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Sample records for superconducting composites cu 2

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. Phase composition and properties of superconducting ceramics based on Bi1.7Pb0.3Sr2Ca2Cu3O y precursors fabricated by melt quenching in a solar furnace

    Science.gov (United States)

    Gulamova, D. D.; Uskenbaev, D. E.; Fantozzi, G.; Chigvinadze, J. G.; Magradze, O. V.

    2009-06-01

    Production of superconducting ceramics based on precursors with rated composition Bi1.7Pb0.3Sr2Ca2Cu3O y is studied. The precursors are synthesized in a solar furnace by melt rapid quenching. The phase composition of the samples is examined by microstructural and X-ray analyses. The temperature dependences of the resistance and magnetic susceptibility are measured. The influence of the composition and crystal structure of the substrate on texturing in the Bi-Sr-Ca-Cu-O system is studied. It is found that the type of quenching plays a significant role, while the type of substrate is of minor significance.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. Strain control of composite superconductors to prevent degradation of superconducting magnets due to a quench: I. Ag/Bi2Sr2CaCu2Ox multifilament round wires

    Science.gov (United States)

    Ye, Liyang; Li, Pei; Jaroszynski, Jan; Schwartz, Justin; Shen, Tengming

    2017-02-01

    The critical current of many practical superconductors is sensitive to strain, and this sensitivity is exacerbated during a quench that induces a peak local strain which can be fatal to superconducting magnets. Here, a new method is introduced to quantify the influence of the conductor stress and strain state during normal operation on the margin to degradation during a quench, as measured by the maximum allowable hot spot temperature T allowable, for composite wires within superconducting magnets. The first conductor examined is Ag-sheathed Bi2Sr2CaCu2Ox round wire carrying high engineering critical current density, J E, of 550 A mm-2 at 4.2 K and 15 T. The critical axial tensile stress of this conductor is determined to be 150 MPa and, in the absence of Lorentz forces, T allowable is greater than 450 K. With increasing axial tensile stress, σ a, however, T allowable decreases nonlinearly, dropping to 280 K for σ a = 120 MPa and to 160 K for σ a = 145 MPa. T allowable(σ a) is shown to be nonlinear and independent of magnetic field from 15 to 30 T. T allowable(σ a) dictates the balance between magnetic field generation, which increases with the magnet operating current and stress, and the safety margin, which decreases with decreasing T allowable, and therefore has important engineering value. It is also shown that T allowable(σ a) can be predicted accurately by a general strain model, showing that strain control is the key to preventing degradation of superconductors during a quench.

  12. 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...

  13. 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.

  14. 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.

  15. 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.

  16. 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...

  17. 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...

  18. 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....

  19. 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.

  20. 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.

  1. 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.

  2. 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...

  3. 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...

  4. 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.

  5. 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.

  6. 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.

  7. 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.)

  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. 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.

  10. 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.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-09-01

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

  12. 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.

  13. 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.

  14. 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.)

  15. 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.

  16. 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.

  17. 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

  18. 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...

  19. 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.

  20. 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.

  1. Superconducting composites materials. Materiaux composites supraconducteurs

    Energy Technology Data Exchange (ETDEWEB)

    Kerjouan, P.; Boterel, F.; Lostec, J.; Bertot, J.P.; Haussonne, J.M. (Centre National d' Etudes des Telecommunications (CNET), 22 - Lannion (FR))

    1991-11-01

    The new superconductor materials with a high critical current own a large importance as well in the electronic components or in the electrotechnical devices fields. The deposit of such materials with the thick films technology is to be more and more developed in the years to come. Therefore, we tried to realize such thick films screen printed on alumina, and composed mainly of the YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} material. We first realized a composite material glass/YBa{sub 2}Cu{sub 3}O{sub 7-{delta}}, by analogy with the classical screen-printed inks where the glass ensures the bonding with the substrate. We thus realized different materials by using some different classes of glass. These materials owned a superconducting transition close to the one of the pure YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} material. We made a slurry with the most significant composite materials and binders, and screen-printed them on an alumina substrate preliminary or not coated with a diffusion barrier layer. After firing, we studied the thick films adhesion, the alumina/glass/composite material interfaces, and their superconducting properties. 8 refs.; 14 figs.; 9 tabs.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.).

  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. 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.

  12. 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)

  13. Synthesis and photocatalytic activity of carbon spheres loaded Cu{sub 2}O/Cu composites

    Energy Technology Data Exchange (ETDEWEB)

    Li, Yinhui, E-mail: lillian09281@hotmail.com; Zhao, Mengyao; Zhang, Na; Li, Ruijuan; Chen, Jianxin

    2015-09-15

    Highlights: • Carbon spheres loaded Cu{sub 2}O/Cu composites are obtained by hydrothermal process. • Cu{sub 2}O/Cu nanocrystals grow on the surface of carbon spheres. • The composites with core–shell structure show highly photo-catalytic activity. • The composites can degrade methyl orange under simulated solar light irradiation. • The composites can be used to treat dye wastewater or organic pollutants. - Abstract: In this work, using amylose as carbon source and cupric acetate as copper source, carbon spheres loaded Cu{sub 2}O/Cu composites were obtained by hydrothermal synthesis. The effects of the molar ratios between glucose and Cu(II), and hydrothermal time on the morphology and sizes of the composites were investigated. The result of photocatalytic experiments demonstrated that the composites could degrade methyl orange in aqueous solution under simulated solar light irradiation. The highest degradation rate was achieved to 93.83% when the composites were prepared by hydrothermal synthesis at 180 °C for 16 h and the molar ratio between glucose and Cu(II) was 10/1. The composites, as new and promising materials, can be used to treat dye wastewater or other organic pollutants.

  14. 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.

  15. 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.

  16. 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.

