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Sample records for superconducting cu oxides

  1. 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.

  2. 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.

  3. Characterization of transparent superconductivity Fe-doped CuCrO2 delafossite oxide

    Science.gov (United States)

    Taddee, Chutirat; Kamwanna, Teerasak; Amornkitbamrung, Vittaya

    2016-09-01

    Delafossite CuCr1-xFexO2 (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 CuCr1-xFexO2 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 CuCrO2 samples exhibited ferromagnetic behavior at room temperature. This indicated that the substitution of Fe3+ for Cr3+ produced a mixed effect on the magnetic properties of CuCrO2 delafossite oxide. The temperature dependent resistivity measurements clearly revealed the presence of superconductivity in the CuCr1-xFexO2 with a superconducting transition up to 118 K.

  4. Ionic Model of Some Aspects of Cu NQR Spectra in Superconducting Oxides

    Science.gov (United States)

    Shimizu, Tadashi

    1993-02-01

    We apply an ionic model to explain the pressure and the temperature dependences of copper nuclear quadrupole frequency νQ in superconducting oxides. The pressure and the temperature dependences of νQ can, for the most part, be explained only by the change in the lattice spacing. It has also been shown that the origin of large difference in the 63Cu NQR line width between crystallographically different copper sites in YBa2Cu3O6.5 can be explained in the same model. The result of the present study suggests that the Sternheimer antishielding factor γ∞ is certainly effective in the case of ionic model, although a negligibly small value has been argued from viewpoint of the band calculation.

  5. Superconductivity of Nd1.85Ce0.15CuO4-y by Electrochemical Oxidation

    Institute of Scientific and Technical Information of China (English)

    CHEN Ling; CHE Guang-Can; LI Hong; DONG Cheng; ZHOU Fang; HUANG Yu-Zhen; ZHAO Zhong-Xian

    2000-01-01

    Superconductivity of n-type superconductor Nd1.85Ce0.15CuO4-y (NCCO) by electrochemical oxidation is re ported for the first time and the cyclic voltammogram curve for NCCO as working electrode is presented. In vestigations indicate that after oxidation, superconductivity of NCCO is improved: Tc is raised from 20 K up to 26 K, the superconducting volume fraction is increased also. The valence electronic states of oxygen and copper in NCCO are studied by x-ray photoelectron spectroscopy. It is found that the Cu-2ps/2 peak shifts to the higher binding energy side about 0.4 e V, which indicates that the valence-state of copper ions is risen up after oxidation. These results imply that hole-carriers exist in n-type superconductor.

  6. High-T(c) Superconductivity at the Interface between the CaCuO2 and SrTiO3 Insulating Oxides.

    Science.gov (United States)

    Di Castro, D; Cantoni, C; Ridolfi, F; Aruta, C; Tebano, A; Yang, N; Balestrino, G

    2015-10-02

    At interfaces between complex oxides it is possible to generate electronic systems with unusual electronic properties, which are not present in the isolated oxides. One important example is the appearance of superconductivity at the interface between insulating oxides, although, until now, with very low T(c). We report the occurrence of high T(c) superconductivity in the bilayer CaCuO(2)/SrTiO(3), where both the constituent oxides are insulating. In order to obtain a superconducting state, the CaCuO(2)/SrTiO(3) interface must be realized between the Ca plane of CaCuO(2) and the TiO(2) plane of SrTiO(3). Only in this case can oxygen ions be incorporated in the interface Ca plane, acting as apical oxygen for Cu and providing holes to the CuO(2) planes. A detailed hole doping spatial profile can be obtained by scanning transmission electron microscopy and electron-energy-loss spectroscopy at the O K edge, clearly showing that the (super)conductivity is confined to about 1-2 CaCuO(2) unit cells close to the interface with SrTiO(3). The results obtained for the CaCuO(2)/SrTiO(3) interface can be extended to multilayered high T(c) cuprates, contributing to explaining the dependence of T(c) on the number of CuO(2) planes in these systems.

  7. Superconducting YBa2Cu3O(7-delta) thin films on GaAs with conducting indium-tin-oxide buffer layers

    Science.gov (United States)

    Kellett, B. J.; Gauzzi, A.; James, J. H.; Dwir, B.; Pavuna, D.

    1990-12-01

    Superconducting YBa2Cu3O(7-delta) (YBCO) thin films have been grown in situ on GaAs with conducting indium-tin-oxide (ITO) buffer layers. Superconducting onset is about 92 K with zero resistance at 60 K. ITO buffer layers usually form Schottky-like barriers on GaAs. The YBCO film and ITO buffer layer, grown by ion beam sputter codeposition, are textured and polycrystalline with a combined room-temperature resistivity of about 1 milliohm cm.

  8. 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...

  9. 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...... and differences concerning the modifications induced by this oxidation process in the present series of La2-xBaxCuO4+y compounds and in equivalent La2-xSrxCuO4+y materials are discussed....

  10. Dimensionality of high temperature superconductivity in oxides

    Science.gov (United States)

    Chu, C. W.

    1989-01-01

    Many models have been proposed to account for the high temperature superconductivity observed in oxide systems. Almost all of these models proposed are based on the uncoupled low dimensional carrier Cu-O layers of the oxides. Results of several experiments are presented and discussed. They suggest that the high temperature superconductivity observed cannot be strictly two- or one-dimensional, and that the environment between the Cu-O layers and the interlayer coupling play an important role in the occurrence of such high temperature superconductivity. A comment on the very short coherence length reported is also made.

  11. In situ growth of superconducting YBa sub 2 Cu sub 3 O sub 7 minus. delta. thin films on Si with conducting indium-tin-oxide buffer layers

    Energy Technology Data Exchange (ETDEWEB)

    Kellett, B.J.; James, J.H.; Gauzzi, A.; Dwir, B.; Pavuna, D.; Reinhart, F.K. (Institute of Micro and Optoelectronics, Ecole Polytechnique Federale de Lausanne, CH-1015, Lausanne (Switzerland))

    1990-09-10

    Superconducting YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} (YBCO) thin films have been grown {ital in} {ital situ} on Si with conducting indium-tin-oxide (ITO) buffer layers. ITO allows YBCO to be electrically connected to the underlying Si substrate. Both the YBCO film and ITO buffer layer, grown by ion beam sputtering, are textured and polycrystalline with a combined room- temperature resistivity of about 2 m{Omega} cm. Superconducting onsets are 92 K with zero resistance at 68 K.

  12. Superconducting YBa sub 2 Cu sub 3 O sub 7 minus. delta. thin films on GaAs with conducting indium-tin-oxide buffer layers

    Energy Technology Data Exchange (ETDEWEB)

    Kellett, B.J.; Gauzzi, A.; James, J.H.; Dwir, B.; Pavuna, D.; Reinhart, F.K. (Institut de Micro et Optoelectronique, Ecole Polytechnique Federale de Lausanne, CH-1015, Lausanne (CH))

    1990-12-10

    Superconducting YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} (YBCO) thin films have been grown {ital in} {ital situ} on GaAs with conducting indium-tin-oxide (ITO) buffer layers. Superconducting onset is about 92 K with zero resistance at 60 K. ITO buffer layers usually form Schottky-like barriers on GaAs. The YBCO film and ITO buffer layer, grown by ion beam sputter codeposition, are textured and polycrystalline with a combined room-temperature resistivity of about 1 m{Omega} cm.

  13. A study of mixed phase behavior in the lanthanide-substituted superconducting oxide ErBa sub 2 Cu sub 3 O sub 7

    Energy Technology Data Exchange (ETDEWEB)

    Zandbergen, H.W.; Holland, G.F.; Tejedor, P.; Gronsky, R.; Stacy, A.M. (Univ. of California, Berkeley (USA))

    1987-07-01

    Substitution of lanthanide ions, Ln{sup 3+}, for Y in the novel superconducting oxide YBa{sub 2}Cu{sub 3}O{sub 7} has been studied largely to investigate the effect of magnetic 4f{sup n} ions on superconductivity. A possibility that should also be considered however is that slight variation in the size of the lanthanide ions might lead to different structural types. For instance, La does not form the YBa{sub 2}Cu{sub 3}O{sub 7} structure, preferring instead the La{sub 3}Ba{sub 3}Cu{sub 6}O{sub 4} habit. Changes in the size of Ln could also be important on the microscopic scale, where different defect structures could occur. Defects as well as other impurities will adversely affect the current carrying capacity, J{sub c}, of these new high T{sub c} superconductors. The challenge in improving the performance of the Y-Ba-Cu-O type superconductors is to develop an understanding of the relationship between their fabrication, processing, performance, and microstructure. Here the authors report the synthesis and characterization, both magnetic and structural of ErBa{sub 2}Cu{sub 3}O{sub 7}. High resolution electron micrographs show the presence of an unusual defect structure in this pure phase.

  14. 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

    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(c)s......The insertion of an excess of oxygen within the structure of La2-xCaxCuO4 (x less than or equal to 0.12) by means of room temperature chemical oxidation modifies the physical properties and the crystal structure of these cuprates. The superconducting features of the starting La2-xCaxCuO4 samples....... This decrease of T-c is connected with the ability of these compounds to incorporate extra oxygen, which decreases as the Ca-doping increases and is controlled by a structural limit. The behavior of the La2-xCaxCuO4 materials under the oxidation process and the changes induced by the interstitial oxygen...

  15. Superconductivity of Cu/CuOx interface formed by shock-wave pressure

    Science.gov (United States)

    Shakhray, D. V.; Avdonin, V. V.; Palnichenko, A. V.

    2016-11-01

    A mixture of powdered Cu and CuO has been subjected to shock-wave pressure of 350 kbar with following quenching of the vacuum-encapsulated product to 77 K. The ac magnetic susceptibility measurements of the samples have revealed metastable superconductivity with Tc ≈ 19 K, characterized by glassy dynamics of the shielding currents below Tc . Comparison of the ac susceptibility and the DC magnetization measurements infers that the superconductivity arises within the granular interfacial layer formed between metallic Cu and its oxides due to the shock-wave treatment.

  16. A novel pre-sintering technique for the growth of Y-Ba-Cu-O superconducting single grains from raw metal oxides

    Science.gov (United States)

    Li, Jiawei; Shi, Yun-Hua; Dennis, Anthony R.; Namburi, Devendra Kumar; Durrell, John H.; Yang, Wanmin; Cardwell, David A.

    2017-09-01

    Most established top seeded melt growth (TSMG) processes of bulk, single grain Y-Ba-Cu-O (YBCO) superconductors are performed using a mixture of pre-reacted precursor powders. Here we report the successful growth of large, single grain YBCO samples by TSMG with good superconducting properties from a simple precursor composition consisting of a sintered mixture of the raw oxides. The elimination of the requirement to synthesize precursor powders in a separate process prior to melt processing has the potential to reduce significantly the cost of bulk superconductors, which is essential for their commercial exploitation. The growth morphology, microstructure, trapped magnetic field and critical current density, J c, at different positions within the sample and maximum levitation force of the YBCO single grains fabricated by this process are reported. Measurements of the superconducting properties show that the trapped filed can reach 0.45 T and that a zero field J c of 2.5 × 104 A cm-2 can be achieved in these samples. These values are comparable to those observed in samples fabricated using pre-reacted, high purity commercial oxide precursor powders. The experimental results are discussed and the possibility of further improving the melt process using raw oxides is outlined.

  17. Superconducting YBa2Cu3O7 films on Si and GaAs with conducting indium tin oxide buffer layers

    Science.gov (United States)

    James, J. H.; Kellett, B. J.; Gauzzi, A.; Dwir, B.; Pavuna, D.

    1991-03-01

    Superconducting YBa2Cu3O7-delta (YBCO) thin films have been grown in situ by ion beam sputtering on Si and GaAs substrates with intermediate, conducting Indium Tin Oxide (ITO) buffer layers. Uniform, textured YBCO films on ITO exhibit Tc onset at 92K and Tc0 at 68K and 60K on Si and GaAs substrates respectively, the latter value is the highest Tc reported on GaAs. YBCO/ITO films exhibit metallic resistivity behavior. In situ YBCO films on SrTiO3 show Tc onset = 92K and Tc0 = 90.5K, transition widths are less than 1K. A simple optical bolometer has been constructed from YBCO films on SrTiO3. Tunnelling measurements have also been carried out using the first YBCO-Pb window-type tunnel junctions.

  18. Electronic structures, hole-doping, and superconductivity of the s = 1, 2, 3, and 4 members of the (Cu,Mo)-12s2 homologous series of superconductive copper oxides.

    Science.gov (United States)

    Grigoraviciute, Inga; Karppinen, Maarit; Chan, Ting-Shan; Liu, Ru-Shi; Chen, Jin-Ming; Chmaissem, Omar; Yamauchi, Hisao

    2010-01-20

    We demonstrate that the T(c) value of superconductive copper oxides does not depend on the distance between two adjacent CuO(2) planes as long as the hole-doping level and the immediate (crystal) chemical surroundings of the planes are kept the same. Experimental evidence is accomplished for the homologous series of (Cu,Mo)-12s2, the member phases of which differ from each other by the number (s) of cation layers in the fluorite-structured (Ce,Y)-[O(2)-(Ce,Y)](s-1) block between the CuO(2) planes. X-ray absorption near-edge structure spectroscopy is employed as a probe for the hole states of these phases. The s = 1 member appears to be more strongly doped with holes than other phases of the series and accordingly to possess the highest T(c) value of 87 K. For s > or = 2, unexpectedly, both the CuO(2) plane hole concentration and the value of T(c) (approximately 55 K) remain constant, being independent of s.

  19. Superconducting interfaces between insulating oxides.

    Science.gov (United States)

    Reyren, N; Thiel, S; Caviglia, A D; Kourkoutis, L Fitting; Hammerl, G; Richter, C; Schneider, C W; Kopp, T; Rüetschi, A-S; Jaccard, D; Gabay, M; Muller, D A; Triscone, J-M; Mannhart, J

    2007-08-31

    At interfaces between complex oxides, electronic systems with unusual electronic properties can be generated. We report on superconductivity in the electron gas formed at the interface between two insulating dielectric perovskite oxides, LaAlO3 and SrTiO3. The behavior of the electron gas is that of a two-dimensional superconductor, confined to a thin sheet at the interface. The superconducting transition temperature of congruent with 200 millikelvin provides a strict upper limit to the thickness of the superconducting layer of congruent with 10 nanometers.

  20. Superconductivity in Zigzag CuO Chains

    Energy Technology Data Exchange (ETDEWEB)

    Berg, E.

    2010-04-06

    Superconductivity has recently been discovered in Pr{sub 2}Ba{sub 4}Cu{sub 7}O{sub 15-{delta}} with a maximum T{sub c} of about 15K. Since the CuO planes in this material are believed to be insulating, it has been proposed that the superconductivity occurs in the double (or zigzag) CuO chain layer. On phenomenological grounds we propose a theoretical interpretation of the experimental results in terms of a new phase for the zigzag chain, labelled by C{sub 1}S{sub 3/2}. This phase has a gap in the relative charge mode and a partial gap in the relative spin mode. It has gapless uniform charge and spin excitations and can have a divergent superconducting susceptibility, even for repulsive interactions. A microscopic model for the zigzag CuO chain is proposed, and on the basis of density matrix renormalization group (DMRG) and bosonization studies, we adduce evidence that supports our proposal.

  1. New superconducting oxides in the Bi-Sr-Ca-Cu-0 system: magnetic measurements and structural determination

    Energy Technology Data Exchange (ETDEWEB)

    Giordanengo, B.; Godinho, M.; Lejay, P.; De Rango, P.; Sulpice, A.; Tholence, J.L.; Tournier, R. (Centre National de la Recherche Scientifique, 38 - Grenoble (FR) Centre de Recherches sur les Tres Basses Temperatures, Grenoble, (FR)); Hewat, A.W. (Institut Max Von Laue - Paul Langevin, 38 - Grenoble (FR)); Hewat, E.A. (CEA Centre d' Etudes Nucleaires de Grenoble 38 (FR). Inst. de Recherche Technologique et de Developpement Industriel (IRDI)); Marezio, M. (AT and T Bell Lab., Murray Hill, NJ (US)); Bordet, P.; Capponi, J.J.; Chaillout, C.; Chenavas, J.J.; Hodeau, J.L.; Spieser, A.M.; Tranqui, D. (Centre National de la Recherche Scientifique, 38 - Grenoble (FR) Lab. de Cristallographie (FR))

    1988-12-01

    Detailed neutron diffraction structure analysis of Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} is reported. The effects of Pb-substitution on Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} and Bi{sub 2}Sr{sub 2}CuO{sub 6} are discussed, and magnetization measurement results on the 110 K phase in the Bi-Sr-Ca-Cu-O system are given.

  2. Structure and superconductivity of room temperature chemically oxidized La2-xNdxCuO4+y (0<=x<=0.5)

    DEFF Research Database (Denmark)

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

    1997-01-01

    of oxygen introduced in the semiconducting starting materials relieves partially the distortion of the structure, which increases for increasing Nd content, and provides the hole doping required for superconductivity. The extra oxygen content decreases along this series of compounds as the Nd......-doping increases, probably due to the progressive contraction of the structure along the c-axis. Analogies and differences in the modifications induced by the oxidation process in the present La2-xNdxCuO4+y materials and in related compounds La2-x(Ca/Sr/Ba)(x)CuO4+y (x less than or equal to 0.15) are reported...

  3. Superconductive articles including cerium oxide layer

    Science.gov (United States)

    Wu, Xin D.; Muenchausen, Ross E.

    1993-01-01

    A ceramic superconductor comprising a metal oxide substrate, a ceramic high temperature superconductive material, and a intermediate layer of a material having a cubic crystal structure, said layer situated between the substrate and the superconductive material is provided, and a structure for supporting a ceramic superconducting material is provided, said structure comprising a metal oxide substrate, and a layer situated over the surface of the substrate to substantially inhibit interdiffusion between the substrate and a ceramic superconducting material deposited upon said structure.

  4. Superconductivity in the Sn-Ba-Sr-Y-Cu-O system

    Science.gov (United States)

    Aleksandrov, K. S.; Khrustalev, B. P.; Krivomazov, S. N.; Petrov, M. I.; Vasilyev, A. D.; Zwegintsev, S. A.

    1991-01-01

    After the discovery of high-T(sub c) superconductivity in the La-Ba-Cu-O compound, several families of superconducting oxides were synthesized. Here, researchers report the results of the search for superconductivity in the compounds based on tin which has a lone electron pair like Bi, Tl, and Pb. The following compounds were synthesized: Sn1Ba1Sr1Cu3O(sub x), Sn1Ba1Ca1Cu3O(sub x), Sn1Ba1Mg1Cu3O(sub x), Sn1Sr1Ca1Cu3O(sub x), Sn1Sr1Mg1Cu3O(sub x), and Sn1Ca1Mg1Cu3O(sub x). The initial components were oxides and carbonates of the appropriate elements. A standard firing-grinding procedure was used. Final heating was carried out at 960 C during 12 hours. Then the samples were cooled inside the furnace. All the synthesis cycles were carried out in air atmosphere. Among the synthesized compounds only Sn1Ba1Sr1Cu3O(sub x) showed remarkable conductivity. Other compounds were practically dielectrics. Presence of a possible superconductivity in Sn1Ba1Sr1Cu3O(sub x) was defined by using the Meissner effect. At low temperature a deviation from paramagnetic behavior is observed. The hysteresis loops obtained at lower temperature undoubtly testify to the presence of a superconductive phase in the sample. However, the part of the superconductive phase in the Sn1Ba1Sr1Cu3O(sub x) ceramic turned out to be small, less than 2 percent, which agrees with the estimation from magnetic data. In order to increase the content of the superconductive phase, two-valent cations Ba and Sr were partially substituted by univalent (K) and three-valent ones (Y).

  5. Synthesis and superconductivity of (Agx/CuTl-1223 composites

    Directory of Open Access Journals (Sweden)

    Abdul Jabbar

    2015-06-01

    Full Text Available Series of (Agx/(Cu0.5Tl0.5Ba2Ca2Cu3O10-δ {(Agx/CuTl-1223} nano-superconductor composites were synthesized with different concentrations (i.e. x=0~4.0 wt% of silver (Ag nanoparticles. Low anisotropic CuTl-1223 superconducting matrix was prepared by solid-state reaction and Ag nanoparticles were prepared by a sol–gel method separately. The required (Agx/CuTl-1223 composition was obtained by the inclusion of Ag nanoparticles in CuTl-1223 superconducting matrix. Structural, morphological, compositional and superconducting transport properties of these composites were investigated in detail by x-ray diffraction (XRD, scanning electron microscopy (SEM, energy dispersive x-rays (EDX spectroscopy and four-point probe electrical resistivity (ρ measurements. The inclusion of Ag nanoparticles enhanced the superconducting properties without affecting the tetragonal structure of the host CuTl-1223 matrix. The improvement in superconducting properties of (Agx/CuTl-1223 composites is most likely due to enhanced inter-grains coupling and increased superconducting volume fraction after the addition of metallic Ag nanoparticles at the inter-crystallite sites in the samples. The presence of Ag nanoparticles at the grain-boundaries may increase the number of flux pinning centers, which were present in the form of weak-links in the pure CuTl-1223 superconducting matrix.

  6. High-temperature processing of oxide superconductors and superconducting oxide-silver oxide composite

    Science.gov (United States)

    Wu, M. K.; Loo, B. H.; Peters, P. N.; Huang, C. Y.

    1988-01-01

    High temperature processing was found to partially convert the green 211 phase oxide to 123 phase. High Tc superconductivity was observed in Bi-Sr-Cu-O and Y-Sr-Cu-O systems prepared using the same heat treatment process. High temperature processing presents an alternative synthetic route in the search for new high Tc superconductors. An unusual magnetic suspension with enhancement in critical current density was observed in the 123 and AgO composite.

  7. Possible mechanism of superconductivity in CuO-Cu interface

    CERN Document Server

    Amelin, I I

    2002-01-01

    The CuO two-dimensional lattice consisting of the Cu sup 2 sup + and O sup 1 sup - ions which form the narrow partially filled two-dimensional zone is apparently formed in the CuO-Cu interface on the copper oxide surface. In this case formation of local electron pairs (LEP) is possible in the plane oxygen subsystem due to the Shubin-Vonsovskii conditions. In this approximation rough evaluation of the LEP formation temperature results in the T* approx 10 sup 4 K value. The temperature of the initial Bose-Einstein condensation by the concentration in the interface layer n approx 1.6 x 10 sup 2 sup 0 cm sup - sup 3 and the carriers effective mass m* approx m sub e may have the value of T sub c approx 1000 K. The obtained evaluation of the T sub c temperature corresponds by the values order to the experimental value

  8. Superconducting spin-valve effect and triplet superconductivity in Co Ox/Fe1/Cu /Fe2/Cu /Pb multilayer

    Science.gov (United States)

    Leksin, P. V.; Garif'yanov, N. N.; Kamashev, A. A.; Fominov, Ya. V.; Schumann, J.; Hess, C.; Kataev, V.; Büchner, B.; Garifullin, I. A.

    2015-06-01

    We report magnetic and superconducting properties of the modified spin-valve system CoOx/Fe1/Cu /Fe2/Cu /Pb . Introduction of a Cu interlayer between Fe2 and Pb layers prevents material interdiffusion process, increases the Fe2/Pb interface transparency, stabilizes and enhances properties of the system. This allowed us to perform a comprehensive study of such heterostructures and to present theoretical description of the superconducting spin-valve effect and of the manifestation of the long-range triplet component of the superconducting condensate.

  9. Magnetic Exchange Between Superconducting and Ferromagnetic Oxide Layers

    Science.gov (United States)

    Giblin, Sean; Taylor, Jon; Duffy, Jon; Dugdale, Stephen; Nakamura, T.; Santamaria, Jacobo

    2012-02-01

    The origins of high temperature superconductivity and the rich phase diagrams in complex oxides are still a matter of contention that have stimulated many novel experimental studies and observations. Recently the improvement of layer by layer growth techniques of thin films has enabled investigations of both bulk and surface properties. For most common superconductors the order parameter is thought to be antagonistic to that of the exchange mechanism in ferromagnets. Accurately grown thin fllms have enabled these competing interactions to be probed experimentally. In particular, the growth of epitaxial oxide layers, with well-characterized atomically flat interfaces, consisting of superconducting layers of YBa2Cu3O7 (YBCO) and lattice-matched ferromagnetic La2/3Ca1/3MnO3 (LCMO) has flourished. Using XMCD we demonstrate that the known superexchange between Mn and Cu across the YBCO/LCMO is modified when an apparent critical thickness of the superconducting layer is reduced. All samples show an apparent exchange below the superconducting transition but above it is dependent on the YBCO thickness. Possible origins of this behaviour will be discussed.

  10. Empirical Criteria of Superconductivity for Some Oxides

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The properties of superconductivity of some oxides were investigated by structural parametricdiagrams or pattern recognition with structural chemical parameters. The essential criteria ofsuperconductivity for some oxides have been obtained by using 109 oxides as the training setand seven parameters as features; the results illustrated that the electronegativity difference isthe most important factor among seven parameters. Moreover, the regularity of superconductivetransition temperature Tc for complex oxides is discussed by partial least squares (PL5) method.

  11. Percolated Superconductivity and Electron-Electron Exchange Mechanism in Ba-La-Cu-O

    Science.gov (United States)

    Tao, Ruibao

    It is found that the oxygen vacancies at the Cu-O basal plane of oxide (La1-xBax)2CuO4-y (Balacuo) will break the bonds of Cu-O-Cu to make the hopping between those coppers disappear so that the electrical conduction in the Cu-O basal plane would become a bond percolation system consisting of an infinite cluster carrying the current with a great number of finite clusters hanging around. It is favorable to create some mechanism of electron-electron exchange so that the transition temperature Tc of superconductivity could be increased significantly. The comparison with Y1Ba2Cu3O9-y is also discussed briefly.

  12. Microscopic annealing process and its impact on superconductivity in T'-structure electron-doped copper oxides.

    Science.gov (United States)

    Kang, Hye Jung; Dai, Pengcheng; Campbell, Branton J; Chupas, Peter J; Rosenkranz, Stephan; Lee, Peter L; Huang, Qingzhen; Li, Shiliang; Komiya, Seiki; Ando, Yoichi

    2007-03-01

    High-transition-temperature superconductivity arises in copper oxides when holes or electrons are doped into the CuO(2) planes of their insulating parent compounds. Whereas hole doping quickly induces metallic behaviour and superconductivity in many cuprates, electron doping alone is insufficient in materials such as R(2)CuO(4) (R is Nd, Pr, La, Ce and so on), where it is necessary to anneal an as-grown sample in a low-oxygen environment to remove a tiny amount of oxygen in order to induce superconductivity. Here we show that the microscopic process of oxygen reduction repairs Cu deficiencies in the as-grown materials and creates oxygen vacancies in the stoichiometric CuO(2) planes, effectively reducing disorder and providing itinerant carriers for superconductivity. The resolution of this long-standing materials issue suggests that the fundamental mechanism for superconductivity is the same for electron- and hole-doped copper oxides.

  13. Effect of the laser sputtering parameters on the orientation of a cerium oxide buffer layer on sapphire and the properties of a YBa2Cu3Ox superconducting film

    DEFF Research Database (Denmark)

    Mozhaev, P. B.; Ovsyannikov, G. A.; Skov, Johannes

    1999-01-01

    The effect of the laser sputtering parameters on the crystal properties of CeO2 buffer layers grown on a (1 (1) under bar 02) sapphire substrate and on the properties of superconducting YBa2Cu3Ox thin films are investigated. It is shown that (100) and (111) CeO2 growth is observed, depending...

  14. Study of some superconducting and magnetic materials on high T sub c oxide superconductors

    Science.gov (United States)

    Wu, M. K.

    1987-01-01

    On the basis of existing data it appears that the high-temperature superconductivity above 77 K reported here, occurs only in compound systems consisting of a phase other than the K2NiF4 phase. A narrow superconducting transition was obtained with T sub c0 = 98 K and T sub c1 = 94 K in Y-Ba-Cu-O (YBCO). Preliminary results indicate that YBCO is rather different from the layered LaBCO, LaSCO, and LaCCO. While electron-photon interaction cannot be absent from this compound system, nonconventional enhanced superconducting interactions due to interfaces, Resonating Valence Bond (RVB) states, or even a superconducting state beyond the BCS framework, may be required to account for the high T sub c in YBCO. It is believed that study of the possible subtle correlation between magnetism and superconductivity will definitely provide important insight into the superconducting mechanism in YBCO and other oxides.

  15. Synthesis, characterization, phase diagrams and superconducting and normal state magnetic properties of La{sub 2{minus}x}Sr{sub x}CuO{sub 4} (0 {le} x {le} 0.08) and electrochemically oxidized La{sub 2{minus}x}Sr{sub x}CuO{sub 4+{delta}} (0 {le} x {le} 0.33, 0 {le} {delta} {le} 0.12)

    Energy Technology Data Exchange (ETDEWEB)

    Chou, F.

    1993-08-01

    La{sub 2{minus}x}Sr{sub x}CuO{sub 4} (0 {le} x {le} 0.15) can all be intercalated with oxygen by a novel electrochemical oxidation method. Bulk superconductivity is found with an onset {Tc} {approx} 40 K for the whole range 0.01 {le} x {le} 0.15; for x = 0.25 and 0.33, the electrochemical oxidation did not improve the superconducting properties. The magnetic susceptibility {chi}(T = 50--320 K) data for La{sub 2}CuO{sub 4.11} and La{sub 1.92}Sr{sub 0.08}CuO{sub 4.07} are nearly identical with those of conventionally prepared La{sub 1.85}Sr{sub 0.15}CuO{sub 4}, indicating that the hole doping level (p) in the CuO{sub 2} planes of the three compounds is nearly the same. Combined thermogravimetric analysis and iodometric titration experiments indicate that part of the intercalated oxygen has a formal valence close to {minus}1. The maximum doped-hole concentration in the CuO{sub 2} planes that can be achieved from combined Sr-doping and electrochemical oxygen doping for 0 {le} x {le} 0.15 is p {approx} 0.16 holes/formula unit. Oxygen can also intercalate into single crystal La{sub 2}CuO{sub 4} through a slow electrochemical oxidation process. The required low current and long time for the charging process reflects that the oxygen intercalation for a single crystal is limited by its small specific surface area and long diffusion distance. The anisotropic superconducting, magnetic and transport properties are summarized and compared with those of polycrystalline La{sub 2}CuO{sub 4+{delta}} as well as of YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} and La{sub 2{minus}x}Sr{sub x}CuO{sub 4} single crystals. The single crystal La{sub 2}CuO{sub 4+{delta}} has a maximum {Tc} {approx} 40 K, which is lower than that ({Tc} {approx} 42--45) of the corresponding polycrystalline samples. The magnetic phase diagram of La{sub 2{minus}x}Sr{sub x}CuO{sub 4} in the antiferromagnetic (AF) regime (0 {le} x {le} 0.02) has been derived from {sup 139}La NQR studies from 4 to 250 K.

  16. Mo{sub x}Cu{sub 1-x}Sr{sub 2}YCu{sub 2}O{sub y} (0.3{<=}x{<=}1) revisited: Superconductivity, magnetism and the molybdenum oxidation state

    Energy Technology Data Exchange (ETDEWEB)

    Marik, Sourav [Dpto. Quimica Inorganica, Facultad de CC.Quimicas, U. Complutense de Madrid, 28040-Madrid (Spain); CNRS, Universite de Bordeaux, ICMCB, 87 avenue du Dr. A. Schweitzer, Pessac, F-33608 (France); Moran, Emilio, E-mail: emoran@quim.ucm.es [Dpto. Quimica Inorganica, Facultad de CC.Quimicas, U. Complutense de Madrid, 28040-Madrid (Spain); Labrugere, Christine; Toulemonde, Olivier [CNRS, Universite de Bordeaux, ICMCB, 87 avenue du Dr. A. Schweitzer, Pessac, F-33608 (France); Alario-Franco, Miguel Angel [Dpto. Quimica Inorganica, Facultad de CC.Quimicas, U. Complutense de Madrid, 28040-Madrid (Spain)

    2012-07-15

    A systematic study is reported on the range of stability of molybdenum substituted Sr-based 123 compounds with Mo-Sr-Y-Cu system, synthesized under ambient pressure. All materials crystallize in the space group: P4/mmm and the observed solubility limit of Mo is rather low in this structure because secondary phases start to form as soon as x>0.3 in nominal composition is reached. The antiferromagnetic property in all superconducting multiphase samples can be attributed to the secondary phase Y{sub 2}Cu{sub 2}O{sub 5}. The influence of oxygen annealing on the changes in electronic structure for the pure Mo{sub 0.3}Cu{sub 0.7}Sr{sub 2}YCu{sub 2}O{sub y} system associated with a non-superconductor to superconductor transition has been investigated by means of X-ray photoelectron spectroscopy, powder X-ray diffraction, magnetic susceptibility and specific-heat measurements. We unambiguously show the predominance of the Mo{sup 5+} state over the Mo{sup 6+} one on both as-synthesized and annealed phases; annealing under an oxygen atmosphere enhances both the Mo{sup 6+} and Cu{sup 2+} amounts. We suggest that the enhancement of Mo{sup 6+} under oxygen annealing is in close relation with the decrease in the O 2p{yields}Cu 3d charge-transfer energy resulting in superconducting properties. - Graphical abstract: A study on the ambient-pressure synthesis and the range of stability of complex perovskites in the system Y-Sr-Cu-Mo shows that the solubility limit of Mo is rather low in this structure ({approx}30%). Secondary phases (detected by XRD) start to form for x>0.3 in nominal composition. All materials crystallize in the space group: P4/mmm. Antiferromagnetism in all superconducting multiphase samples is attributed to the secondary phase Y{sub 2}Cu{sub 2}O{sub 5}. Pure Mo{sub 0.3}Cu{sub 0.7}Sr{sub 2}YCu{sub 2}O{sub y} studied by means of powder X-ray diffraction, magnetic susceptibility and specific-heat measurements. Changes in electronic structure for the pure Mo{sub 0

  17. Synthesis and superconductivity of (Ag)x/CuTl-1223 composites

    Institute of Scientific and Technical Information of China (English)

    Abdul Jabbar; Irfan Qasim; M Mumtaz; K Nadeem

    2015-01-01

    Series of (Ag)x/(Cu0.5Tl0.5Ba2Ca2Cu3O10-δ) {(Ag)x/CuTl-1223} nano-superconductor composites were synthesized with different concentra-tions (i.e. x ¼ 0 ? 4.0 wt%) of silver (Ag) nanoparticles. Low anisotropic CuTl-1223 superconducting matrix was prepared by solid-state reaction and Ag nanoparticles were prepared by a sol–gel method separately. The required (Ag)x/CuTl-1223 composition was obtained by the inclusion of Ag nanoparticles in CuTl-1223 superconducting matrix. Structural, morphological, compositional and superconducting transport properties of these composites were investigated in detail by x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive x-rays (EDX) spectroscopy and four-point probe electrical resistivity (ρ) measurements. The inclusion of Ag nanoparticles enhanced the superconducting properties without affecting the tetragonal structure of the host CuTl-1223 matrix. The improvement in superconducting properties of (Ag)x/CuTl-1223 composites is most likely due to enhanced inter-grains coupling and increased superconducting volume fraction after the addition of metallic Ag nanoparticles at the inter-crystallite sites in the samples. The presence of Ag nanoparticles at the grain-boundaries may increase the number of flux pinning centers, which were present in the form of weak-links in the pure CuTl-1223 superconducting matrix.

  18. Emergence of superconductivity from the dynamically heterogeneous insulating state in La(2-x)Sr(x)CuO4.

    Science.gov (United States)

    Shi, Xiaoyan; Logvenov, G; Bollinger, A T; Božović, I; Panagopoulos, C; Popović, Dragana

    2013-01-01

    A central issue for copper oxides is the nature of the insulating ground state at low carrier densities and the emergence of high-temperature superconductivity from that state with doping. Even though this superconductor-insulator transition (SIT) is a zero-temperature transition, measurements are not usually carried out at low temperatures. Here we use magnetoresistance to probe both the insulating state at very low temperatures and the presence of superconducting fluctuations in La(2-x)Sr(x)CuO(4) films, for doping levels that range from the insulator to the superconductor (x  =  0.03-0.08). We observe that the charge glass behaviour, characteristic of the insulating state, is suppressed with doping, but it coexists with superconducting fluctuations that emerge already on the insulating side of the SIT. The unexpected quenching of the superconducting fluctuations by the competing charge order at low temperatures provides a new perspective on the mechanism for the SIT.

  19. The Oxidation of Sn-Ag coated Superconducting Cables for the Large Hadron Collider (LHC)

    CERN Document Server

    Scheuerlein, C; Cantoni, M

    2006-01-01

    The oxides formed on the Sn-Ag coated LHC superconducting cables during a 200°C heat treatment in air are described and the oxide composition is compared with the interstrand contact resistance (Rc). The analysis of more than 250 interstrand contact areas shows that the higher the average Cu content with respect to the Sn content in the oxide, the higher is Rc. During the 200°C heat treatment, Sn in the coating is transformed into a Cu3Sn layer, on which an oxide grows that consists essentially of a thin outermost layer of CuO on top of Cu2O, similar to the oxide structure formed on bare Cu. The underlying Cu3Sn layer acts as an O diffusion barrier that prevents O diffusion into the Cu bulk during the subsequent cable heat treatment under high pressure. On contact zones where the Cu3Sn layer is not formed during the 200°C heat treatment mainly Sn oxide grows and Rc is comparatively low.

  20. Structure and superconductivity in (Bi(0.35)Cu(0.65))Sr2YCu2O7 and related materials

    Science.gov (United States)

    Jennings, R. A.; Williams, S. P.; Greaves, C.

    1995-01-01

    The recently reported (Bi/Cu)Sr2YCu2O7 phase has been studied by time of flight powder neutron diffraction. The proposed 1212 structure has been confirmed and refinements have shown the oxygen in the (Bi/Cu)O layer is displaced by 0.78 A from the ideal (1/2,1/2,0) site (P4/mmm space group) along /100/. Bond Valence Sum calculations have suggested oxidation states of Bi(5+) and Cu(2+) for the cations in the (Bi/Cu)O layers. The material is non-superconducting and all attempts to induce superconductivity have been unsuccessful. Work on the related material (Ce/Cu)Sr2YCu2O7 has shown the ideal Ce content to be 0.5 Ce per formula unit. The introduction of Ba (10%) onto the Sr site dramatically increases phase stability and also induces superconductivity (62 K).

  1. Cu-Ti Formation in Nb-Ti/Cu Superconducting Strand Monitored by in situ Techniques

    CERN Document Server

    Pong, I; Pong, Ian; Gerardin, Alexandre; Scheuerlein, Christian; Bottura, Luca

    2010-01-01

    In order to investigate the high temperature exposure effect on Nb-Ti/Cu superconducting strands, as might be encountered in joining by soldering and in cabling annealing, X-ray diffraction and resistometry measurements were performed in situ during heat treatment, and complemented by conventional metallography, mechanical tests and superconducting properties measurements. Changes of the Nb-Ti nanostructure at temperatures above 300 degrees C are manifested in the degradation of critical current in an applied external magnetic field, although degradation at self field was insignificant up to 400 degrees C for several minutes. Above 500 degrees C, the formation of various Cu-Ti intermetallic compounds, due to Ti diffusion from Nb-Ti into Cu, is detected by in situ XRD albeit not resolvable by SEM-EDS. There is a ductile to brittle transition near 600 degrees C, and liquid formation is observed below 900 degrees C. The formation of Cu-Ti causes a delayed reduction of the residual resistivity ratio (RRR) and adv...

  2. Coulomb-oscillator origin of superconductivity in p-doped copper oxides

    CERN Document Server

    Bucher, Manfred

    2013-01-01

    Emergence, development and cessation of superconductivity in three representative compounds of copper oxide families---cation doped Ca_2-xNa_xCuO2Cl2 and La_2-xAe_xCuO4 (Ae = Ba, Sr), as well as oxygen enriched YBa2Cu3O_6+x ---are explained with the Coulomb-oscillator model of superconductivity. By the model, non-resistive current is carried by axial Coulomb oscillations of s electrons through neighbor nuclei---here excited 3s electrons from O^2- ions through next-nearest neighbor oxygen nuclei---if their accompanying lateral oscillation is sufficiently confined to prevent lateral overswing. Cation doping gives rise to a superlattice in the layers that sandwich each CuO2 plane. In Ca_2-xNa_xCuO2Cl2, having one CuO2 plane per unit cell, superconductivity emerges when laterally confined Coulomb oscillators start connecting along 6 x 6 superlattice domains (in units of planar lattice constants) and it peaks at 4 x 4 domains when, at doping x = 1/8, the superlattice is completed. With further doping a new, off-se...

  3. Electric currents in REBaCuO superconducting tapes

    Science.gov (United States)

    Jirsa, M.; Rameš, M.; Ďuran, I.; Melíšek, T.; Kováč, P.; Viererbl, L.

    2017-04-01

    Magnetic induction and current transport techniques were employed to test the electromagnetic performance of 22 samples of superconducting REBaCuO tapes of several manufacturers with the aim to select the best candidates for wiring new generation superconducting magnets for fusion reactors. An extraordinary shape of pinning force density as a function of magnetic field was observed in ‘advanced pinning, AP’ SuperPower tapes. The induced currents enabled us to classify the tapes and show the best ones, at low temperatures and high magnetic fields on the one hand and at high temperatures and low magnetic fields on the other hand. Transport current experiments confirmed the results. Moreover, they provided information on current anisotropy, which appeared to be specific for each tape type. The present results formed a basis for the ongoing study of neutron irradiation impact on the tapes’ properties. The first experiment showed that neutron irradiation by the fluence of 2.1 E22 m‑2 either enhances, reduces, or has no effect on the tape’s properties, according to the tape pinning structure.

  4. Prediction of Superconductivity for Oxides Based on Structural Parameters and Artificial Neural Network Method

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Superconductive properties for oxides were predicted by artificial neural network (ANN) method with structural and chemical parameters as inputs. The predicted properties include superconductivity for oxides, distributed ranges of the superconductive transition temperature (Tc) for complex oxides, and Tc values for cuprate superconductors. The calculated results indicated that the adjusted ANN can be used to predict superconductive properties for unknown oxides.

  5. Microwave observation of magnetic field penetration of high-T/sub c/ superconducting oxides

    Energy Technology Data Exchange (ETDEWEB)

    Khachaturyan, K.; Weber, E.R.; Tejedor, P.; Stacy, A.M.; Portis, A.M.

    1987-12-01

    Microwave methods, using a conventional EPR spectrometer, have been applied to a study of magnetic field penetration of the high-T/sub c/ superconducting oxides La/sub 1.85/Sr/sub 0.15/CuO/sub 4/, YBa/sub 2/Cu/sub 3/O/sub 7/, and EuBa/sub 2/Cu/sub 3/O/sub 7/. Signals over 10/sup 5/ times the sensitivity limit of the EPR spectrometer were obtained. Huge low-field peaks were observed in the superconducting phase for magnetic fields below 10 G. The peak signal decreased exponentially with temperature just below T/sub c/. These observations are taken as evidence of the spin-glass features of these materials and of fluxoid penetration of intrinsic Josephson junctions.

  6. Influence of Cu-site substitution on La2Ca1Ba2Cu5Oz superconducting system

    Science.gov (United States)

    Bhalodia, J. A.; Mankadia, S. R.; Dalsaniya, S. M.; Gonal, M. R.

    2012-07-01

    We have prepared a series of La2CaBa2Cu5-xCoxOz; x = 0.0, 0.1, 0.2, 0.5, 1.0, 2.0, 5.0 (La-2125) compounds by the standard solid state reaction method and characterized for their structural, superconducting, magnetic properties and oxygen content through X-ray diffraction, scanning electron microscopy, d. c. resistivity, magnetic susceptibility and iodometric titration respectively. All the compounds crystallize with the tetragonal LaBa2Cu3Oz type structure, space group P4/mmm. Here the effect of higher Co substitution for Cu in the La2CaBa2Cu5-xCoxOz system has been studied. It is observed that only 2 at. % Co substitution for Cu destroys the superconductivity of the sample. For heavily doped samples (with x >= 0.1) are found non-superconducting presumably because of magnetic pair- breaking effect. These samples do not show superconductivity but are of interest for understanding the interplay between superconductivity and magnetism. Possible reasons for destruction of superconductivity are discussed in this communication.

  7. Synthesis, characterization, phase diagrams and superconducting and normal state magnetic properties of La2-xSrxCuO4 (0 ≤ x ≤ 0.08) and electrochemically oxidized La2-xSrxCuO4+δ (0 ≤ x ≤ 0.33, 0 ≤ δ ≤ 0.12)

    Energy Technology Data Exchange (ETDEWEB)

    Chou, Fangcheng [Iowa State Univ., Ames, IA (United States)

    1993-08-01

    La2-xSrxCuO4 (0 ≤ x ≤ 0.15) can all be intercalated with oxygen by a novel electrochemical oxidation method. Bulk superconductivity is found with an onset Tc~ 40 K for the whole range 0.01 ≤ x ≤ 0.15; for x = 0.25 and 0.33, the electrochemical oxidation did not improve the superconducting properties. The magnetic susceptibility χ(T = 50--320 K) data for La2CuO4.11 and La1.92Sr0.08CuO4.07 are nearly identical with those of conventionally prepared La1.85Sr0.15CuO4, indicating that the hole doping level (p) in the CuO2 planes of the three compounds is nearly the same. Combined thermogravimetric analysis and iodometric titration experiments indicate that part of the intercalated oxygen has a formal valence close to -1. The maximum doped-hole concentration in the CuO2 planes that can be achieved from combined Sr-doping and electrochemical oxygen doping for 0 ≤ x ≤ 0.15 is p ~ 0.16 holes/formula unit. Oxygen can also intercalate into single crystal La2CuO4 through a slow electrochemical oxidation process. The required low current and long time for the charging process reflects that the oxygen intercalation for a single crystal is limited by its small specific surface area and long diffusion distance. The anisotropic superconducting, magnetic and transport properties are summarized and compared with those of polycrystalline La2CuO4+δ as well as of YBa2Cu3O7-δ and La2-xSrxCuO4 single crystals. The single crystal La2CuO4+δ has a maximum Tc ~ 40 K, which is lower than that (Tc ~ 42--45) of the corresponding polycrystalline samples. The magnetic phase diagram of La2-xSrxCuO4 in the antiferromagnetic (AF) regime (0 ≤ x ≤ 0

  8. High-pressure study of the new Y-Ba-Cu-O superconducting compound system

    Science.gov (United States)

    Hor, P. H.; Gao, L.; Meng, R. L.; Huang, Z. J.; Wang, Y. Q.

    1987-01-01

    Hydrostatic effects on the superconducting transition temperature of the Y-Ba-Cu-O compound system, resistively, up to 19 kbar are investigated. It is found that pressure has little effect on the superconducting state of Y-Ba-Cu-O, in marked contrast to the behavior of the K2NiF4-phase La-Ba-Cu-O and La-Sr-Cu-O systems. It is suggested that this effect may be due to chemical pressure associated with the smaller Y atoms already present in Y-Ba-Cu-O. X-ray powder-diffraction studies show that the high-temperature superconductivity in Y-Ba-Cu-O can only be attributed to one or more phases with structures different from the cubic perovskite or tetragonal layered ones.

  9. Fabrication of YBa2Cu3O7-δ superconducting nanofibres by electrospinning

    Science.gov (United States)

    Cui, Xue Mei; Lyoo, Won Seok; Son, Won Keun; Park, Dae Hun; Choy, Jin Ho; Lee, Taek Seung; Park, Won Ho

    2006-12-01

    YBa2Cu3O7-δ superconducting nanofibres were successfully fabricated via the electrospinning method in combination with the sol-gel process. The solution was prepared by the sol-gel process with a homogeneous aqueous PVA solution containing Y, Ba, and Cu acetates. The viscosity of the precursor sol for electrospinning was controlled by the evaporation of solvent and a condensation reaction. The electrospun nanofibres were pyrolysed to remove PVA or volatile components, and then sintered to generate a superconducting phase. The critical transition temperature (Tc) of superconducting YBa2Cu3O7-δ nanofibres was measured by DC susceptibility tests. By optimizing the electrospinning process and following heat treatments, superconducting YBa2Cu3O7-δ nanofibres with a Tc = 92.2 K could be produced.

  10. Properties of superconducting Bi-Sr-Ca-Cu-O system remelted under higher gravity conditions

    Science.gov (United States)

    Volkov, M. P.; Melekh, B. T.; Parfeniev, R. V.; Kartenko, N. F.; Regel, L. L.; Turchaninov, A. M.

    1992-04-01

    The structure and magnetic properties of high Tc superconductor Bi-Sr-Ca-Cu-O samples remelted under 1 g0, 8 g0 and 12 g0 gravity levels have been investigated. Superconducting properties make a change along the ingots. The dependence of structural and superconducting properties on the gravity level and their time degradation have been observed.

  11. Proximity-induced superconductivity in monolayer CuO2 on cuprate substrates

    Science.gov (United States)

    Zhu, Guo-Yi; Zhang, Fu-Chun; Zhang, Guang-Ming

    2016-11-01

    To understand the recently observed high temperature superconductivity in the monolayer CuO2 grown on the Bi2Sr2CaCu2O8 + δ substrates, we propose a two-band model of the hybridized oxygen px and py orbitals with the proximity effect of the substrate. We demonstrate that both the nodal and nodeless superconducting states can be induced by the proximity effect, depending on the strengths of the pairing parameters.

  12. Submicrometer Superconducting YBa2Cu3O6+x Particles Made by a Low-Temperature Synthetic Route.

    Science.gov (United States)

    Horowitz, H S; McLain, S J; Sleight, A W; Druliner, J D; Gai, P L; Vankavelaar, M J; Wagner, J L; Biggs, B D; Poon, S J

    1989-01-06

    Evidence suggests that superconducting, orthorhombic YBa(2)Cu(3)O(6+x)+ (x greater, similar 0.5) is always produced by oxidation of the oxygen-deficient, tetragonal form (x less, similar 0.5) of this phase (commonly referred to as 123). A synthetic route whereby solution-derived, carbon-free precursors are decomposed at 650 degrees to 700 degrees C in inert atmosphere to yield tetragonal 123 is now available. Appropriate precursors include hydrated oxides derived from the hydrolysis of organometallic solutions and aqueous solution-derived hyponitrites. Subsequent oxidation of the tetragonal phase at 400 degrees C results in submicrometer particles of orthorhombic 123. Superconductivity (T(c) onset approximately 87 K) has been confirmed in these materials by both Meissner effect and specific-heat measurements.

  13. Nonlinear lattice dynamics as a basis for enhanced superconductivity in YBa2Cu3O6.5.

    Science.gov (United States)

    Mankowsky, R; Subedi, A; Först, M; Mariager, S O; Chollet, M; Lemke, H T; Robinson, J S; Glownia, J M; Minitti, M P; Frano, A; Fechner, M; Spaldin, N A; Loew, T; Keimer, B; Georges, A; Cavalleri, A

    2014-12-04

    Terahertz-frequency optical pulses can resonantly drive selected vibrational modes in solids and deform their crystal structures. In complex oxides, this method has been used to melt electronic order, drive insulator-to-metal transitions and induce superconductivity. Strikingly, coherent interlayer transport strongly reminiscent of superconductivity can be transiently induced up to room temperature (300 kelvin) in YBa2Cu3O6+x (refs 9, 10). Here we report the crystal structure of this exotic non-equilibrium state, determined by femtosecond X-ray diffraction and ab initio density functional theory calculations. We find that nonlinear lattice excitation in normal-state YBa2Cu3O6+x at above the transition temperature of 52 kelvin causes a simultaneous increase and decrease in the Cu-O2 intra-bilayer and, respectively, inter-bilayer distances, accompanied by anisotropic changes in the in-plane O-Cu-O bond buckling. Density functional theory calculations indicate that these motions cause drastic changes in the electronic structure. Among these, the enhancement in the character of the in-plane electronic structure is likely to favour superconductivity.

  14. High-temperature interface superconductivity between metallic and insulating copper oxides.

    Science.gov (United States)

    Gozar, A; Logvenov, G; Kourkoutis, L Fitting; Bollinger, A T; Giannuzzi, L A; Muller, D A; Bozovic, I

    2008-10-09

    The realization of high-transition-temperature (high-T(c)) superconductivity confined to nanometre-sized interfaces has been a long-standing goal because of potential applications and the opportunity to study quantum phenomena in reduced dimensions. This has been, however, a challenging target: in conventional metals, the high electron density restricts interface effects (such as carrier depletion or accumulation) to a region much narrower than the coherence length, which is the scale necessary for superconductivity to occur. By contrast, in copper oxides the carrier density is low whereas T(c) is high and the coherence length very short, which provides an opportunity-but at a price: the interface must be atomically perfect. Here we report superconductivity in bilayers consisting of an insulator (La(2)CuO(4)) and a metal (La(1.55)Sr(0.45)CuO(4)), neither of which is superconducting in isolation. In these bilayers, T(c) is either approximately 15 K or approximately 30 K, depending on the layering sequence. This highly robust phenomenon is confined within 2-3 nm of the interface. If such a bilayer is exposed to ozone, T(c) exceeds 50 K, and this enhanced superconductivity is also shown to originate from an interface layer about 1-2 unit cells thick. Enhancement of T(c) in bilayer systems was observed previously but the essential role of the interface was not recognized at the time.

  15. Elemental composition analysis of superconducting Hg0.67Pb0.34Ba2Ca2Cu3O8+δ

    Institute of Scientific and Technical Information of China (English)

    毛福明; 邵力为

    1997-01-01

    The analysis of superconducting sample by using a sputtered neutral particle mass spectrometer demonstrates that Ca and Ba elements are oxidative, Cu is non-oxidative, Hg is mainly in metallic form near the surface and becomes oxidative far from the surface, and Pb is concentrated on the surface. The analysis also reveals that the highly concentrative hydrocarbon and water impurities are mixed into the sample during the preparation and conservation.

  16. Superconducting YBa2Cu3O7– thick film (c (0)$ = 92 K) on a newly developed perovskite ceramic substrate

    Indian Academy of Sciences (India)

    S U K Nair; P R S Warriar; J Koshy

    2002-04-01

    A complex perovskite oxide, YbBa2NbO6, as a non-reacting substrate for YBa2Cu3O7– superconducting film has been developed. The dielectric constant and loss factor values of the material are in the range suitable for its use as substrate for microwave application. A YBa2Cu3O7– superconducting thick film dip coated on YbBa2NbO6 substrate gave a c (0) of 92 K and current density of ∼ 1.3 × 104 A cm-2.

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

    Science.gov (United States)

    Raveau, Bernard

    2016-11-25

    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.

  18. Free-standing oxide superconducting articles

    Science.gov (United States)

    Wu, Xin D.; Muenchausen, Ross E.

    1993-01-01

    A substrate-free, free-standing epitaxially oriented superconductive film including a layer of a template material and a layer of a ceramic superconducting material is provided together with a method of making such a substrate-free ceramic superconductive film by coating an etchable material with a template layer, coating the template layer with a layer of a ceramic superconductive material, coating the layer of ceramic superconductive material with a protective material, removing the etchable material by an appropriate means so that the etchable material is separated from a composite structure including the template lay This invention is the result of a contract with the Department of Energy (Contract No. W-7405-ENG-36).

  19. NiCu-based superconducting devices: fabrication and characterization

    Energy Technology Data Exchange (ETDEWEB)

    Ruotolo, A [Universita di Napoli Federico II, Dip. Scienze Fisiche, Facolta d' Ingegneria, P.le Tecchio 80, 80125 Naples (Italy); Pullini, D [Centro Ricerche FIAT, Strada Torino 50, 10043 Orbassano, Turin (Italy); Adamo, C [Universita di Salerno, Dip. Scienze Fisiche, Via S. Allende 1, 84081 Baronissi, Salerno (Italy); Pepe, G P [Universita di Napoli Federico II, Dip. Scienze Fisiche, Facolta d' Ingegneria, P.le Tecchio 80, 80125 Naples (Italy); Maritato, L [Universita di Salerno, Dip. Scienze Fisiche, Via S. Allende 1, 84081 Baronissi, Salerno (Italy); Innocenti, G [Centro Ricerche FIAT, Strada Torino 50, 10043 Orbassano, Turin (Italy); Perlo, P [Centro Ricerche FIAT, Strada Torino 50, 10043 Orbassano, Turin (Italy)

    2006-06-01

    The critical Josephson current (I{sub C}) in superconducting/ferromagnetic (S/F) multilayer-based junctions can be controlled by changing the relative directions of the magnetization in the F-layers. Recent experimental works show that an enhancement of I{sub C} is achieved in S/F weak links when the alternating F-layers are antiparallel aligned. We present preliminary experimental results concerning the dependence of I{sub C} on the relative orientation of the ferromagnetic layers in S/F{sub 1}/I/F{sub 2}/S tunnel junctions where the F-layers are obtained by changing the relative composition of NiCu alloys. The multilayers were grown by electron beam deposition, and processed by Focused Ion Beam lithography. The magnetic state of the devices was directly determined by measuring the current perpendicular to plane (CPP) magnetoresistance (MR) at high bias. I{sub C} was found to be larger when the F-layers are antiparallel aligned. The maximum change of I{sub C} corresponds to the maximum change of MR. The application of a magnetic field induces a transition in the shape of the currentvoltage curve that seems to suggest Coulomb blockade effect.

  20. NiCu-based superconducting devices: fabrication and characterization

    Science.gov (United States)

    Ruotolo, A.; Pullini, D.; Adamo, C.; Pepe, G. P.; Maritato, L.; Innocenti, G.; Perlo, P.

    2006-06-01

    The critical Josephson current (IC) in superconducting/ferromagnetic (S/F) multilayer-based junctions can be controlled by changing the relative directions of the magnetization in the F-layers. Recent experimental works [1, 2] show that an enhancement of IC is achieved in S/F weak links when the alternating F-layers are antiparallel aligned. We present preliminary experimental results concerning the dependence of IC on the relative orientation of the ferromagnetic layers in S/F1/I/F2/S tunnel junctions where the F-layers are obtained by changing the relative composition of NiCu alloys. The multilayers were grown by electron beam deposition, and processed by Focused Ion Beam lithography. The magnetic state of the devices was directly determined by measuring the current perpendicular to plane (CPP) magnetoresistance (MR) at high bias. IC was found to be larger when the F-layers are antiparallel aligned. The maximum change of IC corresponds to the maximum change of MR. The application of a magnetic field induces a transition in the shape of the currentvoltage curve that seems to suggest Coulomb blockade effect.

  1. Relation between oxygen content and superconductivity in Bi-Sr-Ca-Cu-O system

    Energy Technology Data Exchange (ETDEWEB)

    Miura, N.; Deshimaru, Y.; Otani, T.; Shimizu, Y.; Yamazoe, N. (Dept. of Materials Science and Tech., Graduate School of Engineering Sciences, Kyushu Univ., Fukuoka (Japan))

    1991-12-01

    Oxygen sorption-desorption behaviors as well as superconducting properties were examined for a series of 2212-isostructural oxides, Bi{sub 2}Sr{sub 2-x}Ca{sub 1+x}Cu{sub 2}O{sub y} (x=0-1.0). It was found that oxygen sorption and desorption at temperatures below 600deg C brought about reversible shifts of Tc in a manner dependent on x. Quantitative determination of oxygen content (y) revealed that, as y decreased with oxygen desorption from the as-prepared levels, Tc increased montonically for x=0 and 0.25, while it went through a maximum at y=8.15 for x=0.8. (orig.).

  2. Study on the electronic structures of REBaCuO superconductors and their relation to superconductivity

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Electronic structures of REBaCuO(RE=La, Pr, Nd, Sm, Gd, Dy, Ho and Er)systems were calculated by means of SCF-Xα -SW methods. Results show that there is an inner-orbit coupling for these oxide superconductor systems. The inner-orbit coupling was resulted from the interaction of two electronic orbits of RE 5p and O 2s, since they have similar energy state levels and relatively larger orbital electronic clouds. Compared with experimental facts, it is also found that the overlap in space between the two orbits has a similar tendency to Tc and the number of enrolling electrons has a close relation to Jc, therefore, the influence of inner-orbit coupling on superconductivity could not be overlooked.

  3. Emergent vortices at a ferromagnetic superconducting oxide interface

    Science.gov (United States)

    Petrović, A. P.; Paré, A.; Paudel, T. R.; Lee, K.; Holmes, S.; Barnes, C. H. W.; David, A.; Wu, T.; Tsymbal, E. Y.; Panagopoulos, C.

    2014-10-01

    Understanding the cohabitation arrangements of ferromagnetism and superconductivity at the LaAlO3/SrTiO3 interface remains an open challenge. Probing this coexistence with sub-Kelvin magnetotransport experiments, we demonstrate that a hysteretic in-plane magnetoresistance develops below the superconducting transition for ≤ft| {{H}//} \\right| \\lt 0.15 T, independently of the carrier density or oxygen annealing. This hysteresis is argued to arise from vortex depinning within a thin (\\lt 20 nm) superconducting layer, mediated by discrete ferromagnetic dipoles located solely above the layer. The pinning strength may be modified by varying the superconducting channel thickness via electric field-effect doping. No evidence is found for bulk magnetism or finite-momentum pairing, and we conclude that ferromagnetism is strictly confined to the interface, where it competes with superconductivity. Our work indicates that oxide interfaces are ideal candidate materials for the growth and analysis of nanoscale superconductor/ferromagnet hybrids.

  4. Competing charge, spin, and superconducting orders in underdoped YBa2Cu3Oy

    DEFF Research Database (Denmark)

    Hücker, M.; Christensen, Niels Bech; Holmes, A. T.

    2014-01-01

    order decreases with underdoping to TCDW~90 K in YBa2Cu3O6.44. Together with a weakened order parameter this suggests a competition between CDW and SDW orders. In addition, the CDW order in YBa2Cu3O6.44 shows the same type of competition with superconductivity as a function of temperature and magnetic...

  5. Effects of carbon nanotube addition on superconductivity in Y-Ba-Cu-O bulk superconductors

    Science.gov (United States)

    Inoue, K.; Miyake, Y.; Miryala, M.; Murakami, M.

    2017-07-01

    Bulk Y-Ba-Cu-O superconductors have significant potential for engineering applications due to high critical current density, which is attributed to the presence of pinning centers such as Y2BaCuO5. The introduction of nano-sized secondary phase is known to act as more effective pinning center than those in micron sizes. The diameter of carbon nanotube (CNT) is close to that of the coherence length of high-temperature superconductors, which is expected to improve the flux pinning performance. We have investigated the effects of CNT addition on the microstructure, superconducting transition temperature (T c), and critical current density (J c) of YBa2Cu3O x (Y123) based bulk superconductors. SEM observation showed the distribution of needle-like particles around 100 nm in length in the Y123 matrix for the CNT added samples. The highly porous texture was also observed for the excess addition of CNT. T c was enhanced from 90.5 K to 91.8 K with increasing CNT addition. It is probable that carbon originated from CNT suppressed oxidation and carrier doping. Jc exhibited the highest value for 0.25 wt% CNT added sample. This suggests that nano-sized needle-like particles act as effective pinning centers. However, a further increase of CNT led to the decline of J c, which suggests that there is an optimum amount of CNT for the improvement of J c. The secondary peak was observed for the sample with 1 wt% CNT addition, where CO3 substitutions with Cu site at the Cu-O chain might induce oxygen vacancies leading to the field induced pinning.

  6. Superconductivity in spinel-type compounds CuRh2S4 and CuRh2Se4

    OpenAIRE

    1995-01-01

    An extensive study of electrical resistivity, ac magnetic susceptibility, magnetization, specific heat, and NMR has been made on high purity samples of the spinel compounds CuRh2S4 and CuRh2Se4. The superconducting transitions occur at 4.70 K in CuRh2S4 and 3.48 K in CuRh2Se4. The magnetic susceptibilities show perfect diamagnetism in both compounds. Upper critical fields at T=0 are estimated to be 20.0 and 4.40 kOe, the lower critical fields at T=0 are 70 and 95 Oe, respectively. The thermod...

  7. Negative lattice expansion from the superconductivity--antiferromagnetism crossover in ruthenium copper oxides.

    Science.gov (United States)

    McLaughlin, A C; Sher, F; Attfield, J P

    2005-08-11

    The mechanism of high-transition-temperature (high-T(c)) superconductivity in doped copper oxides is an enduring problem. Antiferromagnetism is established as the competing order, but the relationship between the two states in the intervening 'pseudogap' regime has become a central puzzle. The role of the crystal lattice, which is important in conventional superconductors, also remains unclear. Here we report an anomalous increase of the distance between copper oxide planes on cooling, which results in negative thermal volume expansion, for layered ruthenium copper oxides that have been doped to the boundary of antiferromagnetism and superconductivity. We propose that a crossover between these states is driven by spin ordering in the ruthenium oxide layers, revealing a novel mechanism for negative lattice expansion in solids. The differences in volume and lattice strain between the distinct superconducting and antiferromagnetic states can account for the phase segregation phenomena found extensively in low-doped copper oxides, and show that Cooper pair formation is coupled to the lattice. Unusually large variations of resistivity with magnetic field are found in these ruthenium copper oxides at low temperatures through coupling between the ordered Ru and Cu spins.

  8. Ubiquitous long-range antiferromagnetic coupling across the interface between superconducting and ferromagnetic oxides

    Science.gov (United States)

    de Luca, G. M.; Ghiringhelli, G.; Perroni, C. A.; Cataudella, V.; Chiarella, F.; Cantoni, C.; Lupini, A. R.; Brookes, N. B.; Huijben, M.; Koster, G.; Rijnders, G.; Salluzzo, M.

    2014-11-01

    The so-called proximity effect is the manifestation, across an interface, of the systematic competition between magnetic order and superconductivity. This phenomenon has been well documented and understood for conventional superconductors coupled with metallic ferromagnets; however it is still less known for oxide materials, where much higher critical temperatures are offered by copper oxide-based superconductors. Here we show that, even in the absence of direct Cu-O-Mn covalent bonding, the interfacial CuO2 planes of superconducting La1.85Sr0.15CuO4 thin films develop weak ferromagnetism associated to the charge transfer of spin-polarised electrons from the La0.66Sr0.33MnO3 ferromagnet. Theoretical modelling confirms that this effect is general to all cuprate/manganite heterostructures and the presence of direct bonding only affects the strength of the coupling. The Dzyaloshinskii-Moriya interaction, also at the origin of the weak ferromagnetism of bulk cuprates, propagates the magnetisation from the interface CuO2 planes into the superconductor, eventually depressing its critical temperature.

  9. Ubiquitous long-range antiferromagnetic coupling across the interface between superconducting and ferromagnetic oxides.

    Science.gov (United States)

    De Luca, G M; Ghiringhelli, G; Perroni, C A; Cataudella, V; Chiarella, F; Cantoni, C; Lupini, A R; Brookes, N B; Huijben, M; Koster, G; Rijnders, G; Salluzzo, M

    2014-11-24

    The so-called proximity effect is the manifestation, across an interface, of the systematic competition between magnetic order and superconductivity. This phenomenon has been well documented and understood for conventional superconductors coupled with metallic ferromagnets; however it is still less known for oxide materials, where much higher critical temperatures are offered by copper oxide-based superconductors. Here we show that, even in the absence of direct Cu-O-Mn covalent bonding, the interfacial CuO2 planes of superconducting La(1.85)Sr(0.15)CuO(4) thin films develop weak ferromagnetism associated to the charge transfer of spin-polarised electrons from the La(0.66)Sr(0.33)MnO(3) ferromagnet. Theoretical modelling confirms that this effect is general to all cuprate/manganite heterostructures and the presence of direct bonding only affects the strength of the coupling. The Dzyaloshinskii-Moriya interaction, also at the origin of the weak ferromagnetism of bulk cuprates, propagates the magnetisation from the interface CuO2 planes into the superconductor, eventually depressing its critical temperature.

