for different rare-earth and Sr doping levels in La{sub 2-x-y}RE{sub y}Sr{sub x}CuO{sub 4} revealed the strong correlation of static spin stripe order with the structural distortion in the low temperature tetragonal (LTT) phase and the competition with the superconducting ground state. High magnetic field studies demonstrate the nearly degenerate ground state energy of the different electronic phases. Slow transverse fluctuations of the charge stripes are found in nickelates and cuprates at low temperatures.

  1. Superconductivity in compensated and uncompensated semiconductors

    Directory of Open Access Journals (Sweden)

    Youichi Yanase and Naoyuki Yorozu

    2008-01-01

    Full Text Available We investigate the localization and superconductivity in heavily doped semiconductors. The crossover from the superconductivity in the host band to that in the impurity band is described on the basis of the disordered three-dimensional attractive Hubbard model for binary alloys. The microscopic inhomogeneity and the thermal superconducting fluctuation are taken into account using the self-consistent 1-loop order theory. The superconductor-insulator transition accompanies the crossover from the host band to the impurity band. We point out an enhancement of the critical temperature Tc around the crossover. Further localization of electron wave functions leads to the localization of Cooper pairs and induces the pseudogap. We find that both the doping compensation by additional donors and the carrier increase by additional acceptors suppress the superconductivity. A theoretical interpretation is proposed for the superconductivity in the boron-doped diamond, SiC, and Si.

  2. Rugged Low-Resistance Contacts To High-Tc Superconductors

    Science.gov (United States)

    Caton, Randall; Selim, Raouf; Byvik, Charles E.; Buoncristiani, A. Martin

    1992-01-01

    Newly developed technique involving use of gold makes possible to fabricate low-resistance contacts with rugged connections to high-Tc superconductors. Gold diffused into specimen of superconducting material by melting gold beads onto surface of specimen, making strong mechanical contacts. Shear strength of gold bead contacts greater than epoxy or silver paste. Practical use in high-current-carrying applications of new high-Tc materials, including superconducting magnets, long-wavelength sensors, electrical ground planes at low temperatures, and efficient transmission of power.

  3. Bi-Polaron Condensation in High Tc Superconductors

    International Nuclear Information System (INIS)

    Ranninger, J.

    1995-01-01

    On the basis of optical measurements-, photoemission-, EXAFS- and neutron scattering-experiments we conclude that itinerant valence electrons coexist with localized bi-polarons.Entering the metallic phase upon chemical doping, a charge transfer between the two electronic subsystems is triggered off. We show that as the temperature is lowered towards Tc this process leads to a delocalization of bi-polarons due to a precursor effect of superfluidity of those bi-polarons. Upon entering the superconducting phase, these bipolarons ultimately condense into a superfluid state which is expected to largely determine the superconducting properties of high Tc materials. (authors)

  4. Characterization of superconducting coil for fault current limitation

    International Nuclear Information System (INIS)

    Polasek, Alexander; Dias, Rodrigo; Niedu, Daniel Brito; Ogasawara, Tsuneharu; Oliveira Filho, Orsino Borges de; Serra, Eduardo Torres; Gomes Junior, George; Amorim, Helio Salim

    2010-01-01

    The increasing power demand has been raising fault currents up to dangerous levels. Superconducting fault current limiters are a promising solution for this problem. In the present work, we studied a superconducting Bi-2212 coil that is used for fault current limitation. Samples were analyzed by XRD, SEM/EDS and measurement of critical temperature (Tc). The Rietveld method was employed for phase quantification. Relatively high Bi-2212 fractions were found. However, Tc varies from a sample to another one. Variations of local Tc are attributed to variations of oxygen content in Bi- 2212 phase. (author)

  5. Superconducting cermets

    International Nuclear Information System (INIS)

    Goyal, A.; Funkenbusch, P.D.; Chang, G.C.S.; Burns, S.J.

    1988-01-01

    Two distant classes of superconducting cermets can be distinguished, depending on whether or not a fully superconducting skeleton is established. Both types of cermets have been successfully fabricated using non-noble metals, with as high as 60wt% of the metal phase. The electrical, magnetic and mechanical behavior of these composites is discussed

  6. Chemical approaches to understanding the environmental behavior of Pu, Np, and Tc

    International Nuclear Information System (INIS)

    Bondietti, E.A.

    1978-01-01

    Some topics discussed are as follows: speciation behavior of Pu, Np, and Tc; thermodynamic and radiochemical behavior; sorption studies with soils; Pu oxidation states in fresh water; Np oxidation states in soils; effect of oxidation state of Tc on environmental transport predictions; and thermodynamic calculations of Tc speciation

  7. Superconducting technology

    International Nuclear Information System (INIS)

    2010-01-01

    Superconductivity has a long history of about 100 years. Over the past 50 years, progress in superconducting materials has been mainly in metallic superconductors, such as Nb, Nb-Ti and Nb 3 Sn, resulting in the creation of various application fields based on the superconducting technologies. High-T c superconductors, the first of which was discovered in 1986, have been changing the future vision of superconducting technology through the development of new application fields such as power cables. On basis of these trends, future prospects of superconductor technology up to 2040 are discussed. In this article from the viewpoints of material development and the applications of superconducting wires and electronic devices. (author)

  8. Interface superconductivity

    Energy Technology Data Exchange (ETDEWEB)

    Gariglio, S., E-mail: stefano.gariglio@unige.ch [DQMP, Université de Genève, 24 Quai E.-Ansermet, CH-1211 Genève (Switzerland); Gabay, M. [Laboratoire de Physique des Solides, Bat 510, Université Paris-Sud 11, Centre d’Orsay, 91405 Orsay Cedex (France); Mannhart, J. [Max Planck Institute for Solid State Research, 70569 Stuttgart (Germany); Triscone, J.-M. [DQMP, Université de Genève, 24 Quai E.-Ansermet, CH-1211 Genève (Switzerland)

    2015-07-15

    Highlights: • We discuss interfacial superconductivity, a field boosted by the discovery of the superconducting interface between LaAlO. • This system allows the electric field control and the on/off switching of the superconducting state. • We compare superconductivity at the interface and in bulk doped SrTiO. • We discuss the role of the interfacially induced Rashba type spin–orbit. • We briefly discuss superconductivity in cuprates, in electrical double layer transistor field effect experiments. • Recent observations of a high T{sub c} in a monolayer of FeSe deposited on SrTiO{sub 3} are presented. - Abstract: Low dimensional superconducting systems have been the subject of numerous studies for many years. In this article, we focus our attention on interfacial superconductivity, a field that has been boosted by the discovery of superconductivity at the interface between the two band insulators LaAlO{sub 3} and SrTiO{sub 3}. We explore the properties of this amazing system that allows the electric field control and on/off switching of superconductivity. We discuss the similarities and differences between bulk doped SrTiO{sub 3} and the interface system and the possible role of the interfacially induced Rashba type spin–orbit. We also, more briefly, discuss interface superconductivity in cuprates, in electrical double layer transistor field effect experiments, and the recent observation of a high T{sub c} in a monolayer of FeSe deposited on SrTiO{sub 3}.

  9. Superconducting critical temperature under pressure

    Science.gov (United States)

    González-Pedreros, G. I.; Baquero, R.

    2018-05-01

    The present record on the critical temperature of a superconductor is held by sulfur hydride (approx. 200 K) under very high pressure (approx. 56 GPa.). As a consequence, the dependence of the superconducting critical temperature on pressure became a subject of great interest and a high number of papers on of different aspects of this subject have been published in the scientific literature since. In this paper, we calculate the superconducting critical temperature as a function of pressure, Tc(P), by a simple method. Our method is based on the functional derivative of the critical temperature with the Eliashberg function, δTc(P)/δα2F(ω). We obtain the needed coulomb electron-electron repulsion parameter, μ*(P) at each pressure in a consistent way by fitting it to the corresponding Tc using the linearized Migdal-Eliashberg equation. This method requires as input the knowledge of Tc at the starting pressure only. It applies to superconductors for which the Migdal-Eliashberg equations hold. We study Al and β - Sn two weak-coupling low-Tc superconductors and Nb, the strong coupling element with the highest critical temperature. For Al, our results for Tc(P) show an excellent agreement with the calculations of Profeta et al. which are known to agree well with experiment. For β - Sn and Nb, we found a good agreement with the experimental measurements reported in several works. This method has also been applied successfully to PdH elsewhere. Our method is simple, computationally light and gives very accurate results.

  10. High-Q Tl2CaBa2Cu2O8 high-Tc superconducting quasi-optical millimeter-wave bandpass filters working at 77 K

    International Nuclear Information System (INIS)

    Zhang, D.; Fetterman, H.R.

    1994-01-01

    Tl 2 CaBa 2 Cu 2 O 8 high-temperature superconducting thin films with T c 's of over 100 K on LaAlO 3 substrates were used to fabricate quasi-optical millimeter-wave bandpass filters. Q-factors of over 400 were achieved, at liquid nitrogen temperatures from these filters at W-band frequencies (75--110 GHz)

  11. Low-temperature specific heat of the β-pyrochlore oxide superconductors under high pressure

    Science.gov (United States)

    Isono, T.; Iguchi, D.; Machida, Y.; Izawa, K.; Salce, B.; Flouquet, J.; Ogusu, H.; Yamaura, J.; Hiroi, Z.

    2011-01-01

    We report the results of the low-temperature specific heat measurements of the single crystalline β-pyrochlore oxide superconductors AOs 2O 6 (A=K, Rb, and Cs) under high pressure up to 13 GPa. We find that superconducting transition temperature ( Tc) monotonically increases for CsOs 2O 6 and RbOs 2O 6, while the one for KOs 2O 6 decreases by applying the pressure. With further increasing the pressure, Tc is suddenly suppressed at the same lattice volume for all compounds, concomitant with the first-order structural phase transition.

  12. Electronic structure and superconductivity of FeSe-related superconductors.

    Science.gov (United States)

    Liu, Xu; Zhao, Lin; He, Shaolong; He, Junfeng; Liu, Defa; Mou, Daixiang; Shen, Bing; Hu, Yong; Huang, Jianwei; Zhou, X J

    2015-05-13

    FeSe superconductors and their related systems have attracted much attention in the study of iron-based superconductors owing to their simple crystal structure and peculiar electronic and physical properties. The bulk FeSe superconductor has a superconducting transition temperature (Tc) of ~8 K and it can be dramatically enhanced to 37 K at high pressure. On the other hand, its cousin system, FeTe, possesses a unique antiferromagnetic ground state but is non-superconducting. Substitution of Se with Te in the FeSe superconductor results in an enhancement of Tc up to 14.5 K and superconductivity can persist over a large composition range in the Fe(Se,Te) system. Intercalation of the FeSe superconductor leads to the discovery of the AxFe2-ySe2 (A = K, Cs and Tl) system that exhibits a Tc higher than 30 K and a unique electronic structure of the superconducting phase. A recent report of possible high temperature superconductivity in single-layer FeSe/SrTiO3 films with a Tc above 65 K has generated much excitement in the community. This pioneering work opens a door for interface superconductivity to explore for high Tc superconductors. The distinct electronic structure and superconducting gap, layer-dependent behavior and insulator-superconductor transition of the FeSe/SrTiO3 films provide critical information in understanding the superconductivity mechanism of iron-based superconductors. In this paper, we present a brief review of the investigation of the electronic structure and superconductivity of the FeSe superconductor and related systems, with a particular focus on the FeSe films.

  13. Organic superconductivity

    International Nuclear Information System (INIS)

    Jerome, D.

    1980-01-01

    We present the experimental evidences for the existence of a superconducting state in the Quasi One Dimensional organic conductor (TMTSF) 2 PF 6 . Superconductivity occuring at 1 K under 12 kbar is characterized by a zero resistance diamagnetic state. The anistropy of the upper critical field of this type II superconductor is consistent with the band structure anistropy. We present evidences for the existence of large superconducting precursor effects giving rise to a dominant paraconductive contribution below 40 K. We also discuss the anomalously large pressure dependence of T sb(s), which drops to 0.19 K under 24 kbar in terms of the current theories. (author)

  14. Inelastic electron scattering influence on the strong coupling oxide superconductors

    International Nuclear Information System (INIS)

    Gabovich, A.M.; Voitenko, A.I.

    1995-01-01

    The superconducting order parameters Δ and energy gap Δ g are calculated taking into account the pair-breaking inelastic quasiparticle scattering by thermal Bose-excitations, e.g., phonons. The treatment is self-consistent because the scattering amplitude depends on Δ. The superconducting transition for any strength of the inelastic scattering is the phase transition of the first kind and the dependences Δ (T) and Δ g (T) tend to rectangular curve that agrees well with the experiment for high-Tc oxides. On the basis of the developed theory the nuclear spin-lattice relaxation rate R s in the superconducting state is calculated. The Hebel-Slichter peak in R s (T) is shown to disappear for strong enough inelastic scattering

  15. Superconducting linac

    International Nuclear Information System (INIS)

    Bollinger, L.M.; Shepard, K.W.; Wangler, T.P.

    1978-01-01

    This project has two goals: to design, build, and test a small superconducting linac to serve as an energy booster for heavy ions from an FN tandem electrostatic accelerator, and to investigate various aspects of superconducting rf technology. The main design features of the booster are described, a status report on various components (resonators, rf control system, linac control system, cryostats, buncher) is given, and plans for the near future are outlined. Investigations of superconducting-linac technology concern studies on materials and fabrication techniques, resonator diagnostic techniques, rf-phase control, beam dynamics computer programs, asymmetry in accelerating field, and surface-treatment techniques. The overall layout of the to-be-proposed ATLAS, the Argonne Tandem-Linac Accelerator System, is shown; the ATLAS would use superconducting technology to produce beams of 5 to 25 MeV/A. 6 figures

  16. High Tc superconductor-gallate crystal structures

    International Nuclear Information System (INIS)

    Gallagher, W.J.; Giess, E.A.; Gupta, A.; Laibowitz, R.B.; O'Sullivan, E.J.; Sandstrom, R.L.

    1990-01-01

    This patent describes a superconductive combination. It comprises a crystalline gallate layer, including a rare earth element or another element selected from the group consisting of Y, La, Bi, and Sc, or combinations of a rare earth element and at least one of the another elements. A superconductive layer thereon, the superconductive layer having a transition temperature in excess of 77 degrees K. and being an oxide material having Cu-O planes whose Cu and O atoms align with Ga and O atoms in the gallate layer

  17. Fracton pairing mechanism for unconventional superconductors: Self-assembling organic polymers and copper-oxide compounds

    DEFF Research Database (Denmark)

    Milovanov, A.V.; Juul Rasmussen, J.

    2002-01-01

    Self-assembling organic polymers and copper-oxide compounds are two classes of unconventional superconductors, whose challenging behavior does not comply with the traditional picture of Bardeen-Cooper-Schrieffer (BCS) superconductivity in regular crystals. In this paper, we propose a theoretical...... or holes) exchange fracton excitations, quantum oscillations of fractal lattices that mimic the complex microscopic organization of the unconventional superconductors. For the copper oxides, the superconducting transition temperature T-c as predicted by the fracton mechanism is of the order of similar to......150 K. We suggest that the marginal ingredient of the high-temperature superconducting phase is provided by fracton coupled holes that condensate in the conducting copper-oxygen planes owing to the intrinsic field-effect-transistor configuration of the cuprate compounds. For the gate...

  18. On the application of High-Tc superconductors in power coils and transformers

    NARCIS (Netherlands)

    Chevtchenko, O.A.

    2002-01-01

    In this study, the electro-magnetic properties of high-Tc tapes and coils are investigated. The focus is on Bi-2223/Ag tapes with non-twisted superconducting filaments as these are the only high-Tc superconductors at present available in sufficient length for practical applications. The study is

  19. Electrochemical investigations of high-Tc superconductors - low-temperature electrochemistry

    International Nuclear Information System (INIS)

    Lorenz, W.J.

    1992-01-01

    This research report presents a summary of results obtained by electrochemical investigations of high-Tc superconductors at room temperature and below the critical temperature (Tc). The studies were to reveal the behaviour of the ceramic superconducting materials at the interface between superconductor and ionic conductor. (MM) With 4 tabs., 8 figs [de

  20. Correlation effects in high-Tc superconductors and heavy fermion compounds

    International Nuclear Information System (INIS)

    Kuzemsky, A.L.