  17. Phase composition and superconducting properties of (Pb sub 0 sub . sub 6 Sn sub y Cu sub 0 sub . sub 4 sub - sub y)Sr sub 2 (Y sub 1 sub - sub x Ca sub x)Cu sub 2 O sub z

    CERN Document Server

    Balchev, N; Kunev, B; Souleva, A; Tsacheva, T

    2001-01-01

    The effect of Sn-doping in (Pb sub 0 sub . sub 6 Sn sub y Cu sub 0 sub . sub 4 sub - sub y)Sr sub 2 (Y sub 1 sub - sub x Ca sub x)Cu sub 2 O sub z for 0 <= y <= 0.3 and 0 <= x <= 0.7 was investigated. It was established that a nearly pure 1212 phase could be obtained at 0 <= y <= 0.1 and 0 <= x <= 0.3. The obtained X-ray diffraction (XRD) patterns as well as the results of the inductively coupled plasma atomic emission spectrometry (ICP-AES) and energy-dispersive X-ray (EDX) analysis showed that the Sn-substitution was possible in the (Pb,Cu)-1212 phase. Superconductivity was observed at 0.4 <= x <= 0.7. The onset of the diamagnetic transitions varied from 10 to 30 K. The influence of the strong Pb deficiency on the superconducting properties of the samples was discussed. (authors)

  18. 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...

  19. 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).

  20. Direct synthesis of RGO/Cu{sub 2}O composite films on Cu foil for supercapacitors

    Energy Technology Data Exchange (ETDEWEB)

    Dong, Xiangmao; Wang, Kun [Key Laboratory for Ultrafine Materials of the Ministry of Education, Shanghai Key Laboratory of Advanced Polymeric Materials, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237 (China); Zhao, Chongjun, E-mail: chongjunzhao@ecust.edu.cn [Key Laboratory for Ultrafine Materials of the Ministry of Education, Shanghai Key Laboratory of Advanced Polymeric Materials, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237 (China); Institute for Superconducting and Electronic Materials, University of Wollongong, Wollongong 2500 (Australia); Qian, Xiuzhen [Key Laboratory for Ultrafine Materials of the Ministry of Education, Shanghai Key Laboratory of Advanced Polymeric Materials, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237 (China); Chen, Shi [School of Information Engineering, Wuhan University of Technology, Wuhan 430070 (China); Li, Zhen, E-mail: zhenl@uow.edu.au [Institute for Superconducting and Electronic Materials, University of Wollongong, Wollongong 2500 (Australia); Liu, Huakun; Dou, Shixue [Institute for Superconducting and Electronic Materials, University of Wollongong, Wollongong 2500 (Australia)

    2014-02-15

    Graphical abstract: RGO/Cu{sub 2}O/Cu composites were synthesized by simple hydrothermal treatment of copper foils with graphene oxide, in which the reduction of graphene oxide and the formation of Cu{sub 2}O nanoparticles simultaneously happened in one-pot reaction. These composites can be directly used as electrodes of supercapacitors with the highest specific capacitance of 98.5 F/g at 1 A g{sup −1}, which is much better than that of CuO or Cu{sub 2}O electrodes. -- Highlights: • The RGO/Cu{sub 2}O/Cu composites were obtained by a friendly method in one step. • Improved capacitance performance is realized by the hydrothermal treatment of graphene oxides with Cu foils. • RGO/Cu{sub 2}O/Cu-200 composites exhibit the largest specific capacitance of 98.5 F g{sup −1} at 1 A g{sup −1}. -- Abstract: Reduced graphene oxide/cuprous oxide (RGO/Cu{sub 2}O) composite films were directly synthesized on the surface of copper foil substrates through a straight redox reaction between GO and Cu foil via a hydrothermal approach. Characterization of the resultant composites with X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, and field emission scanning electron microscope (FESEM) confirms the formation of Cu{sub 2}O and reduction of GO, in which Cu{sub 2}O nanoparticles were well covered by RGO. The resultant composites (referred to as RGO/Cu{sub 2}O/Cu) were directly used as electrodes for supercapacitors, and their electrochemical performance was assessed by cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), and electrochemical impedance spectrometry (EIS) in 1 M KOH aqueous solution. A specific capacitance of 98.5 F g{sup −1} at 1 A g{sup −1} was obtained, which is much higher than that of pure Cu{sub 2}O prepared under the same conditions, due to the presence of RGO.

  1. 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.

  2. 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.

  3. 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.

  4. 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).

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  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. 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.

  13. 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.

  14. 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.

  15. 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.>

  16. Structural and magnetic properties of YBa2Cu3O7/BaZrO3 composites

    Directory of Open Access Journals (Sweden)

    David A. Landínez-Téllez

    2013-01-01

    Full Text Available We reported a study of the structural and magnetic properties of BaZrO3 (BZO as possible substrate material for the production of YBa2Cu3O7-δ (YBCO superconducting films. Rietveld analyses of the X-ray diffraction pattern show that BZO crystalizes as a cubic perovskite, space group Pm3m (#221. Chemical stability and crystallographic coupling between BZO and YBCO were examined by characterizing YBCO/BZO (10, 30 and 50 YBCO vol% polycrystalline composites. Morphological and compositional analyses of composites were performed through scanning electron microscopy and energy dispersive X-ray experiments, respectively. Response of magnetization measurements revealed that the proximity of BZO does not affect the superconducting transition temperature (Tc=90,2 K of YBCO material. Our results evidenced that the BZO is an excellent candidate to be substrate for the fabrication of YBCO superconducting thin films.

  17. 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.

  18. 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.

  19. Physical Properties of (BaSnO3)_x/Cu_{0.5}Tl_{0.5}Ba2Ca2Cu3O_{10{-}δ } Superconductor Composite

    Science.gov (United States)

    Srour, A.; Awad, R.; Malaeb, W.; Barakat, M. ME.