  10. Nonlocal transport in superconducting oxide nanostructures

    Science.gov (United States)

    Veazey, Joshua; Cheng, Guanglei; Lu, Shicheng; Tomczyk, Michelle; Irvin, Patrick; Huang, Mengchen; Wung Bark, Chung; Ryu, Sangwoo; Eom, Chang-Beom; Levy, Jeremy

    2013-03-01

    We report nonlocal transport signatures in the superconducting state of nanostructures formed[2] at the LaAlO3/SrTiO3 interface using conductive AFM lithography. Nonlocal resistances (nonlocal voltage divided by current) are as large as 200 Ω when 2-10 μm separate the current-carrying segments from the voltage-sensing leads. The nonlocal resistance reverses sign at the local critical current of the superconducting state. Features observed in the nonlocal V-I curves evolve with back gate voltage and magnetic field, and are correlated with the local four-terminal V-I curves. We discuss how nonlocal and local transport effects in LaAlO3/SrTiO3 nanostructures may result from the electronic phase separation and superconducting inhomogeneity reported by others in planar structures[3]. This work is supported by AFOSR (FA9550-10-1-0524) and NSF DMR-0906443

  11. Antiferromagnetic ordering in superconducting YBa2Cu3O6.5

    DEFF Research Database (Denmark)

    Sidis, Y.; Ulrich, C.; Bourges, P.

    2001-01-01

    Commensurate antiferromagnetic ordering has been observed in the superconducting high-T-c. cuprate YBa2Cu3O6.5 (T-c = 55 K) by polarized and unpolarized elastic neutron scattering. The magnetic peak intensity exhibits a marked enhancement at T-c. Zero-field muon-spin-resonance experiments...... demonstrate that the staggered magnetization is not truly static but fluctuates on a nanosecond time scale. These results point towards an unusual spin density wave state coexisting with superconductivity....

  12. Properties of superconducting Bi-Sr-Ca-Cu-O system remelted under higher gravity conditions

    Energy Technology Data Exchange (ETDEWEB)

    Volkov, M.P.; Melekh, B.T.; Parfeniev, R.V.; Kartenko, N.F. (A.F. Ioffe Physical Technical Inst., Academy of Sciences, Moscow (Russia)); Regel, L.L.; Turchaninov, A.M. (Space Research Inst., Academy of Sciences, Moscow (Russia))

    1992-04-01

    The structure and magnetic properties of high Tc superconductor Bi-Sr-Ca-Cu-O samples remelted under 1g{sub 0}, 8g{sub 0} and 12g{sub 0} gravity levels have been investigated. Superconducting properties make a change along the ingots. The dependence of structural and superconducting properties on the gravity level and their time degradation have been observed. (orig.).

  13. Symmetry of the superconducting order parameter in Bi2Sr2CaCu2Ox

    Science.gov (United States)

    Kelley, R. J.; Ma, Jian; Margaritondo, G.; Onellion, M.

    1993-12-01

    We analyzed the symmetry of the superconducting-phase condensate of Bi2Sr2CaCu2Ox with photoemission at high energy and angular resolution. The result unambiguously demonstrates that the photohole must include non-s-wave components. Under the hypothesis of a pure d-wave symmetry, this would be identified as dxz+dyz. Our superconducting state data are, specifically, incompatible with pure d2x-y2 symmetry. Mixed symmetries, however, cannot be excluded as long as they include a non-s-wave component. We specifically observe a change in the symmetry of electronic states between the normal state and the superconducting state.

  14. Dark counts in superconducting single-photon NbN/NiCu detectors

    Science.gov (United States)

    Parlato, L.; Nasti, U.; Ejrnaes, M.; Cristiano, R.; Myoren, H.; Sobolewski, Roman; Pepe, G.

    2015-05-01

    Nanostripes of hybrid superconductor/ferromagnetic (S/F) NbN/NiCu bilayers and pure superconducting NbN nanostripes have been investigated in dark count experiments. Presence of a ferromagnetic layer influences the superconducting properties of the S/F bilayer, such as the critical current density and the transient photoresponse. The observed significant decrease of the dark-count rate is discussed in terms of vortex-related fluctuation models to shed more light in the intriguing question of the basic mechanism responsible for dark counts in superconducting nanostripe single photon detectors.

  15. Superconductivity of Bi1.6Pbo.4Sr2Ca3Cu4O12

    Institute of Scientific and Technical Information of China (English)

    Atilla Coskun; Ahmet Ekicibil; Bekir Ozgelik

    2002-01-01

    The superconducting ceramics Bi1.6Pbo.4Sr2Ca3Cu4O12 have been prepared by the melt-casting method. A zero resistance temperature at 60 K has been observed. It has been found that the superconducting phase temperature Tc increases with increasing sintering temperature. The effect of Pb content on the superconductivity of the ceramic has been studied. The microstructure of the samplehas been investigated by scanning electron microscopy. Phase analysis has been carried out by x-ray diffraction patterns and energy dispersive analysis through x-ray spectroscopy.

  16. Superconductivity in the high-Tc Bi-Ca-Sr-Cu-O system - Phase identification

    Science.gov (United States)

    Hazen, R. M.; Prewitt, C. T.; Angel, R. J.; Ross, N. L.; Finger, L. W.

    1988-01-01

    Four phases are observed in superconducting Bi-Ca-Sr-Cu-O samples. The superconducting phase, with onset temperature near 120 K, is a 15.4-A-layered compound with composition near Bi2Ca1Sr2Cu2O9 and an A-centered orthorhombic unit subcell 5.41 x 5.44 x 30.78 A. X-ray diffraction and electron microscopy data are consistent with a structure of alternating perovskite and Bi2O2 layers. High-resolution transmission electron microscopy images reveal a b-axis superstructure of 27.2 A, numerous (001) stacking faults, and other defects.

  17. Superconducting oxides containing sulphate and phosphate groups

    Science.gov (United States)

    Scorzelli, R. B.; Baggio-Saitovitch, E.; Giordanengo, B.; Elmassalami, M.; Dominguez, A. B.; Bustamante Dominguez, A.

    1994-12-01

    The effects of partial substitution of Sr and Ca in Y-Ba-Cu-O related materials containing sulphate and phosphate groups have been investigated. e57Fe Mössbauer measurements were performed on samples doped with lat. % e57Fe and the spectral components related to different Cu sites and oxygen vacancies.

  18. Stress dependent oxidation of sputtered niobium and effects on superconductivity

    Science.gov (United States)

    David Henry, M.; Wolfley, Steve; Monson, Todd; Clark, Blythe G.; Shaner, Eric; Jarecki, Robert

    2014-02-01

    We report on the suppression of room temperature oxidation of DC sputtered niobium films and the effects upon the superconductive transition temperature, Tc. Niobium was sputter-deposited on silicon dioxide coated 150 mm wafers and permitted to oxidize at room temperature and pressure for up to two years. Resistivity and stress measurements indicate that tensile films greater than 400 MPa resist bulk oxidation with measurements using transmission electron microscope, electron dispersive X-ray spectroscopy, x-ray photoelectric spectroscopy, and secondary ion mass spectrometry confirming this result. Although a surface oxide, Nb2O5, consumed the top 6-10 nm, we measure less than 1 at. % oxygen and nitrogen in the bulk of the films after the oxidation period. Tc measurements using a SQUID magnetometer indicate that the tensile films maintained a Tc approaching the dirty superconductive limit of 8.4 K after two years of oxidation while maintaining room temperature sheet resistance. This work demonstrates that control over niobium film stress during deposition can prevent bulk oxidation by limiting the vertical grain boundaries ability to oxidize, prolonging the superconductive properties of sputtered niobium when exposed to atmosphere.

  19. Influence of additions and radiation damage on the superconducting properties of sintered YBa 2Cu 3O 7 - gd

    Science.gov (United States)

    Koblischka, M. R.; Schuster, Th.; Kronmüller, H.

    1993-06-01

    Using the high-resolution Faraday (HRF) technique, domain patterns of sintered YBa 2Cu 3O 7 - δ samples containing additions of Ag 2O and Y 2BaCuO 5 are obtained. Similar observations are carried out on sintered YBa 2Cu 3O 7- δ samples with reduced oxygen content and on electron-irradiated samples. The penetration of flux into sintered high- Tc superconductors is found to be totally different from single crystalline materials (single crystals and epitaxial thin films) as the Abrikosov vortices penetrate the sample not as a whole thus forming a so-called flux front. Only a flux penetration into single superconducting grains is observed. From the measured flux density profiles, the intragrain critical current densities are determined locally. It is found that the chemical impurity phases do not affect the intragranular flux density distribution and the intragranular critical current density, but the decomposition of the Ag 2O leads to an improved oxygen stoichiometry in these samples. Electron irradiation is found to enhance the intragrain critical current densities, whereas the oxygen reduction leads to reduced intragrain currents. To determine the influence of the additions also on the intergrain critical current densities, standard four-point transport current measurements are carried out on the same samples. It is found that a maximum enhancement of the critical current density is obtained by the addition of 10 wt% silver oxide; however, this critical current density is drastically reduced by applying small external magnetic fields. The lower critical field of the matrix and the corresponding Josephson penetration depth are determined from transport current measurements. The Ag 2O additions and the green phase particles are found to separate the superconducting YBa 2Cu 3O 7- δ grains. The resulting larger widths of the barriers between the superconducting grains are found to cause a stronger influence of external magnetic fields on the intergrain critical

  20. Superconductivity above 10 K in Non-Cuprate Oxides

    OpenAIRE

    Johnston, David C.

    2010-01-01

    Beginning in 1973, several non-cuprate transition metal and non-transition metal oxides were discovered with superconducting transition temperatures between 10 and 30 K. Retrospectives about these discoveries in spinel structure LiTi2O4 and perovskite structure (Ba,K)(Bi,Pb)O3 are given.

  1. Influence of Oxygen Content on the Superconductivity of Bi-Based Oxides Homologous to 2212 Phase

    Science.gov (United States)

    Deshimaru, Yuichi; Otani, Tetsuya; Shimizu, Youichi; Miura, Norio; Yamazoe, Noboru

    1991-10-01

    Thermal desorption of oxygen and its relevance to superconductivity were examined for a series of oxides Bi2Sr2-xCa1+xCu2Oy (x=0, 0.25, 0.5, 0.8 and 1.0) isostructural to the 2212 phase. The total oxygen desorbed up to 600°C amounted to 2˜ 3× 10-5 mol/g for each oxide. Tc was constant at about 80 K for all the as-prepared oxides but Tc decreased linearly with x from 97 K (x=0) to 67 K (x=1.0) for the oxygen-desorbed oxides. The total oxygen contents (y) were determined and correlated with Tc, which increased for x=0 and 0.25, whereas it went through a maximum at about y=8.15 for x=0.8.

  2. Chemical Oxidation of La2CuO4 Epitaxial Thin Films Grown by Pulsed Laser Deposition

    Institute of Scientific and Technical Information of China (English)

    WANG Chun-Chang; YAN Yun-Jie; ZHU Jing

    2007-01-01

    Chemical oxidation is used to induce superconductivity in La2CuO4 expitaxial thin films fabricated by pulsed laser deposition technique. Details about the influence of oxidation time on structural, surface morphology, Raman spectra, and electrical properties have been investigated. The results convince that successful uptake of oxygen occurs in the oxidized films, and the content of the inserted oxygen increases with increasing oxidation interval. The possible mechanism for the excess oxygen insertion into the film is also discussed.

  3. Incommensurate magnetism in non-superconducting PrBa2Cu3O6.92

    DEFF Research Database (Denmark)

    Boothroyd, A.T.; Hill, J.P.; McMorrow, D.F.

    1999-01-01

    We report the discovery of incommensurate magnetic order in non-superconducting single crystals PrBa2Cu3O6.92. Resonant X-ray magnetic scattering at the Pr L-II and L-III edges and high resolution neutron diffraction were used to characterise the magnetic order on the different magnetic sublattices...

  4. New magnetic coherence effect in superconducting La2-xSrxCuO4

    DEFF Research Database (Denmark)

    Mason, T.E.; Schröder, A.; Aeppli, G.

    1996-01-01

    We have used inelastic neutron scattering to examine the magnetic fluctuations at intermediate frequencies in the simplest high temperature superconductor, La2-xSrxCuO4. The suppression of the low energy magnetic response in the superconducting state is accompanied by an increase in the response...

  5. Bulk superconductivity in Tl 2Ba 2CaCu 2O 8 and TlBa 2Ca 2Cu 3O 9 phases

    Science.gov (United States)

    Sulpice, A.; Giordanengo, B.; Tournier, R.; Hervieu, M.; Maignan, A.; Martin, C.; Michel, C.; Provost, J.

    1988-09-01

    Well-crystallized Tl 2Ba 2CaCu 2O 8 phases have been observed superconducting or normal below 108 K depending on their stoichiometry. This observation is an evidence that a (Cu IL&.zbnd;O -) mixed valence induced by vacancies or substitution on different sites gives rise to superconductivity in this phase. The new phase TlBa 2Ca 2CuO 9 which intrinsically contains a mixed valence has been observed as having a sharp transition to bulk superconductivity in the Meissner effect at a critical temperature of 120 K. This temperature is much higher than the recently observed one.

  6. Oxygen stabilization induced enhancement in superconducting characteristics of high-Tc oxides

    Science.gov (United States)

    Wu, M. K.; Chen, J. T.; Huang, C. Y.

    1991-01-01

    In an attempt to enhance the electrical and mechanical properties of the high temperature superconducting oxides, high T(sub c) composites were prepared composed of the 123 compounds and AgO. The presence of extra oxygen due to the decomposition of AgO at high temperature is found to stabilize the superconducting 123 phase. Ag is found to serve as clean flux for grain growth and precipitates as pinning center. Consequently, almost two orders of magnitude enhancement in critical current densities were also observed in these composites. In addition, these composites also show much improvement in workability and shape formation. On the other hand, proper oxygen treatment of Y5Ba6Cu11Oy was found to possibly stabilize superconducting phase with T(sub c) near 250 K. I-V, ac susceptibility, and electrical resistivity measurements indicate the existence of this ultra high T(sub c) phase in this compound. Detailed structure, microstructure, electrical, magnetic and thermal studies of the superconducting composites and the ultra high T(sub c) compound are presented and discussed.

  7. Triplet superconductivity in oxide ferromagnetic interlayer of mesa-structure

    Science.gov (United States)

    Ovsyannikov, G. A.; Y Constantinian, K.; Sheerman, A. E.; Shadrin, A. V.; Kislinski, Yu V.; Khaydukov, Yu N.; Mustafa, L.; Kalabukhov, A.; Winkler, D.

    2015-03-01

    We present experimental data on Nb-Au/La0.7Sr0.3MnO3/SrRuO3/YBa2Cu3O7-δ mesa- structure with in plane linear size 10÷50 μm. The mesa-structures were patterned from the epitaxial heterostructures fabricated by pulsed laser ablation and magnetron sputtering. Superconducting critical current was observed for mesa-structures with the interlayer thicknesses up to 50 nm. In the mesa-structures with just one, either La0.7Sr0.3MnO3 or SrRuO3 interlayer with a thickness larger than 10 nm no superconducting current was observed. The registered superconducting current for the mesa-structures with a thinner interlayer is attributed to pinholes. Obtained results are discussed in terms of superconducting long-range triplet generation at interfaces of superconductor and a composite ferromagnet consisting of ferromagnetic materials with non-collinear magnetization.

  8. Broken bond symmetry assists stripe pinning in superconducting La2-xSrxCuO4

    Science.gov (United States)

    Tranquada, John; Jacobsen, H.; Zaliznyak, I. A.; Huecker, M.; Gu, G. D.; Savici, A. T.; Winn, B.; Chang, S.

    There has been evidence for quite some time for some degree of charge and spin stripe order in La2-xSrxCuO4 (LSCO). This has been a bit surprising as the crystal structure is supposed to lack the anisotropic Cu-O bonds that lead to robust stripe pinning in La2-xBaxCuO4. Using neutron scattering measurements on the HYSPEC instrument at the Spallation Neutron Source, we have discovered evidence for broken bond symmetry and strong associated lattice fluctuations in an LSCO crystal with x = 0 . 07. The broken bond symmetry occurs within the orthorhombic phase. We also observe quasielastic incommensurate spin excitations that coexist with the bulk superconductivity, suggesting some degree of pair-density-wave order in the superconducting state. Work at BNL supported by Office of Basic Energy Sciences, US DOE, under Contract No. DE-SC00112704.

  9. INTERFACE DISORDER CONTROLLED SUPERCONDUCTIVITY YBa2Cu3O7 / SrTiO3 SUPERLATTICES

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Barriocanal, Javier [Universidad Complutense, Spain; Rivera-Calzada, Alberto [Universidad Complutense, Spain; Sefrioui, Z. [Universidad Complutense, Spain; Arias, D [Universidad Complutense, Spain; Varela del Arco, Maria [ORNL; Leon, C. [Universidad Complutense, Spain; Pennycook, Stephen J [ORNL; Santamaria, J. [Universidad Complutense, Spain

    2013-01-01

    We report on the coherent growth of ultrathin YBa2Cu3O7 (YBCO) layers on SrTiO3 (STO) in YBCO/STO superlattices. The termination plane of the STO is TiO2 and the CuO chains are missing at the interface. Disorder (steps) at the STO interface cause alterations of the stacking sequence of the intra-cell YBCO atomic layers. Stacking faults give rise to antiphase boundaries which break the continuity of the CuO2 planes and depress superconductivity. We show that superconductivity is directly controlled by interface disorder outlining the importance of pair breaking and localization by disorder in ultrathin layers.

  10. ELECTROCHEMICAL OXIDATION OF La2CuO4 SINGLE CRYSTALS

    Institute of Scientific and Technical Information of China (English)

    Chen Ling; Huang Yu-zhen; Zhou Fang; Dong Cheng; Che Guang-can; Zhao Zhong-xian

    2000-01-01

    Bulk superconducting La2CuO4+ single crystals are obtained byusing electrochemical intercalation technique from the as-growninsulating samples. Oxidation is carried out by constant currentI=10 at temperature T=70 and room temperature, respectively. Structure and magnetic properties are studied by low-temperature X-ray diffraction and susceptibility measurements. A superconducting phase with Tc of 19K and -0.12 can be attributed to the formation of oxygen clusters. Room temperature oxidation is inhomogeneous: two superconducting phases with T c1 of 24K and Tc2 of 8K and an antiferromagnetic phase are coexisting in the crystal. It is found that the appearance of Tc in this system has the step tendency.

  11. Friction and wear behavior of the superconducting compound oxide of Ag/Bi_(1. 6) Pb_(0. 4)Sr_2Ca_2Cu_3O_(10-x)%超导Ag/Bi_(1.6)Pb_(0.4)Sr_2Ca_2Cu_3O_(10-x)复合氧化物摩擦磨损性能

    Institute of Scientific and Technical Information of China (English)

    彭义; 李长生; 董丽荣; 丁巧党; 王昊璐

    2009-01-01

    The superconducting Bi_(1.6)Pb_(0.4)Sr_2Ca_2Cu_3O_(10-x) samples were prepared by the solid-state synthesismethod. The tribological properties were measured on the friction and wear tester from ambient temperature toliquid nitrogen temperature. The results indicate that the friction coefficient of Bi_(1.6)Pb_(0.4)Srz_2Ca_2Cu_30_(10-x) againststainless steel is about 0.35 at the ambient temperature and decreases abruptly to half of the normal state value whenthe temperature is below the superconducting transition temperature of Bi_(1.6)Pb_(0. 4_Srz_2Ca_2Cu_30_(10-x). Themeasurements prove directly the effect of electronic excitation on friction. Moreover, the Ag/Bi_(1.6) Pb_(0.4)Sr_2Ca_2Cu_3O_(10-x) composite samples were prepared by sintering Bi_(1.6)Pb_(0.4)Sr_2Ca_2Cu_3O_(10-x) with Ag at different mass fractions to improve the tribological properties of Bi_(1.6)Pb_(0.4)Sr_2Ca_2Cu_3O_(10-x) at room temperature. The experimental results show that the friction coefficient of 10 Wt%Ag/Bi_(1. 6) Pb_(0. 4)Sr_2Ca_2Cu_3O_(10-x) is about 0. 2~O. 3 and the wear rate is 4. 57×10~(-4)mm~3·(N·m)~(-1), and the superconductivity of 10 Wt% Ag/Bi_(1. 6) Pb_(0. 4)Sr_2Ca_2Cu_3O_(10-x) is not degenerated.%为适应20℃~-200℃温度的适用范围, 采用固相法制备了Bi_(1.6) Pb_(0. 4)Sr_2Ca_2Cu_3O_(10-x)超导材料, 用摩擦磨损试验机测试了Bi_(1.6) Pb_(0. 4)Sr_2Ca_2Cu_3O_(10-x)从液氮温度至室温的摩擦学性能. 结果表明: 在室温20℃下, Bi_(1. 6) Pb_(0. 4)Sr_2Ca_2Cu_3O_(10-x)与对偶件轴承钢盘对摩时, 摩擦系数约为0. 35, 当温度降到超导转变温度以下时(液氮温度-170℃)摩擦系数大幅度降低, Bi_(1. 6) Pb_(0. 4)Sr_2Ca_2Cu_3O_(10-x)超导态摩擦系数为正常态值的一半, 实验证明了电子激励对摩擦能量耗散的作用. 为改善室温下Bi_(1. 6) Pb_(0. 4)Sr_2Ca_2Cu_3O_(10-x)摩擦学性能, 掺杂不同质量分数Ag作为润滑组元, 制备了Ag/Bi_(1. 6) Pb_(0. 4)Sr_2Ca_2Cu_3O_(10-x)

  12. Homogeneous lattice disorder and superconducting properties of YBa2Cu3O6.9 films.

    Science.gov (United States)

    Pavuna, Davor; Gauzzi, Andrea

    We discuss the striking changes of the superconducting properties of YBa2Cu3O6.9 films to the homogeneous lattice disorder, induced by varying growth temperatures: Tc decreases with increasing disorder, while the width of the resistive transition and the normal state resistivity increase. We estimate the length scale of such dis- order from the broadening DJ of the lt; 005 > X-ray diffraction rocking curves. The suppression of superconductivity and normal conductivity scales as DJ and appears for in-plane lattice coherence lengths rc ≫ 1/DJ smaller than about 10 nm.

  13. Deformation processing of high-Tc superconducting oxides

    Science.gov (United States)

    Rajan, K.; German, R. M.; Knorr, D. B.; Maccrone, R. K.; Misiolek, W.; Wright, R. N.

    1989-04-01

    Plastic deformation and texture development in polycrystalline YBa2Cu3O7- δ has been studied to expedite the process development of high-critical-temperature (high-Tc) superconducting wires and tapes. It is anticipated that deformation texture will be a major processing consideration in terms of maximizing critical current density, assessing conductor-fabrication options in light of critical current density, and developing such mechanical properties as strength, toughness and thermal fatigue. The intrinsic texture development in YBa2Cu3O7- δ deformation processing should be highly beneficial, insofar as the c axes of the crystals tend to become oriented along the compression axis. This means that conducting tapes and wires formed by rolling, extrusion and drawing can develop textures with the c axis in the transverse or radial direction, thus maximizing the flow of current along the length of the conductor.

  14. Tunable spin polarization and superconductivity in engineered oxide interfaces.

    Science.gov (United States)

    Stornaiuolo, D; Cantoni, C; De Luca, G M; Di Capua, R; Di Gennaro, E; Ghiringhelli, G; Jouault, B; Marrè, D; Massarotti, D; Miletto Granozio, F; Pallecchi, I; Piamonteze, C; Rusponi, S; Tafuri, F; Salluzzo, M

    2016-03-01

    Advances in growth technology of oxide materials allow single atomic layer control of heterostructures. In particular delta doping, a key materials' engineering tool in today's semiconductor technology, is now also available for oxides. Here we show that a fully electric-field-tunable spin-polarized and superconducting quasi-2D electron system (q2DES) can be artificially created by inserting a few unit cells of delta doping EuTiO3 at the interface between LaAlO3 and SrTiO3 oxides. Spin polarization emerges below the ferromagnetic transition temperature of the EuTiO3 layer (TFM = 6-8 K) and is due to the exchange interaction between the magnetic moments of Eu-4f and of Ti-3d electrons. Moreover, in a large region of the phase diagram, superconductivity sets in from a ferromagnetic normal state. The occurrence of magnetic interactions, superconductivity and spin-orbit coupling in the same q2DES makes the LaAlO3/EuTiO3/SrTiO3 system an intriguing platform for the emergence of novel quantum phases in low-dimensional materials.

  15. Tunable spin polarization and superconductivity in engineered oxide interfaces

    Science.gov (United States)

    Stornaiuolo, D.; Cantoni, C.; de Luca, G. M.; di Capua, R.; di. Gennaro, E.; Ghiringhelli, G.; Jouault, B.; Marrè, D.; Massarotti, D.; Miletto Granozio, F.; Pallecchi, I.; Piamonteze, C.; Rusponi, S.; Tafuri, F.; Salluzzo, M.

    2016-03-01

    Advances in growth technology of oxide materials allow single atomic layer control of heterostructures. In particular delta doping, a key materials' engineering tool in today's semiconductor technology, is now also available for oxides. Here we show that a fully electric-field-tunable spin-polarized and superconducting quasi-2D electron system (q2DES) can be artificially created by inserting a few unit cells of delta doping EuTiO3 at the interface between LaAlO3 and SrTiO3 oxides. Spin polarization emerges below the ferromagnetic transition temperature of the EuTiO3 layer (TFM = 6-8 K) and is due to the exchange interaction between the magnetic moments of Eu-4f and of Ti-3d electrons. Moreover, in a large region of the phase diagram, superconductivity sets in from a ferromagnetic normal state. The occurrence of magnetic interactions, superconductivity and spin-orbit coupling in the same q2DES makes the LaAlO3/EuTiO3/SrTiO3 system an intriguing platform for the emergence of novel quantum phases in low-dimensional materials.

  16. 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.

  17. Fabrication of YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} superconducting nanofibres by electrospinning

    Energy Technology Data Exchange (ETDEWEB)

    Cui Xuemei [Department of Advanced Organic Materials and Textile System Engineering, Chungnam National University, Daejeon 305-764 (Korea, Republic of); Lyoo, Won Seok [School of Textiles, Yeungnam University, Kyungsan-city 712-429 (Korea, Republic of); Son, Won Keun [Research Institute of Advanced Materials, Chungnam National University, Daejeon 305-764 (Korea, Republic of); Park, Dae Hun [Division of Nano Science, Ewha Womans University, Seoul 120-750 (Korea, Republic of); Choy, Jin Ho [Division of Nano Science, Ewha Womans University, Seoul 120-750 (Korea, Republic of); Lee, Taek Seung [Department of Advanced Organic Materials and Textile System Engineering, Chungnam National University, Daejeon 305-764 (Korea, Republic of); Park, Won Ho [Department of Advanced Organic Materials and Textile System Engineering, Chungnam National University, Daejeon 305-764 (Korea, Republic of)

    2006-12-15

    YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} superconducting nanofibres were successfully fabricated via the electrospinning method in combination with the sol-gel process. The solution was prepared by the sol-gel process with a homogeneous aqueous PVA solution containing Y, Ba, and Cu acetates. The viscosity of the precursor sol for electrospinning was controlled by the evaporation of solvent and a condensation reaction. The electrospun nanofibres were pyrolysed to remove PVA or volatile components, and then sintered to generate a superconducting phase. The critical transition temperature (T{sub c}) of superconducting YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} nanofibres was measured by DC susceptibility tests. By optimizing the electrospinning process and following heat treatments, superconducting YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} nanofibres with a T{sub c} = 92.2 K could be produced.

  18. Electrodeposited NiCu Alloy Catalysts for Glucose Oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Lim, Jieun; Park, Hansoo; Kim, Sookil [Chung-Ang Univ., Seoul (Korea, Republic of); Ahn, Sang Hyun; Jang, Jong Hyun [Korea Institute of Science and Technology, Seoul (Korea, Republic of)

    2014-07-15

    NiCu alloys have been suggested as potential candidates for catalysts in glucose oxidation. In this study, NiCu alloys with different compositions were prepared on a glassy carbon substrate by changing the electrodeposition potential to examine the effect of Ni/Cu ratios in alloys on catalytic activity toward glucose oxidation. Cyclic voltammetry and chronoamperometry showed that NiCu alloys had higher catalytic activity than pure Ni and Cu catalysts. Especially, Ni{sub 59}Cu{sub 41} had superior catalytic activity, which was about twice that of Ni at a given oxidation potential. X-ray analyses showed that the oxidation state of Ni in NiCu alloys was increased with the content of Cu by lattice expansion. Ni components in alloys with higher oxidation state were more effective in the oxidation of glucose.

  19. 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

  20. Oxide Nanotube Analogues: CuO Nanobarrels

    Energy Technology Data Exchange (ETDEWEB)

    H. H. Farrell; R. D. Parra

    2011-11-01

    The principle 'form follows function' which dominated much of twentieth century architechture and industrial design has its parallel on the nanolevel in the concept of 'function follows form'. This has been realized in many technologically valuable ways on this level via nanoparticles such as nanotubes and quantum dots, for example. Now, a new material, copper oxide (CuO) nanobarrels, offers still another opportunity to exploit unusual form to obtain new functionality. Recently, CuO 'rings' on the order of 100 nm diameter have been observed experimentally by El-Azab and Liang (2003). In a separate effort, we have used first principles density functional calculations to investigate smaller, single walled CuO structures that appear to be nanotubes or nanobarrels with a square unit mesh rather than the hexagonal mesh of carbon nanotubes. These structures are unique and novel, and almost certainly will yield fascinating results when studied experimentally.

  1. 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.

  2. RE-Ba-Cu-O for high functional superconducting permanent magnet

    Energy Technology Data Exchange (ETDEWEB)

    Yoo, S.I.; Higuchi, T. [Railway Technical Research Inst., Tokyo (Japan)]|[Superconductivity Research Laboratory, ISTEC, Minato-ku, Tokyo 185 (Japan); Sakai, N.; Murakami, M. [Superconductivity Research Laboratory, ISTEC, Minato-ku, Tokyo 185 (Japan); Fujimoto, H. [Railway Technical Research Inst., Tokyo (Japan)

    1998-05-01

    Among various potential applications of melt-textured RE-Ba-Cu-O (REBCO, RE: rare earth elements) superconductors, we have examined the bulk application as the superconducting permanent magnet, especially for the magnetically-levitated (MAGLEV) train. Compared with Y-Ba-Cu-O (YBCO), oxygen-controlled melt-growth (OCMG)-processed LREBCO (LRE: light rare earth elements) bulk superconductors are more promising for this application because of larger critical current density (J{sub c}) values in high field and higher irreversibility field (B{sub irr}) within the range of the liquid nitrogen refrigeration (63-77 K), implying that even higher trapped fields (B{sub t}) are achievable in principle. In this paper, material requirements of superconducting bulks for the MAGLEV train are first presented and then processing aspects for the fabrication of good LREBCO bulks are described. (orig.) 19 refs.

  3. Strong critical current density enhancement in NiCu/NbN superconducting nanostripes for optical detection

    Science.gov (United States)

    Marrocco, N.; Pepe, G. P.; Capretti, A.; Parlato, L.; Pagliarulo, V.; Peluso, G.; Barone, A.; Cristiano, R.; Ejrnaes, M.; Casaburi, A.; Kashiwazaki, N.; Taino, T.; Myoren, H.; Sobolewski, Roman

    2010-08-01

    We present measurements of ferromagnet/superconductor (NiCu/NbN) and plain superconducting (NbN) nanostripes with the linewidth ranging from 150 to 300 nm. The NiCu (3 nm)/NbN (8 nm) bilayers, as compared to NbN (8 nm), showed a up to six times increase in their critical current density, reaching at 4.2 K the values of 5.5 MA/cm2 for a 150 nm wide nanostripe meander and 12.1 MA/cm2 for a 300 nm one. We also observed six-time sensitivity enhancement when the 150 nm wide NiCu/NbN nanostripe was used as an optical detector. The strong critical current enhancement is explained by the vortex pinning strength and density increase in NiCu/NbN bilayers and confirmed by approximately tenfold increase in the vortex polarizability factor.

  4. Void formation in Nb3Sn-Cu superconducting wire produced by the external tin process

    Science.gov (United States)

    Verhoeven, J. D.; Efron, A.; Gibson, E. D.; Cheng, C. C.

    1986-03-01

    The tin (Sn) diffusion step for producing Nb3Sn-Cu superconducting wire by the external Sn process was modeled in experiments where either pure Sn or a Cu-Sn alloy was plated on sheets of either pure Cu or a Cu-Sn bronze. Each stage of the three-stage solid-state diffusion process was evaluated and it was found that rows of voids are produced in stage I of the process. These voids coarsen in stages II and III and in the worst case they are observed to coalesce and cause complete spalling away of the Sn-rich diffusion layers. Methods for minimizing void formation and possible causes of the void formation are discussed.

  5. Co-doped Bi2Sr2CaCu2Ox: Anderson localization and superconductivity

    Science.gov (United States)

    Onellion, M.; Quitmann, C.; Ma, J.; Alméras, P.; Berger, H.; Margaritondo, G.

    1994-12-01

    Cobalt-doping of Bi2Sr2CaCu2Ox beyond a critical level of 1.5-1.7 at % produces both a large decrease in the superconducting transition critical temperature and all of the classic symptoms of Anderson localization. These include: a negative slope of the ab-plane resistivity vs temperature, no dispersing states near the Fermi level and a decrease of the photoemission signal in the same region.

  6. Superconducting properties of Tl-Ba-Ca-Cu-O films on silver substrates

    Energy Technology Data Exchange (ETDEWEB)

    Dye, R.C.; Arendt, P.N.; Martin, J.A.; Hubbard, K.M.; Elliott, N.; Reeves, G. (Los Alamos National Lab., NM (United States))

    1991-03-01

    Films of Ba-Ca-Cu-O have been rf magnetron sputtered onto Consil 995 substrates. A post deposition anneal in an over pressure of Tl produces the superconducting 1212 and 2212 phases. Varying the annealing procedures changes the electrical properties of the final films dramatically. Dynamic impedance, an approach to the electrical characterization of these films on a conductive substrate is discussed and compared in this paper, with SEM, XRD and RBS measurements as a function of differing annealing protocols.

  7. Superconducting properties of Tl-Ba-Ca-Cu-O films on silver substrates

    Energy Technology Data Exchange (ETDEWEB)

    Dye, R.C.; Arendt, P.N.; Martin, J.A.; Hubbard, K.M.; Elliott, N.; Reeves, G.

    1990-01-01

    Films of Ba-Ca-Cu-O have been rf magnetron sputtered onto Consil 995 substrates. A post deposition anneal in an over pressure of Tl produces the superconducting 1212 and 2212 phases. Varying the annealing procedures changes the electrical properties of the final films dramatically. Dynamic impedance, a novel approach to the electrical characterization of these films on a conductive substrate is discussed and compared with SEM, XRD and RBS measurements as a function of differing annealing protocols. 3 refs., 9 figs.

  8. Investigation of agglomerated Cu seed on Cu oxidation after chemical mechanical planarization

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Jeng-Yu, E-mail: jylin@ttu.edu.tw [Department of Chemical Engineering, Tatung University, Taipei 104, Taiwan (China); Chou, Shu-Wei [Department of Chemical Engineering, Tatung University, Taipei 104, Taiwan (China); Cheng, Min-Yuan [TSMC, No. 8, Li-Hsin Rd. 6, Science-Based Industrial Park, Hsinchu 300-77, Taiwan (China)

    2010-11-01

    After chemical mechanical planarization (CMP), the reason which caused the formation of Cu-oxide defects at the interface between Cu deposit and TaN barrier layer has been studied. The experimental results of atomic force microscopy, secondary ion mass spectroscopy, X-ray diffraction demonstrated that the agglomeration phenomenon was found on Cu seed in the thickness of only 10 nm, thus resulting in the electrodeposited Cu film with more abundant C impurities at Cu/TaN interface and lower (1 1 1)/(2 0 0) ratio compared to the thick one (30 nm). Therefore it caused the Cu deposit with poor corrosion resistance and then the Cu-oxide defects were easily formed after CMP. As a result, the correlation between Cu-oxide defects at the Cu/TaN interface and the agglomeration on Cu seed layer was proposed herein.

  9. Magnetocaloric Evidence for FFLO Superconductivity in κ-(BEDT-TTF)2Cu(NCS)2

    Science.gov (United States)

    Fortune, Nathanael; Agosta, Charles; Hannahs, Scott; Park, Ju-Hyun; Gu, Shuyao; Liang, Lucy; Schleuter, John

    We present new magnetocaloric and calorimetric measurements of the high field superconducting state in the layered structure superconductor κ - (BEDT-TTF)2Cu(NCS)2. The strongly field-orientation dependent phase transition between the low field superconducting state and high field superconducting states is first order and is nearly temperature independent, occurring at the Clogston-Chandrasakar paramagnetic limit Hp. Magnetocaloric measurements dT / dH as a function of magnetic field reveal that the system becomes strongly paramagnetic at the cross over from the low field to high field state. At lower temperatures, we are able to resolve small changes at the phase boundary due to the absorption/release of latent heat when increasing/decreasing field, indicating that the high field state is higher entropy than the low field state. These results provide strong new evidence for the formation of paramagnetic spin domains within an inhomogeneous FFLO superconducting state. They also allow us to rule out alternative explanations involving the formation of spin density waves within a homogenous superconducting state. A portion of this work was performed at the National High Magnetic Field Laboratory, which is supported by National Science Foundation Cooperative Agreement No. DMR-1157490 and the State of Florida.

  10. Understanding the superconductivity in copper oxides

    CERN Document Server

    2016-01-01

    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...

  11. Observation and identification of a 107 K superconducting family in the CaBa 2Ca 2Cu 3O 9- δ system

    Science.gov (United States)

    Wu, N. L.; Du, Z. L.; Xue, Y. Y.; Rusakova, I.; Ross, D. K.; Gao, L.; Cao, Y.; Sun, Y. Y.; Chu, C. W.; Hervieu, M.; Raveau, B.

    1999-04-01

    A new family of C-free high-temperature superconducting oxides in the Ba-Ca-Cu-O system showing a Tc up to 107 K has been synthesized under high pressure. Structural analyses, based on X-ray and electron diffractions and high resolution electron microscopy, have revealed that these oxides can be represented by CaBa 2Ca 2Cu 3O 9- δ [Ca-1223-Ba] with a tetragonal subcell that has lattice constants a∼3.85 Å and c∼16.5 Å and is isostructural to Tl-1223-Ba with the Tl sites occupied mainly by Ca. These oxides have the same active block of [(CuO 2)(Ca)(CuO 2)(Ca)(CuO 2)] but with cation mixing and substitution of Ca by Cu within the charge reservoir block [(BaO)(CaO)(BaO)]. This results in the observed variations in composition and superstructure but has only minor influence on Tc.

  12. High Temperature Superconductivity in Praseodymium Doped (0%, 2%, 4%) in Melt-Textured Y(1-x)Pr(x)Ba2Cu3O(7-delta) Systems

    Science.gov (United States)

    James, Claudell

    1995-01-01

    A study of the magnetic and structural properties of the alloy Y(1-x)Pr(x)Ba2Cu3O(7-delta) of 0%, 2%, and 4% doping of praseodymium is presented. The resulting oxides of the alloy series are a high-temperature superconductor Y-Ba-Cu-O, which has an orthorhombic superconducting crystal-lattice. Magnetic relaxation studies have been performed on the Y-Pr-Ba-CuO bulk samples for field orientation parallel to the c-axis, using a vibrating sample magnetometer. Relaxation was measured at several temperatures to obtain the irreversible magnetization curves used for the Bean model. Magnetization current densities were derived from the relaxation data. Field and temperature dependence of the logarithmic flux-creep relaxation was measured in critical state. The data indicates that the effective activation energy U(eff) increases with increasing T between 77 K and 86 K. Also, the data shows that U(eff)(T) and superconducting transition temperature, Tc, decreased as the lattice parameters increased with increasing Pr ion concentration, x, for the corresponding Y(1-x)Pr(x)Ba(x)Cu3O(7-delta) oxides. One contribution to Tc decrease in this sampling is suspected to be due to the larger ionic radius of the Pr(3+) ion. The upper critical field (H(sub c2)) was measured in the presence of magnetic field parallel to the c axis. A linear temperature dependence with H(sub c2) was obtained.

  13. Physical properties of the superconducting spin-valve Fe/Cu/Fe/In heterostructure

    Science.gov (United States)

    Leksin, P. V.; Garif'yanov, N. N.; Garifullin, I. A.; Schumann, J.; Kataev, V.; Schmidt, O. G.; Büchner, B.

    2012-01-01

    We report on structural, magnetic, and superconducting properties of the spin-valve multilayer system CoOx/Fe1/Cu/Fe2/In. For most of the thicknesses of the second iron layer dFe2 up to 2 nm, we have observed a full spin-valve effect for the superconducting current, i.e., a complete transition from the normal to the superconducting state by changing the mutual orientation of the magnetizations of the Fe1 and Fe2 layers. For dFe2<1 nm, the superconducting transition temperature TcP for the parallel orientation of magnetizations of the Fe1 and Fe2 layers is smaller than that for the antiparallel orientation TcAP, which corresponds to the direct spin-valve effect. For dFe2⩾1 nm, we have found the inverse spin-valve effect with ΔTc=TcAP-TcP<0. Further, in samples with a fixed thickness of the In layer, we have observed an oscillating dependence of its superconducting transition temperature Tc on dFe2. The analysis of the Tc(dFe2) dependence using the theory of the superconducting-ferromagnetic proximity effect has enabled determination of all microscopic parameters of the studied system. With these parameters, a satisfactory description of the sign-changing oscillating behavior of the spin-valve effect ΔTc(dFe2) has been obtained using a recent theory by Fominov [Ya. V. Fominov , Pis'ma Zh. Eksp. Teor. Fiz. 91, 329 (2010) [JETP Lett.JTPLA20021-364010.1134/S002136401006010X 91, 308 (2010)

  14. Evidence for two coupled subsystems in the superconducting state of La2-xSrxCuO4

    Science.gov (United States)

    Rast, S.; Schneider, M. L.; Onellion, M.; Zeng, X. H.; Si, Weidong; Xi, X. X.; Abrecht, M.; Ariosa, D.; Pavuna, D.; Ren, Y. H.; Lüpke, G.; Perakis, I.

    2001-12-01

    We used a pump-probe technique to measure the transient change of optical reflectivity of both La2-xSrxCuO4, of various dopings, and slightly underdoped YBa2Cu3O7-x and NdBa2Cu3O7-x thin films. For the La2-xSrxCuO4 films, our data demonstrate the coexistence, in the superconducting state, of two coupled subsystems with different relaxation times and different contributions to the optical reflectivity. One subsystem is associated with the superconducting phase. By contrast, the data from YBa2Cu3O7-x and NdBa2Cu3O7-x shows that the coupling between the two subsystems is weak or absent.

  15. Crystal structure, magnetic susceptibility and thermopower of superconducting and non-superconducting Nd1.85Ce0.15CuO4+#upsilone#

    DEFF Research Database (Denmark)

    Mangelschots, I.; Andersen, N.H.; Lebech, B.

    1992-01-01

    An experimental study of superconducting and non-superconducting Nd1.85Ce0.15CuO4+y, including structure determination by neutron powder diffraction, recording of oxygen changes by gas volumetry, and susceptibility and thermoelectric measurements, is reported. Difference neutron diffraction...... from the superconducting to the non-superconducting state. Structural refinements confirm that Nd1.85Ce0.15CuO4+y has the T'-type tetragonal structure reported in the literature, but additional oxygen may be located on the apical O(3) oxygen site of the T-type structure, with a total oxygen content...... of 4 + y = 4.03(5). Consistent with this result, we find very small values of the thermoelectric power indicating that Nd1.85Ce0.15CuO4+y is Close to the formal threshold, y(c) = 0.075, between electron and hole conduction, but surprisingly, the thermoelectric power of the superconducting sample...

  16. 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).

  17. Visualizing short-range charge transfer at the interfaces between ferromagnetic and superconducting oxides.

    Science.gov (United States)

    Chien, Te Yu; Kourkoutis, Lena F; Chakhalian, Jak; Gray, Benjamin; Kareev, Michael; Guisinger, Nathan P; Muller, David A; Freeland, John W

    2013-01-01

    The interplay between antagonistic superconductivity and ferromagnetism has been a interesting playground to explore the interaction between competing ground states. Although this effect in systems of conventional superconductors is better understood, the framework of the proximity effect at complex-oxide-based superconductor/ferromagnet interfaces is not so clear. The main difficulty originates from the lack of experimental tools capable of probing the interfaces directly with high spatial resolution. Here we harness cross-sectional scanning tunnelling microscopy and spectroscopy together with atomic-resolution electron microscopy to understand the buried interfaces between cuprate and manganite layers. The results show that the fundamental length scale of the electronic evolution between YBa2Cu3O(7-δ) (YBCO) and La2/3Ca1/3MnO3 (LCMO) is confined to the subnanometre range. Our findings provide a complete and direct microscopic picture of the electronic transition across the YBCO/LCMO interfaces, which is an important step towards understanding the competition between ferromagnetism and superconductivity in complex-oxide heterostructures.

  18. Cation disorder and gas phase equilibrium in an YBa 2Cu 3O 7- x superconducting thin film

    Science.gov (United States)

    Shin, Dong Chan; Ki Park, Yong; Park, Jong-Chul; Kang, Suk-Joong L.; Yong Yoon, Duk

    1997-02-01

    YBa 2Cu 3O 7- x superconducting thin films have been grown by in situ off-axis rf sputtering with varying oxygen pressure, Ba/Y ratio in a target, and deposition temperature. With decreasing oxygen pressure, increasing Ba/Y ratio, increasing deposition temperature, the critical temperature of the thin films decreased and the c-axis length increased. The property change of films with the variation of deposition variables has been explained by a gas phase equilibrium of the oxidation reaction of Ba and Y. Applying Le Chatelier's principle to the oxidation reaction, we were able to predict the relation of deposition variables and the resultant properties of thin films; the prediction was in good agreement with the experimental results. From the relation between the three deposition variables and gas phase equilibrium, a 3-dimensional processing diagram was introduced. This diagram has shown that the optimum deposition condition of YBa 2Cu 3O 7- x thin films is not a fixed point but can be varied. The gas phase equilibrium can also be applied to the explanation of previous results that good quality films were obtained at low deposition temperature using active species, such as O, O 3, and O 2+.

  19. Evidence for spin-triplet superconducting correlations in metal-oxide heterostructures with noncollinear magnetization

    Science.gov (United States)

    Khaydukov, Yu. N.; Ovsyannikov, G. A.; Sheyerman, A. E.; Constantinian, K. Y.; Mustafa, L.; Keller, T.; Uribe-Laverde, M. A.; Kislinskii, Yu. V.; Shadrin, A. V.; Kalaboukhov, A.; Keimer, B.; Winkler, D.

    2014-07-01

    Heterostructures composed of ferromagnetic La0.7Sr0.3MnO3, ferromagnetic SrRuO3, and superconducting YBa2Cu3O6+x were studied experimentally. Structures of composition Au /La0.7Sr0.3MnO3/SrRuO3/YBa2Cu3O6+x were prepared by pulsed laser deposition, and their high quality was confirmed by x-ray diffraction and reflectometry. A noncollinear magnetic state of the heterostructures was revealed by means of superconducting quantum interference device magnetometry and polarized neutron reflectometry. We have further observed superconducting currents in mesa structures fabricated by deposition of a second superconducting Nb layer on top of the heterostructure, followed by patterning with photolithography and ion-beam etching. Josephson effects observed in these mesa structures can be explained by the penetration of a triplet component of the superconducting order parameter into the magnetic layers.

  20. Formation and Oxidation Behavior of Al-Cu-Fe Quasicrystal

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Al62.5Cu25Fe12.5 alloy was prepared by arc melting. It was found that the formation of quasicrystalline phase is related to the condition of annealing, such as temperature and duration. Weight gain of Al-Cu-Fe quasicrystal during the oxidation at 700 and 800 C in dry air was measured by means of thermal balance. The oxidation kinetics showed that the quasicrystal has good oxidation resistance. Only α-Al2O3 was formed on Al62.5Cu25Fe12.5 quasicrystal. The surface morphologies of Al-Cu-Fe quasicrystal after isothermal oxidation for different times were observed.

  1. The role of Cu-O bond length fluctuations in the high temperature superconductivity mechanism

    Science.gov (United States)

    Deutscher, Guy

    2012-06-01

    We review three different kinds of experiments that emphasize the non-BCS, inhomogeneous aspects of superconductivity in the high Tc cuprates. The first is the existence of two different energy scales in the superconducting state, initially identified by a comparison between tunneling and Andreev-Saint-James spectroscopies [Deutscher, Nature (London) 397, 410 (1999)]. The second are EXAFS measurements of the Cu-O bond length distribution, which have shown that below a temperature T* > Tc, it becomes broader than expected from the Debye-Waller broadening and presents a split [Bianconi et al., Phys. Rev. Lett. 76, 3412 (1996)]. The third one is the effect of frozen lattice disorder on critical current and vortex pinning, which profoundly affects the pairing landscape [Gutierrez et al., Nature Mater. 6, 367 (2007)]. We then discuss how these results fit with models in which the electron-lattice interaction plays a leading role.

  2. Evolving Picture of Striped Superconductivity in La2-xBaxCuO4

    Science.gov (United States)

    Tranquada, John; Gu, Genda; Homes, Chris; Huecker, Markus; Li, Qiang; Wen, Jinsheng; Xu, Guangyong; Xu, Zhijun

    2010-03-01

    We have previously presented experimental evidence for two-dimensional superconductivity in La1.875Ba0.125CuO4 coexisting with charge and spin stripe order for T < 40 K. A pair-density-wave (PDW) state has been proposed to explain the dynamical layer decoupling; however, recent photoemission measurements indicate that a d-wave gap develops on the nodal arc in the same temperature range. We show that our various experimental results are consistent with the onset of PDW correlations together with the charge-stripe order at 53 K, followed by the development of uniform d-wave superconductivity. We can rule out layer decoupling due to a charge-density-wave gap.

  3. Discovery of Superconductivity in κ-(BEDT-TTF)_2Cu[N(CN)_2]I

    Science.gov (United States)

    Lee, H. S.; Cowan, D. O.; Fainchtein, R.; Bohandy, J.; Geiser, U.; Wang, H. H.; Schlueter, J. A.; Kushch, N. D.; Flynn, J. P.; Vanzile, M. L.; Williams, J. M.

    1996-03-01

    Evidence of superconductivity with a mid-point transition temperature of 7.2K was found for the first time on crystals of κ-(BEDT-TTF)_2Cu[N(CN)_2]I. The crystals were first synthesized at Johns Hopkins University and later independently synthesized at Argonne National Laboratory. The structure of the materials has been confirmed to be of the kappa-phase moiety by STM, AFM, Raman, ESR and X-ray diffraction. Superconductivity of the samples was confirmed by dc-conductivity, modulated microwave reflectance and magnetic susceptibility with a transition onset of 7.5K. (Authors HSL, DOC and RF acknowledge support by NSF under grant No. DMR-9223481; authors affiliated with ANL acknowledge support by DOE under contract No. W-31-109-ENG-38.)

  4. Resistive evaporation of superconducting Y-Ba-Cu-O thin films from a single source

    Energy Technology Data Exchange (ETDEWEB)

    Azoulay, J.; Goldschmidt, D.

    1989-06-12

    A new evaporation method of high-temperature superconducting films, the /ital resistive vaporation/ /ital from/ /ital single/ /ital source/, isreported here for the first time. The source material, inserted into a tungstenboat in a conventional vacuum system, consisted of a pulverized mixture of Cu,YF/sub 3/, and BaF/sub 2/. The handling of the source material required only grindingand mixing of the raw materials. Its deposition onto SrTiO/sub 3/ substratesyielding superconducting films with properties very similar to those obtained ina layer-by-layer resistive evaporation of these materials. In particular, aresistive transition onset at 75 K and zero resistance at /similar to/40 K, and criticalcurrents of 2000 A/cm/sup 2/ at approx.10 K have been measured. The broad transition maybe attributed to a copper concentration gradient, as measured by Auger depthprofiling, or to a residual fluorine-rich phase.

  5. Preparation of uniform mixed metal oxide and superconductive oxides

    Energy Technology Data Exchange (ETDEWEB)

    Barder, T.J.

    1991-04-30

    This paper describes a method for producing a uniform mixed metal oxide. It includes dissolving metals as their salts of a carboxylic acid in an aliphatic alcohol in the substantial absence of water, the metals are in the same proportions as in the corresponding mixed metal oxide; co-precipitating the metals as their oxalates by mixing the alcohol solution with oxalic acid; separating the co-precipitated metal oxalates and calcining the oxalates in air or oxygen above about 500{degrees} C to convert the oxalates to the corresponding metal oxides.

  6. A superconducting conveyer system using multiple bulk Y-Ba-Cu-O superconductors and permanent magnets

    Science.gov (United States)

    Kinoshita, T.; Koshizuka, N.; Nagashima, K.; Murakami, M.

    Developments of non-contact superconducting devices like superconducting magnetic levitation transfer and superconducting flywheel energy storage system have been performed based on the interactions between bulk Y-Ba-Cu-O superconductors and permanent magnets, in that the superconductors can stably be levitated without any active control. The performances of noncontact superconducting devices are dependent on the interaction forces like attractive forces and stiffness. In the present study, we constructed a non-contact conveyer for which the guide rails were prepared by attaching many Fe-Nd-B magnets onto an iron base plate. Along the translational direction, all the magnets were arranged as to face the same pole, and furthermore their inter-distance was made as small as possible. The guide rail has three magnet rows, for which the magnets were glued on the iron plate such that adjacent magnet rows have opposite poles like NSN. At the center row, the magnetic field at zero gap reached 0.61T, while the field strengths of two rows on the side edges were only 0.48T due to magnetic interactions among permanent magnets. We then prepared a cryogenic box made with FRP that can store several bulk Y-Ba-Cu-O superconductors 25 mm in diameter cooled by liquid nitrogen. It was found that the levitation forces and stiffness increased with increasing the number of bulk superconductors installed in the box, although the levitation force per unit bulk were almost the same. We also confirmed that these forces are dependent on the configuration of bulk superconductors.

  7. Superconductivity

    Science.gov (United States)

    1989-07-01

    SUPERCONDUCTIVITY HIGH-POWER APPLICATIONS Electric power generation/transmission Energy storage Acoustic projectors Weapon launchers Catapult Ship propulsion • • • Stabilized...temperature superconductive shields could be substantially enhanced by use of high-Tc materials. 27 28 NRAC SUPERCONDUCTIVITY SHIP PROPULSION APPLICATIONS...motor shown in the photograph. As a next step in the evolution of electric-drive ship propulsion technology, DTRC has proposed to scale up the design

  8. Undoped high-Tc superconductivity in T'-La1.8Eu0.2CuO4+δ revealed by 63,65Cu and 139La NMR: Bulk superconductivity and antiferromagnetic fluctuations

    Science.gov (United States)

    Fukazawa, Hideto; Ishiyama, Seiya; Goto, Masato; Kanamaru, Shuhei; Ohashi, Kohki; Kawamata, Takayuki; Adachi, Tadashi; Hirata, Michihiro; Sasaki, Takahiko; Koike, Yoji; Kohori, Yoh

    2017-10-01

    We performed 63,65Cu and 139La NMR measurements of T'-La1.8Eu0.2CuO4+δ (T'-LECO) with the Nd2CuO4-type structure (so-called T'-structure). As a result, we detected the 63,65Cu NMR signal under finite magnetic fields and found superconductivity without antiferromagnetic (AF) order only in the reduced T'-LECO, where excess apical oxygen atoms are properly removed. This indicates that the intrinsic ground state of the ideal T'-LECO is a paramagnetic and superconducting (SC) state. Below Tc, the Knight shift was found to rapidly decrease, which indicates the emergence of bulk superconductivity due to spin-singlet Cooper pairs in the reduced T'-LECO. In the SC state of the reduced T'-LECO, moreover, a characteristic temperature dependence of the spin-lattice relaxation rate 1/T1 was observed, which implies the existence of nodal lines in the SC gap. These findings suggest that the superconductivity in the reduced T'-LECO probably has d-wave symmetry. In the normal state of the reduced T'-LECO, on the other hand, AF fluctuations were found to exist from the temperature dependence of 1/T1T, though no clear pseudogap behavior was observed. This suggests that the AF correlation plays a key role in the superconductivity of undoped high-Tc cuprate superconductors with the T'-structure.

  9. Research on Y-Ba-Cu-O superconducting thin films at liquid nitrogen temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Li Yuan; Yang Senzu; Ji Zhengming; Sun Zhijian; Jing Dong; Wu Peiheng; Zhang Shiyan; Wang Hao; Zhou Ningsheng; Fan Depei; and others

    1988-12-01

    The Y-Ba-Cu-O superconducting thin films on several kinds of substrates of single crystal ZrO/sub 2/, YSZ and polycrystalline SrTiO/sub 3/ have been successfully prepared by mean of /ital rf/ reactive magnetron sputtering. The zero resistance temperature obtained is 81 K. The thickness of the films is about 1--2 ..mu..m. In this paper the composition of the films, the substrates, /ital R/-/ital T/ curves, X-ray diffraction patterns and the heat treatment process of the films are described.

  10. New method for fabrication of superconducting pipes in the Bi-Sr-Ca-Cu-O system

    Science.gov (United States)

    Abe, Yoshihiro; Hosono, Hideo; Lee, Won-Hyuk; Hosoe, Masahiro; Nakamura, Koichi; Inukai, Eikichi

    1993-01-01

    Pipes or hollow cylinders in the Bi-Sr-Ca-Cu-O system were found to be fabricated easily by inspiring or sucking the low viscosity melt into a cold silica glass tube. The outer part of the cast rod-like melt solidified, and the inner hot low-viscosity part of the rod melt was expired. The precursor pipes were reheated at 800 C for 50 h in air, resulting in the formation of superconducting (Tc = 87 K) pipes which were of smooth surface without machining and high bending strength (100-150 MPa).

  11. Interstitial doping and oxygen exchange in superconducting La sub 2 CuO sub 4+. delta

    Energy Technology Data Exchange (ETDEWEB)

    Shinn, N.D.; Bartram, M.E.; Schirber, J.E.; Rogers, J.W. Jr.; Overmyer, D.L. (Sandia National Labs., Albuquerque, NM (USA)); Fisk, Z.; Cheong, S.W. (Los Alamos National Lab., NM (USA))

    1991-09-01

    The oxygen doping of lanthanum cuprate to generate superconductiving La{sub 2}CuO{sub 4+{delta}} (0<{delta}{<=}0.032) has been studied by high-pressure, isotopic-oxygen enrichment and thermal desorption mass spectroscopy (TDMS). Isotopic data show that the additional oxygen incorporated under high pressure readily exchanges with ionic lattice oxygen during enrichment at 860 K. The thermal release of the excess oxygen from superconducting crystals above {proportional to}350 K is not bulk diffusion limited. An alternate explanation for the observed rapid O{sub 2}(g) bursts is proposed. (orig.).

  12. Superconductivity in 2-2-3 system Y2Ba2Cu2O(8+delta)

    Science.gov (United States)

    Joshi, H. H.; Baldha, G. J.; Jotania, R. B.; Joshi, S. M.; Mohan, H.; Pandya, P. B.; Pandya, H. N.; Kulkarni, R. G.

    1991-01-01

    Researchers synthesized a new high T(sub c) 2-2-3 superconductor Y2Ba2Cu3O(8+delta) by a special preparation technique and characterized it by ac-susceptibility measurements. Diamagnetism and Meissner effect sets in at low fields and superconducting transition onsets at 90 K. The systematic investigation of the real and imaginary components of ac-susceptibility as a function of temperature and applied ac magnetic field reveals that the magnetic behavior is that of a granular type superconductor.

  13. Superconductivity of k-(BEDT-TTF) sub 2 Cu[N(CN) sub 2]I under pressure

    CERN Document Server

    Kushch, N D; Yagubskii, E B; Ishiguro, T

    2001-01-01

    The insulating state of k-(BEDT-TTF) sub 2 Cu[N(CN) sub 2]I salt appearing at ambient pressure at low temperatures is suppressed by hydrostatic pressure. The resistive measurement showed that in high-quality crystals the emerging metallic state reveals superconductivity. The superconducting state with the transition temperature of about 8 K is stable at pressures higher than 0.1 GPa

  14. Role of impurity oxygen in superconductivity of "non-doped" T'-(La,RE)2CuO4

    OpenAIRE

    Tsukada, A.; Noda, M; Yamamoto, H; Naito, M.

    2005-01-01

    We have systematically investigated the effect of oxygen nonstoichiometry in a nominally undoped superconductor T'-(La,Y)2CuO4+y. In the experiments, the reduction condition was changed after the sample growth by MBE. The superconductivity is very sensitive to the reduction condition. With systematically increasingly reduced atmospheres, resistivity shows a continuous drop and no discontinuity is observed even until the appearance of superconductivity. The absence of the highly insulating sta...

  15. Superconducting gap in Bi-Sr-Ca-Cu-O by high-resolution angle-resolved photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Olson, C.G.; Liu, R.; Yang, A.B.; Lynch, D.W. (Iowa State Univ., Ames (USA)); Arko, A.J.; List, R.S. (Los Alamos National Lab., NM (USA)); Veal, B.W.; Chang, Y.C.; Jiang, P.Z.; Paulikas, A.P. (Argonne National Lab., IL (USA))

    1989-08-18

    Detailed studies indicate a superconducting gap in the high-temperature superconductor Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8}. Photoemission measurements with high energy and angle resolution isolate the behavior of a single band as it crosses the Fermi level in both the normal and superconducting states, giving support to the Fermi liquid picture. The magnitude of the gap is 24 millielectron volts. 18 refs., 3 figs.

  16. Oxidation-stability studies of CuInSe2

    Science.gov (United States)

    Kazmerski, L. L.; Ireland, P. J.; Jamjoum, O.; Deb, S. K.; Sheldon, P.; Mickelsen, R. A.; Chen, W.; Bachmann, K.

    The oxidation of p-type single-crystal and thin-film polycrystalline CuInSe2 is investigated using complementary Auger electron spectroscopy (AES), secondary ion mass spectroscopy (SIMS) and X-ray photoelectron spectroscopy (XPS). The compositions of the thermally-grown oxides over the 150-300 C temperature range are found to be primarily In2O3, with some SeO2, estimated to be less than 10% by quantitative AES and XPS. The interface between the oxide and CuInSe2 is examined using AES and SIMS depth-compositional profiling in conjunction with XPS. Cu(x)Se is found to form at the interface. Angular-resolved XPS with an in-situ oxidation process is utilized to evaluate the initial oxidation of this Cu-ternary semiconductor. These studies confirm that Cu(x)Se forms during oxide growth.

  17. Initial oxidation of CuInSe2

    Science.gov (United States)

    Kazmerski, L. L.; Jamjoum, O.; Ireland, P. J.; Deb, S. K.; Mickelsen, R. A.; Chen, W.

    1981-10-01

    The oxidation of p-type single-crystal and thin-film polycrystalline CuInSe2 is investigated using complementary Auger electron spectroscopy (AES), secondary ion mass spectroscopy (SIMS) and X-ray photoelectron spectroscopy (XPS). The compositions of the thermally-grown oxides over the 150-300 C temperature range are found to be primarily In2O3, with some SeO2, estimated to be less than 10% by quantitative AES and XPS. The interface between the oxide and CuInSe2 is examined using AES and SIMS depth-compositional profiling in conjunction with XPS. Cu(x)Se is found to form at the interface. Angular-resolved XPS with an in situ oxidation process is utilized to evaluate the initial oxidation of this Cu-ternary semiconductor. These studies confirm that Cu(x)Se forms during oxide growth.

  18. Normal and superconducting properties in the Ca 1-xCd xLaBaCu 3O y system

    Science.gov (United States)

    Zhang, X.-J.; Wang, J.-S.; Xu, Z.-A.; Jiao, Z.-K.; Zhang, Q. R.

    1994-11-01

    The superconducting behavior of the superconductor CaLaBaCu 3O y (CLBCO) has been studied as a function of substitution of Cd for Ca. Electrical resistivity measurements show that the superconducting critical temperature ( Tc) decreases monotonously with increasing substituent Cd concentration x. Within the composition range O⩽ x⩽1, the samples remain in single phase. Thermogravimetry (TG) studies of the samples show that the oxygen content greatly influences the normal and superconducting properties of the Ca 1- xCd xLaBaCu 3O y system. The substitution of Cd for Ca leads to deficiencies of oxygen in Cu-O chain. As the substituent Cd concentration x increases, the oxygen content decreases monotonously. It is concluded that the reason why Cd leads to the suppression of Tc is the reduction of oxygen content caused by substitution of Cd for Ca.

  19. Two-Dimensional Superconducting Fluctuations in Stripe-Ordered La2-xBaxCuO4

    Science.gov (United States)

    Li, Qiang; Hucker, Markus; Gu, Genda; Tsvelik, Alexei; Tranquada, John

    2008-03-01

    Recent spectroscopic observations of a d-wave-like gap in stripe-ordered La2-xBaxCuO4 with x=1/8 have led us to critically analyze the anisotropic transport and magnetization properties of this material. The data suggest that concomitant with the spin ordering is an electronic decoupling of the CuO2 planes. We observe a transition (or crossover) to a state of two-dimensional (2D) fluctuating superconductivity. Thus, it appears that the stripe order in La2-xBaxCuO4 frustrates three-dimensional superconducting phase order, but is fully compatible with 2D superconductivity and an enhanced Tc --[Ref. Q. Li, et al., PRL 99, 067001 (2007)

  20. 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...

  1. Superconducting transition in ruthenocuprate RuSr2GdCu2O8 viewed from the studies of the imaginary part of ac susceptibility

    Science.gov (United States)

    Zivkovic, I.; Drobac, D.; Ariosa, D.; Berger, H.; Pavuna, D.; Prester, M.

    2002-12-01

    We have measured two structurally similar superconducting systems, RuSr2GdCu2O8 and GdBa2Cu3O7 by means of high-resolution ac susceptibility. The real and the imaginary part of ac susceptibility of both bulk-ceramic and powdered samples have been studied down to the very small magnetic-field levels. We show that there are significant differences in the evolution of superconductivity in the two studied superconducting systems. In particular, we show that the superconducting transition in the grains in RuSr2GdCu2O8 system is masked with intrinsic magnetism of complex origin.

  2. Localized electronic states and the superconducting gap in Bi 2Sr 2CaCu 2O 8+y

    Science.gov (United States)

    Quitmann, C.; Ma, Jian; Kelley, R. J.; Margaritondo, G.; Onellion, M.

    1994-12-01

    Angle-resolved photoemission data taken on some Bi 2Sr 2CaCu 2O 8+y single crystals exhibit the formation of a superconducting gap in the absence of a quasiparticle normal state band. We observe the opening of the superconducting gap in the same regions of the Brillouin zone for which it is observed for samples that do exhibit a quasiparticle normal state. The absence of a dispersing quasiparticle normal state indicates that the normal state electronic states in these samples are almost localized in real space. Our data suggest that two types of carriers can coexist, and contribute to forming a superconducting gap, in these materials.

  3. Magnetic impurity induced states in superconducting Bi2Sr2CaCuO8+δ

    Science.gov (United States)

    Choubey, Peayush; Kreisel, Andreas; Berlijn, Tom; Andersen, Brian; Hirschfeld, Peter

    2015-03-01

    We revisit the Ni impurity problem in superconducting Bi2Sr2CaCu2O8+δ (BSCCO-2212) using the Bogoliubov- de Gennes (BdG)-Wannier approach. We solve the self-consistent BdG equations on a square lattice and use first principle-based Wannier function to compute the local density of states (LDOS) with sub-atomic resolution in the vicinity of a magnetic impurity. We find two spin-resolved virtual bound states localized around the impurity position. The spatial LDOS patterns at the resonance energies are found to be in excellent agreement with STM experiment, and can be understood by accounting for the tails of Cu Wannier function.