    1993-10-01

    This paper describes certain aspects of Highly Correlated Systems (HCS) such as high Tc superconductors (HTSC) and some new class of Heavy Fermion (HF) systems which have been studied recently. The problem is discussed on how the charge and spin degrees of freedom participate in the specific character of superconductivity in the copper oxides and competition of the magnetism and Kondo screening in heavy fermions. The electronic structure and possible superconducting mechanisms of HTSC compounds are discussed. The similarity and dissimilarity with HF compounds is pointed out. It is shown that the spins and carriers in the copper oxides are coupled in a very nontrivial way in order to introduce the discussion and the comparison of the Emery model, the t - J-model and the Kondo-Heisenberg model. It concerns attempts to derive from fundamental multi-band Hamiltonian the reduced effective Hamiltonians to extract and separate the relevant low-energy physics. A short review of the arguments which seem to support the spin-polaron pairing mechanism in HTSC are presented. Many other topics like the idea of mixed valence states in oxides, the role of charge transfer (CT) excitations, phase separation, self-consistent nonperturbative technique, etc. are also discussed. (author). 161 refs

  1. Superconducted tour

    Energy Technology Data Exchange (ETDEWEB)

    Anon.

    1988-09-15

    Superconductivity - the dramatic drop in electrical resistance in certain materials at very low temperatures - has grown rapidly in importance over the past two or three decades to become a key technology for high energy particle accelerators. It was in this setting that a hundred students and 15 lecturers met in Hamburg in June for a week's course on superconductivity in particle accelerators, organized by the CERN Accelerator School and the nearby DESY Laboratory.

  2. Superconductivity: Phenomenology

    International Nuclear Information System (INIS)

    Falicov, L.M.

    1988-08-01

    This document discusses first the following topics: (a) The superconducting transition temperature; (b) Zero resistivity; (c) The Meissner effect; (d) The isotope effect; (e) Microwave and optical properties; and (f) The superconducting energy gap. Part II of this document investigates the Ginzburg-Landau equations by discussing: (a) The coherence length; (b) The penetration depth; (c) Flux quantization; (d) Magnetic-field dependence of the energy gap; (e) Quantum interference phenomena; and (f) The Josephson effect

  3. On the interaction of granite with Tc(IV) and Tc(VII) in aqueous solution

    International Nuclear Information System (INIS)

    Eriksen, T.E.; Cui, Daquing

    1991-10-01

    The behaviour of technetium in granite-groundwater systems under reducing conditions was investigated. The anion TcO 4 - was reduced to Tc(IV) and simultaneously precipitated as TcO 2 xnH 2 O on the granite surfaces. The electron sources are assumed to be iron oxides and/or iron containing minerals in the granite. The technetium concentration in ground water under repository conditions may be predicted assuming TcO 2 xnH 2 O as the solid phase and TcO(OH) 2 0 and TcO 4 - as the predominant aqueous complexes using a formation constant for TcO(OH) 2 0 of log K = -8.16 and a standard reduction potential E 0 for the reaction TcO 4 - + 3e - + 4H + = TcO 2 xnH 2 O of 0.738 V. The surface related distribution ratio K a for TcO(OH) 2 0 between Stripa granite and ground water is approximately 1 cm based on geometrical surface area. (au)

  4. High T$_{c}$ superconductors and related transition metal oxides special contributions in honor of K. Alex Müller on the occasion of his 80th birthday

    CERN Document Server

    Bussmann-Holder, Annette

    2007-01-01

    This book containing 30 articles written by highly reputed experts is dedicated to K. Alex Müller on the occasion of his 80th birthday. The contributions reflect the major research areas of K. Alex Müller which he activated in high temperature superconductivity and phase transitions. They are theoretical as well as experimental ones and focus mainly on high temperature superconductivity. A smaller part deals with ferroelectricity and their applications. Also in this field there have recently been major break throughs experimentally as well as theoretically which will be addressed by the invited authors. During the scientific career of K. Alex Müller he made major advances in the understanding of ferroelectricity, which used to be his major research field. The discovery of superconductivity in cuprates for which he received together with J. Georg Bednorz the Nobel Prize in 1987 has not diminished his interest in this area, but has enlarged his activities considerably.

  5. The use of microemulsions for the synthesis of oxalate precursors of YBaCuO superconduction oxide

    International Nuclear Information System (INIS)

    Wang, L.; Zhang, Y.; Muhammed, M.

    1992-01-01

    Although emulsion technique has been used as an advanced separation method, little attention has been paid to the particular feature of emulsions as a powerful reaction media for synthesis of powders, e.g., precipitation of fine particles. In the present paper, the authors report the use of some microemulsion systems as a reaction media in a controlled coprecipitation of the oxalate precursors of superconducting YBa 2 Cu 3 O 7-δ ceramics. The phase diagram of the system: oil (hydrocarbon) - surfactant (Aerosol Orange T) - water, in the absence and presence of nitric/oxalic acids and nitrates, have been systematically investigated. Several hydrocarbons, n-hexane, n-haptene and n-octane have been tested. The different stability regions of microemulsions have been determined. The oxalate coprecipitation of Y, Ba and Cu from nitrate solution was studied under various operating conditions, pH, ratio of oil/surfactant/water and ratio of Y/Ba/Cu/.H 2 C 2 O 4 2 . The chemical and morphological properties of the oxalate powders obtained in the microemulsion systems have been examined by different techniques, e.g., ICP, TGA, XRD and SEM. By XRD, the optimum products are found to be amorphous oxalate composite with exact required stoichiometry and high homogeneity. The average size of the dispersed particles is 50-70 nm while the mean diameter of the agglomerates is around 300 nm. The best sinters bulk sample has T, (R = 0) at 92 K. These powders are used as fine precursors for the synthesis of high T c superconducting ceramics as bulk material and particularly thick films

  6. Superconducting wires and methods of making thereof

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Xingchen; Sumption, Michael D.; Peng, Xuan

    2018-03-13

    Disclosed herein are superconducting wires. The superconducting wires can comprise a metallic matrix and at least one continuous subelement embedded in the matrix. Each subelement can comprise a non-superconducting core, a superconducting layer coaxially disposed around the non-superconducting core, and a barrier layer coaxially disposed around the superconducting layer. The superconducting layer can comprise a plurality of Nb.sub.3Sn grains stabilized by metal oxide particulates disposed therein. The Nb.sub.3Sn grains can have an average grain size of from 5 nm to 90 nm (for example, from 15 nm to 30 nm). The superconducting wire can have a high-field critical current density (J.sub.c) of at least 5,000 A/mm.sup.2 at a temperature of 4.2 K in a magnetic field of 12 T. Also described are superconducting wire precursors that can be heat treated to prepare superconducting wires, as well as methods of making superconducting wires.

  7. Superconducting Magnetic Energy Storage

    International Nuclear Information System (INIS)

    Hassenzahl, W.

    1989-01-01

    Recent programmatic developments in Superconducting Magnetic Energy Storage (SMES) have prompted renewed and widespread interest in this field. In mid 1987 the Defense Nuclear Agency, acting for the Strategic Defense Initiative Office issued a request for proposals for the design and construction of SMES Engineering Test Model (ETM). Two teams, one led by Bechtel and the other by Ebasco, are now engaged in the first phase of the development of a 10 to 20 MWhr ETM. This report presents the rationale for energy storage on utility systems, describes the general technology of SMES, and explains the chronological development of the technology. The present ETM program is outlined; details of the two projects for ETM development are described in other papers in these proceedings. The impact of high Tc materials on SMES is discussed

  8. Two band superconductivity for MgB2: Tc and isotope exponent α as a function of the carrier number n and the role of the center of the band

    International Nuclear Information System (INIS)

    Rodriguez-Nunez, J.J.; Schmidt, A.A.; Bianconi, A.; Perali, A.

    2005-08-01

    We study a two band superconducting, assuming that we have two tight binding bands, ε 2 (k-vector) = ε 2 (0) - t 2 [cos(k x ) + cos(k y ) + s 2 cos(k z )] - μ and ε 3 (k-vector) ε 3 (0) - t 3 [cos(k x ) + cos(k y )+s 3 cos(k z )] - μ. We solve the two gap equations at T = T c and calculate T c x n and μ x n for various values of pairing interaction, V, and Debye frequency, ω D . Also, from an expression developed in a previous paper by two of the present authors, we calculate α x n, where n is the number of carriers per site per band and α is the isotope exponent. We take only interband scattering, V, as a first approach. We find that in order to have superconductivity (T c ≠ 0), large values of V are necessary. Also, for V/ω D > 1, we obtain α > 1.00 and for V/ω D >1.00, the isotope exponent becomes less than 1. (author)

  9. Temperature Dependence of Quasiparticle Spectral Weight and Coherence in High Tc Superconductors

    Science.gov (United States)

    He, Yang; Zhang, Jessie; Hoffman, Jennifer; Hoffman Lab Team

    2014-03-01

    Superconductivity arises from the Cooper pairing of quasiparticles on the Fermi surface. Understanding the formation of Cooper pairs is an essential step towards unveiling the mechanism of high Tc superconductivity. We compare scanning tunneling microscope investigations of the temperature dependence of quasiparticle spectral weight and quasiparticle interference in several families of high Tc materials. We calculate the coherent spectral weight related to superconductivity, despite the coexistence of competing orders. The relation between pairing temperature and coherent spectral weight is discussed. We acknowledge support by the New York Community Trust-George Merck Fund.

  10. High temperature interface superconductivity

    International Nuclear Information System (INIS)

    Gozar, A.; Bozovic, I.

    2016-01-01

    Highlight: • This review article covers the topic of high temperature interface superconductivity. • New materials and techniques used for achieving interface superconductivity are discussed. • We emphasize the role played by the differences in structure and electronic properties at the interface with respect to the bulk of the constituents. - Abstract: High-T_c superconductivity at interfaces has a history of more than a couple of decades. In this review we focus our attention on copper-oxide based heterostructures and multi-layers. We first discuss the technique, atomic layer-by-layer molecular beam epitaxy (ALL-MBE) engineering, that enabled High-T_c Interface Superconductivity (HT-IS), and the challenges associated with the realization of high quality interfaces. Then we turn our attention to the experiments which shed light on the structure and properties of interfacial layers, allowing comparison to those of single-phase films and bulk crystals. Both ‘passive’ hetero-structures as well as surface-induced effects by external gating are discussed. We conclude by comparing HT-IS in cuprates and in other classes of materials, especially Fe-based superconductors, and by examining the grand challenges currently laying ahead for the field.

  11. Foreword: Focus on Superconductivity in Semiconductors

    Directory of Open Access Journals (Sweden)

    Yoshihiko Takano

    2008-01-01

    Full Text Available Since the discovery of superconductivity in diamond, much attention has been given to the issue of superconductivity in semiconductors. Because diamond has a large band gap of 5.5 eV, it is called a wide-gap semiconductor. Upon heavy boron doping over 3×1020 cm−3, diamond becomes metallic and demonstrates superconductivity at temperatures below 11.4 K. This discovery implies that a semiconductor can become a superconductor upon carrier doping. Recently, superconductivity was also discovered in boron-doped silicon and SiC semiconductors. The number of superconducting semiconductors has increased. In 2008 an Fe-based superconductor was discovered in a research project on carrier doping in a LaCuSeO wide-gap semiconductor. This discovery enhanced research activities in the field of superconductivity, where many scientists place particular importance on superconductivity in semiconductors.This focus issue features a variety of topics on superconductivity in semiconductors selected from the 2nd International Workshop on Superconductivity in Diamond and Related Materials (IWSDRM2008, which was held at the National Institute for Materials Science (NIMS, Tsukuba, Japan in July 2008. The 1st workshop was held in 2005 and was published as a special issue in Science and Technology of Advanced Materials (STAM in 2006 (Takano 2006 Sci. Technol. Adv. Mater. 7 S1.The selection of papers describe many important experimental and theoretical studies on superconductivity in semiconductors. Topics on boron-doped diamond include isotope effects (Ekimov et al and the detailed structure of boron sites, and the relation between superconductivity and disorder induced by boron doping. Regarding other semiconductors, the superconducting properties of silicon and SiC (Kriener et al, Muranaka et al and Yanase et al are discussed, and In2O3 (Makise et al is presented as a new superconducting semiconductor. Iron-based superconductors are presented as a new series of high-TC

  12. Feshbach shape resonance for high Tc pairing in superlattices of quantum stripes and quantum wells

    Directory of Open Access Journals (Sweden)

    A Bianconi

    2006-09-01

    Full Text Available   The Feshbach shape resonances in the interband pairing in superconducting superlattices of quantum wells or quantum stripes is shown to provide the mechanism for high Tc superconductivity. This mechanism provides the Tc amplification driven by the architecture of material: superlattices of quantum wells (intercalated graphite or diborides and superlattices of quantum stripes (doped high Tc cuprate perovskites where the chemical potential is tuned to a Van Hove-Lifshitz singularity (vHs in the electronic energy spectrum of the superlattice associated with the change of the Fermi surface dimensionality in one of the subbands.

  13. James C. McGroddy Prize Talk: Superconductivity in alkali-metal doped Carbon-60

    Science.gov (United States)

    Hebard, Arthur

    2008-03-01

    Carbon sixty (C60), which was first identified in 1985 in laser desorption experiments, is unquestionably an arrestingly beautiful molecule. The high symmetry of the 12 pentagonal and 20 hexagonal faces symmetrically arrayed in a soccer-ball like structure invites special attention and continues to stimulate animated speculation. The availability in 1990 of macroscopic amounts of purified C60 derived from carbon-arc produced soot allowed the growth and characterization of both bulk and thin-film samples. Crystalline C60 is a molecular solid held together by weak van der Waals forces. The fcc structure has a 74% packing fraction thus allowing ample opportunity (26% available volume) for the intercalation of foreign atoms into the interstitial spaces of the three dimensional host. This opportunity catalyzed much of the collaborative work amongst chemists, physicists and materials scientists at Bell Laboratories, and resulted in the discovery of superconductivity in alkali-metal doped C60 with transition temperatures (Tc) in the mid-30-kelvin range. In this talk I will review how the successes of this initial team effort stimulated a worldwide collaboration between experimentalists and theorists to understand the promise and potential of an entirely new class of superconductors containing only two elements, carbon and an intercalated alkali metal. Although the cuprates still hold the record for the highest Tc, there are still open scientific questions about the mechanism that gives rise to such unexpectedly high Tc's in the non-oxide carbon-based superconductors. The doped fullerenes have unusual attributes (e.g., narrow electronic bands, high disorder, anomalous energy scales, and a tantalizing proximity to a metal-insulator Mott transition), which challenge conventional thinking and at the same time provide useful insights into new directions for finding even higher Tc materials. The final chapter of the `soot to superconductivity' story has yet to be written.

  14. Earlier and recent aspects of superconductivity

    International Nuclear Information System (INIS)

    Bednorz, J.G.; Muller, K.A.

    1990-01-01

    Contemporary knowledge of superconductivity is set against its historical background in this book. First, the highlights of superconductivity research in the twentieth century are reviewed. Further contributions then describe the basic phenomena resulting from the macroscopic quantum state of superconductivity (such as zero resistivity, the Meissner-Ochsenfeld effect, and flux quantization) and review possible mechanisms, including the classical BCS theory and the more recent alternative theories. The main categories of superconductors - elements, intermetallic phases, chalcogenides, oxides and organic compounds - are described. Common features and differences in their structure and electronic properties are pointed out. This overview of superconductivity is completed by a discussion of properties related to the coherence length

  15. The structure of the non-superconducting phase La3Ba3Cu6Osub(14+ x) and its relation to the high - Tc superconductor YBa2Cu3Osub(7 -delta)

    International Nuclear Information System (INIS)

    David, W.I.F.; Harrison, W.T.A.; Ibberson, R.M.; Grasmeder, J.R.; Lanchester, P.