    2017-08-01

    The influence of barium tin oxide nanoparticles addition on the structural and superconducting properties of the Cu_{0.5}Tl_{0.5}Ba2Ca2Cu3O_{10{-}δ } phase, (CuTl)-1223, was studied. A different wt% of BaSnO3 , ranging from 0.00 to 1.50, were added into (CuTl)-1223 phase, and this composite was synthesized using the solid-state reaction technique. The phase formation and lattice parameters were calculated from X-ray powder diffraction measurements. The grain connectivity and surface morphology were identified using scanning electron microscope. Energy dispersive X-ray spectroscopy gave the real elemental composition of the prepared samples. Superconducting transition temperature ({T_c}) and critical current density ({J_c}) were determined from the electrical resistivity and I-V measurements, respectively. A complete study about the vibration modes of different atoms was carried out using Fourier transform infrared (FTIR) absorption spectroscopy of (BaSnO3)_x/CuTl-1223 composite. The increase in {T_c} and {J_c} up to x=0.25 wt% is an evidence for improving the superconducting properties of (BaSnO3)_x/CuTl-1223 composites by enhancing both the inter-grains coupling and volume fraction of the (CuTl)-1223 phase.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.).

  5. 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.

  6. 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.

  7. 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 .

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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

  13. 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.

  14. The effect of composition on the occurrence of a second phase transition in the vicinity of T{sub c} in CeCu{sub 2}Si{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Modler, R. [Technische Hochschule Darmstadt (Germany). Inst. fuer Festkoerperphysik]|[Kernforschungszentrum Karlsruhe, INFP, D 76021 Karlsruhe (Germany); Lang, M. [Technische Hochschule Darmstadt (Germany). Inst. fuer Festkoerperphysik; Geibel, C. [Technische Hochschule Darmstadt (Germany). Inst. fuer Festkoerperphysik; Schank, C. [Technische Hochschule Darmstadt (Germany). Inst. fuer Festkoerperphysik; Mueller-Reisener, R. [Technische Hochschule Darmstadt (Germany). Inst. fuer Festkoerperphysik; Hellmann, P. [Technische Hochschule Darmstadt (Germany). Inst. fuer Festkoerperphysik; Link, A. [Technische Hochschule Darmstadt (Germany). Inst. fuer Festkoerperphysik; Sparn, G. [Technische Hochschule Darmstadt (Germany). Inst. fuer Festkoerperphysik; Assmus, W. [Physikalisches Institut der Universitaet Frankfurt, D 60054 Frankfurt (Germany); Steglich, F. [Physikalisches Institut der Universitaet Frankfurt, D 60054 Frankfurt (Germany)

    1995-02-01

    We report on measurements of the thermal expansion and specific heat on a series of polycrystalline CeCu{sub 2}Si{sub 2} samples with small variations in the stoichiometry. The occurrence of superconductivity and/or the surrounding phase labeled `A`, were found to be most sensitively controlled by the Ce:Cu:Si composition. ((orig.)).

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. High-T{sub c} superconductivity in Bi{sub 1.6}Pb{sub 0.4}Sr{sub 2}Ca{sub 2}Cu{sub 2+x}O{sub y} compounds

    Energy Technology Data Exchange (ETDEWEB)

    Ali, Zahida; Maqsood, Asghari; Maqsood, Muhammad; Ramay, S.M.; Yousaf, Mohammad [Thermal Physics Laboratory, Department of Physics, Quaid-I-Azam University, Islamabad (Pakistan); Anwar-ul-Haq [Metallurgy Division, Dr A Q Khan Research Laboratories, Kahuta, Rawalpindi (Pakistan)

    1996-05-01

    Superconducting samples with the nominal composition Bi{sub 1.6}Pb{sub 0.4}Sr{sub 2}Ca{sub 2}Cu{sub 2+x}O{sub y} (x = 1.6, 1.8, 2.0) have been prepared by a solid state reaction technique. The resistivity data reveal the occurrence of multi phases in all the samples. By a process of ageing over 2 years then re annealing, a dramatic increase in T{sub c} was observed in the above system for x=2.0. We achieved zero resistance at 130 K, which is the highest in the composition Bi{sub 1.6}Pb{sub 0.4}Sr{sub 2}Ca{sub 2}Cu{sub 2+x}O{sub y} (x = 1.6, 1.8, 2.0) reported so far but the recipe is often not reproducible. This shows that the system is sensitive to Cu composition and to the conditions of preparation. Furthermore, long storage leads to a deterioration in the superconducting properties. X-ray diffraction studies show that these samples mainly contain the (2223) phase. However, in each sample, a few lines could not be indexed, which may indicate the presence of some new phase. (author)

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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}).

  6. 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.

  7. 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.

  8. 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

  9. Photoelectrochemical Properties of CuS-GeO2-TiO2 Composite Coating Electrode

    Science.gov (United States)

    Wen, Xinyu; Zhang, Huawei

    2016-01-01

    The ITO (indium tin oxide) conductive glass-matrix CuS-GeO2-TiO2 composite coating was generated via EPD (electrophoretic deposition) and followed by a sintering treatment at 450°C for 40 minutes. Characterizations of the CuS-GeO2-TiO2 composite coating were taken by SEM (scanning electron microscope), XRD (X-ray diffraction), EDX (energy dispersive X-ray), UV-Vis DRS (ultraviolet-visible diffuse reflection spectrum), and FT-IR (Fourier transform infrared spectroscopy). Results showed that CuS and GeO2 had dispersed in this CuS-GeO2-TiO2 composite coating (mass percentages for CuS and GeO2 were 1.23% and 2.79%, respectively). The electrochemical studies (cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and Tafel polarization) of this CuS-GeO2-TiO2 composite coating electrode were performed in pH = 9.51 Na2CO3-NaHCO3 buffer solution containing 0.50 mol/L CH3OH under the conditions of visible light, ultraviolet light (λ = 365 nm), and dark (without light irradiation as control), respectively. Electrochemical studies indicated that this CuS-GeO2-TiO2 composite coating electrode had better photoelectrocatalytic activity than the pure TiO2 electrode in the electrocatalysis of methanol under visible light. PMID:27055277

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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)

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.)