  4. NQR study of pressure induced superconductivity in CeCu{sub 2}Si{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Fujiwara, K.; Okazaki, Y.; Hata, Y.; Miyoshi, K.; Takeuchi, J. [Department of Materials Science, Shimane University, Matsue 690-8504 (Japan); Kobayashi, T.C. [Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530 (Japan); Geibel, C.; Steglich, F. [Max Planck Institute for Chemical Physics of Solids, Nothnitzer Strase 40, 01187 Dresden (Germany)

    2010-03-15

    We have measured nuclear quadrupole resonance (NQR) for {sup 63}Cu nuclei under high pressure up to 4.8 GPa. A linear increase in NQR frequency {sup 63} {nu}{sub Q} of {sup 63}Cu nuclei was observed below 3 GPa. However, {sup 63} {nu}{sub Q} deviates gradually from the linear relation above 3.5 GPa. The downward deviation is associated with a change of valence and consistent with the results of band calculations with the structural parameters under pressure. Antiferromagnetic (AFM) spin fluctuations are drastically suppressed with increasing pressure, whereas T{sub c} increases from 0.7 K at ambient pressure to 1.64 K at 4.2 GPa. We have found that bulk superconductivity suddenly disappears at 4.8 GPa accompanied with a rapid decrease in the density of states at the Fermi level. These are indenter pressure cells for NQR measurements. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  5. Electric field effect on superconductivity in La2-xSrxCuO4

    Science.gov (United States)

    Dubuis, G.; Bollinger, A. T.; Pavuna, D.; Božović, I.

    2012-06-01

    We demonstrate a method to tune the carrier concentration of a high temperature superconductor over a wide range, using an applied electric field. Thin film devices were made in an electrical double layer transistor configuration utilizing an ionic liquid. In this way, the surface carrier density in La2-xSrxCuO4 films can be varied between 0.01 and 0.14 carriers per Cu atom with a resulting change in critical temperature of 25 K (˜70% of the maximum critical temperature in this compound). This allows one to study a large segment of the cuprate phase diagram without altering the level of disorder. We used this method [A. T. Bollinger et al., Nature 472, 458-460 (2011)] to study the quantum critical point at the superconductor to insulator phase transition on the underdoped side of superconducting dome, and concluded that this transition is driven by quantum phase fluctuations and Cooper pair delocalization.

  6. Electric field effect on superconductivity in La2−xSrxCuO4

    Energy Technology Data Exchange (ETDEWEB)

    Dubuis, G.; Bollinger, A. T.; Pavuna, D.; Božović, I.

    2012-01-01

    We demonstrate a method to tune the carrier concentration of a high temperature superconductor over a wide range, using an applied electric field. Thin film devices were made in an electrical double layer transistor configuration utilizing an ionic liquid. In this way, the surfacecarrier density in La2-x Sr x CuO4 films can be varied between 0.01 and 0.14 carriers per Cu atom with a resulting change in critical temperature of 25 K (~70% of the maximum critical temperature in this compound). This allows one to study a large segment of the cuprate phase diagram without altering the level of disorder. We used this method [A. T. Bollinger et al., Nature 472, 458–460 (2011)] to study the quantum critical point at the superconductor to insulator phase transition on the underdoped side of superconducting dome, and concluded that this transition is driven by quantum phase fluctuations and Cooper pair delocalization.

  7. Trapped magnetic field of a superconducting bulk magnet in high- T sub c RE-Ba-Cu-O

    CERN Document Server

    Fujimoto, H; Higuchi, T; Nakamura, Y; Kamijo, H; Nagashima, K; Murakami, M

    1999-01-01

    Superconducting magnets made of high-T sub c superconductors are promising for industrial applications. It is well known that REBa sub 2 Cu sub 3 O sub 7 sub - sub x and LRE (light rare-earth) Ba sub 2 Cu sub 3 O sub 7 sub - sub x superconductors prepared by melt processes have a high critical current density, J sub 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 sub c in high magnetic fields and a much improved irreversibility field, H sub i sub r sub r , 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.

  8. Trapped magnetic field of a superconducting bulk magnet in high- T{sub c} RE-Ba-Cu-O

    Energy Technology Data Exchange (ETDEWEB)

    Fujimoto, Hiroyuki; Yoo, Sang Im; Higuchi, Takamitsu; Nakamura, Yuichi; Kamijo, Hiroki; Nagashima, Ken [Railway Technical Research Institute, Tokyo (Japan); Murakami, Masato [International Superconductivity Technology Center, Tokyo (Japan)

    1999-07-01

    Superconducting magnets made of high-T{sub c} superconductors are promising for industrial applications. It is well known that REBa{sub 2}Cu{sub 3}O{sub 7-x} and LRE (light rare-earth) Ba{sub 2}Cu{sub 3}O{sub 7-x} superconductors prepared by melt processes have a high critical current density, J{sub 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{sub c} in high magnetic fields and a much improved irreversibility field, H{sub 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.

  9. Structural properties of strained YBa2Cu3O6+x superconducting films grown by pulsed laser deposition

    Science.gov (United States)

    Ariosa, Daniel; Abrecht, M.; Pavuna, Davor; Onellion, Marshall

    2000-09-01

    In YBa2Cu3O6+x compound the tetragonal to orthorhombic transition occurs around x equals 0.3, followed by a continuum variation of lattice parameters. Hence both, the structural and superconducting properties, depend upon the oxygen content in CuO chains. Conversely, the epitaxial stress, exerted by the substrate on YBCO films, modified the lattice parameters influencing the oxygen stability in the chains. The understanding of this mechanism is essential when growing epitaxial films for in- situ photoemission studies as well as for tunneling experiments, since the oxygen stability up to the top surface unit-cell is a central issue. We have studied this effect on c-axis oriented YBCO films grown by laser ablation on (001) STO single crystals. Accurate x-ray diffraction analysis of thick films (t GRT 500 angstrom) indicates the presence of two distinct layers, one strained and the other relaxed. Detailed analysis shows that the relaxed layer is as well oxidized as bulk samples, while the strained one is oxygen deficient. Furthermore, despite an oxygen content of about x equals 0.65, the strained layer is in the tetragonal phase (in bulk, the tetragonal phase exists for x < 0.3). We discuss these results in terms of competition between the chemical pressure induced by oxygen inclusion in the chains, and the uniaxial stress within the film.

  10. Effect of shock pressure on the structure and superconducting properties of Y-Ba-Cu-O in explosively fabricated bulk metal-matrix composites

    Science.gov (United States)

    Murr, L. E.; Niou, C. S.; Pradhan-Advani, M.

    1991-01-01

    While it is now well established that copper-oxide-based power, or virtually any other ceramic superconductor powder, can be consolidated and encapsulated within a metal matrix by explosive consolidation, the erratic superconductivity following fabrication has posed a major problem for bulk applications. The nature of this behavior was found to arise from microstructural damage created in the shock wave front, and the residual degradation in superconductivity was demonstrated to be directly related to the peak shock pressure. The explosively fabricated or shock loaded YBa2Cu3Ox examples exhibit drastically altered rho (or R) - T curves. The deterioration in superconductivity is even more noticeable in the measurement of ac magnetic susceptibility and flux exclusion or shielding fraction which is also reduced in proportion to increasing peak shock pressure. The high frequency surface resistance (in the GHz range) is also correspondingly compromised in explosively fabricated, bulk metal-matrix composites based on YBa2Cu3O7. Transmission electron microscopy (including lattice imaging techniques) is being applied in an effort to elucidate the fundamental (microstructural) nature of the shock-induced degradation of superconductivity and normal state conductivity. One focus of TEM observations has assumed that oxygen displaced from b-chains rather than oxygen-vacancy disorder in the basal plane of oxygen deficient YBa2Cu3Ox may be a prime mechanism. Shock-wave displaced oxygen may also be locked into new positions or interstitial clusters or chemically bound to displaced metal (possibly copper) atoms to form precipitates, or such displacements may cause the equivalent of local lattice cell changes as a result of stoichiometric changes. While the shock-induced suppression of T(sub c) is not desirable in the explosive fabrication of bulk metal-matrix superconductors, it may be turned into an advantage if the atomic-scale distortion can be understood and controlled as local

  11. Mechanism of superconductivity in Yb sub 1 sub - sub x Ca sub x (Ba sub 0 sub . sub 8 Sr sub O sub . sub 2) sub 2 Cu sub 3 O sub 6 sub + subdelta

    CERN Document Server

    Anvekar, T S; Sarode, P R; Kamat-Dalal, V N; Narlikar, Anant V

    2002-01-01

    EXAFS, X-ray Rietveld refinement and infra-red absorption measurements have been made on Yb sub 1 sub - sub x Ca sub x (Ba sub 0 sub . sub 8 Sr sub 0 sub . sub 2) sub 2 Cu sub 3 O sub 6 sub + subdelta in order to understand the effect of Ca doping on the local structure of planar Cu ion. The study indicates that restoration of superconductivity is due to oxidation of copper ions in the CuO sub 2 planes. (author)

  12. The oxygen isotope effect on critical temperature in superconducting copper oxides

    OpenAIRE

    Mourachkine, A.

    2003-01-01

    The isotope effect provided a crucial key to the development of the BCS (Bardeen-Cooper-Schrieffer) microscopic theory of superconductivity for conventional superconductors. In superconducting cooper oxides (cuprates) showing an unconventional type of superconductivity, the oxygen isotope effect is very peculiar: the exponential coefficient strongly depends on doping level. No consensus has been reached so far on the origin of the isotope effect in the cuprates. Here we show that the oxygen i...

  13. Superconducting YBa sub 2 Cu sub 3 O sub 7 thin films grown in-situ by ion beam CO-deposition

    Energy Technology Data Exchange (ETDEWEB)

    Kellett, B.K.; James, J.H.; Gauzzi, A.; Dwir, B.; Pavuna, D. (Inst. of Micro and Optoelectronics, Dept. of Physics, Federal Inst. of Tech., Lausanne (Switzerland))

    1989-12-01

    Superconducting YBCO thin films have been grown in-situ by three ion beam co-deposition sputtering. Both metal and oxide targets of Cu and Y and BaF{sub 2} and BaCO{sub 3} targets have been investigated. Film composition was determined by RBS and AES analysis. Films grown using BaF{sub 2} show fluorine contamination, whereas the carbon concentration in films grown using BaCO{sub 3} is beneath the Auger detection limit. Superconducting films have been grown on SrTiO{sub 3} (T{sub co}=78K) and on Si with SiO{sub 2} or Y{sub 2}O{sub 3} buffer layers (T{sub co}=35K). (orig.).

  14. Direct Observation of Long-Term Durability of Superconductivity in YBa2Cu3O7-Ag2O Composites

    Science.gov (United States)

    Lin, Juhn-Jong; Lin, Yong-Han; Huang, Shiu-Ming; Lee, Tsang-Chou; Chen, Teng-Ming

    2003-10-01

    We report direct observation of long-term durability of superconductivity of several YBa2Cu3O7-Ag2O composites that were first prepared and studied almost fourteen years ago [J. J. Lin et al.: Jpn. J. Appl. Phys. 29 (1990) 497]. Remeasurements performed recently on both resistances and magnetizations indicate a sharp critical transition temperature at 91 K. We also find that such long-term environmental stability of high-temperature superconductivity can only be achieved in YBa2Cu3O7 with Ag2O addition, but not with pure Ag addition.

  15. X-ray Photoelectron Spectroscopy on Superconducting Tl2CaBa2Cu2O8 Thin Film

    Science.gov (United States)

    Zeng, Wensheng; Qiu, Ping; Yan, Shaolin; Li, Zengfa; Zhang, Guangyin

    1991-06-01

    We have prepared single-phase superconducting Tl2CaBa2Cu2O8 thin film by dc magnetron sputtering process and measured x-ray photoelectron spectra of the film at room and liquid nitrogen temperatures. From the relative intensities of the Ba3d, Tl4f. O1s and Cu2p spectra taken at different take-off angles, we have concluded that there is an adventitious contamination (nonsuperconducting phase) surface layer. After excluding contributions from these spurious phases, we have tentatively assigned which core-level shifts should be caused by the superconducting phase transition.

  16. NUMERICAL SIMULATION OF MECHANICAL BEHAVIORS OF SUPERCONDUCTING POWDER BSCCO (BiSrCaCuO)

    Institute of Scientific and Technical Information of China (English)

    ZHAO Yinghong; LEI Liping; ZENG Pan

    2007-01-01

    An equivalent continuum method and a deformable discrete method to describe the mechanical behaviors of superconducting powder BSCCO (BiSrCaCuO) aggregate are studied systematically. The equivalent continuum model idealizes the aggregation of the powder as an equivalent continuum material. The powder aggregate yielding is caused by not only the deviatoric stress but also the hydrostatic stress and the modified Drucker-Prager/Cap model is adopted to describe the mechanical behaviors of BSCCO powder aggregate in continuum method. The deformable discrete model is known as a direct model, which considers the discrete nature of the powder particles. Its framework encompasses the local behaviors between the particles, such as particles contact, sliding and rolling. Based on commercial finite element software ABAQUS, the equivalent continuum model and the deformable discrete model are used to simulate the confined compression of superconducting powder BSCCO, and the numerical results show agreement with experimental results, which verify the correctness of these built models. Compared with the equivalent continuum model based on macroscopic statistics method, the deformable discrete model can present the microscopic information during processing and can describe the nature of mechanical behaviors of superconducting powder BSCCO. But from an industrial viewpoint, the equivalent continuum model has a definitive edge over the microscopic models in that the gross behavior of the powder mass can be modeled and simulated on an industrial scale.

  17. Nitrogen oxides under pressure: stability, ionization, polymerization, and superconductivity.

    Science.gov (United States)

    Li, Dongxu; Oganov, Artem R; Dong, Xiao; Zhou, Xiang-Feng; Zhu, Qiang; Qian, Guangrui; Dong, Huafeng

    2015-11-17

    Nitrogen oxides are textbook class of molecular compounds, with extensive industrial applications. Nitrogen and oxygen are also among the most abundant elements in the universe. We explore the N-O system at 0 K and up to 500 GPa though ab initio evolutionary simulations. Results show that two phase transformations of stable molecular NO2 occur at 7 and 64 GPa, and followed by decomposition of NO2 at 91 GPa. All of the NO(+)NO3(-) structures are found to be metastable at T = 0 K, so experimentally reported ionic NO(+)NO3(-) is either metastable or stabilized by temperature. N2O5 becomes stable at 9 GPa, and transforms from P-1 to C2/c structure at 51 GPa. NO becomes thermodynamically stable at 198 GPa. This polymeric phase is superconducting (Tc = 2.0 K) and contains a -N-N- backbone.

  18. Controlled growth of ultrathin Mo2C superconducting crystals on liquid Cu surface

    Science.gov (United States)

    Geng, Dechao; Zhao, Xiaoxu; Li, Linjun; Song, Peng; Tian, Bingbing; Liu, Wei; Chen, Jianyi; Shi, Dong; Lin, Ming; Zhou, Wu; Loh, Kian Ping

    2017-03-01

    Exhibiting thickness-dependent change in the critical temperature (T c) for the onset of superconductivity, Mo2C has emerged as an important new member in the family of two-dimensional atomic crystals. Controllable growth in terms of morphology and thickness is necessary to elucidate its intrinsic properties at the 2D limit. Here we demonstrate the chemical vapor deposition of ultrathin Mo2C crystals on liquid Cu surface where the morphology of the crystals can be controlled by tuning the carbon supersaturation. A unique staggered carbon vacancy ordering is discovered in Mo2C crystals having particular geometries. Thickness engineering of the crystal can be achieved by controlling the thickness of the Cu catalyst layer, which affords a facile route to grow ultrathin 2D samples. Ultrathin Mo2C crystals so obtained, have been characterized using aberration corrected scanning transmission electron microscopy annular dark field imaging, where the co-existence of both AA and AB stacking modes is observed. The high crystallinity of the Mo2C crystals synthesized in this work is attested by its characteristic sharp superconducting transition.

  19. Observation of nonuniform current transport in epitaxial YBa{sub 2}Cu{sub 3}O{sub 7-x} film near the superconducting transition temperature

    Energy Technology Data Exchange (ETDEWEB)

    Wang, L.B.; Price, M.B.; Young, J.L.; Kwon, C.; Haugan, Timothy J.; Barnes, Paul N

    2004-06-15

    We have studied the local transport properties in an epitaxial YBa{sub 2}Cu{sub 3}O{sub 7-x} (YBCO) film on LaAlO{sub 3} (LAO) using variable temperature scanning laser microscope (VTSLM) near the superconducting transition. A map of the superconducting transition temperature (T{sub c}{sup *}) is generated from a series of VTSLM images. The map of T{sub c}{sup *} indicates there are inhomogeneities in the film large enough to create nonuniform current flow near the superconducting transition. The evaluated T{sub c}{sup *} varies between 90.3 and 91.0 K in the film. Even though such change in T{sub c}{sup *} is not large enough to be detected by other localized compositional and structural characterization techniques, this along with an area of lower T{sub c}{sup *} and/or higher resistance affects current flow near the superconducting transition temperature as shown in VTSLM images. This inhomogeneity may be caused by slight variations of the stoichiometry and/or oxidation of the YBCO film.

  20. Superconducting Hg-Based Mixed Oxides and Oxyfluorides

    Science.gov (United States)

    Antipov, E. V.

    2000-09-01

    Syntheses under high pressure and under controlled mercury and oxygen partial pressures of different members of the HgBa2Can-1CunO2n+2+δ series have been developed. There are two main parameters influencing Tc in this family: width of a perovskite slab (n) and concentration (δ) of the extra oxygen located in the Hg layer. The increase of Tc with n occurs until the third member, while after that it decreases. All the members of the series exhibit similar cupola shaped dependencies of Tc vs. δ. Strongly overdoped high members of the series with n = 3-5 were prepared only using high pressure technique and BaO2 as an internal oxidizer. Neutron powder diffraction experiments were carried out for monophase oxygenated HgBa2CuO4F4+δ and fluorinated HgBa2CuO4Fδ samples with different extra oxygen or fluorine content and Tc values. Fluorinated series also exhibits the cupola -like behavior for the Tc vs. δ dependence. NPD showed twice the amount of extra fluorine in comparison with those for the oxygenated Hg-1201 phases with close Tc's. The exchange of the extra oxygen by double amount of fluorine causes shortening of the apical Cu-O distances, while the in-plane ones, as well as Tc, do not vary. The influence of the external pressure on the structure and Tc of Hg-1201 strongly depends on the doping level. The increase of the extra oxygen content on going from underdoped to overdoped state results in the larger compression of the apical Cu-O and Ba-OHg distances while the HgO2 dumbbell as well as the distance between Ba and O from the (CuO2) layers becomes practically pressure independent. These results together with the data for fluorinated materials allow to elucidate the crucial structural features responsible for the Tc variation under high pressure.

  1. Evidence of interstitial oxygen in room temperature oxidized La2-xSrxCuO4+y (0-LESS-THAN-X-LESS-THAN-0.1)

    DEFF Research Database (Denmark)

    Rial, C.; Amador, U.; Morán, E.;

    1994-01-01

    The crystal structure, superconducting properties and oxygen stoichiometry of room temperature chemically oxidized La2-xSrxCuO4+y (x = 0.05, 0.09) have been studied by means of powder neutron diffraction, magnetic susceptibility and thermogravimetric analysis. The presence in these materials....... Besides, an important improvement in the superconducting properties (T(c) and superconducting volume fraction) of these compounds is observed after oxidation. On the other hand, no phase separation into two phases with different oxygen content is observed at low temperature....... of interstitial oxygen located at (1/4, y, 3/4; y almost-equal-to 1/4), as previously observed in oxygen-rich La2CuO4+y, is proposed from neutron diffraction data at different temperatures. This is supported by the excess of mass loss detected by TG for the oxidized materials relative to the starting ones...

  2. 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...

  3. Structural and superconducting properties of ion beam sputtered Nb thin films and Nb/Cu bilayers

    Science.gov (United States)

    Nath, S. K.; Dhawan, R.; Rai, S.; Lodha, G. S.; Sokhey, K. J. S.

    2012-01-01

    We present the results of a study of structural and superconducting properties of polycrystalline Nb thin films (200 Å, 300 Å, 400 Å, 700 Å and 1000 Å) and Nb/Cu bilayers (300 Å/300 Å and 400 Å/300 Å) prepared on Si substrates by ion beam sputtering at room temperature. The thicknesses, roughnesses at the surfaces and interfaces were determined by X-ray reflectivity whereas the grain sizes were determined from grazing incidence X-ray diffraction and transmission electron microscopic studies. The superconducting transition temperature ( T C) of Nb thin films are smaller than T C of bulk Nb. The Nb-200 Å sample does not show T C down to 2.3 K. The average size of the grains varies from 42 Å for Nb-200 Å sample to 69 Å for Nb-1000 Å sample. Our results show that the T C in these polycrystalline films is not only limited by its thickness but also by the size of the grains. The Nb films deposited in situ on the Cu layer (Nb/Cu) show a marginal increase in average sizes of the grains as compare to their respective values in Nb films of same thicknesses. As a result a marginal increase in T C of these films is also observed. The maximum decrease in T C due to oxygen intake during deposition should be about 0.5 K from its bulk value (9.28 K). We have attributed the large decrease in T C in our case on the basis of decrease in the Debye temperature and density of states at the Fermi level for Nb thin films as compared to their respective values for bulk Nb.

  4. Superconducting properties of La{sub 2-x}Ba{sub 2}CuO{sub 4} under pressure

    Energy Technology Data Exchange (ETDEWEB)

    Schottenhamel, Wolf; Wolter-Giraud, Anja; Buechner, Bernd [Leibniz Institute for Solid State and Materials Research Dresden, IFW Dresden (Germany); Huecker, Markus [Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY (United States)

    2016-07-01

    La{sub 2-x}Ba{sub 2}CuO{sub 4} displays an anomalous doping dependence associated with a deep suppression of superconductivity at the hole concentration x=1/8. The so-called 1/8-anomaly is accompanied by a structural transition in the average rotational symmetry of the CuO{sub 2} planes coinciding with the onset of a charge stripe order. It has been claimed that static stripe order destroys the superconducting phase coherence, while dynamic stripe correlations may promote superconductivity. In order to achieve more information about the relationship between superconductivity, stripe order and crystal structure we performed magnetization measurements under pressure up to 3 GPa on the single crystalline La{sub 2-x}Ba{sub 2}CuO{sub 4} with 0.095 ≤ x ≤ 0.125. Moreover, we relate the magnetization data to pressure dependent X-Ray diffraction studies. This way, we show that the specific superconducting properties as function of pressure are clearly correlated to structural changes.

  5. Thermoelectric power of (Cu0.5Tl0.5)-1223 superconducting phase added with BaSnO3 nanoparticles

    Science.gov (United States)

    Srour, A.; Malaeb, W.; Marhaba, S.; Awad, R.

    2017-07-01

    In this study, we report the thermoelectric power (TEP) measurements of Cu0.5Tl0.5Ba2Ca2Cu3O10-δ added with BaSnO3 nanoparticles. BaSnO3 nanoparticles were prepared by chemical co-precipitation method, while (BaSnO3)x/(CuT1)-1223 superconducting samples with 0.00 ≤ x ≤ 1.50 wt% were prepared using the solid-state reaction method. The standard four-probe technique was applied to measure DC electrical resistivity in the temperature range from 300 to 77 K. Superconducting transition temperature (Tc) increases up to 117.5 for x = 0.25 wt.% and then it decreases with further x addition. The TEP coefficient was measured as a function of temperature in a wide temperature range from ∼77 K (liquid nitrogen temperature) up to 280 K using a standard differential technique. The behavior of the obtained TEP coefficient is suit with high-Tc copper-oxide superconductors. The results were investigated according to two-band model with an extra linear term. Several parameters such as the pseudo-gap temperature (T*), Fermi energy (EF) and Fermi temperature (TF) values were calculated and discussed in terms of nanoparticles BaSnO3 addition.

  6. Superconductivity in the antiperovskite Dirac-metal oxide Sr3-xSnO

    Science.gov (United States)

    Oudah, Mohamed; Ikeda, Atsutoshi; Hausmann, Jan Niklas; Yonezawa, Shingo; Fukumoto, Toshiyuki; Kobayashi, Shingo; Sato, Masatoshi; Maeno, Yoshiteru

    2016-12-01

    Investigations of perovskite oxides triggered by the discovery of high-temperature and unconventional superconductors have had crucial roles in stimulating and guiding the development of modern condensed-matter physics. Antiperovskite oxides are charge-inverted counterpart materials to perovskite oxides, with unusual negative ionic states of a constituent metal. No superconductivity was reported among the antiperovskite oxides so far. Here we present the first superconducting antiperovskite oxide Sr3-xSnO with the transition temperature of around 5 K. Sr3SnO possesses Dirac points in its electronic structure, and we propose from theoretical analysis a possibility of a topological odd-parity superconductivity analogous to the superfluid 3He-B in moderately hole-doped Sr3-xSnO. We envision that this discovery of a new class of oxide superconductors will lead to a rapid progress in physics and chemistry of antiperovskite oxides consisting of unusual metallic anions.

  7. Localized electronic states and photoemission superconducting condensate in Bi 2Sr 2CaCu 2O 8+x

    Science.gov (United States)

    Ma, Jian; Quitmann, C.; Kelley, R. J.; Margaritondo, G.; Onellion, M.

    1995-04-01

    We present the first detailed angle-resolved photoemission evidence that there are two types of carriers that contribute to the photoe-mission superconducting condensate in Bi 2Sr 2CaCu 2O 8+x. Our data indicate that both itinerant and somewhat localized normal state carriers can contribute to the formation of Cooper pairs.

  8. 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...

  9. Investigation of Precursor Superconducting State in YBa2Cu3O7-δ through In-Plane Optical Spectroscopy

    Science.gov (United States)

    Lee, Kegan; Kamiya, Keisuke; Nakajima, Masamichi; Miyasaka, Shigeki; Tajima, Setsuko

    2017-02-01

    A precursor of superconductivity has been searched in the in-plane optical spectra of underdoped YBa2Cu3Oy, in which the previous c-axis optical spectra showed the presence of superconducting carriers at a temperature far above Tc [Uykur et al., https://doi.org/10.1103/PhysRevLett.112.127003" xlink:type="simple">Phys. Rev. Lett. 112, 127003 (2014)][Dubroka et al., https://doi.org/10.1103/PhysRevLett.106.047006" xlink:type="simple">Phys. Rev. Lett. 106, 047006 (2011)]. By carefully subtracting the normal component from the imaginary part of conductivity σ2(ω), we found a clear in-plane response of superconducting condensate at the temperature consistent with the c-axis optical data. This confirms that the precursory superconductivity developing with decreasing doping level is an intrinsic phenomenon in the cuprates.

  10. Structural and physical aspects of room temperature oxidized La2-xSrxCuO4+y (O-LESS-THAN-X-LESS-THAN-0.15)

    DEFF Research Database (Denmark)

    Rial, C.; Amador, U.; Moran, E.

    1994-01-01

    Crystal structure, oxygen stoichiometries and superconducting properties of RT chemically oxidized La2-xSrxCuO4+y (0 < x < 0.15) have been studied by means of powder neutron diffraction, thermogravimetric analysis and magnetic susceptibility measurements. The presence of interstitial oxygen locat...... at (1/4,1/4,approximate to 1/4), as in La2CuO4+y, is confirmed; however, phase separation at low temperature is not observed....

  11. Laser drilling: enhancing superconducting joint of GdBa2Cu3O7 - δ coated conductors

    Science.gov (United States)

    Park, Y. J.; Lee, M. W.; Oh, Y. K.; Lee, H. G.

    2014-08-01

    While GdBa2Cu3O7 - δ (GdBCO) coated conductors (CCs) have been proposed for superconducting applications, they have not been used in devices with persistent current mode (PCM) operation because of a lack of joining techniques. A superconducting joint of CCs, formed via melting diffusion and oxygenation annealing, offers no electrical resistance between the CCs, thus establishing a superconducting closed loop for PCM operation. Because superconductivity degrades with oxygen out-diffusion during melting diffusion, oxygenation annealing allows oxygen diffusion into the GdBCO lattices. As effective oxygenation annealing requires oxygen pathways in the joint, low solubility and diffusivity of oxygen in the buffer and CC substrate hinder full superconductivity recovery. Here we show a laser-drilling technique to produce microholes as conduits on the surfaces of GdBCO CCs’ to promote oxygen in-diffusion, which resulted in reduced superconductivity recovery time. Superconductivity was fully recovered after laser drilling, melting diffusion at 850 °C for 1 min, and oxygenation annealing at 500 °C for 350 h.

  12. STRUCTURAL AND SUPERCONDUCTING PROPERTIES OF LA2-XSRXCUO4+Y (0-LESS-THAN-X-LESS-THAN-0.15) PREPARED BY ROOM-TEMPERATURE CHEMICAL OXIDATION

    DEFF Research Database (Denmark)

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

    1995-01-01

    The presence of interstitial oxygen in room temperature chemically oxidized La2-xSrxCuO4+y, (0.15superconducting properties of these cuprates. The existence of a structural limit for the insertion of oxygen under the current oxidation...... conditions, related to the relieving of the internal strain of these materials, is proposed. Besides, oxidized materials show an almost constant T-c close to that corresponding to the optimum hole doping concentration. The coincidence of both features is remarked upon and discussed....

  13. Interface high-temperature superconductivity

    Science.gov (United States)

    Wang, Lili; Ma, Xucun; Xue, Qi-Kun

    2016-12-01

    Cuprate high-temperature superconductors consist of two quasi-two-dimensional (2D) substructures: CuO2 superconducting layers and charge reservoir layers. The superconductivity is realized by charge transfer from the charge reservoir layers into the superconducting layers without chemical dopants and defects being introduced into the latter, similar to modulation-doping in the semiconductor superlattices of AlGaAs/GaAs. Inspired by this scheme, we have been searching for high-temperature superconductivity in ultra-thin films of superconductors epitaxially grown on semiconductor/oxide substrates since 2008. We have observed interface-enhanced superconductivity in both conventional and unconventional superconducting films, including single atomic layer films of Pb and In on Si substrates and single unit cell (UC) films of FeSe on SrTiO3 (STO) substrates. The discovery of high-temperature superconductivity with a superconducting gap of ∼20 meV in 1UC-FeSe/STO has stimulated tremendous interest in the superconductivity community, for it opens a new avenue for both raising superconducting transition temperature and understanding the pairing mechanism of unconventional high-temperature superconductivity. Here, we review mainly the experimental progress on interface-enhanced superconductivity in the three systems mentioned above with emphasis on 1UC-FeSe/STO, studied by scanning tunneling microscopy/spectroscopy, angle-resolved photoemission spectroscopy and transport experiments. We discuss the roles of interfaces and a possible pairing mechanism inferred from these studies.

  14. Nonaqueous slip casting of YBa2Cu3O(7-x) superconductive ceramics. Ph.D. Thesis - 1993

    Science.gov (United States)

    Hooker, Matthew W.; Taylor, Theodore D.

    1994-01-01

    This study investigates the slip casting of YBa2Cu3O(7-x) powders using nonaqueous carrier liquids and fired ceramic molds. The parameters of the process examined here include the rheological properties of YBa2Cu3O(7-x) powder dispersed in various solvent/dispersant systems, the combination of nonaqueous slips with fired ceramic molds to form the superconductive ceramics, the process-property relationships using a four-factor factorial experiment, and the applicability of magnetic fields to align the YBa2Cu3O(7-x) grains during the casting process.

  15. Oxide-based platform for reconfigurable superconducting nanoelectronics

    Science.gov (United States)

    Veazey, Joshua P.; Cheng, Guanglei; Irvin, Patrick; Cen, Cheng; Bogorin, Daniela F.; Bi, Feng; Huang, Mengchen; Bark, Chung-Wung; Ryu, Sangwoo; Cho, Kwang-Hwan; Eom, Chang-Beom; Levy, Jeremy

    2013-09-01

    We report quasi-1D superconductivity at the interface of LaAlO3 and SrTiO3. The material system and nanostructure fabrication method supply a new platform for superconducting nanoelectronics. Nanostructures having line widths w ˜ 10 nm are formed from the parent two-dimensional electron liquid using conductive atomic force microscope lithography. Nanowire cross-sections are small compared to the superconducting coherence length in LaAlO3/SrTiO3, placing them in the quasi-1D regime. Broad superconducting transitions versus temperature and finite resistances in the superconducting state well below Tc ≈ 200 mK are observed, suggesting the presence of fluctuation- and heating-induced resistance. The superconducting resistances and V-I characteristics are tunable through the use of a back gate. Four-terminal resistances in the superconducting state show an unusual dependence on the current path, varying by as much as an order of magnitude. This new technology, i.e., the ability to ‘write’ gate-tunable superconducting nanostructures on an insulating LaAlO3/SrTiO3 ‘canvas’, opens possibilities for the development of new families of reconfigurable superconducting nanoelectronics.

  16. 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.

  17. Resin-impregnated bulk RE-Ba-Cu-O current leads for the superconducting magnet on maglev train

    Science.gov (United States)

    Tomita, M.; Nagashima, K.; Herai, T.; Murakami, M.

    2002-08-01

    Bulk RE-Ba-Cu-O (RE: rare earth elements) superconductors exhibit high critical current density ( Jc) and low thermal conductivity, that are the characteristics desired for the current lead applications. In this study, we studied whether the resin-impregnated Y-Ba-Cu-O rods can be used as the current lead for the superconducting magnet on a magnetically levitated train. The fatigue test showed that the mechanical properties of resin-impregnated Y-Ba-Cu-O rods are sufficiently good for maglev applications. We could also pass the electric currents of 500 A without heat generation. This was further confirmed by field distribution measurements, which showed that the superconducting state of the current lead was well maintained when the currents of 500 A were passed.

  18. Structure and superconductivity in (Bi{sub 0.35}Cu{sub 0.65})Sr{sub 2}YCu{sub 2}O{sub 7} and related materials

    Energy Technology Data Exchange (ETDEWEB)

    Jennings, R.A.; Williams, S.P.; Greaves, C. [Univ. of Birmingham (United Kingdom)

    1994-12-31

    The recently reported (Bi/Cu)Sr{sub 2}YCu{sub 2}O{sub 7} phase has been studied by time of flight powder neutron diffraction. The proposed 1212 structure has been confirmed and refinements have shown the oxygen in the (Bi/Cu)O layer is displaced by 0.78{angstrom} from the ideal (1/2,1/2,0) site (P4/mmm space group) along (100). Bond Valence Sum calculations have suggested oxidation states of Bi{sup 5+} and Cu{sup 2+} for the cations in the (Bi/Cu)O layers. The material is non-superconducting and all attempts to induce superconductivity have been unsuccessful. Work on the related material (Ce/Cu)Sr{sub 2}YCu{sub 2}O{sub y} has shown the ideal Ce content to be 0.5 Ce per formula unit. The introduction of Ba (10%) onto the Sr site dramatically increases phase stability and also induces superconductivity (62K).

  19. Proximitized NbN/NiCu nanostripes as new promising superconducting single-photon detectors

    Science.gov (United States)

    Pepe, Giampiero; Parlato, Loredana; Bonavolontà, Carmela; Valentino, Massimo; De Lisio, Corrado; Cristiano, Roberto; Ejrnaes, Mikkel; Myoren, Horoshi; Sobolewski, Roman

    2013-05-01

    Transport properties of NbN/NiCu superconductor/ferromagnet (S/F) nanostripes fabricated in both in single-wire and series-parallel, meander-type configurations are presented down to T = 4.2 K. In particular, the enhancement of the superconducting critical current has been observed at smaller widths, apparently, due to an extra pinning mechanism, arising from clustering of ferromagnetic atoms inside the thin S layer. Moreover, we observed a number of characteristic voltage steps on the nanostripe current-voltage characteristics and their nature was investigated as a function of temperature. An explanation in terms of active phase-slip phenomena has been proposed based of the time-dependent Ginzburg-Landau theory and led to an estimation of the inelastic electron-phonon relaxation time τe-ph ~ 1 ps, in agreement with the τopt = 1.2+/-0.3 ps value, measured by the femtosecond transient optical reflectivity spectroscopy method on the same bilayer. Transient optical properties of our superconducting S/F nano-bilayers have been also investigated and compared to those obtained for pure NbN nanostripe reference samples. Finally, electrical photoresponse signals of S/F heterostructures exposed to ultraweak pulsed (width 400 ps, repetition rate ~100 MHz) laser radiation at 850 nm wavelength exhibited the falling time of voltage responses directly dependent on the NiCu overlayer. We have also noticed that the presence of the top F layer and the resulting proximity effect reduced frequency of dark counts in our samples.

  20. Quantitative XPS analysis of silica-supported Cu Co oxides

    Science.gov (United States)

    Cesar, Deborah V.; Peréz, Carlos A.; Schmal, Martin; Salim, Vera Maria M.

    2000-04-01

    Copper-cobalt oxides with Cu/Co=5:5, 15:15 and 35:35 bulk ratio have been prepared by deposition-precipitation method at constant pH from copper and cobalt nitrate solutions. Different oxides were obtained by decomposition of the precursors at 673 K for 7 h in air and analyzed by X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). XRD data showed the formation of different oxide phases; for the bulk atomic ratio of 15Cu:15Co, a phase containing Cu and Co with spinel-like structure was observed, while the other bimetallic oxides presented CuO and Co 3O 4 as distinct phases. The XPS qualitative analysis has shown that all samples exhibited Cu 2+ and Co 3+ species at the surface. The Cu-Co spinel presented a displacement in Cu 2p binding energy value. A mathematical model was proposed from relative intensity ratios, which allowed the determination of the oxide particle thickness and the fraction of coverage at the support. This model described accurately the system and showed that cobalt improved the copper dispersion.

  1. Aluminium-oxide wires for superconducting high kinetic inductance circuits

    Science.gov (United States)

    Rotzinger, H.; Skacel, S. T.; Pfirrmann, M.; Voss, J. N.; Münzberg, J.; Probst, S.; Bushev, P.; Weides, M. P.; Ustinov, A. V.; Mooij, J. E.

    2017-02-01

    We investigate thin films of conducting aluminium-oxide, also known as granular aluminium, as a material for superconducting high quality, high kinetic inductance circuits. The films are deposited by an optimised reactive DC magnetron sputter process and characterised using microwave measurement techniques at milli-Kelvin temperatures. We show that, by precise control of the reactive sputter conditions, a high room temperature sheet resistance and therefore high kinetic inductance at low temperatures can be obtained. For a coplanar waveguide resonator with 1.5 kΩ sheet resistance and a kinetic inductance fraction close to unity, we measure a quality factor in the order of 700 000 at 20 mK. Furthermore, we observe a sheet resistance reduction by gentle heat treatment in air. This behaviour is exploited to study the kinetic inductance change using the microwave response of a coplanar wave guide resonator. We find the correlation between the kinetic inductance and the sheet resistance to be in good agreement with theoretical expectations.

  2. Superconductivity at 52.5 K in the lanthanum-barium-copper-oxide system

    Science.gov (United States)

    Chu, C. W.; Hor, P. H.; Meng, R. L.; Gao, L.; Huang, Z. J.

    1987-01-01

    The electrical properties of the (La/0/9/Ba/0.1/)CuO/4-y/ system are examined under ambient and hydrostatic pressures. The resistance, ac magnetic susceptibility, and superconductivity onset, midpoint, and intercept temperatures are measured. It is observed that at ambient pressure the resistance decreases with temperature decreases, and the ac susceptibility shows diamagnetic shifts starting at about 32 K. Under hydrostatic pressure a superconducting transition with an onset temperature of 52.5 K is observed, and the resistance increases at lower temperatures. The data reveal that the electrical properties of the La-Ba-Cu-O system are dependent on samples and preparation conditions. Various causes for the high temperature superconductivity of the system are proposed.

  3. PREPARATION OF ULTRA-FINE SUPERCONDUCTING YBa2Cu3O7-x POWDERS BY GEL COMBUSTION PROCESS%凝胶燃烧法制备超细YBa2Cu3O7-x超导粉末

    Institute of Scientific and Technical Information of China (English)

    郭建栋; 徐晓林; 王永忠; 张炎; 刘达颐; 石磊

    2005-01-01

    The ultra-fine superconducting YBa2Cu3O7-x powders were prepared by means of the gel combustion process using nitrates of Y, Ba and Cu as the starting materials and citric acid as the fuel. The resulting particle size and its superconducting properties is dependent on the nature of the auto-ignition reaction, which in turn depends upon the citrate-nitrate ratio in the gel. An attempt to determine the optimal citrate-nitrate ratio has been made in order to obtain pure, homogeneous and reasonably fine YBCO superconductor. In our experiments we found the best fuel-oxidant molar ratio to be 0.5.%纳米级细度的YBa2Cu3O7-x超导粉末有可能在第二代超导带材的研制中得到应用.超细YBa2Cu3O7-x超导粉末已经通过凝胶燃烧法制备成功.使用的起始物质是钇、钡、铜的硝酸盐以及作为燃烧剂的柠檬酸.产物颗粒的尺寸大小及其超导性能依赖于自燃过程的情况,而自燃过程又与凝胶中柠檬酸盐-硝酸盐的YBa2Cu3O7-x超导粉末.在本实验中我们发现最好的燃烧剂-氧化剂摩尔比为0.5.

  4. A possible mechanism of exciton exchange percolated superconductivity for the oxide Balacuo

    Science.gov (United States)

    Tao, Ruibao

    1987-08-01

    The effect of oxygen vacancies in (La 1- xBa x) 2CuO 4- y (Balacuo) is analyzed and it is pointed out that the vacancies in the Cu-O basal plane will break the bonds of Cu-O-Cu to make the hopping between those coppers disappear so that the electrical conduction in the Cu-O basal plane would become a bond percolation system consisting of an infinite cluster carrying the current with a great number of finite clusters hanging around. It is favorable to create some mechanism of exciton exchange so that the transition temperature Tc of superconductivity could be increased significantly. The comparison with YBa 2Cu 3O 9- y is also discussed briefly.

  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. Neutron irradiation damage effect on superconducting and normal state properties of the YBa 2Cu 3O 7 system

    Science.gov (United States)

    Przysłupski, P.; Wiśniewski, A.; Koleśnik, S.; Dobrowolski, W.; Pajączkowska, A.; Pytel, K.; Pytel, B.

    1988-06-01

    Effect of irradiation by fast neutrons on superconducting and normal state properties of the YBa 2Cu 3O 7 samples is presented. Transport measurements showed a degradation of all superconducting parameters, especially the transport critical current density. Critical current densities obtained from magnetization data exhibited a substantial increase / about 15 times at 77 K and H = 10 kOe/ after the irradiation with the fluence in the range 2.4·10 17 ÷ 8.7 · 10 17 n/cm 2. Such an anomalous bahavior is explained in terms of neutron created defects at intergrain regions and improved intragrain pinning.

  7. Co-doped Bi 2Sr 2CaCu 2O x: Anderson localization and superconductivity

    Science.gov (United States)

    Alméras, P.; Berger, H.; Margaritondo, G.; Ma, Jian; Quitmann, C.; Kelley, R. J.; Onellion, M.

    1994-08-01

    Cobalt-doping of Bi 2Sr 2CaCu 2O x beyond a critical level of 1.5-1.6 at % produces both a large decrease in the superconducting transition critical temperature and all of the classic symptoms of Anderson localization. These include: a negative slope of the abplane resistivity vs temperature, no dispersing states near the Fermi level and a decrease of the photoemission signal in the same region. The correlation between Anderson localization and high-temperature superconductivity at low doping levels supports a non-local interaction for the paring mechanism, such as antiferromagnetic spin fluctuations.

  8. Low energy excitations in superconducting La1.86Sr0.14CuO4

    DEFF Research Database (Denmark)

    Mason, T.E.; Aeppli, G.; Hayden, S.M.

    1993-01-01

    We present magnetic neutron scattering and specific heat data on the high-T(c) superconductor La1.86Sr0.14CuO4. Even when the samples are superconducting and the magnetic response, chi'', is suppressed, there are excitations with energies well below 3.5k(B)T(c). The wave-vector dependence of chi......'' is identical to that for the normal state, which implies that the low frequency excitations in our crystals are not those associated with the nodes of a clean d-wave superconductor. However, the data are consistent with gapless superconductivity induced by localized magnetic impurities, clearly observed...

  9. Quasiparticles in the superconducting state of Bi(2)Sr(2)CaCu(2)O(8+delta)

    Science.gov (United States)

    Kaminski; Mesot; Fretwell; Campuzano; Norman; Randeria; Ding; Sato; Takahashi; Mochiku; Kadowaki; Hoechst

    2000-02-21

    Recent improvements in momentum resolution lead to qualitatively new angle-resolved photoemission spectroscopy results on the spectra of Bi(2)Sr(2)CaCu(2)O(8+delta) (Bi2212) along the (pi,pi) direction, where there is a node in the superconducting gap. We now see the intrinsic line shape, which indicates the presence of true quasiparticles at all Fermi momenta in the superconducting state, and lack thereof in the normal state. The region of momentum space probed here is relevant for charge transport, motivating a comparison of our results to conductivity measurements by infrared reflectivity.

  10. Scaling between superconducting critical temperature and structural coherence length in YBa2Cu3O6.9 films

    Science.gov (United States)

    Gauzzi, A.; Jönsson-Åkerman, B. Johan; Clerc-Dubois, A.; Pavuna, D.

    2000-09-01

    Measurements of critical temperature Tc in superconducting YBa2Cu3O6.9 films with reduced long-range structural order show the validity of the empirical scaling relation ΔTc propto rc-2 between disorder-induced reduction of Tc and structural coherence length rc in the ab-plane. This result is quantitatively explained by the disorder-induced confinement of the charge carriers within each ordered domain of size rc. Our analysis of the data based on this picture enables us to precisely determine the Ginzburg-Landau superconducting coherence length in the ab-plane, ξab = 1.41 ± 0.04 nm.

  11. Superconducting thin films of BiSrCaCuO made by sequential electron beam evaporation

    Energy Technology Data Exchange (ETDEWEB)

    Steinbeck, J.; Anderson, A.C.; Tsauer, B.Y.; Strauss, A.J.

    1989-03-01

    Superconducting thin films of Bi/sub 2/Sr/sub 2/Ca/sub 1/Cu/sub 2/O/sub x/ have been made by sequential electron-beam evaporation of multiple layers of Bi and Cu metals and (Sr,Ca)F/sub 2/ on MgO substrates. The films were annealed at high temperature, first in wet O/sub 2/ and then in dry O/sub 2/, and cooled to room temperature in dry O/sub 2/. The resulting films which are -- 1 ..mu..m thick, have transition temperatures of -- 85 K. X-ray diffraction shows that the films are preferentially oriented with their c-axis perpendicular to the MgO substrate. The authors' best film has a zero-resistance temperature of 90 K and critical current densities of 8 x 10/sup 4/ A/cm/sup 2/ at 77 K and 2.5 x 10/sup 5/ A/cm/sup 2/ at 4.2 K.

  12. Proximity effect in planar superconducting tunnel junctions containing Nb/NiCu superconductor/ferromagnet bilayers

    Science.gov (United States)

    Pepe, G. P.; Latempa, R.; Parlato, L.; Ruotolo, A.; Ausanio, G.; Peluso, G.; Barone, A.; Golubov, A. A.; Fominov, Ya. V.; Kupriyanov, M. Yu.

    2006-02-01

    We present experimental results concerning both the fabrication and characterization of superconducting tunnel junctions containing superconductor/ferromagnet (S/F) bilayers made by niobium (S) and a weak ferromagnetic Ni0.50Cu0.50 alloy. Josephson junctions have been characterized down to T=1.4K in terms of current-voltage I - V characteristics and Josephson critical current versus magnetic field. By means of a numerical deconvolution of the I - V data the electronic density of states on both sides of the S/F bilayer has been evaluated at low temperatures. Results have been compared with theoretical predictions from a proximity model for S/F bilayers in the dirty limit in the framework of Usadel equations for the S and F layers, respectively. The main physical parameters characterizing the proximity effect in the Nb/NiCu bilayer, such as the coherence length and the exchange field energy of the F metal, and the S/F interface parameters have been also estimated.

  13. Superconductivity-induced magnetization depletion in a ferromagnet through an insulator in a ferromagnet-insulator-superconductor hybrid oxide heterostructure.

    Science.gov (United States)

    Prajapat, C L; Singh, Surendra; Paul, Amitesh; Bhattacharya, D; Singh, M R; Mattauch, S; Ravikumar, G; Basu, S

    2016-05-21

    Coupling between superconducting and ferromagnetic states in hybrid oxide heterostructures is presently a topic of intense research. Such a coupling is due to the leakage of the Cooper pairs into the ferromagnet. However, tunneling of the Cooper pairs though an insulator was never considered plausible. Using depth sensitive polarized neutron reflectivity we demonstrate the coupling between superconductor and magnetic layers in epitaxial La2/3Ca1/3MnO3 (LCMO)/SrTiO3/YBa2Cu3O7-δ (YBCO) hybrid heterostructures, with SrTiO3 as an intervening oxide insulator layer between the ferromagnet and the superconductor. Measurements above and below the superconducting transition temperature (TSC) of YBCO demonstrate a large modulation of magnetization in the ferromagnetic layer below the TSC of YBCO in these heterostructures. This work highlights a unique tunneling phenomenon between the epitaxial layers of an oxide superconductor (YBCO) and a magnetic layer (LCMO) through an insulating layer. Our work would inspire further investigations on the fundamental aspect of a long range order of the triplet spin-pairing in hybrid structures.

  14. Superconductivity-induced magnetization depletion in a ferromagnet through an insulator in a ferromagnet-insulator-superconductor hybrid oxide heterostructure

    Science.gov (United States)

    Prajapat, C. L.; Singh, Surendra; Paul, Amitesh; Bhattacharya, D.; Singh, M. R.; Mattauch, S.; Ravikumar, G.; Basu, S.

    2016-05-01

    Coupling between superconducting and ferromagnetic states in hybrid oxide heterostructures is presently a topic of intense research. Such a coupling is due to the leakage of the Cooper pairs into the ferromagnet. However, tunneling of the Cooper pairs though an insulator was never considered plausible. Using depth sensitive polarized neutron reflectivity we demonstrate the coupling between superconductor and magnetic layers in epitaxial La2/3Ca1/3MnO3 (LCMO)/SrTiO3/YBa2Cu3O7-δ (YBCO) hybrid heterostructures, with SrTiO3 as an intervening oxide insulator layer between the ferromagnet and the superconductor. Measurements above and below the superconducting transition temperature (TSC) of YBCO demonstrate a large modulation of magnetization in the ferromagnetic layer below the TSC of YBCO in these heterostructures. This work highlights a unique tunneling phenomenon between the epitaxial layers of an oxide superconductor (YBCO) and a magnetic layer (LCMO) through an insulating layer. Our work would inspire further investigations on the fundamental aspect of a long range order of the triplet spin-pairing in hybrid structures.

  15. Chemical Trend of Superconducting Critical Temperatures in Hole-Doped CuBO2, CuAlO2, CuGaO2, and CuInO2

    Science.gov (United States)

    Nakanishi, Akitaka; Katayama-Yoshida, Hiroshi; Ishikawa, Takahiro; Shimizu, Katsuya

    2016-09-01

    We calculated the superconducting critical temperature (Tc) for hole-doped CuXO2 (X = B, Al, Ga, and In) compounds using first-principles calculations based on rigid band model. The compounds with X = Al, Ga, and In have delafosite-type structures and take maximum Tc values at 0.2-0.3 with respect to the number of holes (Nh) in the unit-cell: 50 K for CuAlO2, 10 K for CuGaO2, and 1 K for CuInO2. The decrease of Tc for this change in X is involved by covalency reduction and lattice softening associated with the increase of ionic mass and radius. For CuBO2 which is a lighter compound than CuAlO2, the delafosite structure is unstable and a body-centered tetragonal structure emerges as the most stable structure. As the results, the electron-phonon interaction is decreased and Tc is lower by approximately 43 K than that of CuAlO2 at the hole-doping conditions of Nh = 0.2-0.3.

  16. Superconducting thin films of Tl 2Ca 2Ba 2Cu 3O y and Tl 2CaBa 2Cu 2O y

    Science.gov (United States)

    Ginley, D. S.; Kwak, J. F.; Hellmer, R. P.; Baughman, R. J.; Venturini, E. L.; Mitchell, M. A.; Morosin, B.

    1988-11-01

    We present techniques for preparing unoriented polycrystalline and epitaxial superconducting thin films of the Tl 2CaBa 2Cu 2O y and Tl 2Ca 2Ba 2Cu 3O y phases on a wide variety of substrates. The crucial steps determining the properties of the films are shown to be the air sintering and oxygen annealing following the initial metal deposition by electron beam evaporation under a slight oxygen overpressure. A sintered Tl-Ca-Ba-Cu-O pellet is employed as a source of excess Tl during sintering and annealing of the thin film. The Tl concentration in the final films controls the nature of the intergrain connections. The films are characterized by their structural, chemical, magnetic and transport properties. Zero resistance typically occurs at 97 K for Tl 2CaBa 2Cu 2O and at 106 K for Tl 2Ca 2Ba 2Cu 3O y. Transport critical currents of up to 110 000 A/cm 2 have been obtained at 77 K for unoriented Tl 2CaBa 2Cu 2O y, up to 160 000 A/cm 2 for epitaxial Tl 2Ca 2Ba 2Cu 3O y and up to 240 000 A/cm 2 for unoriented Tl 2Ca 2Cu 3O y films with little field dependence of the critical current observed.

  17. Dietary bioavailability of Cu adsorbed to colloidal hydrous ferric oxide

    Science.gov (United States)

    Cain, Daniel J.; Croteau, Marie-Noële; Fuller, Christopher C.

    2013-01-01

    The dietary bioavailability of copper (Cu) adsorbed to synthetic colloidal hydrous ferric oxide (HFO) was evaluated from the assimilation of 65Cu by two benthic grazers, a gastropod and a larval mayfly. HFO was synthesized, labeled with 65Cu to achieve a Cu/Fe ratio comparable to that determined in naturally formed HFO, and then aged. The labeled colloids were mixed with a food source (the diatom Nitzschia palea) to yield dietary 65Cu concentrations ranging from 211 to 2204 nmol/g (dry weight). Animals were pulse fed the contaminated diet and assimilation of 65Cu from HFO was determined following 1–3 days of depuration. Mass transfer of 65Cu from HFO to the diatom was less than 1%, indicating that HFO was the source of 65Cu to the grazers. Estimates of assimilation efficiency indicated that the majority of Cu ingested as HFO was assimilated (values >70%), implying that colloidal HFO potentially represents a source of dietary Cu to benthic grazers, especially where there is active formation and infiltration of these particles into benthic substrates.

  18. Superconductivity at 31 K in Alkaline Metal-Doped Cobalt Oxides

    Institute of Scientific and Technical Information of China (English)

    闻海虎; 杨海朋; 鲁希锋; 闫静

    2003-01-01

    By using a simple solid reaction method, we have fabricated alkaline metal doped cobalt oxides Anx CoO2+δ(An = Na, K). The magnetic measurement shows a superconducting-like diamagnetic signal at 31 K based on a strong superparamagnetic signal. Below 31 K, the magnetization hysteresis loops contain a strong rough linear superparamagnetic background and a superconducting hysteresis. The typical magnetization hysteresis loops for a type-Ⅱ superconductor are found. Preliminary resistive data also show a fast dropping of resistance below Tc.These give indication of superconductivity below 31 K in Anx CoO2+δ (An = Na, K).

  19. Temperature Dependence of the Superconducting Gap Anistropy in Bi_2 Sr_2CaCu_2O8+x

    Science.gov (United States)

    Ma, Jian; Quitmann, C.; Kelley, R. J.; Berger, H.; Margaritondo, G.; Onellion, M.

    1995-02-01

    Detailed data on the momentum-resolved temperature dependence of the superconducting gap of Bi_2Sr_2CaCu_2O8+x are presented, complemented by similar data on the intensity of the photoemission superconducting condensate spectral area. The gap anisotropy between the Gamma-overline{M} and Gamma-X directions increases markedly with increasing temperature, contrary to what happens for conventional anisotropic-gap superconductors, such as lead. Specifically, the size of the superconducting gap along the Gamma-X direction decreases to values indistinguishable from zero at temperatures for which the gap retains virtually full value along the Gamma-overline{M} direction. These data rule out the simplest type of d-wave order parameter.

  20. A new technique for the growth of superconducting YBa2Cu3O6 + δ crystals completely separated from flux

    Science.gov (United States)

    Rao, S. M.; Loo, B. H.; Wang, N. P.; Kelley, R. J.

    1991-04-01

    Growth of completely flux-separated YBa2Cu3O6 + δ (referred to as 123 phase) crystals using a novel technique is described. The technique employs a modification of the seed pulling method commonly used in crystal growth. The crystals are grown in the temperature range of 960-1000°C using a BaCuO2 flux. A 123 flux ratio of 1:5 is maintained. Photographs of the crystals and photomicrograph of the surfaces are presented to show complete flux-separation of the crystals measuring 6 mm × 3 mm × 1 mm. The Raman spectra recorded on the as-grown crystals show that they are in the tetragonal phase. Magnetic susceptibility measurements on crystals annealed in an oxygen atmosphere show a superconducting transition starting at 71 K. The present technique offers a possibility of growing large, completely flux-separated crystals of 123 for superconductivity research.

  1. Structural studies of Nd$_{1.85}$Ce$_{0.15}$CuO$_{4}$ $+$ Ag superconducting system

    Indian Academy of Sciences (India)

    N RADHIKESH RAVEENDRAN; A K SINHA; R RAJARAMAN; M PREMILA; E P AMALADASS; K VINOD; J JANAKI; S KALAVATHI; AWADHESH MANI

    2016-06-01

    We have studied for the first time the effect of Ag addition (0–15 wt%) to the superconducting system, Nd$_{1.85}$Ce$_{0.15}$CuO$_{4}$, on its crystal structure and local structural features, using synchrotron X-ray diffraction(SXRD) and Raman spectroscopy, respectively. SXRD and subsequent Rietveld refinement studies on powders of Nd$_{1.85}$Ce$_{0.15}$CuO$_4$ $+$ Ag system indicate a small but significant change in lattice parameter upon Ag addition, showing evidence for possible incorporation of Ag to the extent of $\\sim$1 wt%. Raman spectroscopic studies indicate that the parent structure of Nd$_{1.85}$Ce$_{0.15}CuO$_{4}$ remains unaffected with no major local structural changes on doping with silver. However, all Raman modes show minor phonon hardening upon Ag addition, which is consistent with the unit cell volume reduction as is observed in XRD. A systematic bleaching out of the apical oxygen defect mode was also observed with increased Ag addition. Polarized Raman measurements helped to identify the asymmetric nature of the B1g Raman mode. X-ray diffraction studies on pellets of Nd$_{1.85}$Ce$_{0.15}CuO$_4$ $+$ Ag system further indicate a randomization of preferred orientation upon Ag addition. The superconductivity of the Nd$_{1.85}$Ce$_{0.15}$CuO$_4$ $+$ Ag system has been well characterized for all the compositions studied.

  2. Superconductivity in the antiperovskite Dirac-metal oxide Sr$_3$SnO

    CERN Document Server

    Oudah, Mohamed; Yonezawa, Shingo; Fukumoto, Toshiyuki; Kobayashi, Shingo; Sato, Masatoshi; Maeno, Yoshiteru

    2016-01-01

    Oxides with perovskite-based structures have been known as essential materials for fascinating phenomena such as high-temperature and unconventional superconductivity. Discoveries of these oxide superconductors have driven the science community to vastly extend the concepts of strongly correlated electron systems. The base of these materials, the cubic perovskite oxides, $AB$O$_3$, also exhibit superconductivity with $T_{\\mathrm{c}}$ of up to 30 K, as reported for Ba$_{0.6}$K$_{0.4}$BiO$_3$. Perovskite oxides have their counterparts, antiperovskite oxides $A_3B$O (or "$B$O$A_3$"), in which the position of metal and oxygen ions are reversed and therefore metallic $B$ ions take unusual negative valence states. However, no superconductivity has been reported among antiperovskite oxides. Here, we report the discovery of the first superconducting antiperovskite oxide Sr$_3$SnO with $T_{\\mathrm{c}}$ of around 5 K. Sr$_3$SnO possesses Dirac points in its electronic structure, originating from the inversion of bands ...

  3. Enhanced charge stripe order of superconducting La2-xBaxCuO4 in a magnetic field

    Science.gov (United States)

    Hücker, M.; v. Zimmermann, M.; Xu, Z. J.; Wen, J. S.; Gu, G. D.; Tranquada, J. M.

    2013-01-01

    The effect of a magnetic field on the charge stripe order in La2-xBaxCuO4 has been studied by means of high-energy (100 keV) x-ray diffraction for charge carrier concentrations ranging from strongly underdoped to optimally doped. We find that charge stripe order can be significantly enhanced by a magnetic field applied along the c axis, but only at temperatures and dopings where it coexists with bulk superconductivity at zero field. The field also increases stripe correlations between the planes, which can result in an enhanced frustration of the interlayer Josephson coupling. Close to the famous x=(1)/(8) compound, where zero field stripe order is pronounced and bulk superconductivity is suppressed, charge stripe order is independent of a magnetic field. The results for La2-xBaxCuO4 resemble recent observations in YBa2Cu3O6+δ and, independent of potential differences in the microscopic origin of charge order in these two compounds, imply a very similar competition with three-dimensionally coherent superconductivity.

  4. Structural and superconducting properties of YBa2Cu3-xMxOy (M=Ag, Al

    Directory of Open Access Journals (Sweden)

    S Falahati

    2009-08-01

    Full Text Available   Samples of YBa2Cu3-xAgxOy with x=0, 0.1, 0.15, 0.2, 0.3 and samples of YBa2Cu3-xAlxOy with x=0, 0.01, 0.02, 0.03 and 0.045 are prepared by the sol-gel method. Structural and superconducting properties of samples are studied by electrical resistivity (R-T, X-ray diffraction (XRD and scanning electron microscopy (SEM. All the samples show transition to superconducting state and the transition temperatures of the samples increased with increasing Ag doping up to x=0.15. R-T measurements show a small decrease of TC (zero with increasing Al doping up to x=0.02, and followed by a faster decrease with increasing doping concentration. YBCO grains are better linked with increasing Ag doping. So, Ag has positive effects in superconducting properties of YBCO. The crystal structure of samples was refined by MAUD. These results show tha, Ag is substituted for Cu(1 in YBCO. According to these analysis, we introduce x=0.15 as the optimum value for doping concentration .

  5. Superconducting phase formation in random neck syntheses: a study of the Y-Ba-Cu-O system by magneto-optics and magnetometry

    Energy Technology Data Exchange (ETDEWEB)

    Willems, J B; Landau, I L; Hulliger, J [Department of Chemistry and Biochemistry, University of Berne, Freiestrasse 3, CH-3012-Berne (Switzerland); Albrecht, J [Max-Planck-Institute for Metals Research, Heisenbergstrasse 3, D-70569 Stuttgart (Germany)

    2009-04-15

    Magneto-optical imaging and magnetization measurements were applied to investigate the local formation of a superconducting phase effected by a random neck synthesis in the Y-Ba-Cu-O system. Polished pellets of strongly inhomogeneous ceramic samples show clearly the appearance of superconducting material in the intergrain zones of binary primary particles reacted under different conditions. Susceptibility measurements allowed evaluation of the superconducting critical temperature, which turned out to be close to that of optimally doped YBa{sub 2}Cu{sub 3}O{sub 7-x}.

  6. Superconducting correlations above Tc in the pseudogap state of Bi2Sr2CaCu2O8 +δ cuprates revealed by angular-dependent magnetotunneling

    Science.gov (United States)

    Jacobs, Th.; Katterwe, S. O.; Krasnov, V. M.

    2016-12-01

    We present an angular-dependent magnetotunneling technique, which facilitates unambiguous separation of superconducting (supporting circulating screening currents) and nonsuperconducting (not supporting screening currents) contributions to the pseudogap phenomenon in layered Bi2Sr2CaCu2O8 +δ cuprates. Our data indicate persistence of superconducting correlations at temperatures up to 1.5 Tc in a form of both phase and amplitude fluctuations of the superconducting order parameter. However, despite a profound fluctuations region, only a small fraction of the pseudogap spectrum is caused by superconducting correlations, while the dominating part comes from a competing nonsuperconducting order, which does not support circulating orbital currents.

  7. Two-dimensional superconducting fluctuations in stripe-ordered La1.875Ba0.125CuO4.

    Science.gov (United States)

    Li, Q; Hücker, M; Gu, G D; Tsvelik, A M; Tranquada, J M

    2007-08-10

    Recent spectroscopic observations of a d-wave-like gap in stripe-ordered La(2-x)Ba(x)CuO(4) with x=1/8 have led us to critically analyze the anisotropic transport and magnetization properties of this material. The data suggest that concomitant with the spin ordering is an electronic decoupling of the CuO(2) planes. We observe a transition (or crossover) to a state of two-dimensional (2D) fluctuating superconductivity, which eventually reaches a 2D superconducting state below a Berezinskii-Kosterlitz-Thouless transition. Thus, it appears that the stripe order in La(2-x)Ba(x)CuO(4) frustrates three-dimensional superconducting phase order, but is fully compatible with 2D superconductivity and an enhanced T(c).

  8. Two-Dimensional Superconducting Fluctuations in Stripe-Ordered La1.875Ba0.125CuO4

    Science.gov (United States)

    Li, Q.; Hücker, M.; Gu, G. D.; Tsvelik, A. M.; Tranquada, J. M.

    2007-08-01

    Recent spectroscopic observations of a d-wave-like gap in stripe-ordered La2-xBaxCuO4 with x=(1)/(8) have led us to critically analyze the anisotropic transport and magnetization properties of this material. The data suggest that concomitant with the spin ordering is an electronic decoupling of the CuO2 planes. We observe a transition (or crossover) to a state of two-dimensional (2D) fluctuating superconductivity, which eventually reaches a 2D superconducting state below a Berezinskii-Kosterlitz-Thouless transition. Thus, it appears that the stripe order in La2-xBaxCuO4 frustrates three-dimensional superconducting phase order, but is fully compatible with 2D superconductivity and an enhanced Tc.

  9. Detailed magnetization study of superconducting properties of YBa2Cu3O7-x ceramic spheres

    Science.gov (United States)

    Landau, I. L.; Willems, J. B.; Hulliger, J.

    2008-03-01

    We present a magnetization study of low density YBa2Cu3O7-x ceramics carried out in magnetic fields H such that 0.5 Oe85 K, using low field magnetization measurements, we were able to evaluate the temperature dependence of λ, which turned out to be very close to predictions from conventional Ginzburg-Landau theory. Although the present samples consisted of randomly oriented grains, specifics of magnetization measurements allowed for evaluation of λab(T). Good agreement between our estimation of the grain size and the real sample structure provides evidence for the validity of this analysis of magnetization data. Measurements of the equilibrium magnetization in high magnetic fields were used for evaluation of Hc2(T). At temperatures close to Tc, the Hc2(T) dependence turned out to be linear, in agreement with Ginzburg-Landau theory. The value of the temperature at which Hc2 vanishes coincides with the superconducting critical temperature evaluated from low field measurements, which is important evidence of the validity of both approaches to the analysis of magnetization data.

  10. X-ray-absorption fine-structure studies of superconducting Tl2CaBa2Cu2Ox thin films

    Science.gov (United States)

    Dimarzio, D.; Wiesmann, H.; Chen, D. H.; Heald, S. M.

    1990-07-01

    Superconducting Tl-Ca-Ba-Cu-O thin films have been prepared by the technique of reactive magnetron sputtering using targets of Tl, Ca-Ba, and Cu. Three films with different quality superconducting transitions were fabricated and analyzed. X-ray-absorption fine-structure measurements were performed on the Cu K edge in order to determine orientation, bond lengths, number of nearest neighbors, and relative disorder as a function of the quality of their superconducting transition. Magnetically oriented powder samples of the appropriate superconducting phase were used for comparison. X-ray-absorption near-edge results reveal increasing CuO2 plane orientation parallel to the substrate as the quality of the superconducting transition improved, consistent with x-ray-diffraction data. Extended x-ray-absorption fine-structure (EXAFS) measurements also show this trend. EXAFS gives a Cu-O(1) bond length of 1.92+/-0.01 Å for all three films, and all three samples exhibit an increasing Debye-Waller disorder factor consistent with the deterioration in the quality of their superconducting transitions.