    1987-01-01

    The authors report time-of-flight neutron powder diffraction results, which confirm that the structure of La 3 Ba 3 Cu 6 Osub(14+x) is isomorphous with the tetragonal variant of YBa 2 Cu 3 Osub(7-delta); in particular, the copper coordination and calculated valencies of both compounds agree closely. The apparent contradiction of stoichiometries between these two phases is resolved by ordering of the large cations consistent with a formulation La(Lasub(0.25)Basub(0.75)) 2 Cu 3 Osub(7+1/2x). The present results indicate that there is a remarkable structural stability from RA 2 Cu 3 O 6 to RA 2 Cu 3 Osub(7.2), although superconductivity appears to be confined to the range RA 2 Cu 3 Osub(6.5) to Ra 2 Cu 3 O 7 . (author)

  16. Exafs studies of coprecipitation and adsorption reactions of Tc

    Energy Technology Data Exchange (ETDEWEB)

    Bunker, D.J.; Jones, M.J.; Livens, F.R.; Collison, D. [Manchester Univ. (United Kingdom). Dept. of Chemistry; Pattrick, R.A.D. [Manchester Univ., Dept. of Earth Sciences (United Kingdom); Charnock, J.M. [CLRC Daresbury Laboratoire, Warrington Cheshire (United Kingdom)

    2000-07-01

    Adsorption and coprecipitation reactions may be a simple way of removing [TcO{sub 4}]{sup -} from aqueous solution. The effectiveness of a range of potential adsorbents and precipitants has been evaluated and some are capable of near quantitative (>98%) removal of [TcO{sub 4}){sup -} from solution. X-ray absorption near edge structure (XANES) has been used to determine Tc oxidation states and extended X-ray absorption fine structure spectroscopy (EXAFS) has been used to identify the local environment of Tc. The absorption edge position has been determined, using [PPh{sub 4}][TcO{sub 4}], TcS{sub 2} and Tc{sub 2}S{sub 7} as model compounds, and is diagnostic of Tc oxidation state. In a series of experiments investigating FeS coprecipitation, Tc was reduced to oxidation state (IV) and its local environment resembled that in TcO{sub 2} (6 O atoms at approximately 2.0 Angstrom). (authors)

  17. Superconducting cyclotrons

    International Nuclear Information System (INIS)

    Blosser, H.G.; Johnson, D.A.; Burleigh, R.J.

    1976-01-01

    Superconducting cyclotrons are particularly appropriate for acceleration of heavy ions. A review is given of design features of a superconducting cyclotron with energy 440 (Q 2 /A) MeV. A strong magnetic field (4.6 tesla average) leads to small physical size (extraction radius 65 cm) and low construction costs. Operating costs are also low. The design is based on established technology (from present cyclotrons and from large bubble chambers). Two laboratories (in Chalk River, Canada and in East Lansing, Michigan) are proceeding with construction of full-scale prototype components for such cyclotrons

  18. Status of RF superconductivity at Argonne

    Energy Technology Data Exchange (ETDEWEB)

    Shepard, K.W.

    1989-01-01

    Development of a superconducting (SC) slow-wave structures began at Argonne National Laboratory (ANL) in 1971, and led to the first SC heavy-ion linac (ATLAS - the Argonne Tandem-Linac Accelerating System), which began regularly scheduled operation in 1978. To date, more than 40,000 hours of bean-on target operating time has been accumulated with ATLAS. The Physics Division at ANL has continued to develop SC RF technology for accelerating heavy-ions, with the result that the SC linac has, up to the present, has been in an almost continuous process of upgrade and expansion. It should be noted that this has been accomplished while at the same time maintaining a vigorous operating schedule in support of the nuclear and atomic physics research programs of the division. In 1987, the Engineering Physics Division at ANL began development of SC RF components for the acceleration of high-brightness proton and deuterium beams. This work has included the evaluation of RF properties of high-{Tc} oxide superconductors, both for the above and for other applications. The two divisions collaborated while they worked on several applications of RF SC, and also worked to develop the technology generally. 11 refs., 6 figs.

  19. Method and system for controlling chemical reactions between superconductors and metals in superconducting cables

    Energy Technology Data Exchange (ETDEWEB)

    Shen, Tengming

    2018-01-02

    A method, system, and apparatus for fabricating a high-strength Superconducting cable comprises pre-oxidizing at least one high-strength alloy wire, coating at least one Superconducting wire with a protective layer, and winding the high-strength alloy wire and the Superconducting wire to form a high-strength Superconducting cable.

  20. Method and system for controlling chemical reactions between superconductors and metals in superconducting cables

    Science.gov (United States)

    Shen, Tengming

    2016-11-15

    A method, system, and apparatus for fabricating a high-strength Superconducting cable comprises pre-oxidizing at least one high-strength alloy wire, coating at least one Superconducting wire with a protective layer, and winding the high-strength alloy wire and the Superconducting wire to form a high-strength Superconducting cable.

  1. Direct observation of competition between superconductivity and charge density wave order in YBa2Cu3O6.67

    DEFF Research Database (Denmark)

    Chang, J.; Blackburn, E.; Holmes, A. T.

    2012-01-01

    Superconductivity often emerges in the proximity of, or in competition with, symmetry-breaking ground states such as antiferromagnetism or charge density waves (CDW). A number of materials in the cuprate family, which includes the high transition-temperature (high-Tc) superconductors, show spin...... and charge density wave order. Thus a fundamental question is to what extent do these ordered states exist for compositions close to optimal for superconductivity. Here we use high-energy X-ray diffraction to show that a CDW develops at zero field in the normal state of superconducting YBa2Cu3O6.67 (Tc= 67 K......). This sample has a hole doping of 0.12 per copper and a well-ordered oxygen chain superstructure. Below Tc, the application of a magnetic field suppresses superconductivity and enhances the CDW. Hence, the CDW and superconductivity in this typical high-Tc material are competing orders with similar energy...

  2. Superconductivity proximate to antiferromagnetism in a copper-oxide monolayer grown on Bi2Sr2CaCu2O8 +δ

    Science.gov (United States)

    Wang, Shuai; Zhang, Long; Wang, Fa

    2018-01-01

    A nodeless superconducting (SC) gap was reported in a recent scanning tunneling spectroscopy experiment of a copper-oxide monolayer grown on a Bi2Sr2CaCu2O8 +δ (Bi2212) substrate [Zhong et al., Sci. Bull. 61, 1239 (2016), 10.1007/s11434-016-1145-4], which is in stark contrast to the nodal d -wave pairing gap in the bulk cuprates. Motivated by this experiment, we first show with first-principles calculations that the tetragonal CuO (T-CuO) monolayer on the Bi2212 substrate is more stable than the commonly postulated CuO2 structure. The T-CuO monolayer is composed of two CuO2 layers sharing the same O atoms. The band structure is obtained by first-principles calculations, and its strong electron correlation is treated with the renormalized mean-field theory. We argue that one CuO2 sublattice is hole doped while the other sublattice remains half filled and may have antiferromagnetic (AF) order. The doped Cu sublattice can show d -wave SC; however, its proximity to the AF Cu sublattice induces a spin-dependent hopping, which splits the Fermi surface and may lead to a full SC gap. Therefore, the nodeless SC gap observed in the experiment could be accounted for by the d -wave SC proximity to an AF order, thus it is extrinsic rather than intrinsic to the CuO2 layers.

  3. The NMR probe of high-Tc materials and correlated electron systems

    CERN Document Server

    Walstedt, Russell E

    2018-01-01

    This new edition updates readers in three areas of NMR studies, namely, recent developments in high-Tc materials, heavy fermion systems and actinide oxides are presented.  The NMR probe has yielded a vast array of data for solid state materials, corresponding to different compounds, ionic sites, and nuclear species, as well as to a wide variety of experimental conditions. The last two parts of the book are completely new in this edition, while the first part has seen major updates. This edition features the latest developments for high-Tc materials, especially the advances in the area of pseudogap studies are reviewed.  An in depth overview of heavy fermion systems is presented in the second part,  notably Kondo lattices, quantum critical points and unconventional superconductivity are areas of intense research recently and are covered extensively. Finally, valuable information from NMR studies with actinide oxides will be provided. Ongoing analysis and discussion of NMR data have resulted in a wealth o...

  4. Superconducting materials

    International Nuclear Information System (INIS)

    Ruvalds, J.

    1990-01-01

    This report discusses the following topics: Fermi liquid nesting in high temperature superconductors; optical properties of high temperature superconductors; Hall effect in superconducting La 2-x Sr x CuO 4 ; source of high transition temperatures; and prospects for new superconductors

  5. Superconducting transformer

    International Nuclear Information System (INIS)

    Murphy, J.H.

    1982-01-01

    A superconducting transformer having a winding arrangement that provides for current limitation when subjected to a current transient as well as more efficient utilization of radial spacing and winding insulation. Structural innovations disclosed include compressed conical shaped winding layers and a resistive matrix to promote rapid switching of current between parallel windings

  6. Superconducting magnets

    International Nuclear Information System (INIS)

    1994-08-01

    This report discusses the following topics on superconducting magnets: D19B and -C: The next steps for a record-setting magnet; D20: The push beyond 10 T: Beyond D20: Speculations on the 16-T regime; other advanced magnets for accelerators; spinoff applications; APC materials development; cable and cabling-machine development; and high-T c superconductor at low temperature

  7. Superconducting magnets

    International Nuclear Information System (INIS)

    Willen, E.

    1996-01-01

    Superconducting dipole magnets for high energy colliders are discussed. As an example, the magnets recently built for the Relativistic Heavy Ion Collider at Brookhaven are reviewed. Their technical performance and the cost for the industry-built production dipoles are given. The cost data is generalized in order to extrapolate the cost of magnets for a new machine

  8. Bipolar superconductivity

    International Nuclear Information System (INIS)

    Pankratov, S.G.

    1987-01-01

    A model of bipolaron superconductivity suggested by Soviet scientist Alexandrov A.S. and French scientist Ranninger is presentes in a popular way. It is noted that the bipolaron theory gives a good explanation of certain properties of new superconductors, high critical temperature, in particular

  9. Superconducting transistor

    International Nuclear Information System (INIS)

    Gray, K.E.

    1978-01-01

    A three film superconducting tunneling device, analogous to a semiconductor transistor, is presented, including a theoretical description and experimental results showing a current gain of four. Much larger current gains are shown to be feasible. Such a development is particularly interesting because of its novelty and the striking analogies with the semiconductor junction transistor

  10. Midwest Superconductivity Consortium: 1994 Progress report

    Energy Technology Data Exchange (ETDEWEB)

    1995-01-01

    The mission of the Midwest Superconductivity Consortium, MISCON, is to advance the science and understanding of high {Tc} superconductivity. During the past year, 27 projects produced over 123 talks and 139 publications. Group activities and interactions involved 2 MISCON group meetings (held in August and January); with the second MISCON Workshop held in August; 13 external speakers; 79 collaborations (with universities, industry, Federal laboratories, and foreign research centers); and 48 exchanges of samples and/or measurements. Research achievements this past year focused on understanding the effects of processing phenomena on structure-property interrelationships and the fundamental nature of transport properties in high-temperature superconductors.

  11. Superconductivity: materials and applications; La supraconductivite: materiaux et apllications

    Energy Technology Data Exchange (ETDEWEB)

    Duchateau, J.L. [CEA Cadarache, 13 - Saint Paul lez Durance (France); Kircher, F. [CEA Saclay, 91 - Gif sur Yvette (France); Leveque, J. [Groupe de Recherche en Electrotechnique et Electronique de Nancy, GREEN - UHP, 54 - Vandoeuvre les Nancy (France); Tixador, P. [INP/Institut Neel, 38 - Grenoble (France)

    2008-07-01

    This digest paper presents the different types of superconducting materials: 1 - the low-TC superconductors: the multi-filament composite as elementary constituent, the world production of NbTi, the superconducting cables of the LHC collider and of the ITER tokamak; 2 - the high-TC superconductors: BiSrCaCuO (PIT 1G) ribbons and wires, deposited coatings; 3 - application to particle physics: the the LHC collider of the CERN, the LHC detectors; 4 - applications to thermonuclear fusion: Tore Supra and ITER tokamaks; 5 - NMR imaging: properties of superconducting magnets; 6 - applications in electrotechnics: cables, motors and alternators, current limiters, transformers, superconducting energy storage systems (SMES). (J.S.)

  12. Theory of superconductivity

    International Nuclear Information System (INIS)

    Crisan, M.

    1988-01-01

    This book discusses the most important aspects of the theory. The phenomenological model is followed by the microscopic theory of superconductivity, in which modern formalism of the many-body theory is used to treat most important problems such as superconducting alloys, coexistence of superconductivity with the magnetic order, and superconductivity in quasi-one-dimensional systems. It concludes with a discussion on models for exotic and high temperature superconductivity. Its main aim is to review, as complete as possible, the theory of superconductivity from classical models and methods up to the 1987 results on high temperature superconductivity. Contents: Phenomenological Theory of Superconductivity; Microscopic Theory of Superconductivity; Theory of Superconducting Alloys; Superconductors in a Magnetic Field; Superconductivity and Magnetic Order; Superconductivity in Quasi-One-Dimensional Systems; and Non-Conventional Superconductivity

  13. Measurement method of moving vehicle in the magnetic levitation and propulsion system using high-Tc superconducting bulks; Koon chodendo barukutai wo riyoshita fujo suishin shisutemu no suishin tokusei keisoku shuho

    Energy Technology Data Exchange (ETDEWEB)

    Fuwa, Y.; Mizuma, T.

    1999-06-07

    The transportation system using simple magnetic levitation system got in the combination of high-temperature superconductivity bulk body and permanent magnet, which caught a quantum magnetic flux, is devised in great numbers, and the model equipment has also been manufactured. In the meantime, a grasp of levitation and guide characteristics is necessary for the case in which this levitation system is applied to the simple individual transportation system, and the measurement of the levitation characteristics is indispensable for the reason. In the conventional research, the measurement of the levitation characteristics has not been very much made. There was due to be no technique which measured kinetic characteristics of noncontacting surfacing and running travel body. In this study, measuring method for measuring these levitation characteristics was devised, and it was applied to actual measurement by the production of the model test equipment. Through this measurement, the purpose of this study is to show with that it is applicable for the real test equipment as this measuring method judges possibility of application to simple transportation system. (NEDO)

  14. Interdiffusion studies on high-Tc superconducting YBa2Cu3O7-δ thin films on Si(111) with a NiSi2/ZrO2 buffer layer

    DEFF Research Database (Denmark)

    Aarnink, W.A.M.; Blank, D.H.A.; Adelerhof, D.J.

    1991-01-01

    Interdiffusion studies on high-T(c) superconducting YBa2Cu3O7-delta thin films with thickness in the range of 2000-3000 angstrom, on a Si(111) substrate with a buffer layer have been performed. The buffer layer consists of a 400 angstrom thick epitaxial NiSi2 layer covered with 1200 angstrom...... of polycrystalline ZrO2. YBa2Cu3O7-delta films were prepared using laser ablation. The YBa2Cu3O7-delta films on the Si/NiSi2/ZrO2 substrates are of good quality; their critical temperatures T(c,zero) and T(c,onset) have typical values of 85 and 89 K, respectively. The critical current density j(c) at 77 K equaled 4...... x 10(4) A/cm2. With X-ray analysis (XRD), only c-axis orientation has been observed. The interdiffusion studies, using Rutherford backscattering spectrometry (RBS) and scanning Auger microscopy (SAM) show that the ZrO2 buffer layer prevents severe Si diffusion to the YBa2Cu3O7-delta layer, the Si...

  15. Amorphous-like interfacial layer between a high-Tc superconducting Tl-1223 film and a Ag substrate examined by high-voltage high-resolution transmission electron microscopy

    International Nuclear Information System (INIS)

    Kim, Bongjun; Kim, Hyuntak; Nagai, Takuro; Matsui, Yoshio; Horiuchi, Shigeo; Jeong, Daeyeong; Deinhofer, Christian; Gritzner, Gerhard; Kim, Youngmin; Kim, Younjoong

    2006-01-01

    The thin amorphous-like layer, formed at the interface between a high-T c superconducting (Tl 0.5 , Pb 0.5 )(Sr 0.8 , Ba 0.2 )Ca 2 Cu 3 O y (Tl-1223) film and a Ag substrate during heating at 910 .deg. C, has been examined by using high-voltage high-resolution transmission electron microscopy. The interfacial layer is less than 10 nm in thickness. It contacts the (001) plane of Tl-1223 and the (113) or (133) planes of Ag in most cases. Its composition is similar to that of Tl-1223, except for the inclusion of a substantial amount of Ag. Its formation proceeds by diffusion of Ag into Tl-1223, during which a structure change first occurs at the layer of CuO 2 + Ca planes. The Tl(Pb)O + the Sr(Ba)O layers are then destroyed to cause the total structure to become amorphous-like. Furthermore, we have found that it is formed under an irradiation of highly energetic electrons.