  2. Photocatalytic performance of Cu2O composite octahedra prepared by a propanetriol-reduced process

    Science.gov (United States)

    Zhang, Lihui; Wang, Xiangfu

    2014-12-01

    Cu2O and Ag/Cu2O composite octahedra were synthesized via a hydrothermal reaction of CuAc2 with urea in H2O-propanetriol binary solution by adjusting the quantity of AgNO3 at 180 °C for 10 h. The influence of reaction temperature and time on the morphology and phase of the products was investigated, and a possible growth mechanism of Cu2O octahedron was also proposed. The photocatalytic activities of the as-prepared Cu2O and Ag/Cu2O octahedra for the degradation of methyl orange aqueous solution were studied. The results show that they are effective photocatalysts for the degradation of methyl orange, and the photocatalytic ability of Ag/Cu2O composite is stronger than that of Cu2O octahedra, which are expected to be useful in the treatment of wastewaters.

  3. Effect of Cu2O morphology on photocatalytic hydrogen generation and chemical stability of TiO2/Cu2O composite.

    Science.gov (United States)

    Zhu, Lihong; Zhang, Junying; Chen, Ziyu; Liu, Kejia; Gao, Hong

    2013-07-01

    Improving photocatalytic activity and stability of TiO2/Cu2O composite is a challenge in generating hydrogen from water. In this paper, the TiO2 film/Cu2O microgrid composite was prepared via a microsphere lithography technique, which possesses a remarkable performance of producing H2 under UV-vis light irradiation, in comparison with pure TiO2 film, Cu2O film and TiO2 film/Cu2O film. More interesting is that in TiO2 film/Cu2O microgrid, photo-corrosion of Cu2O can be retarded. After deposition of Pt on its surface, the photocatalytic activity of TiO2/Cu2O microgrid in producing H2 is improved greatly.

  4. Electrochemical performance of electroactive poly(amic acid)-Cu2+ composites

    Science.gov (United States)

    Yan, Ying; Li, Fangfei; Hanlon, Ashley M.; Berda, Erik B.; Liu, Xincai; Wang, Ce; Chao, Danming

    2017-01-01

    Electroactive poly(amic acid)-Cu2+ (EPAA-Cu) composites on substrates were successfully prepared via nucleophilic polycondensation followed by the use of an immersing method. Analysis of the structure properties of EPAA-Cu composites was performed using scanning electron microscopy (SEM), X-ray photoelectron spectra (XPS) and Fourier-transform infrared spectra (FTIR). A significant current enhancement phenomenon of EPAA-Cu/ITO electrodes was found as evident from cyclic voltammetry (CV) measurements. In addition, Cu2+ ions were incorporated into the composites and had a positive effect on their electrochromic behaviors decreasing their switching times. The anticorrosive performance of EPAA-Cu composites coatings on the carbon steel in 3.5 wt% NaCl solution were also investigated in detail using tafel plots analysis and electrochemical impedance spectroscopy. The anticorrosive ability of these coatings significantly enhanced through the incorporation of Cu2+ ions.

  5. 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.

  6. 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.

  7. Optimization of BaZrO3 concentration as secondary phase in superconducting YBa2Cu3O7 for high current applications

    Science.gov (United States)

    Malik, Bilal A.; Malik, Manzoor A.; Asokan, K.

    2016-04-01

    We report the superconducting state properties of YBa2Cu3O7 (YBCO) on introduction of BaZrO3 (BZO) as a secondary phase. YBCO+xBZO (x= 0, 2, 4, 6, and 10 wt%) composite samples were prepared by solid state reaction method and characterized for structural, morphological and superconducting properties. X-ray diffraction confirms the increased crystallinity and images of scanning electron microscopy measurement show an increase in both grain size and grain connectivity on addition of BZO in YBCO. These effects are well pronounced in an applied magnetic field. Critical current density, JC, as well as the pinning force peaks at 4% of BZO concentration showed significant difference. A three-fold enhancement in JC and a six-fold enhancement in pinning force were observed at this optimum BZO concentration. This has been attributed to the pinning of flux lines in YBCO due to introduction of BZO as a secondary phase. These results show that this composite has potential application in high current applications.

  8. Optimization of BaZrO3 concentration as secondary phase in superconducting YBa2Cu3O7 for high current applications

    Directory of Open Access Journals (Sweden)

    Bilal A. Malik

    2016-04-01

    Full Text Available We report the superconducting state properties of YBa2Cu3O7 (YBCO on introduction of BaZrO3 (BZO as a secondary phase. YBCO+xBZO (x= 0, 2, 4, 6, and 10 wt% composite samples were prepared by solid state reaction method and characterized for structural, morphological and superconducting properties. X-ray diffraction confirms the increased crystallinity and images of scanning electron microscopy measurement show an increase in both grain size and grain connectivity on addition of BZO in YBCO. These effects are well pronounced in an applied magnetic field. Critical current density, JC, as well as the pinning force peaks at 4% of BZO concentration showed significant difference. A three-fold enhancement in JC and a six-fold enhancement in pinning force were observed at this optimum BZO concentration. This has been attributed to the pinning of flux lines in YBCO due to introduction of BZO as a secondary phase. These results show that this composite has potential application in high current applications.