  11. Effects of grain size and grain boundary on critical current density of high T(sub c) superconducting oxides

    Science.gov (United States)

    Zhao, Y.; Zhang, Q. R.; Zhang, H.

    1990-01-01

    By means of adding impurity elements in high T sub c oxides, the effects were studied of grain size and grain boundary on the critical current density of the following systems: YBa2Cu3O(7-y) and Bi-Pr-Sr-Ca-Cu-O. In order to only change the microstructure instead of the superconductivity of the grains in the samples, the impurity elements were added into the systems in terms of the methods like this: (1) substituting Y with the lanthanide except Pr, Ce, and Tb in YBa2Cu3O(7-y) system to finning down grains in the samples, therefore, the effect can be investigated of the grain size on the critical current density of 1:2:3 compounds; (2) mixing the high T sub c oxides with the metal elements, such as Ag, according to the composition of (high T sub c oxide)1-xAgx to metallize the grain boundaries in the samples, studying the effect of the electric conductivity of the grain boundaries on the critical current density; (3) adding SiO2, PbO2, and SnO2 into the high T sub c oxide to form impurity phases in the grain boundaries, trying to find out the effects of the impurity phases or metalloid grain boundaries on the critical current density of the high T sub c superconductors. The experimental results indicate that in the case of of the presence of the metalloid grain boundaries finning down grains fails to enhance the j sub c, but restrains it strongly, the granular high T sub c superconductors with the small size grains coupled weakly is always the low j sub c system.

  12. Superconducting and ferromagnetic properties of NbN/NiCu and NbTiN/NiCu bilayer nanostructures for photon detection

    Science.gov (United States)

    Klimov, A.; Puźniak, R.; Aichner, B.; Lang, W.; Joon, E.; Stern, R.; Słysz, W.; Guziewicz, M.; Juchniewicz, M.; Borysiewicz, M. A.; Kruszka, R.; Wegrzecki, M.; Łaszcz, A.; Czerwinski, A.; Sobolewski, Roman

    2015-05-01

    Performance of superconducting single-photon detectors based on resistive hotspot formation in nanostripes upon optical photon absorption depends strongly on the critical current density JC of the fabricated nanostructure. Utilization of an ultrathin, weak-ferromagnet cap layer on the top of a superconducting film enhances of the structure's JC due to an extra flux pinning. We have fabricated a number of both NbN/NiCu and NbTiN/NiCu superconductor/ferromagnet (S/F) ultrathin bilayers and microbridges. NbN and NbTiN underlayers with thicknesses varying from 4 to 7 nm were grown using dc-magnetron sputtering on chemically cleaned sapphire single-crystal substrates. After rapid thermal annealing at high temperatures, the S films were coated with Ni0.54Cu0.46 overlayers with thicknesses of about 6 nm, using cosputtering. Compositions of the deposited films were confirmed by EDX spectroscopy analysis, while TEM studies demonstrated excellent epitaxial quality of our S layers with ~2-nm-thick F/S transition layer and atomically-sharp S/substrate interface. Magnetic properties of bilayers were studied using both the SQUID and Vibrating Sample Magnetometer techniques in low and high magnetic fields. Low-temperature tests confirmed that in all cases NiCu films were ferromagnetic with the Curie temperature of above 30 K. Below the bilayer critical temperature of approx. 12-13 K, the structures were fully proximitized with the strong superconducting signal. For superconducting transport properties characterization, we used bilayers patterned into 40-μm-long microbridges with the width varying from 0.4 μm to 2 μm. The same S/F nanostructures were also used to study their superconducting fluctuations. The temperature dependence of magnetoresistance demonstrated highly 2-dimensional character with an unusual negative region that extended almost to room temperature. In the S/F sample, the fluctuations were observed to be substantially below theoretical expectations.

  13. Tuning the superconductivity in single-layer FeSe/oxides by interface engineering

    Science.gov (United States)

    Peng, Rui

    2015-03-01

    The discovery of high Tc in single-layer FeSe films has enormous implications for both searching new high Tc superconductors and exploring the important factors for high temperature superconductivity. In this talk, I will show our recent angle-resolved photoemission studies on various FeSe-based heterostructures grown by molecular beam epitaxy. We systematically studied the electronic structures and superconducting properties of FeSe with varied strain, different interfacial oxide materials and different thicknesses, and uncover that electronic correlations and superconducting gap-closing temperatures are tuned by interfacial effects. We exclude the direct relation between superconductivity and tensile strain, or the energy of an interfacial phonon mode, and demonstrate the crucial and non-trivial role of FeSe/oxide interface on the high pairing temperature. By tuning the interface, superconducting pairing temperature reaches up to 75K in FeSe/Nb:BaTiO3/KTaO3 with the in-plane lattice of 3.99 Å, which sets a new superconducting-gap-closing temperature record for iron-based superconductors, and may paves the way to more cost-effective applications of ultra-thin superconductors. Besides, in extremely tensile-strained single-layer FeSe films, we found that the Fermi surfaces consist of two elliptical electron pockets at the zone corner, without detectable hybridization. The lifting of degeneracy is clearly observed for the first time for the iron-based superconductors with only electron Fermi surfaces. Intriguingly, the superconducting gap distribution is anisotropic but nodeless around the electron pockets, with minima at the crossings of the two pockets. Our results provide important experimental foundations for understanding the interfacial superconductivity and the pairing symmetry puzzle of iron-based superconductors, and also provide clues for further enhancing Tc through interface engineering.

  14. Reinforced fluropolymer nanocomposites with high-temperature superconducting Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub y}

    Energy Technology Data Exchange (ETDEWEB)

    Jayasree, T. K., E-mail: drjayasreetk@gmail.com [Laboratory for Molecular Photonics and Electronic (Lamp), Department of Physics, National Institute of Technology, Calicut, Kerala, India - 673601 and Department of Physics, Sree Ayyappa College, Eramallikkara, Chengannur, Kerala-689109 (India)

    2014-10-15

    Bismuth Strontium Calcium Copper Oxide (Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub y})/Polyvinylidene fluoride (PVDF) nanocomposite was prepared and their thermal properties were analyzed. The composite consists of the polyvinylidene fluoride (PVDF) as an insulating polymer matrix, and homogenously distributed Bismuth strontium calcium copperoxide (2212) nanoparticles. SEM data shows flaky grains of the superconductor coated and linked by polymer. Differential scanning calorimetry (DSC) results indicated that the melting point was not affected significantly by the addition of BSCCO. However, the addition of superconducting ceramic resulted in an extra melting peak at a lower temperature (145°C). Thermogravimetric analysis of the samples shows that the onset decomposition temperature of the PVDF matrix was decreased by the addition of SC filler.

  15. Structural studies and c dependence in La2-DyCaBa2Cu4+O type mixed oxide superconductors

    Indian Academy of Sciences (India)

    S Rayaprol; Krushna Mavani; C M Thaker; D S Rana; Keka Chakravorty; S K Paranjape; M Ramanadham; Nilesh A Kulkarni; D G Kuberkar

    2002-05-01

    A new series of mixed oxide superconductors with the stoichiometric composition La2-DyCaBa2Cu4+O ( = 0.0 - 0.5, = 2) has been studied for structural and superconductiong properties. Our earlier studies on La2-(Y/Er)CaBa2Cu4+O series, show a strong dependence of c on hole concentration (sh). In the present work, the results of the analysis of the neutron diffraction measurements at room temprerature on = 0.3 and 0.5 samples are reported. It is interesting to know that Ca substitutes for both La and Ba site with concomitant displacement of La onto Ba site. Superconductivity studies show that maximum c is obtained for = 0.5, = 1.0 sample (c ∼ 75 K), for La1.5Dy0.5Ca1Ba2Cu5O (La-2125).

  16. The effects of interstitial oxygen on superconducting electronic phases in strontium and oxygen co-doped La1.937Sr0.063CuO4+δ

    Institute of Scientific and Technical Information of China (English)

    Shen Cai-xia; Shen Xiao-Li; Lu Wei; Dong Xiao-Li; Li Zheng-Cai; Xiong Ji-Wu; Zhou Fang

    2008-01-01

    Strontium and oxygen co-doped La1.937Sr0.063CuO4+δ superconductor with Tc≈40K, which is obtained by oxidizing strontium-doped starting ceramic sample La1.937Sr0.063CuO4 in NaClO solution, is annealed under different conditions to allow interstitial oxygen to redistribute. The evolution of the intrinsic superconducting property with the oxygen redistribution is studied in detail by magnetic measurements in various fields. It is found that there occurs the electronic phase separation from the single superconducting phase with Tc≈40K into two coexisting superconducting states with values of Tc: 15 and 40K or of 15 and 35K in this system, depending on annealing condition. Our results indicate that the 15, 35 and 40K superconducting phases associated with the excess oxygen redistribution are all thermodynamically meta-stable intrinsic states in this Sr/O co-doped cuprate.

  17. Low temperature magnetic force microscopy on ferromagnetic and superconducting oxides

    Science.gov (United States)

    Sirohi, Anshu; Sheet, Goutam

    2016-05-01

    We report the observation of complex ferromagnetic domain structures on thin films of SrRuO3 and superconducting vortices in high temperature superconductors through low temperature magnetic force microscopy. Here we summarize the experimental details and results of magnetic imaging at low temperatures and high magnetic fields. We discuss these data in the light of existing theoretical concepts.

  18. Effect of CuO2 planes on the structural and superconducting transport properties of [CuTl - 12(n - 1)n;n = 2,3,4] superconductor family

    Science.gov (United States)

    Muzaffar, M. Usman; Khan, Nawazish A.

    2016-06-01

    Cu0.5Tl0.5Ba2Can-1CunO2n+4-δ (n = 2, 3, 4) superconducting bulk samples have been synthesized by using two-step solid state reaction method. We investigated the effects of CuO2 planes on the structural and superconducting transport properties of [CuTl - 12(n - 1)n; n = 2, 3, 4] superconducting family. These samples were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) absorption spectroscopy and DC-resistivity (ρ) measurements. These samples are c-axis length oriented and have shown orthorhombic crystal structure. All the samples have shown metallic variations of resistivity from room temperature down to onset of superconductivity. The zero resistivity critical temperature Tc(R = 0) increases with the increase in superconducting planes and normal state resistivity systematically decreases, which show the density of inadvertent defects decreases in the final compound. The apical oxygen phonon modes are hardened as observed in the FTIR absorption measurements. The intrinsic microscopic superconducting parameters, such as the cross-over temperatures, coherence length along c-axis (ξc(0)) at 0 K, inter-layer coupling (J), inter-grain coupling (α) and fermi velocity (VF), were extracted from the fluctuation-induced conductivity (FIC) analysis. FIC analysis also showed the improvement in superconductivity with the increase in CuO2 planes.

  19. Oxygenation and superconductivity of Tl2CaBa2Cu2O8- x

    Science.gov (United States)

    Wu, Nae-Lih; Chu, H. T.

    1990-05-01

    Oxygenation of Tl 2CaBa 2Cu 2O 8- x between 250°C and 800°C was studied. The curves which plotted the amount of oxygen adsorbed as a function of oxygenation temperature indicated the presence of two oxygen adsorption processes, including one which prevailed at temperature below 400°C and the other between 500°C and 700°C. When the compound was oxygenated consecutively at increasing temperatures, the Tc of the oxide first increased and then decreased, exhibiting a maximum after oxygenation at 400°C. The Tc increased almost linearly with the amounts of oxygen adsorbed below 400°C but showed no unique (one-to-one) correlation with the overall oxygen content of the oxide.

  20. Neutron-Scattering Evidence for a Periodically Modulated Superconducting Phase in the Underdoped Cuprate La1.905Ba0.095CuO4

    Science.gov (United States)

    Xu, Zhijun; Stock, C.; Chi, Songxue; Kolesnikov, A. I.; Xu, Guangyong; Gu, Genda; Tranquada, J. M.

    2014-10-01

    The role of antiferromagnetic spin correlations in high-temperature superconductors remains a matter of debate. We present inelastic neutron-scattering evidence that gapless spin fluctuations coexist with superconductivity in La1.905Ba0.095CuO4. Furthermore, we observe that both the low-energy magnetic spectral weight and the spin incommensurability are enhanced with the onset of superconducting correlations. We propose that the coexistence occurs through intertwining of spatial modulations of the pair wave function and the antiferromagnetic correlations. This proposal is also directly relevant to sufficiently underdoped La2-xSrxCuO4 and YBa2Cu3O6+x.

  1. Metal-Insulator Transition and Superconductivity in Spinel-Type System Cu 1-xZnxIr 2S 4

    Science.gov (United States)

    Suzuki, Hiroyuki; Furubayashi, Takao; Cao, Guanghan; Kitazawa, Hideaki; Kamimura, Akira; Hirata, Kazuto; Matsumoto, Takehiko

    1999-08-01

    The thiospinel compoundCuIr2S4 exhibits the metal-insulator (M-I) transitionaccompanied by the structural transition. In this work, compounds ofCu1-xZnxIr2S4 in the composition range 0≤x≤0.5 were synthesized to examine the effects of excess electronssupplied by replacing Cu with Zn. The samples were investigated bymeasurements of X-ray diffraction, electrical resistance and magneticsusceptibility. The M-I transition temperature T MIdecreases with increasing x. Results are discussed on the basis ofthe model of charge ordering for the insulating state. It was foundthat the samples with x≥0.3 show no M-I transition and exhibitsuperconductivity. The transition temperature T C is 2.8 Kfor x= 0.3 and 2.2 K for x= 0.5. The ground state of the systemchanges from insulating to superconducting with increasing Zncontent.

  2. Structure, spin-stripe order, and superconductivity in La1.905 Ba 0.095 CuO 4 with and without 1% Zn substitution of Cu

    Science.gov (United States)

    Wen, Jinsheng; Xu, Z.; Xu, G.; Jie, Q.; Hucker, M.; Zheludev, A.; Tian, W.; Winn, B.; Zarestky, J.; Singh, D.; Hong, T.; Li, Q.; Gu, G.; Tranquada, J.

    2011-03-01

    We have performed susceptibility, thermal transport, and neutron scattering measurements to study the effect of Zn and magnetic field on the structure, spin-stripe order and superconductivity, and the interplay between them in La 1.905 Ba 0.095 Cu O4 with and without 1% Zn. It is shown that the bulk superconductivity is depressed by either the Zn doping or the magnetic field, spin stripe order is enhanced, and the structure is unaffected. For a range of magnetic field, the spin stripe order appears to stabilize a quasi-two-dimensional vortex glass phase. Supported by Office of Basic Energy Sciences, US DOE, under Contract No. DE-AC02-98CH10886.

  3. Cu-Nb reinforced (Nb, Ti){sub 3}Sn superconducting wire; Cu-Nb hokyo anteika (Nb, Ti){sub 3}Sn chodendo sen

    Energy Technology Data Exchange (ETDEWEB)

    Sakamoto, H.; Endo, S.; Kimura, A.; Wada, K.; Meguro, S. [The Furukawa Electric Co., Ltd., Tokyo (Japan); Watanabe, K.; Awaji, S. [Tohoku Univ., Sendai (Japan)

    2000-05-29

    The development of Nb{sub 3}Sn super-conducting wire material by combining in-Situ Cu-Nb alloy as a reinforced stabilization material in the wire inside has been carried out until now. Since the reinforced stabilization wire materials are used for cryogenic magnet of large diameter refrigerating machine, manufacture of long wire is vital. In this report, the results of investigating characteristics of Cu-Nb reinforced stabilization wire materials produced in different manufacturing scale are reported. The Cu-20wt%-Nb alloy is adopted as the reinforced stabilization material of the bronze process Nb{sub 3}Sn super-conducting wire. The produced wire is heat-treated at 650 degrees C and 864ks for 240 hrs and its characteristics are investigated. The non-copper part Jc of the reinforced stabilization wire material is 551A/mm {sup 2} at 12T, 184A/mm{sup 2} at 16T, and 76A/mm{sup 2} at 18T, and rates to the non-copper part Jc of the comparison wire materials in the same magnetic field are 0.87, 0.75 and 0.61 respectively. (NEDO)

  4. Electrical conductivity plus probability of superconductivity in α-CuSe/klockmannite; bulk and nano-layers

    Energy Technology Data Exchange (ETDEWEB)

    Shojaei, Ali Reza, E-mail: Ali.r.shojaei@gmail.com

    2015-05-25

    Highlights: • We calculated electrical conductivity of α-CuSe in bulk state and nano-layers (NLs). • We found a large anisotropy (nearly six orders of magnitude) in bulk conductivities. • Our studies show probability of superconductivity occurrence in α-CuSe bulk. • We considered a simple model for feasibility study of this occurrence in CuSe bulk. • We found a high anisotropy (nearly 10{sup 6} orders of magnitude) in NLs conductivities. - Abstract: In this paper, a computational study is carried out on unusual electrical conductivity of α-CuSe compound in the bulk state and its nano-layers (NLs). The property is studied by using Full-potential calculations and the Boltzmann transport equation assuming a suitable temperature-dependent relaxation time for charge carriers. The dependence of electrical conductivity per temperature changes is considered from 80 up to 330 K as well as separately in low-temperature. Our results show that CuSe has a high anisotropy electrical conductivity meaning that the in-plane conductivity is very good, with high hole transport but the z-axis transport is completely different, with two types of electron and hole carriers. By considering the curves of electrical conductivity in low-temperature and again reviewing the experimental data, we predict probability of occurrence of a superconductivity phase transition in this compound in a temperature about 3 K. This possibility has been discussed by assuming a simple model. In continuation of our previous work, we calculate the values of electrical conductivity of the most stable NLs of CuSe. Our results show that the electrical conductivity of NLs in x (or y) direction is nearly 10{sup 6} orders of magnitude than z direction. Therefore, the NLs have very good hole conductive in x (or y) direction but their conductivity is ultra-low in z-axis.

  5. Competition between the pseudogap and superconductivity in the high-T(c) copper oxides.

    Science.gov (United States)

    Kondo, Takeshi; Khasanov, Rustem; Takeuchi, Tsunehiro; Schmalian, Jörg; Kaminski, Adam

    2009-01-15

    In a classical Bardeen-Cooper-Schrieffer superconductor, pairing and coherence of electrons are established simultaneously below the critical transition temperature (T(c)), giving rise to a gap in the electronic energy spectrum. In the high-T(c) copper oxide superconductors, however, a pseudogap extends above T(c). The relationship between the pseudogap and superconductivity is one of the central issues in this field. Spectral gaps arising from pairing precursors are qualitatively similar to those caused by competing electronic states, rendering a standard approach to their analysis inconclusive. The issue can be settled, however, by studying the correlation between the weights associated with the pseudogap and superconductivity spectral features. Here we report a study of two spectral weights using angle-resolved photoemission spectroscopy. The weight of the superconducting coherent peak increases away from the node following the trend of the superconducting gap, but starts to decrease in the antinodal region. This striking non-monotonicity reveals the presence of a competing state. We demonstrate a direct correlation, for different values of momenta and doping, between the loss in the low-energy spectral weight arising from the opening of the pseudogap and a decrease in the spectral weight associated with superconductivity. We therefore conclude that the pseudogap competes with the superconductivity by depleting the spectral weight available for pairing.

  6. Enhanced charge stripe order in superconducting La2-xBaxCuO4 in high magnetic fields

    Science.gov (United States)

    Huecker, M.; Zimmermann, M. V.; Xu, Z. J.; Wen, J. S.; Gu, G. D.; Tranquada, J. M.

    2013-03-01

    There is mounting evidence for a proximity of the superconducting ground state in the cuprates to competing states with static spin and/or charge density modulations. One such competing state is the spin and charge stripe phase in La2-xBaxCuO4. By means of high energy (100 keV) x-ray diffraction we have studied the effect of a high magnetic field (H||c) on the charge stripe order in a broad range of doping (0.095 <= x <= 0.155). We find that the field can significantly enhance the charge stripe order, but only at temperatures and dopings where it coexists with bulk superconductivity at zero field. The field also increases stripe correlations between the planes, which can result in an enhanced frustration of the interlayer Josephson coupling. Close to the famous x =1/8 compound, where zero field stripe order is pronounced and bulk superconductivity is suppressed, charge stripe order is independent of the field. The results imply that static stripe order and three-dimensionally coherent superconductivity are competing ground states. The work at Brookhaven was supported by the Office of Basic Energy Sciences, Division of Materials Science and Engineering, U.S. Department of Energy (DOE), under Contract No. DE-AC02-98CH10886.

  7. Relationships between oxygen content, modulation period and superconducting property of Bi-based superconducting oxides. Bi kei sankabtsu chodendotai ni okeru sanso ganryo, hencho kozo oyobi chodendo tokusei no sokan

    Energy Technology Data Exchange (ETDEWEB)

    Deshimaru, Y.; Shimizu, Y.; Miura, N.; Yamazoe, N. (Kyushu Univ., Fukuoka (Japan). Graduate School of Engineering Sciences); Hiroi, Z.; Bando, Y. (Kyoto Univ., Kyoto (Japan). Inst. for Chemical Research)

    1992-09-10

    Two (2223 and 2212) of three superconducting phases in the Pb-doped Bi-Sr-Ca-Cu-O (BSCCO) oxide superconductor were examined for their changes of crystal structures and superconducting properties with changing oxygen content. Their oxygen sorption behavior examined by the temperature-programmed-desorption method showed that both samples desorb trace amounts of oxygen in a temperature range of 350-600 centigrade and the behavior examined by the temperature-programmed oxidation method showed that they absorb (absorb) reversibly oxygen desorbed above in a range of 100-350 centigrade. The critical temperature to bear diamagnetism (Tc) of the 2223 sample fell from 111 K to 96 K as oxygen was desorbed up to 600 centigrade. However, Tc recovers reversibly to the initial value when oxygen was re-absorbed. Contrary to the 2223, the 2212 sample showed the opposite Tc change. Both samples increased in their c-axes lengths and their modulation periods and the changes were reversible respectively. It was pointed out that the Tc behaviors of both sample systems were dependent on the concentration of holes on the CuO2 surfaces. 33 refs., 9 figs.

  8. Superconductivity in the antiperovskite Dirac-metal oxide Sr3−xSnO

    Science.gov (United States)

    Oudah, Mohamed; Ikeda, Atsutoshi; Hausmann, Jan Niklas; Yonezawa, Shingo; Fukumoto, Toshiyuki; Kobayashi, Shingo; Sato, Masatoshi; Maeno, Yoshiteru

    2016-01-01

    Investigations of perovskite oxides triggered by the discovery of high-temperature and unconventional superconductors have had crucial roles in stimulating and guiding the development of modern condensed-matter physics. Antiperovskite oxides are charge-inverted counterpart materials to perovskite oxides, with unusual negative ionic states of a constituent metal. No superconductivity was reported among the antiperovskite oxides so far. Here we present the first superconducting antiperovskite oxide Sr3−xSnO with the transition temperature of around 5 K. Sr3SnO possesses Dirac points in its electronic structure, and we propose from theoretical analysis a possibility of a topological odd-parity superconductivity analogous to the superfluid 3He-B in moderately hole-doped Sr3−xSnO. We envision that this discovery of a new class of oxide superconductors will lead to a rapid progress in physics and chemistry of antiperovskite oxides consisting of unusual metallic anions. PMID:27941805

  9. Superconducting fluctuations: paraconductivity, excess Hall effect and magnetoconductivity in 2223-BiSrCaCuO thin films

    Energy Technology Data Exchange (ETDEWEB)

    Lang, W. (Ludwig Boltzmann Inst. fuer Festkoerperphysik, Wien (Austria) Inst. fuer Festkoerperphysik, Univ. Wien (Austria)); Kula, W. (Dept. of Electrical Engineering and Lab. for Laser Energetics, Univ. of Rochester, NY (United States) Inst. of Physics, Polish Academy of Sciences, Warszawa (Poland)); Sobolewski, R. (Dept. of Electrical Engineering and Lab. for Laser Energetics, Univ. of Rochester, NY (United States) Inst. of Physics, Polish Academy of Sciences, Warszawa (Poland))

    1994-02-01

    We report a detailed study of the influence of thermodynamic fluctuations of the superconducting order parameter on various normal-state transport properties in 2223-(Bi,Pb)SrCaCuO thin films at temperatures near the superconducting transition. Measurements of the electrical resistivity, the magnetoresistance and the Hall effect were analyzed with regard to fluctuation contributions, using theories for 2-dimensional, layered superconductors. We obtained a consistent set of parameters, which fit all magneto-transport measurements above 118 K, but observed a remarkable enhancement of both excess Hall effect and negative magnetoconductivity closer to T[sub c], whereas the zero-field fluctuation conductivity follows the theoretical predictions down to 110 K. No significant contributions from the indirect (Maki-Thompson) fluctuations process were found. (orig.)

  10. Magnetic proximity effect and superconducting triplet correlations at the cuprate superconductor and oxide spin valve interface

    Science.gov (United States)

    Ovsyannikov, G. A.; Constantinian, K. Y.; Demidov, V. V.; Khaydukov, Yu. N.

    2016-10-01

    A heterostructure consisting of a cuprate superconductor YBa2Cu3O7-δ and a ruthenate/manganite (SrRuO3/La0.7Sr0.3MnO3) spin valve was studied using SQUID magnetometry, ferromagnetic resonance, and neutron reflectometry. It is shown that because of the magnetic proximity effect a magnetic moment is excited in the superconducting portion of the heterostructure, whereas the magnetic moment in the spin valve becomes suppressed. The experimentally obtained value of a typical penetration depth of a magnetic moment into the superconductor is significantly greater than the coherence length of the cuprate superconductor, which indicates that the induced magnetic moment mechanism of Cu atoms is dominant. The mesastructure prepared by adding niobium film as a second superconducting electrode to the existing heterostructure, exhibited a superconducting current (dc Josephson effect) at interlayer thicknesses that are much greater than the coherence length of the ferromagnetic materials. The maximum of the critical current density dependence on the thickness of the spin valve material corresponds to the interlayer coherence length, which agrees with the theoretical predictions associated with spin-triplet pairing. The superconducting current is observed at magnetic fields that are two orders of magnitude greater than the field corresponding to the occurrence of one magnetic flux quantum in the mesastructure. The ratio of the second harmonic of the current-phase dependence of the mesastructure superconducting current to the first, determined according to the dependence of the Shapiro steps on the amplitude of microwave exposure, did not exceed 50%.

  11. Coming across a novel copper oxide 2D framework during the oxidation of Cu(111).

    Science.gov (United States)

    Matencio, Sonia; Barrena, Esther; Ocal, Carmen

    2016-12-07

    Two dimensional copper oxides obtained on Cu(111) by air-enriched argon sputtering plus annealing have been measured at room temperature by means of scanning tunneling microscopy (STM) and atomic force microscopy (AFM) under ultra-high vacuum (UHV) conditions. Depending on the oxygen content different oxide frameworks and diverse stoichiometric metal/oxide interfaces exist. In particular, we report on a novel open honeycomb structure with a large unit cell which is modeled as a two dimensional network made out of Cu3O units. This lattice coexists with other oxide structures richer in oxygen and is suggested to develop towards these denser phases by oxygen incorporation.

  12. Preparation of superconducting Bi-Sr-Ca-Cu-O thin films by sequential electron beam evaporation and oxygen annealing

    Energy Technology Data Exchange (ETDEWEB)

    Steinbeck, J.; Tsaur, B.; Anderson, A.C.; Strauss, A.J.

    1989-01-30

    Superconducting films with nominal composition Bi/sub 2/Sr/sub 2/Ca/sub 1/Cu/sub 2/O/sub x/ have been prepared on <100> MgO substrates by sequential electron beam evaporation of Cu, Bi, and Sr/sub 2/3/ Ca/sub 1/3/ F/sub 2/, followed by annealing in flowing wet, then dry, O/sub 2/. X-ray diffraction data show that the films contain the two Bi-Sr-Ca-Cu-O phases that have been identified in the literature as a superconducting phase with capprox.31 A and a semiconducting phase with capprox.24 A. Both phases are strongly textured with the c axis perpendicular to the substrate. For the best film, which was annealed at 870 /sup 0/C for 30 min, zero resistance was observed at 90 K, and the critical current density increased from 0.8 x 10/sup 5/ A/cm/sup 2/ at 77 K to 2.3 x 10/sup 5/ A/cm/sup 2/ at 4.2 K.

  13. The Occurrence of Superconductivity in the TlBa2CuO5-δ-Type (1021) System

    Science.gov (United States)

    Ku, H. C.; Tai, M. F.; Shi, J. B.; Shieh, M. J.; Hsu, S. W.; Hwang, G. H.; Ling, D. C.; Watson-Yang, T. J.; Lin, T. Y.

    1989-06-01

    Stable and reproducible superconductivity in the Tl(Ba2-xLax)CuO5-δ (0.0≤x≤0.6) system with the tetragonal TlBa2CuO5-δ-type (1021) structure was reported. A Prototype compound TlBa2CuO5-δ had shown a metastable superconducting onset around 25 K, with zero resistivity at 10 K. With partial substitution of La for Ba ions, Tc (50% resistivity drop) increases to 45 K, Tc0 (zero resistivity) to 42 K and onset around 50 K. A diamagnetic signal was observed with onset as high as 57 K. Tetragonal lattice parameters decrease with the increasing La concentration due to the partial replacement of larger Ba2+ ions by smaller La3+ ions. The Pairing field energy of 170 K and electron-elementary excitation coupling constant λ of 0.76 were derived from the BCS-like Tc formula through comparison with other single Tl-O layer systems TlCan-1Ba2CunO2n+3-δ.

  14. Korea's developmental program for superconductivity

    Science.gov (United States)

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

    1995-01-01

    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.

  15. Superconducting transistor

    Science.gov (United States)

    Gray, Kenneth E.

    1979-01-01

    A superconducting transistor is formed by disposing three thin films of superconducting material in a planar parallel arrangement and insulating the films from each other by layers of insulating oxides to form two tunnel junctions. One junction is biased above twice the superconducting energy gap and the other is biased at less than twice the superconducting energy gap. Injection of quasiparticles into the center film by one junction provides a current gain in the second junction.

  16. Carbon Supported Oxide-Rich Pd-Cu Bimetallic Electrocatalysts for Ethanol Electrooxidation in Alkaline Media Enhanced by Cu/CuOx

    Directory of Open Access Journals (Sweden)

    Zengfeng Guo

    2016-04-01

    Full Text Available Different proportions of oxide-rich PdCu/C nanoparticle catalysts were prepared by the NaBH4 reduction method, and their compositions were tuned by the molar ratios of the metal precursors. Among them, oxide-rich Pd0.9Cu0.1/C (Pd:Cu = 9:1, metal atomic ratio exhibits the highest electrocatalytic activity for ethanol oxidation reaction (EOR in alkaline media. X-ray photoelectron spectroscopy (XPS and high resolution transmission electron microscopy (HRTEM confirmed the existence of both Cu and CuOx in the as-prepared Pd0.9Cu0.1/C. About 74% of the Cu atoms are in their oxide form (CuO or Cu2O. Besides the synergistic effect of Cu, CuOx existed in the Pd-Cu bimetallic nanoparticles works as a promoter for the EOR. The decreased Pd 3d electron density disclosed by XPS is ascribed to the formation of CuOx and the spill-over of oxygen-containing species from CuOx to Pd. The low Pd 3d electron density will decrease the adsorption of CH3COads intermediates. As a result, the electrocatalytic activity is enhanced. The onset potential of oxide-rich Pd0.9Cu0.1/C is negative shifted 150 mV compared to Pd/C. The oxide-rich Pd0.9Cu0.1/C also exhibited high stability, which indicated that it is a candidate for the anode of direct ethanol fuel cells (DEFCs.

  17. From quantum matter to high-temperature superconductivity in copper oxides.

    Science.gov (United States)

    Keimer, B; Kivelson, S A; Norman, M R; Uchida, S; Zaanen, J

    2015-02-12

    The discovery of high-temperature superconductivity in the copper oxides in 1986 triggered a huge amount of innovative scientific inquiry. In the almost three decades since, much has been learned about the novel forms of quantum matter that are exhibited in these strongly correlated electron systems. A qualitative understanding of the nature of the superconducting state itself has been achieved. However, unresolved issues include the astonishing complexity of the phase diagram, the unprecedented prominence of various forms of collective fluctuations, and the simplicity and insensitivity to material details of the 'normal' state at elevated temperatures.

  18. Enhanced formic acid oxidation on Cu-Pd nanoparticles

    Science.gov (United States)

    Dai, Lin; Zou, Shouzhong

    Developing catalysts with high activity and high resistance to surface poisoning remains a challenge in direct formic acid fuel cell research. In this work, copper-palladium nanoparticles were formed through a galvanic replacement process. After electrochemically selective dissolution of surface Cu, Pd-enriched Cu-Pd nanoparticles were formed. These particles exhibit much higher formic acid oxidation activities than that on pure Pd nanoparticles, and they are much more resistant to the surface poisoning. Possible mechanisms of catalytic activity enhancement are briefly discussed.

  19. Tailoring oxides of copper-Cu{sub 2}O and CuO nanoparticles and evaluation of organic dyes degradation

    Energy Technology Data Exchange (ETDEWEB)

    Raghav, Ragini; Aggarwal, Priyanka; Srivastava, Sudha, E-mail: sudha.srivastava@jiit.ac.in [Department of Biotechnology, Jaypee Institute of Information Technology, A-10, Sector-62, Noida-201307,Uttar Pradesh (India)

    2016-04-13

    We report a simple one-pot colloidal synthesis strategy tailoring cuprous or cupric nano-oxides in pure state. NaOH provided alkaline conditions (pH 12.5 -13) for nano-oxides formation, while its concentration regulated the oxidation state of the nano-oxides. The morphological, structural and optical properties of synthesized Cu{sub 2}O and CuO nanoparticles were studied by transmission electron microscopy (TEM), X-Ray diffraction (XRD) and UV-vis spectroscopy. Dye degradation capability of CuO and Cu2O nanoparticles was evaluated using four organic dyes - Malachite green, Methylene blue, Methyl orange and Methyl red. The results demonstrate effective degradation of all four dyes employing with almost comparable activity both Cu{sub 2}O and CuO nanoparticles.

  20. Tailoring oxides of copper-Cu2O and CuO nanoparticles and evaluation of organic dyes degradation

    Science.gov (United States)

    Raghav, Ragini; Aggarwal, Priyanka; Srivastava, Sudha

    2016-04-01

    We report a simple one-pot colloidal synthesis strategy tailoring cuprous or cupric nano-oxides in pure state. NaOH provided alkaline conditions (pH 12.5 -13) for nano-oxides formation, while its concentration regulated the oxidation state of the nano-oxides. The morphological, structural and optical properties of synthesized Cu2O and CuO nanoparticles were studied by transmission electron microscopy (TEM), X-Ray diffraction (XRD) and UV-vis spectroscopy. Dye degradation capability of CuO and Cu2O nanoparticles was evaluated using four organic dyes - Malachite green, Methylene blue, Methyl orange and Methyl red. The results demonstrate effective degradation of all four dyes employing with almost comparable activity both Cu2O and CuO nanoparticles.

  1. Oxidation of two-phase Cu-Cr alloys with different microstructures

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The oxidation of PM Cu-50Cr, MA Cu-40Cr and MS Cu-40Cr alloys at 800  ℃ in 0.1  MPa O2 was studied. The most important difference of their oxidation behaviors is the formation of an exclusive chromia scale on the surface of the MS Cu-40Cr alloy and a continuous chromia layer beneath an outer CuO layer corresponding MA Cu-40Cr alloy, while a complex scale composing of CuO, Cu2O, Cu2Cr2O4 and Cr2O3 formed on the PM Cu-50Cr alloy. This result implies that alloy microstructure affects their oxidation behaviors largely. Microcrystalline structure provides numerous diffusion paths for reactive component chromium, shorter diffusion distance and rapid dissolution of Cr-riched second phase. All these favor the exclusive formation of the most stable oxide.

  2. Nodal quasiparticle lifetime in the superconducting state of Bi(2)Sr(2)CaCu(2)O(8+delta)

    Science.gov (United States)

    Corson; Orenstein; Oh; O'Donnell; Eckstein

    2000-09-18

    We have measured the complex conductivity sigma of a Bi(2)Sr(2)CaCu(2)O(8+delta) thin film between 0.2 and 0.8 THz. We find sigma in the superconducting state to be well described as the sum of contributions from quasiparticles, condensate, and order parameter fluctuations which draw 30% of the spectral weight from the condensate. An analysis based on this decomposition yields a quasiparticle scattering rate on the order of k(B)T/Planck's over 2pi for temperatures below T(c).

  3. High field performance of superconducting magnets using powder metallurgy processed Cu-Nb-Sn and Nb-Al

    Energy Technology Data Exchange (ETDEWEB)

    Zaleski, A.J.; Foner, S.

    1984-06-01

    Small superconducting magnets were fabricated with powder metallurgy processed Nb-Al wire and with powder metallurgy processed multistrand Cu-Nb--Sn wire with 19 tin cores. Tests in a background field of up to 15 T showed that short sample characteristics were achieved for three coils. Upper limits of resistivity were established for both powder metallurgy processed wires. The reacted wires in the magnets gave upper limits of resistivity at 10 T of less than 1.4 x 10/sup -14/ ..cap omega.. cm for the Nb/sub 3/Sn wire, and less than 9 x 10/sup -13/ ..cap omega.. cm for the Nb-Al wire.

  4. Effects of lattice disorder on the superconducting properties of YBa 2Cu 3O 6.9 films

    Science.gov (United States)

    Gauzzi, Andrea; Pavuna, Davor

    1994-12-01

    We report on striking sensitivity of the superconducting properties of ion-beam sputtered YBa 2Cu 3O 6.9 films to the lattice disorder (induced by varying growth temperatures). Tc decreases with increasing disorder, while the width of the resistive transition and the normal state resistivity increase. We give a quantitative significance to this trend by expressing the degree of the disorder in terms of the lattice coherence length rc is extracted from the width of X-ray diffraction rocking curves. We find that Tc saturates to the maximum of ∼ 92 K for rc > 10 nm.

  5. Superconductivity in 2-2-3 Y2Ba2Cu3O(sub 8+ delta)

    Science.gov (United States)

    Joshi, H. H.; Baldha, G. J.; Jotania, R. B.; Joshi, S. M.; Mohan, H.; Pandya, P. B.; Pandya, H. N.; Kulkarni, R. G.

    1990-01-01

    Researchers synthesized a new high T(sub c) 2-2-3 superconductor (Y2Ba2Cu3O8+delta) by a special preparation technique and characterized it by ac-susceptibility measurements. Diamagnetism and Meissner effect sets in at low fields and superconducting transition onsets at 90 K. The systematic investigation of the real and imaginary components of ac-susceptibility as a function of temperature and applied ac magnetic field reveals that the magnetic behavior is that of a granular type superconductor.

  6. Features of pseudogap and superconductivity states of YBa sub 2 Cu sub 3 O sub 7 sub - sub x

    CERN Document Server

    Misochko, O V; Dekorsy, T; Helm, M

    2002-01-01

    The relaxation dynamics of the lattice and low-energy quasi-particles of the YBa sub 2 Cu sub 3 O sub 7 sub - sub x superconductor is studied through the light reflection method within the wide temperature range. It is shown that for T > T sub c there exist two areas of temperature with qualitatively and quantitatively different excitation dynamics and the transition between these areas is of the hysteresis character. It is established also, that the character of the change in the relaxation dynamics of the charge carriers in the superconducting state indicates the anisotropic gap with zeroes on the Fermi surface

  7. Superconductivity at 43 K in Samarium-arsenide Oxides $SmFeAsO_{1-x}F_x$

    OpenAIRE

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

    2008-01-01

    Since the discovery of high-transition temperature ($T_c$) superconductivity in layered copper oxides, extensive efforts have been devoted to explore the higher $T_c$ superconductivity. However, the $T_c$ higher than 40 K can be obtained only in the copper oxide superconductors so far. The highest reported value of $T_c$ for non-copper-oxide bulk superconductivity is 39 K in $MgB_2$.\\cite{jun} The $T_c$ of about 40 K is close to or above the theoretical value predicted from BCS theory.\\cite{m...

  8. Coulomb-oscillator explanation of striped STM images of superconductive copper oxides

    CERN Document Server

    Bucher, Manfred

    2013-01-01

    Asymmetric scanning tunneling microscopy (STM) of the CuO2 plane of Ca2-xNaxCuO2Cl2, x = 0.125, shows a square domain structure with edge length four times the compound's lattice constant a0 (Cu-O-Cu distance). The domain structure is a direct consequence of the 4a0 by 4a0 superlattice formed by vertical Na+ pairs (oriented parallel to the crystal's c axis) that substitute Ca2+ ions. The surrounding O2- ions are displaced away from, and the Cu2+ ions toward the Na+ pairs. Contrary to the fourfold symmetry of the CuO2 plane, the stable displacement configuration has a twofold symmetry, dominated by large and, respectively, small displacement of opposite O2- ions being nearest neighbors to each vertical Na+ pair. The ion displacements give rise to sufficient squeeze of certain O2- ions that, by the Coulomb-oscillator model of superconductivity, prevents lateral overswing of their excited 3s electrons. The axial 3s oscillations are predominantly oriented in the directions of O2- ion displacements. The observed l...

  9. Relation of Structure and Superconductivity in Self-Compensating Y1-xCaxBa2-xLaxCu3Oy

    Institute of Scientific and Technical Information of China (English)

    SUN Xue-Feng; YU Jing; WANG Fa; ZHANG Han

    2006-01-01

    @@ The self-compensating compound of Y1-xCaxBa2-xLaxCu3Oy is synthesized through a solid-state reaction method with x from 0.25 to 0.55. Structural and superconducting properties have been investigated by x-ray diffraction, Rietveld refinement, and dc magnetization measurement, respectively. The impure peaks appear when x is more than 0.5 in the diffraction pattern. Orthorhombic-tetragonal transition occurs at x=0.45.Some local structural parameters, such as Cu(1)-O(4), Cu(2)-O(4) bond lengths, change randomly in a narrow range. The relationship between the character of (Ba/La)-O plane and Tc is rather interesting. We attribute the behaviour of superconductivity to the joint effects of these local structural parameters. The results give the evidence that the influence of the structural change on superconductivity is essential and independent of carrier concentration.

  10. Spin-fluctuation mediated superconductivity and magnetic order in the cuprate La1.88Sr0.12CuO4

    DEFF Research Database (Denmark)

    Rømer, Astrid Tranum

    High-temperature superconductivity in cuprates emerges as one out of many electronic phases when doping the antiferromagnetic Mott insulator La2CuO4 away from half _lling. The description of the superconducting phase is therefore complicated by intertwined electronic orders that compete...... with superconductivity. However, it is possible that the tendency towards additional ordering phenomena is a necessary condition for unconventional superconductivity to develop. Indeed most superconductors discovered throughout the last 29 years, including also the recently discovered class of iron-based superconductors......, show a very rich electronic phase diagram. A common feature that characterizes both cuprates, heavy fermions, and iron pnictides is the proximity to magnetic order. Therefore, the idea of spin-uctuation mediated pairing is a popular paradigm proposed for unconventional superconductivity. A _ngerprint...

  11. Cu patterning on Si substrate using solution-processed Ti-Cu oxide films and electroless plating

    Science.gov (United States)

    Miyazeki, Yusuke; Horiuchi, Yoshio; Noh, Joo-Hyong; Cordonier, Christopher E. J.; Honma, Hideo; Arakawa, Taro

    2016-09-01

    We demonstrated for the first time the Cu patterning on Si using Ti and Cu oxide (TiCu-ox) films patterned by photolithography and electroless plating without etching or surface modification. The TiCu-ox films had a porous structure and acted as adhesion layers. The TiCu-ox films were patterned by photolithography on Si and glass for comparison, followed by Cu deposition by electroless plating. Fine Cu patterns on the patterned TiCu-ox films were formed. The smallest line/space widths on glass and Si were 3.2/0.8 and 3.6/4.4 µm, respectively. The deposited Cu layers had high adhesion strength and low sheet resistance.

  12. Temperature-dependence of the superconducting condensate and gap in Bi 2Sr 2Ca 1Cu 2O 8+ z

    Science.gov (United States)

    Ma, Jian; Quitmann, C.; Kelley, R. J.; Alméras, P.; Berger, H.; Margaritondo, G.; Onellion, M.

    1994-12-01

    Using high energy resolution angle-resolved photoemission, we have measured both the superconducting gap and the photoemission superconducting condensate spectral area of Bi 2Sr 2Ca 1Cu 1O 8+ z as a function of temperature in two different locations of the Brillouin zone. We found that the size of superconducting gap along the Γ- X direction decreases to values indistinguishable from zero for which the gap retains virtually full value along the Γ - M¯ direction. The increased gap anisotropy with increasing temperature is in contrast to what happens for conventional anisotropic superconductors such as lead.

  13. Temperature-dependence of the superconducting condensate and gap in Bi2Sr2Ca1Cu2O8+x

    Science.gov (United States)

    Quitmann, C.; Kelly, R. J.; Onellion, M.; Alméras, P.; Berger, H.; Margaritondo, G.

    1994-12-01

    Using high energy resolution angle-resolved photoemission, we have measured both the superconducting gap and the photoemission superconducting condensate spectral area of Bi2Sr2Ca1Cu1O8+x as a function of temperature in two different locations of the Brillouin zone. We found that the size of superconducting gap along the Γ - X direction decreases to values indistinguishable from zero for which the gap retains virtually full value along the Γ - M direction. The increased gap anisotropy with increasing temperature is in contrast to what happens for conventional anisotropic superconductors such as lead.>

  14. Coexistence of, and Competition between, Superconductivity and Charge-Stripe Order in La1.6-xNd0.4SrxCuO4

    Science.gov (United States)

    Tranquada, J. M.; Axe, J. D.; Ichikawa, N.; Moodenbaugh, A. R.; Nakamura, Y.; Uchida, S.

    1997-01-01

    Previously we have presented evidence for stripe order of holes and spins in La1.6-xNd0.4SrxCuO4 with x = 0.12. Here we show, via neutron diffraction measurements of magnetic scattering, that similar order occurs in crystals with x = 0.15 and 0.20. Zero-field-cooled magnetization measurements show that all three compositions are also superconducting, with the superconducting transition temperature increasing as the low-temperature staggered magnetization decreases. These results directly demonstrate an intimate connection between stripe correlations and superconductivity.

  15. Photoemission search for the superconducting energy gap of high-T/sub c/YBa/sub 2/Cu/sub 3/O/sub 7/

    Energy Technology Data Exchange (ETDEWEB)

    Moog, E.R.; Bader, S.D.; Arko, A.J.; Flandermeyer, B.K.

    1987-10-01

    Photoemission data (h..nu.. = 21.2 eV) are reported for the high-T/sub c/ superconductor YBa/sub 2/Cu/sub 3/O/sub 7/ above and well below T/sub c/ and examined for effects due to the formation of the superconducting energy gap. To guide expectations, simulations are also presented based on a BCS quasiparticle excitation expression broadened by a 30-meV experimental resolution. Comparison of the experimental Fermi-edge spectra with the calculations indicates either that the surface region probed is not superconducting or that the superconductivity is in the extreme gapless limit.

  16. Development of a superconducting joint between a GdBa2Cu3O7-δ-coated conductor and YBa2Cu3O7-δ bulk: towards a superconducting joint between RE (Rare Earth) Ba2Cu3O7-δ-coated conductors

    Science.gov (United States)

    Jin, Xinzhe; Yanagisawa, Yoshinori; Maeda, Hideaki; Takano, Yoshiki

    2015-07-01

    We have started to develop a superconducting bridge joint between two GdBa2Cu3O7-δ (Gd123)-coated conductors, where both conductors are placed in an end-to-end arrangement on the surface of a melt-textured YBCO (including Y2BaCuO5 and YBa2Cu3O7-δ) bulk, which acts as a superconducting medium between the coated conductors. As a first step in the development, one half of the bridge joint assembly was modeled and investigated. Experimental results achieved are as follows: (a) the higher-melting-temperature textured Gd123-coated conductor acts as a seed for the melt texture of the YBa2Cu3O7-δ (Y123) bulk, and (b) the superconducting phase continues across the Y123/Gd123 boundary. The critical current of the joint model is 10 A, which is about 10% of the original Gd123-coated conductor, at 77 K in a self-magnetic field. These results are considered to be extensible to the superconducting bridge joint between the Gd123-coated conductors.

  17. Charge order, metallic behavior, and superconductivity in La2-xBaxCuO4 with x=1/8.

    Science.gov (United States)

    Homes, C C; Dordevic, S V; Gu, G D; Li, Q; Valla, T; Tranquada, J M

    2006-06-30

    The ab-plane optical properties of a cleaved single crystal of La2-xBaxCuO4 for x=1/8 (Tc approximately =2.4 K) have been measured over a wide frequency and temperature range. The low-frequency conductivity is Drude-like and shows a metallic response with decreasing temperature. However, below approximately =60 K, corresponding to the onset of charge-stripe order, there is a rapid loss of spectral weight below about 40 meV. The behavior is quite different from that typically associated with the pseudogap in the normal state of the cuprates. Instead, the gapping of the normal-state single-particle excitations looks surprisingly similar to that observed in superconducting La2-xSrxCuO4, including the presence of a residual Drude peak with reduced weight.

  18. Unusual physical and chemical properties of Cu in Ce(1-x)Cu(x)O(2) oxides.

    Science.gov (United States)

    Wang, Xianqin; Rodriguez, José A; Hanson, Jonathan C; Gamarra, Daniel; Martínez-Arias, Arturo; Fernandez-García, Marcos

    2005-10-27

    The structural and electronic properties of Ce(1-x)Cu(x)O(2) nano systems prepared by a reverse microemulsion method were characterized with synchrotron-based X-ray diffraction, X-ray absorption spectroscopy, Raman spectroscopy, and density functional calculations. The Cu atoms embedded in ceria had an oxidation state higher than those of the cations in Cu(2)O or CuO. The lattice of the Ce(1)(-x)Cu(x)O(2) systems still adopted a fluorite-type structure, but it was highly distorted with multiple cation-oxygen distances with respect to the single cation-oxygen bond distance seen in pure ceria. The doping of CeO(2) with copper introduced a large strain into the oxide lattice and favored the formation of O vacancies, leading to a Ce(1-x)Cu(x)O(2-y) stoichiometry for our materials. Cu approached the planar geometry characteristic of Cu(II) oxides, but with a strongly perturbed local order. The chemical activities of the Ce(1-x)Cu(x)O(2) nanoparticles were tested using the reactions with H(2) and O(2) as probes. During the reduction in hydrogen, an induction time was observed and became shorter after raising the reaction temperature. The fraction of copper that could be reduced in the Ce(1-x)Cu(x)O(2) oxides also depended strongly on the reaction temperature. A comparison with data for the reduction of pure copper oxides indicated that the copper embedded in ceria was much more difficult to reduce. The reduction of the Ce(1-x)Cu(x)O(2) nanoparticles was rather reversible, without the generation of a significant amount of CuO or Cu(2)O phases during reoxidation. This reversible process demonstrates the unusual structural and chemical properties of the Cu-doped ceria materials.

  19. Microstructural aspects of joining superconductive components using (RE)Ba{sub 2}Cu{sub 3}O{sub 7-x} solder

    Energy Technology Data Exchange (ETDEWEB)

    Schmitz, G.J.; Tigges, A.; Schmidt, J.C. [ACCESS e. V., Intzestr. 5, D-52072 Aachen (Germany)

    1998-01-01

    Investigations of superconductive joints were performed using an infiltration technique. Gaps between two domains of YBa{sub 2}Cu{sub 3}O{sub 7-x} were prepared mechanically and subsequently filled with Y{sub 2}BaCuO{sub 5} powder. Barium cuprate liquid prepared by the peritectic decomposition of YbBa{sub 2}Cu{sub 3}O{sub 7-x} was infiltrated into the gap between the two YBa{sub 2}Cu{sub 3}O{sub 7-x} domains. Microstructural analysis indicates a local epitaxy of the solder. (author)

  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

    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.

  2. Formation of the 110-K superconducting phase in Pb-doped Bi-Sr-Ca-Cu-O thin films

    Energy Technology Data Exchange (ETDEWEB)

    Kula, W.; Sobolewski, R.; Gorecka, J.; Lewandowski, S.J. (Instytut Fizyki, Polska Akademia Nauk, Al. Lotnikow 32/46, PL-02668 Warszawa (Poland))

    1991-09-15

    Investigation of the 110-K Bi{sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub {ital x}} phase formation in superconducting thin films of Bi-based cuprates is reported. The films were dc magnetron sputtered from single Bi(Pb)-Sr-Ca-Cu-O targets of various stoichiometries, and subsequently annealed in air at high temperatures. The influence of the initial Pb content, annealing conditions, as well as the substrate material on the growth of the 110-K phase was investigated. We found that the films, fully superconducting above 100 K could be reproducibly fabricated on various dielectric substrates from Pb-rich targets by optimizing annealing conditions for each initial Pb/Bi ratio. Heavy Pb doping considerably accelerated formation of the 110-K phase, reducing the film annealing time to less than 1 h. Films containing, according to the x-ray measurement, more than 90% of the 110-K phase were obtained on MgO substrates, after sputtering from the Bi{sub 2}Pb{sub 2.5}Sr{sub 2}Ca{sub 2.15}Cu{sub 3.3}O{sub {ital x}} target and annealing in air for 1 h at 870 {degree}C. The films were {ital c}-axis oriented, with 4.5-K-wide superconducting transition, and zero resistivity at 106 K. Their critical current density was 2 {times} 10{sup 2} A/cm{sup 2} at 90 K, and above 10{sup 4} A/cm{sup 2} below 60 K. The growth of the 110-K phase on epitaxial substrates, such as CaNdAlO{sub 4} and SrTiO{sub 3}, was considerably deteriorated, and the presence of the 80- and 10-K phases was detected. Nevertheless, the best films deposited on these substrates were fully superconducting at 104 K and exhibited critical current densities above 2 {times} 10{sup 5} A/cm{sup 2} below 60 K{minus}one order of magnitude greater than the films deposited on MgO.

  3. Superconducting fluctuations in Bi2Sr2Ca2Cu3Ox thin films: Paraconductivity, excess Hall effect, and magnetoconductivity

    Science.gov (United States)

    Lang, W.; Heine, G.; Kula, W.; Sobolewski, Roman

    1995-04-01

    A detailed study of normal-state magnetotransport properties in (Bi,Pb)2Sr2Ca2Cu3Ox thin films with a zero-resistance critical temperature Tc0=105 K prepared by dc-magnetron sputtering on MgO substrates is reported. Measurements of the electrical resistivity, the magnetoresistance, and the Hall effect are analyzed with regard to contributions of the superconducting order-parameter thermodynamic fluctuations, using theories for two-dimensional, layered superconductors. We have obtained a consistent set of parameters, i.e., the in-plane coherence length ξab(0)=1.6 nm, the out-of-plane coherence length ξc(0)=0.14 nm, and the electron-hole asymmetry parameter β=-0.38. At temperatures below 118 K, we observe a remarkable enhancement (above theoretical predictions) of both the excess Hall effect and magnetoconductivity, whereas no such effect is detected for the zero-field paraconductivity. The above anomalies are attributed to a nonuniform critical temperature distribution inside our samples and can be well explained assuming a Gaussian distribution of Tc's with a standard deviation δTc=2.3 K. The excess Hall effect caused by superconducting fluctuations is negative in the entire accessible temperature range, which indicates, together with the paraconductivity and magnetoconductivity results that the indirect (Maki-Thompson) fluctuation process for (Bi,Pb)2Sr2Ca2Cu3Ox is vanishingly small at temperatures from Tc to 130 K.

  4. Optically induced lattice deformations, electronic structure changes, and enhanced superconductivity in YBa2Cu3O6.48

    Directory of Open Access Journals (Sweden)

    R. Mankowsky

    2017-07-01

    Full Text Available Resonant optical excitation of apical oxygen vibrational modes in the normal state of underdoped YBa2Cu3O6+x induces a transient state with optical properties similar to those of the equilibrium superconducting state. Amongst these, a divergent imaginary conductivity and a plasma edge are transiently observed in the photo-stimulated state. Femtosecond hard x-ray diffraction experiments have been used in the past to identify the transient crystal structure in this non-equilibrium state. Here, we start from these crystallographic features and theoretically predict the corresponding electronic rearrangements that accompany these structural deformations. Using density functional theory, we predict enhanced hole-doping of the CuO2 planes. The empty chain Cu dy2-z2 orbital is calculated to strongly reduce in energy, which would increase c-axis transport and potentially enhance the interlayer Josephson coupling as observed in the THz-frequency response. From these results, we calculate changes in the soft x-ray absorption spectra at the Cu L-edge. Femtosecond x-ray pulses from a free electron laser are used to probe changes in absorption at two photon energies along this spectrum and provide data consistent with these predictions.

  5. Microstructure Analysis of Internally Oxidized Cu-C Composite

    Directory of Open Access Journals (Sweden)

    Rudolf, R.

    2006-01-01

    Full Text Available On the basis of experimentally obtained data, it was established that submicron-size bubbles are formed by the internal oxidation of Cu-C composite with fine dispersed graphite particles. They are homogeneously distributed in the Cu-matrix. This process starts with the dissolution of oxygen into the metal at the free surfaces, and continues with the diffusion of oxygen atoms into the volume of copper crystal lattice where they react with the graphite particles. The reactions of dissolved oxygen with carbon yield the gas products (CO2, CO, which cannot be dissolved in the crystal lattice of the matrix. The gas molecules, which are enclosed in the space previously occupied by the graphite, have a greater specific volume than the solid graphite. Consequently, compressive stresses arise in the copper matrix around the bubbles. The interaction of these stress fields with gliding dislocations during loading could improve the mechanical properties of the copper. The internal oxidation kinetic in Cu-C composite depends on the diffusion of oxygen in the copper matrix, and the penetration depth of the internal oxidation front indicates the parabolic nature of the process.

  6. Optical and electrical properties of Cu-based all oxide semi-transparent photodetector

    Science.gov (United States)

    Kim, Hong-Sik; Patel, Malkeshkumar; Yadav, Pankaj; Kim, Joondong; Sohn, Ahrum; Kim, Dong-Wook

    2016-09-01

    Zero-bias operating Cu oxide-based photodetector was achieved by using large-scale available sputtering method. Cu oxide (Cu2O or CuO) was used as p-type transparent layer to form a heterojunction by contacting n-type ZnO layer. All metal-oxide materials were employed to realize transparent device at room temperature and showed a high transparency (>75% at 600 nm) with excellent photoresponses. The structural, morphological, optical, and electrical properties of Cu oxides of CuO and Cu2O are evaluated in depth by UV-visible spectrometer, X-ray diffraction, scanning electron microscopy, atomic force microscopy, Kelvin probe force microscopy, and Hall measurements. We may suggest a route of high-functional Cu oxide-based photoelectric devices for the applications in flexible and transparent electronics.

  7. Stripe Order in Superconducting La2−xBaxCuO4 (0.095 x 0.155)

    Energy Technology Data Exchange (ETDEWEB)

    Hucker, M.; Zimmermann, M.v.; Gu, G.D.; Xu, Z.J.; Wen, J.S.; Xu, G.; Kang, H.J.; Zheludev, A.; Tranquada, J.M.

    2011-03-01

    The correlations between stripe order, superconductivity, and crystal structure in La{sub 2-x}Ba{sub x}CuO{sub 4} single crystals have been studied by means of x-ray and neutron diffraction as well as static magnetization measurements. The derived phase diagram shows that charge stripe order (CO) coexists with bulk superconductivity in a broad range of doping around x=1/8, although the CO order parameter and correlation length fall off quickly for x {ne} 1/8. Except for x=0.155, the onset of CO always coincides with the transition between the orthorhombic and the tetragonal or less orthorhombic low-temperature structures. The CO transition evolves from a sharp drop at low x to a more gradual transition at higher x, eventually falling below the structural phase boundary for optimum doping. With respect to the interlayer CO correlations, we find no qualitative change of the stripe stacking order as a function of doping, and in-plane and out-of-plane correlations disappear simultaneously at the transition. Similarly to the CO, the spin stripe order (SO) is also most pronounced at x=1/8. Truly static SO sets in below the CO and coincides with the first appearance of in-plane superconducting correlations at temperatures significantly above the bulk transition to superconductivity (SC). Indications that bulk SC causes a reduction of the spin or charge stripe order could not be identified. We argue that CO is the dominant order that is compatible with SC pairing but competes with SC phase coherence. Comparing our results with data from the literature, we find good agreement if all results are plotted as a function of x' instead of the nominal x, where x' represents an estimate of the actual Ba content, extracted from the doping dependence of the structural transition between the orthorhombic phase and the tetragonal high-temperature phase.

  8. Superhydrophilicity and antibacterial property of a Cu-dotted oxide coating surface

    Directory of Open Access Journals (Sweden)

    Nie Yining

    2010-09-01

    Full Text Available Abstract Background Aluminum-made settings are widely used in healthcare, schools, public facilities and transit systems. Frequently-touched surfaces of those settings are likely to harbour bacteria and be a potential source of infection. One method to utilize the effectiveness of copper (Cu in eliminating pathogens for these surfaces would be to coat the aluminum (Al items with a Cu coating. However, such a combination of Cu and Al metals is susceptible to galvanic corrosion because of their different electrochemical potentials. Methods In this work, a new approach was proposed in which electrolytic plasma oxidation (EPO of Al was used to form an oxide surface layer followed by electroplating of Cu metal on the top of the oxide layer. The oxide was designed to function as a corrosion protective and biocompatible layer, and the Cu in the form of dots was utilized as an antibacterial material. The antibacterial property enhanced by superhydrophilicity of the Cu-dotted oxide coating was evaluated. Results A superhydrophilic surface was successfully prepared using electrolytic plasma oxidation of aluminum (Al followed by electroplating of copper (Cu in a Cu-dotted form. Both Cu plate and Cu-dotted oxide surfaces had excellent antimicrobial activities against E. coli ATCC 25922, methicillin-resistant Staphylococcus aureus (MRSA ATCC 43300 and vancomycin-resistant Enterococcus faecium (VRE ATCC 51299. However, its Cu-dotted surface morphology allowed the Cu-dotted oxide surface to be more antibacterial than the smooth Cu plate surface. The enhanced antibacterial property was attributed to the superhydrophilic behaviour of the Cu-dotted oxide surface that allowed the bacteria to have a more effective killing contact with Cu due to spreading of the bacterial suspension media. Conclusion The superhydrophilic Cu-dotted oxide coating surface provided an effective method of controlling bacterial growth and survival on contact surfaces and thus reduces the

  9. Superconducting and related oxides: Physics and nanoengineering 3

    Energy Technology Data Exchange (ETDEWEB)

    Pavuna, D.; Bozovic, I. [eds.

    1998-12-31

    This volume is composed of 51 papers presented at the symposium. Topics covered are: physical properties of oxide superconductors; thin film growth and properties; and device physics and new concepts.

  10. Enhancing triplet superconductivity by the proximity to a singlet superconductor in oxide heterostructures

    Science.gov (United States)

    Horsdal, Mats; Khaliullin, Giniyat; Hyart, Timo; Rosenow, Bernd

    2016-06-01

    We show how in principle a coherent coupling between two superconductors of opposite parity can be realized in a three-layer oxide heterostructure. Due to strong intraionic spin-orbit coupling in the middle layer, singlet Cooper pairs are converted into triplet ones and vice versa. This results in a large enhancement of the triplet superconductivity, persisting well above the native triplet critical temperature.

  11. Fluctuation induced conductivity studies in YBa2Cu3Oy compound embedded by superconducting nano-particles Y-deficient YBa2Cu3Oy: effect of silver inclusion

    Science.gov (United States)

    Hannachi, E.; Slimani, Y.; Ben Salem, M. K.; Hamrita, A.; Al-Otaibi, A. L.; Almessiere, M. A.; Ben Salem, M.; Ben Azzouz, F.

    2016-09-01

    The effect of superconducting Y-deficient YBa2Cu3Oy nano-particles prepared by the planetary ball milling technique and silver inclusion on electrical fluctuation conductivity of polycrystalline YBa2Cu3Oy has been reported. Samples, synthesized by the conventional solid-state reaction technique, have been investigated using X-ray diffraction, scanning electron microscope and electrical resistivity. Scanning electron microscope analyses show that nano-particles of Y-deficient YBa2Cu3Oy are embedded in the superconducting matrix. The density of these nano-particles strongly depends on milling parameters. The fluctuation conductivity has been analyzed as a function of reduced temperature using the Aslamazov-Larkin model. Three different fluctuation regions namely critical, mean-field and short-wave are observed. The zero-temperature coherence length, the effective layer thickness of the two-dimensional system, critical magnetic fields and critical current density are estimated. Superconducting parameters are affected by Y-deficient YBa2Cu3Oy nano-particles. It has been found that attainment of an optimum concentration and well-dispersed of nano-sized inclusions by ball milling process improves the physical properties. On the other hand, the sample with Y-deficient YBa2Cu3Oy nano-particles and Ag exhibits better superconducting properties in comparison with free added one.

  12. Neutron scattering study of spin ordering and stripe pinning in superconducting La1.93Sr0.07CuO4

    Science.gov (United States)

    Jacobsen, H.; Zaliznyak, I. A.; Savici, A. T.; Winn, B. L.; Chang, S.; Hücker, M.; Gu, G. D.; Tranquada, J. M.

    2015-11-01

    The relationships among charge order, spin fluctuations, and superconductivity in underdoped cuprates remain controversial. We use neutron scattering techniques to study these phenomena in La1.93Sr0.07CuO4 , a superconductor with a transition temperature of Tc=20 K. At T ≪Tc we find incommensurate spin fluctuations with a quasielastic energy spectrum and no sign of a gap within the energy range from 0.2 to 15 meV. A weak elastic magnetic component grows below ˜10 K, consistent with results from local probes. Regarding the atomic lattice, we have discovered unexpectedly strong fluctuations of the CuO6 octahedra about Cu-O bonds, which are associated with inequivalent O sites within the CuO2 planes. Furthermore, we observed a weak elastic (3 3 ¯0 ) superlattice peak that implies a reduced lattice symmetry. The presence of inequivalent O sites rationalizes various pieces of evidence for charge stripe order in underdoped La2 -xSrxCuO4 . The coexistence of superconductivity with quasistatic spin-stripe order suggests the presence of intertwined orders; however, the rotation of the stripe orientation away from the Cu-O bonds might be connected with evidence for a finite gap at the nodal points of the superconducting gap function.

  13. Superconducting YBa2Cu3O7 films for novel (opto)electronic device structures

    Science.gov (United States)

    Pavuna, D.; Dwir, B.; Gauzzi, A.; James, J. H.; Kellett, B. J.

    1991-02-01

    This short overview briefly summarizes the most important parameters for successful preparation and associated properties of thin films of YBa2Cu3O(7-delta) (YBCO) superconductors. The principles are illustrated by using the example of monotarget ion beam sputtering technique: YBCO films grown in situ on SrTiO3 show Tc(onset) = 92 K and Tco = 91 K. Magnetron sputtering, E-beam evaporation, laser ablation and molecular beam epitaxy are discussed. In situ ion beam sputtering of YBCO on Si and GaAs substrates with intermediate, conducting Indium Tin Oxide (ITO) buffer layers is also presented. Uniform, textured YBCO films on ITO exhibit Tc(onset) at 92 K and Tco at 68 K and 60 K on Si and GaAs substrates, respectively; the latter is the highest Tc reported on GaAs. YBCO/ITO films exhibit metallic resistivity behavior. Finally, the performance of a simple optical bolometer demonstrated on YBCO films and the results of tunneling measurements on the window-type YBCO-Pb tunnel junctions are discussed.

  14. Comparison of the Isothermal Oxidation Behavior of As-Cast Cu-17%Cr and Cu-17%Cr-5%Al. Part 1; Oxidation Kinetics

    Science.gov (United States)

    Raj. Sai V.