  16. Dependence of trapped-flux-induced surface resistance of a large-grain Nb superconducting radio-frequency cavity on spatial temperature gradient during cooldown through T_{c}

    Directory of Open Access Journals (Sweden)

    Shichun Huang

    2016-08-01

    Full Text Available Recent studies by Romanenko et al. revealed that cooling down a superconducting cavity under a large spatial temperature gradient decreases the amount of trapped flux and leads to reduction of the residual surface resistance. In the present paper, the flux expulsion ratio and the trapped-flux-induced surface resistance of a large-grain cavity cooled down under a spatial temperature gradient up to 80  K/m are studied under various applied magnetic fields from 5 to 20  μT. We show the flux expulsion ratio improves as the spatial temperature gradient increases, independent of the applied magnetic field: our results support and enforce the previous studies. We then analyze all rf measurement results obtained under different applied magnetic fields together by plotting the trapped-flux-induced surface resistance normalized by the applied magnetic field as a function of the spatial temperature gradient. All the data can be fitted by a single curve, which defines an empirical formula for the trapped-flux-induced surface resistance as a function of the spatial temperature gradient and applied magnetic field. The formula can fit not only the present results but also those obtained by Romanenko et al. previously. The sensitivity r_{fl} of surface resistance from trapped magnetic flux of fine-grain and large-grain niobium cavities and the origin of dT/ds dependence of R_{fl}/B_{a} are also discussed.

  17. Superconducting properties of magnetron sputtered high T/sub c/ thin films containing oxide compounds of yttrium, bismuth, or thallium

    International Nuclear Information System (INIS)

    Kang, J.H.; Kampwirth, R.T.; Gray, K.E.

    1989-01-01

    The authors have used multiple source magnetron sputtering to prepare thin films of Y-Ba-Cu-O, Bi-Ca-Sr-Cu-O, and Tl-Ca-Ba-Cu-O on (100) SrTiO/sub 3/, (100) MgO, and ZrO/sub 2/-9%Y/sub 2/O/sub 3/ substrates. Y-Ba-Cu-O films grow best on SrTiO/sub 3/ with mostly an a-axis orientation. Stoichiometry, particularly the Ba/Ca ratio must be within 2% of the correct value to obtain narrow ΔT/sub c/ transitions. Conversely the 80K phase of Bi-Ca-Sr-Cu-O films grows best on MgO substrates and has a predominant c-axis orientation. The requirements on composition are less stringent, however, the annealing temperature must be held within a narrow around 865 0 C to obtain the best films. The best films of Tl-Ca-Ba-Cu-O compounds are grown on (100) oriented and polycrystalline ZrO/sub 2/ substrates. The highest transition temperature, T/sub c0/, where the resistance goes zero is about 114K in the Tl/sub 2/Ba/sub 2/Ca/sub 2/Cu/sub 3/O/sub x/ phase and 100-105K in Tl/sub 2/Ba/sub 2/Ca/sub 1/Cu/sub 2/O/sub x/ and Tl/sub 1/Ba/sub 2/Ca/sub 2/Cu/sub 3/O/sub x/ phase samples. The upper critical field measurements show high anisotropies in the critical field slopes (≥70 for Tl-Ba-Ca-Cu-O compounds and ∼15 for Bi-Sr-Ca-Cu-O compounds), as might be expected from highly oriented materials. The authors compare the preparation conditions and superconducting properties, including T/sub c/, ΔT/sub c/, dB/sub c2//dT (parallel and perpendicular to film surface), of all three compounds

  18. Superconductivity and ceramic superconductors II; Proceedings of the Symposium, Orlando, FL, Nov. 12-15, 1990. Ceramic transactions. Vol. 18

    International Nuclear Information System (INIS)

    Nair, K.M.; Balachandran, U.; Chiang, Y.-M.; Bhalla, A.S.

    1991-01-01

    The present symposium on superconductivity and ceramic superconductors discusses fundamentals and general principles, powder processing and properties, fabrication and properties, and device reliability and applications. Attention is given to phase formation in the Tl-Ca-Ba-Cu-O system, comparative defect studies in La2CuO4 and La2NiO4, solid solution and defect behavior in high Tc oxides, oxygen ion transport and disorder in cuprates, and Sr-free Bi-Ln-Ca-Cu-O superconductors. Topics addressed include the preparation of superconductor Y-Ba-Cu-O powder by single-step calcining in air, low-temperature synthesis of YBa2Cu3O(7-x), synthesis of high-phase purity ceramic oxide superconductors by the xerogel method, and the preparation and characterization of the BYa2Cu4O8 superconductor. Also discussed are optical studies of humidity-based corrosion effects on thin film and bulk ceramic YBa2Cu3O(7-delta), thermomechanical processing of YBa2Cu3O(x)/Ag sheathed wires, and the expansion of high-Tc superconducting ceramics

  19. Tunneling observation at very low temperature of impurity bands within the gap of the Kondo superconducting system CuFe/Pb(T(K)>T(c))

    International Nuclear Information System (INIS)

    Dumoulin, Louis; Le Fur, Daniel

    1976-01-01

    Very low temperature superconducting tunneling experiments on CuFe(12.10 -6 ) backed by superconducting lead show a band of localized states next to the gap edge. There is no quantitative agreement with the perturbative approach of Mueller-Hartmann Zittartz in this system where the Kondo temperature is larger than the superconductive T(c) [fr

  20. Experimental Observation of Non-'S-Wave' Superconducting Behavior in Bulk Superconducting Tunneling Junctions of Yba2Cu3O7-δ

    Directory of Open Access Journals (Sweden)

    Leandro Jose Guerra

    1998-06-01

    Full Text Available Evidence of non-s-wave superconductivity from normal tunneling experiments in bulk tunneling junctions of YBa2Cu3O7-δ is presented. The I-V and dI/dV characteristics of bulk superconducting tunneling junctions of YBa2Cu3O7-δ have been measured at 77.0K and clear deviation from s-wave superconducting behavior has been observed. The result agrees with d-wave symmetry, and interpreting the data in this way, the magnitude of the superconducting energy gap, 2Δ, is found to be (0.038 ± 0.002 eV. Comparing this energy gap with Tc (2Δ/kB Tc = 5.735, indicates that these high-Tc superconductors are strongly correlated materials, which in contrast with BCS-superconductors are believed to be weakly correlated.

  1. Color superconductivity

    International Nuclear Information System (INIS)

    Wilczek, F.

    1997-01-01

    The asymptotic freedom of QCD suggests that at high density - where one forms a Fermi surface at very high momenta - weak coupling methods apply. These methods suggest that chiral symmetry is restored and that an instability toward color triplet condensation (color superconductivity) sets in. Here I attempt, using variational methods, to estimate these effects more precisely. Highlights include demonstration of a negative pressure in the uniform density chiral broken phase for any non-zero condensation, which we take as evidence for the philosophy of the MIT bag model; and demonstration that the color gap is substantial - several tens of MeV - even at modest densities. Since the superconductivity is in a pseudoscalar channel, parity is spontaneously broken

  2. Color superconductivity

    Energy Technology Data Exchange (ETDEWEB)

    Wilczek, F. [Institute for Advanced Study, Princeton, NJ (United States)

    1997-09-22

    The asymptotic freedom of QCD suggests that at high density - where one forms a Fermi surface at very high momenta - weak coupling methods apply. These methods suggest that chiral symmetry is restored and that an instability toward color triplet condensation (color superconductivity) sets in. Here I attempt, using variational methods, to estimate these effects more precisely. Highlights include demonstration of a negative pressure in the uniform density chiral broken phase for any non-zero condensation, which we take as evidence for the philosophy of the MIT bag model; and demonstration that the color gap is substantial - several tens of MeV - even at modest densities. Since the superconductivity is in a pseudoscalar channel, parity is spontaneously broken.

  3. Superconductivity in Bi-Sr-Ca-Cu-O bulk and film ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Sukhanov, A A; Ozmanian, KH R; Sandomirskii, B B

    1988-07-01

    A superconducting transition with Tc0 = 82-95 K and Tc(R = 0) = 82-72 K was observed in Bi(Sr/1-x/Ca/x/)2Cu3O(y) bulk and film specimens obtained via a solid-phase reaction. Temperature dependences of the resistance, critical current, and magnetic susceptibility were measured.

  4. Status of RF superconductivity at Argonne

    International Nuclear Information System (INIS)

    Shepard, K.W.

    1990-01-01

    Development of a superconducting slow-wave structures began at Argonne National Laboratory (ANL) in 1971, and led to the first superconducting heavy-ion linac (ATLAS - the Argonne Tandem-Linac Accelerator System). The Physics Division at ANL has continued to develop superconducting RF technology for accelerating heavy-ions, with the result that the linac has been in an almost continuous process of upgrade and expansion. In 1987, the Engineering Physics Division at ANL began developing of superconducting RF components for the acceleration of high-brightness proton and deuterium beams. The two divisions collaborate in work on several applications of RF superconductivity, and also in work to develop the technology generally. The present report briefly describes major features of the superconducting heavy-ion linac (very-low-velocity superconducting linac, positive ion injector), proton accelerating structures (superconducting resonant cavities for acceleration of high-current proton and deuteron beams, RF properties of oxide superconductors), and future work. Both divisions expect to continue a variety of studies, frequently in collaboration, to advance the basic technology of RF superconductivity. (N.K.)

  5. Magnetic-Field-Tunable Superconducting Rectifier

    Science.gov (United States)

    Sadleir, John E.

    2009-01-01

    Superconducting electronic components have been developed that provide current rectification that is tunable by design and with an externally applied magnetic field to the circuit component. The superconducting material used in the device is relatively free of pinning sites with its critical current determined by a geometric energy barrier to vortex entry. The ability of the vortices to move freely inside the device means this innovation does not suffer from magnetic hysteresis effects changing the state of the superconductor. The invention requires a superconductor geometry with opposite edges along the direction of current flow. In order for the critical current asymmetry effect to occur, the device must have different vortex nucleation conditions at opposite edges. Alternative embodiments producing the necessary conditions include edges being held at different temperatures, at different local magnetic fields, with different current-injection geometries, and structural differences between opposite edges causing changes in the size of the geometric energy barrier. An edge fabricated with indentations of the order of the coherence length will significantly lower the geometric energy barrier to vortex entry, meaning vortex passage across the device at lower currents causing resistive dissipation. The existing prototype is a two-terminal device consisting of a thin-film su - perconducting strip operating at a temperature below its superconducting transition temperature (Tc). Opposite ends of the strip are connected to electrical leads made of a higher Tc superconductor. The thin-film lithographic process provides an easy means to alter edge-structures, current-injection geo - metries, and magnetic-field conditions at the edges. The edge-field conditions can be altered by using local field(s) generated from dedicated higher Tc leads or even using the device s own higher Tc superconducting leads.

  6. Superconducting magnet

    Science.gov (United States)

    1985-01-01

    Extensive computer based engineering design effort resulted in optimization of a superconducting magnet design with an average bulk current density of approximately 12KA/cm(2). Twisted, stranded 0.0045 inch diameter NbTi superconductor in a copper matrix was selected. Winding the coil from this bundle facilitated uniform winding of the small diameter wire. Test coils were wound using a first lot of the wire. The actual packing density was measured from these. Interwinding voltage break down tests on the test coils indicated the need for adjustment of the wire insulation on the lot of wire subsequently ordered for construction of the delivered superconducting magnet. Using the actual packing densities from the test coils, a final magnet design, with the required enhancement and field profile, was generated. All mechanical and thermal design parameters were then also fixed. The superconducting magnet was then fabricated and tested. The first test was made with the magnet immersed in liquid helium at 4.2K. The second test was conducted at 2K in vacuum. In the latter test, the magnet was conduction cooled from the mounting flange end.

  7. Colloquium: High pressure and road to room temperature superconductivity

    Science.gov (United States)

    Gor'kov, Lev P.; Kresin, Vladimir Z.

    2018-01-01

    This Colloquium is concerned with the superconducting state of new high-Tc compounds containing hydrogen ions (hydrides). Recently superconductivity with the record-setting transition temperature of Tc=203 K was reported for sulfur hydrides under high pressure. In general, high pressure serves as a path finding tool toward novel structures, including those with very high Tc . The field has a rich and interesting history. Currently, it is broadly recognized that superconductivity in sulfur hydrides owes its origin to the phonon mechanism. However, the picture differs from the conventional one in important ways. The phonon spectrum in sulfur hydride is both broad and has a complex structure. Superconductivity arises mainly due to strong coupling to the high-frequency optical modes, although the acoustic phonons also make a noticeable contribution. A new approach is described, which generalizes the standard treatment of the phonon mechanism and makes it possible to obtain an analytical expression for Tc in this phase. It turns out that, unlike in the conventional case, the value of the isotope coefficient (for the deuterium-hydrogen substitution) varies with the pressure and reflects the impact of the optical modes. The phase diagram, that is the pressure dependence of Tc , is rather peculiar. A crucial feature is that increasing pressure results in a series of structural transitions, including the one which yields the superconducting phase with the record Tc of 203 K. In a narrow region near P ≈150 GPa the critical temperature rises sharply from Tc≈120 to ≈200 K . It seems that the sharp structural transition, which produces the high-Tc phase, is a first-order phase transition caused by interaction between the order parameter and lattice deformations. A remarkable feature of the electronic spectrum in the high-Tc phase is the appearance of small pockets at the Fermi level. Their presence leads to a two-gap spectrum, which can, in principle, be observed with the

  8. Melt formed superconducting joint between superconducting tapes

    International Nuclear Information System (INIS)

    Benz, M.G.; Knudsen, B.A.; Rumaner, L.E.; Zaabala, R.J.

    1992-01-01

    This patent describes a superconducting joint between contiguous superconducting tapes having an inner laminate comprised of a parent-metal layer selected from the group niobium, tantalum, technetium, and vanadium, a superconductive intermetallic compound layer on the parent-metal layer, a reactive-metal layer that is capable of combining with the parent-metal and forming the superconductive intermetallic compound, the joint comprising: a continuous precipitate of the superconductive intermetallic compound fused to the tapes forming a continuous superconducting path between the tapes

  9. Resonance of Superconducting Microstrip Antenna with Aperture in the Ground Plane

    Directory of Open Access Journals (Sweden)

    S. Benkouda

    2013-08-01

    Full Text Available This paper presents a rigorous full-wave analysis of a high Tc superconducting rectangular microstrip antenna with a rectangular aperture in the ground plane. To include the effect of the superconductivity of the microstrip patch in the full-wave analysis, a complex surface impedance is considered. The proposed approach is validated by comparing the computed results with previously published data. Results showing the effect of the aperture on the resonance of the superconducting microstrip antenna are given.

  10. High critical temperature superconducting composite and fabrication process

    International Nuclear Information System (INIS)

    Dubots, P.; Legat, D.

    1989-01-01

    The core comprises a high temperature superconducting sintered oxide coated with alumina or barium oxide covered with a first sheath in aluminum, a second sheath in niobium and a third sheath in copper [fr

  11. An investigation of texturing by magnetic and mechanical techniques in high critical temperature superconducting ceramics

    International Nuclear Information System (INIS)

    Deschanels, X.