  9. Effect of CuF2 on the Synthesis and Superconducting Properties of (Bi,Pb)2Sr2Ca2Cu3O10 Bulk Ceramic Samples

    DEFF Research Database (Denmark)

    Grivel, Jean-Claude; Andersen, Niels Hessel

    2013-01-01

    Bulk polycrystalline samples with Bi1.72Pb0.34Sr1.87Ca1.91Cu3.13O9.83−x F x (0.00≤x≤0.51) were prepared by a solid-state route using CuF2 as a fluorine source. CuF2 was introduced in the precursor powders either by direct mixing with the other starting reagents or by addition to precalcined precu...

  10. 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.

  11. 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.)

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. Superconducting transition width (ΔT c) characteristics of 25 mol% Zr-added (Gd, Y)Ba2Cu3O7-δ superconductor tapes with high in-field critical current density at 30 K

    Science.gov (United States)

    Heydari Gharahcheshmeh, M.; Galstyan, E.; Xu, A.; Kukunuru, J.; Katta, R.; Zhang, Y.; Majkic, G.; Li, X.-F.; Selvamanickam, V.

    2017-01-01

    The superconducting transition width (∆T c) characteristics of REBa2Cu3O7-δ (REBCO and RE = Gd, Y) superconductor tapes with Zr content of 25 mol% with high lift factor (ratio of critical current density (J c) at 30 K, 3 T (B||c) to the J c at 77 K, 0 T) has been determined. In this work, heavily doped (Gd, Y)Ba2Cu3O7-δ superconductor tapes with 25 mol% Zr addition were fabricated by metal organic chemical vapor deposition using a reel-to reel process. The optimal chemical composition range of (Gd, Y)Ba2Cu3O7-δ superconductor tapes with Zr content of 25 mol% to achieve critical current densities above 3.5 MA cm-2 at 77 K in zero applied magnetic field has been determined. A superconducting transition width (∆T c) as narrow as 0.4 K and an onset critical transition temperature (T c-onset) as high as 92 K were obtained in the 25 mol% Zr-added (Gd, Y)BaCuO superconductor tapes. Based on the mapped compositional phase diagram of the ∆Tc and lift factor, ∆T c in the range of 0.7-0.9 K is observed in 25 mol% Zr-added (Gd, Y)BaCuO superconductor tapes with a high lift factor.

  17. 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.

  18. 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...

  19. 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...

  20. 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...

  1. 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...

  2. 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.

  3. 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....

  4. Superconducting gap and order parameter in Bi2Sr2CaCu2O8+x

    Science.gov (United States)

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

    1994-07-01

    Using angle-resolved photoemission, we observed a nonzero superconducting gap and the presence of a superconducting condensate along all three major symmetry directions. We find that the gap is highly anisotropic, with a gap as small as 1-2 meV along Γ-Y, 4-8 meV along Γ-X, and 14-20 meV along Γ-M. We argue that our data imply either an anisotropic s-wave order parameter or an unconventional, two-component order parameter, and that measuring the size of the gap does not by itself distinguish between the two possibilities. We propose a phenomenological unconventional order parameter, and note the quantitative agreement between theory and experiment.

  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. 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.

  7. 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

  8. 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+.

  9. 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

  10. 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.

  11. Nb Substitution Effects on Superconducting Properties of Ru1−xNbxSr2Eu1.4Ce0.6Cu2O10−δ

    Directory of Open Access Journals (Sweden)

    J. L. Maldonado-Mejía

    2013-01-01

    Full Text Available In order to gain further insight into the role of substitution of Ru by Nb on superconductivity, polycrystalline samples of Ru1−xNbxSr2Eu1.4Ce0.6Cu2O10−δ  (0.0 ≤ x ≤ 1.0 have been synthesized by solid-state reaction method. Substitution of Nb at the Ru site in the system takes place isostructurally in the tetragonal structure (space group I4/mmm with full solubility (x = 1.0. Superconductivity exists for all compositions. Resistivity measurements in function of temperature from 0 to 300 K were done using the four-probe technique. It is found that the substitution of Ru5+ for Nb5+ depresses the superconductivity of samples from Tc = 29 K for x = 0.0 to Tc = 5 K for x = 1.0 (where Tc is the critical temperature, when resistivity becomes equal to zero. In the normal state, the dependence of resistivity with temperature, for compositions with x = 0.0 and 0.2, shows a metallic behavior, while for compositions between x = 0.4 and x = 1 it shows a semiconducting behavior. In that way, the density of charge carriers is reduced with niobium doping, leading to the semiconducting behavior. The resistive transition to the superconducting state of all samples is found to be affected by granularity. Samples undergo double superconducting transition.

  12. Synthesis of p-Cu2O/rGO composite films for enhancing photocurrent of p-Cu2O and H2 generation

    Science.gov (United States)

    Samarakoon, S. P. A. U. K.; Karunarathna, P. G. D. C. K.; Hemachandra, K. A. S. K.; Fernando, C. A. N.

    2017-08-01

    Composites of p type cuprous oxide (p-Cu2O) and reduced graphene oxide (rGO) were prepared by depositing an rGO layer on top of nano-sized Cu2O particles prepared on a Cu substrate. These synthesized composites help to enhance the photocurrent over that of bare Cu2O, which means rGO acts as an excellent electron acceptor to separate electrons from Cu2O particles. Here the p-Cu2O layer was fabricated using thermal oxidation and the rGO layer was fabricated using electrophoretic deposition (EPD). The samples thus fabricated were characterized using diffuse reflectance spectra, Fourier transmission infrared (FTIR) spectra, scanning electron microscopy (SEM) images, time development of the photocurrent of photoelectrochemical cells, and electrochemical impedance spectroscopy (EIS) measurements. H2 evolution was observed using a gas chromatograph system.

  13. 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.

  14. 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.

  15. 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.