    2008-01-01

    The isothermal oxidation kinetics of as-cast Cu-17%Cr and Cu-17%Cr-5%Al in air were studied between 773 and 1173 K under atmospheric pressure. These observations reveal that Cu- 17%Cr-5%Al oxidizes at significantly slower rates than Cu-17%Cr. The rate constants for the alloys were determined from generalized analyses of the data without an a priori assumption of the nature of the oxidation kinetics. Detailed analyses of the isothermal thermogravimetric weight change data revealed that Cu-17%Cr exhibited parabolic oxidation kinetics with an activation energy of 165.9 9.5 kJ mol-1. In contrast, the oxidation kinetics for the Cu-17%Cr- 5%Al alloy exhibited a parabolic oxidation kinetics during the initial stages followed by a quartic relationship in the later stages of oxidation. Alternatively, the oxidation behavior of Cu-17%CR- 5%Al could be better represented by a logarithmic relationship. The parabolic rate constants and activation energy data for the two alloys are compared with literature data to gain insights on the nature of the oxidation mechanisms dominant in these alloys.

  15. Comparison of the Isothermal Oxidation Behavior of As-Cast Cu-17 Percent Cr and Cu-17 Percent Cr-5 Percent Al. Part 1; Oxidation Kinetics

    Science.gov (United States)

    Raj, S. V.

    2008-01-01

    The isothermal oxidation kinetics of as-cast Cu-17%Cr and Cu-17%Cr-5%Al in air were studied between 773 and 1173 K under atmospheric pressure. These observations reveal that Cu-17%Cr-5%Al oxidizes at significantly slower rates than Cu-17%Cr. The rate constants for the alloys were determined from generalized analyses of the data without an a priori assumption of the nature of the oxidation kinetics. Detailed analyses of the isothermal thermogravimetric weight change data revealed that Cu-17%Cr exhibited parabolic oxidation kinetics with an activation energy of 165.9+/-9.5 kJ/mol. In contrast, the oxidation kinetics for the Cu-17%Cr-5%Al alloy exhibited a parabolic oxidation kinetics during the initial stages followed by a quartic relationship in the later stages of oxidation. Alternatively, the oxidation behavior of Cu-17%CR-5%Al could be better represented by a logarithmic relationship. The parabolic rate constants and activation energy data for the two alloys are compared with literature data to gain insights on the nature of the oxidation mechanisms dominant in these alloys.

  16. Superconductivity in the non-oxide perovskite MgCNi3.

    Science.gov (United States)

    He, T; Huang, Q; Ramirez, A P; Wang, Y; Regan, K A; Rogado, N; Hayward, M A; Haas, M K; Slusky, J S; Inumara, K; Zandbergen, H W; Ong, N P; Cava, R J

    2001-05-03

    The interplay of magnetic interactions, the dimensionality of the crystal structure and electronic correlations in producing superconductivity is one of the dominant themes in the study of the electronic properties of complex materials. Although magnetic interactions and two-dimensional structures were long thought to be detrimental to the formation of a superconducting state, they are actually common features of both the high transition-temperature (Tc) copper oxides and low-Tc material Sr2RuO4, where they appear to be essential contributors to the exotic electronic states of these materials. Here we report that the perovskite-structured compound MgCNi3 is superconducting with a critical temperature of 8 K. This material is the three-dimensional analogue of the LnNi2B2C family of superconductors, which have critical temperatures up to 16 K (ref. 2). The itinerant electrons in both families of materials arise from the partial filling of the nickel d-states, which generally leads to ferromagnetism as is the case in metallic Ni. The high relative proportion of Ni in MgCNi3 suggests that magnetic interactions are important, and the lower Tc of this three-dimensional compound-when compared to the LnNi2B2C family-contrasts with conventional ideas regarding the origins of superconductivity.

  17. Decoupling of superconducting planes of La1.905Ba0.095CuO4 in a transverse magnetic field

    Science.gov (United States)

    Tranquada, John; Stegen, Z.; Boebinger, G. S.; Han, Su Jung; Wu, Jie; Xu, Zhijun; Gu, Genda; Li, Qiang

    2012-02-01

    We have measured the resistivity parallel and perpendicular to the CuO2 planes in single crystals of La1.905Ba0.095CuO4 for magnetic fields up to 35 T applied along the c-axis. Below the zero-field superconducting transition temperature of 32 K, we observe that, above a threshold field, the c-axis resistivity grows with field, eventually reaching a maximum and then decreasing. At the resistivity maximum, interlayer pair tunneling becomes insignificant. Under the same field and temperature conditions, the in-plane resistivity remains quite low, reflecting robust superconductivity. We identify a regime in which the superconducting planes are effectively decoupled. At 20 K, a field much greater than 35 T would be required to destroy the in-plane pairing, despite the fact that the field also induces both charge and spin stripe order (J.S. Wen et al., arXiv:1009.0031).

  18. Measurement of unique magnetic and superconducting phases in oxygen-doped high-temperature superconductors La2-xSrxCuO4+y

    DEFF Research Database (Denmark)

    Udby, Linda; Larsen, Jacob; Christensen, Niels Bech

    2013-01-01

    We present a combined magnetic neutron scattering and muon spin rotation study of the nature of the magnetic and superconducting phases in electronically phase separated La2-xSrxCuO4+y, x=0.04, 0.065, 0.09. For all samples, we find long-range modulated magnetic order below TN≃Tc=39 K. In sharp co...

  19. Inductance mode characteristics of a ceramic YBa2Cu3O7-x radio-frequency superconducting quantum interference device at 77 K

    DEFF Research Database (Denmark)

    Il'ichev, E. V.; Andreev, A. V.; Jacobsen, Claus Schelde

    1993-01-01

    Experimental results on some radio-frequency superconducting quantum interference device (rf-SQUID) signal properties are presented. The quantum interferometer was made of ceramic YBa2Cu3O7−x and was due to a low critical current operated in the inductance or nonhysteretic mode. With bias current...

  20. Superconducting Dy1-x(Gd,Yb)xBa2Cu3O7-δ thin films made by Chemical Solution Deposition

    DEFF Research Database (Denmark)

    Opata, Yuri Aparecido; Wulff, Anders Christian; Hansen, Jørn Otto Bindslev

    2016-01-01

    Dy1-x(Gd or Yb)xBa2Cu3O7-δ samples were prepared using chemical solution deposition (CSD), based on trifluoroacetate metal-organic decomposition (MOD) methods. X-ray diffraction results demonstrated the formation of the RE123 superconducting phase with a strong in-plane and out-of-plane texture. c...

  1. Microwave properties of YBa2Cu3O(7-delta) high-transition-temperature superconducting thin films measured by the power transmission method

    Science.gov (United States)

    Miranda, F. A.; Gordon, W. L.; Bhasin, K. B.; Heinen, V. O.; Warner, J. D.

    1991-01-01

    The microwave response of YBa2Cu3O(7-delta) superconducting thin films deposited on LaAlO3, MgO, YSZ, and LaGaO3 substrates are studied. It is found that the microwave transmission properties are very weakly dependent on temperature in the normal state but change drastically upon transition to the superconducting state. In particular, the transmission decreases and there is a negative phase shift with respect to the phase at room temperature when the sample is cooled through its transition temperature. The magnetic penetration depth for all the films was determined from the surface reactance of the films. The microwave complex conductivity is determined in both the normal and the superconducting state. It is observed that both sigma1 and sigma2 increase in transition to the superconducting state. The surface resistivity is calculated for all the films.

  2. Vertical temperature boundary of the pseudogap under the superconducting dome in the phase diagram of Bi2Sr2CaCu2O8 +δ

    Science.gov (United States)

    Loret, B.; Sakai, S.; Benhabib, S.; Gallais, Y.; Cazayous, M.; Méasson, M. A.; Zhong, R. D.; Schneeloch, J.; Gu, G. D.; Forget, A.; Colson, D.; Paul, I.; Civelli, M.; Sacuto, A.

    2017-09-01

    Combining electronic Raman scattering experiments with cellular dynamical mean field theory, we present evidence of the pseudogap in the superconducting state of various hole-doped cuprates. In Bi2Sr2CaCu2O8 +δ we track the superconducting pseudogap hallmark, a peak-dip feature, as a function of temperature T and doping p , well beyond the optimal one. We show that, at all temperatures under the superconducting dome, the pseudogap disappears at the doping pc, between 0.222 and 0.226, where also the normal-state pseudogap collapses at a Lifshitz transition. This demonstrates that the superconducting pseudogap boundary forms a vertical line in the T -p phase diagram.

  3. Oxygen nonstoichiometry and superconductivity of the Nd 2- xCe xCuO 4- δ single crystal

    Science.gov (United States)

    Pankov, V.; Kalanda, N.; Truchan, V.; Zhigunov, D.; Babushkin, O.

    2002-09-01

    Investigations of the oxygen desorption by Nd 2- xCe xCuO 4- δ single crystals (0⩽ x⩽0.17) was carried out, and we present here a group of superconductors with an electron type of conductivity made by crystallization from a melt. It was established that, under heating of the single crystals with a constant flow rate of Ar and pO 2=100 Pa, the oxygen desorption proceeded through two maxima in the temperature range of 973-1173 K, the nature of which is related to desorption of oxygen from different crystallographic fragments. It is suggested that the problem of creation of the necessary concentration of oxygen and its ordering in the net of Cu-O 2 layers is related to the redistribution of oxygen from the 02 to the 01 structural positions in the Nd 2- xCe xCuO 4- δ crystal. Under a schedule of three stages of thermal treatments of the single crystal, we were able to achieve superconductivity of the researched samples at temperatures of <19 K.

  4. Evidence for K-substitution in the Tl-sites of superconducting Tl 2CaBa 2Cu 2O χ: Neutron diffraction studies

    Science.gov (United States)

    Sequeira, A.; Rajagopal, H.; Gopalakrishnan, I. K.; Sastry, P. V. P. S. S.; Phatak, G. M.; Yakhmi, J. V.; Iyer, R. M.

    1988-11-01

    A comparison of the Rietveld profile refinement of neutron diffraction data of the superconducting compounds Tl-2122 (i.e. Tl 2CaBa 2Cu 2O χ) and Tl 1K 1Ca 1Ba 2Cu 2O y provides evidence that nearly half of the Tl-sites belonging to the pure Tl-2122 structure get substituted by K-ions in Tl 1K 1Ca 1Ba 2Cu 2O y. The consequence of this is reflected in a substantial movement of Ba-ions towards the plane of the O(2)-ions in the K-substituted compound.

  5. Charge localization in oxidized Pb2Sr2Y0.5Cu308+8 studies by electron and neutron powder diffraction

    DEFF Research Database (Denmark)

    Iversen, M.H.; Jørgensen, J.E.; Andersen, N.H.

    1998-01-01

    Oxidized Pb2Sr2Y0.5Ca0.5Cu3O8+delta was studied by electron diffraction and neutron powder diffraction. The electron diffraction diagrams showed a doubling along the b-axis and a quadruplication along the a-axis indicating that the excess oxygen is incorporated into the structure in an ordered wa...... of superconductivity in the oxidized compound. (C) 1998 Elsevier Science B.V.......Oxidized Pb2Sr2Y0.5Ca0.5Cu3O8+delta was studied by electron diffraction and neutron powder diffraction. The electron diffraction diagrams showed a doubling along the b-axis and a quadruplication along the a-axis indicating that the excess oxygen is incorporated into the structure in an ordered way....... The oxygen content was determined from refinement of the neutron data and delta = 1.2(1) was obtained. Calculation of bond valency sums for the cations shows that the bond valency sum for Cu in the CuO2 layers in Pb2Sr2Y0.5Ca0.5Cu3O8 decreases when the compound is oxidized, thereby explaining the lack...

  6. Relationship between oxygen content and seebeck coefficient of Bi-based superconducting oxides

    Science.gov (United States)

    Miura, N.; Sakata, F.; Shimizu, Y.; Deshimaru, Y.; Yamazoe, N.

    1994-12-01

    The correlations among Seebeck coefficient, oxygen content and superconducting property were examined for four Bi-based oxides (2223 and 2212 phases). Each oxide underwent reversible sorption and desorption of small amounts of oxygen (ca.3x10 -5mol/g) in the temperature range 100-600 °C. In good agreement with such behavior, the Seebeck coefficient (Q) of each oxide was found to change reversibly with changing temperature, suggesting that Q is a reversible function of oxygen content. It was further found that the highest Tc was reached at the oxygen content at which Q was incidentally brought to be around zero at 100 °C for each oxide.

  7. Materials science studies of high-temperature superconducting ceramic oxides. Final report, May 1988-March 1993

    Energy Technology Data Exchange (ETDEWEB)

    Vezzoli, G.C.; Chen, M.F.; Craver, F.; Katz, R.N.

    1997-12-01

    Herein is presented the results of a comprehensive program of research aimed at understanding the materials science and the mechanistic physics of high-temperature superconducting oxides. This comprehensive research program has identified the materials properties that are consistently associated with high-Tc superconductors and has shown that the mechanism that gives rise to the phenomenon of high-Tc superconductivity is associated with bound holes that are due to charge-transfer excitations at high frequency. The latter are a result of the high internal electric field present in high-Tc materials, owing to the asymmetry of the crystal structure. The interaction of bound holes with free electrons and the interaction of local spin fluctuations with the spin of free electrons generate a charge density wave and a spin density wave that cause Cooper pairing.

  8. A Controllable Synthetic Route for Preparing Graphene-Cu and Graphene-Cu2O Nanocomposites Using Graphene Oxide-CuO as a Precursor

    Institute of Scientific and Technical Information of China (English)

    CHEN Li; ZHU Junwu; BI Huiping; MENG Xiaoqian; YAO Pengcheng; HAN Qiaofeng

    2015-01-01

    The development of convenient method to obtain graphene-based nanocomposites is a key issue for their application. Herein, we described a facile route for synthesizing graphene-Cu and graphene-Cu2O nanocomposites using graphene oxide-CuO as a precursor. Remarkably, the different nanocomposites could be formed just by varying the reaction temperature and time. This work provides a feasible route for the preparation of graphene-based nanocomposites with various constituents.

  9. Oxygen Adsorption-Desorption Behavior and Superconducting Properties of High-Tc Bi(Pb)-Sr-Ca-Cu-O

    Science.gov (United States)

    Miura, Norio; Suzuta, Hiroki; Deshimaru, Yuichi; Shimizu, Youichi; Sakashita, Hirofumi; Yamazoe, Noboru

    1989-07-01

    Temperature-programmed desorption (TPD) chromatograms revealed that a small amount of oxygen was desorbed from high-Tc Bi(Pb)-Sr-Ca-Cu-O (BPSCCO) in the temperature range from ca. 350 to ca. 650°C prior to a steep increase of oxygen desorption in the higher temperature range. The Tc of BPSCCO was significantly lowered with the progress of oxygen desorption especially in the former temperature range, and was restored to the original level when the desorbed oxygen was recovered. With no corresponding changes in X-ray powder diffraction pattern being detected, the oxygen desorbed below ca. 650°C was concluded to have strong relevance to the superconductivity of BPSCCO.

  10. Surface resistance measurement of superconducting YBa sub 2 Cu sub 3 O sub 7 in a magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Chin, C.C. (Center for Materials Science and Engineering, Massachusetts Institute of Technology, Department of Physics, Massachusetts Institute of Technology, Cambridge, MA (USA)); Rainville, P.J.; Drehman, A.J.; Derov, J.S.; Steinbeck, J. (Rome Air Development Center (RADC), Hanscom AFB, MA (USA)); Dresselhaus, G. (Francis Bitter National Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, MA (USA)); Dresselhaus, M.S. (Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA (USA))

    1990-08-01

    We report on the magnetic-field dependent surface resistance of polycrystalline YBa{sub 2}Cu{sub 3}O{sub 7} ({ital T}{sub {ital c}}{congruent}92 K), measured using a brass cylindrical cavity resonator, operating at 16.5 GHz in the TE{sub 011} mode. A dc magnetic field {ital H}{sub app} is applied parallel to the superconducting sample surface, and the temperature dependence of the surface resistance is measured for four different values of {ital H}{sub app} (0 T, 0.22 T, 1 T, 5 T). An effective medium theory and the two-fluid model are used to fit the surface resistance versus temperature measurements both in zero field and for various applied fields. These results are applied to characterize the microwave properties of a polycrystalline ceramic superdconductor.

  11. Effect of nanowires SiO2 on superconducting properties of YBa2Cu3O7-d bulks

    Science.gov (United States)

    Salem, M. K. Ben; Hannachi, E.; Slimani, Y.; Hamrita, A.; Bessais, L.; Azzouz, F. Ben; Salem, M. Ben

    2013-12-01

    The effects of SiO2 nanowires on the superconducting properties of YBa2Cu3O7-d (YBCO) compound were studied. Samples were synthesized in air using a standard solid state reaction technique by adding nanowires SiO2 up to 1wt.%. Phase analysis by X-ray diffraction (XRD), microstructure investigation by scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDXS), critical current density dependence on applied magnetic field Jc(H) and electrical resistivity as a function of temperature ρ(T) were carried out to evaluate the relative performance of samples. We find that Tco does not change much (90.8-90.2 K) with the low concentration of SiO2 (≤ 0.1 wt.%) and Jc(H) is enhanced.

  12. Effects of doping on superconducting gap anisotropy in Bi_2Sr2 CaCu_2O8+x

    Science.gov (United States)

    Onellion, Marshall; Ma, Jian; Quitmann, Christoph; Kelley, R. J.; Kendziora, C.; Larosa, S.; Berger, H.; Margaritondo, G.

    1996-03-01

    We report on recent fabrication of Bi_2Sr_2CaCu_2O_8+x single crystals that span the phase diagram from insulators, all of the underdoped part, and as far into the overdoped part as a superconducting transition temperature, T_c=55K.[1,2] Optimally doped and overdoped samples exhibit narrow susceptibility transition widths. However, the c-axis between insulators-underdoped-optimally doped materials is almost identical, indicating that oxygen is added and removed from different part of the unit cell.[1,2] We have studied the superconducting gap anisotropy for optimally doped and overdoped samples. We find that the ratio gap along the (0,π)direction to that along the (π,π) is 20:1 for optimally doped or slightly underdoped samples, consistent with earlier report. The gap along the (π,π) direction is indistiguishable from zero. However, for somewhat overdoped samples, the gap anisotropy is 2:1, with the smaller gap 10meV, definitely non-zero.

  13. Catalytic Oxidative Properties and Characterization of CuO/CeO2 Catalysts

    Institute of Scientific and Technical Information of China (English)

    蒋晓原; 周仁贤; 袁骏; 吕光烈; 郑小明

    2003-01-01

    The oxidative properties and characterization of CuO, CeO2 and CuO/CeO2 catalysts were examined by means of a CO micro-reactor GC system, TPR, XPS and X-ray diffraction Rietveld methods. The results show that either CuO or CeO2 activity is quite low for CO oxidation. However, when CuO and CeO2 are mixed, the oxidative activity of the catalyst increases significantly, probably owing to the valency status of copper species (Cu2+ and Cu+) on the CeO2 surface, the dispersion and reducibility. XPS surface analysis shows that CuO loading is very important in forming of either Cu2+ or Cu+. Rietveld analysis shows that some CuO, which has smaller ion radius than Ce4+, enters the CeO2 lattice after CuO and CeO2 are mixed. When the CuO loading reaches 5.0%, the size of CuO crystals is a minimum (6.1 nm) and the micro-strain value is a maximum (2.86×10-3), resulting in high surface energy and the best activity for CO oxidation.

  14. Valence State of Active Copper in CuOx/CeO2 Catalysts for CO Oxidation

    Institute of Scientific and Technical Information of China (English)

    Zeng Shanghong; Bai Xue; Wang Xiaoyan; Yu Wenguo; Liu Yuan

    2006-01-01

    CuOx/CeO2 catalysts were prepared by adsorption-impregnation method.CO conversion was tested over the catalysts pretreated under different conditions for preferential CO oxidation in H2, and the catalysts were characterized with X-ray photoelectron spectroscopy and temperature programmed reduction.Experimental results show that there are two kinds of copper, which are Cu+ and Cu2+ in calcined CuOx/CeO2.Among them, the Cu+ is the key active component for CO oxidation.The main reason is as follows: CO is activated by copper for CO oxidation over CuOx/CeO2, while CO can not be activated by Cu2+.Only when Cu2+ is reduced to Cu+ or Cu0, the copper may be active for CO oxidation, moreover, the experimental results show that the reduction of Cu2+ does not lead to an increase of catalytic activity.So the active species is Cu+ in CuOx/CeO2 catalysts.

  15. Harvesting (67)Cu from the Collection of a Secondary Beam Cocktail at the National Superconducting Cyclotron Laboratory.

    Science.gov (United States)

    Mastren, Tara; Pen, Aranh; Loveless, Shaun; Marquez, Bernadette V; Bollinger, Elizabeth; Marois, Boone; Hubley, Nicholas; Brown, Kyle; Morrissey, David J; Peaslee, Graham F; Lapi, Suzanne E

    2015-10-20

    Isotope harvesting is a promising new method to obtain isotopes for which there is no reliable continuous supply at present. To determine the possibility of obtaining radiochemically pure radioisotopes from an aqueous beam dump at a heavy-ion fragmentation facility, preliminary experiments were performed to chemically extract a copper isotope from a large mixture of projectile fragmentation products in an aqueous medium. In this work a 93 MeV/u secondary beam cocktail was collected in an aqueous beam stop at the National Superconducting Cyclotron Laboratory (NSCL) located on the Michigan State University (MSU) campus. The beam cocktail consisted of ∼2.9% (67)Cu in a large mixture of co-produced isotopes ranging in atomic number from ∼19 to 34. The chemical extraction of (67)Cu was achieved via a two-step process: primary extraction using a divalent metal chelation disk followed by anion-exchange chromatography. A significant fraction (74 ± 4%) of the (67)Cu collected in the aqueous beam stop was recovered with >99% radiochemical purity. To illustrate the utility of this product, the purified (67)Cu material was then used to radiolabel an anti-EGFR antibody, Panitumumab, and injected into mice bearing colon cancer xenografts. The tumor uptake at 5 days postinjection was found to be 12.5 ± 0.7% which was in very good agreement with previously reported studies with this radiolabeled antibody. The present results demonstrate that harvesting isotopes from a heavy-ion fragmentation facility could be a promising new method for obtaining high-quality isotopes that are not currently available by traditional methods.

  16. Antiferromagnetic spin correlation and superconductivity in La2-xSrxCuO4: Cu NQR study

    Science.gov (United States)

    Kitaoka, Y.; Ohsugi, S.; Ishida, K.; Asayama, K.

    1990-09-01

    We have measured the nuclear spin-lattice relaxation time T1 of 63Cu in La2- xSrxCuO4 in the concentration range of x = 0.075-0.15 approaching the magnetic phase boundary around x = 0.05. ( T1T) -1 is found to be markedly enhanced with decreasing Sr content and temperature due to the development of the AF spin correlation among Cu spins. It is shown that ( T1T) -1 follows a T-dependence of the form C/( T+θ) associated with the Curie-Weiss law of the staggered susceptibility χQ( T) at the zone boundary ( Q = ( π/ α, π/ α)). An important finding is that the Weiss temperature θ is decreased from 75 K (x = 0.15) to 20 K (x = 0.07 5) with decreasing Sr content, which causes the large enhancement of ( T1T) -1 and accompanies the decreases of Tc, becoming 0 K at θ = 0 K for x = 0.05, whereas the Curie constant, C, slightly increases.

  17. CuO impregnated activated carbon for catalytic wet peroxide oxidation of phenol.

    Science.gov (United States)

    Liou, Rey-May; Chen, Shih-Hsiung

    2009-12-15

    This paper presents an original approach to the removal of phenol in synthetic wastewater by catalytic wet peroxide oxidation with copper binding activated carbon (CuAC) catalysts. The characteristics and oxidation performance of CuAC in the wet hydrogen peroxide catalytic oxidation of phenol were studied in a batch reactor at 80 degrees C. Complete conversion of the oxidant, hydrogen peroxide, was observed with CuAC catalyst in 20 min oxidation, and a highly efficient phenol removal and chemical oxygen demand (COD) abatement were achieved in the first 30 min. The good oxidation performance of CuAC catalyst was contributed to the activity enhancement of copper oxide, which was binding in the carbon matrix. It can be concluded that the efficiency of oxidation dominated by the residual H2O2 in this study. An over 90% COD removal was achieved by using the multiple-step addition in this catalytic oxidation.

  18. Evolution of superconducting correlations within magnetic-field-decoupled La2-xBaxCuO4 (x=0.095)

    Science.gov (United States)

    Stegen, Z.; Han, Su Jung; Wu, Jie; Pramanik, A. K.; Hücker, M.; Gu, Genda; Li, Qiang; Park, J. H.; Boebinger, G. S.; Tranquada, J. M.

    2013-02-01

    We explore the evolution of superconductivity in La2-xBaxCuO4 with x=0.095 in magnetic fields of up to 35 T applied perpendicular to the CuO2 planes. Previous work on this material has shown that perpendicular fields enhance both charge- and spin-stripe order within the planes. We present measurements of the resistivity parallel and perpendicular to the planes, as well as the Hall effect. Measurements of magnetic susceptibility for fields of up to 15 T applied both parallel and perpendicular to the planes provide complementary measures of the superconductivity. We show that fields sufficient to destroy pair tunneling between the planes do not disrupt the superconducting correlations within the planes. In fact, we observe an onset of large-amplitude but phase-disordered superconductivity within the planes at approximately 30 K that is remarkably insensitive to field. With further cooling, we observe a phase-transition-like drop in the in-plane resistivity to an apparent state of superconductivity despite the lack of phase coherence between the layers. These observations raise interesting questions concerning the identification of the upper critical field, where pairing is destroyed, in underdoped cuprates.

  19. Early and transient stages of Cu oxidation: Atomistic insights from theoretical simulations and in situ experiments

    Science.gov (United States)

    Zhu, Qing; Zou, Lianfeng; Zhou, Guangwen; Saidi, Wissam A.; Yang, Judith C.

    2016-10-01

    Understanding of metal oxidation is critical to corrosion control, catalysis synthesis, and advanced materials engineering. Although, metal oxidation process is rather complicated, different processes, many of them coupled, are involved from the onset of reaction. Since first introduced, there has been great success in applying heteroepitaxial theory to the oxide growth on a metal surface as demonstrated in the Cu oxidation experiments. In this paper, we review the recent progress in experimental findings on Cu oxidation as well as the advances in the theoretical simulations of the Cu oxidation process. We focus on the effects of defects such as step edges, present on realistic metal surfaces, on the oxide growth dynamics. We show that the surface steps can change the mass transport of both Cu and O atoms during oxide growth, and ultimately lead to the formation of different oxide morphology. We also review the oxidation of Cu alloys and explore the effect of a secondary element to the oxide growth on a Cu surface. From the review of the work on Cu oxidation, we demonstrate the correlation of theoretical simulations at multiple scales with various experimental techniques.

  20. Novel Interplay between High-Tc Superconductivity and Antiferromagnetism in Tl-Based Six-CuO2-Layered Cuprates: 205Tl- and 63Cu-NMR Probes

    Science.gov (United States)

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

    2016-08-01

    We report 63Cu- and 205Tl-NMR studies on six-layered (n = 6) high-Tc superconducting (SC) cuprate TlBa2Ca5Cu6O14+δ (Tl1256) with Tc ˜ 100 K, which reveal that antiferromagnetic (AFM) order takes place below TN ˜ 170 K. In this compound, four underdoped inner CuO2 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 TN ˜ 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 TN and the AFM moments for the IPs does not bring about any reduction in Tc, since Tc ˜ 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 TN 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.

  1. Characteristics of oxide scale formed on Cu-bearing austenitic stainless steel during early stages of high temperature oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Swaminathan, Srinivasan, E-mail: swaminathan@kist.re.kr [Metallurgy & Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India); High Temperature Energy Materials Research Center, Korea Institute of Science and Technology, Seongbuk-gu, Seoul 136 791 (Korea, Republic of); Krishna, Nanda Gopala [Metallurgy & Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India); Kim, Dong-Ik, E-mail: dongikkim@kist.re.kr [High Temperature Energy Materials Research Center, Korea Institute of Science and Technology, Seongbuk-gu, Seoul 136 791 (Korea, Republic of)

    2015-10-30

    Highlights: • Initial oxidation characteristics of Cu-bearing austenitic stainless steel at 650 °C were studied. • Strong segregation and oxidation of Mn and Nb were found in the entire oxide scale. • Surface coverage by metallic Cu-rich precipitates increases with exposure time. • Chemical heterogeneity of oxide scale revealed initial oxidation to be non-selective. • Fe-Cr and Mn-Cr mixed oxides were realized along with binary oxides of Fe, Cr and Mn. - Abstract: Oxide scale evolution on Cu-bearing austenitic stainless steel 304H at 650 °C, in ambient air, for exposure times 100, 300, 500 and 1000 h, has been investigated. Surface morphology and chemistry of the oxide scale grown were examined using SEM/EDX and XPS. The oxidation kinetics was determined by measuring the weight change using an electronic balance. At the initial stage, up to 500 h of exposure time, the oxidation rate was rapid due to surface reactions governed primarily by oxygen ingress, and then, dropped to a low rate after prolonged oxidation for 1000 h. The diffusion of reactants through the initially formed oxide scale limits the oxidation rate at longer times, thus, the progress of reaction followed the parabolic kinetics. The formed oxide scale was enriched significantly with segregation and subsequent oxidation of Nb, and finely dispersed metallic Cu particles. Within the time frame of oxidation, the oxide scale was mainly composed of mixed oxides such as FeCr{sub 2}O{sub 4} and MnCr{sub 2}O{sub 4} along with the binary oxides of Fe, Cr and Mn. Moreover, the precipitation fraction of Cu-rich particles on the oxide scale increased markedly with increase of exposure times. The chemical heterogeneity of oxide scale suggests that the oxidation occurred in a non-selective manner.

  2. Superconducting glass-ceramics in the Bi-Sr-Ca-Cu-O system

    Science.gov (United States)

    De Guire, Mark R.; Kim, Cheol J.; Bausal, Narottam P.

    1990-01-01

    Differential thermal analysis, XRD, SEM, and resistivity measurements, have been used to study the recrystallization during various heat treatments of a Bi1.5SrCaCu2O(z) glass obtained by rapid quenching from the melt. Heating at 450 C formed the Bi(2+x)Sr(2-x)-CuO(z) solid solution designated 'R'. Between 765 and 845 C, R reacts slowly with the glass to form the 80 K superconductor Bi2(Sr,Ca)3Cu2O(z), together with CuO. Heating for 7 days at the higher temperature, followed by slow cooling, raised the temperature of zero resistance to 77 K.

  3. Relationship between effective mass and superconducting critical temperature in the organic superconductor {kappa}-(BEDT-TTF){sub 2}Cu(NCS){sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Caulfield, J. [Physics Dept., Univ. of Oxford, Clarendon Lab. (United Kingdom); Lubczynski, W. [Physics Dept., Univ. of Oxford, Clarendon Lab. (United Kingdom); Lee, W. [School of Physics and Materials, Lancaster Univ. (United Kingdom); Singleton, J. [Physics Dept., Univ. of Oxford, Clarendon Lab. (United Kingdom); Pratt, F.L. [Physics Dept., Univ. of Oxford, Clarendon Lab. (United Kingdom); Hayes, W. [Physics Dept., Univ. of Oxford, Clarendon Lab. (United Kingdom); Kurmoo, M. [Royal Institution, London (United Kingdom); Day, P. [Royal Institution, London (United Kingdom)

    1995-03-15

    We report high pressure magnetotransport on the organic superconductor {kappa}-(BEDT-TTF){sub 2}Cu(NCS){sub 2}. The observation of Shubnikov-de Haas and magnetic breakdown oscillations has allowed the pressure dependences of the Fermi surface topology and quasiparticle effective masses to be deduced and compared with simultaneous measurements of the superconducting critical temperature T{sub c}. The data strongly suggest that the enhancement of the effective mass and the superconducting behaviour are directly connected. The results are fitted by calculations of the linearised Eliashberg equations. (orig.)

  4. Oxygen isotope effect on the superconductivity and stripe phase in La$_{1.6-x}$Nd$_{0.4}$Sr$_{x}$CuO$_4$

    OpenAIRE

    Wang, G. Y.; Zhang, J D; Yang, R. L.; Chen, X. H.

    2007-01-01

    The oxygen isotope effect on the superconductivity, stripe phase and structure transition is systematically investigated in La$_{1.6-x}$Nd$_{0.4}$Sr$_{x}$CuO$_4$ with static stripe phase. Substitution of $^{16}$O by $^{18}$O leads to a decrease in superconducting transition temperature T$_C$, while enhances the temperature of the structural transition from low-temperature-orthorhombic (LTO) phase to low-temperature-tetragonal (LTT) phase. Compared to the Nd free sample, a larger isotope effec...

  5. Superconductivity of up to 80 K for Tb-123 - TbSr2Cu2.7Mo0.3O7

    OpenAIRE

    Awana, V. P. S.; Kishan, H.; Takayama-Muromachi, E; WATANABE, T.; Karppinen, M.; Yamauchi, H.; Malik, S K; Yelon, W. B.; Ganesan, V; Narlikar, A. V.

    2003-01-01

    The Tb-123 phase has been synthesized in single-phase form with the composition TbSr2Cu2.7Mo0.3O7 by solid-state reaction route and its phase purity is confirmed by neutron powder diffraction experiments. As-synthesized sample does not show superconductivity down to 5 K. An unusually high antiferromagnetic ordering temperature (TN) of around 7 K is seen for Tb. After 120-atm-O2 post-annealing, bulk superconductivity is achieved in the compound at around 30 K, without any significant effect on...

  6. Scanning Josephson tunneling microscopy of single-crystal Bi_{2}Sr_{2}CaCu_{2}O_{8+delta} with a conventional superconducting tip.

    Science.gov (United States)

    Kimura, Hikari; Barber, R P; Ono, S; Ando, Yoichi; Dynes, R C

    2008-07-18

    We have performed both Josephson and quasiparticle tunneling in vacuum tunnel junctions formed between a conventional superconducting scanning tunneling microscope tip and overdoped Bi_{2}Sr_{2}CaCu_{2}O_{8+delta} single crystals. A Josephson current is observed with a peak centered at a small finite voltage due to the thermal-fluctuation-dominated superconducting phase dynamics. Josephson measurements at different surface locations yield local values for the Josephson I_{C}R_{N} product. Corresponding energy gap measurements were also performed and a surprising inverse correlation was observed between the local I_{C}R_{N} product and the local energy gap.

  7. Bond polarons and high-Tc superconductivity in single layer La_(2-x)Sr_xCuO_4: normal state currents and pairing

    CERN Document Server

    Georgiev, Mladen

    2011-01-01

    We use the term "bond polaron" for a phonon coupled entity which makes the link between neighboring conductive CuO_2 layers in high-Tc superconductive materials. The link is essential for the superconductivity which requires a long range phase coherence in addition to pairing of carriers. The linkage features studied point to a process which is less dependent on the doped hole density implanted as x in the solid solution. The analysis applies to single layered materials mostly but may help understand multilayer ones as well.

  8. Thick REBaCuO superconducting films through single-coating of low-fluorine metallorganic solution

    Science.gov (United States)

    Boubeche, M.; Cai, C. B.; Jian, H. B.; Li, M. J.; Yang, W. T.; Liu, Z. Y.; Bai, C. Y.

    2016-10-01

    A high critical current Ic is crucial for the application of high temperature superconductors YBa2Cu3O7-δ in energy efficient power devices and wires. In this paper we report the fabrication of thick (YGd)1.3Ba2Cu3O7-x films on a metal substrate using low-fluorine metal organic deposition method. The effects of the film thickness on the microstructure, texture and superconductivity properties of the films were evaluated. In order to increase the film thicknesses by single coating, the influence of withdrawal speed during the dip coating on resulting thickness are investigated with the other processing parameters fixed. It is revealed that there is a maximum thickness for a certain starting solution. Here we used 3 different solutions, Conventional Low Fluorine solutions with 2 M and 2.5 M, and super low-fluorine solution with 2.5 M. The maximum thicknesses of about 710 nm, 1280 nm and 1460 nm were obtained, respectively.

  9. Preparation of very thin superconducting films of Y-Ba-Cu-O by a layer-by-layer resistive evaporation

    Energy Technology Data Exchange (ETDEWEB)

    Azoulay, J.; Goldschmidt, D. (Raymond and Beverly Sackler Faculty of Exact Sciences, School of Physics and Astronomy, Tel Aviv University, Tel Aviv 69978, Israel, and Center for Technological Education, Holon, P.O. Box 305, Holon 58680, Israel (IL)); Brener, R. (Solid State Institute, Technion, Israel Institute of Technology, Haifa 3200, Israel)

    1989-10-15

    We report here on 1/4 -{mu}m-thick superconducting Y-Ba-Cu-O films, produced by a sequential layer-by-layer deposition of Cu, BaF{sub 2}, and YF{sub 3}, utilizing solely resistive evaporation from tungsten boats onto SrTiO{sub 3} substrates. The films are composed primarily of quasioriented elongated grains and have, on the average, the correct stoichiometry. A transition onset at 75 K and width of {similar to}25 K have been observed in these films. The shape of the current-voltage curve indicates that Josephson-coupled weak links limit the transport in these films. However, the magnitude of critical current (3000 A/cm{sup 2} at {similar to}10 K) is larger than that found in bulk ceramic superconductors. The origin of weak links in these films is probably in the regions of contact between the elongated grains. The relatively large critical current density, as compared to regular bulk ceramic superconductors, is presumably related to the quasioriented nature of the film.

  10. Kinetic equation for internal oxidation of Cu-Al alloy cylinders

    Institute of Scientific and Technical Information of China (English)

    Kexing Song; Jiandong Xing; Baohong Tian; Ping Liu; Qiming Dong

    2005-01-01

    The kinetics of internal oxidation of Cu-Al alloy cylinders, containing up to 2.214mol% Al, were investigated in the temperature range of 1023 K to 1273 K, and the depth of internal oxidation was measured in the microscopy. A kinetic equation was derived to describe the internal oxidation of Cu-Al alloy cylinders. For the internal oxidation of Cu-Al alloys employed in the synthesis of alumina dispersion strengthened copper, the kinetic equation can be simplified. The derived equation was checked experimentally by means of oxidation depth measurements and the results show that the derived equation is exact enough to describe the kinetics of internal oxidation of Cu-Al alloy cylinders. Based on this equation and the oxidation depth measurements, the permeability of oxygen in solid copper was obtained. Investigation also shows that there is no evidence for preferential diffusion along grain boundaries in the process of internal oxidation.

  11. Structure and Catalytic Behavior of CuO-ZrO-CeO2 Mixed Oxides

    Institute of Scientific and Technical Information of China (English)

    王恩过; 陈诵英

    2002-01-01

    The effect of doping CuO on the structure and properties of zirconia-ceria mixed oxide was studied. The results show that addition of CuO decreases the reduction temperature of ceria, and stabilizes the cubic structure of mixed oxides, and enhances catalytic activity of CuO-ZrO-CeO2 mixed oxides for CO oxidation. Increasing ceria content in the mixed oxides can enhance the catalytic activity, but some impurities such as sulfate make catalytic activity falling. There is little effect of calcination temperature on catalytic activities, implying that these catalysts are effective with good thermal stability.

  12. Probing the connections between superconductivity, stripe order, and structure in La1.905Ba0.095Cu1-yZnyO4

    Science.gov (United States)

    Wen, Jinsheng; Xu, Zhijun; Xu, Guangyong; Jie, Qing; Hücker, M.; Zheludev, A.; Tian, Wei; Winn, B. L.; Zarestky, J. L.; Singh, D. K.; Hong, Tao; Li, Qiang; Gu, Genda; Tranquada, J. M.

    2012-04-01

    The superconducting system La2-xBaxCuO4 is known to show a minimum in the transition temperature Tc at x=(1)/(8) where maximal stripe order is pinned by the anisotropy within the CuO2 planes that occurs in the low-temperature-tetragonal (LTT) crystal structure. For x=0.095, where Tc reaches its maximum value of 32 K, there is a roughly coincident structural transition to a phase that is very close to LTT. Here, we present a neutron scattering study of the structural transition, and demonstrate how features of it correlate with anomalies in the magnetic susceptibility, electrical resistivity, thermal conductivity, and thermoelectric power. We also present measurements on a crystal with 1% Zn substituted for Cu, which reduces Tc to 17 K, enhances the spin stripe order, but has much less effect on the structural transition. We make the case that the structural transition correlates with a reduction of the Josephson coupling between the CuO2 layers, which interrupts the growth of the superconducting order. We also discuss evidence for two-dimensional superconducting fluctuations in the normal state, analyze the effective magnetic moment per Zn impurity, and consider the significance of the anomalous thermopower often reported in the stripe-ordered phase.

  13. Probing the connections between superconductivity, stripe order, and structure in La1.905Ba0.095Cu1 yZnyO4

    Energy Technology Data Exchange (ETDEWEB)

    Wen, Jinsheng [University of California, Berkeley; Xu, Zhijun [Brookhaven National Laboratory (BNL); Xu, Guangyong [Brookhaven National Laboratory (BNL); Jie, Qing [Brookhaven National Laboratory (BNL); Hucker, M. [Brookhaven National Laboratory (BNL); Zheludev, A [ETH Zurich, Switzerland; Tian, Wei [Ames Laboratory and Iowa State University; Winn, Barry L [ORNL; Zarestky, Jerel L [ORNL; Singh, D. K. [University of Maryland and NIST; Hong, Tao [ORNL; Li, Qiang [Brookhaven National Laboratory (BNL); Gu, Genda [Brookhaven National Laboratory (BNL); Tranquada, John M. [Brookhaven National Laboratory (BNL)

    2012-01-01

    The superconducting system La2 xBaxCuO4 is known to show a minimum in the transition temperature, Tc, at x = 1/8 where maximal stripe order is pinned by the anisotropy within the CuO2 planes that occurs in the low-temperature-tetragonal (LTT) crystal structure. For x = 0.095, where Tc reaches its maximum value of 32 K, there is a roughly coincident structural transition to a phase that is very close to LTT. Here we present a neutron scattering study of the structural transition, and demonstrate how features of it correlate with anomalies in the magnetic susceptibility, electrical resistivity, thermal conductivity, and thermoelectric power. We also present measurements on a crystal with 1% Zn substituted for Cu, which reduces Tc to 17 K, enhances the spin stripe order, but has much less effect on the structural transition. We make the case that the structural transition correlates with a reduction of the Josephson coupling between the CuO2 layers, which interrupts the growth of the superconducting order. We also discuss evidence for two-dimensional superconducting fluctuations in the normal state, analyze the effective magnetic moment per Zn impurity, and consider the significance of the anomalous thermopower often reported in the stripeordered phase.

  14. Electronic state and superconductivity of YBa2Cu3-xO7-y (M=Al,Zn and Sn) systems

    Science.gov (United States)

    Zhao, Y.; Zhang, Q. R.; Zhang, H.

    1990-01-01

    A series of YBa2Cu(3-x)MxO(7-y) (M=Al,Zn and Sn) single phase samples were prepared, and the measurements of the crystal structure, oxygen content, electric resistivity, thermoelectric power, Mossbauer spectrum, XPS and superconductivity were performed. The experimental results of X ray powder diffraction, Mossbauer spectrum and oxygen content show that the Zn(2+) and the Al(3+) occupy the Cu(2) site in Cu-O planes and the Cu(1) site in Cu-O chains respectively, but the Sn(4+) occupies both the Cu(1) sites. As regards the properties in superconducting state, both the Zn(2+) and the Al(3+) depress T(sub c) strongly, but the Sn(4+) does not. As for the electronic transport properties in normal state, the system doped by Al(3+) displays a rapid increase of resistivity and some electron localization-like effects, and the thermoelectric power enhances obviously; the series contained Zn(2+) almost shows no changes of electric resistivity but the sign of the thermoelectric power is reversed. Other results are given and briefly discussed.

  15. Highly-textured thallium-barium-calcium-copper-oxide polycrystalline superconducting films on silver substrates

    Energy Technology Data Exchange (ETDEWEB)

    Arendt, P.; Elliott, N.; Cooke, D.W.; Dye, R.; Gray, E.; Hubbard, K.; Martin, J.; Reeves, G.; Brown, D.; Klapetzky, A.

    1990-01-01

    Thick (8 to 10 {mu}m) Ba--Ca--Cu--O films have been rf magnetron sputtered onto Ag alloy (Consil 995) substrates. The films were given a post-deposition anneal in an over pressure of Tl in order to form the superconducting phases. Annealing protocols were done which result in predominantly the 1212 and 2212 phases. The substrate orientation was varied to determine its effect on film orientation. Material properties of the films were characterized by x-ray diffraction (XRD), ion beam backscattering spectroscopy, energy dispersive x-ray analysis (EDAX), and scanning electron microscopy (SEM). Electrical characterization of the films was done using dynamic impedance (DI) at 10 kHz and rf surface resistance (R{sub s}) at 18 GHz in a TE{sub 011} fundamental mode cavity. 19 refs., 7 figs.

  16. Cupric Oxide (CuO) Oxidation Detects Pyrogenic Carbon in Burnt Organic Matter and Soils.

    Science.gov (United States)

    Hatten, Jeff; Goñi, Miguel

    2016-01-01

    Wildfire greatly impacts the composition and quantity of organic carbon stocks within watersheds. Most methods used to measure the contributions of fire altered organic carbon-i.e. pyrogenic organic carbon (Py-OC) in natural samples are designed to quantify specific fractions such as black carbon or polyaromatic hydrocarbons. In contrast, the CuO oxidation procedure yields a variety of products derived from a variety of precursors, including both unaltered and thermally altered sources. Here, we test whether or not the benzene carboxylic acid and hydroxy benzoic acid (BCA) products obtained by CuO oxidation provide a robust indicator of Py-OC and compare them to non-Py-OC biomarkers of lignin. O and A horizons from microcosms were burned in the laboratory at varying levels of fire severity and subsequently incubated for 6 months. All soils were analyzed for total OC and N and were analyzed by CuO oxidation. All BCAs appeared to be preserved or created to some degree during burning while lignin phenols appeared to be altered or destroyed to varying extents dependent on fire severity. We found two specific CuO oxidation products, o-hydroxybenzoic acid (oBd) and 1,2,4-benzenetricarboxylic acid (BTC2) that responded strongly to burn severity and withstood degradation during post-burning microbial incubations. Interestingly, we found that benzene di- and tricarboxylic acids (BDC and BTC, respectively) were much more reactive than vanillyl phenols during the incubation as a possible result of physical protection of vanillyl phenols in the interior of char particles or CuO oxidation derived BCAs originating from biologically available classes of Py-OC. We found that the ability of these compounds to predict relative Py-OC content in burned samples improved when normalized by their respective BCA class (i.e. benzene monocarboxylic acids (BA) and BTC, respectively) and when BTC was normalized to total lignin yields (BTC:Lig). The major trends in BCAs imparted by burning

  17. Simple Superconducting "Permanent" Electromagnet

    Science.gov (United States)

    Israelson, Ulf E.; Strayer, Donald M.

    1992-01-01

    Proposed short tube of high-temperature-superconducting material like YBa2Cu3O7 acts as strong electromagnet that flows as long as magnetic field remains below critical value and temperature of cylinder maintained sufficiently below superconducting-transition temperature. Design exploits maximally anisotropy of high-temperature-superconducting material.

  18. Spin density wave induced disordering of the vortex lattice in superconducting La2xSrxCuO4

    DEFF Research Database (Denmark)

    Chang, J.; White, J.S.; Laver, M.

    2012-01-01

    We use small-angle neutron scattering to study the superconducting vortex lattice in La2-xSrxCuO4 as a function of doping and magnetic field. We show that near optimally doping the vortex lattice coordination and the superconducting coherence length. are controlled by a Van Hove singularity cross...

  19. Oxidation of Carbon Monoxide over Cu/CeO2 Catalysts Prepared by SMAI

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Supported Cu catalysts for low-temperature CO oxidation were prepared by solvated metal atom impregnation (SMAI). X-ray photoelectron spectroscopy (XPS) investigations indicated that the copper in all the samples was in a metallic state. XRD measurements showed that the mean diameters of Cu particles prepared by SMAI were small. Catalytical tests showed that the SMAI catalyst had high CO oxidation activity.

  20. Superconductivity in the Tl-Ca-Ba-Cu-O System:. Synthesis, Characterization and Mechanism

    Science.gov (United States)

    Ganguli, A. K.; Swamy, K. S. Nanjunda; Subbanna, G. N.; Rajumon, M. K.; Sarma, D. D.; Rao, C. N. R.

    Synthesis and characterization of some of the members of the Tl-Ca-Ba-Cu-O system are presented. Tc in both the TlCan-1Ba2CunO2n+3 and Tl2Can-1Ba2CunO2n+4 series increase with the number of Cu-O layers, n; Tc in the latter series with two Tl-O layers are generally higher than in the former with a single Tl-O layer. Tl in the cuprates is in the 3+ state while Cu is in the 1+ and 2+ states, showing the importance of oxygen holes. The concentration of these holes seems to increase with the number of Tl-O layers.

  1. Effect of Pressure on Magneto-Transport Properties in the Superconducting and Normal Phases of the Metallic Double Chain Compound Pr2Ba4Cu7O15-δ

    Science.gov (United States)

    Kuwabara, Masayoshi; Matsukawa, Michiaki; Sugawara, Keisuke; Taniguchi, Haruka; Matsushita, Akiyuki; Hagiwara, Makoto; Sano, Kazuhiro; Ōno, Yoshiaki; Sasaki, Takahiko

    2016-12-01

    To examine the electronic phase diagram of superconducting CuO double chains, we report the effect of external pressure on the magneto-transport properties in superconducting and non-superconducting polycrystalline samples of Pr2Ba4Cu7O15-δ at low temperatures (1.8-40 K) under various magnetic fields (up to 14 T). In the as-sintered non-superconducting sample, the magneto-resistance (MR) follows a power law of H3/2 at low temperatures, which is in no agreement with the H2 dependence of MR in the PrBa2Cu4O8 system. The negative pressure dependence of the superconducting phase is qualitatively consistent with a theoretical prediction on the basis of the Tomonaga-Luttinger liquid theory. The 48-h-reduced superconducting sample at ambient pressure exhibits no clear increase in MR for T > Tc,on = 26.5 K. In contrast, with the application of pressure to the superconducting sample, the MR effects reappear and are also well fitted by H3/2. The model of slightly warped Fermi surfaces explains not only the MR effect of the non-superconducting sample, but is also related to the reasons for the pressure-induced MR phenomena of the superconducting sample.

  2. Multicomponent (Ce, Cu, Ni) oxides with cage and core-shell structures: tunable fabrication and enhanced CO oxidation activity

    Science.gov (United States)

    Liu, Wei; Tang, Ke; Lin, Ming; June, Lay Ting Ong; Bai, Shi-Qiang; Young, David James; Li, Xu; Yang, Yan-Zhao; Hor, T. S. Andy

    2016-05-01

    Solvothermal synthesis of Cu2O cubes from Cu(OAc)2 in ethanol provided templates for tunable formation of novel multicomponent composites: hollow CeO2-Cu2O (1), core-shell NiO@Cu2O (2) and hollow CeO2-NiO-Cu2O (3). Composites 1-3 catalyze the oxidation of CO at a lower temperature than the parent Cu2O cubes.Solvothermal synthesis of Cu2O cubes from Cu(OAc)2 in ethanol provided templates for tunable formation of novel multicomponent composites: hollow CeO2-Cu2O (1), core-shell NiO@Cu2O (2) and hollow CeO2-NiO-Cu2O (3). Composites 1-3 catalyze the oxidation of CO at a lower temperature than the parent Cu2O cubes. Electronic supplementary information (ESI) available: Experimental section: materials and characterization; synthesis of materials; catalytic test. Tables S1-S3 and Fig. S1-S8. See DOI: 10.1039/c6nr02383e

  3. Pressure effect on the superconductivity and the metal-insulator transition in Cu sub 1 sub sub - sub x Zn sub x Ir sub 2 S sub 4

    CERN Document Server

    Cao, G; Kitazawa, H; Isobe, M; Matsumoto, T

    2002-01-01

    The variations of the superconducting transition temperature T sub c and the metal-insulator (MI) transition temperature T sub M sub I were investigated as a function of pressure in the superconducting Cu sub 1 sub sub - sub x Zn sub x Ir sub 2 S sub 4 (0.3 <= x <= 0.5) system. The experiment was performed by measuring the temperature dependence of resistance under the pressures up to 1.5 GPa. It is shown that the external pressure destroys the superconductivity, and gives rise to the MI transitions. The result is discussed in terms of the stabilization of the insulating phase at high pressures and the phase separation associated with the charge segregation. It is proposed that the BCS Cooper pairs compete with the proposed bipolarons under certain pressures.

  4. Anomalous spectral weight transfer at the superconducting transition of Bi sub 2 Sr sub 2 CaCu sub 2 O sub 8+. delta

    Energy Technology Data Exchange (ETDEWEB)

    Dessau, D.S.; Wells, B.O.; Shen, Z.; Spicer, W.E. (Stanford Electronics Laboratories, Stanford University, Stanford, California 94305 (USA)); Arko, A.J.; List, R.S. (Los Alamos National Laboratories, Los Alamos, New Mexico 87545 (USA)); Mitzi, D.B.; Kapitulnik, A. (Department of Applied Physics, Stanford University, Stanford, California 94305 (USA))

    1991-04-22

    Anomalous spectral weight transfer at the superconducting transition of single-crystalline Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}} was observed by high-resolution angle-resolved photoemission spectroscopy. As the sample goes superconducting, not only is there spectral weight transfer from the gap region to the pileup peak as in BCS theory, but along the {Gamma}-{ital {bar M}} direction there is also some spectral weight transfer from higher binding energies in the form of a dip. In addition, we note that at the superconducting transition there is a decrease (increase) in the occupied spectral weight for the spectra taken along {Gamma}-{ital {bar M}} ({Gamma}-{ital X}).

  5. Investigation of the superconducting gap structure in κ-(BEDT-TTF)2Cu(NCS)2 and κ-(BEDT-TTF)2Cu[N(CN)2]Br by means of thermal-conductivity measurements

    Science.gov (United States)

    Kühlmorgen, S.; Schönemann, R.; Green, E. L.; Müller, J.; Wosnitza, J.

    2017-10-01

    We report temperature-dependent thermal-conductivity, κ, measurements on the layered quasi-two-dimensional organic superconductors κ-(BEDT-TTF)2Cu(NCS)2 and κ-(BEDT-TTF)2Cu[N(CN)2]Br down to 160 mK. The results for κ-(BEDT-TTF)2Cu(NCS)2 may be consistent with a nodal superconducting (SC) gap structure as indicated by a non-negligible remnant linear contribution when κ/T \\propto T2 is extrapolated to T = 0 . For κ-(BEDT-TTF)2Cu[N(CN)2]Br, contrary to expectations, higher κ values are observed in the superconducting regime as compared to the normal, high-field state evidencing a dominant phonon contribution to κ in the superconducting state. The strong increase of κ in the normal state below T c for both samples indicates strong electron–phonon scattering. Our results highlight the need for thermal-conductivity measurements performed down to significantly lower temperatures to determine the symmetry of the SC gap.

  6. Y1Ba2Cu3O(7-delta) thin film dc SQUIDs (superconducting quantum interference device)

    Science.gov (United States)

    Racah, Daniel

    1991-03-01

    Direct current superconducting quantum interferometers (SQUIDs) based on HTSC thin films have been measured and characterized. The thin films used were of different quality: (1) Granular films on Sapphire substrates, prepared either by e-gun evaporation, by laser ablation or by MOCVD (metal oxide chemical vapor deposition), (2) Epitaxial films on MgO substrates. Modulations of the voltage on the SQUIDs as a function of the applied flux have been observed in a wide range of temperatures. The nature of the modulation was found to be strongly dependent on the morphology of the film and on its critical current. The SQUIDs based on granular films were relatively noisy, hysteretic and with a complicated V-phi shape. Those devices based on low quality (lowIc) granular films could be measured only at low temperatures (much lower than 77 K). While those of higher quality (granular films with high Ic) could be measured near to the superconductive transition. The SQUID based on high quality epitaxial film was measured near Tc and showed an anomalous, time dependent behavior.

  7. The relationship between open volume defects and deposition conditions of superconducting thin-film YBa sub 2 Cu sub 3 O sub 7 sub - sub x

    CERN Document Server

    Zhou, X Y; Jiang, H; Bauer-Kugelmann, W; Duffy, J A; Koegel, G; Triftshaeuser, W

    1997-01-01

    The relationship between the open volume defects and the deposition conditions of superconducting thin-film YBa sub 2 Cu sub 3 O sub 7 sub - sub x was studied by the position lifetime technique. Using a low-energy pulsed positron system, positron lifetime as a function of implantation energy was measured on epitaxial superconducting thin-film YBa sub 2 Cu sub 3 O sub 7 sub - sub x deposited on yttrium stabilized cubic zirconia substrates (YSZ) with pulsed laser deposition in a partial pressure of air under different conditions. The results show that the type of open volume defect is independent of deposition conditions such as the substrate temperature, T sub s , and the air pressure, P sub a. The defect concentration increases with decreasing T sub s and increasing P sub a. (author). Letter-to-the-editor

  8. Local structure, stripe pinning, and superconductivity in La1.875Ba0.125CuO4 at high pressure

    Science.gov (United States)

    Fabbris, G.; Hücker, M.; Gu, G. D.; Tranquada, J. M.; Haskel, D.

    2013-08-01

    The interplay between stripe correlations, local structure, and superconductivity in La1.875Ba0.125CuO4 is studied with concomitant polarized x-ray absorption fine structure (XAFS) and x-ray diffraction measurements at high pressure. Long-range order of the CuO6 octahedral tilt pattern that pins charge-stripe order vanishes at a pressure-induced structural transition (P=1.8 GPa at T=5 K). Diffraction shows that static charge stripe and associated octahedral tilt correlations which survive in the high-pressure phase are effectively suppressed above 3.5 GPa. In contrast, XAFS analysis shows that instantaneous local correlations of the characteristic octahedral tilt pattern remain robust to at least 5 GPa. The decreasing local tilt angle is well correlated with a gradual increase in the superconducting transition temperature, suggesting that orientational pinning of charge correlations can survive the loss of static stripe order.

  9. Maximum allowable currents in YBa2Cu3O7 superconducting tapes as a function of the coating thickness, external magnetic field induction, and cooling conditions

    Science.gov (United States)

    Arkharov, A. M.; Dontsova, E. S.; Lavrov, N. A.; Romanovskii, V. R.

    2014-04-01

    Maximum allowable (ultimate) currents stably passing through an YBa2Cu3O7 superconducting current-carrying element are determined as a function of a silver (or copper) coating thickness, external magnetic field induction, and cooling conditions. It is found that if a magnetic system based on yttrium ceramics is cooled by a cryogenic coolant, currents causing instabilities (instability onset currents) are almost independent of the coating thickness. If, however, liquid helium is used as a cooling agent, the ultimate current monotonically grows with the thickness of the stabilizing copper coating. It is shown that depending on cooling conditions, the stable values of the current and electric field strength preceding the occurrence of instability may be both higher and lower than the a priori chosen critical parameters of the superconductor. These features should be taken into account in selecting the stable value of the operating current of YBa2Cu3O7 superconducting windings.

  10. On the effect of Cd doping for Ca in La 3CaBa 3Cu 7O y superconducting cuprate

    Science.gov (United States)

    Kandyel, Elsayed; Elsabawy, Khaled M.

    2006-02-01

    We report on the influence of isovalent substitution of Cd 2+ for Ca 2+ on the structural, electrical and magnetic properties of La 3CaBa 3Cu 7O y. Based on X-ray diffraction and DSC measurements, Cd can replace upto 100% of Ca ions without affecting the basic crystal structure or the formation of any impurity phases. Both Tc and oxygen content decrease monotonously with Cd content. Contrary to Y-123, the transition from the region of maximal Tc to the non-superconducting state takes place within a narrow range of oxygen content. The difference in chemical properties between Cd and Ca, as well as the observed concomitant decrease in the oxygen content, is believed to be responsible for the structural changes and suppression of superconductivity through the reduction of oxygen in the Cu-O layers when Cd replaces Ca.

  11. On the effect of Cd doping for Ca in La{sub 3}CaBa{sub 3}Cu{sub 7}O {sub y} superconducting cuprate

    Energy Technology Data Exchange (ETDEWEB)

    Kandyel, Elsayed [Faculty of Science, Department of Chemistry, Tanta University, Tanta 31527 (Egypt)]. E-mail: skandyel@yahoo.com; Elsabawy, Khaled M. [Faculty of Science, Department of Chemistry, Tanta University, Tanta 31527 (Egypt)

    2006-02-15

    We report on the influence of isovalent substitution of Cd{sup 2+} for Ca{sup 2+} on the structural, electrical and magnetic properties of La{sub 3}CaBa{sub 3}Cu{sub 7}O {sub y}. Based on X-ray diffraction and DSC measurements, Cd can replace upto 100% of Ca ions without affecting the basic crystal structure or the formation of any impurity phases. Both T {sub c} and oxygen content decrease monotonously with Cd content. Contrary to Y-123, the transition from the region of maximal T {sub c} to the non-superconducting state takes place within a narrow range of oxygen content. The difference in chemical properties between Cd and Ca, as well as the observed concomitant decrease in the oxygen content, is believed to be responsible for the structural changes and suppression of superconductivity through the reduction of oxygen in the Cu-O layers when Cd replaces Ca.

  12. Characterization of the native oxide of CuInSe2 using synchrotron radiation photoemission

    Science.gov (United States)

    Nelson, Art J.; Gebhard, Steven; Kazmerski, L. L.; Colavita, Elio; Engelhardt, Mike; Höchst, Hartmut

    1990-10-01

    Synchrotron radiation soft x-ray photoemission spectroscopy was used to investigate the native oxide of n-type single-crystal CuInSe2. Photoemission measurements were acquired on the oxide surface before and after removal using sputter etching. Observed changes in the valence-band electronic structure as well as changes in the In 4d and Se 3d core lines were correlated with the interface chemistry at the oxide/CuInSe2 interface. These results show the native oxide to be composed of an In2O3 outer layer (no SeO2) with an additional Cu2Se interface layer.

  13. Apical oxygen, 3D-2D cross over and superconductivity in Sm{sub 2-x}Ce{sub x}CuO{sub 4-{delta}}

    Energy Technology Data Exchange (ETDEWEB)

    Boujida, M. [Laboratory of Signals Systems and Components LSSC, Department of Electrical Engineering School, Faculty of Sciences and Techniques, University of Sidi Mohammed Ben Abdellah, Route d' Immouzer BP 2202, Fes (Morocco)

    2006-09-15

    In spite of the vast amount of experimental and theoretical articles accumulated in HTSC, the mechanism of the interaction driving charge carriers to form Cooper pairs below T{sub c} is still unknown. The comparison of the normal state transport properties of YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} and the Sm{sub 2-x}Ce{sub x}CuO{sub 4-{delta}} [1, 2] might shed some light on the microscopic origin of HTSC. In comparison to the YBCO, the apical oxygen in Sm{sub 2-x}Ce{sub x}CuO{sub 4-{delta}} [3] destroys the superconductivity via the vertical ionic bonding which localizes the charge in the Cu-O squares, however the hole transfer by moving O(4) towards the CuO{sub 2} planes, leads to the optimization of YBCO properties. The behaviour of C axis parameter vs the oxygen content cannot be explained by a BSC mechanism. The high amount of anisotropy ratio [4] is explained by the sheer square planes in NCCO system, i.e. without apical oxygen (SC with T{sub c} maximum). From the data of the resistivity in the normal state, we conclude the observation of a 3D-2D cross over only in Sm{sub 2-x}Ce{sub x}CuO{sub 4-{delta}} [2] and Nd{sub 2-x}Ce{sub x}CuO{sub 4-{delta}} [5] which is also related to its high anisotropy. The competition between anisotropy and superconductivity destroys the superconducting state in the 2D limit even in the ground state. In this material the superconductivity cannot be enhanced at high temperature because the compound is a quasi 2D system (sheer square planes of CuO{sub 2}) and the cuprate superconductors is a genuine three-dimensional (3D) phenomenon [6]. The Josephson coupling between the different layers is S-I-S for NCCO and S-N-S for YBCO, thus the Lawrence and Doniach model (LD) [7] with neighbouring layers coupled by the Josephson tunnelling is appropriate. In summary the behaviour of apical oxygen is intrinsically different in the two kinds of cuprates. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  14. Combinative energy,oxygen deficiency and superconductivity in LnBa2Cu3O7-x (Ln=Nd,Er,Sm)

    Institute of Scientific and Technical Information of China (English)

    王淑霞; 刘文利; 韩圣浩; 张酣

    2003-01-01

    The correlation among the combinative energy, superconductivity, oxygen content, the position of holes in different planes, and the position of holes in the Cu(2)-O plane in LnBa2Cu3O7-x (Ln= Nd, Er, and Sm) has been investigated on the basis of a block model. The results indicate that the combinative energy decreases with increasing Tc in all of these compounds. And also, the combinative energies are obviously different with holes at different positions in the Cu(2)-O plane when the oxygen deficiency is low. However, this difference becomes less with increasing the oxygen deficiency.The effect of the holes in different positions on the combinative energy supplies some clue to the understanding of an unresolved problem, i.e. whether the distribution of carriers in the CuO2 plane is uniform or inhomogeneous. The results not only show that the structural characters, the combinative energy between two structural blocks and the superconductivity are closely interrelated in this class of compounds, but also reveal some differences among these systems. The relationship between the combinative energy and the Tc value in NdBa2Cu3O7-x shows some features different from the systems containing Er or Sm.

  15. Reassessment of the electronic state, magnetism, and superconductivity in high-T{sub c} cuprates with the Nd{sub 2}CuO{sub 4} structure

    Energy Technology Data Exchange (ETDEWEB)

    Naito, Michio, E-mail: minaito@cc.tuat.ac.jp [Department of Applied Physics, Tokyo University of Agriculture and Technology, Naka-cho 2-24-16, Koganei, Tokyo 184-8588 (Japan); Krockenberger, Yoshiharu; Ikeda, Ai; Yamamoto, Hideki [NTT Basic Research Laboratories, NTT Corporation, 3-1 Morinosato-Wakamiya, Atsugi, Kanagawa 243-0198 (Japan)

    2016-04-15

    Highlights: • The 30-year history of “electron-doped” cuprates is reviewed, including basic physics and material issues. • Undoped cuprates with the Nd{sub 2}CuO{sub 4} (T’) structure are superconducting with T{sub c} over 30 K. • Electron doping by Ce in T’-RE{sub 2}CuO{sub 4} lowers T{sub c} and the highest T{sub c} is obtained at no doping. - Abstract: The electronic phase diagram of the cuprates remains enigmatic and is still a key ingredient to understand the mechanism of high-T{sub c} superconductivity. It has been believed for a long time that parent compounds of cuprates were universally antiferromagnetic Mott insulators (charge-transfer insulators) and that high-T{sub c} superconductivity would develop upon doping holes or electrons in a Mott–Hubbard insulator (“doped Mott-insulator scenario”). However, our recent discovery of superconductivity in the parent compounds of square-planar cuprates with the Nd{sub 2}CuO{sub 4} (T’) structure and the revised electronic phase diagram in T’ cuprates urged a serious reassessment to the above scenario. In this review, we present the main results derived from our synthesis and experiments on T’ cuprates in the undoped or heavily underdoped regime over 20 years, including material issues and basic physics. The key material issue is how to remove excess oxygen ions at the apical site without introducing oxygen vacancies in the CuO{sub 2} planes. In order to put this into practice, the basic knowledge of complex solid-state chemistry in T’ cuprates is required, which is also included in this review.