    1992-11-01

    The principal goal of this work is to quantify the influence of texture of ceramic superconductors ReBaCuO (Re=Dy, Y) on their critical current density (Jc). The magnetic alignment of particles at ambient temperature is the first technique who has allowed us to produce superconducting (Meissner effect) and textured ceramics. However, these materials are very brittle because of their porosity and this makes it impossible to measure their Jc. Press-forging (or creep sintering) is the second technique who has allowed us to prepare highly textured ceramics materials which are also dense. We have studied the influence of various conditions of thermomechanical treatment (sintering time and temperature, applied load, rate of deformation, density of the material at the beginning) on the texture quality. We have shown that at 900 deg, the eutectic liquid formed by BaCuO 2 , CuO and YBa 2 Cu 3 0 7-Y various mechanisms that help explain the formation of observed texture. After the oxidation stage which requires heat treatment under controlled atmospheres, we obtain superconducting ceramics (Tc=85 K). Moreover, this study also shows that the texture can improve the Jc by 400%, to 750 A/cm 2 at 77 K in the best specimens. This low value is explained by the presence of non-superconducting secondary phases and amorphous phases at the grain boundaries. (Author). 120 refs., figs., tabs

  12. A simple model to estimate the optimal doping of p - Type oxide superconductors

    Directory of Open Access Journals (Sweden)

    Adir Moysés Luiz

    2008-12-01

    Full Text Available Oxygen doping of superconductors is discussed. Doping high-Tc superconductors with oxygen seems to be more efficient than other doping procedures. Using the assumption of double valence fluctuations, we present a simple model to estimate the optimal doping of p-type oxide superconductors. The experimental values of oxygen content for optimal doping of the most important p-type oxide superconductors can be accounted for adequately using this simple model. We expect that our simple model will encourage further experimental and theoretical researches in superconducting materials.

  13. The war of the cold: an history of the superconductivity

    International Nuclear Information System (INIS)

    Matricon, J.; Waysand, G.

    1994-01-01

    The evolution of superconductivity is described from a scientific, and social points of view. The evolution of researches and realizations towards the absolute zero temperature leading to the discovery of superconductivity by Gilles Holst in 1991, is followed by the theoretical modelization of the superconductivity phenomena leading to the Ginzburg and Landau theory in 1950 and to the Bardeen, Cooper and Schrieffer theory in 1957. Then researches on materials that lead to high-tc superconductors are presented with some applications. (A.B.). refs., figs,. tabs

  14. Bi-based superconducting fibers with high critical parameters

    International Nuclear Information System (INIS)

    Huo Yujing; He Yusheng; Liu Menglin; Mao Sining; Cai Liying; Wang Ying; Zhang Jincang; He Aisheng; Wang Jinsong

    1991-01-01

    Superconducting fibers of Bi(Pb)-Sr-Ca-Cu-O high Tc superconducting materials have been prepared by means of the laser-heated pedestal growth (LHPG) method. The highest zero resistance temperature T c0 reaches is 114K, and the highest critical current density J c (77K, O T) is greater than 5000 A/cm 2 . As-grown superconducting fibers were successfully fabricated without post growth heat treatment. Amorphous materials were used for the first time to make high quality fibers. The influence of growth conditions, thermal treatment and the composition of the fibers were discussed. (author). 5 refs., 7 figs., 3 tabs

  15. Superconducting Nb{sub 3}Sn intermetallics made by electrochemical reduction of Nb{sub 2}O{sub 5}-SnO{sub 2} oxides

    Energy Technology Data Exchange (ETDEWEB)

    Glowacki, B A; Fray, D J; Yan, X-Y; Chen, G

    2003-05-01

    The article is focused on low temperature superconducting Nb{sub 3}Sn material manufactured by novel electrodeoxidizing method developed in Cambridge whereby the range of alloys and intermetallics are produced cheaply making potential superconducting wires more cost effective. The process of direct electrochemical reduction of Nb{sub 2}O{sub 5}-SnO{sub 2} mixtures and in situ formation of the Nb{sub 3}Sn is discussed in details.

  16. Chemistry of /sup 99m/Tc labeling kits

    International Nuclear Information System (INIS)

    Srivastava, S.C.; Meinken, G.; Richards, P.

    1976-01-01

    Problems have been reported with the use of kit-produced /sup 99m/Tc radiopharmaceuticals. This study was undertaken to understand the chemistry involved in various stannous kit systems. The relation between Tc, tin, and the ligands used to complex the reduced Tc was investigated. It is concluded that for reliable performance, stannous kits should be prepared so that most of the tin is kept in the usable (reducing) form; a solution would be to use minimum tin and a large excess of complexing agent. Oxidation of the Tc complex to free pertechnetate is not a major problem in most kit systems. 5 figures

  17. Magnetic and Superconducting Materials at High Pressures

    Energy Technology Data Exchange (ETDEWEB)

    Struzhkin, Viktor V. [Carnegie Inst. of Washington, Washington, DC (United States)

    2015-03-24

    The work concentrates on few important tasks in enabling techniques for search of superconducting compressed hydrogen compounds and pure hydrogen, investigation of mechanisms of high-Tc superconductivity, and exploring new superconducting materials. Along that route we performed several challenging tasks, including discovery of new forms of polyhydrides of alkali metal Na at very high pressures. These experiments help us to establish the experimental environment that will provide important information on the high-pressure properties of hydrogen-rich compounds. Our recent progress in RIXS measurements opens a whole field of strongly correlated 3d materials. We have developed a systematic approach to measure major electronic parameters, like Hubbard energy U, and charge transfer energy Δ, as function of pressure. This technique will enable also RIXS studies of magnetic excitations in iridates and other 5d materials at the L edge, which attract a lot of interest recently. We have developed new magnetic sensing technique based on optically detected magnetic resonance from NV centers in diamond. The technique can be applied to study superconductivity in high-TC materials, to search for magnetic transitions in strongly correlated and itinerant magnetic materials under pressure. Summary of Project Activities; development of high-pressure experimentation platform for exploration of new potential superconductors, metal polyhydrides (including newly discovered alkali metal polyhydrides), and already known superconductors at the limit of static high-pressure techniques; investigation of special classes of superconducting compounds (high-Tc superconductors, new superconducting materials), that may provide new fundamental knowledge and may prove important for application as high-temperature/high-critical parameter superconductors; investigation of the pressure dependence of superconductivity and magnetic/phase transformations in 3d transition metal compounds, including

  18. Applied superconductivity handbook on devices and applications

    CERN Document Server

    2015-01-01

    This wide-ranging presentation of applied superconductivity, from fundamentals and materials right up to the latest applications, is an essential reference for physicists and engineers in academic research as well as in the field. Readers looking for a systematic overview on superconducting materials will expand their knowledge and understanding of both low and high Tc superconductors, including organic and magnetic materials. Technology, preparation and characterization are covered for several geometries, but the main benefit of this work lies in its broad coverage of significant applications in power engineering or passive devices, such as filter and antenna or magnetic shields. The reader will also find information on superconducting magnets for diverse applications in mechanical engineering, particle physics, fusion research, medicine and biomagnetism, as well as materials processing. SQUIDS and their usage in medicine or geophysics are thoroughly covered as are applications in quantum metrology, and, las...

  19. Isotope effect on superconductivity and Raman phonons of Pyrochlore Cd2Re2O7

    Science.gov (United States)

    Razavi, F. S.; Hajialamdari, M.; Reedyk, M.; Kremer, R. K.

    2018-06-01

    Cd2Re2O7 is the only α-Pyrochlore exhibiting superconductivity with a transition temperature (Tc) of ∼ 1 K. In this study, we present the effect of oxygen isotope (18O) as well as combined 18O and cadmium isotope (116Cd) substitution on the superconductivity and Raman scattering spectrum of Cd2Re2O7. The change of Tc and the energy gap Δ(T) are reported using various techniques including point contact spectroscopy. The shift in Raman phonon frequencies upon isotope substitution will be compared with measurement of the isotope effect on the superconducting transition temperature.

  20. Environmental conditions for the formation of insoluble Tc in water ponds located above paddy fields

    International Nuclear Information System (INIS)

    Ishii, Nobuyoshi; Koiso, Hiroyuki; Takeda, Hiroshi; Uchida, Shigeo

    2008-01-01

    Optimum conditions for the formation of insoluble Tc (Tc in >0.2 μm size fraction) were studied using a microcosm including water ponds above a paddy field to understand Tc behavior in such fields. In the microcosm, soluble TcO 4 - was converted to insoluble forms, but no changes in the form of Tc were observed in filtered microcosm samples which were microorganisms-free. The formation of insoluble Tc was inhibited by the addition of the antibiotic chloramphenicol. In addition, the reduction of soluble Tc(VII)O 4 - to low-valence oxide was not observed in the filtered microcosm samples, although reducing conditions were present. These results indicated that bacteria were involved in the formation of insoluble Tc. Since oxidizing conditions influence bacterial metabolism, the formation of insoluble Tc by bacteria was studied under aerobic and anaerobic conditions. The results showed that anaerobic conditions were favorable for the formation of insoluble Tc. In addition, the addition of formate as an electron donor to a microcosm sample facilitated the formation of insoluble Tc. The results suggested that insoluble Tc in the water ponds above paddy fields was caused by bacteria, which were shown to couple the oxidation of formate to the reduction of Tc(VII) during anaerobic respiration

  1. Formation of a Tc(III)-adenosine diphosphate complex

    International Nuclear Information System (INIS)

    Torres, J.; Kremer, C.; Kremer, E.

    1995-01-01

    A 99 Tc-ADP complex was prepared when KTcO 4 was reduced in aqueous medium by SnCl 2 , Na 2 S 2 O 4 , NaBH 4 or Zn in the presence of ADP in excess. The resulting solution was studied by chromatography and spectrophotometry. Electrochemical reduction and substitution on [Tc III (tu) 6 ] 3+ were investigated as alternative synthetic routes. The anionic Tc-ADP complex was isolated as a solid. Cerimetric titrations confirmed the oxidation state +3 for the central atom. IR and 1 H-NMR data showed that the purine base is bonded to the Tc central atom but not the ribose moiety. No oxo groups seemed to be directly bonded to the Tc atom. The complex is rather stable in neutral solutions. However, it decomposes to pertechnetate and TcO 2 at extreme pH values. (author). 16 refs., 2 figs., 3 tabs

  2. Superconducting plasmas

    International Nuclear Information System (INIS)

    Ohnuma, Toshiro; Ohno, J.

    1994-01-01

    Superconducting (SC) plasmas are proposed and investigated. The SC plasmas are not yet familiar and have not yet been studied. However, the existence and the importance of SC plasmas are stressed in this report. The existence of SC plasmas are found as follows. There is a fundamental property of Meissner effect in superconductors, which shows a repulsive effect of magnetic fields. Even in that case, in a microscopic view, there is a region of magnetic penetration. The penetration length λ is well-known as London's penetration depth, which is expressed as δ = (m s /μ 0 n s q s 2 ) 1/2 where m s , n s , q s and μ o show the mass, the density, the charge of SC electron and the permeability in free space, respectively. Because this expression is very simple, no one had tried it into more simple and meaningful form. Recently, one of the authors (T.O.) has found that the length can be expressed into more simple and understandable fundamental form as λ = c/ω ps where c = (ε 0 μ 0 ) -1/2 and ω ps = (n s q s 2 /m s ε 0 ) 1/2 are the light velocity and the superconducting plasma frequency. From this simple expression, the penetration depth of the magnetic field to SC is found as a SC plasma skin depth, that is, the fundamental property of SC can be expressed by the SC plasmas. This discovery indicates an importance of the studies of superconducting plasmas. From these points, several properties (propagating modes et al) of SC plasmas, which consist of SC electrons, normal electrons and lattice ions, are investigated in this report. Observations of SC plasma frequency is also reported with a use of Terahertz electromagnet-optical waves

  3. Superconducting thin films

    International Nuclear Information System (INIS)

    Hebard, A.F.; Vandenberg, J.M.

    1982-01-01

    This invention relates to granular metal and metal oxide superconducting films formed by ion beam sputter deposition. Illustratively, the films comprise irregularly shaped, randomly oriented, small lead grains interspersed in an insulating lead oxide matrix. The films are hillock-resistant when subjected to thermal cycling and exhibit unusual josephson-type switching characteristics. Depending on the oxygen content, a film may behave in a manner similar to that of a plurality of series connected josephson junctions, or the film may have a voltage difference in a direction parallel to a major surface of the film that is capable of being switched from zero voltage difference to a finite voltage difference in response to a current larger than the critical current

  4. Liquid phase sintered superconducting cermet

    International Nuclear Information System (INIS)

    Ray, S.P.

    1990-01-01

    This patent describes a method of making a superconducting cermet having superconducting properties with improved bulk density, low porosity and in situ stabilization. It comprises: forming a structure of a superconducting ceramic material having the formula RM 2 Cu 3 O (6.5 + x) wherein R is one or more rare earth elements capable of reacting to form a superconducting ceramic, M is one or more alkaline earth metal elements selected from barium and strontium capable of reacting to form a superconducting ceramic, x is greater than 0 and less than 0.5; and a precious metal compound in solid form selected from the class consisting of oxides, sulfides and halides of silver; and liquid phase sintering the mixture at a temperature wherein the precious metal of the precious metal compound is molten and below the melting point of the ceramic material. The liquid phase sintering is carried out for a time less than 36 hours but sufficient to improve the bulk density of the cermet

  5. Electronic properties of high Tc superconductors. Propiedades electronicas de los superconductores de alta temperatura critica

    Energy Technology Data Exchange (ETDEWEB)

    Rojo, A G

    1989-01-01

    Using analytical and numerical methods, the electronic properties of the copper-oxygen plane in the normal phase of high Tc superconductors are described. Using the slave-boson technique in the saddle point, a theory of the metal insulator transition which generalizes the notions of a Mott insulator to the case of more than a single band for those planes is presented. A phase-diagram is obtained in the parameter space and effective masses, optical gaps and metallization are calculated as a function of the number of carriers. Based on the experimental evidence, the theory permits classification of superconducting compounds as charge transfer insulators in the stoichiometric case. The insulator state is characterized by a non-zero optical gap and a divergent effective mass which corresponds to the breakage of a Fermi-liquid scheme. The results obtained are applicable to metal-transition-oxides whose behaviour has been traditionally controversial and it is concluded that it is necessary to broaden the meaning of a Mott insulator to the case of more than a single band to better understand them. Based on the ideas of group renormalization in a real space, a lattice approximation is presented, which allows: a) To complement the treatment of slave-bosons in phase diagrams and optical gaps; b) Identification of an attraction mechanism between carriers originating from purely repulsive interactions. Numerical calculations in small clusters show the existence of a pairing mechanism showing a superconducting instability from a charge transfer insulator. (Author).

  6. Dense high temperature ceramic oxide superconductors

    Science.gov (United States)

    Landingham, Richard L.

    1993-01-01

    Dense superconducting ceramic oxide articles of manufacture and methods for producing these articles are described. Generally these articles are produced by first processing these superconducting oxides by ceramic processing techniques to optimize materials properties, followed by reestablishing the superconducting state in a desired portion of the ceramic oxide composite.

  7. Solubility study of Tc(IV) in a granitic water

    International Nuclear Information System (INIS)

    Liu, D.J.; Yao, J.; Wang, B.; Bruggeman, C.; Maes, N.

    2007-01-01

    The deep geological disposal of the high level radioactive wastes is expected to be a safe disposal method in most countries. The long-lived fission product 99 Tc is present in large quantities in nuclear wastes and its chemical behavior in aqueous solution is of considerable interest. Under oxidizing conditions technetium exists as the anionic species TcO 4 - whereas under the reducing conditions, expected to exist in a deep geological repository, it is generally predicted that technetium will be present as TcO 2 .nH 2 O. Hence, the mobility of Tc(IV) in reducing groundwater may be limited by the solubility of TcO 2 .nH 2 O under these conditions. Due to this fact it is important to investigate the solubility of TcO 2 .nH 2 O. The solubility determines the release of radionuclides from waste form and is used as a source term in radionuclide migration analysis in performance assessment of radioactive waste repository. Technetium(IV) was prepared by reduction of a technetate solution with Sn 2+ . The solubility of Tc(IV) has been determined in simulated groundwater and redistilled water under aerobic and anaerobic conditions. The effects of pH and CO 3 2- concentration of solution on solubility of Tc(IV) were studied. The concentration of total technetium and Tc(IV) species in the solutions were periodically determined by separating the oxidized and reduced technetium species using a solvent extraction procedure and counting the beta activity of the 99 Tc with a liquid scintillation counter. The experimental results show that the rate of oxidation of Tc(IV) in simulated groundwater and redistilled water is about (1.49 ∝ 1.86) x 10 -9 mol L -1 d -1 under aerobic conditions, while no Tc(IV) oxidation was detected in simulated groundwater and redistilled water under anaerobic conditions. Under aerobic or anaerobic conditions the solubility of Tc(IV) in simulated groundwater and redistilled water is equal on the whole after centrifugation or ultrafiltration. The

  8. The effect of ammonia intercalation on the superconducting ...

    African Journals Online (AJOL)

    A theoretical investigation of the electronic properties of the relatively high-Tc alkali-metal doped superconducting fullerides when they are further exposed to ammonia molecules as dopants is presented. Our numerical method relies on a group theoretical technique for the formation of molecular orbitals (MO's) for the solid ...