  16. Influence of the utilized precursors on the morphology and properties of YBa{sub 2}Cu{sub 3}O{sub 7−y} superconducting nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Alikhanzadeh-Arani, Sima [Plasma Physics Research Center, Science and Research Branch, Islamic Azad University, Tehran, Islamic Republic of Iran (Iran, Islamic Republic of); Salavati-Niasari, Masoud, E-mail: salavati@kashanu.ac.ir [Institute of Nano Science and Nano Technology, University of Kashan, Kashan, P.O. Box 87317-51167, Islamic Republic of Iran (Iran, Islamic Republic of); Almasi-Kashi, Mohammad [Department of Physics, University of Kashan, Kashan, 87317-51167, Islamic Republic of Iran (Iran, Islamic Republic of)

    2013-05-15

    Highlights: ► YBa{sub 2}Cu{sub 3}O{sub 7−x} (Y-123) nanoparticles was synthesized by solid state processing. ► Inorganic precursor was used in the synthesis of YBa{sub 2}Cu{sub 3}O{sub 7−x}. ► The effect of calcinations on morphology and particle size were investigated. -- Abstract: In order to prevent agglomeration of high temperature ceramic material, the solid state processing based on new and appropriate yttrium complex precursors without applying surfactant has been suggested. These have been prepared by a reaction of yttrium acetate with three coordination compositions, acetylacetone, 2-hydroxo-1-naphthaldehyde and salicylaldehyde, for forming yttrium complex types. It was found that the size and morphology of products are clearly dependent on the type of utilized precursor because the organic ligands around yttrium center in these novel precursors act like a protecting agent. Magnetic susceptibility measurements showed that T{sub c} of the superconducting nanoparticles is from 82 K to 88.4 K. The crystalline structures of the nanoparticles remained in orthorhombic symmetry. Characterizations of specimens were performed using scanning electron microscopy and transmission electron microscopy, supported by other techniques including XRD diffraction, energy dispersive X-ray, FT-IR spectrum and magnetic susceptibility measurements.

  17. 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.

  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. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. Facile synthesis of uniform hierarchical composites CuO-CeO2 for enhanced dye removal

    Science.gov (United States)

    Xu, Pan; Niu, Helin; Chen, Jingshuai; Song, Jiming; Mao, Changjie; Zhang, Shengyi; Gao, Yuanhao; Chen, Changle

    2016-12-01

    The hierarchically shaped CuO-CeO2 composites were prepared through a facile solvothermal method without using any template. The as-prepared products were characterized by X-ray powder diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, and N2 adsorption-desorption analysis. In the characterization, we found that CuO-CeO2 composites were showed uniform size and morphology which were consisted of the secondary nanoflakes interconnected with each other. Most interestingly, the composites showed efficient performance to remove methyl blue and Congo red dyes from water with maximum adsorption capacities of 2131.24 and 1072.09 mg g-1, respectively. In addition, because of their larger surface area and the unique hierarchical structures, the adsorption performance of the CuO-CeO2 composites is much better than the materials of CuO and CeO2.

  5. 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.

  6. 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.

  7. Excellent magnetocaloric properties in RE2Cu2Cd (RE = Dy and Tm) compounds and its composite materials

    Science.gov (United States)

    Zhang, Yikun; Yang, Yang; Xu, Xiao; Geng, Shuhua; Hou, Long; Li, Xi; Ren, Zhongming; Wilde, Gerhard

    2016-09-01

    The magnetic properties and magnetocaloric effect (MCE) of ternary intermetallic RE2Cu2Cd (RE = Dy and Tm) compounds and its composite materials have been investigated in detail. Both compounds undergo a paramagnetic to ferromagnetic transition at its own Curie temperatures of TC ~ 48.5 and 15 K for Dy2Cu2Cd and Tm2Cu2Cd, respectively, giving rise to the large reversible MCE. An additionally magnetic transition can be observed around 16 K for Dy2Cu2Cd compound. The maximum values of magnetic entropy change (-ΔSMmax) are estimated to be 17.0 and 20.8 J/kg K for Dy2Cu2Cd and Tm2Cu2Cd, for a magnetic field change of 0-70 kOe, respectively. A table-like MCE in a wide temperature range of 10-70 K and enhanced refrigerant capacity (RC) are achieved in the Dy2Cu2Cd - Tm2Cu2Cd composite materials. For a magnetic field change of 0-50 kOe, the maximum improvements of RC reach 32% and 153%, in comparison with that of individual compound Dy2Cu2Cd and Tm2Cu2Cd. The excellent MCE properties suggest the RE2Cu2Cd (RE = Dy and Tm) and its composite materials could be expected to have effective applications for low temperature magnetic refrigeration.

  8. Microstructure analysis of graphite/Cu joints brazed with (Cu-50TiH{sub 2}) + B composite filler

    Energy Technology Data Exchange (ETDEWEB)

    Mao, Yangwu, E-mail: yangwu.mao@gmail.com [Key Laboratory of Plasma Chemistry and Advanced Materials of Hubei Province, Wuhan Institute of Technology, Wuhan 430073 (China); Yu, Si [Key Laboratory of Plasma Chemistry and Advanced Materials of Hubei Province, Wuhan Institute of Technology, Wuhan 430073 (China); Zhang, Yizhong [Zhuzhou Cemented Carbide Cutting Tools Co., Ltd., Zhuzhou, Hunan 412007 (China); Guo, Beibei; Ma, Zhibin; Deng, Quanrong [Key Laboratory of Plasma Chemistry and Advanced Materials of Hubei Province, Wuhan Institute of Technology, Wuhan 430073 (China)