  16. Oxidation behavior of Cu nanoparticles embedded into semiconductive TiO{sub 2} matrix

    Energy Technology Data Exchange (ETDEWEB)

    Stranak, Vitezslav, E-mail: stranak@prf.jcu.cz [University of South Bohemia, Faculty of Science, Branisovska 31, 37005 Ceske Budejovice (Czech Republic); Drache, Steffen; Wulff, Harm [University of Greifswald, Institute of Physics, Felix-Hausdorff-Str. 6, 17489 Greifswald (Germany); Hubicka, Zdenek [Institute of Physics, Academy of Science of the Czech Republic, Na Slovance 2, 18221 Prague (Czech Republic); Tichy, Milan [Charles University in Prague, Faculty of Mathematics and Physics, V Holesovickach 2, 18000 Prague (Czech Republic); Kruth, Angela [Leibniz Institute for Plasma Science and Technology, INP Greifswald e.V., Felix-Hausdorff-Straße 2, 17489 Greifswald (Germany); Helm, Christiane A.; Hippler, Rainer [University of Greifswald, Institute of Physics, Felix-Hausdorff-Str. 6, 17489 Greifswald (Germany)

    2015-08-31

    Metal nanoparticles embedded into a semiconductive matrix represent a promising material for widely sought advanced technological applications. We focused our interest on the preparation of TiO{sub 2} matrix with embedded Cu nanoparticles. In particular, we studied the effect of reactive discharge (Ar/O{sub 2}) exposition on copper oxidation, which can result in two stable forms: cuprous oxide (Cu{sub 2}O) and cupric oxide (CuO). Copper nanoparticles, of size in range 10–50 nm, were produced by magnetron sputtering in combination with gas aggregation. The beam of Cu nanoparticles was impinging onto a silicon substrate which was directly exposed to a reactive Ar/O{sub 2} magnetron discharge providing sputtering of Ti target at the same time. The properties of deposited nanocomposite Cu({sub x}O)–TiO{sub 2} were investigated by X-ray photoelectron spectroscopy, grazing incidence X-ray diffractometry, X-ray reflectometry and scanning electron microscopy techniques to reveal the nanocomposite properties and to understand the oxidation process of embedded Cu nanoparticles. It was found that CuO is preferentially formed if copper is exposed to active oxygen species (O{sup +}, O{sup −}, O{sup ⁎} etc.) produced in the reactive magnetron discharge. On the other hand, Cu{sub 2}O was observed in the case of copper reaction in ambient Ar/O{sub 2} atmosphere. As a result, two possible copper oxidation mechanisms are proposed, employing chemical kinetics. - Highlights: • Cu–TiO{sub 2} nanocomposite was prepared by plasma assisted methods. • Embedded Cu always occurs in oxidized phase depending on the way of oxidation. • CuO is formed if copper is exposed to active oxygen species produced in Ar/O{sub 2} discharge. • Cu{sub 2}O appears in the case of copper reaction in an ambient oxygen-based atmosphere. • Two possible copper oxidation mechanisms are proposed.

  17. Characteristics of oxide scale formed on Cu-bearing austenitic stainless steel during early stages of high temperature oxidation

    Science.gov (United States)

    Swaminathan, Srinivasan; Krishna, Nanda Gopala; Kim, Dong-Ik

    2015-10-01

    Oxide scale evolution on Cu-bearing austenitic stainless steel 304H at 650 °C, in ambient air, for exposure times 100, 300, 500 and 1000 h, has been investigated. Surface morphology and chemistry of the oxide scale grown were examined using SEM/EDX and XPS. The oxidation kinetics was determined by measuring the weight change using an electronic balance. At the initial stage, up to 500 h of exposure time, the oxidation rate was rapid due to surface reactions governed primarily by oxygen ingress, and then, dropped to a low rate after prolonged oxidation for 1000 h. The diffusion of reactants through the initially formed oxide scale limits the oxidation rate at longer times, thus, the progress of reaction followed the parabolic kinetics. The formed oxide scale was enriched significantly with segregation and subsequent oxidation of Nb, and finely dispersed metallic Cu particles. Within the time frame of oxidation, the oxide scale was mainly composed of mixed oxides such as FeCr2O4 and MnCr2O4 along with the binary oxides of Fe, Cr and Mn. Moreover, the precipitation fraction of Cu-rich particles on the oxide scale increased markedly with increase of exposure times. The chemical heterogeneity of oxide scale suggests that the oxidation occurred in a non-selective manner.

  18. Mass distribution of cluster ions produced from laser ablation of metal-composite-oxides Y-M-Cu-O (M = Ba, Sr, Ca, Mg)

    Energy Technology Data Exchange (ETDEWEB)

    Liu Zhaoyang; Wang Chunru; Huang Rongbin; Zheng Lansun [Xiamen Univ. (China). Dept. of Chem.

    1995-09-01

    Laser ablation of YMCuO metal-composite-oxides (M = Ba, Sr, Ca, Mg) in high vacuum produced cluster ions with various sizes and compositions. Mass spectra of the cluster ions were recorded by a home-built time-of-flight (TOF) mass spectrometer and the mass distributions were analyzed by a statistical model. For YBa{sub 2}Cu{sub 3}O{sub 7-x} (YBCO) high-Tc superconducting samples, six series of cluster ions were observed. Replacement of barium in the metal-composite-oxide sample with other alkaline earth metal, such as strontium, calcium, or magnesium, not only removed the superconductivity, but also changed the compositions and distributions of the laser generated cluster ions. For instance, copper was only found in the compositions of cluster ions generated from YBCO sample. From comparison of the experimental results, interactions among components of the metal-composite-oxides and the function of alkaline earth metal in superconducting material were discussed. (orig.) 19 refs.

  19. Electrodeposition of PdCu alloy and its application in methanol electro-oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Hsieh, Ming-Wei [Department of Chemistry, National Cheng Kung University, 1 University Road, Tainan 70101, Taiwan (China); Whang, Thou-Jen, E-mail: twhang@mail.ncku.edu.tw [Department of Chemistry, National Cheng Kung University, 1 University Road, Tainan 70101, Taiwan (China)

    2013-04-01

    This study demonstrates a simple electrodeposition method to fabricate the palladium–copper alloy on an ITO coated glass (PdCu/ITO) and its application in methanol electro-oxidation. Our approaches involve the co-reduction of Pd and Cu using triethanolamine (TEA) as a complexing agent in the electroplating bath and a Pd redox replacement of Cu on the surface of the as-prepared PdCu alloy. The phase structures, alloy compositions and morphologies of catalysts are determined by X-ray diffraction, energy dispersive spectrometer and scanning electron microscopy, respectively. X-ray diffraction shows that the particle size of PdCu deposits shrink when the alloy is deposited in a TEA-contained solution. The electrocatalytic properties of PdCu alloys and Pd redox replacement modified PdCu alloys for methanol oxidation have been investigated by cyclic voltammetry. The PdCu alloy with atomic ratio of 20.5% Cu exhibits higher catalytic activity toward methanol oxidation compared with a pure Pd catalyst. PdCu alloys with smaller particle sizes associated with TEA agent and the surface confined Pd replacement are found to have enhanced catalytic performance in the electro-oxidation of methanol.

  20. Superconductivity up to 110 K in Bi/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/0/sub 10/ compounds

    Energy Technology Data Exchange (ETDEWEB)

    Lejay, P.; Rango, P. de; Sulpice, A.; Giordanengo, B.; Tournier, R.; Retoux, R.; Deslandes, S.; Michel, C.; Hervieu, M.; Raveau, B.

    1989-05-01

    In the Bi-Sr-Ca-Cu-0 system, we have studied the compound with the ideal formula Bi/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/0/sub 10/, responsible for the superconductivity up to 110 K. The magnetic measurements reveal the presence of two phases in the samples with superconducting transitions up to 80 K and 110 K. By varying the composition and the thermal treatment of those samples, we have succeeded in increasing the amount of the superconducting phase with T/sub c/ up to 110 K. The Meissner effect reaches 30 % of - 3/8 ..pi.. at 90 K for the undoped samples and more than 50 % for the samples doped with Pb. Because of the high reversibility of the magnetization versus magnetic field around T/sub c/, we have evaluated the critical thermodynamic field. This one gives an electronic specific heat coefficient similar to the one of YBaCu0 compounds.

  1. Uniaxial Linear Resistivity of Superconducting La1.905Ba0.095CuO4 Induced by an External Magnetic Field

    Energy Technology Data Exchange (ETDEWEB)

    Wen J.; Jie, Q.; Li, Q.; Hucker, M.; Zimmermann, M.v.; Han, S.J.; Xu, Z.; Singh, D.K.; Konik, R.M.; Zhang, L.; Gu, G.; Tranquada, J.M.

    2012-04-12

    We present an experimental study of the anisotropic resistivity of superconducting La{sub 2-x}Ba{sub x}CuO{sub 4} with x = 0.095 and transition temperature T{sub c}=32 K. In a magnetic field perpendicular to the CuO{sub 2} layers H{perpendicular}, we observe that the resistivity perpendicular to the layers {rho}{perpendicular} becomes finite at a temperature consistent with previous studies on very similar materials; however, the onset of finite parallel resistivity {rho}{parallel} occurs at a much higher temperature. This behavior contradicts conventional theory, which predicts that {rho}{perpendicular} and {rho}{parallel} should become finite at the same temperature. Voltage versus current measurements near the threshold of voltage detectability indicate linear behavior perpendicular to the layers, becoming nonlinear at higher currents, while the behavior is nonlinear from the onset parallel to the layers. These results, in the presence of moderate H{perpendicular}, appear consistent with superconducting order parallel to the layers with voltage fluctuations between the layers due to thermal noise. In search of uncommon effects that might help to explain this behavior, we have performed diffraction measurements that provide evidence for H{perpendicular}-induced charge- and spin-stripe order. The field-induced decoupling of superconducting layers is similar to the decoupled phase observed previously in La{sub 2-x}Ba{sub x}CuO{sub 4} with x=1/8 in zero field.

  2. Uniaxial linear resistivity of superconducting La1.905Ba0.095CuO4 induced by an external magnetic field

    Science.gov (United States)

    Wen, Jinsheng; Jie, Qing; Li, Qiang; Hücker, M.; v. Zimmermann, M.; Han, Su Jung; Xu, Zhijun; Singh, D. K.; Konik, R. M.; Zhang, Liyuan; Gu, Genda; Tranquada, J. M.

    2012-04-01

    We present an experimental study of the anisotropic resistivity of superconducting La2-xBaxCuO4 with x=0.095 and transition temperature Tc=32 K. In a magnetic field perpendicular to the CuO2 layers H⊥, we observe that the resistivity perpendicular to the layers ρ⊥ becomes finite at a temperature consistent with previous studies on very similar materials; however, the onset of finite parallel resistivity ρ∥ occurs at a much higher temperature. This behavior contradicts conventional theory, which predicts that ρ⊥ and ρ∥ should become finite at the same temperature. Voltage versus current measurements near the threshold of voltage detectability indicate linear behavior perpendicular to the layers, becoming nonlinear at higher currents, while the behavior is nonlinear from the onset parallel to the layers. These results, in the presence of moderate H⊥, appear consistent with superconducting order parallel to the layers with voltage fluctuations between the layers due to thermal noise. In search of uncommon effects that might help to explain this behavior, we have performed diffraction measurements that provide evidence for H⊥-induced charge- and spin-stripe order. The field-induced decoupling of superconducting layers is similar to the decoupled phase observed previously in La2-xBaxCuO4 with x=1/8 in zero field.

  3. Testing the Itinerancy of Spin Dynamics in Superconducting Bi2Sr2CaCu2O8C+δ

    Energy Technology Data Exchange (ETDEWEB)

    Xu, G.; Gu, G.D.; Hücker, M.; Fauqué, B.; Perring, T.G.; Regnault, L.P.; Tranquada, J.M.

    2009-09-01

    Much of what we know about the electronic states of high-temperature superconductors is due to photoemission and scanning tunnelling spectroscopy studies of the compound Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}}. The demonstration of well-defined quasiparticles in the superconducting state has encouraged many theorists to apply the conventional theory of metals, Fermi-liquid theory, to the cuprates. In particular, the spin excitations observed by neutron scattering at energies below twice the superconducting gap energy are commonly believed to correspond to an excitonic state involving itinerant electrons. Here, we present the first measurements of the magnetic spectral weight of optimally doped Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}} in absolute units. The lack of temperature dependence of the local spin susceptibility across the superconducting transition temperature, T{sub c}, is incompatible with the itinerant calculations. Alternatively, the magnetic excitations could be due to local moments, as the magnetic spectrum is similar to that in La{sub 1.875}Ba{sub 0.125}CuO{sub 4}, where quasiparticles and local moments coexist.

  4. Prepared GdBa2 Cu3Oy Single Domain Superconducting Bulks in Air

    Institute of Scientific and Technical Information of China (English)

    Zheng Minghui; Xiao Ling; Ren Hongtao; Jiao Yulei; Xu Bin; Fang Yuan

    2004-01-01

    The preparation of the single domain GBCO bulk with 25 mm in diameter in air was reported. In order to avoid the Gd ions substituted the Ba sites, different BaCuO2 contents was added into the precursor powders. Tc of the samples achieved 94.3 K. The magnetization hysteresis loops of the samples were measured at 77 K. It is shown that the irreverswas obtained.

  5. Itinerant Ferromagnetism and Superconductivity

    OpenAIRE

    Karchev, Naoum

    2004-01-01

    Superconductivity has again become a challenge following the discovery of unconventional superconductivity. Resistance-free currents have been observed in heavy-fermion materials, organic conductors and copper oxides. The discovery of superconductivity in a single crystal of $UGe_2$, $ZrZn_2$ and $URhGe$ revived the interest in the coexistence of superconductivity and ferromagnetism. The experiments indicate that: i)The superconductivity is confined to the ferromagnetic phase. ii)The ferromag...

  6. Interfacial Cu+ promoted surface reactivity: Carbon monoxide oxidation reaction over polycrystalline copper-titania catalysts

    Science.gov (United States)

    Senanayake, Sanjaya D.; Pappoe, Naa Adokaley; Nguyen-Phan, Thuy-Duong; Luo, Si; Li, Yuanyuan; Xu, Wenqian; Liu, Zongyuan; Mudiyanselage, Kumudu; Johnston-Peck, Aaron C.; Frenkel, Anatoly I.; Heckler, Ilana; Stacchiola, Dario; Rodriguez, José A.

    2016-10-01

    We have studied the catalytic carbon monoxide (CO) oxidation (CO + 0.5O2 → CO2) reaction using a powder catalyst composed of both copper (5 wt.% loading) and titania (CuOx-TiO2). Our study was focused on revealing the role of Cu, and the interaction between Cu and TiO2, by systematic comparison between two nanocatalysts, CuOx-TiO2 and pure CuOx. We interrogated these catalysts under in situ conditions using X-ray diffraction (XRD), X-ray absorption fine structure (XAFS) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) to probe the structure and electronic properties of the catalyst at all stages of the reaction and simultaneously probe the surface states or intermediates of this reaction. With the aid of several ex situ characterization techniques including transmission electron microscopy (TEM), the local catalyst morphology and structure were also studied. Our results show that a CuOx-TiO2 system is more active than bulk CuOx for the CO oxidation reaction due to its lower onset temperature and better stability at higher temperatures. Our results also suggest that surface Cu+ species observed in the CuOx-TiO2 interface are likely to be a key player in the CO oxidation mechanism, while implicating that the stabilization of this species is probably associated with the oxide-oxide interface. Both in situ DRIFTS and XAFS measurements reveal that there is likely to be a Cu(Ti)-O mixed oxide at this interface. We discuss the nature of this Cu(Ti)-O interface and interpret its role on the CO oxidation reaction.

  7. Effect of Pr doping on the superconductivity and interlayer coupling of the Bi{sub 2}Sr{sub 2-x}Pr{sub x}Ca{sub 1}Cu{sub 2}O{sub y} system

    Energy Technology Data Exchange (ETDEWEB)

    Salamati, H [Department of Physics, Isfahan University of Technology, Isfahan 84154 (Iran, Islamic Republic of); Kameli, P [Department of Physics, Isfahan University of Technology, Isfahan 84154 (Iran, Islamic Republic of); Razavi, F S [Department of Physics, Brock University, St Catharines, ON L2S 3A1 (Canada)

    2003-08-01

    We investigate the effect of Pr substitution on the superconductivity and interlayer coupling of the Bi{sub 2}Sr{sub 2}Ca{sub 1}Cu{sub 2}O{sub y} system. Magnetic and transport measurements were performed for the purposes of characterization. The superconducting transition temperature T{sub c} first increases and then decreases until it becomes zero at x = 0.6. The effective superconducting volume also decreases due to Pr substitution. From the fluctuation conductivity analysis, it is found that the interlayer coupling constant J decreases monotonically with the increase of the Pr content. This result shows that the Pr doping weakens the CuO{sub 2} interlayer coupling of the Bi2212 system due to the loss of local superconductivity in the CuO{sub 2} layers.

  8. Superconductivity of reduction-treated ceramic material of Pr{sub 2}Ba{sub 4}Cu{sub 7}O{sub 15-{delta}} mixed with the related structure phases

    Energy Technology Data Exchange (ETDEWEB)

    Hagiwara, M. [Department Comprehensive Sciences, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto 606-8585 (Japan)], E-mail: hag@kit.ac.jp; Tanaka, S.; Shima, T.; Gotoh, K. [Department Comprehensive Sciences, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto 606-8585 (Japan); Kanda, S.; Saito, T.; Koyama, K. [University of Tokushima, Tokushima 770-8502 (Japan)

    2008-09-15

    Superconductivity caused by oxygen reduction treatment for sintered Pr{sub 2}Ba{sub 4}Cu{sub 7}O{sub 15-{delta}} (Pr247) synthesized using citrate pyrolysis precursor method is examined experimentally. The sintered sample tends to be heterogeneous structure including Pr124 phase and stacking fault structure rich in CuO single chains. In this work, such a heterogeneous sample and nearly pure phase one were prepared, and the electric conductive behaviors were examined comparatively for various reduction grade sample series. In enough reduced stages, superconductivity with onset temperature 25-28 K was observed for both heterogeneous and purer samples. At transition process by the reduction, superconductivity of the heterogeneous samples can arise from lower oxygen-reduction% than purer Pr247 material. The results may possibly suggest superconductivity by CuO double chains besides Pr247 crystal in our heterogeneous ceramic system.

  9. Superconducting order parameter fluctuations above Tc in polycrystalline Ho 1Ba 2Cu 3O 7-δ compounds

    Science.gov (United States)

    Vidal, Félix; Veira, J. A.; Maza, J.; Ponte, J. J.; Amador, J.; Cascales, C.; Casais, M. T.; Rasines, I.

    1988-08-01

    We report measurements of the excess electrical conductivity, Δσ, above Tc in polycrystalline HoBa 2Cu 3O 7-δ single-phase 0 (within 4%) compounds. The relative temperature resolution is of the order of 10 -2 K which, in spite of the broadening of the transition by nonintrinsic effects, should probably make accessible the whole mean-field regime for Δσ and also to penetrate inside the full critical dynamic region. The general behavior of Δσ(ɛ) in these Ho-based samples is very similar to that previously observed in our laboratory for Y-based high-temperature superconductors. In particular, when analyzed in terms of the Aslamazov-Larkin theory and by using some dynamic scaling ideas, the Δσ(ɛ) data are compatible with a superconducting order parameter of two components fluctuating in three dimensions. No influence of the magnetic Ho ions on Δσ is observed in the whole reduced-temperature range studied.

  10. Extending Universal Nodal Excitations Optimizes Superconductivity in Bi2Sr2CaCu2O8+delta

    Energy Technology Data Exchange (ETDEWEB)

    Gu, G.; Pushp, A.; Parker, C.V.; Pasupathy, A.N.; Gomes, K.K.; Ono, S.; Wen, J.; Xu, Z.; Yazdani, A.

    2009-06-26

    Understanding the mechanism by which d wave superconductivity in the cuprates emerges and is optimized by doping the Mott insulator is one of the major outstanding problems in condensed-matter physics. Our high-resolution scanning tunneling microscopy measurements of the high-transition temperature (T{sub c}) superconductor Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}} show that samples with different T{sub c} values in the low doping regime follow a remarkably universal d wave low-energy excitation spectrum, indicating a doping-independent nodal gap. We demonstrate that T{sub c} instead correlates with the fraction of the Fermi surface over which the samples exhibit the universal spectrum. Optimal T{sub c} is achieved when all parts of the Fermi surface follow this universal behavior. Increasing the temperature above T{sub c} turns the universal spectrum into an arc of gapless excitations, whereas overdoping breaks down the universal nodal behavior.

  11. Cu(II)-catalyzed transformation of benzylpenicillin revisited: the overlooked oxidation.

    Science.gov (United States)

    Chen, Jiabin; Sun, Peizhe; Zhou, Xuefei; Zhang, Yalei; Huang, Ching-Hua

    2015-04-07

    Penicillins, a class of widely used β-lactam antibiotics, are known to be susceptible to catalyzed hydrolysis by metal ions such as Cu(II). However, new results in this study strongly indicate that the role of Cu(II) is not merely a hydrolysis catalyst but also an oxidant. When benzylpenicillin (i.e., penicillin G (PG)) was exposed to Cu(II) ion at an equal molar ratio and pH 7, degradation of PG occurred rapidly in the oxygen-rich solution but gradually slowed down to a halt in the oxygen-limited solution. In-depth studies revealed that Cu(II) catalyzed hydrolysis of PG to benzylpenicilloic acid (PA) and oxidized PA to yield phenylacetamide and other products. The availability of oxygen played the role in reoxidizing Cu(I) back to Cu(II), which sustained fast degradation of PG over time. The overall reaction was also influenced by pH, with Cu(II)-catalyzed hydrolysis of PG occurring throughout pH 5, 7 and 9, while Cu(II) oxidation of PA occurring at pH 7 and 9. Note that the potential of Cu(II) to oxidize penicillins was largely overlooked in the previous literature, and catalyzed hydrolysis was frequently assumed as the only reaction. This study is among the first to identify the dual roles of Cu(II) in the entire degradation process of PG and systematically investigate the overlooked oxidation reaction to elucidate the mechanism. The new mechanistic knowledge has important implications for many other β-lactam antibiotics for their interactions with Cu(II), and significantly improves the ability to predict the environmental fate and transformation products of PG and related penicillins in systems where Cu(II) species are also present.

  12. Nb/NiCu bilayers in single and stacked superconductive tunnel junctions: preliminary results

    Science.gov (United States)

    Pepe, G. P.; Ruotolo, A.; Parlato, L.; Peluso, G.; Ausanio, G.; Carapella, G.; Latempa, R.

    2004-05-01

    We present preliminary experimental results concerning both single and stacked tunnel junctions in which one of the electrodes was formed by a superconductor/ferromagnet (S/F) bi-layer. In particular, in the stacked configuration a Nb/NiCu bi-layer was used as the intermediate electrode, and it was probed by tunneling on both sides. Tunnel junctions have been characterized in terms of current-voltage characteristics (IVC), and differential conductance. Preliminary steady-state injection-detection measurements performed in the stacked devices at T=4.2K are also presented and discussed.

  13. Nb/NiCu bilayers in single and stacked superconductive tunnel junctions: preliminary results

    Energy Technology Data Exchange (ETDEWEB)

    Pepe, G.P. E-mail: ruotolo_antonio@tin.it; Ruotolo, A.; Parlato, L.; Peluso, G.; Ausanio, G.; Carapella, G.; Latempa, R

    2004-05-01

    We present preliminary experimental results concerning both single and stacked tunnel junctions in which one of the electrodes was formed by a superconductor/ferromagnet (S/F) bi-layer. In particular, in the stacked configuration a Nb/NiCu bi-layer was used as the intermediate electrode, and it was probed by tunneling on both sides. Tunnel junctions have been characterized in terms of current-voltage characteristics (IVC), and differential conductance. Preliminary steady-state injection-detection measurements performed in the stacked devices at T=4.2 K are also presented and discussed.

  14. Pd-Cu/poly(o-Anisidine) nanocomposite as an efficient catalyst for formaldehyde oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Hosseini, Sayed Reza, E-mail: r.hosseini@umz.ac.ir [Nanochemistry Research Laboratory, Faculty of Chemistry, University of Mazandaran, 47416-95447 Babolsar (Iran, Islamic Republic of); Raoof, Jahan-Bakhsh [Department of Analytical Chemistry, Faculty of Chemistry, University of Mazandaran, 47416-95447 Babolsar (Iran, Islamic Republic of); Ghasemi, Shahram; Gholami, Zahra [Nanochemistry Research Laboratory, Faculty of Chemistry, University of Mazandaran, 47416-95447 Babolsar (Iran, Islamic Republic of)

    2016-08-15

    Highlights: • o-Anisidine monomer was electro-polymerized at the pCPE surface in acid medium. • Palladium/copper NPs were prepared by galvanic replacement method at the POA/pCPE. • Pd-Cu NPs showed excellent electrocatalytic activity towards formaldehyde oxidation. • The bimetallic Pd-Cu NPs/POA nanocomposite showed satisfactory long-term stability. - Abstract: In this work, for the first time, the electrocatalytic oxidation of formaldehyde in 0.5 M sulfuric acid solution at spherical bimetallic palladium-copper nanoparticles (Pd-Cu NPs) deposited on the poly (o-Anisidine) film modified electrochemically pretreated carbon paste electrode (POA/pCPE) has been investigated. Highly porous POA film prepared by electropolymerization onto the pCPE was used as a potent support for deposition of the Pd-Cu NPs. The Pd-Cu NPs were prepared through spontaneous and irreversible reaction via galvanic replacement between Pd{sup II} ions and the Cu{sup 0} particles. The prepared Pd-Cu NPs were characterized by scanning electron microscopy, energy dispersive spectroscopy and electrochemical methods. The obtained results showed that the utilization of Cu nanoparticles and pretreatment technique enhances the electrocatalytic activity of the modified electrode towards formaldehyde oxidation. The influence of several parameters on formaldehyde oxidation as well as stability of the Pd-Cu/POA/pCPE has been investigated.

  15. Structure-activity relationship of CuO/MnO2 catalysts in CO oxidation

    Science.gov (United States)

    Qian, Kun; Qian, Zhaoxia; Hua, Qing; Jiang, Zhiquan; Huang, Weixin

    2013-05-01

    A series of CuO/MnO2 catalysts with different CuO loadings were synthesized by the incipient wetness impregnation method. The catalysts were characterized by N2 adsorption-desorption isotherms, powder X-ray diffraction, X-ray photoelectron spectroscopy, H2-temperature programmed reduction, CO-temperature programmed reduction and scanning electron microscope. The CuO/MnO2 catalysts with CuO loading of 1-40% exhibit almost the same catalytic performance toward CO oxidation while those with higher CuO loadings exhibit a much poorer catalytic activity. The structural characterization results demonstrate that the CuO-MnO2 interface is the active site for CO oxidation in CuO/MnO2 catalysts and CO oxidation over CuO/MnO2 probably follows the interfacial reaction mechanism in which CO chemisorbed on CuO reacts with oxygen species on MnO2 at the CuO-MnO2 interface.

  16. Superconducting magnetic separation of phosphate using freshly formed hydrous ferric oxide sols.

    Science.gov (United States)

    Li, Yiran; Li, Zhiyong; Xu, Fengyu; Zhang, Weimin

    2017-02-01

    Paramagnetic materials, such as ferric hydroxides, which are cost-effective and highly-efficient, have been little studied in relation to the magnetic separation process. In this study, freshly formed hydrous ferric oxide (HFO) sols were used to remove aqueous phosphate, followed by superconducting magnetic separation. The magnetization of HFO was determined to be 5.7 emu/g in 5.0 T. The particle size distributions ranged from 1 to 80 μm. Ferrihydrite was the primary mineral phase according to XRD analysis. Dissolved P (DP) was first adsorbed on HFO, and second, the P-containing HFO were separated by high gradient superconducting magnetic separation (HGSMS) to remove the Total P (TP). To obtain a P concentration of <0.05 mg/l in the effluent, 0.3, 1.0 and 1.3 g/l HFO were added to 2.5, 5 and 10 mg/l P solutions. The capacity of the HGSMS canister for capturing P-adsorbed HFO depends on the magnetic intensity and flow rate. In the 5.0 T HGSMS at a 1.0 cm/s flow rate, there were 75 column volumes in a single HGSMS cycle. The P concentration increased by 37.5 times after regeneration. Approximately 170 mg/l TP was measured in the backwash water.

  17. Tailoring the morphology of Pt3Cu1 nanocrystals supported on graphene nanoplates for ethanol oxidation

    Science.gov (United States)

    Zhang, Genlei; Yang, Zhenzhen; Zhang, Wen; Hu, Hongwei; Wang, Chunzhen; Huang, Chengde; Wang, Yuxin

    2016-01-01

    In the search for alternatives to conventional Pt electrocatalysts, we synthesized a series of graphene nanoplate (GNP)-supported Pt3Cu1 nanocrystals (NCs), possessing almost the same composition but different morphologies to probe their electrochemical properties as a function of morphology for the ethanol oxidation reaction. The morphology of the Pt3Cu1 catalysts could be systematically evolved from dendritic (D-Pt3Cu1/GNPs) to wire-like (W-Pt3Cu1/GNPs) and spherical (Pt3Cu1/GNPs) by only varying pH of the reaction solution. The as-prepared Pt3Cu1 catalysts were subsequently characterized using a suite of techniques including transmission electron microscopy (TEM), selected area electron diffraction (SAED), X-ray diffraction (XRD), inductively coupled plasma mass spectrometry (ICP-MS) and X-ray photoelectron spectroscopy (XPS) to verify not only their morphologies and chemical compositions but also the incorporation of Cu into the Pt lattice, as well as physical structure and integrity. Gratifyingly, the three Pt3Cu1 catalysts exhibited superior electrocatalytic properties for the ethanol oxidation compared to the monometallic Pt/GNPs and Pt/C-JM (Johnson Matthey), with the activities, durabilities and anti-poisonous abilities following the order Pt3Cu1/GNPs chemical compositions but also the incorporation of Cu into the Pt lattice, as well as physical structure and integrity. Gratifyingly, the three Pt3Cu1 catalysts exhibited superior electrocatalytic properties for the ethanol oxidation compared to the monometallic Pt/GNPs and Pt/C-JM (Johnson Matthey), with the activities, durabilities and anti-poisonous abilities following the order Pt3Cu1/GNPs < W-Pt3Cu1/GNPs < D-Pt3Cu1/GNPs. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr08013d

  18. Kinetic Equation for Internal Oxidation of Cu-Al Alloy Spheres

    Institute of Scientific and Technical Information of China (English)

    SONG Kexing; GAO Jianxin; XU Xiaofeng; LI Peiquan; TIAN Baohong; GUO Xiuhua

    2007-01-01

    The kinetics of internal oxidation of Cu-Al alloy spheres, containing up to 2.214% mole fraction Al was investigated in the temperature range 1 023 K to 1 273 K, and the depth of internal oxidation was measured in the microscopy. A kinetic equation was derived to describe the internal oxidation of Cu-Al alloy spheres, which was checked experimentally by means of oxidation depth measurements. The results show that the derived equation is exact enough to describe the kinetics of internal oxidation of Cu-Al alloy spheres.Based on this equation and the oxidation depth measurements, the permeability of oxygen in solid copper has been obtained. Investigation also shows that in the process of internal oxidation, there is no evidence for preferential diffusion along grain boundaries.

  19. Thermal desorption studies of isotopically-labeled oxygen-induced superconductivity in La sub 2 CuO sub 4+. delta

    Energy Technology Data Exchange (ETDEWEB)

    Shinn, N.D.; Bartram, M.E.; Schirber, J.E.; Overmyer, D.L.; Rogers, J.W. Jr. (Sandia National Labs., Albuquerque, NM (USA)); Fisk, Z.; Cheong, S.W. (Los Alamos National Lab., NM (USA))

    1990-01-01

    Isotopically-labeled oxygen enrichment and thermal desorption mass spectroscopy (TDMS) have been combined to study interstitial oxygen desorption from superconducting La{sub 2}CuO{sub 4+{delta}} ({delta} {le} 0.032). Single crystal samples of magnetic insulating La{sub 2}CuO{sub 4.00} were annealed at 860K under 1--3 kbar oxygen pressure for 12--100 hours to yield hole-doped, superconducting La{sub 2}CuO{sub 4+{delta}} samples with 35K < {Tc} < 40K. Whereas no TDMS signals were observed for the insulator, rapid bursts (FWHM < 0.5 sec) of molecular oxygen were observed above 350K while heating the superconductor at less than 1 K sec{sup {minus}1} in high vacuum. A kinetic model is proposed in which the interstitial oxygen diffuses to internal grain boundaries and defects during heating, thereby inducing stress in the lattice as it attempts to revert to the LaCuO{sub 4.00} crystal structure. This stress is relieved by lattice fracture at grain boundaries during the TDMS experiment, releasing the trapped oxygen from the sample as micro-cracks are formed. In addition, the facile oxygen exchange between interstitial and lattice oxygen sites has been discovered by TDMS and weight gain measurements from isotopically-enriched crystals, supporting the structural model of Chaillout, et al. in which the interstitial oxygen atom dimerizes with a lattice oxygen ion.

  20. The Debye temperature of YBa sub 2 Cu sub 3 O sub 7-. delta. and its dependence on the volume fraction of superconductivity

    Energy Technology Data Exchange (ETDEWEB)

    Fisher, R.A.; Phillips, N.E. (Lawrence Berkeley Lab., CA (United States)); Gordon, J.E. (Lawrence Berkeley Lab., CA (United States) Amherst Coll., MA (United States). Dept. of Physics)

    1991-12-01

    Specific-heat measurements, on polycrystalline samples of YBa{sub 2}Cu{sub 3}O{sub 7-{delta}}, YBCO, have shown sample-to-sample variations in the volume fraction of superconductivity, f{sub s}, which is correlated with the concentration of Cu{sup 2+} magnetic moments in the YBCO lattice. At low temperatures the lattice specific heat also varies with f{sub s}, but these variations do not persist above {approximately}20K. The low-temperature data show that {Theta}{sub 0}{sup {minus}3} varies linearly with f{sub 3}, and give values of 520 and 390K for {Theta}{sub o} for fully-superconducting and fully-normal'' YBCO, respectively. These results suggest that the long wavelength phonon modes are altered when Cu{sup 2+} magnetic moments are present in the lattice. The fact that different samples have the same lattice specific heat at {approximately}20K and above T{sub c} indicates that the higher energy phonon modes are insensitive to these Cu{sup 2+} moments.

  1. The Debye temperature of YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} and its dependence on the volume fraction of superconductivity

    Energy Technology Data Exchange (ETDEWEB)

    Fisher, R.A.; Phillips, N.E. [Lawrence Berkeley Lab., CA (United States); Gordon, J.E. [Lawrence Berkeley Lab., CA (United States)]|[Amherst Coll., MA (United States). Dept. of Physics

    1991-12-01

    Specific-heat measurements, on polycrystalline samples of YBa{sub 2}Cu{sub 3}O{sub 7-{delta}}, YBCO, have shown sample-to-sample variations in the volume fraction of superconductivity, f{sub s}, which is correlated with the concentration of Cu{sup 2+} magnetic moments in the YBCO lattice. At low temperatures the lattice specific heat also varies with f{sub s}, but these variations do not persist above {approximately}20K. The low-temperature data show that {Theta}{sub 0}{sup {minus}3} varies linearly with f{sub 3}, and give values of 520 and 390K for {Theta}{sub o} for fully-superconducting and ``fully-normal`` YBCO, respectively. These results suggest that the long wavelength phonon modes are altered when Cu{sup 2+} magnetic moments are present in the lattice. The fact that different samples have the same lattice specific heat at {approximately}20K and above T{sub c} indicates that the higher energy phonon modes are insensitive to these Cu{sup 2+} moments.

  2. on THICKNESS OF COPPER (|) OXIDE (Cu2"O) SOLAR CELL

    African Journals Online (AJOL)

    thickness of copper oxides solar ce[[s prepared 63/ thermaf oxidation method The sampfes were oxidized at di_';§'erent oxidation temperatures and time. The diflerent oxidation ... observed that the later was relatively high. Adrianus (1978).

  3. Electrochemical fluorination of La(2)CuO(4): a mild "chimie douce" route to superconducting oxyfluoride materials.

    Science.gov (United States)

    Delville, M H; Barbut, D; Wattiaux, A; Bassat, J M; Ménétrier, M; Labrugère, C; Grenier, J C; Etourneau, J

    2009-08-17

    The fluorination of La(2)CuO(4) was achieved for the first time under normal conditions of pressure and temperature (1 MPa and 298 K) via electrochemical insertion in organic fluorinated electrolytes and led to lanthanum oxyfluorides of general formula La(2)CuO(4)F(x). Analyses showed that, underneath a very thin layer of LaF(3) (a few atomic layers), fluorine is effectively inserted in the material's structure. The fluorination strongly modifies the lanthanum environment, whereas very little modification is observed on copper, suggesting an insertion in the La(2)O(2) blocks of the structure. In all cases, fluorine insertion breaks the translation symmetry and introduces a long-distance disorder, as shown by electron spin resonance. These results highlight the efficiency of electrochemistry as a new "chimie douce" type fluorination technique for solid-state materials. Performed at room temperature, it additionally does not require any specific experimental care. The choice of the electrolytic medium is crucial with regard to the fluorine insertion rate as well as the material deterioration. Successful application of this technique to the well-known La(2)CuO(4) material provides a basis for further syntheses from other oxides.

  4. Long term high temperature oxidation characteristics of La and Cu alloyed ferritic stainless steels for solid oxide fuel cell interconnects

    Science.gov (United States)

    Swaminathan, Srinivasan; Lee, Young-Su; Kim, Dong-Ik

    2016-09-01

    To ensure the best performance of solid oxide fuel cell metallic interconnects, the Fe-22 wt.% Cr ferritic stainless steels with various La contents (0.006-0.6 wt.%) and Cu addition (1.57 wt.%), are developed. Long-term isothermal oxidation behavior of these steels is investigated in air at 800 °C, for 2700 h. Chemistry, morphology, and microstructure of the thermally grown oxide scale are examined using XPS, SEM-EDX, and XRD techniques. Broadly, all the steels show a double layer consisting of an inner Cr2O3 and outer (Mn, Cr)3O4. Distinctly, in the La-added steels, binary oxides of Cr, Mn and Ti are found at the oxide scale surface together with (Mn, Cr)3O4. Furthermore, all La-varied steels possess the metallic Fe protrusions along with discontinuous (Mn, Cr)3O4 spinel zones at the oxide scale/metal interface and isolated precipitates of Ti-oxides in the underlying matrix. Increase of La content to 0.6 wt.% is detrimental to the oxidation resistance. For the Cu-added steel, Cu is found to segregate strongly at the oxide scale/metal interface which inhibits the ingress of oxygen thereby suppressing the subscale formation of (Mn, Cr)3O4. Thus, Cu addition to the Fe-22Cr ferritic stainless steels benefits the oxidation resistance.

  5. Dynamic Behavior of CuZn Nanoparticles under Oxidizing and Reducing Conditions

    DEFF Research Database (Denmark)

    Holse, Christian; Elkjær, Christian Fink; Nierhoff, Anders Ulrik Fregerslev;

    2015-01-01

    The oxidation and reduction of CuZn nanoparticles was studied using X-ray photoelectron spectroscopy (XPS) and in situ transmission electron microscopy (TEM). CuZn nanoparticles with a narrow size distribution were produced with a gas-aggregation cluster source in conjunction with mass......-filtration. A direct comparison between the spatially averaged XPS information and the local TEM observations was thus made possible. Upon oxidation in O2, the as-deposited metal clusters transform into a polycrystalline cluster consisting of separate CuO and ZnO nanocrystals. Specifically, the CuO is observed...... to segregate to the cluster surface and partially cover the ZnO nanocrystals. Upon subsequent reduction in H2 the CuO converts into metallic Cu with ZnO nanocrystal covering their surface. In addition, a small amount of metallic Zn is detected suggesting that ZnO is reduced. It is likely that Zn species can...

  6. One-Pot Synthesis of Cu(II Complex with Partially Oxidized TTF Moieties

    Directory of Open Access Journals (Sweden)

    Hiroki Oshio

    2012-07-01

    Full Text Available The one-pot synthesis of a Cu(II complex with partially oxidized tetrathiafulvalene (TTF moieties in its capping MT-Hsae-TTF ligands, [CuII(MT-sae-TTF2] [CuICl2] was realized by the simultaneous occurrence of Cu(II complexation and CuIICl2 mediated oxidation of TTF moieties. The crystal structure was composed of one-dimensional columns formed by partially oxidized TTF moieties and thus the cation radical salt showed relatively high electrical conductivity. Tight binding band structure calculations indicated the existence of a Peierls gap due to the tetramerization of the TTF moieties in the one-dimensional stacking column at room temperature, which is consistent with the semiconducting behavior of this salt.

  7. Ultrasonic evaluation of oxygen content, modulus, and microstructure changes in YBa2Cu3O(7-x) occurring during oxidation and reduction

    Science.gov (United States)

    Roth, Don J.; Deguire, Mark R.; Dolhert, Leonard E.

    1992-01-01

    Ultrasonic velocity measurement techniques were used to evaluate the effects of oxidation and reduction on the elastic properties, global microstructure and oxygen content of the YBa2Cu3O(7-x) ceramic superconductor for samples ranging from 70 to 90 pct of theoretical density. Bulk density, velocity, and elastic modulus generally increased with increasing oxygen content upon oxidation, and this behavior was reversible. Velocity image patterns were similar after oxidation and reduction treatments for a 90 pct. dense sample, although the velocity value at any given point on the sample was changed following the treatments. The unchanging pattern correlated with destructive measurements showing that the spatial pore distribution (fraction and size) was not measurably altered after the treatments. Changes in superconducting behavior, crystal structure, and grain structure were observed consistent with changes in oxygen content.

  8. Ultrasonic evaluation of oxidation and reduction effects on the elastic behavior and global microstructure of YBa2Cu3O7-x

    Science.gov (United States)

    Roth, Don J.; Deguire, Mark R.; Dolhert, Leonard E.

    1991-01-01

    Ultrasonic velocity measurement techniques were used to evaluate the effects of oxidation and reduction on the elastic properties, global microstructure and oxygen content of the YBa2Cu3O(7-x) ceramic superconductor for samples ranging from 70 to 90 pct. of theoretical density. Bulk density, velocity, and elastic modulus generally increased with increasing oxygen content upon oxidation, and this behavior was reversible. Velocity image patterns were similar after oxidation and reduction treatments for a 90 pct. dense sample, although the velocity value at any given point on the sample was changed following the treatments. The unchanging pattern correlated with destructive measurements showing that the spatial pore distribution (fraction and size) was not measurably altered after the treatments. Changes in superconducting behavior, crystal structure, and grain structure were observed consistent with changes in oxygen content.

  9. Measurements and analysis of Hall effect of a two dimensional electron gas in the close proximity of a superconducting YBa2Cu3O(7 - x) film

    Science.gov (United States)

    Tseng, M. Z.; Jiang, W. N.; Hu, E. L.

    1994-09-01

    A direct integration of YBa2Cu3O(7 - x) and a two dimensional electron gas Hall probe was made possible through the use of a MgO buffer layer. We demonstrate the use of this structure for the measurements of the magnetization hysteresis of a superconducting YBa2Cu3O(7 - x) thin film, and we make an estimate of the sensitivity and resolution that can be achieved with this probe structure. The close proximity of the YBa2Cu3O(7 - x) to the two dimensional electron gas (approximately 1700 A) allows sensitive measurements of interactions between the two; more importantly, closer superconductor-semiconductor spacing can be achieved without severe compromise of the component material quality.

  10. Superconductivity and structural characteristics of ceramic Pr{sub 2}Ba{sub 4}Cu{sub 7}O{sub 15-{delta}} prepared by ambient pressure synthesis using citrate pyrolysis method

    Energy Technology Data Exchange (ETDEWEB)

    Hagiwara, M. [Department of Comprehensive Sciences, Kyoto Institute of Technology, Sakyo-ku, Kyoto 606-8585 (Japan)], E-mail: hag@kit.ac.jp; Shima, T.; Tanaka, S.; Nishio, K.; Isshiki, T. [Department of Comprehensive Sciences, Kyoto Institute of Technology, Sakyo-ku, Kyoto 606-8585 (Japan); Saito, T.; Koyama, K. [University of Tokushima, Tokushima 770-8502 (Japan)

    2007-10-01

    Sintered material of Pr{sub 2}Ba{sub 4}Cu{sub 7}O{sub 15-{delta}} (Pr247) was synthesized at ambient pressure condition by using citrate pyrolysis precursor method, and the superconductivity caused by oxygen reduction treatment has been confirmingly observed and examined. By resistivity and magnetization experiments, it has been found that the critical temperature T{sub c} of the reduced samples could reach about 10 K higher than previously reported data for pure Pr247. Besides, from TEM observations, the present material was found to be heterogeneous system containing Pr247, Pr124 and novel stacking structure phases rich in CuO single chains. These results have suggested that oxygen-reduction at such region rich in the CuO single chains may affect the superconductivity of the adjacent crystal region containing CuO double chains, and might enhance the superconductive critical temperature.

  11. Alkaline vapor oxidation synthesis and electrocatalytic activity toward glucose oxidation of CuO/ZnO composite nanoarrays

    Science.gov (United States)

    Soejima, Tetsuro; Takada, Kohei; Ito, Seishiro

    2013-07-01

    CuO/ZnO nanocomposite materials have attracted widespread attention because of their scientific and technological importance as, for example, photocatalysts, gas and humidity sensors, catalysts for H2 production and organic synthesis, and solar cells. High-temperature and/or complicated multistep processes are usually used to prepare these composites. Here we demonstrate a low-temperature and facile one-step synthesis of CuO nanoflowers/ZnO nanorods composite arrays via an alkaline vapor oxidation process. The CuO/ZnO composite nanoarrays show high electrocatalytic activity toward glucose oxidation.

  12. Deposition of superconducting YBaCuO thin films by pseudospark ablation

    Energy Technology Data Exchange (ETDEWEB)

    Hoebel, M.; Geerk, J.; Linker, G.; Schultheiss, C. (Kernforschungszentrum Karlsruhe, Institut fuer Nukleare Festkoerperphysik (INFP), P.O. Box 3640, D-7500 Karlsruhe, Federal Republic of Germany (DE))

    1990-03-05

    Thin YBaCuO films have been deposited on ZrO{sub 2}(Y) and SrTiO{sub 3} substrates by a novel ablation method, using a pulsed intense electron beam generated by a pseudospark source. Films with zero resistance around 85 K were grown at substrate temperatures of 820 {degree}C with high reproducibility. X-ray analysis indicates highly textured growth on both substrates. {ital J}{sub {ital c}} values were 6{times}10{sup 6} A/cm{sup 2} at 4.2 K and 1.1{times}10{sup 5} A/cm{sup 2} at 77 K. Because of the high simplicity of the deposition system and the variety of changeable parameters it represents an interesting alternative to existing laser ablation methods.

  13. Enhanced wet hydrogen peroxide catalytic oxidation performances based on CuS nanocrystals/reduced graphene oxide composites

    Science.gov (United States)

    Qian, Jing; Wang, Kun; Guan, Qingmeng; Li, Henan; Xu, Hui; Liu, Qian; Liu, Wei; Qiu, Baijing

    2014-01-01

    CuS nanocrystals/reduced graphene oxide (CuS NCs/rGO) composites were prepared by a facile one-pot solvothermal reaction. In this solvothermal system, thioacetamide was found to perform the dual roles of sulphide source and reducing agent, resulting in the formation of CuS NCs and simultaneous reduction of graphene oxide (GO) sheets to rGO sheets. In addition, CuS NCs/rGO composites were further used as heterogeneous catalysts in the wet hydrogen peroxide catalytic oxidation process, with methylene blue as a model organic dye. The introduction of rGO to CuS NCs could effectively enhance the catalytic activity of CuS NCs, and the resultant CuS NCs/rGO composites with a starting GO amount of 5 wt% showed the highest catalytic activity. Furthermore, the CuS NCs/rGO composites showed high catalytic activity over a broad pH operation range from 3.0 to 11.0 under ambient conditions, and still retained 90% of the original catalytic activity after reuse in five cycles.

  14. Large transport Jc in Cu-sheathed Sr0.6K0.4Fe2As2 superconducting tape conductors

    Science.gov (United States)

    Lin, He; Yao, Chao; Zhang, Haitao; Zhang, Xianping; Zhang, Qianjun; Dong, Chiheng; Wang, Dongliang; Ma, Yanwei

    2015-01-01

    Copper sheath is the first choice for manufacturing high-Tc superconducting wires and tapes because of its high electrical and thermal conductivities, low-cost and good mechanical properties. However, Cu can easily react with superconducting cores, such as BSCCO, MgB2 and pnictides, and therefore drastically decrease the transport Jc. Here, we report the fabrication of Cu-sheathed Sr1−xKxFe2As2 tapes with superior Jc performance using a simple hot pressing method that is capable of eliminating the lengthy high-temperature sintering. We obtained high-quality Sr1−xKxFe2As2 tapes with processing at 800 oC for 30 minutes and measured high Tc and sharp transition. By this rapid fabrication, Cu sheath does not give rise to apparent reaction layer, and only slightly diffuses into Sr-122 core. As a consequence, we achieved high transport Jc of 3.1 × 104 A/cm2 in 10 T and 2.7 × 104 A/cm2 in 14 T at 4.2 K. The in-field Jc performance is by far the highest reported for Cu-sheathed high-Tc conductors. More importantly, Cu-sheathed Sr-122 tapes also showed a high Je value of 1.0 × 104 A/cm2 in 10 T at 4.2 K, which has reached the widely accepted practical level for applications. These results demonstrate that Cu is a very promising sheath for the practical application of pnictide conductors. PMID:26122741

  15. Smooth surfaces in very thin GdBa{sub 2}Cu{sub 3}O{sub 7−δ} films for application in superconducting tunnel junctions

    Energy Technology Data Exchange (ETDEWEB)

    Navarro, H., E-mail: henrynavarro@cab.cnea.gov.ar [Instituto Balseiro, Universidad Nacional de Cuyo & CNEA, 8400 Bariloche (Argentina); Centro Atómico Bariloche, Comisión Nacional de Energía Atómica. Av. Bustillo 9500, 8400 San Carlos de Bariloche (Argentina); Sirena, M. [Instituto Balseiro, Universidad Nacional de Cuyo & CNEA, 8400 Bariloche (Argentina); Centro Atómico Bariloche, Comisión Nacional de Energía Atómica. Av. Bustillo 9500, 8400 San Carlos de Bariloche (Argentina); Kim, Jeehoon [Department of Physics, Pohang University of Science and Technology, Pohang (Korea, Republic of); CALDES, Institute for Basic Science, Pohang (Korea, Republic of); Haberkorn, N. [Instituto Balseiro, Universidad Nacional de Cuyo & CNEA, 8400 Bariloche (Argentina); Centro Atómico Bariloche, Comisión Nacional de Energía Atómica. Av. Bustillo 9500, 8400 San Carlos de Bariloche (Argentina)

    2015-03-15

    Highlights: • A detailed study of the morphological properties of GdBa{sub 2}Cu{sub 3}O{sub 7−δ} thin films was realized. • The inclusion of a very thin SrTiO{sub 3} buffer layer modifies the surface of the SrTiO{sub 3} substrates. • The inclusion of the buffer layer suppress the three dimensional nucleation in the GdBa{sub 2}Cu{sub 3}O{sub 7−δ} film. • GdBa{sub 2}Cu{sub 3}O{sub 7−δ} films with large areas free of topological defects and T{sub c} close to liquid nitrogen can be obtained. - Abstract: This paper provides a systematic analysis of the morphology and the superconducting critical temperature obtained in very thin GdBa{sub 2}Cu{sub 3}O{sub 7−δ} films grown on (0 0 1) SrTiO{sub 3} substrates by DC sputtering. We find that the use of a very thin SrTiO{sub 3} buffer layer (≈2 nm) modify the nucleation of GdBa{sub 2}Cu{sub 3}O{sub 7−δ} on the surface of the substrate reducing the formation of 3 dimensional clusters. Our results demonstrate that 16 nm thick GdBa{sub 2}Cu{sub 3}O{sub 7−δ} films with an average root-mean-square (RMS) smaller than 1 nm and large surface areas (up 10 μm{sup 2}) free of 3 dimensional topological defects can be obtained. In films thinner than 24 nm the onset (zero resistance) of superconducting transition of the films is reduced, being close to liquid nitrogen. This fact can be associated with stress reducing the orthorhombicity and slightly drop in oxygen stoichiometry.

  16. Magnetic-field-induced charge-stripe order in the high-temperature superconductor YBa2Cu3Oy.

    Science.gov (United States)

    Wu, Tao; Mayaffre, Hadrien; Krämer, Steffen; Horvatić, Mladen; Berthier, Claude; Hardy, W N; Liang, Ruixing; Bonn, D A; Julien, Marc-Henri

    2011-09-07

    Electronic charges introduced in copper-oxide (CuO(2)) planes generate high-transition-temperature (T(c)) superconductivity but, under special circumstances, they can also order into filaments called stripes. Whether an underlying tendency towards charge order is present in all copper oxides and whether this has any relationship with superconductivity are, however, two highly controversial issues. To uncover underlying electronic order, magnetic fields strong enough to destabilize superconductivity can be used. Such experiments, including quantum oscillations in YBa(2)Cu(3)O(y) (an extremely clean copper oxide in which charge order has not until now been observed) have suggested that superconductivity competes with spin, rather than charge, order. Here we report nuclear magnetic resonance measurements showing that high magnetic fields actually induce charge order, without spin order, in the CuO(2) planes of YBa(2)Cu(3)O(y). The observed static, unidirectional, modulation of the charge density breaks translational symmetry, thus explaining quantum oscillation results, and we argue that it is most probably the same 4a-periodic modulation as in stripe-ordered copper oxides. That it develops only when superconductivity fades away and near the same 1/8 hole doping as in La(2-x)Ba(x)CuO(4) (ref. 1) suggests that charge order, although visibly pinned by CuO chains in YBa(2)Cu(3)O(y), is an intrinsic propensity of the superconducting planes of high-T(c) copper oxides.

  17. High-Resolution Gamma-Ray Spectrometers using Bulk Absorbers Coupled to Mo/Cu Multilayer Superconducting Transition-Edge Sensors

    Energy Technology Data Exchange (ETDEWEB)

    Chow, D.T.; Loshak, A.; Van Den Berg, M.L.; Frank, M.; Barbee Jr., T.W.; Labov, S.E.

    2000-07-04

    In x-ray and gamma-ray spectroscopy, it is desirable to have detectors with high energy resolution and high absorption efficiency. At LLNL, we have developed superconducting tunnel junction-based single photon x-ray detectors with thin film absorbers that have achieved these goals for photon energies up to 1 keV. However, for energies above 1 keV, the absorption efficiency of these thin-film detectors decreases drastically. We are developing the use of high-purity superconducting bulk materials as microcalorimeter absorbers for high-energy x-rays and gamma rays. The increase in absorber temperature due to incident photons is sensed by a superconducting transition-edge sensor (TES) composed of a Mo/Cu multilayer thin film. Films of Mo and Cu are mutually insoluble and therefore very stable and can be annealed. The multilayer structure allows scaling in thickness to optimize heat capacity and normal state resistance. We measured an energy resolution of 70 eV for 60 keV incident gamma-rays with a 1 x 1 x 0.25 mm{sup 3} Sn absorber. We present x-ray and gamma-ray results from this detector design with a Sn absorber. We also propose the use of an active negative feedback voltage bias to improve the performance of our detector and show preliminary results.

  18. Reassessment of the electronic state, magnetism, and superconductivity in high-Tc cuprates with the Nd2CuO4 structure

    Science.gov (United States)

    Naito, Michio; Krockenberger, Yoshiharu; Ikeda, Ai; Yamamoto, Hideki

    2016-04-01

    The electronic phase diagram of the cuprates remains enigmatic and is still a key ingredient to understand the mechanism of high-Tc superconductivity. It has been believed for a long time that parent compounds of cuprates were universally antiferromagnetic Mott insulators (charge-transfer insulators) and that high-Tc superconductivity would develop upon doping holes or electrons in a Mott-Hubbard insulator ("doped Mott-insulator scenario"). However, our recent discovery of superconductivity in the parent compounds of square-planar cuprates with the Nd2CuO4 (T') structure and the revised electronic phase diagram in T' cuprates urged a serious reassessment to the above scenario. In this review, we present the main results derived from our synthesis and experiments on T' cuprates in the undoped or heavily underdoped regime over 20 years, including material issues and basic physics. The key material issue is how to remove excess oxygen ions at the apical site without introducing oxygen vacancies in the CuO2 planes. In order to put this into practice, the basic knowledge of complex solid-state chemistry in T' cuprates is required, which is also included in this review.

  19. CuInS2 nanotube array on indium tin oxide: synthesis and photoelectrochemical properties.

    Science.gov (United States)

    Wu, Jih-Jen; Jiang, Wan-Ting; Liao, Wen-Pin

    2010-08-28

    CuInS(2) nanotube (NT) arrays were synthesized on indium tin oxide (ITO) substrates for the first time using a successive ionic layer absorption and reaction (SILAR) process with self-dissolved ZnO nanowire (NW) templates. The p-type CuInS(2) NT array shows promising conversion efficiency in a photoelectrochemical cell with polysulfide electrolyte.

  20. Depolymerization of organosolv lignin to aromatic compounds over Cu-doped porous metal oxides

    NARCIS (Netherlands)

    Barta, Katalin; Warner, Genoa R.; Beach, Evan S.; Anastas, Paul T.

    2014-01-01

    Isolated, solvent-extracted lignin from candlenut (Aleurites moluccana) biomass was subjected to catalytic depolymerization in methanol with an added pressure of H-2, using a porous metal oxide catalyst (PMO) derived from a Cu-doped hydrotalcite-like precursor. The Cu-PMO was effective in converting

  1. Depolymerization of organosolv lignin to aromatic compounds over Cu-doped porous metal oxides

    NARCIS (Netherlands)

    Barta, Katalin; Warner, Genoa R.; Beach, Evan S.; Anastas, Paul T.

    2014-01-01

    Isolated, solvent-extracted lignin from candlenut (Aleurites moluccana) biomass was subjected to catalytic depolymerization in methanol with an added pressure of H-2, using a porous metal oxide catalyst (PMO) derived from a Cu-doped hydrotalcite-like precursor. The Cu-PMO was effective in converting

  2. 8 COPPER (I) OXIDE (Cu2O) BASED SOLAR CELLS - A REVIEW

    African Journals Online (AJOL)

    DR. AMINU

    ABSTRACT. Copper (I) oxide (Cu2O) is a potential material for the fabrication of low cost solar cells for ... problems of the above energy sources make the international ..... results of their study on ZnO/Cu2O junction solar cells. The best values ...

  3. The crystal structure of RESrGaCuO sub 5 (RE: La, Pr, Nd), a gallate-cuprate with strong structural similarities to superconducting cuprates

    Energy Technology Data Exchange (ETDEWEB)

    Roth, G.; Adelmann, P.; Massing, S. (INFP, Karlsruhe (Germany)); Knitter, R. (IMF, Karlsruhe (Germany)); Wolf, T. (ITP, Karlsruhe (Germany))

    1992-08-01

    The crystal structure and some basic properties of RESrGaCuO{sub 5}(RE: La, Pr, Nd, space group Ima2, z = 4, a = 16.277(1) {angstrom}, b = 5.5191(3) {angstrom}, c = 5.3342(3) {angstrom} for RE = Nd) has been studied by powder and single-crystal X-ray methods, electrical resistivity and magnetic susceptibility measurements, DSC, TG, and optical microscopy. The structure consists of almost planar nets of distorted corner sharing Cu-O{sub 6} octahedra connected along the longest axis via Ga-O{sub 4} tetrahedral chains with RE and Sr ions filling the large voids between planes and chains. It is isotypic to the structure of the mineral Brownmillerite (Ca{sub 2}(Al,Fe){sub 2}O{sub 5}). Together with its recently described double Cu-O{sub n} layer counterpart RESr{sub 2}GaCu{sub 2}O{sub 7} it forms a homologous series of new gallate-cuprates which closely resemble the corresponding Ga-free superconducting cuprates with single and double Cu-O{sub n} layers. Stoichiometric RESrGaCuO{sub 5} has a fixed oxygen content and is semiconducting with a strong anisotropy of the optical absorption, indicating a pronounced 2-dimensional character of the electronic properties. P-doping of these materials by partial substitution of RE by additional Sr has not been successful up to now.

  4. High-Tc superconductivity in ultrathin Bi2Sr2CaCu2O(8+x) down to half-unit-cell thickness by protection with graphene.

    Science.gov (United States)

    Jiang, Da; Hu, Tao; You, Lixing; Li, Qiao; Li, Ang; Wang, Haomin; Mu, Gang; Chen, Zhiying; Zhang, Haoran; Yu, Guanghui; Zhu, Jie; Sun, Qiujuan; Lin, Chengtian; Xiao, Hong; Xie, Xiaoming; Jiang, Mianheng

    2014-12-08

    High-Tc superconductors confined to two dimension exhibit novel physical phenomena, such as superconductor-insulator transition. In the Bi2Sr2CaCu2O(8+x) (Bi2212) model system, despite extensive studies, the intrinsic superconducting properties at the thinness limit have been difficult to determine. Here, we report a method to fabricate high quality single-crystal Bi2212 films down to half-unit-cell thickness in the form of graphene/Bi2212 van der Waals heterostructure, in which sharp superconducting transitions are observed. The heterostructure also exhibits a nonlinear current-voltage characteristic due to the Dirac nature of the graphene band structure. More interestingly, although the critical temperature remains essentially the same with reduced thickness of Bi2212, the slope of the normal state T-linear resistivity varies by a factor of 4-5, and the sheet resistance increases by three orders of magnitude, indicating a surprising decoupling of the normal state resistance and superconductivity. The developed technique is versatile, applicable to investigate other two-dimensional (2D) superconducting materials.

  5. Crossover between superconductivity and magnetism in SrRuO3 mesocrystal embedded YBa2Cu3O7-x heterostructures.

    Science.gov (United States)

    Suresh, Vandrangi; Lin, Jheng-Cyuan; Liu, Heng-Jui; Zhang, Zaoli; Chiang, Ping-Chih; Hsun, Yu-Ching; Chen, Yi-Chun; Lin, Jiunn-Yuan; Chu, Ying-Hao

    2016-11-03

    The competition between superconductivity and ferromagnetism poses great challenges and has attracted renewed interest for applications in novel spintronic devices. In order to emphasize their interactions, we fabricated a heterostructure composed of superconducting YBa2Cu3O7-δ (YBCO) film embedded with itinerant ferromagnetic SrRuO3 (SRO) mesocrystals. Starting from a doping concentration of 10 vol% of SRO mesocrystal in a YBCO matrix, corresponding to the density of SRO nanocrystals ∼5 × 10(9) cm(-2), which exhibits the typical characteristic of a metal-superconductor transition, and then increasing the magnetic interactions as a function of SRO embedment, the electronic correlation and the interplay between superconductivity and magnetism throughout the temperature regime were investigated. A metal-insulator transition in the normal state of YBCO and a crossover between superconductivity and magnetism at low temperatures were found upon increasing the density of nano-size SRO crystallites in the YBCO matrix as a consequence of competing interactions between these two ordered phases.

  6. CuO/CeO2 Catalysts for Selective Oxidation of Carbon Monoxide in Excess Hydrogen

    Institute of Scientific and Technical Information of China (English)

    刘春涛; 史鹏飞; 张菊香

    2004-01-01

    CuO/CeO2 catalysts were prepared by a coprecipitation method and tested for CO removal from reformed fuels via selective oxidation. The influence of the calcination temperature on the chemical compositions and catalytic performance of CuO/CeO2 catalysts were studied. It was found that CuO/CeO2 catalysts exhibit excellent CO oxidation activity and selectivity,and the complete removal of CO is attained when the catalysts are calcined at appropriate temperatures. XRD, TPR and XPS results indicate that CuO/CeO2 catalysts exhibit higher catalytic performance in CO selective oxidation due to the strong interaction between copper oxide and cerium dioxide, which promotes the dispersion and hydrogen reduction activity of copper.

  7. Hydroxylation of benzene to phenol over magnetic recyclable nanostructured CuFe mixed-oxide catalyst

    CSIR Research Space (South Africa)

    Makgwane, PR

    2015-03-01

    Full Text Available A highly active and magnetically recyclable nanostructured copper–iron oxide (CuFe) catalyst has been synthesized for hydroxylation of benzene to phenol under mild reaction conditions. The obtained catalytic results were correlated with the catalyst...

  8. Fabrication and Optoelectrical Properties of IZO/Cu2O Heterostructure Solar Cells by Thermal Oxidation

    Directory of Open Access Journals (Sweden)

    Cheng-Chiang Chen

    2012-01-01

    Full Text Available Indium zinc oxide (IZO/cupper oxide (Cu2O is a nontoxic nature and an attractive all-oxide candidate for low-cost photovoltaic (PV applications. The present paper reports on the fabrication of IZO/Cu2O heterostructure solar cells which the Cu2O layers were prepared by oxidation of Cu thin films deposited on glass substrate. The measured parameters of cells were the short-circuit current (Isc, the open-circuit voltage (Voc, the maximum output power (Pm, the fill factor (FF, and the efficiency (η, which had values of 0.11 mA, 0.136 V, 5.05 μW, 0.338, and 0.56%, respectively, under AM 1.5 illumination.

  9. Anomalous pressure dependence of the superconducting transition temperature of beta-pyrochlore AOs2O6 oxides.

    Science.gov (United States)

    Muramatsu, T; Takeshita, N; Terakura, C; Takagi, H; Tokura, Y; Yonezawa, S; Muraoka, Y; Hiroi, Z

    2005-10-14

    High-pressure effects on the superconducting transitions of beta-pyrochlore oxide superconductors AOs(2)O(6) (A = Cs,Rb,K) are studied by measuring resistivity under high pressures up to 10 GPa. The superconducting transition temperature T(c) first increases with increasing pressure in every compound 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 GPa and 6 GPa for A = Rb and K and probably above 10 GPa for A = Cs. Characteristic changes in the coefficient A of the T(2) term in resistivity and residual resistivity are observed, both of which are synchronized with the corresponding change in T(c).

  10. Performance of a Y-Ba-Cu-O superconducting filter/GaAs low noise amplifier hybrid circuit

    Science.gov (United States)

    Bhasin, Kul B.; Toncich, S. S.; Chorey, C. M.; Bonetti, R. R.; Williams, A. E.

    1992-01-01

    A superconducting 7.3 GHz two-pole microstrip bandpass filter and a GaAs low noise amplifier (LNA) were combined into a hybrid circuit and characterized at liquid nitrogen temperatures. This superconducting/seismology circuit's performance was compared to a gold filter/GaAs LNA hybrid circuit. The superconducting filter/GaAs LNA hybrid circuit showed higher gain and lower noise figure than its gold counterpart.

  11. Catalytic conversion of methane to methanol on Cu-SSZ-13 using N2O as oxidant.

    Science.gov (United States)

    Ipek, B; Lobo, R F

    2016-11-08

    Direct catalytic methanol production from methane is achieved on Cu-SSZ-13 zeolite catalysts using N2O as the oxidant. The methanol production rate on Cu-SSZ-13 (on a per gram basis) was more than twice the rate on Cu-mordenite and more than four times the rate on Cu-ZSM-5.

  12. Cu and Boron Doped Carbon Nitride for Highly Selective Oxidation of Toluene to Benzaldehyde

    Directory of Open Access Journals (Sweden)

    Hongling Han

    2015-07-01

    Full Text Available A novel Cu and boron doped graphitic carbon nitride catalyst (Cu-CNB was synthesized using cheap precursors and systematically characterized. The selective oxidation of toluene proceeded very smoothly over the catalyst at 70 °C using tert-butyl hydroperoxide (TBHP as the oxidant to exclusively afford benzaldehyde. The catalyst can be used for at least five cycles without decrease in activity and selectivity.