  9. The state of superconductivity

    International Nuclear Information System (INIS)

    Clark, T.D.

    1981-01-01

    The present status of applications based on the phenomena of superconductivity are reviewed. Superconducting materials, large scale applications, the Josephson effect and its applications, and superconductivity in instrumentation, are considered. The influence that superconductivity has had on modern theories of elementary particles, such as gauge symmetry breaking, is discussed. (U.K.)

  10. Tc Reductant Chemistry and Crucible Melting Studies with Simulated Hanford Low-Activity Waste

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Dong-Sang; Soderquist, Chuck Z.; Icenhower, Jonathan P.; McGrail, B PETER.; Scheele, Randall D.; McNamara, Bruce K.; Bagaasen, Larry M.; Schweiger, Michael J.; Crum, Jarrod V.; Yeager, John D.; Matyas, Josef; Darnell, Lori P.; Schaef, Herbert T.; Owen, Antionette T.; Kozelisky, Anne E.; Snow, Lanee A.; Steele, Marilyn J.

    2005-03-30

    The FY 2003 risk assessment (RA) of bulk vitrification (BV) waste packages used 0.3 wt% of the technetium (Tc) inventory as a leachable salt and found it sufficient to create a significant peak in the groundwater concentration in a 100-meter down-gradient well. Although this peak met regulatory limits, considering uncertainty in the actual Tc salt fraction, peak concentrations could exceed the maximum concentration limit (MCL) under some scenarios so reducing the leachable salt inventory is desirable. The main objective of this study was to reduce the mobile Tc species available within a BV disposal package by reducing the oxidation state of the Tc in the waste feed and/or during melting because Tc in its reduced form of Tc(IV) has a much lower volatility than Tc(VII). Reduced Tc volatility has a secondary benefit of increasing the Tc retention in glass.

  11. Superconducting property measuring system by magnetization method

    International Nuclear Information System (INIS)

    Ikisawa, K.; Mori, T.; Takasu, N.

    1988-01-01

    Superconducting property measuring system (CMS-370B) for high temperature oxide superconductor has been developed. This system adopts magnetization measurement. The superconducting properties are able to be measured automatically and continuously changing the temperature and external magnetic field. The critical current density as a function of temperature and magnetic field of high temperature superconductor YBa 2 Cu 3 O 7-y (YBCO) has been measured. This paper reports how it was confirmed that this system having the high performance and the accuracy gave the significant contribution to the superconducting material development

  12. Superconductores de alta Tc, diez años después

    Directory of Open Access Journals (Sweden)

    A. Mariño Camargo

    1996-07-01

    Full Text Available This contribution is a short review of the current state of the high temperature superconductivity. After ten years of research in this field. A description of the common characteristics of the new sllperconducting materials is followed by the discussion of so me releva nt problems that limit their applications. Sorne aspects related to the determination of the mechanisms responsibles for the high Tc superconductivity are mentioned.

  13. 100 years of superconductivity

    CERN Document Server

    Rogalla, Horst

    2011-01-01

    Even a hundred years after its discovery, superconductivity continues to bring us new surprises, from superconducting magnets used in MRI to quantum detectors in electronics. 100 Years of Superconductivity presents a comprehensive collection of topics on nearly all the subdisciplines of superconductivity. Tracing the historical developments in superconductivity, the book includes contributions from many pioneers who are responsible for important steps forward in the field.The text first discusses interesting stories of the discovery and gradual progress of theory and experimentation. Emphasizi

  14. Superconducting accelerator technology

    International Nuclear Information System (INIS)

    Grunder, H.A.; Hartline, B.K.

    1986-01-01

    Modern and future accelerators for high energy and nuclear physics rely increasingly on superconducting components to achieve the required magnetic fields and accelerating fields. This paper presents a practical overview of the phenomenon of superconductivity, and describes the design issues and solutions associated with superconducting magnets and superconducting rf acceleration structures. Further development and application of superconducting components promises increased accelerator performance at reduced electric power cost

  15. Round robin tests of Tc and Ic on YBa/sub 2/Cu/sub 3/O/sub x/

    International Nuclear Information System (INIS)

    Kimura, Y.; Higuchi, N.; Meguro, S.; Takahashi, K.; Uyeda, K.; Ishihara, T.; Inukai, E.; Umeda, M.

    1989-01-01

    In the author's research and development of oxide superconducting material, methods for measuring the critical properties such as critical temperature and critical current were investigated and studied by way of round robin tests. The investigation was carried out through the steps of (1) decision on the specifications of common samples and measuring methods, (2) preparation and characterization of common samples, (3) distribution of samples to ten member research organs of Super-GM, (4) experimental measurement in the respective research organs, and (5) analysis of measurement results. The measurement of critical temperature and critical current were made mainly using the 4-probe method, and partially the magnetization method. The results were found to disperse, depending on the measurement methods and definitions of Tc and lc. Data analysis with these factors clarified is important

  16. Possibility of high temperature superconducting phases in PdH

    Science.gov (United States)

    Tripodi, Paolo; Di Gioacchino, Daniele; Borelli, Rodolfo; Vinko, Jenny Darja

    2003-05-01

    Possible new superconducting phases with a high critical transition temperature (Tc) have been found in stable palladium-hydrogen (PdHx) samples for stoichiometric ratio x=H/Pd⩾1, in addition to the well-known low critical transition temperature (0⩽Tc⩽9) when x is in the range (0.75⩽x⩽1.00). Possible new measured superconducting phases with critical temperature in the range 51⩽Tc⩽295 K occur. This Tc varies considerably with every milli part of x when x exceeds unit. A superconducting critical current density Jc⩾6.1×104 A cm-2 has been measured at 77 K with HDC=0 T.

  17. Design and preliminary assessment of 99mTc-labeled ultrasmall superparamagnetic iron oxide-conjugated bevacizumab for single photon emission computed tomography/magnetic resonance imaging of hepatocellular carcinoma

    International Nuclear Information System (INIS)

    Yanzhao Zhao; Hui Tan; Bing Wu; Pengcheng Hu; Pengyue Wu; Yushen Gu; Dengfeng Cheng; Hongcheng Shi; Qi Yao; Chunfu Zhang

    2014-01-01

    Hepatocellular carcinoma (HCC) has a very high incidence and mortality. Early diagnosis and timely treatments are therefore required to improve the quality of life and survival rate of HCC patients. Here, we developed a vascular endothelial growth factor (VEGF)-based multimodality imaging agent for single photon emission computed tomography (SPECT), computed tomography (CT) and magnetic resonance imaging (MRI) and used it to assess HCC mice and explore the combinative value of CT/MRI-based morphological imaging and SPECT functional imaging. HCC targeting with 125 I-labeled bevacizumab monoclonal antibody (mAb) was examined using SPECT/CT in HepG2 tumor-bearing mice after intravenous mAb injection. Based on this, an integrated, bimodal, VEGF-targeted, ultrasmall superparamagnetic iron oxide (USPIO)-conjugated 99m Tc-labeled bevacizumab mAb was synthesized to increase tumor penetration and accumulations. The in vivo pharmacokinetics and HepG2 tumor targeting were explored through in vivo planar imaging and SPECT/CT using a mouse model of HepG2 liver cancer. The specificity of the radiolabeled nanoparticles for HepG2 HCC was verified using in vitro immunohistochemistry and Prussian blue staining. With diethylenetriamine pentaacetic acid as a bifunctional chelating agent, USPIO-bevacizumab achieved a 99m Tc labeling efficiency of >90 %. The in vivo imaging results also exhibited the targeting of USPIO on HepG2 HCC. The specificity of these results was confirmed using in vitro immunohistochemistry and Prussian blue staining. Our preliminary findings showed the potential of USPIO as an imaging agent for the SPECT/MRI of HepG2 HCC. (author)

  18. High field superconducting magnets

    Science.gov (United States)

    Hait, Thomas P. (Inventor); Shirron, Peter J. (Inventor)

    2011-01-01

    A superconducting magnet includes an insulating layer disposed about the surface of a mandrel; a superconducting wire wound in adjacent turns about the mandrel to form the superconducting magnet, wherein the superconducting wire is in thermal communication with the mandrel, and the superconducting magnet has a field-to-current ratio equal to or greater than 1.1 Tesla per Ampere; a thermally conductive potting material configured to fill interstices between the adjacent turns, wherein the thermally conductive potting material and the superconducting wire provide a path for dissipation of heat; and a voltage limiting device disposed across each end of the superconducting wire, wherein the voltage limiting device is configured to prevent a voltage excursion across the superconducting wire during quench of the superconducting magnet.

  19. Understanding and application of superconducting materials

    International Nuclear Information System (INIS)

    Moon, Byeong Mu; Lee, Chun Heung

    1997-02-01

    This book deals with superconducting materials, which contains from basic theory to application of superconducting materials. The contents of this book are mystery of superconducting materials, properties of superconducting materials, thermodynamics of superconducting materials, theoretical background of superconducting materials, tunnelling and quantum interference, classification and properties of superconducting materials, high temperature superconducting materials, production and analysis of superconducting materials and application of superconducting materials.

  20. Dimensionality Driven Enhancement of Ferromagnetic Superconductivity in URhGe

    Science.gov (United States)

    Braithwaite, Daniel; Aoki, Dai; Brison, Jean-Pascal; Flouquet, Jacques; Knebel, Georg; Nakamura, Ai; Pourret, Alexandre

    2018-01-01

    In most unconventional superconductors, like the high-Tc cuprates, iron pnictides, or heavy-fermion systems, superconductivity emerges in the proximity of an electronic instability. Identifying unambiguously the pairing mechanism remains nevertheless an enormous challenge. Among these systems, the orthorhombic uranium ferromagnetic superconductors have a unique position, notably because magnetic fields couple directly to ferromagnetic order, leading to the fascinating discovery of the reemergence of superconductivity in URhGe at a high field. Here we show that uniaxial stress is a remarkable tool allowing the fine-tuning of the pairing strength. With a relatively small stress, the superconducting phase diagram is spectacularly modified, with a merging of the low- and high-field superconducting states and a significant enhancement of the superconductivity. The superconducting critical temperature increases both at zero field and under a field, reaching 1 K, more than twice higher than at ambient pressure. This enhancement of superconductivity is shown to be directly related to a change of the magnetic dimensionality detected from an increase of the transverse magnetic susceptibility: In addition to the Ising-type longitudinal ferromagnetic fluctuations, transverse magnetic fluctuations also play an important role in the superconducting pairing.

  1. A study on the effect of tantalum-impurity content on the superconducting properties of niobium materials used for making superconducting radio frequency cavities

    Science.gov (United States)

    Roy, S. B.; Sharath Chandra, L. S.; Chattopadhyay, M. K.; Tiwari, M. K.; Lodha, G. S.; Myneni, G. R.

    2012-11-01

    Niobium materials in highly pure form are used in the fabrication of superconducting radio frequency cavities. We present here a study of the superconducting properties of such niobium materials that have been used in the fabrication of high accelerating gradient superconducting radio frequency cavities after determining their tantalum-impurity contents using a synchrotron-based x-ray fluorescence spectroscopy technique. Our results show that there is a small change in superconducting parameters such as TC,HC1 and HC2 when the tantalum-impurity content varies from ≈150 to ≈1300 ppm. In contrast, a buffered chemical polishing of the same niobium samples changes all these superconducting parameters more significantly. The implications of these results on the performance of niobium superconducting radio frequency cavities are discussed.

  2. Conductive polymer switch for controlling superconductivity

    International Nuclear Information System (INIS)

    McDevitt, J.T.; Haupt, S.G.; Riley, D.R.; Zhao, J.; Grassi, J.; Lo, K.; Jones, C.

    1994-01-01

    The preparation of a hybrid conducting polymer/high-temperature superconductor device consisting of a polypyrrole coated YBa 2 Cu 3 O 7-σ microbridge is reported. Electrochemical techniques are exploited to alter the oxidation state of the polymer and, in doing so, it is found for the first time that superconductivity can be modulated in a controllable and reproducible fashion by a polymer layout. Whereas the neutral (insulating) polypyrrole only slightly influences the electrical properties of the underlying YBa 2 Cu 3 O 7-σ film, the oxidized (conductive) polymer depresses T c by up to 50K. In a similar fashion, the oxidation state of the polymer is found to reversibly modulate the magnitude of J c , the superconducting critical current. Thus, a new type of molecule switch for controlling superconductivity is demonstrated

  3. ac superconducting articles

    International Nuclear Information System (INIS)

    Meyerhoff, R.W.

    1977-01-01

    A noval ac superconducting cable is described. It consists of a composite structure having a superconducting surface along with a high thermally conductive material wherein the superconducting surface has the desired physical properties, geometrical shape and surface finish produced by the steps of depositing a superconducting layer upon a substrate having a predetermined surface finish and shape which conforms to that of the desired superconducting article, depositing a supporting layer of material on the superconducting layer and removing the substrate, the surface of the superconductor being a replica of the substrate surface

  4. Synthesis of a Novel Energetic Heterocyclic Oxidizer with Higher Energy and Lower Sensitivity Final Report CRADA No. TC02099.0

    Energy Technology Data Exchange (ETDEWEB)

    Pagoria, P. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Racoveanu, A. [Physical Sciences, Inc., Andover, MD (United States)

    2017-09-08

    The project involved the synthesis of 5g of a target energetic compound, 3,4-bis(5-nitro-1,2,5- oxadiazol-4-yl)-1,2,5-oxadiazole-1-oxide (DNTF. The deliverables were the synthesis of 5g of DNTF along with quantities of the precursor compounds. In addition, small-scale safety tests on DNTF were performed, which to confirmed that DNTF has no undesirable safety properties before scaling up the synthesis in Phase II of this project.

  5. High-Tc superconductor quantum interference devices

    International Nuclear Information System (INIS)

    1991-01-01

    This patent describes a superconductive quantum interferometric device for sensing a characteristic of a magnetic field. It comprises a substrate having a surface, the substrate being selected from the group which consists of strontium titanate, aluminum oxide, sapphire, ZrO 2 and mixtures thereof; a coating of MgO on the surface of the substrate; two identical thin-strip films of a high-critical temperature superconductor on the coating, each of the films having a pair of mutually parallel arms in the form of superconductor strips extending toward and aligned with super conductor strips forming corresponding arms of the other thin-strip film, and a crossbar strip connecting the arms of each thin-strip film at right angles to the arms, the high-critical-temperature superconductor being selected from the group which consists of yttrium-barium-calcium-copper-oxides, bismuth-strontium-calcium-copper-oxides, thallium-barium-copper-oxides, thallium-barium-calcium-copper-oxides, barium oxide: potassium oxide: bismuth oxides, and calcium oxide: zinc oxide: iron oxides; and insulating films on the coating between corresponding free ends of the arms thin-strip films, the insulating films being composed of a material selected from the group which consists of silicon dioxide, silicon nitride, magnesium oxide and mixture thereof

  6. Superconductivity in Mesocrystalline Inverse Opal Structures

    Science.gov (United States)

    Lungu, Anca; Bleiweiss, Michael; Saygi, Salih; Amirzadeh, Jafar; Datta, Timir

    2000-03-01

    Mesocrystalline inverse opal structures were fabricated by the electrodeposition of metallic lead in synthetic opals. In these structures, the superconducting regions percolate in all directions through the voids in the artificial opals and their size is comparable to the coherence length for bulk lead. The inverse lead opals were proven superconducting, with a transition temperature close to that of bulk lead (between 7.2 K and 7.36 K) and broad transition regions. The magnetic behavior of the inverse opals was very different from that of bulk lead. Due to the reduced dimensonality of the superconducting regions, not surprisingly, the magnetic properties of our samples were found to be similar to those of type II superconductors. The critical magnetic field (or the field at which T_copals was proven at least two times larger than that for bulk lead and (dT_c/dH) was observed 2.7 times smaller. We found a reversible ZFC-FC magnetic behavior in the temperature range between T* and T_c. We also performed magnetic relaxation measurements and studied the fluctuation diamagnetism above T_c.