    2015-11-15

    Highlights: • TiB whiskers are synthesized in situ in the filler layer of graphite/copper joints. • Boron content has a considerable effect on the strength and microstructure of joints. • TiB whiskers could serve as reinforcements, contributing to the improvement of joints. - Abstract: Joining of carbon materials to copper will benefit the fabrication of plasma facing components for fusion applications. Graphite/Cu joints have been prepared by brazing with (Cu-50TiH{sub 2}) + B composite filler in a vacuum. The effect of boron content in the composite filler on the mechanical property and microstructure of brazed graphite/Cu joints has been investigated. The average shear strength of joints increases with boron content raising from 0 to 15 vol%. The maximum average shear strength of 19.8 MPa was obtained with boron content of 15 vol%. Then, the strength of joints decreases with boron content higher than 15 vol%. The microstructure analysis of joints brazed with (Cu-50TiH{sub 2}) + 15 vol% B filler indicates that TiB whiskers have been in situ synthesized in the filler layer. The filler layer is mainly composed of Cu based solid solution and Ti-Cu intermetallic compounds with TiB whiskers distributed inside. The distribution of TiB whiskers in the filler layer could serve as reinforcements, contributing to the improvement of graphite/Cu joints.

  9. 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.

  10. Novel anisotropy in the superconducting gap structure of Bi2Sr2CaCu2O(8+delta) probed by quasiparticle heat transport.

    Science.gov (United States)

    Ando, Yoichi; Takeya, J; Abe, Yasushi; Sun, X F; Lavrov, A N

    2002-04-08

    Since the nature of pairing interactions is manifested in the superconducting gap symmetry, the exact gap structure, particularly any deviation from the simple d(x(2)-y(2)) symmetry, would help in elucidating the pairing mechanism in high- T(c) cuprates. Anisotropic heat transport measurement in Bi(2)Sr(2)CaCu(2)O(8+delta) reveals that the quasiparticle populations are different for the two nodal directions and thus the gap structure must be uniquely anisotropic, suggesting that pairing is governed by interactions with a rather complicated anisotropy. Intriguingly, it is found that the "plateau" in the magnetic-field dependence of the thermal conductivity is observed only in the b-axis transport.

  11. 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.

  12. 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.

  13. Doping-Induced Change of Superconducting Gap Anisotropy in Bi_2Sr_2Ca_1Cu_2O8+δ

    Science.gov (United States)

    Kelley, R. J.; Quitmann, C.; Onellion, M.; Berger, H.; Almeras, P.; Margaritondo, G.

    1996-03-01

    High-resolution angle-resolved photoemission measurements were performed on single crystals of Bi_2Sr_2Ca_1Cu_2O8+δ with different oxygen stoichiometries. The data establish that the gap anisotropy (ratio of the gap along Gamma-M to the gap along Gamma-X) can be reversibly changed from ~20:1 (optimal or underdoped) to ~2:1 (overdoped). Differences in sample doping explain the conflicting reports on gap anisotropy in the literature. Possible effects of this change in gap anisotropy on the symmetry of the order parameter are discussed. There remains some ambiguity as to the relation between the order parameter and doping.

  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. 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.

  16. 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

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. Surface composition deviation of Cu2ZnSnS4 derivative powdered samples

    Science.gov (United States)

    Harel, S.; Guillot-Deudon, C.; Choubrac, L.; Hamon, J.; Lafond, A.

    2014-06-01

    Powdered samples of Cu2ZnSnS4 derivatives prepared through a solid-state route were investigated by both bulk (electron dispersive X-ray spectroscopy) and surface-sensitive (X-ray photoelectron spectroscopy) methods. We observe a deviation in composition between the surface and the bulk for all non-stoichiometric samples (both Cu-poor and Cu-rich). This behavior has already been observed for slightly Cu-poor CZTS thin films and is reminiscent of that of CIGSe compounds.

  4. 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.

  5. 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...

  6. 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.

  7. 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...

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.)

  13. 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.

  14. 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.

  15. 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.

  16. Effect of cationic size in Hg(Tl/Bi)Ba2Ca2Cu3O8+ on superconducting and microstructural characteristics

    Indian Academy of Sciences (India)

    Rajiv Giri; H K Singh; R S Tiwari; O N Srivastava

    2001-10-01

    In this paper we have reported investigations on the effect of simultaneous substitution of Bi and Tl at the H site in the oxygen deficient HO layer of HBa2Ca2Cu3O8+ cuprate superconductor. Bulk polycrystalline samples have been prepared by the two-step solid state reaction process (precursor route). It has been observed that the as grown HBi0.2–TlBa2Ca2Cu3O8+ (with = 0.00, 0.05, 0.10, 0.15, 0.20) corresponds to the 1223 phase. It has been found that the c varies with the average cationic size $\\langle R_d \\rangle$ of the dopantcations. The optimum c of ∼ 131 K has been found for the composition HBi0.15Tl0.05Ba2Ca2Cu3O8+. This composition leads to the average dopant cation size of ∼ 1.108 Å which is very close to the size of H2+ (∼ 1.11 Å). The microstructure for HBi0.15Tl0.05Ba2Ca2Cu3O8+ has been found to be most dense and this phase exhibits the highest stability. The c of the optimum material HBi0.15Tl0.05Ba2Ca2Cu3O8+ is found to be ∼ 1.29 × 103 A/cm2 at 77 K.

  17. Anelastic characterization and superconducting properties of RuSr2GdCu2O8+δ

    Directory of Open Access Journals (Sweden)

    Jurelo, A. R.