  13. Cu and Boron Doped Carbon Nitride for Highly Selective Oxidation of Toluene to Benzaldehyde.

    Science.gov (United States)

    Han, Hongling; Ding, Guodong; Wu, Tianbin; Yang, Dexin; Jiang, Tao; Han, Buxing

    2015-07-13

    A novel Cu and boron doped graphitic carbon nitride catalyst (Cu-CNB) was synthesized using cheap precursors and systematically characterized. The selective oxidation of toluene proceeded very smoothly over the catalyst at 70 °C using tert-butyl hydroperoxide (TBHP) as the oxidant to exclusively afford benzaldehyde. The catalyst can be used for at least five cycles without decrease in activity and selectivity.

  14. Effects of Ag, Ag{sub 2}O and AgNO{sub 3} addition on the superconducting properties of Tl{sub 2}Ba{sub 2}CaCu{sub 2}O{sub 8}

    Energy Technology Data Exchange (ETDEWEB)

    Salleh, Faizah M.; Yahya, A.K.; Imad, H.; Abd-Shukor, R

    2003-02-25

    The effects of 5 wt.% Ag additions in the form of Ag powder, Ag{sub 2}O and AgNO{sub 3} on phase formation and superconductivity of Tl-2212 is reported. Samples were prepared using two different solid state synthesis routes: (a) addition of 5 wt.% Ag to presynthesized (PS) Tl-2212 powder and (b) premixing (PM) of 5 wt.% Ag to unreacted powders with starting composition of Tl{sub 2}Ba{sub 2}CaCu{sub 2}O{sub 8}. For PS samples, addition of Ag showed little effect on T{sub c} values. For PM samples, addition of Ag in the form of Ag powder and AgNO{sub 3} showed a lowering of T{sub czero} to around 70 K. In the case of Ag{sub 2}O the deterioration is severe and the sample was not superconducting down to 10 K. X-ray diffraction patterns of PM samples showed existence of Tl-2212 phase and a substantial amount of unreacted Tl{sub 2}O{sub 3}. We also report results of microstructural investigations using scanning electron microscope and Vickers Microhardness measurements and their variation with the synthesis methods and the different forms of Ag-additives. The different forms of starting silver give rise to varied Tl-2212 properties and the PS AgNO{sub 3} sample showed the best improvement in normal state conductivity compared to metallic silver and silver oxide powders.

  15. Ba{sub 2}NdZrO{sub 5.5} as a potential substrate material for YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} superconducting films

    Energy Technology Data Exchange (ETDEWEB)

    Tovar, H. [Universidad de la Amazonia, Florencia, Caqueta (Colombia); Grupo de Fisica de Nuevos Materiales, Departamento de Fisica, Universidad Nacional de Colombia, AA 14490, Bogota DC (Colombia); Ortiz Diaz, O.; Landinez Tellez, D.A.; Roa-Rojas, J. [Grupo de Fisica de Nuevos Materiales, Departamento de Fisica, Universidad Nacional de Colombia, AA 14490, Bogota DC (Colombia)

    2007-07-01

    The new oxide Ba{sub 2}NdZrO{sub 5.5} (BNZO) has been produced by the standard solid state reaction method. X-ray diffraction analysis (XRD) revealed that this synthesized material has an ordered complex cubic perovskite structure characteristic of A{sub 2}BB'O{sub 6} crystalline structure with a lattice parameter of a = 8.40 Aa. It was established through EDX analysis that there is no trace of impurities. Chemical stability of BNZO with YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO) has been studied by means of Rietveld analysis of experimental XRD data on several samples of BNZO-YBCO composites. Quantitative analysis of phases on XRD patterns show that all peaks have been indexed for both BNZO and YBCO, and no extra peak is detectable. YBCO and BNZO remain as two different separate phases in the composites with no chemical reaction. Electrical measurements also revealed that superconducting transition temperature of pure YBCO and BNZO-YBCO composites is 90 K. These favorable characteristics of BNZO show that it can be used as a potential substrate material for deposition of YBCO superconducting films. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  16. Factors affecting the superconductivity in the process of depositing Nd1.85Ce0.15CuO4-δ by the pulsed electron deposition technique

    Institute of Scientific and Technical Information of China (English)

    GUO; YanFeng

    2007-01-01

    On SrTiO3 single crystal substrate, by using the pulsed electron deposition technique, the high-quality electron doped Nd1.85Ce0.15CuO4-δsuperconducting film was successfully fabricated. After careful study on the R-T curves of the obtained samples deposited with different substrate temperatures, thicknesses, annealing methods and pulse frequencies, the effects of them on the superconductivity of the films were found, and the reasons were also analyzed. Additionally, by using the same model of the pulsed laser deposition technique, the relation between the target-to-substrate distance and the deposition pressure was drawn out as a quantitative one.  ……

  17. Theory of high gradient attractive magnetic separation of superconducting materials and its experimental verification by YBa{sub 2}Cu{sub 3}O{sub x} particles

    Energy Technology Data Exchange (ETDEWEB)

    Dessauges, L; Willems, J B; Favre, D; Bohrer, C; Helbling, F; Hulliger, J [Department of Chemistry and Biochemistry, University of Berne, Freiestrasse 3, CH-3012 Berne (Switzerland)

    2006-08-15

    The calculation of trajectories for sedimenting diamagnetic particles shows that superconducting matter in the Meissner or vortex state can be captured sidewise to a ferromagnetic wire magnetized perpendicular to its length. Capture is possible for externally applied fields lower than typical critical fields H{sub c1}(c), H{sub c1}(a,b) of cuprates. For single crystalline particles in the vortex state, the magnetic anisotropy may reduce the capture force because of alignment. Theoretical predictions were confirmed experimentally for suspensions of polycrystalline and single crystalline particles of YBa{sub 2}Cu{sub 3}O{sub x} (size range: 2-125 {mu}m) in liquid nitrogen. As a general conclusion we find that for the extraction of superconducting particles out of combinatorial ceramic reaction mixtures, separation in the Meissner state might be most effective because of the presence of an excess of normal state matter featuring a much lower diamagnetic susceptibility.

  18. Scaling between superconducting critical temperature and structural coherence length in YBa{sub 2}Cu{sub 3}O{sub 6.9} films

    Energy Technology Data Exchange (ETDEWEB)

    Gauzzi, A. [Ecole Polytechnique Federale, Lausanne (Switzerland). Dept. de Physique; Consiglio Nazionale delle Ricerche, Parma (Italy). Lab. MASPEC; Joensson-Aakerman, B.J.; Clerc-Dubois, A.; Pavuna, D. [Ecole Polytechnique Federale, Lausanne (Switzerland). Dept. de Physique

    2000-09-15

    Measurements of critical temperature T{sub c} in superconducting YBa{sub 2}Cu{sub 3}O{sub 6.9} films with reduced long-range structural order show the validity of the empirical scaling relation {delta}T{sub c}{proportional_to}r{sub c}{sup -2} between disorder-induced reduction of T{sub c} and structural coherence length r{sub c} in the ab-plane. This result is quantitatively explained by the disorder-induced confinement of the charge carriers within each ordered domain of size r{sub c}. Our analysis of the data based on this picture enables us to precisely determine the Ginzburg-Landau superconducting coherence length in the ab-plane, {xi}{sub ab} = 1.41 {+-} 0.04 nm. (orig.)

  19. Enhanced flux pinning properties in superconducting YBa{sub 2}Cu{sub 3}O{sub 7−z} films by a novel chemical doping approach

    Energy Technology Data Exchange (ETDEWEB)

    Wang, W.T., E-mail: wtwang@swjtu.edu.cn [Key Laboratory of Magnetic Levitation and Maglev Trains (Ministry of Education of China), Superconductivity R and D Center (SRDC), Southwest Jiaotong University, Mail Stop 165, Chengdu, Sichuan 610031 (China); Pu, M.H.; Lei, M.; Zhang, H.; Wang, Z. [Key Laboratory of Magnetic Levitation and Maglev Trains (Ministry of Education of China), Superconductivity R and D Center (SRDC), Southwest Jiaotong University, Mail Stop 165, Chengdu, Sichuan 610031 (China); Zhang, H. [Department of Physics, Peking University, Beijing 100871 (China); Cheng, C.H. [Key Laboratory of Magnetic Levitation and Maglev Trains (Ministry of Education of China), Superconductivity R and D Center (SRDC), Southwest Jiaotong University, Mail Stop 165, Chengdu, Sichuan 610031 (China); Superconductivity Research Group, School of Materials Science and Engineering, University of New South Wale, Sydney, 2052 NSW (Australia); Zhao, Y., E-mail: yzhao@swjtu.edu.cn [Key Laboratory of Magnetic Levitation and Maglev Trains (Ministry of Education of China), Superconductivity R and D Center (SRDC), Southwest Jiaotong University, Mail Stop 165, Chengdu, Sichuan 610031 (China); Superconductivity Research Group, School of Materials Science and Engineering, University of New South Wale, Sydney, 2052 NSW (Australia)

    2013-10-15

    Highlights: • Pure and Co-doped YBCO films were prepared by newly-developed chemical method. • The doped films have much denser and smoother surface microstructures. • Significantly enhanced fux-pinning properties have been obtained for dilute Co-doped flm. -- Abstract: Pure and cobalt-doped superconducting YBa{sub 2}Cu{sub 3}O{sub 7−z} (YBCO) films were prepared on (0 0 l) LaAlO{sub 3} substrate by a newly developed polymer-assisted metal organic deposition method. The cobalt-doped YBCO films display much denser and smoother surface microstructures and the superconducting transition temperature T{sub c} spans a small range of 1.7 K with the doping levels. Significantly enhanced flux-pinning properties have been obtained for dilute cobalt-doped film. This may be attributed to the good grain connections and the effective flux pinning centers introduced by cobalt doping.

  20. Anomalous vortex dynamics in κ-[bis(ethylenedithio)tetrathiafulvalene]2Cu[N(CN)2]Br: Evidence for field-induced magnetic order and unconventional superconductivity

    Science.gov (United States)

    Lahaise, U. G.; Chen, Qun; de Long, L. E.; Brock, C. P.; Wang, H. H.; Carlson, K. D.; Schlueter, J. A.; Williams, J. M.

    1995-02-01

    Anisotropic superconducting flux-line behavior of single-crystal κ-[bis(ethylenedithio)tetrathiaful- valene]2Cu[N(CN)2]Br has been studied with dc magnetization and vibrating-reed (VR) techniques. A peak at T*(H) in the temperature dependence of the VR inverse quality factor 1/Q exhibits a shoulder for magnetic fields 0<μ0H<=0.5 T parallel to the conducting ac plane. The shoulder becomes unresolved near a kink in T*(H) at μ0H~=0.7 T. Discontinuities in 1/Q and the VR frequency shift occur for 0.1<=μ0H<=1.3 T applied perpendicular to the ac plane and temperatures T<=20 K, well into the normal state. These anomalies are preliminary evidence for a field-induced magnetic phase transition and unconventional superconductivity.

  1. Synthesis of Y1-xAlxBa2Cu3O7-δ via combustion route: Effects of Al2O3 nanoparticles on superconducting properties

    Science.gov (United States)

    Mohd Suan, Mohd Shahadan; Johan, Mohd Rafie

    2017-02-01

    Combustion reaction was used to synthesis Al2O3 nanoparticles embedded Y1-xAlxBa2Cu3O7-δ simultaneously. The effects of Al2O3 nanoparticles with nominal molar mass (xmol) of 0.02, 0.04, 0.06, 0.08 and 0.10 towards the critical current density JC of Y1-xAlxBa2Cu3O7-δ were verified by magnetic measurement. Resulted XRD patterns revealed that the calcined samples consist of pure Al2O3 and Y1-xAlxBa2Cu3O7-δ phases which had been confirmed by EDX results. The SEM images showed that Al2O3 nanoparticles ( 10 nm) were distributed in polycrystalline YBa2Cu3O7-δ grains and grain boundaries. The presence of higher concentration of Al2O3 nanoparticles has developed Al3+ rich spots which diffused within the YBa2Cu3O7-δ superconducting matrix to form Y1-xAlxBa2Cu3O7-δ and was confirmed by EDX analysis. The samples were electrically superconducting at temperature above 85 K as measured by using standard four-probe technique. The magnetic field (H) dependent magnetization (M), M-H hysteresis loops measured at 77 K for xmol≤0.06 samples are significantly improved attributed to the increase of trapped fluxes in the samples. Remarkable increase of magnetic JC (H) in Al2O3 nanoparticles added samples compared to the as prepared polycrystalline YBa2Cu3O7-δ sample indicating strong pinning effect. It is suggested that well-distributed Al2O3 nanoparticles in the polycrystalline YBa2Cu3O7-δ matrix achieved via auto-combustion reaction has efficiently pin the magnetic vortex. The magnetic JC was optimized to 6 kAcm-2 in xmol=0.06 sample. On the other hand, insignificant magnetic JC improvement in xmol≥0.08 samples is probably resulted from the agglomerated Al2O3 nanoparticles in Y1-xAlxBa2Cu3O7-δ phase.

  2. Experimental evidence for s-wave pairing symmetry in superconducting Cu(x)Bi2Se3 single crystals using a scanning tunneling microscope.

    Science.gov (United States)

    Levy, Niv; Zhang, Tong; Ha, Jeonghoon; Sharifi, Fred; Talin, A Alec; Kuk, Young; Stroscio, Joseph A

    2013-03-15

    Topological superconductors represent a newly predicted phase of matter that is topologically distinct from conventional superconducting condensates of Cooper pairs. As a manifestation of their topological character, topological superconductors support solid-state realizations of Majorana fermions at their boundaries. The recently discovered superconductor Cu(x)Bi(2)Se(3) has been theoretically proposed as an odd-parity superconductor in the time-reversal-invariant topological superconductor class, and point-contact spectroscopy measurements have reported the observation of zero-bias conductance peaks corresponding to Majorana states in this material. Here we report scanning tunneling microscopy measurements of the superconducting energy gap in Cu(x)Bi(2)Se(3) as a function of spatial position and applied magnetic field. The tunneling spectrum shows that the density of states at the Fermi level is fully gapped without any in-gap states. The spectrum is well described by the Bardeen-Cooper-Schrieffer theory with a momentum independent order parameter, which suggests that Cu(x)Bi(2)Se(3) is a classical s-wave superconductor contrary to previous expectations and measurements.

  3. Silica functionalized Cu(II) catalysed selective oxidation of benzyl alcohols using TEMPO and molecular oxygen as an oxidant

    Indian Academy of Sciences (India)

    Manjulla Gupta; Pankaj Sharma; Monika Gupta; Rajive Gupta

    2015-08-01

    A general scheme for the oxidation of benzyl alcohols catalyzed by silica functionalized copper (II) has been designed. TEMPO, a free radical, assists this oxidation that was initiated by molecular oxygen which converts it to a primary oxidant. This catalytic combination i.e. SiO2 -Cu(II) in presence of TEMPO and oxygen provides excellent results in terms of yields and reaction time. SiO2 -Cu(II) was very well characterized by different spectroscopic techniques such as FTIR, XRD, TGA, XPS, EDAX, SEM, TEM and AAS and is recyclable upto five times which makes it economically beneficial.

  4. Crystallization and electrical resistivity of Cu{sub 2}O and CuO obtained by thermal oxidation of Cu thin films on SiO{sub 2}/Si substrates

    Energy Technology Data Exchange (ETDEWEB)

    De Los Santos Valladares, L., E-mail: ld301@cam.ac.uk [Cavendish Laboratory, University of Cambridge, J.J Thomson Av., Cambridge CB3 0HE (United Kingdom); Materials and Structures Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8503 (Japan); Departamento de Fisica, Universidade Federal de Pernambuco, 50670-901, Recife-Pe (Brazil); Salinas, D. Hurtado [Materials and Structures Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8503 (Japan); Laboratorio de Ceramicos y Nanomateriales, Facultad de Ciencias Fisicas, Universidad Nacional Mayor de San Marcos, Ap. Postal 14-0149, Lima (Peru); Dominguez, A. Bustamante [Laboratorio de Ceramicos y Nanomateriales, Facultad de Ciencias Fisicas, Universidad Nacional Mayor de San Marcos, Ap. Postal 14-0149, Lima (Peru); Najarro, D. Acosta [Instituto de Fisica, Departamento de Materia Condensada, Universidad Nacional Autonoma de Mexico, Ap. Postal 20-364, CP 01000 (Mexico); Khondaker, S.I. [NanoScience Technology Centre and Department of Physics, University of Central Florida, Orlando, FL 32826 (United States); Mitrelias, T.; Barnes, C.H.W. [Cavendish Laboratory, University of Cambridge, J.J Thomson Av., Cambridge CB3 0HE (United Kingdom); Aguiar, J. Albino [Departamento de Fisica, Universidade Federal de Pernambuco, 50670-901, Recife-Pe (Brazil); Majima, Y. [Materials and Structures Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8503 (Japan); CREST, Japan Science and Technology Agency (JST), 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8503 (Japan)

    2012-08-01

    In this work, we study the crystallization and electrical resistivity of the formed oxides in a Cu/SiO{sub 2}/Si thin film after thermal oxidation by ex-situ annealing at different temperatures up to 1000 Degree-Sign C. Upon increasing the annealing temperature, from the X ray diffractogram the phase evolution Cu {yields} Cu + Cu{sub 2}O {yields} Cu{sub 2}O {yields} Cu{sub 2}O + CuO {yields} CuO was detected. Pure Cu{sub 2}O films are obtained at 200 Degree-Sign C, whereas uniform CuO films without structural surface defects such as terraces, kinks, porosity or cracks are obtained in the temperature range 300-550 Degree-Sign C. In both oxides, crystallization improves with annealing temperature. A resistivity phase diagram, which is obtained from the current-voltage response, is presented here. The resistivity was expected to increase linearly as a function of the annealing temperature due to evolution of oxides. However, anomalous decreases are observed at different temperatures ranges, this may be related to the improvement of the crystallization and crystallite size when the temperature increases. - Highlights: Black-Right-Pointing-Pointer The crystallization and electrical resistivity of oxides in a Cu films are studied. Black-Right-Pointing-Pointer In annealing Cu films, the phase evolution Cu + Cu{sub 2}O {yields} Cu{sub 2}O {yields} Cu{sub 2}O + CuO {yields} CuO occurs. Black-Right-Pointing-Pointer A resistivity phase diagram, obtained from the current-voltage response, is presented. Black-Right-Pointing-Pointer Some decreases in the resistivity may be related to the crystallization.

  5. Preparation,Characterization of CuO/CeO2 and Cu/CeO2 Catalysts and Their Applications in Low-Temperature CO Oxidation

    Institute of Scientific and Technical Information of China (English)

    Zheng Xiucheng; Han Dongzhan; Wang Shuping; Zhang Shoumin; Wang Shurong; Huang Weiping; Wu Shihua

    2005-01-01

    CeO2 was synthesized via sol-gel process and used as supporter to prepare CuO/CeO2, Cu/CeO2 catalysts by impregnation method. The catalytic properties and characterization of CeO2, CuO/CeO2 and Cu/CeO2 catalysts were examined by means of a microreactor-GC system, HRTEM, XRD, TPR and XPS techniques. The results show that CuO has not catalytic activity and the activity of CeO2 is quite low for CO oxidation. However, the catalytic activity of CuO/CeO2 and Cu/CeO2 catalysts increases significantly. Furthermore, the activity of CuO/CeO2 is higher than that of Cu/CeO2 catalysts.

  6. Cu isotopes in marine black shales record the Great Oxidation Event.

    Science.gov (United States)

    Chi Fru, Ernest; Rodríguez, Nathalie P; Partin, Camille A; Lalonde, Stefan V; Andersson, Per; Weiss, Dominik J; El Albani, Abderrazak; Rodushkin, Ilia; Konhauser, Kurt O

    2016-05-01

    The oxygenation of the atmosphere ∼2.45-2.32 billion years ago (Ga) is one of the most significant geological events to have affected Earth's redox history. Our understanding of the timing and processes surrounding this key transition is largely dependent on the development of redox-sensitive proxies, many of which remain unexplored. Here we report a shift from negative to positive copper isotopic compositions (δ(65)CuERM-AE633) in organic carbon-rich shales spanning the period 2.66-2.08 Ga. We suggest that, before 2.3 Ga, a muted oxidative supply of weathering-derived copper enriched in (65)Cu, along with the preferential removal of (65)Cu by iron oxides, left seawater and marine biomass depleted in (65)Cu but enriched in (63)Cu. As banded iron formation deposition waned and continentally sourced Cu became more important, biomass sampled a dissolved Cu reservoir that was progressively less fractionated relative to the continental pool. This evolution toward heavy δ(65)Cu values coincides with a shift to negative sedimentary δ(56)Fe values and increased marine sulfate after the Great Oxidation Event (GOE), and is traceable through Phanerozoic shales to modern marine settings, where marine dissolved and sedimentary δ(65)Cu values are universally positive. Our finding of an important shift in sedimentary Cu isotope compositions across the GOE provides new insights into the Precambrian marine cycling of this critical micronutrient, and demonstrates the proxy potential for sedimentary Cu isotope compositions in the study of biogeochemical cycles and oceanic redox balance in the past.

  7. Cu isotopes in marine black shales record the Great Oxidation Event

    Science.gov (United States)

    Fru, Ernest Chi; Rodríguez, Nathalie P.; Partin, Camille A.; Lalonde, Stefan V.; Andersson, Per; Weiss, Dominik J.; El Albani, Abderrazak; Rodushkin, Ilia

    2016-05-01

    The oxygenation of the atmosphere ˜2.45-2.32 billion years ago (Ga) is one of the most significant geological events to have affected Earth's redox history. Our understanding of the timing and processes surrounding this key transition is largely dependent on the development of redox-sensitive proxies, many of which remain unexplored. Here we report a shift from negative to positive copper isotopic compositions (δ65CuERM-AE633) in organic carbon-rich shales spanning the period 2.66-2.08 Ga. We suggest that, before 2.3 Ga, a muted oxidative supply of weathering-derived copper enriched in 65Cu, along with the preferential removal of 65Cu by iron oxides, left seawater and marine biomass depleted in 65Cu but enriched in 63Cu. As banded iron formation deposition waned and continentally sourced Cu became more important, biomass sampled a dissolved Cu reservoir that was progressively less fractionated relative to the continental pool. This evolution toward heavy δ65Cu values coincides with a shift to negative sedimentary δ56Fe values and increased marine sulfate after the Great Oxidation Event (GOE), and is traceable through Phanerozoic shales to modern marine settings, where marine dissolved and sedimentary δ65Cu values are universally positive. Our finding of an important shift in sedimentary Cu isotope compositions across the GOE provides new insights into the Precambrian marine cycling of this critical micronutrient, and demonstrates the proxy potential for sedimentary Cu isotope compositions in the study of biogeochemical cycles and oceanic redox balance in the past.

  8. Electron-Phonon Anomaly Related to Charge Stripes: Static Stripe Phase Versus Optimally Doped Superconducting La1.85Sr0.15CuO4

    Science.gov (United States)

    Reznik, D.; Pintschovius, L.; Fujita, M.; Yamada, K.; Gu, G. D.; Tranquada, J. M.

    2007-05-01

    Inelastic neutron scattering was used to study the Cu-O bond-stretching vibrations in optimally doped La1.85Sr0.15CuO4 (Tc = 35 K) and in two other cuprates showing static stripe order at low temperatures, i.e. La1.48Nd0.4Sr0.12CuO4 and La1.875Ba0.125CuO4. All three compounds exhibit a very similar phonon anomaly, which is not predicted by conventional band theory. It is argued that the phonon anomaly reflects a coupling to charge inhomogeneities in the form of stripes, which remain dynamic in superconducting La1.85Sr0.15CuO4 down to the lowest temperatures. These results show that the phonon effect indicating stripe formation is not restricted to a narrow region of the phase diagram around the so-called 1/8 anomaly but occurs in optimally doped samples as well.

  9. A new RHQT Nb3Al superconducting wire with a Ta/Cu/Ta three-layer filament-barrier structure

    Science.gov (United States)

    Takeuchi, Takao; Tsuchiya, Kiyosumi; Nakagawa, Kazuhiko; Nimori, Shigeki; Banno, Nobuya; Iijima, Yasuo; Kikuchi, Akihiro; Nakamoto, Tatsushi

    2012-06-01

    To suppress the low-magnetic-field instability (flux jumps in low magnetic fields) of a rapid-heating, quenching and transformation (RHQT) processed Nb3Al superconductor, we had previously modified the cross-sectional design of an RHQT Nb3Al by adopting a Ta filament-barrier structure. Unlike Nb barriers, Ta barriers are not superconducting in magnetic fields at 4.2 K so that they electromagnetically decouple filaments. However, small flux jumps still occurred at 1.8 K, which is a typical operating temperature for the magnets used in high-energy particle accelerators. Furthermore, poor bonding at the Ta/Ta interface between neighboring Ta-coated jelly-roll (JR) filaments frequently caused precursor wires to break during drawing. To overcome these problems, we fabricated a new RHQT Nb3Al wire with a Ta/Cu/Ta three-layer filament-barrier structure for which an internal stabilization technique (Cu rods encased in Ta are dispersed in the wire cross section) was extended. Removing the Ta/Ta interface in the interfilamentary barrier (JR filament/Ta/Cu/Ta/JR filament) allowed precursor wires to be drawn without breaking. Furthermore, the Cu filament barrier electromagnetically decoupled filaments to suppress flux jumps at 1.8 K. The ductile Cu layer also improved the bending strain tolerance of RHQT Nb3Al.

  10. Cu Binding to Iron Oxide-Organic Matter Coprecipitates in Solid and Dissolved Phases

    Science.gov (United States)

    Vadas, T. M.; Koenigsmark, F.

    2015-12-01

    Recent studies indicate that Cu is released from wetlands following storm events. Assymetrical field flow field fractionation (AF4) analyses as well as total and dissolved metal concentration measurements suggest iron oxide-organic matter complexes control Cu retention and release. Coprecipitation products of Fe oxide and organic matter were prepared under conditions similar to the wetland to assess Cu partitioning to and availability from solid phases that settle from solution as well as phases remaining suspended. Cu coprecipitation and sorption to organomineral precipitation solids formed at different Fe:organic carbon (OC) ratios were compared for net Cu removal and extractability. As more humic acid was present during precipitation of Fe, TEM images indicated smaller Fe oxide particles formed within an organic matrix as expected. In coprecipitation reactions, as the ratio of Fe:OC decreased, more Cu was removed from solution at pH 5.5 and below. However, in sorption reactions, there was an inhibition of Cu removal at low OC concentrations. As the pH increased from 5.5 to 7 and as solution phase OC concentration increased, more Cu remained dissolved in both coprecipitation and sorption reactions. The addition of Ca2+, glycine, histidine and citric acid or lowering the pH resulted in more extractable Cu from the coprecipitation compared with the sorption reactions. The variations in Cu extraction were likely due to a combination of a more amorphous structure in CPT products, and the relative abundance of available Fe oxide or OC binding sites. Suspended Fe oxide-organic matter coprecipitates were assessed using AF4 coupled to online TOC analysis and ICP-MS. In laboratory prepared samples, Cu was observed in a mixture of small 1-5 nm colloids of Fe oxide-organic matter precipitates, but the majority was observed in larger organic matter colloids and were not UV absorbing, suggesting more aliphatic carbon materials. In field samples, up to 60% of the dissolved Cu

  11. Superconducting Bi(1.5)Pb(0.5)Sr2Ca2Cu3O(x) ceramics by rapid melt quenching and glass crystallization

    Science.gov (United States)

    Bansal, Narottam P.

    1990-01-01

    The preparation of superconducting Bi(1.5)Pb(0.5)Sr2Ca2Cu3O(x) in the glassy state is described, and the results of a study of its crystallization kinetics are presented. The annealing parameters for transforming the glass into a superconductor containing a large fraction of the high-Tc phase were determined. It was found that prolonged annealing (longer than 10 days) in air at 840 C, followed by slow cooling, results in the Tc of 107.2 K and a sharp transition of 2 K.

  12. Imaging the impact of single oxygen atoms on superconducting Bi(2+y)Sr(2-y)CaCu2O(8+x).

    Science.gov (United States)

    Zeljkovic, Ilija; Xu, Zhijun; Wen, Jinsheng; Gu, Genda; Markiewicz, Robert S; Hoffman, Jennifer E

    2012-07-20

    High-temperature cuprate superconductors display unexpected nanoscale inhomogeneity in essential properties such as pseudogap energy, Fermi surface, and even superconducting critical temperature. Theoretical explanations for this inhomogeneity have ranged from chemical disorder to spontaneous electronic phase separation. We extend the energy range of scanning tunneling spectroscopy on Bi(2+y)Sr(2-y)CaCu(2)O(8+x), allowing a complete mapping of two types of interstitial oxygen dopants and vacancies at the apical oxygen site. We show that the nanoscale spatial variations in the pseudogap states are correlated with disorder in these dopant concentrations, particularly that of apical oxygen vacancies.

  13. Doping-induced change in the interlayer transport mechanism of Bi_{2}Sr_{2}CaCu_{2}O_{8+delta} near the superconducting transition temperature.

    Science.gov (United States)

    Katterwe, S O; Rydh, A; Krasnov, V M

    2008-08-22

    We perform a detailed study of temperature, bias, and doping dependence of interlayer transport in the layered high temperature superconductor Bi_{2}Sr_{2}CaCu_{2}O_{8+delta}. We observe that the shape of interlayer characteristics in underdoped crystals exhibits a remarkable crossover at the superconducting transition temperature: from thermal activation-type above T_{c} to almost T-independent quantum tunneling-type below T_{c}. Our data provide insight into the nature of interlayer transport and indicate that its mechanism changes with doping: from the conventional single quasiparticle tunneling in overdoped to a progressively increasing Cooper pair contribution in underdoped crystals.

  14. Quantitive analysis of lattice disorder and superconducting transition in exptaxial YBa{sub 2}Cu{sub 3}O{sub 6.9} films

    Energy Technology Data Exchange (ETDEWEB)

    Gauzzi, A.; Pavuna, D. [Ecole Polytechnique Federale de Lausanne (Switzerland)

    1996-02-01

    The authors show that the average lattice disorder in YBa{sub 2}Cu{sub 3}O{sub 6.9} films grown by ion-beam sputtering is homogeneous and can be quantified by introducing the lattice coherence length r{sub c} that is extracted from the width of X-ray diffraction rocking curves. The superconducting properties of the films are correlated with r{sub c}: T{sub c} decreases with increasing disorder for r{sub c}{approx_lt}10 nm, while the width of the resistive transition and the normal-state resistivity increase.

  15. Magnetic measurements of superconducting glass-ceramic fine rods in Bi sub 1 Ca sub 1 Sr sub 1 Cu sub 2 Al sub 0. 5 O sub x prepared under a temperature gradient

    Energy Technology Data Exchange (ETDEWEB)

    Higashida, Y.; Yokoyama, H.; Michishita, K.; Kubo, Y.; Yoshida, H. (R D Laboratory, Japan Fine Ceramics Center, Mutuno-cho, Atsuta-ku, Nagoya 456, Japan (JP)); Abe, Y.; Hosono, H. (Department of Materials Science and Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466, Japan)

    1989-10-09

    It is shown that the crystallization of the glass precursor under a temperature gradient is very effective for preparing the superconducting glass ceramics in the Bi-Ca-Sr-Cu-O system. The magnetization measurements show that the specimen prepared under a temperature gradient has a magnetization hysteresis several times larger at 4.2 K than that prepared under no temperature gradient; the coupling between superconducting grains of the former is stronger than that of the latter.

  16. Magnetic measurements of superconducting glass-ceramic fine rods in Bi1Ca1Sr1Cu2Al(0.5)O(x) prepared under a temperature gradient

    Science.gov (United States)

    Higashida, Yutaka; Yokoyama, Hisanori; Michishita, Kazuo; Kubo, Yukio; Yoshida, Hiroshi

    1989-10-01

    It is shown that the crystallization of the glass precursor under a temperature gradient is very effective for preparing the superconducting glass ceramics in the Bi-Ca-Sr-Cu-O system. The magnetization measurements show that the specimen prepared under a temperature gradient has a magnetization hysteresis several times larger at 4.2 K than that prepared under no temperature gradient; the coupling between superconducting grains of the former is stronger than that of the latter.

  17. Kinetics of carbon monoxide oxidation over modified supported CuO catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Loc, Luu Cam; Tri, Nguyen; Cuong, Hoang Tien; Thoang, Ho Si [Vietnam Academy of Science and Technology (VAST), Ho Chi Minh City (Viet Nam). Inst. of Chemical Technology; Agafonov, Yu.A.; Gaidai, N.A.; Lapidus, A.L. [Russian Academy of Sciences, Moscow (Russian Federation). N.D. Zelinsky Institute of Organic Chemistry

    2013-11-01

    The following supported on {gamma}-Al{sub 2}O{sub 3} catalysts: 10(wt.)%CuO (CuAl), 10%CuO+10%Cr{sub 2}O{sub 3} (CuCrAl) and 10%CuO+20%CeO{sub 2} (CuCeAl) were under the investigation. Physico-chemical characteristics of the catalysts were determined by the methods of BET, X-ray Diffraction (XRD), and Temperature-Programmed Reduction (TPR). A strong interaction of copper with support in CuAl resulted in the formation of low active copper aluminates. The bi-oxide CuCrAl was more active than CuAl owing to the formation of high catalytically active spinel CuCr{sub 2}O{sub 4}. The fact of very high activity of the sample CuCeAl can be explained by the presence of the catalytically active form of CuO-CeO{sub 2}-Al{sub 2}O{sub 3}. The kinetics of CO total oxidation was studied in a gradientless flow-circulating system at the temperature range between 200 C and 270 C. The values of initial partial pressures of carbon monoxide (P{sup o}{sub CO}), oxygen (P{sup o}{sub O2}), and specially added carbon dioxide (P{sup o}{sub CO{sub 2}}) were varied in ranges (hPa): 10 / 45; 33 / 100, and 0 / 30, respectively. (orig.)

  18. Study of superconducting and non-superconducting (Cu, Cr)-1212 compounds by high-resolution TEM and electron energy loss spectroscopy

    CERN Document Server

    Anan, Y; Kurami, H; Hatano, J; Tsutsumi, S; Kimoto, K; Matsui, Y

    2001-01-01

    Structure of YSr/sub 2-x/Ba/sub x/Cu/sub 2.8/Cr/sub 0.2/O/sub y/ (x =0-1.5) superconductors are examined by electron diffraction, HRTEM and electron energy loss spectroscopy (EELS). YSr/sub 2/Cu/sub 2.8/Cr /sub 0.2/O/sub y/ (x=0) shows incommensurate superstructure with 3.67a/sub 0/ due to lattice strain and mixed intergrowth of -(Cr-Cu- Cu-Cu-Cr)- and -(Cr-Cu-Cu-Cr)- sequences. In the h 0 l electron diffraction pattern the wavevector [~0.27, 0, 1/2] due to the incommensurate superstructure disappear in the crystal with high Ba contain (x>or=1.0). This suggests that structural distortion decreases with Ba substitution. At the same time, Cr-L3, L2 edge of EELS spectra shifts toward the low-energy side with increase of Ba content. (13 refs).

  19. Supported Pd-Cu bimetallic nanoparticles that have high activity for the electrochemical oxidation of methanol.

    Science.gov (United States)

    Yin, Zhen; Zhou, Wu; Gao, Yongjun; Ma, Ding; Kiely, Christopher J; Bao, Xinhe

    2012-04-16

    Monodisperse bimetallic Pd-Cu nanoparticles with controllable size and composition were synthesized by a one-step multiphase ethylene glycol (EG) method. Adjusting the stoichiometric ratio of the Pd and Cu precursors afforded nanoparticles with different compositions, such as Pd(85)-Cu(15), Pd(56)-Cu(44), and Pd(39)-Cu(61). The nanoparticles were separated from the solution mixture by extraction with non-polar solvents, such as n-hexane. Monodisperse bimetallic Pd-Cu nanoparticles with narrow size-distribution were obtained without the need for a size-selection process. Capping ligands that were bound to the surface of the particles were removed through heat treatment when the as-prepared nanoparticles were loaded onto a Vulcan XC-72 carbon support. Supported bimetallic Pd-Cu nanoparticles showed enhanced electrocatalytic activity towards methanol oxidation compared with supported Pd nanoparticles that were fabricated according to the same EG method. For a bimetallic Pd-Cu catalyst that contained 15 % Cu, the activity was even comparable to the state-of-the-art commercially available Pt/C catalysts. A STEM-HAADF study indicated that the formation of random solid-solution alloy structures in the bimetallic Pd(85)-Cu(15)/C catalysts played a key role in improving the electrochemical activity. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Site-specifically Hydrolytic Cleavage of Oxidized Insulin B Chain With Cu(II) Ion

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Electrospray mass spectrometry investigation shows that denatured oxidized insulin B chain can be selectively cleaved by simple Cu(II) ion and the site of cleavage is at Gly8-Ser9 bond which is second amide bond left from His 10 in the sequence of oxidized insulin B chain.

  1. Persistence of the superconducting condensate far above the critical temperature of YBa2(Cu,Zn)3O(y) revealed by c-axis optical conductivity measurements for several Zn concentrations and carrier doping levels.

    Science.gov (United States)

    Uykur, Ece; Tanaka, Kiyohisa; Masui, Takahiko; Miyasaka, Shigeki; Tajima, Setsuko

    2014-03-28

    The superconductivity precursor phenomena in high temperature cuprate superconductors is studied by direct measurements of the superconducting condensate with the use of the c-axis optical conductivity of YBa2(Cu1-xZnx)3Oy for several doping levels (p) as well as for several Zn concentrations. Both the real and imaginary parts of the optical conductivity clearly show that the superconducting carriers persist up to the high temperatures Tp that is higher than the critical temperature Tc but lower than the pseudogap temperature T*. Tp increases with reducing doping level like T*, but decreases with Zn substitution unlike T*.

  2. Out-of-plane Ionicity versus In-plane Covalency Interplay in High-Tc Superconducting Oxides

    OpenAIRE

    2015-01-01

    It seems that the remarkable properties of the high temperature superconducting oxides, especially the Insulator-Metal Transition (IMT) and the Metal-Superconductor Transition (MST) both originate from the competition (interplay) between ionic versus in-plane covalence nature of bonds in these materials. As a result of this competition, the microscopic order parameter, that is firmly identified to be the local field estimated from the ionic polarization at the sub-unit level (one half of the ...

  3. Percolative superconductivity in La{sub 2}CuO{sub 4.06} by lattice granularity patterns with scanning micro x-ray absorption near edge structure

    Energy Technology Data Exchange (ETDEWEB)

    Poccia, Nicola [MESA Institute for Nanotechnology, University of Twente, P. O. Box 217, 7500AE Enschede (Netherlands); RICMASS Rome International Center for Materials Science Superstripes, via dei Sabelli 119A, 00185 Roma (Italy); Chorro, Matthieu [Synchrotron SOLEIL L' Orme des Merisiers, 91190 Paris S.Aubin (France); Ricci, Alessandro [Deutsches Elektronen-Synchrotron DESY, Notkestraße 85, D-22607 Hamburg (Germany); RICMASS Rome International Center for Materials Science Superstripes, via dei Sabelli 119A, 00185 Roma (Italy); Xu, Wei [Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); Marcelli, Augusto [Istituto Nazionale di Fisica Nucleare - Laboratori Nazionali di Frascati, 00044 Frascati, Rome (Italy); NSRL, University of Science and Technology of China, Hefei 230026 (China); RICMASS Rome International Center for Materials Science Superstripes, via dei Sabelli 119A, 00185 Roma (Italy); Campi, Gaetano [Institute of Crystallography, CNR, via Salaria Km 29.300, Monterotondo, 00015 Rome (Italy); RICMASS Rome International Center for Materials Science Superstripes, via dei Sabelli 119A, 00185 Roma (Italy); Bianconi, Antonio [RICMASS Rome International Center for Materials Science Superstripes, via dei Sabelli 119A, 00185 Roma (Italy); Institute of Crystallography, CNR, via Salaria Km 29.300, Monterotondo, 00015 Rome (Italy)

    2014-06-02

    The simplest cuprate superconductor La{sub 2}CuO{sub 4+y} with mobile oxygen interstitials exhibits a clear phase separation. It is known that oxygen interstitials enter into the rocksalt La{sub 2}O{sub 2+y} spacer layers forming oxygen interstitials rich puddles and poor puddles but only recently a bulk multiscale structural phase separation has been observed by using scanning micro X-ray diffraction. Here we get further information on their spatial distribution, using scanning La L{sub 3}-edge micro X-ray absorption near edge structure. Percolating networks of oxygen rich puddles are observed in different micrometer size portions of the crystals. Moreover, the complex surface resistivity shows two jumps associated to the onset of intra-puddle and inter-puddles percolative superconductivity. The similarity of oxygen doped La{sub 2}CuO{sub 4+y}, with the well established phase separation in iron selenide superconductors is also discussed.

  4. Charge Order, Metallic Behavior, and Superconductivity in La{2-x}Ba{x}CuO{4} with x = 1/8

    Energy Technology Data Exchange (ETDEWEB)

    Homes,C.; Dordevic, S.; Gu, G.; Li, Q.; Valla, T.; Tranquada, J.

    2006-01-01

    The ab-plane optical properties of a cleaved single crystal of La{sub 2-x}Ba{sub x}CuO{sub 4} for x=1/8 (T{sub c}{approx}2.4 K) have been measured over a wide frequency and temperature range. The low-frequency conductivity is Drude-like and shows a metallic response with decreasing temperature. However, below {approx}60 K, corresponding to the onset of charge-stripe order, there is a rapid loss of spectral weight below about 40 meV. The behavior is quite different from that typically associated with the pseudogap in the normal state of the cuprates. Instead, the gapping of the normal-state single-particle excitations looks surprisingly similar to that observed in superconducting La{sub 2-x}Sr{sub x}CuO{sub 4}, including the presence of a residual Drude peak with reduced weight.

  5. Superconducting characterization of Ni/Bi{sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub y} superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Tokuda, T.; Hidaka, K. [Department of Electrical and Electric Engineering, Tottori University, 4-101, Koyama-Minami, Tottori 680-8552 (Japan); Kishida, S. [Department of Electrical and Electric Engineering, Tottori University, 4-101, Koyama-Minami, Tottori 680-8552 (Japan)], E-mail: kishida@ele.tottori-u.ac.jp

    2007-10-01

    We deposited non-superconducting materials, Ni metal on the surface of Bi{sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub y} (BSCCO) superconductors. Critical temperature (T{sub c}) and critical current (I{sub c}) of Ni/BSCCO specimens decreased with increasing thickness of Ni films. This indicates that the T{sub c} and the I{sub c} of the BSCCO films are degraded with a thickness of Ni. This behavior is approximately equal to that of a Ni/YBa{sub 2}Cu{sub 3}O{sub y} (YBCO) specimen, where the T{sub c} and the I{sub c} of it were dependent on rf power during Ni deposition. Therefore, the degradation of the Ni/BSCCO specimen may be due to the Ni diffusion into the BSCCO films.

  6. An NMR approach to the superconducting regime of the spin ladder compound Sr{sub 2}Ca{sub 12}Cu{sub 24}O{sub 41}

    Energy Technology Data Exchange (ETDEWEB)

    Piskunov, Y.; Jerome, D.; Auban-Senzier, P.; Wzietek, P. [Universite de Paris-Sud, Orsay (France). Lab. de Physique des Solides; Ammerahl, U. [Laboratoire de Physicochimie des Solides (France); II. Physikalisches Institut, Universitaet zu Koeln, Zuelpicher Str. 77, 50937 Koeln (Germany); Dhalenne, G.; Revcolevschi, A. [Laboratoire de Physicochimie des Solides (France)

    2000-02-01

    {sup 63}Cu-NMR experiments of Knight shift and relaxation time T{sub 1} have been performed on the two-leg spin ladders of a Sr{sub 2}Ca{sub 12}Cu{sub 24}O{sub 41} single crystal at several pressures up to the critical pressure P{sub c} for the stabilization of a superconducting ground state. The data confirm the onset of low-lying spin excitations at P{sub c} observed previously (1998) and reveal a marked decrease of the spin gap under pressures above 20 kbar although a significant fraction of the spin excitations remains gappedat P{sub c}=32 kbar. A comparison between NMR and transport data under pressure suggests that the depression of the spin gap can be ascribed to an increase in the interladder exchange coupling, possibly mediated by the ladder-chain interaction along the b-direction. (orig.)

  7. Cu-Ag core-shell nanoparticles with enhanced oxidation stability for printed electronics.

    Science.gov (United States)

    Lee, Changsoo; Kim, Na Rae; Koo, Jahyun; Lee, Yung Jong; Lee, Hyuck Mo

    2015-11-13

    In this work, we synthesized uniform Cu-Ag core-shell nanoparticles using a facile two-step process that consists of thermal decomposition and galvanic displacement methods. The core-shell structure of these nanoparticles was confirmed through characterization using transmission electron microscopy, energy-dispersive spectroscopy, and x-ray diffraction. Furthermore, we investigated the oxidation stability of the Cu-Ag core-shell nanoparticles in detail. Both qualitative and quantitative x-ray photoelectron spectroscopy analyses confirm that the Cu-Ag core-shell nanoparticles have considerably higher oxidation stability than Cu nanoparticles. Finally, we formulated a conductive ink using the synthesized nanoparticles and coated it onto glass substrates. Following the sintering process, we compared the resistivity of the Cu-Ag core-shell nanoparticles with that of the Cu nanoparticles. The results of this study clearly show that the Cu-Ag core-shell nanoparticles can potentially be used as an alternative to Ag nanoparticles because of their superior oxidation stability and electrical properties.

  8. Cu-Ag core-shell nanoparticles with enhanced oxidation stability for printed electronics

    Science.gov (United States)

    Lee, Changsoo; Kim, Na Rae; Koo, Jahyun; Jong Lee, Yung; Lee, Hyuck Mo

    2015-11-01

    In this work, we synthesized uniform Cu-Ag core-shell nanoparticles using a facile two-step process that consists of thermal decomposition and galvanic displacement methods. The core-shell structure of these nanoparticles was confirmed through characterization using transmission electron microscopy, energy-dispersive spectroscopy, and x-ray diffraction. Furthermore, we investigated the oxidation stability of the Cu-Ag core-shell nanoparticles in detail. Both qualitative and quantitative x-ray photoelectron spectroscopy analyses confirm that the Cu-Ag core-shell nanoparticles have considerably higher oxidation stability than Cu nanoparticles. Finally, we formulated a conductive ink using the synthesized nanoparticles and coated it onto glass substrates. Following the sintering process, we compared the resistivity of the Cu-Ag core-shell nanoparticles with that of the Cu nanoparticles. The results of this study clearly show that the Cu-Ag core-shell nanoparticles can potentially be used as an alternative to Ag nanoparticles because of their superior oxidation stability and electrical properties.

  9. Observation of distinct, temperature dependent flux noise near bicrystal grain boundaries in YBa2Cu3O7-x films

    DEFF Research Database (Denmark)

    Bukh, K. R.; Jacobsen, Claus Schelde; Hansen, Jørn Bindslev

    2000-01-01

    The characteristics of the magnetic flux noise in high temperature superconducting thin-films of yttrium-barium-copper-oxide (YBa2Cu3O7) in the vicinity of artificial grain boundaries have been studied by means of a low critical temperature superconducting quantum interference device (SQUID...

  10. Evaluation of the Cu-CMP process by TOF-SIMS and XPS: time dependence of Cu surface adsorbents and oxidation states

    Science.gov (United States)

    Nishi, A.; Sado, M.; Miki, T.; Fukui, Y.

    2003-01-01

    CMP (chemical mechanical polishing) and the post-CMP cleaning for damascene processes are necessary to produce Cu interconnects. Many kinds of additives, such as an oxidizer, an inhibitor, etching chemicals, are usually in the CMP slurries. Cu films, however, are easily oxidized and corroded by those chemicals, so it is important to choose the chemicals and to decide how long Cu films are treated with them. If we can grasp the residues on Cu films and the Cu oxidation, it will be easy to optimize the conditions of CMP processes. Then we treated Cu films with benzotriazole (BTA), a well-known Cu corrosion inhibitor, in some conditions, and we investigated the residues and the Cu oxidation. The results of TOF-SIMS measurements seem to correlate with the results of XPS measurements. Ions derived from BTA are at high relative intensities in a sample treated with high concentrated BTA, and it is not so highly oxidized. On the other hand, they are at low relative intensities in a sample treated with acids, and it is rapidly oxidized. These analysis methods can be applied in various fields.

  11. Ordered PdCu-Based Nanoparticles as Bifunctional Oxygen-Reduction and Ethanol-Oxidation Electrocatalysts.

    Science.gov (United States)

    Jiang, Kezhu; Wang, Pengtang; Guo, Shaojun; Zhang, Xu; Shen, Xuan; Lu, Gang; Su, Dong; Huang, Xiaoqing

    2016-07-25

    The development of superior non-platinum electrocatalysts for enhancing the electrocatalytic activity and stability for the oxygen-reduction reaction (ORR) and liquid fuel oxidation reaction is very important for the commercialization of fuel cells, but still a great challenge. Herein, we demonstrate a new colloidal chemistry technique for making structurally ordered PdCu-based nanoparticles (NPs) with composition control from PdCu to PdCuNi and PtCuCo. Under the dual tuning on the composition and intermetallic phase, the ordered PdCuCo NPs exhibit better activity and much enhanced stability for ORR and ethanol-oxidation reaction (EOR) than those of disordered PdCuM NPs, the commercial Pt/C and Pd/C catalysts. The density functional theory (DFT) calculations reveal that the improved ORR activity on the PdCuM NPs stems from the catalytically active hollow sites arising from the ligand effect and the compressive strain on the Pd surface owing to the smaller atomic size of Cu, Co, and Ni. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Effects of oxide precursors on superconducting properties of polycrystalline SmFeAsO1-xFx

    Science.gov (United States)

    Yuan, F. F.; Ding, Y.; Sun, Y.; Zhuang, J. C.; Zhou, W.; Li, G. Z.; Sumption, M.; Li, X. W.; Shi, Z. X.

    2013-12-01

    A series of polycrystalline SmFeAsO1-xFx samples were synthesized by one-step and two-step method at ambient pressure using different oxide precursors, namely As2O3, Fe2O3 and nano-Fe2O3 powder, as the source of element O. Results of X-ray diffraction and magnetic measurements manifest that starting oxides affected the phase formation and superconducting properties of SmFeAsO1-xFx. As2O3 as oxide precursor contributes to the fast formation of superconducting phase for a short period of sintering time. And samples prepared using As2O3 show higher superconducting transition temperature Tc and more stable fluorine doping level. Compared with Fe2O3, nano-Fe2O3 promotes fluorine doping into the O site. While using Fe2O3 leads to higher level of Fe and SmOF impurities. The critical current density Jcm were derived from magnetic hysteresis loops. Sample prepared using As2O3 shows higher Jcm in low temperature and high magnetic fields.

  13. Metastable Demixing of Supercooled Cu-Co and Cu-Fe Alloys in an Oxide Flux

    Science.gov (United States)

    Li, D.; Robinson, M. B.; Rathz, T. J.; Williams, G.

    1998-01-01

    A systematic study on the liquid separation in supercooled Cu-Co and Cu-Fe alloys was performed using a melt fluxing which permits high supercooling to be achieved. Moreover, this method renders it possible to directly measure binodal temperatures and establish metastable liquid miscibility gap (LMG). All phase-separated samples at compositions ranging from 10 to 80 wt pct Co or to 83 wt pct Fe were found to exhibit droplet-shaped morphologies, in spite of various droplet distributions. Uniformly dispersed microstructures were obtained as the minority component was less than 20 vol.%; while beyond this percentage, serious coarsening was brought about. Calculations of the miscibility gap in the Cu-Co system and Stokes movement velocity of Co and Fe droplets in Cu matrix were made to analyze the experimental results.

  14. More Cu, more problems: Decreased CO2 conversion ability by Cu-doped La0.75Sr0.25FeO3 perovskite oxides

    Science.gov (United States)

    Daza, Yolanda A.; Maiti, Debtanu; Hare, Bryan J.; Bhethanabotla, Venkat R.; Kuhn, John N.

    2016-06-01

    The effect of Cu doping on the conversion of CO2 to CO was investigated on H2-reduced La0.75Sr0.25FeO3 perovskite oxides. Six La0.75Sr0.25Fe1 -YCuYO3 perovskites, labeled Cu100*Y (with Y = 0, 0.10, 0.25, 0.50, 0.75, and 1) were synthesized and characterized through X-ray diffraction (XRD), temperature-programmed oxygen vacancy formation, and temperature-programmed reduction (TPR). The incorporation of Cu facilitates the formation of oxygen vacancies at lower temperatures but also increased the instability of the perovskite. DFT simulations suggested that the Cu10 sample is favored to produce oxygen vacancies compared to Cu0 and Cu25 samples, which was consistent with experimental oxygen vacancy formation results. For the Cu0, Cu10, and Cu25 samples, temperature-programmed CO2 conversion (TPO-CO2) after isothermal H2-reduction at 450 °C and post-reduction XRD were performed to evaluate the ability of the materials to convert CO2 at low temperatures and to identify the crystalline phases active in the reaction. The peak conversion of CO2 to CO was achieved 30 °C lower on the Cu10 sample versus the Cu0, but less CO was produced, due to a decreased re-oxidation activity of the Cu-doped samples. CO production was inhibited in the Cu25 sample, likely due to a combined effect of poor CO2 dissociative chemisorption energies on metallic Cu and increased thermodynamic stability of the oxygen vacant perovskites. Control experiments (Cu deposited onto La0.75Sr0.25FeO3) indicated the stability of the copper-containing perovskite oxides phases was the primary limiting factor preventing CO formation from CO2.

  15. Catalytic wet oxidation of dyehouse effluents with Cu/Al{sub 2}O{sub 3} and Al-Cu pillared clays

    Energy Technology Data Exchange (ETDEWEB)

    Lee, D.K.; Kim, S.C.; Kim, D.S.; Lee, G.S.; Yoon, S.B. [Dept. of Chemical Engineering/Environmental Protection, Environment and Regional Development Inst., Gyeongsang National Univ., Gyeongnam (Korea)

    2003-07-01

    Catalytic wet oxidation of real dyehouse effluents was performed in a batch reactor and a continuous flow pilot plant scale reactor by using Cu/Al{sub 2}O{sub 3} and Al-Cu-PILC catalysts. Hydrogen peroxide was used as the oxidant. The removal of TOC and color was strongly related to the consumption of H{sub 2}O{sub 2} and the subsequent formation of HO-. Copper components in the catalysts, especially in the Al-Cu-PILCs, showed successful activity toward complete removal of TOC and color. In addition the Al-Cu-PILC catalysts were extremely stable against copper leaching. (orig.)

  16. Enhanced catalytic toluene oxidation by interaction between copper oxide and manganese oxide in Cu-O-Mn/γ-Al2O3 catalysts

    Science.gov (United States)

    Wang, Hongpei; Lu, Yiyuan; Han, YuXiang; Lu, Chunliang; Wan, Haiqin; Xu, Zhaoyi; Zheng, Shourong

    2017-10-01

    Toward catalytic oxidation of toluene, Cu-O-Mn/γ-Al2O3 catalysts with series molar ratios of Cu/Mn were prepared using an impregnation method. The surface structure and chemical state of the as-prepared catalysts were characterized by the combination of X-ray diffraction (XRD), N2 adsorption/desorption, UV-vis spectroscopy (UV-vis), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and H2 temperature programmed reduction (H2-TPR). The results demonstrated that copper oxide and manganese oxide were highly dispersed on the γ-Al2O3 support. Meanwhile, there is an interaction between copper oxide and manganese oxide, depending on the atomic ratio of Cu/Mn. At the ratio of Cu/Mn = 1:1.5, the interaction between Cu and Mn oxides reached the strongest, thus leading to the highest catalytic activity and turn over frequency among all of the ratios. The temperature for complete combustion of toluene over the strongest interaction sample could be 350 °C, which could further decrease to 300 °C when tuning the loading amount of Cu and Mn. Findings in this work are important for the design of efficient catalyst by tuning the interaction between each components.

  17. Determination of surface resistance and magnetic penetration depth of superconducting YBa2Cu3O(7-delta) thin films by microwave power transmission measurements

    Science.gov (United States)

    Bhasin, K. B.; Warner, J. D.; Miranda, F. A.; Gordon, W. L.; Newman, H. S.

    1991-01-01

    A novel waveguide power transmission measurement technique was developed to extract the complex conductivity of superconducting thin films at microwave frequencies. The microwave conductivity was taken of two laser ablated YBa2Cu3O(7-delta) thin films on LaAlO3 with transition temperatures of approximately 86.3 and 82 K, respectively, in the temperature range 25 to 300 K. From the conductivity values, the penetration depth was found to be approximately 0.54 and 0.43 micron, and the surface resistance (R sub s) to be approximately 24 and 36 micro-Ohms at 36 GHz and 76 K for the two films under consideration. The R sub s values were compared with those obtained from the change in the Q-factor of a 36 GHz Te sub 011-mode (OFHC) copper cavity by replacing one of its end walls with the superconducting sample. This technique allows noninvasive characterization of high transition superconducting thin films at microwave frequencies.

  18. Dynamic investigations on the influence of epitaxial strain on the superconducting transition in YBa{sub 2}Cu{sub 3}O{sub 7-x}

    Energy Technology Data Exchange (ETDEWEB)

    Huehne, R; Okai, D; Doerr, K; Trommler, S; Herklotz, A; Holzapfel, B; Schultz, L [IFW Dresden, Institute for Metallic Materials, PO Box 270116, D-01171 Dresden (Germany)], E-mail: r.huehne@ifw-dresden.de

    2008-07-15

    YBa{sub 2}Cu{sub 3}O{sub 7-x} (YBCO) films have been prepared on piezoelectric (001) Pb(Mg{sub 1/3}Nb{sub 2/3}){sub 0.72}Ti{sub 0.28}O{sub 3} (PMN-PT) substrates for dynamic investigations on the influence of strain on the superconducting transition temperature. The YBCO films deposited by off-axis pulsed laser deposition showed a perfect epitaxial growth on the piezocrystals but also significant surface roughness due to the miscut of the substrate. The in-plane lattice constant of the PMN-PT substrate was varied dynamically by the application of an electric field of {<=}10 kV cm{sup -1}. As a result, a reversible shift of the superconducting transition by about 0.1 K was found on an optimally doped YBCO film for an applied strain of 0.05%. The results show for the first time that this approach is suitable for studying the strain dependence of superconducting properties in detail.

  19. Effect of substitution of Ce on superconducting properties of Bi1.7Pb0.3Sr2Ca2-CeCu3O10+ system

    Indian Academy of Sciences (India)

    R R Kothawale; B N Dole; S S Shah

    2002-05-01

    We have investigated the superconducting properties of the Bi1.7Pb0.3Sr2Ca2-CeCu3O10+ system with = 0.00, 0.02, 0.04, 0.08 and 0.1 by X-ray diffraction and magnetic susceptibility. The substitution of Ce for Ca has been found to drastically change the superconducting properties of the system. X-ray diffraction studies on these compounds indicate decrease in the -parameter with increased substitution of Ce at Ca site and volume fraction of high c(2 : 2 : 2 : 3) phase decreases and low c phase increases. The magnetic susceptibility of this compound shows that the diamagnetic on set superconducting transition temperature (onset) varies from 109 K to 51 K for =0.00, 0.02, 0.04, 0.08 and 0.1. These results suggest the possible existence of Ce in a tetravalent state rather than a trivalent state in this system; that is, Ca2+ → Ce4+ replacement changes the hole carrier concentration. Hole filling is the cause of lowering c of the system.

  20. Percolation effect in thick film superconductors: Using a Bi(Pb)SrCaCuO based paste to prepare a superconducting planar transformer

    Science.gov (United States)

    Sali, Robert; Harsanyi, Gabor

    1995-01-01

    A thick film superconductor paste has been developed to study the properties of granulated superconductor materials, to observe the percolation effect and to confirm the theory of the conducting mechanism in the superconducting thick films. This paste was also applied to make a superconducting planar transformer. Due to the T(sub c) and advantageous current density properties the base of the past was chosen to be of Bi(Pb)SrCaCu) system. For contacts a conventional Ag/Pt paste was used. The critical temperature of the samples were between 110 K and 115 K depending on the printed layer thickness. The critical current density -at the boiling temperature of the liquid He- was between 200 - 300 A/sq cm. The R(T) and V(I) functions were measured with different parameters. The results of the measurements have confirmed the theory of conducting mechanism in the material. The percolation structure model has been built and described. As an application, a superconducting planar thick film transformer was planned and produced. Ten windings of the transformer were printed on one side of the alumina substrate and one winding was printed on the other side. The coupling between the two sides was possible through the substrate. The samples did not need special drying and firing parameters. After the preparation, the properties of the transformer were measured. The efficiency ans the losses were determined. Finally, some fundamental advantages and problems of the process were discussed.

  1. A new behaviour of ac losses in superconducting Bi(2)Sr(2)CaCu(2)O(8) single crystals.

    Science.gov (United States)

    Chockalingam, S P; Sarangi, S; Bhat, S V; Oka, K; Nishihara, Y

    2009-01-28

    A new ac loss behaviour is observed in the superconducting state of Bi(2)Sr(2)CaCu(2)O(8) single crystals using a novel technique of measuring dissipation at radio frequencies. It is found that the ac loss in the superconducting state is larger than that in the normal state. This counter-intuitive result is explained in terms of the cumulative effect of repetitive decoupling of intrinsic Josephson junctions in the crystals and analysed in the framework of Ambegaokar-Baratoff theory. The ac losses are studied as a function of temperature, rf amplitude and magnetic field applied at different orientations. A peak in ac losses is observed in the superconducting state along the temperature scale. The amplitude of the peak decreases and shifts towards lower temperature with increasing field and also when the field orientation with respect to the c axis of the crystal changes from the perpendicular to parallel direction. The origin of the peak and its behaviour are discussed in the context of coupling energy of Josephson junctions present in the sample. In the presence of a magnetic field another peak in ac losses arises at temperatures close to T(c), which is associated with the Lorentz-force-driven motion of vortices.

  2. High Critical Current Density of YBa2Cu3O7-x Superconducting Films Prepared through a DUV-assisted Solution Deposition Process.

    Science.gov (United States)

    Chen, Yuanqing; Bian, Weibai; Huang, Wenhuan; Tang, Xinni; Zhao, Gaoyang; Li, Lingwei; Li, Na; Huo, Wen; Jia, Jiqiang; You, Caiyin

    2016-12-01

    Although the solution deposition of YBa2Cu3O7-x (YBCO) superconducting films is cost effective and capable of large-scale production, further improvements in their superconductivity are necessary. In this study, a deep UV (DUV) irradiation technique combined with a low-fluorine solution process was developed to prepare YBCO films. An acrylic acidic group as the chelating agent was used in the precursor solution. The acrylic acidic group was highly sensitive to DUV light at 254 nm and significantly absorbed UV light. The coated gel films exposed to DUV light decomposed at 150 °C and copper aggregation was prevented. The UV irradiation promoted the removal of the carbon residue and other by-products in the films, increased the density and enhanced the crystallinity and superconductivity of the YBCO films. Using a solution with F/Ba = 2, YBCO films with thicknesses of 260 nm and enhanced critical current densities of nearly 8 MA/cm(2) were produced on the LaAlO3 (LAO) substrates.

  3. High Critical Current Density of YBa2Cu3O7‑x Superconducting Films Prepared through a DUV-assisted Solution Deposition Process

    Science.gov (United States)

    Chen, Yuanqing; Bian, Weibai; Huang, Wenhuan; Tang, Xinni; Zhao, Gaoyang; Li, Lingwei; Li, Na; Huo, Wen; Jia, Jiqiang; You, Caiyin

    2016-12-01

    Although the solution deposition of YBa2Cu3O7‑x (YBCO) superconducting films is cost effective and capable of large-scale production, further improvements in their superconductivity are necessary. In this study, a deep UV (DUV) irradiation technique combined with a low-fluorine solution process was developed to prepare YBCO films. An acrylic acidic group as the chelating agent was used in the precursor solution. The acrylic acidic group was highly sensitive to DUV light at 254 nm and significantly absorbed UV light. The coated gel films exposed to DUV light decomposed at 150 °C and copper aggregation was prevented. The UV irradiation promoted the removal of the carbon residue and other by-products in the films, increased the density and enhanced the crystallinity and superconductivity of the YBCO films. Using a solution with F/Ba = 2, YBCO films with thicknesses of 260 nm and enhanced critical current densities of nearly 8 MA/cm2 were produced on the LaAlO3 (LAO) substrates.

  4. Determination of surface resistance and magnetic penetration depth of superconducting YBa2Cu3O(7-delta) thin films by microwave power transmission measurements

    Science.gov (United States)

    Bhasin, K. B.; Warner, J. D.; Miranda, F. A.; Gordon, W. L.; Newman, H. S.

    1991-01-01

    A novel waveguide power transmission measurement technique was developed to extract the complex conductivity of superconducting thin films at microwave frequencies. The microwave conductivity was taken of two laser ablated YBa2Cu3O(7-delta) thin films on LaAlO3 with transition temperatures of approximately 86.3 and 82 K, respectively, in the temperature range 25 to 300 K. From the conductivity values, the penetration depth was found to be approximately 0.54 and 0.43 micron, and the surface resistance (R sub s) to be approximately 24 and 36 micro-Ohms at 36 GHz and 76 K for the two films under consideration. The R sub s values were compared with those obtained from the change in the Q-factor of a 36 GHz Te sub 011-mode (OFHC) copper cavity by replacing one of its end walls with the superconducting sample. This technique allows noninvasive characterization of high transition superconducting thin films at microwave frequencies.

  5. Selective oxidation of cyclohexane on a novel catalyst Mg-Cu/SBA-15 by molecular oxygen.

    Science.gov (United States)

    Duan, Xiaogang; Liu, Weimin; Yue, Lumin; Fu, Wei; Ha, Minh Ngoc; Li, Jun; Lu, Guanzhong

    2015-10-21

    The novel catalysts xMg-2.3Cu/SBA-15 with copper and magnesium oxide co-supported on mesoporous silica were synthesized by an impregnation method. The newly synthesized catalysts were characterized using a series of techniques such as BET, XRD, H2-TPR, UV-vis, XPS, EDS and TEM. The catalytic performance was evaluated by using selective oxidation of cyclohexane with molecular oxygen as the oxidant in a solvent free system. The incorporation of magnesium improved the dispersion of copper oxide and prevented the deep oxidation of cyclohexanol and cyclohexanone. The selectivity of K/A oil was up to 99.3% with 12% conversion of cyclohexane over the 1.2Mg-2.3Cu/SBA-15 catalyst. To our knowledge, this is the best result for the heterogeneous oxidation of cyclohexane by O2.

  6. Analysis of the structure, configuration, and sizing of Cu and Cu oxide nanoparticles generated by fs laser ablation of solid target in liquids

    Energy Technology Data Exchange (ETDEWEB)

    Santillan, J. M. J. [Centro de Investigaciones Opticas (CIOp), (CONICET La Plata - CIC) (Argentina); Videla, F. A.; Schinca, D. C.; Scaffardi, L. B. [Centro de Investigaciones Opticas (CIOp), (CONICET La Plata - CIC) (Argentina); Departamento de Ciencias Basicas, Facultad de Ingenieria, UNLP (Argentina); Fernandez van Raap, M. B. [Departamento de Fisica-IFLP, Universidad Nacional de La Plata-CONICET, L. B. Scaffardi: CIOp CC3 (1897) Gonnet, La Plata (Argentina)

    2013-04-07

    We report on the analysis of structure, configuration, and sizing of Cu and Cu oxide nanoparticles (Nps) produced by femtosecond (fs) laser ablation of solid copper target in liquids. Laser pulse energy ranged between 500 {mu}J and 50 {mu}J. Water and acetone were used to produce the colloidal suspensions. The study was performed through optical extinction spectroscopy using Mie theory to fit the full experimental spectra, considering free and bound electrons size dependent contributions to the metal dielectric function. Raman spectroscopy and AFM technique were also used to characterize the sample. Considering the possible oxidation of copper during the fabrication process, two species (Cu and Cu{sub 2}O) arranged in two structures (bare core or core-shell) and in two configuration types (Cu-Cu{sub 2}O or Cu{sub 2}O-Cu) were considered for the fitting depending on the laser pulse energy and the surrounding media. For water at high energy, it can be observed that a Cu-Cu{sub 2}O configuration fits the experimental spectra of the colloidal suspension, while for decreasing energy and below a certain threshold, a Cu{sub 2}O-Cu configuration needs to be included for the optimum fit. Both species coexist for energies below 170 {mu}J for water. On the other hand, for acetone at high energy, optimum fit of the full spectrum suggests the presence a bimodal Cu-Cu{sub 2}O core-shell Nps distribution while for decreasing energy and below a 70 {mu}J threshold energy value, Cu{sub 2}O-Cu core-shell Nps must be included, together with the former configuration, for the fit of the full spectrum. We discuss possible reasons for the changes in the structural configuration of the core-shell Nps.