  7. Superconductivity mediated by quantum critical antiferromagnetic fluctuations: The rise and fall of hot spots

    Science.gov (United States)

    Wang, Xiaoyu; Schattner, Yoni; Berg, Erez; Fernandes, Rafael M.

    2017-05-01

    In several unconventional superconductors, the highest superconducting transition temperature Tc is found in a region of the phase diagram where the antiferromagnetic transition temperature extrapolates to zero, signaling a putative quantum critical point. The elucidation of the interplay between these two phenomena—high-Tc superconductivity and magnetic quantum criticality—remains an important piece of the complex puzzle of unconventional superconductivity. In this paper, we combine sign-problem-free quantum Monte Carlo simulations and field-theoretical analytical calculations to unveil the microscopic mechanism responsible for the superconducting instability of a general low-energy model, called the spin-fermion model. In this approach, low-energy electronic states interact with each other via the exchange of quantum critical magnetic fluctuations. We find that even in the regime of moderately strong interactions, both the superconducting transition temperature and the pairing susceptibility are governed not by the properties of the entire Fermi surface, but instead by the properties of small portions of the Fermi surface called hot spots. Moreover, Tc increases with increasing interaction strength, until it starts to saturate at the crossover from hot-spots-dominated to Fermi-surface-dominated pairing. Our work provides not only invaluable insights into the system parameters that most strongly affect Tc, but also important benchmarks to assess the origin of superconductivity in both microscopic models and actual materials.

  8. Redox behavior of Tc(VII)/Tc(IV) under various reducing conditions in 0.1 M NaCl solutions

    International Nuclear Information System (INIS)

    Kobayashi, T.; Gaona, X.; Altmaier, M.; Scheinost, A.C.; Fellhauer, D.; European Commission Joint Research Centre, Karlsruhe

    2013-01-01

    Redox behaviour of Tc(VII)/Tc(IV) was investigated in 0.1 M NaCl solutions containing different reducing agents in the pH range 2 to 13 at 22 C under inert Ar atmosphere. In several samples, the 1 x 10 -5 mol/dm 3 (M) initially added TcO 4 - was reduced to form a Tc(IV) oxide solid phase with low solubility. The observed Tc redox transformation processes are systematized according to E h -pH conditions in solution, indicating that a borderline for the reduction of Tc(VII) to Tc(IV), TcO 4 - + 3e - + 4H + TcO 2 . xH 2 O(coll, hyd) + (2-x)H 2 O exists, independent of the reducing chemical system. This experimentally derived borderline is about 100 mV lower than the equilibrium line calculated from the reported standard redox potential of TcO 2 . 1.6H 2 O(s). This behaviour can be related to the existence of more soluble solid phase modifications, i.e. nanoparticulate Tc(IV) oxide species TcO 2 . xH 2 O(coll, hyd). The reaction kinetics likewise correlate to the redox potential measured in solution. Slow reduction of Tc(VII) to Tc(IV) was observed when the redox potential in the system was slightly below the above mentioned reduction borderline. Fast reduction was observed in the systems far below the borderline, but also in those systems containing Fe(II) solids, suggesting a specific surface mediated effect in the reduction process. EXAFS analysis on two magnetite samples indicate reduced Tc(IV) species which do not remain adsorbed at the reactive mineral surface and are incorporated in the magnetite structure. (orig.)

  9. Spectroscopic Properties of Tc(I) Tricarbonyl Species Relevant to the Hanford Tank Waste

    Energy Technology Data Exchange (ETDEWEB)

    Levitskaia, Tatiana G. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Andersen, Amity [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Chatterjee, Sayandev [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Hall, Gabriel B. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Walter, Eric D. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Washton, Nancy M. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2015-12-04

    Technetium-99 (Tc) exists predominately in soluble forms in the liquid supernatant and salt cake fractions of the nuclear tank waste stored at the U.S. DOE Hanford Site. In the strongly alkaline environments prevalent in the tank waste, its dominant chemical form is pertechnetate (TcO4-, oxidation state +7). However, attempts to remove Tc from the Hanford tank waste using ion-exchange processes specific to TcO4- only met with limited success, particularly processing tank waste samples containing elevated concentrations of organic complexants. This suggests that a significant fraction of the soluble Tc can be present as non-pertechnetate low-valent Tc (oxidation state < +7) (non-pertechnetate). The chemical identities of these non-pertechnetate species are poorly understood. Previous analysis of the SY-101 and SY-103 tank waste samples provided strong evidence that non-pertechnetate can be comprised of [Tc(CO)3]+ complexes containing Tc in oxidation state +1 (Lukens et al. 2004). During the last two years, our team has expanded this work and demonstrated that high-ionic-strength solutions typifying tank waste supernatants promote oxidative stability of the [Tc(CO)3]+ species (Rapko et al. 2013; Levitskaia et al. 2014). It also was observed that high-ionic-strength alkaline matrices stabilize Tc(VI) and potentially Tc(IV) oxidation states, particularly in presence organic chelators, suggesting that the relevant Tc compounds can serve as important redox intermediates facilitating the reduction of Tc(VII) to Tc(I). Designing strategies for effective Tc processing, including separation and immobilization, necessitates understanding the molecular structure of these non-pertechnetate species and their identification in the actual tank waste samples. To-date, only limited information exists regarding the nature and characterization of the Tc(I), Tc(IV), and Tc(VI) species. One objective of this project is to

  10. Manufacturing of superconductive silver/ceramic composites

    DEFF Research Database (Denmark)

    Seifi, Behrouz; Bech, Jakob Ilsted; Eriksen, Morten

    2000-01-01

    Manufacturing of superconducting metal/ceramic composites is a rather new discipline within materials forming processes. High Temperature SuperConductors, HTSC, are manufactured applying the Oxide-Powder-In-Tube process, OPIT. A ceramic powder containing lead, calcium, bismuth, strontium, and cop......Manufacturing of superconducting metal/ceramic composites is a rather new discipline within materials forming processes. High Temperature SuperConductors, HTSC, are manufactured applying the Oxide-Powder-In-Tube process, OPIT. A ceramic powder containing lead, calcium, bismuth, strontium...

  11. Superconductivity in Weyl semimetal candidate MoTe{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Qi, Yanpeng; Naumov, Pavel; Rajamathi, Catherine; Barkalov, Oleg; Wu, Shu-Chun; Shekhar, Chandra; Sun, Yan; Suess, Vicky; Schmidt, Marcus; Schwarz, Ulrich; Schnelle, Walter; Felser, Claudia; Medvedev, Sergey [Max Planck Institute for Chemical Physics of Solids, Dresden (Germany); Ali, Mazhar; Cava, Robert [Department of Chemistry, Princeton University, Princeton (United States); Hanfland, Michael [European Synchrotron Radiation Facility, Grenoble (France); Pippel, Eckhard; Werner, Peter; Hillebrand, Reinald; Parkin, Stuart [Max Planck Institute of Microstructure Physics, Halle (Germany); Foerster, Tobias; Kampert, Erik [Dresden High Magnetic Field Laboratory, Dresden (Germany); Yan, Binghai [Max Planck Institute for Chemical Physics of Solids, Dresden (Germany); Max Planck Institute for the Physics of Complex Systems, Dresden (Germany)

    2016-07-01

    In this work, we investigate the sister compound of WTe{sub 2}, MoTe{sub 2}, which is also predicted to be a Weyl semimetal and a quantum spin Hall insulator in bulk and monolayer form, respectively. We find that MoTe{sub 2} exhibits superconductivity with a resistive transition temperature T{sub c} of 0.1 K. The application of a small pressure is shown to dramatically enhance the T{sub c}, with a maximum value of 8.2 K being obtained at 11.7 GPa (a more than 80-fold increase in Tc). This yields a dome-shaped superconducting phase diagram. Further explorations into the nature of the superconductivity in this system may provide insights into the interplay between superconductivity and topological physics.

  12. WORKSHOPS: Radiofrequency superconductivity

    International Nuclear Information System (INIS)

    Anon.

    1992-01-01

    In the continual push towards higher energy particle beams, superconducting radiofrequency techniques now play a vital role, highlighted in the fifth workshop on radiofrequency superconductivity, held at DESY from 19 - 24 August 1991

  13. WORKSHOPS: Radiofrequency superconductivity

    Energy Technology Data Exchange (ETDEWEB)

    Anon.

    1992-01-15

    In the continual push towards higher energy particle beams, superconducting radiofrequency techniques now play a vital role, highlighted in the fifth workshop on radiofrequency superconductivity, held at DESY from 19 - 24 August 1991.

  14. On the structural properties and superconductivity of room-temperature chemically oxidized La2-xBaxCuO4+y (0<=x<=0.15)

    DEFF Research Database (Denmark)

    Rial, C.; Moran, E.; Alario-Franco, M.A.

    1996-01-01

    The insertion of oxygen within the structure of La2-xBaxCuO4+y (x less than or equal to 0.15), by means of room-temperature chemical oxidation, modifies both the physical and the structural features of these materials, Concerning the superconducting properties, the extra oxygen gives rise to an i...

  15. Superconductivity and charge transfer excitations in high Tc superconductors

    International Nuclear Information System (INIS)

    Balseiro, C.A.; Alascio, B.; Gagliano, E.; Rojo, A.

    1988-01-01

    We present some numerical results to show that in a simple model which includes Cu 3d and O 2p orbitals together with inter and intra atomic correlations pairing between holes can occur due to charge transfer excitations. We present also a simple approximation to derive an effective Hamiltonian containing an interaction between particles which is attractive for some values of the different microscopic parameters

  16. High-Tc superconducting Josephson mixers for terahertz heterodyne detection

    International Nuclear Information System (INIS)

    Malnou, M.; Feuillet-Palma, C.; Olanier, L.; Lesueur, J.; Bergeal, N.; Ulysse, C.; Faini, G.; Febvre, P.; Sirena, M.

    2014-01-01

    We report on an experimental and theoretical study of the high-frequency mixing properties of ion-irradiated YBa 2 Cu 3 O 7 Josephson junctions embedded in THz antennas. We investigated the influence of the local oscillator power and frequency on the device performances. The experimental data are compared with theoretical predictions of the general three-port model for mixers in which the junction is described by the resistively shunted junction model. A good agreement is obtained for the conversion efficiency in different frequency ranges, spanning above and below the characteristic frequencies f c of the junctions

  17. Fermi surface of underdoped high-Tc superconducting cuprates

    International Nuclear Information System (INIS)

    Dai, X.; Su, Z.; Yu, L.

    1997-01-01

    The coexistence of a π-flux state and a d-wave resonant-valance-bond (RVB) state is considered in this paper within the slave-boson approach. A critical value of doping concentration δ c is found, below which the coexisting π-flux and d-wave RVB state is favored in energy. The pseudo-Fermi surface of spinons and the physical electron spectral function are calculated. A clear Fermi-level crossing is found along the (0,0) to (π, π) direction, but no such crossing is detected along the (π, 0) to (π, π) direction. Also, an energy gap of d-wave symmetry appears at the Fermi level in our calculation. The above results are in agreement with the angle-resolved photoemission experiments which indicate at a d-wave pseudogap and a half-pocket-like Fermi surface in underdoped cuprates. copyright 1997 The American Physical Society

  18. A magnetic anomaly near Tc in superconducting UPt3

    International Nuclear Information System (INIS)

    Shivaram, B.S.; Gannon, J.J. Jr.; Hinks, D.G.

    1988-12-01

    We report observation of a peak in the r.f. susceptibility of a single crystal of the heavy fermion superconductor UPt 3 . The peak occurs close to but below T c = 0.53 K. In addition our measurements in the low temperature limit (T c ) yield the magnetic field penetration depth in UPt 3 . We obtain a T 4 power law for the penetration depth parallel to the c-axis of the crystal. Based on existing calculations of the penetration depth in anisotropic superconductors we identify the order-parameter in UPt 3 as an odd-parity axial state. 19 refs., 3 figs

  19. Design of Tokamak plasma with high Tc superconducting coils

    International Nuclear Information System (INIS)

    Uchimoto, T.; Miya, K.; Yoshida, Y.; Yamada, T.

    1999-01-01

    This paper presents a design of tokamak plasma in light of how the small ignited tokamak is possible with use of the HTSC coils as plasma stabilizer. The same data base and formulas as ITER are here used and any innovative technology other than the HTSC stabilizing coils is not assumed. (author)

  20. Superconductive materials. Structural mechanisms and nano-structures of some mixed skeletons oxides. Materiaux supraconducteurs. Mecanismes structuraux et nanostructures de quelques oxydes a charpentes mixtes

    Energy Technology Data Exchange (ETDEWEB)

    Hervieu, M [Caen Univ., 14 (France)

    1993-12-01

    Two families of superconductive crystals are described: the phosphate bronze of tungsten family [A[sub x](P[sub 2]O[sub 4])[sub 2](WO[sub 3])[sub 2m] or (PO[sub 2])[sub 4](WO[sub 3])[sub 2m] or A[sub x](PO[sub 2])[sub 4](WO[sub 3])[sub 2m

  1. Superconductivity in the background of disordered flux state of spins

    International Nuclear Information System (INIS)

    Feng Shiping; Guo Rui; Han Fei

    1992-01-01

    The phase diagram of the copper oxide materials with the antiferromagnetic and the superconducting properties as a function of doping δ is obtained in the framework of the t-J model by using the Schwinger boson-slave fermion theory. The results show that the spiral order of spins competes and coexists with superconductivity for small doping δ. For large doping δ, superconductivity appears, which may be caused by the occurrence of a disordered flux state of spins. The phase diagram suggests a strong relationship between antiferromagnetism and superconductivity. (orig.)

  2. Mechanochemical effects on high-Tc superconductor powders

    International Nuclear Information System (INIS)

    Yamada, Taichi; Nagai, Ryoji; Takeuchi, Manabu; Minehara, Eisuke.

    1991-03-01

    We have investigated the mechanochemical effects on high-Tc superconductor (YBa 2 Cu 3 O 7 -δ) powders. The powder was mechanically ground in air using an agate mortar with a pestle. The grinding time was varied from 2 to 100 min. The mean particle sizes of the powders were measured by a sedimentation method. The degradation of superconductivity was evaluated by the measurements of the crystallinity and volume fraction of the superconducting phase. The crystallinity was estimated from X-ray diffraction patterns. The volume fraction of the superconducting phase was estimated from the diamagnetization. The results of these changes of 2 min. and 100 min. grinding are respectively as follows; 1) mean particle size: 10.8 μm and 7.2 μm, 2) crystallinity: 40.0 % and 24.8 %, 3) volume fraction of superconducting phase: 91.5 % and 30.0 %. Recovery of the crystallinity and superconductivity of the ground specimens by re-sintering and re-annealing was also studied. It was found that the recovery of both of the characteristics was not complete. (author)

  3. On characteristic voltage of the high Tc superconductor. [Y-Ba-Cu-O

    Energy Technology Data Exchange (ETDEWEB)

    Vasiliev, B V; Uchaikin, S V [Joint Inst. for Nuclear Research, Low Temperature Physics Dept., Dubna (USSR)

    1991-12-01

    The critical currents and normal resistances of the small bridges from yttrium-based high-Tc superconducting ceramics have been measured. The characteristic voltage of these bridges was found to be approximately 20{mu}V. This effect can be explained if between the ceramic grains there are contacts of an order of one crystalline cell in size. (orig.).

  4. Superconducting current in a bisoliton superconductivity model

    International Nuclear Information System (INIS)

    Ermakov, V.N.; Kruchinin, S.P.; Ponezha, E.A.