  7. Exploration of Anomalous Gravity Effects by rf-Pumped Magnetized High-T(c) Superconducting Oxides

    Science.gov (United States)

    Robertson, Tony; Litchford, Ron; Peters, Randall; Thompson, Byran; Rodgers, Stephen L. (Technical Monitor)

    2001-01-01

    A number of anomalous gravitational effects have been reported in the scientific literature during recent years, but there has been no independent confirmation with regard to any of these claims. Therefore, the NASA Marshall Space Flight Center, in response to the propulsion challenges specified by NASA's Breakthrough Propulsion Physics (BPP) program, proposed to explore the possibility of observing anomalous gravitation behavior through the manipulation of Josephson junction effects in magnetized high-Tc superconducting oxides. The technical goal was to critically test this revolutionary physical claim and provide a rigorous, independent, empirical confirmation (or refutation) of anomalous effects related to the manipulation of gravity by radio frequency (rf)-pumped magnetized type-2 superconductors. Because the current empirical evidence for gravity modification is anecdotal, our objective was to design, construct, and meticulously implement a discriminating experiment, which would put these observations on a more firm footing within the scientific community. Our approach is unique in that we advocate the construction of an extremely sensitive torsion balance with which to measure gravity modification effects by rf-pumped type-2 superconductor test masses. This paper reviews the anecdotal evidence for anomalous gravity effects, describes the design and development of a simplified torsion balance experiment for empirically investigating these claims, and presents the results of preliminary experiments.

  8. Phase Diagram and Electronic Properties of High-Tc Superconducting Oxides

    Science.gov (United States)

    Pavuna, Davor

    We firstly briefly summarize some of the most relevant recent results and open questions across rather complex electronic phase diagram of cuprates. We continue with a discussion of results on thin superconducting oxide films grown by laser ablation. Systematic studies show that BSCCO-phases and LSCO-214 exhibit conductor-like Fermi edge, whereas materials containing "chains" (like YBCO-123) are prone to very rapid surface degradation, most likely related to critical oxygen loss at the outermost layers. Recently, direct ARPES dispersion measurements on in-situ grown, strained 10UC thin LSCO-214 films (Tc = 44 K) have shown the band crossing of Fermi level well before the Brillouin zone boundary. This is in contrast to the flat band observed in unstrained single crystals — and to the band flattening predicted by band calculations for in-plane compressive strain. In spite of density of states reduction near the Fermi level, the critical temperature increases in strained films with respect to unstrained crystals; this poses further challenge to HTSC theory.

  9. Fractal-based modeling of the stress-strain relation of Bi2Sr2CaCu2Ox/AgMg superconducting round wires

    Science.gov (United States)

    Gou, Xiaofan; Schwartz, Justin

    2013-10-01

    Bi2Sr2CaCu2Ox/AgMg (Bi2212) multi filamentary superconducting round wires (RWs) can be only potential candidate for constructing the superconducting magnet with higher magnetic field (>25T). Very complicated microstructure of Bi2212 RWs has been found by recent SEM studies, and then the vital problems of Characterization of this unique microstructure and further exploration of the correlation of macro electromechanical properties with this microstructure arise. In this paper, it is firstly found that the rough surface of individual filaments can be well characterized by fractals. On the geometrical model with the fractal simulation of the rough surface, stress-strain relation of Bi2212 RWs has been investigated. The modelling result with considering the rough surface has a better agreement to the experimental data. At the request of the authors, and with the agreement of the Proceedings Editor, the above paper in AIP Proceedings has been retracted (as of 26 November 2013) due to a prior publication by the authors which reports similar data/results. That paper was first published in volume 26 (issue 5) of the journal Superconductor Science and Technology and was published on 4 April 2013: Fractal analysis of the role of the rough interface between Bi2Sr2CaCu2Ox filaments and the Ag matrix in the mechanical behavior of composite round wires The authors wish to apologize for any inconvenience caused by publication of their AIP Proceedings article.

  10. Fabrication of full high-T sub c superconducting YBa sub 2 Cu sub 3 O sub 7 sub - sub x trilayer junctions using a polishing technique

    CERN Document Server

    Kuroda, K; Takami, T; Ozeki, T

    2003-01-01

    We have successfully fabricated full high-T sub c superconducting YBa sub 2 Cu sub 3 O sub 7 sub - sub x (YBCO)/PrBa sub 2 Cu sub 3 O sub 7 sub - sub x (PBCO)/YBCO trilayer junctions, which have a simple device structure, such as a Pb-alloy-based Josephson tunneling junction. It has been demonstrated that a polishing technique is extremely useful in the fabrication process: it is effective in smoothing a coarse surface and gentling the slopes of the edges, or decreasing the slope angles. Owing to the polishing technique, the PBCO barrier layer and the upper YBCO layer have been notably thinned: the thicknesses of these layers are 10 nm and 250 nm, respectively. Junctions with the dimensions of 5 mu m x 5 mu m showed resistively shunted junction-like current-voltage curves with a typical critical current density of 110 A/cm sup 2 at 4.2 K. Furthermore, the operation of superconducting quantum interference devices has been demonstrated. (author)

  11. Charge transfer polarisation wave in high Tc oxides and superconductive pairing

    Science.gov (United States)

    Chakraverty, B. K.

    1991-01-01

    A general formalism of quantized charge transfer polarization waves was developed. The nature of possible superconductive pairing between oxygen holes is discussed. Unlike optical phonons, these polarization fields will give rise to dielectric bipolarons or bipolaron bubbles. In the weak coupling limit, a new class of superconductivity is to be expected.

  12. Hysteresis and relaxation in TlBa{sub 2}Ca{sub 2}Cu{sub 3}O{sub y} superconducting polycrystals

    Energy Technology Data Exchange (ETDEWEB)

    Batista-Leyva, A J [Physics Department, Engineering Faculty, University of Holguin, Holguin 80100 (Cuba); Cobas, R [Superconductivity Laboratory, IMRE-Physics Faculty, University of Havana, 10400 Havana (Cuba); Orlando, M T D [Physics Department, Universidade Federal do Espiritu Santo, Vitoria ES 29060-900 (Brazil); Altshuler, E [Superconductivity Laboratory, IMRE-Physics Faculty, University of Havana, 10400 Havana (Cuba)

    2003-08-01

    We study the hysteresis and relaxation of both intragranular and intergranular properties of TlBa{sub 2}Ca{sub 2}Cu{sub 3}O{sub y} (Tl-1223) superconducting polycrystals between 80 and 120 K. The samples have been prepared using a technique involving the mixing of grains of different sizes before the final sintering. The grains show a sizeable reversible magnetization, while vortices inside the grain behave as three-dimensional objects. The transport critical current is strongly hysteretic, with features that distinguish our Tl-1223 samples from 'standard' YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO), (Hg, Re)Ba{sub 2}Ca{sub 2}Cu{sub 3}O{sub 8+{delta}} (HBCCO) and (Bi, Pb){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10-{delta}} (BSCCO) polycrystals. The preparation method improves the transport properties of the samples. The relaxation of the transport critical current density, in the presence of trapped fields, is reported here for the first time in this system, as far as we know. A phenomenological model can qualitatively describe the transport properties, where the intragrain magnetization affects the intergranular junctions, but a precise quantitative description is not achieved. The differences in the shape of the transport measurements, for different polycrystalline systems, are also well described by the model.

  13. Mechanism of metallization and superconductivity suppression in YBa2(Cu0.97 Zn0.03)3 O6.92 revealed by 67Zn NQR

    Science.gov (United States)

    Pelc, D.; Požek, M.; Despoja, V.; Sunko, D. K.

    2015-08-01

    We measure the nuclear quadrupole resonance signal on the Zn site in nearly optimally doped YBa2Cu3O6.92, when Cu is substituted by 3% of isotopically pure 67Zn. We observe that Zn creates large insulating islands, confirming two earlier conjectures: that doping provokes an orbital transition in the CuO2 plane, which is locally reversed by Zn substitution, and that the islands are antiferromagnetic. Also, we find that the Zn impurity locally induces a breaking of the D4 symmetry. Cluster and DFT calculations show that the D4 symmetry breaking is due to the same partial lifting of degeneracy of the nearest-neighbor oxygen sites as in the LTT transition in {La}{}2-xBaxCuO4, similarly well-known to strongly suppress superconductivity (SC). These results show that in-plane oxygen 2p5 orbital configurations are principally involved in the metallicity and SC of all high-Tc cuprates, and provide a qualitative symmetry-based constraint on the SC mechanism.

  14. Charge density wave fluctuations in La{sub 2-x}Sr{sub x}CuO{sub 4} and their competition with superconductivity

    Energy Technology Data Exchange (ETDEWEB)

    Croft, Thomas; Lester, Christopher; Hayden, Stephen [H.H. Wills Physics Laboratory, University of Bristol (United Kingdom); Bombardi, Alessandro; Senn, Mark [Diamond Light Source Ltd., Harwell Science and Innovation Campus, Didcot, Oxfordshire (United Kingdom)

    2015-07-01

    The recent observations of charge and stripe correlations in YBa{sub 2}Cu{sub 3}O{sub 6+x} and La{sub 2-x}Ba{sub x}CuO{sub 4} has reinvigorated interest in their role in influencing the superconductivity of the cuprates. However, structural complications of these systems makes it difficult to isolate the effect the lattice has in inducing the charge order. Here, we report hard X-ray diffraction measurements on three compositions (x=0.11,0.12,0.13) of the high-temperature superconductor La{sub 2-x}Sr{sub x}CuO{sub 4}, a canonical example of HTS with T{sub c} ∼ 35 K and a simple crystal structure. All samples show charge-density-wave (CDW) order with onset temperatures in the range 51-80 K and ordering wavevectors close to (0.23,0,0.5). We present a phase diagram of La{sub 2-x}Sr{sub x}CuO{sub 4} including the pseudogap phase, CDW and magnetic order.

  15. Mixed oxide semiconductor CuInAlO4 nanoparticles: synthesis, structure and photocatalytic properties

    Science.gov (United States)

    Xu, Jian; Qin, Chuanxiang; Bi, Shala; Wan, Yingpeng; Huang, Yanlin; Wang, Yaorong; Seo, Hyo Jin

    2017-01-01

    CuInAlO4 nanoparticles were synthesized via the facile sol-gel route. The phase formations were investigated by x-ray powder diffraction and structure refinements. The morphological characteristic of the nano-oxides was tested with scanning electron microscopy, transmission electron microscopy, energy-dispersive spectra, N2-adsorption-desorption isotherms and the x-ray photoelectron spectrum. The optical absorption, band energy and structures of the nanoparticles were measured. CuInAlO4 has wide optical absorption from UV to visible wavelength. The nano-oxides have a narrow band energy of 2.191 eV. The photocatalysis ability of CuInAlO4 nanoparticles was confirmed by its efficient photodegradation on methylene blue (MB) dye under the excitation of the visible wavelengths: CuInAlO4 demonstrates efficient photocatalysis on MB photodegradation.

  16. Cyclic Oxidation Behavior of CuCrAl Cold-Sprayed Coatings for Reusable Launch Vehicles

    Science.gov (United States)

    Raj, Sai; Karthikeyan, J.

    2009-01-01

    The next generation of reusable launch vehicles is likely to use GRCop-84 [Cu-8(at.%)Cr-4%Nb] copper alloy combustion liners. The application of protective coatings on GRCop-84 liners can minimize or eliminate many of the environmental problems experienced by uncoated liners and significantly extend their operational lives and lower operational cost. A newly developed Cu- 23 (wt.%) Cr-5% Al (CuCrAl) coating, shown to resist hydrogen attack and oxidation in an as-cast form, is currently being considered as a protective coating for GRCop-84. The coating was deposited on GRCop-84 substrates by the cold spray deposition technique, where the CuCrAl was procured as gas-atomized powders. Cyclic oxidation tests were conducted between 773 and 1,073 K to characterize the coated substrates.

  17. Oxidation of two ternary Fe-Cu-5Al alloys in 1×105 Pa pure oxygen at 700 ℃

    Institute of Scientific and Technical Information of China (English)

    XIANG Jun-huai; NIU Yan; WU Wei-tao; LIU Guo-dong

    2006-01-01

    The oxidation of two two-phase ternary Fe-Cu-Al alloys containing about 5% Al(mole fraction),one Fe-rich and one Cu-rich,were studied at 700 ℃ in 1×105 Pa pure oxygen. The Fe-rich alloy (Fe-15Cu-5Al) shows two quasi-parabolic stages,with a large increase of the parabolic rate constant after about 4 h. The presence of 5% Al does not change greatly the oxidation rate of Fe-15Cu-5Al with respect to a binary Fe-Cu alloy of similar composition,which was quite different from the situation of the same alloys oxidized at 800 ℃. Oxidation of Fe-15Cu-5Al at 700 ℃ produced an outer layer of iron oxides and an inner layer containing a mixture of copper metal,iron and aluminium oxide. On the contrary,the Cu-rich Fe-85Cu-5Al alloy presents a rather irregular kinetic behavior,with formation of an inner continuous alumina thin layer and a rather irregular outer layer. The outer layer with a rather irregular thickness was mainly composed of a matrix of copper oxides plus some aluminium and iron oxides presenting in the deep part of the layer at certain locations. As a result of the formation of a protective alumina layer,the presence of 5% Al greatly reduced the oxidation rate of Fe-85Cu-5Al with respect to a binary Fe-Cu alloy of similar composition,which was also quite different from the situation of the same alloys oxidized at 800 ℃. Moreover,the oxidation rate at 700 ℃ of the Fe-85Cu-5Al alloy was much lower than that of Fe-15Cu-5Al alloy due to the same reason..

  18. Study of superconducting a-axis oriented YBa 2Cu 3O 7-δ thin films deposited on Y 2O 3/YSZ/Si with PrBa 2Cu 3O 7-δ seed layer

    Science.gov (United States)

    Rosova, Alica; Chromik, Stefan; Benacka, Stefan; Wuyts, Bart

    1995-02-01

    Epitaxial a-axis oriented YBa 2Cu 3O 7-δ (YBCO) superconducting thin films have been grown by off-axis magnetron sputtering on Y 2O 3/YSZ/Si substrates with PrBa 2Cu 3O 7-δ (PBCO) seed layer. The YBCO thin films were deposited immediately after the on-axis magnetron sputtering of PBCO. XRD analyses show that the a-axis volume fraction for 120 nm thick YBCO films varies with substrate temperature during PBCO deposition and its maximum value is higher than 98%. The TEM study shows the clear dependence between the character of the R- T dependence and the microstructure of our YBCO thin films, which varies with the change of the volume ratio of a-axis to c-maxis oriented YBCO.

  19. Superconductivity and mechanical properties of SmBa2Cu3O7-δ added with nano-crystalline ZnFe2O4

    Science.gov (United States)

    Abdeen, W.; El Tahan, A.; Awad, R.; Abou Aly, A. I.; El-Maghraby, E. M.; Khalaf, A.

    2016-06-01

    The effect of nanosized ZnFe2O4 addition on the physical properties of polycrystalline SmBa2Cu3O7-δ superconductor was studied. Superconducting samples of the type (ZnFe2O4) x SmBa2Cu3O7-δ, x = 0.00, 0.01, 0.02, 0.04, 0.06, 0.08, 0.10, 0.15 and 0.20 wt% were prepared by the solid-state reaction method. The characterization and superconductivity investigation were carried out using X-ray powder diffraction, XRD, scanning electron microscope, SEM, energy-dispersive X-ray, EDX, dc electrical resistivity and transport critical current density at 77 K. Improvements in the volume fraction, superconducting transition temperature, Tc, and transport critical current density, Jc, were observed as x increased from 0.00 up to 0.08 wt% and then they decreased with further increase in nanosized ZnFe2O4 addition. The Vickers microhardness number, H v, and elastic parameters have been measured at room temperature. The ultrasonic pulse-echo technique at 4 MHz was used to determine the elastic parameters. H v and the elastic parameters were observed to increase with increasing x. The enhancement of the elastic parameters may be due to the hindrance of dislocation motion with nanosized ZnFe2O4 addition. Moreover, Debye temperatures ( θ D) were calculated and it was found that their values increased with increasing nanosized ZnFe2O4 addition. The elastic parameters of the samples were computed and corrected to zero porosity using different models. Finally, the relationship between Young's modulus and H v was estimated for different models.

  20. A study on the superconducting properties of YBa{sub 2}Cu{sub 9-x}Nb{sub x}O{sup y} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Srinivas, S.; Bhatnagar, A.K. [Univ. of Hyderabad (India); Pinto, R. [Solid State Electronics Group, Bombay (India)] [and others

    1994-12-31

    Effect of niobium substitution at the copper site in YBa{sub 2}Cu{sub 9}O{sub 7-x} was studied in thin film form. The films were deposited by laser ablation technique using the targets of the YBa{sub 2}Cu{sub 3-x}Nb{sub x}O{sub y} where x = 0.0, 0.025, 0.05, 0.1, 0.2, 0.4, 0.8 and 1.0 under identical deposition conditions on SrTiO{sub 9} <100> substrates. Films were characterized by XRD, resistivity, I-V and J{sub c} measurements. Films made from x = 0.025 and 0.05 concentrations of Nb substituted targets showed relatively improved superconducting properties compared to that of undoped films. The best 7 realized for x = 0.025 Nb concentration was 1.8 x 10{sup {sigma}} A/cm{sup 2} and for 0.05 Nb concentration it was 3.2x10{sup {sigma}} A/cm{sup 2} at 77K. However, degradation of the superconducting properties, with the increase of x {ge} 0.1 Nb concentration and drastic suppression and complete loss of superconductivity was noticed for x {ge} 0.4. The growth of impurity phase YBa{sub 2}NbO{sub 6} for x = 0.1 and above of Nb concentration was noticed from XRD patterns. However, the site occupancy of Nb could not be confirmed from these studies.

  1. EPR and speciation simulation study of Cu2+ complexes in an amine-based aqueous precursor system used for preparation of superconducting YBCO coatings.

    Science.gov (United States)

    Lommens, Petra; Feys, Jonas; Vrielinck, Henk; De Buysser, Klaartje; Herman, Gerrit; Callens, Freddy; Van Driessche, Isabel

    2012-03-28

    In this work, we investigate the chemistry for an aqueous acetate-triethanolamine-ammonia based YBa(2)Cu(3)O(7-δ) (YBCO) precursor system. These precursor solutions are suited for the chemical solution deposition of superconducting YBCO layers on top of single crystal SrTiO(3) or buffered NiW tapes. The development of this kind of precursor inks often involves trial-and-error experimenting and thus is very time-consuming. To reduce labwork to the minimum, the theoretical prediction of pH stability limits and the complexation behaviour of the different metal ions and complexants in the inks are very important. For this purpose, we simulated, based on literature values, the complexation behaviour of Cu(2+) in the aqueous precursor solutions as a function of pH. To validate the used model, we performed potentiometric pH titrations for solutions with similar composition and checked the correctness of fit between experiment and model. The generated complexometric results are coupled with X-band EPR spectra to further confirm the results. EPR spectra for fully prepared precursor solutions as well as for Cu(2+) reference solutions containing only one type of ligand (acetate, triethanolamine or ammonia) were investigated as a function of pH. We find that, in line with speciation simulation, only acetates are actively complexing the Cu(2+) ions at pH values below 7, while when reaching higher pH levels mainly triethanolamine complexes are formed. Over the entire pH range, no trace of free Cu(2+)or Cu(OH)(2), possibly creating precipitation during gelation and thus complicating further processing, could be found.

  2. Stripe order in superconducting La2-xBaxCuO4 (0.095 < x < 0.155)

    Energy Technology Data Exchange (ETDEWEB)

    Hucker, Markus [Brookhaven National Lab. (BNL), Upton, NY (United States); v. Zimmermann, Martin [Hamburger Synchrotronstrahlungslabor, Hamburg (Germany); Gu, Genda D. [Brookhaven National Lab. (BNL), Upton, NY (United States); Xu, Z. J. [Brookhaven National Lab. (BNL), Upton, NY (United States); Wen, J. S. [Brookhaven National Lab. (BNL), Upton, NY (United States); Xu, Guangyong [Brookhaven National Lab. (BNL), Upton, NY (United States); Kang, H. J. [National Inst. of Standards and Technology, Gaithersburg, MD (United States); Zheludev, A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Tranquada, John M. [Brookhaven National Lab. (BNL), Upton, NY (United States)

    2011-03-17

    The correlations between stripe order, superconductivity, and crystal structure in La2-x Bax CuO4 single crystals have been studied by means of x-ray and neutron diffraction as well as static magnetization measurements. The derived phase diagram shows that charge stripe order (CO) coexists with bulk superconductivity in a broad range of doping around x=1/8 , although the CO order parameter and correlation length fall off quickly for x≠1/8 . Except for x=0.155 , the onset of CO always coincides with the transition between the orthorhombic and the tetragonal or less orthorhombic low-temperature structures. The CO transition evolves from a sharp drop at low x to a more gradual transition at higher x , eventually falling below the structural phase boundary for optimum doping. With respect to the interlayer CO correlations, we find no qualitative change of the stripe stacking order as a function of doping, and in-plane and out-of-plane correlations disappear simultaneously at the transition. Similarly to the CO, the spin stripe order (SO) is also most pronounced at x=1/8 . Truly static SO sets in below the CO and coincides with the first appearance of in-plane superconducting correlations at temperatures significantly above the bulk transition to superconductivity (SC). Indications that bulk SC causes a reduction of the spin or charge stripe order could not be identified. We argue that CO is the dominant order that is compatible with SC pairing but competes with SC phase coherence. Comparing our results with data from the literature, we find good agreement if all results are plotted as a function of x' instead of the nominal x , where x' represents an estimate of the actual Ba content, extracted from the doping dependence of the structural transition between the orthorhombic phase and the tetragonal high-temperature phase.

  3. Stripe order in superconducting La2-xBaxCuO4 (0.095⩽x⩽0.155)

    Science.gov (United States)

    Hücker, M.; v. Zimmermann, M.; Gu, G. D.; Xu, Z. J.; Wen, J. S.; Xu, Guangyong; Kang, H. J.; Zheludev, A.; Tranquada, J. M.

    2011-03-01

    The correlations between stripe order, superconductivity, and crystal structure in La2-xBaxCuO4 single crystals have been studied by means of x-ray and neutron diffraction as well as static magnetization measurements. The derived phase diagram shows that charge stripe order (CO) coexists with bulk superconductivity in a broad range of doping around x=1/8, although the CO order parameter and correlation length fall off quickly for x≠1/8. Except for x=0.155, the onset of CO always coincides with the transition between the orthorhombic and the tetragonal or less orthorhombic low-temperature structures. The CO transition evolves from a sharp drop at low x to a more gradual transition at higher x, eventually falling below the structural phase boundary for optimum doping. With respect to the interlayer CO correlations, we find no qualitative change of the stripe stacking order as a function of doping, and in-plane and out-of-plane correlations disappear simultaneously at the transition. Similarly to the CO, the spin stripe order (SO) is also most pronounced at x=1/8. Truly static SO sets in below the CO and coincides with the first appearance of in-plane superconducting correlations at temperatures significantly above the bulk transition to superconductivity (SC). Indications that bulk SC causes a reduction of the spin or charge stripe order could not be identified. We argue that CO is the dominant order that is compatible with SC pairing but competes with SC phase coherence. Comparing our results with data from the literature, we find good agreement if all results are plotted as a function of x' instead of the nominal x, where x' represents an estimate of the actual Ba content, extracted from the doping dependence of the structural transition between the orthorhombic phase and the tetragonal high-temperature phase.

  4. Cu2+-Catalyzed Oscillatory Oxidation of Ascorbic Acid by O2 Flow

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A novel heterogeneous oscillator, the Cu2+-catalyzed oscillatory oxidation of ascorbic acid (Vitamin C) in aqueous solution by O2 flow was reported. Both the potential oscillations on Pt-electrode corresponding to [Cu2+] and the absorbance oscillations at l=260 nm corresponding to [ascorbic acid] were observed. Oscillations in the completely homogeneous system were also observed. Effects of several factors on the oscillations were investigated.

  5. Superconducting properties of the Fe-substituted La 2.5Y 0.5CaBa 3(Cu 1- xFe x) 7O z perovskite

    Science.gov (United States)

    Subbarao, M. V.; Kuberkar, D. G.; Kulkarni, R. G.

    1999-02-01

    The structural and superconducting properties of single-phase Fe-substituted La 2.5Y 0.5CaBa 3(Cu 1- xFe x) 7O z [LYCBCuFe] with 0≤ x≤0.15 compounds having triple-perovskite structure are investigated using X-ray diffraction, resistivity, AC Susceptibility, oxygen content and Mössbauer effect measurements. The observed reduction of Tc with increasing x in LYCBCuFe supports the view that magnetic pair breaking by local moments contributes predominantly to the suppression of superconductivity by Fe. The observed Fe-dopant site occupancies and the Cu(2) plane to the Cu(1) chain site ratio in the LYCBCuFe obtained from Mössbauer spectral analysis of x=0.02 sample are quite different from those of the usual Fe-doped YBa 2Cu 3O z.

  6. Superconducting Josephson vortex flow transistors

    CERN Document Server

    Tavares, P A C

    2002-01-01

    The work reported in this thesis focuses on the development of high-temperature superconducting Josephson vortex-flow transistors (JVFTs). The JVFT is a particular type of superconducting transistor, i.e. an electromagnetic device capable of delivering gain while keeping the control and output circuits electrically isolated. Devices were fabricated from (100) YBa sub 2 Cu sub 3 O sub 7 sub - subdelta thin films grown by Pulsed Laser Deposition on 24 deg magnesium oxide and strontium titanate bicrystals. The design of the JVFTs was guided by numerical simulations and the devices were optimised for current gain. Improvements were made to the fabrication process in order to accurately pattern the small structures required. The devices exhibited current gains higher than 60 in liquid nitrogen. Gains measured at lower temperatures were significantly higher. As part of the work a data acquisition suite was developed for the characterisation of three-terminal devices and, in particular, of JVFTs.

  7. Duplex Oxide Formation during Transient Oxidation of Cu-5%Ni(001) Investigated by In situ UHV-TEM and XPS

    Energy Technology Data Exchange (ETDEWEB)

    Yang, J.C.; Starr, D.; Kang, Y.; Luo, L.; Tong, X.; Zhou, G.

    2012-05-20

    The transient oxidation stage of a model metal alloy thin film was characterized with in situ ultra-high vacuum (UHV) transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and analytic high-resolution TEM. We observed the formations of nanosized NiO and Cu{sub 2}O islands when Cu-5a5%Ni(100) was exposed to oxygen partial pressure, pO{sub 2} = 1 x 10{sup -4} Torr and various temperatures in situ. At 350 C epitaxial Cu{sub 2}O islands formed initially and then NiO islands appeared on the surface of the Cu{sub 2}O island, whereas at 750 C NiO appeared first. XPS and TEM was used to reveal a sequential formation of NiO and then Cu{sub 2}O islands at 550 C. The temperature-dependant oxide selection may be due to an increase of the diffusivity of Ni in Cu with increasing temperature.

  8. Au@Cu(II)-MOF: Highly Efficient Bifunctional Heterogeneous Catalyst for Successive Oxidation-Condensation Reactions.

    Science.gov (United States)

    Wang, Jing-Si; Jin, Fa-Zheng; Ma, Hui-Chao; Li, Xiao-Bo; Liu, Ming-Yang; Kan, Jing-Lan; Chen, Gong-Jun; Dong, Yu-Bin

    2016-07-05

    A new composite Au@Cu(II)-MOF catalyst has been synthesized via solution impregnation and full characterized by HRTEM, SEM-EDS, XRD, gas adsorption-desorption, XPS, and ICP analysis. It has been shown here that the Cu(II)-framework can be a useful platform to stabilize and support gold nanoparticles (Au NPs). The obtained Au@Cu(II)-MOF exhibits a bifunctional catalytic behavior and is able to promote selective aerobic benzyl alcohol oxidation-Knoevenagel condensation in a stepwise way.

  9. Separation of Arsenic from the Antimony-Bearing Dust through Selective Oxidation Using CuO

    Science.gov (United States)

    Zhong, Da-Peng; Li, Lei; Tan, Cheng

    2017-04-01

    A pyrometallurgical process of selective oxidation roasting of the antimony-bearing dust using CuO is put forward, in which the antimony component is oxidized to Sb2O4 staying in the roasted residue, and arsenic is volatilized in the form of As2O3. The addition of CuO has an active effect on the arsenic volatilization, because structures of some complicated As-Sb phases in the dust are destroyed after the "Sb" component in them is oxidized to Sb2O4, and this part of arsenic might be transformed to As2O3, which continues to volatilize. However, the arsenic volatilization rate decreases with the CuO amount in a certain range, which is attributed to the greater formation of Cu3 (AsO4)2 and Cu3As. Under the conditions of roasting temperature of 673 K (400 °C), roasting time of 100 minutes, CuO amount of 34.54 mass pct, and N2 flow rate of 30 mL/min, 91.50 pct arsenic and only 8.63 pct antimony go into the smoke.

  10. Preparation of PdCu Alloy Nanocatalysts for Nitrate Hydrogenation and Carbon Monoxide Oxidation

    Directory of Open Access Journals (Sweden)

    Fan Cai

    2016-06-01

    Full Text Available Alloying Pd with Cu is important for catalytic reactions such as denitrification reaction and CO oxidation reaction, but understanding of the catalyst preparation and its correlation with the catalyst’s activity and selectivity remains elusive. Herein, we report the results of investigations of the preparation of PdCu alloy nanocatalysts using different methods and the catalytic properties of the catalysts in catalytic denitrification reaction and CO oxidation reaction. PdCu alloy nanocatalysts were prepared by conventional dry impregnation method and ligand-capping based wet chemical synthesis method, and subsequent thermochemical activation as well. The alloying characteristics depend on the bimetallic composition. PdCu/Al2O3 with a Pd/Cu ratio of 50:50 was shown to exhibit an optimized hydrogenation activity for the catalytic denitrification reaction. The catalytic activity of the PdCu catalysts was shown to be highly dependent on the support, as evidenced by the observation of an enhanced catalytic activity for CO oxidation reaction using TiO2 and CeO2 supports with high oxygen storage capacity. Implications of the results to the refinement of the preparation of the alloy nanocatalysts are also discussed.

  11. Separation of Arsenic from the Antimony-Bearing Dust through Selective Oxidation Using CuO

    Science.gov (United States)

    Zhong, Da-Peng; Li, Lei; Tan, Cheng

    2017-01-01

    A pyrometallurgical process of selective oxidation roasting of the antimony-bearing dust using CuO is put forward, in which the antimony component is oxidized to Sb2O4 staying in the roasted residue, and arsenic is volatilized in the form of As2O3. The addition of CuO has an active effect on the arsenic volatilization, because structures of some complicated As-Sb phases in the dust are destroyed after the "Sb" component in them is oxidized to Sb2O4, and this part of arsenic might be transformed to As2O3, which continues to volatilize. However, the arsenic volatilization rate decreases with the CuO amount in a certain range, which is attributed to the greater formation of Cu3 (AsO4)2 and Cu3As. Under the conditions of roasting temperature of 673 K (400 °C), roasting time of 100 minutes, CuO amount of 34.54 mass pct, and N2 flow rate of 30 mL/min, 91.50 pct arsenic and only 8.63 pct antimony go into the smoke.

  12. Fabrication of Al/AlOx/Al Josephson junctions and superconducting quantum circuits by shadow evaporation and a dynamic oxidation process

    Institute of Scientific and Technical Information of China (English)

    Wu Yu-Lin; Deng Hui; Yu Hai-Feng; Xue Guang-Ming; Tian Ye; Li Jie; Chen Ying-Fei

    2013-01-01

    Besides serving as promising candidates for realizing quantum computing,superconducting quantum circuits are one of a few macroscopic physical systems in which fundamental quantum phenomena can be directly demonstrated and tested,giving rise to a vast field of intensive research work both theoretically and experimentally.In this paper we report our work on the fabrication of superconducting quantum circuits,starting from its building blocks:Al/AlOx/Al Josephson junctions.By using electron beam lithography patterning and shadow evaporation,we have fabricated aluminum Josephson junctions with a controllable critical current density (jc) and wide range of junction sizes from 0.01 μm2 up to 1 μm2.We have carried out systematical studies on the oxidation process in fabricating Al/AlOx/Al Josephson junctions suitable for superconducting flux qubits.Furthermore,we have also fabricated superconducting quantum circuits such as superconducting flux qubits and charge-flux qubits.

  13. Enhancement of convective heat transfer coefficient of ethylene glycol base cuprous oxide (Cu2O) nanofluids

    Science.gov (United States)

    Hassan, Ali; Ramzan, Naveed; Umer, Asim; Ahmad, Ayyaz; Muryam, Hina

    2017-08-01

    The enhancement in the convective heat transfer coefficient of the ethylene glycol (EG) base cuprous oxide (Cu2O) nanofluids were investigated. The nanofluids of different volume concentrations i-e 1%, 2.5% and 4.5% were prepared by the two step method. Cuprous oxide (Cu2O) nanoparticles were ultrasonically stirred for four hours in the ethylene glycol (EG). The experimental study has been performed through circular tube geometry in laminar flow regime at average Reynolds numbers 36, 71 and 116. The constant heat flux Q = 4000 (W/m2) was maintained during this work. Substantial enhancement was observed in the convective heat transfer coefficient of ethylene glycol (EG) base cuprous oxide (Cu2O) nanofluids than the base fluid. The maximum 74% enhancement was observed in convective heat transfer coefficient at 4.5 vol% concentration and Re = 116.

  14. In situ synthesis of Cu{sub 2}O and Cu nanoparticles during the thermal reduction of copper foil-supported graphene oxide

    Energy Technology Data Exchange (ETDEWEB)

    Ortega-Amaya, R., E-mail: ortegaa@cinvestav.mx; Matsumoto, Y. [Centro de Investigación y de Estudios Avanzados del IPN, SEES, Electrical Engineering Department (Mexico); Pérez-Guzmán, M. A. [Centro de Investigación y de Estudios Avanzados del IPN, Nanoscience and Nanotechnology Program (Mexico); Ortega-López, M. [Centro de Investigación y de Estudios Avanzados del IPN, SEES, Electrical Engineering Department (Mexico)

    2015-10-15

    This work describes a novel method to prepare reduced graphene oxide (rGO) sheets decorated with copper oxide and copper nanoparticles, by annealing copper foil-supported graphene oxide (GO) under an Ar atmosphere. The GO reduction level, the predominant Cu or Cu{sub 2}O compound, and the particle size strongly depend on the process temperature. Scanning electron microscopy and X-ray diffraction analysis revealed that rGO–Cu{sub 2}O and rGO–Cu nanocomposites developed on the Cu foil surface at the annealing temperatures of 200–600 and 800–1000 °C range, respectively. Raman spectroscopy corroborates the effective GO reduction.

  15. Combinatorial Investigations of High Temperature CuNb Oxide Phases for Photoelectrochemical Water Splitting.

    Science.gov (United States)

    Skorupska, Katarzyna; Maggard, Paul A; Eichberger, Rainer; Schwarzburg, Klaus; Shahbazi, Paria; Zoellner, Brandon; Parkinson, Bruce A

    2015-12-14

    High-throughput combinatorial methods have been useful in identifying new oxide semiconductors with the potential to be applied to solar water splitting. Most of these techniques have been limited to producing and screening oxide phases formed at temperatures below approximately 550 °C. We report the development of a combinatorial approach to discover and optimize high temperature phases for photoelectrochemical water splitting. As a demonstration material, we chose to produce thin films of high temperature CuNb oxide phases by inkjet printing on two different substrates: fluorine-doped tin oxide and crystalline Si, which required different sample pyrolysis procedures. The selection of pyrolysis parameters, such as temperature/time programs, and the use of oxidizing, nonreactive or reducing atmospheres determines the composition of the thin film materials and their photoelectrochemical performance. XPS, XRD, and SEM analyses were used to determine the composition and oxidation states within the copper niobium oxide phases and to then guide the production of target Cu(1+)Nb(5+)-oxide phases. The charge carrier dynamics of the thin films produced by the inkjet printing are compared with pure CuNbO3 microcrystalline material obtained from inorganic bulk synthesis.

  16. Electrocatalytic activity of Cu2O nanocubes-based electrode for glucose oxidation

    Indian Academy of Sciences (India)

    Sathiyanathan Felix; Pratap Kollu; Bala P C Raghupathy; Soon Kwan Jeong; Andrews Nirmala Grace

    2014-01-01

    A direct electrocatalytic activity of glucose oxidation on cuprous oxide modified glassy carbon electrode is reported. Cu2O nanocubes were synthesized by a simple wet chemical route in the absence of surfactants. Purity, shape and morphology of Cu2O are characterized by XRD, SEM, XPS and DRS-UV. The Cu2O nanocubes-modified glassy carbon electrode (GCE) exhibited high electrocatalytic activity towards glucose oxidation compared with bare GCE electrode. At an applied potential of +0.60V, the Cu2O electrode presented a high sensitivity of 121.7 A/mM. A linear response was obtained from 0 to 500 M, a response time less than 5 s and a detection limit of 38 M (signal/noise=3). The Cu2O nanocubes-modified electrode was stable towards interfering molecules like uric acid (UA), ascorbic acid (AA) and dopamine (DA). In short, a facile chemical preparation process of cuprous oxide nanocubes, and the fabricated modified electrode allow highly sensitive, selective, and fast amperometric sensing of glucose, which is promising for the future development of non-enzymatic glucose sensors.

  17. Possible Nodeless Superconducting Gaps in Bi2Sr2CaCu2O8+δ and YBa2Cu3O7-x Revealed by Cross-Sectional Scanning Tunneling Spectroscopy

    Science.gov (United States)

    Ren, Ming-Qiang; Yan, Ya-Jun; Zhang, Tong; Feng, Dong-Lai

    2016-12-01

    Pairing in the cuprate high-temperature superconductors and its origin remain among the most enduring mysteries in condensed matter physics. With cross-sectional scanning tunneling microscopy/ spectroscopy, we clearly reveal the spatial-dependence or inhomogeneity of the superconducting gap structure of Bi$_2$Sr$_2$CaCu$_2$O$_{8+\\delta}$ (Bi2212) and YBa$_2$Cu$_3$O$_{7-x}$ (YBCO) along their $c$-axes on a scale shorter than the interlayer spacing. By tunneling into the (100) plane of a Bi2212 single crystal and a YBCO film, we observe both U-shaped tunneling spectra with extended flat zero-conductance bottoms, and V-shaped gap structures, in different regions of each sample. On the YBCO film, tunneling into a (110) surface only reveals a U-shaped gap without any zero-bias peak. Our analysis suggests that the U-shaped gap is likely a nodeless superconducting gap. The V-shaped gap has a very small amplitude, and is likely proximity-induced by regions having the larger U-shaped gap.

  18. Probing the density of states of two-level tunneling systems in silicon oxide films using superconducting lumped element resonators

    Energy Technology Data Exchange (ETDEWEB)

    Skacel, S. T. [Physikalisches Institut, Karlsruher Institut für Technologie, Wolfgang-Gaede-Straße 1, D-76131 Karlsruhe (Germany); Institut für Mikro- und Nanoelektronische Systeme, Karlsruher Institut für Technologie, Hertzstraße 16, D-76187 Karlsruhe (Germany); Kaiser, Ch.; Wuensch, S.; Siegel, M. [Institut für Mikro- und Nanoelektronische Systeme, Karlsruher Institut für Technologie, Hertzstraße 16, D-76187 Karlsruhe (Germany); Rotzinger, H.; Lukashenko, A.; Jerger, M.; Weiss, G. [Physikalisches Institut, Karlsruher Institut für Technologie, Wolfgang-Gaede-Straße 1, D-76131 Karlsruhe (Germany); Ustinov, A. V. [Physikalisches Institut, Karlsruher Institut für Technologie, Wolfgang-Gaede-Straße 1, D-76131 Karlsruhe (Germany); Russian Quantum Center, 100 Novaya St., Skolkovo, Moscow Region 143025 (Russian Federation)

    2015-01-12

    We have investigated dielectric losses in amorphous silicon oxide (a-SiO) thin films under operating conditions of superconducting qubits (mK temperatures and low microwave powers). For this purpose, we have developed a broadband measurement setup employing multiplexed lumped element resonators using a broadband power combiner and a low-noise amplifier. The measured temperature and power dependences of the dielectric losses are in good agreement with those predicted for atomic two-level tunneling systems (TLS). By measuring the losses at different frequencies, we found that the TLS density of states is energy dependent. This had not been seen previously in loss measurements. These results contribute to a better understanding of decoherence effects in superconducting qubits and suggest a possibility to minimize TLS-related decoherence by reducing the qubit operation frequency.

  19. Improved Charge Separation in WO3/CuWO4 Composite Photoanodes for Photoelectrochemical Water Oxidation

    Directory of Open Access Journals (Sweden)

    Danping Wang

    2016-05-01

    Full Text Available Porous tungsten oxide/copper tungstate (WO3/CuWO4 composite thin films were fabricated via a facile in situ conversion method, with a polymer templating strategy. Copper nitrate (Cu(NO32 solution with the copolymer surfactant Pluronic®F-127 (Sigma-Aldrich, St. Louis, MO, USA, generic name, poloxamer 407 was loaded onto WO3 substrates by programmed dip coating, followed by heat treatment in air at 550 °C. The Cu2+ reacted with the WO3 substrate to form the CuWO4 compound. The composite WO3/CuWO4 thin films demonstrated improved photoelectrochemical (PEC performance over WO3 and CuWO4 single phase photoanodes. The factors of light absorption and charge separation efficiency of the composite and two single phase films were investigated to understand the reasons for the PEC enhancement of WO3/CuWO4 composite thin films. The photocurrent was generated from water splitting as confirmed by hydrogen and oxygen gas evolution, and Faradic efficiency was calculated based on the amount of H2 produced. This work provides a low-cost and controllable method to prepare WO3-metal tungstate composite thin films, and also helps to deepen the understanding of charge transfer in WO3/CuWO4 heterojunction.

  20. Cu, Fe, or Ni doped molybdenum oxide supported on Al2O3 for the oxidative dehydrogenation of ethylbenzene

    Institute of Scientific and Technical Information of China (English)

    Tiago Pinheiro Braga; Antônio Narcísio Pinheiro; Edson R. Leite; Regina Cláudia R. dos Santos; Antoninho Valentini

    2015-01-01

    Molybdenum-based catalysts supported on Al2O3 doped with Ni, Cu, or Fe oxide were synthesized and used in ethylbenzene dehydrogenation to produce styrene. The molybdenum oxide was sup-ported using an unconventional route that combined the polymeric precursor method (Pechini) and wet impregnation on commercial alumina. The samples were characterized by X-ray diffraction (XRD), N2 adsorption-desorption isotherms, temperature-programmed reduction of H2 (H2-TPR), and thermogravimetric (TG) analysis. XRD results showed that the added metals were well dis-persed on the alumina support. The addition of the metal oxide (Ni, Cu, or Fe) of 2 wt% by wet im-pregnation did not affect the texture of the support. TPR results indicated a synergistic effect be-tween the dopant and molybdenum oxide. The catalytic tests showed ethylbenzene conversion of 28%–53% and styrene selectivity of 94%–97%, indicating that the addition of the dopant improved the catalytic performance, which was related to the redox mechanism. Molybdenum oxides play a fundamental role in the oxidative dehydrogenation of ethylbenzene to styrene by its redox and acid–base properties. The sample containing Cu showed an atypical result with increasing conver-sion during the reaction, which was due to metal reduction. The Ni-containing solid exhibited the highest amount of carbon deposited, shown by TG analysis after the catalytic test, which explained its lower catalytic stability and selectivity.

  1. Comment on magnetism and superconductivity in rutheno cuprates: RuSr2GdCu2O8 and RuSr2Gd1.5Ce0.5Cu2O10

    Indian Academy of Sciences (India)

    V P S Awana; M Karppinen; H Yamauchi

    2002-05-01

    Both RuSr2GdCu2O8- (Ru-1212) and RuSr2Gd1.5Ce0.5Cu2O10- (Ru-1222) exhibits magnetism and superconductivity, as seen by magnetization vs. temperature behavior measured in 5 Oe field. Zero-field-cooled (ZFC) and field-cooled (FC) magnetization data show branching at around 140 K and 100 K with a cusp at 135 K and 80 K and a diamagnetic transition around 20 K and 30 K in the ZFC part, for Ru-1212 and Ru-1222, respectively. The isothermal magnetization possesses a non-linear contribution due to a ferromagnetic component at low temperatures below 50 K for both samples. The resistance vs. temperature behavior of the samples in applied fields of 0, 3 and 7 T confirmed superconductivity, with a different type of broadening of the superconductivity transition under magnetic fields for Ru-1212 from that known for conventional high-c superconductors. The magnetoresistance (MR) is negative above the Ru magnetic ordering temperature at 135 K. Below the Ru magnetic ordering temperature, MR displays a positive peak at low fields and becomes negative at higher fields for Ru-1212. For Ru-1222, MR remains negative both above and below the ordering temperature. A maximum of 2% is observed for the negative MR value at the Ru magnetic ordering temperature. An electron diffraction pattern obtained for the Ru-1212 sample shows two types of superstructure: one has a weak spot at the centre of the - rectangle, and the other only along the direction. Interestingly, Ru-1222 shows only clean - and - planes, without any superstructures.

  2. NO oxidation on Zeolite Supported Cu Catalysts: Formation and Reactivity of Surface Nitrates

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Hai-Ying; Wei, Zhehao; Kollar, Marton; Gao, Feng; Wang, Yilin; Szanyi, Janos; Peden, Charles HF

    2016-04-18

    The comparative activities of a small-pore Cu-CHA and a large-pore Cu-BEA catalyst for the selective catalytic reduction (SCR) of NOx with NH3, and for the oxidation of NO to NO2 and the subsequent formation of surface nitrates were investigated. Although both catalysts are highly active in SCR reactions, they exhibit very low NO oxidation activity. Furthermore, Cu-CHA is even less active than Cu-BEA in catalyzing NO oxidation but is clearly more active for SCR reactions. Temperature-programed desorption (TPD) experiments following the adsorption of (NO2 + NO + O2) with different NO2:NO ratios reveal that the poor NO oxidation activity of the two catalysts is not due to the formation of stable surface nitrates. On the contrary, NO is found to reduce and decompose the surface nitrates on both catalysts. To monitor the reaction pathways, isotope exchange experiments were conducted by using 15NO to react with 14N-nitrate covered catalyst surfaces. The evolution of FTIR spectra during the isotope exchange process demonstrates that 14N-nitrates are simply displaced with no formation of 15N-nitrates on the Cu-CHA sample, which is clearly different from that observed on the Cu-BEA sample where formation of 15N-nitrates is apparent. The results suggest that the formal oxidation state of N during the NO oxidation on Cu-CHA mainly proceeds from its original +2 to a +3 oxidation state, whereas reaching a higher oxidation state for N, such as +4 or +5, is possible on Cu-BEA. The authors at PNNL gratefully acknowledge the US Department of Energy (DOE), Energy Efficiency and Renewable Energy, Vehicle Technologies Office for the support of this work. The research described in this paper was performed at the Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility sponsored by the DOE’s Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory (PNNL). PNNL is operated for the US DOE by Battelle.

  3. First-principles investigations for the catalytic dissociation and oxidation of methane on the Cu surfaces

    Science.gov (United States)

    Li, Ying; Mahadevan, Jagan; Wang, Sanwu

    2010-03-01

    The catalytic reactions of dissociation and oxidation of methane on the copper surfaces play a key role in, for example, the development of high-performance solid oxide fuel cells. We used first-principles quantum theory and large-scale parallel calculations to investigate the atomic-scale mechanism of the catalytic chemical reactions. We report the calculated results, which provide fundamental information and understanding about the atomic-scale dynamics and electronic structures pertinent to the reactions and specifically the catalytic role of the Cu(100) and Cu(111) surfaces. We also report comparison of our results with available experimental data and previous theoretical investigations.

  4. Superconductivity of an oxide film on the surface of Bi(1-x)Sb(x) alloy single crystals produced by electrochemical oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Alfeev, V.N.; Aminov, B.A.; Brandt, N.B.; Vasina, S.IA.; Damaskin, B.B. (Moskovskii Gosudarstvennyi Universitet, Moscow (USSR))

    1989-10-01

    A study is made of the volt-ampere characteristics of point contacts produced by the mechanical compression of the electrochemically oxidized Bi(1-x)Sb(x) single crystals. Volt-ampere characteristics of the Josephson type have been observed at temperatures below Tc=6-8 K, indicating that the oxide films have superconducting properties at these temperatures. In a magnetic field, Mersereau oscillations, typical of a Josephson transition net, are observed in the contact region. In an external microwave field, the volt-ampere characteristics exhibit a structure related to the occurrence of Shapiro steps.

  5. Uptake of Sc 3+ and La 3+ from aqueous solution using ethylenediaminetetraacetate-intercalated Cu-Al layered double hydroxide reconstructed from Cu-Al oxide

    Science.gov (United States)

    Kameda, Tomohito; Hoshi, Kazuaki; Yoshioka, Toshiaki

    2011-02-01

    A Cu-Al layered double hydroxide intercalated with ethylenediaminetetraacetate (edta·Cu-Al LDH) was prepared by suspending Cu-Al oxide, obtained by the calcination of CO32--intercalated Cu-Al LDH, in edta solution. It was found that the reconstruction of Cu-Al oxide to Cu-Al LDH was promoted with an increase in the temperature and time. The reaction in the pH range of around 8 suggests that Hedta 3- was intercalated in the interlayer of Cu-Al LDH. Edta·Cu-Al LDH was found to take up rare metal ions such as Sc 3+ and La 3+ in an aqueous solution at a pH of around 6-6.5. The uptake of Sc 3+ was caused not only by the chelating function of Hedta 3- in the interlayer but also by the chemical behavior of Cu-Al LDH itself. On the other hand, the uptake of La 3+ was caused only by the chelating function of Hedta 3- in the interlayer. The Hedta 3- in the interlayer of edta·Cu-Al LDH had the potential to form a chelate complex more preferentially with Sc 3+ than with La 3+.

  6. Nanoscale coherent intergrowthlike defects in a crystal of La1.9Ca1.1Cu2O6 +δ made superconducting by high-pressure oxygen annealing

    Science.gov (United States)

    Hu, Hefei; Zhu, Yimei; Shi, Xiaoya; Li, Qiang; Zhong, Ruidan; Schneeloch, John A.; Gu, Genda; Tranquada, John M.; Billinge, Simon J. L.

    2014-10-01

    Superconductivity with Tc=53.5 K has been induced in a large La1.9Ca1.1Cu2O6 (La-2126) single crystal by annealing in a high partial pressure of oxygen at 1200 °C. Using transmission electron microscopy techniques, we show that a secondary Ca-doped La2CuO4 (La-214) phase, not present in the as-grown crystal, appears as a coherent intergrowthlike defect as a consequence of the annealing. A corresponding secondary superconducting transition near 13 K is evident in the magnetization measurement. Electron energy-loss spectroscopy reveals a pre-edge peak at the O-K edge in the superconducting La-2126 phase, which is absent in the as-grown crystal, confirming the hole doping by interstitial oxygen.

  7. Deposition by plasma-assisted laser ablation and maskless patterning of YBa[sub 2]Cu[sub 3]O[sub 7-x] superconducting thin films

    Energy Technology Data Exchange (ETDEWEB)

    Tejedor, P. (Centro Nacional de Microelectronica, CSIC, Madrid (Spain)); Cagigal, M. (Dept. de Fisica de Materiales, Univ. Complutense, Madrid (Spain)); Vicent, J.L. (Dept. de Fisica de Materiales, Univ. Complutense, Madrid (Spain)); Briones, F. (Centro Nacional de Microelectronica, CSIC, Madrid (Spain))

    1994-04-01

    YBa[sub 2]Cu[sub 3]O[sub 7-x] superconducting thin films were deposited in situ by plasma-assisted laser ablation onto polycrystalline yttria-stabilized-zirconia (YSZ) substrates at 700 C in a low pressure (200-400 mTorr) O[sub 2] discharge (-300 V). The laser operated at 5-50 Hz repetition rate and was focused onto a superconducting target with a typical energy density of 2.5-4 J cm[sup -2]. An in situ annealing step in 1 Torr O[sub 2] atmosphere at 425 C for 1-2 h was followed by slow cooling of the films to room temperature. The YBa[sub 2]Cu[sub 3]O[sub 7-x] films grew preferentially oriented with the c-axis normal to the substrate surface. They exhibited metallic behaviour in the normal state and superconducting transitions with typical onset of 91 K and zero resistance between 82 and 87 K. The transport critical current densities J[sub c] were 10[sup 2] A cm[sup -2] for 1 [mu]m thick films and two orders of magnitude higher, J[sub c] = 3 x 10[sup 4] A cm[sup -2], for 0.08 [mu]m thick films. Maskless patterning was achieved by utilizing the ArF laser beam to induce etching selectivity of the superconducting thin films. For this purpose, the central part of the beam was apertured by a slit and focused onto the sample by means of a 15 x Schwarzschild microscope objective to give an irradiated area on the sample of approximately 10 x 150 [mu]m[sup 2]. The laser energy density on the sample was typically 10[sup 3] J cm[sup -2], while the repetition rate was varied between 10 and 20 Hz. Microbridges of different geometries with a maximum resolution of 10 [mu]m and high edge definition were obtained at 20 [mu]m s[sup -1] scan rate using this technique. (orig.)

  8. Influence of Pb-rich phases of precursor powder on microstructural evolution in the silver-sheathed (Bi,Pb)2Sr2Ca2Cu3Ox superconducting tapes

    DEFF Research Database (Denmark)

    Chen, X.P.; Grivel, Jean-Claude; Li, M.Y.;

    2010-01-01

    The influence of Pb-rich phases of precursor powder on microstructural evolution during the first heat treatment of the silver-sheathed (Bi,Pb)2Sr2Ca2Cu3Ox ((Bi,Pb)-2223/Ag) superconducting tapes was studied by means of in situ synchrotron X-ray diffraction. Three monofilament tapes were fabricat...

  9. Superconducting material development

    Science.gov (United States)

    1987-09-01

    A superconducting compound was developed that showed a transition to a zero-resistance state at 65 C, or 338 K. The superconducting material, which is an oxide based on strontium, barium, yttrium, and copper, continued in the zero-resistance state similar to superconductivity for 10 days at room temperature in the air. It was also noted that measurements of the material allowed it to observe a nonlinear characteristic curve between current and voltage at 65 C, which is another indication of superconductivity. The research results of the laboratory experiment with the superconducting material will be published in the August edition of the Japanese Journal of Applied Physics.

  10. CuO and Ag2O/CuO Catalyzed Oxidation of Aldehydes to the Corresponding Carboxylic Acids by Molecular Oxygen

    Directory of Open Access Journals (Sweden)

    Yaowu Sha

    2008-04-01

    Full Text Available Furfural was oxidized to furoic acid by molecular oxygen under catalysis by 150nm-sized Ag2O/CuO (92% or simply CuO (86.6%. When 30 nm-size catalyst was used,the main product was a furfural Diels-Alder adduct. Detailed reaction conditions andregeneration of catalysts were investigated. Under optimal conditions, a series of aromaticand aliphatic aldehydes were oxidized to the corresponding acids in good yields.

  11. Garlic's ability to prevent in vitro Cu2+-induced lipoprotein oxidation in human serum is preserved in heated garlic: effect unrelated to Cu2+-chelation

    OpenAIRE

    Menjívar Marta; Barbachano-Esparza Laura; Albarrán Gabriela; Gil-Ortiz Mariana; Pedraza-Chaverrí José; Medina-Campos Omar N

    2004-01-01

    Abstract Background It has been shown that several extracts and compounds derived from garlic are able to inhibit Cu2+-induced low density lipoprotein oxidation. In this work we explored if the ability of aqueous garlic extract to prevent in vitro Cu2+-induced lipoprotein oxidation in human serum is affected by heating (a) aqueous garlic extracts or (b) garlic cloves. In the first case, aqueous extract of raw garlic and garlic powder were studied. In the second case, aqueous extract of boiled...

  12. The YBCO-PbS high-temperature superconducting system. Further investigations. [YBaCuO-PbS

    Energy Technology Data Exchange (ETDEWEB)

    Tyagi, A.K. (Dept. of Applied Physics, GND Univ., Amritsar (India)); Sharma, T.P. (Institute of Advanced Studies, Meerut (India). Dept. of Physics); Shahi, K. (Advanced Centre for Materials Science, IIT, Kanpur (India))

    1993-12-16

    Further investigations on the recently reported YBCO-PbS HTS system are reported. The system is found to have conducting BaPbO[sub 3] as a second phase, which fills the intergrain vacant spaces forming a composite-like microstructure. Thermoanalytical investigations revealed that PbS addition enhances the synthesis of the Y-123-phase and lowers the temperature of partial melting of this phase, which is essential to further reduce the voids. The metallurgical reaction occurring during sintering is also determined and investigated. It is shown that these composite superconducting materials have better normal-state, superconducting, and mechanical properties. (orig.)

  13. Oxidation Control and Non-equilibrium Phase Formation in Cu-Cr Alloys during Mechanical Alloying

    Institute of Scientific and Technical Information of China (English)

    Xiaolong CUI; Lai WANG; Min QI

    2001-01-01

    Using X-ray diffraction (XRD), scanning electron microscopy (SEM), differential scanning calorimeter (DSC) and optical microscopy, phase transformation of Cu-Cr alloys with various compositions during mechanical alloying process has been investigated. Besides the formation of supersaturated solid solution, the results show that a kind of amorphous oxide formed in the process,and the addition of carbon has obviously effect on the suppression of oxidation and the deoxidization of oxide. The reactive milling has a remarkable effect on the behavior of oxidation.

  14. Heteroepitaxy of Cerium Oxide Thin Films on Cu(111

    Directory of Open Access Journals (Sweden)

    Josef Mysliveček

    2015-09-01

    Full Text Available An important part of fundamental research in catalysis is based on theoretical and modeling foundations which are closely connected with studies of single-crystalline catalyst surfaces. These so-called model catalysts are often prepared in the form of epitaxial thin films, and characterized using advanced material characterization techniques. This concept provides the fundamental understanding and the knowledge base needed to tailor the design of new heterogeneous catalysts with improved catalytic properties. The present contribution is devoted to development of a model catalyst system of CeO2 (ceria on the Cu(111 substrate. We propose ways to experimentally characterize and control important parameters of the model catalyst—the coverage of the ceria layer, the influence of the Cu substrate, and the density of surface defects on ceria, particularly the density of step edges and the density and the ordering of the oxygen vacancies. The large spectrum of controlled parameters makes ceria on Cu(111 an interesting alternative to a more common model system ceria on Ru(0001 that has served numerous catalysis studies, mainly as a support for metal clusters.

  15. The Effect of CuSn Intermetallics on the Interstrand Contact Resistance in Superconducting Cables for the Large Hadron Collider (LHC)

    CERN Document Server

    Scheuerlein, C; Jacob, P; Leroy, D; Oberli, L R; Taborelli, M

    2005-01-01

    The LHC superconducting cables are submitted to a 200°C heat-treatment in air in order to increase the resistance between the crossing strands (RC) within the cable. During this treatment the as-applied Sn-Ag alloy strand coating is transformed into a CuSn intermetallic compound layer. The microstructure, the surface topography and the surface chemistry of the non-reacted and reacted coatings have been characterised by different techniques, notably focused ion beam (FIB), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). Based on the results obtained by these techniques the different influences that the intermetallics have on RC are discussed. The desired RC is obtained only when a continuous Cu3Sn layer is formed, i.e. a sufficient wetting of the Cu substrate by the tinning alloy is crucial. Among other effects the formation of the comparatively hard intermetallics roughens the surface and, thus, reduces the true contact area and i...

  16. Comparison of the Isothermal Oxidation Behavior of As-Cast Cu-17 Percent Cr and Cu-17 Percent Cr-5 Percent Al Part II: Scale Microstructures

    Science.gov (United States)

    Raj, Sai V.

    2008-01-01

    The isothermal oxidation kinetics of as-cast Cu-17%Cr and Cu-17%Cr-5%Al in air were studied between 773 and 1173 K under atmospheric pressure. Details of the oxidation kinetics of these alloys were discussed in Part I. This paper analyzes the microstructures of the scale and its composition in an attempt to elucidate the oxidation mechanisms in these alloys. The scales formed on Cu-17%Cr specimens oxidized between 773 and 973 K consisted of external CuO and subsurface Cu2O layers. The total thickness of these scales varied from about 10 m at 773 K to about 450 m at 973 K. In contrast, thin scales formed on Cu-17%Cr-5%Al alloys oxidized between 773 and 1173 K. The exact nature of these scales could not be determined by x-ray diffraction but energy dispersive spectroscopy analyses were used to construct a scale composition map. Phenomenological oxidation mechanisms are proposed for the two alloys.

  17. Comparison of the Isothermal Oxidation Behavior of As-Cast Cu-17 Percent Cr and Cu-17 Percent Cr-5 Percent Al. Part 2; Scale Microstructures

    Science.gov (United States)

    Raj, S. V.

    2008-01-01

    The isothermal oxidation kinetics of as-cast Cu-17%Cr and Cu-17%Cr-5%Al in air were studied between 773 and 1173 K under atmospheric pressure. Details of the oxidation kinetics of these alloys were discussed in Part I. This paper analyzes the microstructures of the scale and its composition in an attempt to elucidate the oxidation mechanisms in these alloys. The scales formed on Cu-17%Cr specimens oxidized between 773 and 973 K consisted of external CuO and subsurface Cu2O layers. The total thickness of these scales varied from about 10 m at 773 K to about 450 m at 973 K. In contrast, thin scales formed on Cu-17%Cr-5%Al alloys oxidized between 773 and 1173 K. The exact nature of these scales could not be determined by x-ray diffraction but energy dispersive spectroscopy analyses were used to construct a scale composition map. Phenomenological oxidation mechanisms are proposed for the two alloys.

  18. Synthesis and characterization of Cu doped cobalt oxide nanocrystals as methane gas sensors

    Energy Technology Data Exchange (ETDEWEB)

    Sheikhi Mehrabadi, Z; Ahmadpour, A [Nanotechnology Research Center, Department of Chemical Engineering, Ferdowsi University of Mashhad, Mashhad (Iran, Islamic Republic of); Shahtahmasebi, N [Nanotechnology Research Center, Department of Physics, Ferdowsi University of Mashhad, Mashhad (Iran, Islamic Republic of); Bagheri Mohagheghi, M M, E-mail: m_mohagheghee@yahoo.co.uk [School of Physics, Damghan University, Damghan (Iran, Islamic Republic of)

    2011-07-01

    In this paper, nanoparticles of copper-cobalt compound oxide have been prepared by the sol-gel technique with different mole ratios of Cu/Co (ranging from 0.05 to 0.15) for the detection of methane gas, which is chemically a very stable hydrocarbon. The structural properties and morphology of the powders were studied by x-ray diffraction (XRD), Fourier transform infrared spectroscopy and transmission electron microscopy (TEM). By XRD analysis, we confirm that Co{sub 3}O{sub 4} and (CuO{sub 0.3}CoO{sub 0.7}) Co{sub 2}O{sub 4} phases are formed and mean grain size is decreased with increasing Cu doping (from 28 to 24 nm). On the basis of TEM images, it is found that these particles possess a cubic structure with nearly uniform distribution. Also, gas-sensing measurements reveal that the optimal operating temperature is 300 {sup 0}C, that the use of Cu as a dopant improved the sensing properties of cobalt oxide and that the sensitivity increased considerably with Cu concentration. The best sensitivity properties of nanosensors have been found at the mole ratios of Cu/Co of 0.125 and 0.15.

  19. Atomic layer deposition of Cu( i ) oxide films using Cu( ii ) bis(dimethylamino-2-propoxide) and water

    Energy Technology Data Exchange (ETDEWEB)

    Avila, J. R.; Peters, A. W.; Li, Zhanyong; Ortuño, M. A.; Martinson, A. B. F.; Cramer, C. J.; Hupp, J. T.; Farha, O. K.

    2017-01-01

    To grow fIlms of Cu2O, bis-(dimethylamino-2-propoxide)Cu(II), or Cu(dmap), is used as an atomic layer deposition precursor using only water vapor as a co-reactant. Between 110 and 175 °C, a growth rate of 0.12 ± 0.02 Å per cycle was measured using an in situ quartz crystal microbalance (QCM). X-ray photoelectron spectroscopy (XPS) confirms the growth of metal– oxide films featuring Cu(I).

  20. Formation and stability of small well-defined Cu- and Ni oxide particles

    Energy Technology Data Exchange (ETDEWEB)

    Thalinger, Ramona [Institute of Physical Chemistry, University of Innsbruck, A-6020 Innsbruck (Austria); Heggen, Marc; Stroppa, Daniel G. [Ernst Ruska Zentrum und Peter Grünberg Institut, Forschungszentrum Jülich GmbH, 52425 Jülich (Germany); Stöger-Pollach, Michael [University Service Facility for Transmission Electron Microscopy (USTEM), Vienna University of Technology, A-1040 Vienna (Austria); Klötzer, Bernhard [Institute of Physical Chemistry, University of Innsbruck, A-6020 Innsbruck (Austria); Penner, Simon, E-mail: simon.penner@uibk.ac.at [Institute of Physical Chemistry, University of Innsbruck, A-6020 Innsbruck (Austria)

    2013-12-16

    Well-defined and -structured Cu/Cu{sub 2}O and Ni/NiO composite nanoparticles have been prepared by physical-vapor deposition on vacuum-cleaved NaCl(001) single crystal facets. Epitaxial growth has been observed due to the close crystallographic matching of the respective cubic crystal lattices. Distinct particle morphologies have only been obtained for the Ni/NiO particles, comprising truncated half-octahedral, rhombohedral- and pentagonal-shaped outlines. Oxidation of the particles in the temperature range 473–673 K in both cases led to the formation of well-defined CuO and NiO particles with distinct morphologies. Whereas CuO possibly adopts its thermodynamical equilibrium shape, NiO formation is accompanied by entering a Kirkendall-like state, that is, a hollow core–shell structure is obtained. The difference in the formation of the oxides is also reflected by their stability under reducing conditions. CuO transforms back to a polycrystalline mixture of Cu metal, Cu{sub 2}O and CuO after reduction in hydrogen at 673 K. In contrast, as expected from theoretical stability considerations, the formation of the hollow NiO structure is reversed upon annealing in hydrogen at 673 K and moreover results in the formation of a Ni-rich silicide structure Ni{sub 3}Si{sub 2}. The discussed systems present a convenient way to tackle and investigate various problems in nanotechnology or catalysis, including phase transformations, establishing structure/activity relationships or monitoring intermetallic particles, starting from well-defined and simple models. - Highlights: • Preparation of epitaxial Cu/Cu{sub 2}O and Ni/NiO composite nanoparticles on NaCl(001). • Distinct Ni/NiO particle morphologies. • Formation of well-shaped CuO and NiO particles upon oxidation. • Reversal of Kirkendall-NiO-state upon reduction/annealing in hydrogen.