    1991-01-01

    It is shown that the transition into a superconducting state with the current which is described by a bisoliton superconductivity model is accompanied by the deformation of the spectrum of one-particle states of the current carriers. The deformation value is proportional to the conducting current force. The residuaby resistance in such state is absent

  5. Synthesis of a Novel Energetic Heterocyclic Oxidizer with Higher Energy and Lower Sensitivity (Phase 2) Final Report CRADA No. TC02125.0

    Energy Technology Data Exchange (ETDEWEB)

    Pagoria, P. F. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Racoveanu, A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2017-09-08

    This project was a continuation of work originally performed under a Phase 1 of the Small Business Technology Transfer (STIR). The success of the Phase 1 led to the award of a Phase 2 of the STIR. In Phase 1 of the STIR, the target energetic compound, 3,4-bis(4-nitro-l,2,5- oxadiazol-3yl)-1,2,5-oxadiazole-l-oxide (DNTF), was synthesized at the 5g scale and small-scale safety tests were performed. DNTF showed promising performance· and safety properties. DNTF was shown to be relatively insensitive while performing better than the current industry standard, H1vIX, in solid propellant formulations. Because of the successful research and development project involving PSI, LLNL and Aerojet in Phase I of the STIR, the sponsors wanted to obtain larger quantities of DNTF for further testing.

  6. Midwest Superconductivity Consortium: 1995 Progress report

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-01-01

    The mission of the Midwest Superconductivity Consortium, MISCON, is to advance the science and understanding of high Tc superconductivity. During the past year, 26 projects produced over 133 talks and 127 publications. Three Master`s Degrees and 9 Doctor`s of Philosophy Degrees were granted to students working on MISCON projects. Group activities and interactions involved 2 MISCON group meetings (held in January and July); the third MISCON Summer School held in July; 12 external speakers; 81 collaborations (with universities, industry, Federal laboratories, and foreign research centers); and 54 exchanges of samples and/or measurements. Research achievements this past year focused on understanding the effects of processing phenomena on structure-property interrelationships and the fundamental nature of transport properties in high-temp superconductors.

  7. Midwest Superconductivity Consortium: 1995 Progress report

    International Nuclear Information System (INIS)

    1996-01-01

    The mission of the Midwest Superconductivity Consortium, MISCON, is to advance the science and understanding of high Tc superconductivity. During the past year, 26 projects produced over 133 talks and 127 publications. Three Master's Degrees and 9 Doctor's of Philosophy Degrees were granted to students working on MISCON projects. Group activities and interactions involved 2 MISCON group meetings (held in January and July); the third MISCON Summer School held in July; 12 external speakers; 81 collaborations (with universities, industry, Federal laboratories, and foreign research centers); and 54 exchanges of samples and/or measurements. Research achievements this past year focused on understanding the effects of processing phenomena on structure-property interrelationships and the fundamental nature of transport properties in high-temp superconductors

  8. Anomalous electron doping independent two-dimensional superconductivity

    Science.gov (United States)

    Zhou, Wei; Xing, Xiangzhuo; Zhao, Haijun; Feng, Jiajia; Pan, Yongqiang; Zhou, Nan; Zhang, Yufeng; Qian, Bin; Shi, Zhixiang

    2017-07-01

    Transition metal (Co and Ni) co-doping effects are investigated on an underdoped Ca0.94La0.06Fe2As2 compound. It is discovered that electron doping from substituting Fe with transition metal (TM = Co, Ni) can trigger high-{T}{{c}} superconductivity around 35 K, which emerges abruptly before the total suppression of the innate spin-density-wave/anti-ferromagnetism (SDW/AFM) state. Remarkably, the critical temperature for the high-{T}{{c}} superconductivity remains constant against a wide range of TM doping levels. And the net electron doping density dependence of the superconducting {T}{{c}} based on the rigid band model can be nicely scaled into a single curve for Co and Ni substitutions, in stark contrast to the case of Ba(Fe1-x TM x )2As2. This carrier density independent superconductivity and the unusual scaling behavior are presumably resulted from the interface superconductivity based on the similarity with the interface superconductivity in a La2-x Sr x CuO4-La2CuO4 bilayer. Evidence of the two-dimensional character of the superfluid by angle-resolved magneto-resistance measurements can further strengthen the interface nature of the high-{T}{{c}} superconductivity.

  9. Enhanced superconductivity of fullerenes

    Energy Technology Data Exchange (ETDEWEB)

    Washington, II, Aaron L.; Teprovich, Joseph A.; Zidan, Ragaiy

    2017-06-20

    Methods for enhancing characteristics of superconductive fullerenes and devices incorporating the fullerenes are disclosed. Enhancements can include increase in the critical transition temperature at a constant magnetic field; the existence of a superconducting hysteresis over a changing magnetic field; a decrease in the stabilizing magnetic field required for the onset of superconductivity; and/or an increase in the stability of superconductivity over a large magnetic field. The enhancements can be brought about by transmitting electromagnetic radiation to the superconductive fullerene such that the electromagnetic radiation impinges on the fullerene with an energy that is greater than the band gap of the fullerene.

  10. Superconductivity in Medicine

    Science.gov (United States)

    Alonso, Jose R.; Antaya, Timothy A.

    2012-01-01

    Superconductivity is playing an increasingly important role in advanced medical technologies. Compact superconducting cyclotrons are emerging as powerful tools for external beam therapy with protons and carbon ions, and offer advantages of cost and size reduction in isotope production as well. Superconducting magnets in isocentric gantries reduce their size and weight to practical proportions. In diagnostic imaging, superconducting magnets have been crucial for the successful clinical implementation of magnetic resonance imaging. This article introduces each of those areas and describes the role which superconductivity is playing in them.

  11. Depth profiling of superconducting thin films using rare gas ion sputtering with laser postionization

    Science.gov (United States)

    Pallix, J. B.; Becker, C. H.; Missert, N.; Char, K.; Hammond, R. H.

    1988-02-01

    Surface analysis by laser ionization (SALI) has been used to examine a high-Tc superconducting thin film of nominal composition YBa2Cu3O7 deposited on SrTiO3 (100) by reactive magnetron sputtering. The main focus of this work was to probe the compositional uniformity and the impurity content throughout the 1800 Å thick film having critical current densities of 1 to 2×106 A/cm2. SALI depth profiles show this film to be more uniform than thicker films (˜1 μm, prepared by electron beam codeposition) which were studied previously, yet the data show that some additional (non-superconducting) phases derived from Y, Ba, Cu, and O are still present. These additional phases are studied by monitoring the atomic and diatomic-oxide photoion profiles and also the depth profiles of various clusters (e.g. Y2O2+, Y2O3+, Y3O4+, Ba2O+, Ba2O2+, BaCu+, BaCuO+, YBaO2+, YSrO2+, etc.). A variety of impurities are observed to occur throughout the film including rather large concentrations of Sr. Hydroxides, F, Cl, and COx are evident particularly in the sample's near surface region (the top ˜100 Å).

  12. Relaxation of polarized nuclei in superconducting rhodium

    DEFF Research Database (Denmark)

    Knuuttila, T.A.; Tuoriniemi, J.T.; Lefmann, K.

    2000-01-01

    Nuclear spin lattice relaxation rates were measured in normal and superconducting (sc) rhodium with nuclear polarizations up to p = 0.55. This was sufficient to influence the sc state of Rh, whose T, and B-c, are exceptionally low. Because B-c ... is unchanged, the nuclear spin entropy was fully sustained across the sc transition. The relaxation in the sc state was slower at all temperatures without the coherence enhancement close to T-c. Nonzero nuclear polarization strongly reduced the difference between the relaxation rates in the sc and normal...

  13. Electron-phonon superconductivity in YIn3

    Science.gov (United States)

    Billington, D.; Llewellyn-Jones, T. M.; Maroso, G.; Dugdale, S. B.

    2013-08-01

    First-principles calculations of the electron-phonon coupling were performed on the cubic intermetallic compound YIn3. The electron-phonon coupling constant was found to be λep = 0.42. Using the Allen-Dynes formula with a Coulomb pseudopotential of μ* = 0.10, a Tc of approximately 0.77 K is obtained which is reasonably consistent with the experimentally observed temperature (between 0.8 and 1.1 K). The results indicate that conventional electron-phonon coupling is capable of producing the superconductivity in this compound.

  14. Effect of milking efficiency on Tc-99 content of Tc-99m derived from Tc-99m generators

    International Nuclear Information System (INIS)

    Bonnyman, J.

    1983-01-01

    Tc-99m obtained by separation from its parent Mo-99 always contains Tc-99 produced by decay of Tc-99m and Mo-99. Factors effecting the Tc-99/Tc-99m ratios are discussed. An HPLC method has been developed to measure the 99 TcO 4- content of sodium pertechnetate from generators with a detection limit of 0.9 ng Tc-99 for a 500 μl/ aliquot of TcO 4- -99m. First eluates of 10 chromatograph-ic generators gave Tc-99/Tc-99m ratios ranging from 3.5-46 ng Tc/mCi Tc-99m measured at the time of milking. The measurements indicate that Tc-99/Tc-99m ratios high enough to cause adverse labelling effects could be found in 'instant pertechnetate' and in the first eluate from Tc-99m generators for the activities normally used in radiopharmaceutical production

  15. Superconductivity in transition metals.

    Science.gov (United States)

    Slocombe, Daniel R; Kuznetsov, Vladimir L; Grochala, Wojciech; Williams, Robert J P; Edwards, Peter P

    2015-03-13

    A qualitative account of the occurrence and magnitude of superconductivity in the transition metals is presented, with a primary emphasis on elements of the first row. Correlations of the important parameters of the Bardeen-Cooper-Schrieffer theory of superconductivity are highlighted with respect to the number of d-shell electrons per atom of the transition elements. The relation between the systematics of superconductivity in the transition metals and the periodic table high-lights the importance of short-range or chemical bonding on the remarkable natural phenomenon of superconductivity in the chemical elements. A relationship between superconductivity and lattice instability appears naturally as a balance and competition between localized covalent bonding and so-called broken covalency, which favours d-electron delocalization and superconductivity. In this manner, the systematics of superconductivity and various other physical properties of the transition elements are related and unified. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

  16. Superconductivity in ThPd2Ge2

    Science.gov (United States)

    Domieracki, Krzysztof; Wiśniewski, Piotr; Wochowski, Konrad; Romanova, Tetiana; Hackemer, Alicja; Gorzelniak, Roman; Pikul, Adam; Kaczorowski, Dariusz

    2018-05-01

    Our on-going search for unconventional superconductors among the ThTE2Ge2 phases (TE is a d-electron transition metal) revealed that ThPd2Ge2, which crystallizes with a body-centered tetragonal ThCr2Si2-type structure, exhibits superconductivity at low temperatures. In this paper, we report on the electrical transport and thermodynamic properties of a polycrystalline sample of this new superconductor, extended down to 50 mK. The experimental data indicates weakly-coupled type-II superconductivity with Tc = 0.63(2) K and μ0Hc2(0) = 32(2) mT.

  17. Pretreatment of Tc-Containing Waste and Its Effect on Tc-99 Leaching From Grouts

    International Nuclear Information System (INIS)

    Aloy, Albert; Kovarskaya, Elena N.; Harbour, John R.; Langton, Christine A.; Holtzscheiter, E. William

    2007-01-01

    A salt solution (doped with Tc-99), that simulates the salt waste stream to be processed at the Saltstone Production Facility, was immobilized in grout waste forms with and without (1) ground granulated blast furnace slag and (2) pretreatment with iron salts. The degree of immobilization of Tc-99 was measured through monolithic and crushed grout leaching tests. Although Fe (+2) was shown to be effective in reducing Tc-99 to the +4 state, the strong reducing nature of the blast furnace slag present in the grout formulation dominated the reduction of Tc-99 in the cured grouts. An effective diffusion coefficient of 4.75 x 10 -12 (Leach Index of 11.4) was measured using the ANSI/ANS-16.1 protocol. The leaching results show that, even in the presence of a concentrated salt solution, blast furnace slag can effectively reduce pertechnetate to the immobile +4 oxidation state. The measured diffusivity was introduced into a flow and transport model (PORFLOW) to calculate the release of Tc-99 from a Saltstone Vault as a function of hydraulic conductivity of the matrix. (authors)

  18. PREFACE: ISEC 2005: The 10th International Superconductive Electronics Conference

    Science.gov (United States)

    Rogalla, Horst

    2006-05-01

    The 10th International Superconductive Electronics Conference took place in Noordwijkerhout in the Netherlands, 5-9 September 2005, not far from the birthplace of superconductivity in Leiden nearly 100 years ago. There have been many reasons to celebrate the 10th ISEC: not only was it the 20th anniversary, but also the achievements since the first conference in Tokyo in 1987 are tremendous. We have seen whole new groups of superconductive materials come into play, such as oxide superconductors with maximum Tc in excess of 100 K, carbon nanotubes, as well as the realization of new digital concepts from saturation logic to the ultra-fast RSFQ-logic. We have learned that superconductors not only show s-wave symmetries in the spatial arrangement of the order parameter, but also that d-wave dependence in oxide superconductors is now well accepted and can even be successfully applied to digital circuits. We are now used to operating SQUIDs in liquid nitrogen; fT sensitivity of SQUID magnetometers is not surprising anymore and can even be reached with oxide-superconductor based SQUIDs. Even frequency discriminating wide-band single photon detection with superconductive devices, and Josephson voltage standards with tens of thousands of junctions, nowadays belong to the daily life of advanced laboratories. ISEC has played a very important role in this development. The first conferences were held in 1987 and 1989 in Tokyo, and subsequently took place in Glasgow (UK), Boulder (USA), Nagoya (Japan), Berlin (Germany), Berkeley (USA), Osaka (Japan), Sydney (Australia), and in 2005 for the first time in the Netherlands. These conferences have provided platforms for the presentation of the research and development results of this community and for the vivid discussion of achievements and strategies for the further development of superconductive electronics. The 10th conference has played a very important role in this context. The results in laboratories show great potential and

  19. Full-switching FSF-type superconducting spin-triplet magnetic random access memory element

    Science.gov (United States)

    Lenk, D.; Morari, R.; Zdravkov, V. I.; Ullrich, A.; Khaydukov, Yu.; Obermeier, G.; Müller, C.; Sidorenko, A. S.; von Nidda, H.-A. Krug; Horn, S.; Tagirov, L. R.; Tidecks, R.

    2017-11-01

    In the present work a superconducting Co/CoOx/Cu41Ni59 /Nb/Cu41Ni59 nanoscale thin film heterostructure is investigated, which exhibits a superconducting transition temperature, Tc, depending on the history of magnetic field applied parallel to the film plane. In more detail, around zero applied field, Tc is lower when the field is changed from negative to positive polarity (with respect to the cooling field), compared to the opposite case. We interpret this finding as the result of the generation of the odd-in-frequency triplet component of superconductivity arising at noncollinear orientation of the magnetizations in the Cu41Ni59 layer adjacent to the CoOx layer. This interpretation is supported by superconducting quantum interference device magnetometry, which revealed a correlation between details of the magnetic structure and the observed superconducting spin-valve effects. Readout of information is possible at zero applied field and, thus, no permanent field is required to stabilize both states. Consequently, this system represents a superconducting magnetic random access memory element for superconducting electronics. By applying increased transport currents, the system can be driven to the full switching mode between the completely superconducting and the normal state.

  20. Influence of laser sputtering parameters on orientation of cerium oxide buffer layer on sapphire and properties of YBa2Cu3Ox superconducting film

    International Nuclear Information System (INIS)

    Mozhaev, P.B.; Ovsyannikov, G.A.; Skov, J.L.

    1999-01-01

    Effect of laser sputtering parameters on crystalline properties of CeO 2 buffer layers grown on (1102) orientation sapphire substrate and on properties of YBa 2 Cu 3 O x superconducting thin films was studied. It was shown that depending on the sputtering conditions one might observe growth of CeO 2 (100) and (111) orientations. Varying heater temperature, chamber pressure and density of laser ray energy on the target one managed to obtain mono-oriented buffer layer of the desired orientation [ru