    2008-08-01

    Full Text Available Since the discovery of the high Tc superconductors, many researches have been carried out on the different properties of these materials, especially on the transition temperature into the superconducting state. The rutheno-cuprates belong to a new class of composites, which were synthesized for the first time by Bauernfeind in 1995. Bernhard and collaborators discovered, in 1999, the coexistence of the ferromagnetism and the superconductivity in this phase, which is known as antagonistic phenomenon in the electromagnetism due to spin-charge interactions established in these states. However, the physical nature of the superconducting and magnetic states is still very obscure. The non-stoichiometric (interstitial oxygen is considered as a possible cause for the non-uniformity of the sample properties. In this paper, results of mechanical spectroscopy in Ru-1212 samples are presented showing complex anelastic spectra, which were attributed to the mobility of the interstitial oxygen atoms in the Ru-1212 lattice.Desde el descubrimiento de los superconductores de alta Tc, muchas investigaciones han sido realizadas sobre las diferentes propiedades de estos materiales, especialmente sobre la temperatura de transición dentro del estado superconductor. Los cupratos de rutenio pertenecen a una nueva clase de compositos, los cuales fueron sintetizados por primera vez por Bauernfeind en 1995. Bernhard y colaboradores descubrieron, en 1999, la coexistencia del ferromagnetismo y la superconductividad en esta fase, lo cual es conocido como un fenómeno antagonistico en el electromagnetismo debido a las interacciones spin-carga establecidas en estos estados. Sin embargo, la naturaleza física de los estados superconductores y magnéticos aun no son muy claros. El oxigeno no-estequiométrico (intersticial es considerado como una causa de la no-uniformidad de las propiedades de la muestra. En este articulo, los resultados de espectroscopia mecánica en muestras

  18. Dynamics of the superconducting mixed state in YBa2Cu3O7-/PrBa2Cu3O7- superlattices in radio frequency regime

    Indian Academy of Sciences (India)

    K Senapati; R C Budhani

    2002-05-01

    Epitaxial multilayers of YBa2Cu3O7- and PrBa2Cu3O7- have been deposited on (100) cut SrTiO3 substrates using the technique of pulsed laser deposition. Standard -2 X-ray diffraction measurements on the films showed excellent superlattice reflections. The mixed state of these superlattices has been probed through measurements of radio frequency penetration depth () as a function of temperature (), magnetic field () and it’s orientation () with respect to the planes of the superlattices. These data reflect the two-dimensional nature of the mixed state in these systems.

  19. 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.

  20. Tribological properties of Cu-La2O3 composite under different electrical currents

    Institute of Scientific and Technical Information of China (English)

    ZHENG Runguo; ZHAN Zaiji; WANG Wenkui

    2011-01-01

    A new type of Cu-La2O3 composite was fabricated by internal oxidation method using powder metallurgy. Sliding wear behavior of the Cu-La2O3 composite was studied on a pin-on-disc wear tester under various electrical currents and applied loads. The worn surfaces were characterized using scanning electron microscopy and energy dispersive spectroscopy to probe the wear mechanisms. The results indicated that applied load had a significant effect on the wear rate of the Cu-La2O3 composite pins. The wear rate displayed the minimum value at the load of 50 N during electrical sliding processes. The corresponding wear mechanism was identified to be adhesive wear, abrasive wear,oxidation wear and arc erosion.

  1. 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.

  2. 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.

  3. Spectral weight changes 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.; Shen, Z.X.; Wells, B.O.; Spicer, W.E. (Stanford Univ., CA (United States). Stanford Electronics Labs.); Arko, A.J. (Los Alamos National Lab., NM (United States))

    1991-01-01

    An overview of our gap studies in high-{Tc} superconductors is presented for the workshop on Fermiology of high-{Tc}'s. The work is centered on the study of single crystal Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}}. In a conventional BCS superconductor, a superconducting gap {Delta} is formed when the near Fermi edge electrons condense to form Cooper pairs at low temperatures. As the material goes superconducting the density of states is modified such that the spectral intensity in the region from the Fermi energy down to an energy {Delta} is transferred to a regions just below {Delta}. While this spectral weight transfer has in the past been studied with tunneling spectroscopy, the size of the gap as well as improvements in our instrument resolution allow us now to study it with photoelectron spectroscopy. We have found that as the sample goes superconducting, not only is there spectral weight transfer from the gap region as in BCS theory, but along the {Gamma}-M direction there is also some spectral weight transfer from higher binding energies resulting in a dspectral dip at about {minus}90 meV relative E{sub F}. The total spectral weight decreases along the {Gamma}-M direction, but actually increases along the {Gamma}-X direction. This temperature dependent spectral transfer is discussed in terms of (1) a two to three dimensional phase transition from RVB theory; (2) a manifestation of the electron-boson interaction in the form of {alpha}{sup 2}F oscillations; and (3) conformity with the theory of Van Hove singularities. The latter are particularly attractive in that there are several other observations possibly explained by them: (1) the observation that the magnitude of the gap is anisotropic in the a-b plane; (2) the observation that for overdoped samples the magnitude of D appears to fall off faster then {Tc}. 25 refs., 8 figs., 1 tab.

  4. 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.

  5. 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.)

  6. 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.

  7. 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.

  8. The effect of composition on structural and electronic properties in polycrystalline CuGaSe2 thin film

    Institute of Scientific and Technical Information of China (English)

    Zhang Li; He Qing; Xu Chuan-Ming; Xue Yu-Ming; Li Chang-Jian; Sun Yun

    2008-01-01

    Polycrystalline CuGaSe2 thin films on Mo-coated soda-lime glass substrates have been synthesized by co-evaporation process from Cu, Ga and Se sources. Structural and electrical properties of the as-grown CuGaSe2 films strongly depend on the film composition. Stoichiometric CuGaSe2 is fabricated, as indicated by x-ray diffraction spec-troscope (XRD) and x-ray fluorescence (XRF). A two-phase region is composed of CuGaSe2 and Cu2-xSe phases for Cu-rich films, and CuGaSe2 and CuGa3Se5 phases for Ga-rich films, respectively. Morphological properties are de-tected by scanning electron microscope (SEM) for various compositional films, the grain sizes of the CuGaSe2films decrease with the extent of deviation from stoichiometric composition. Raman spectroscopy of Cu-rich samples shows that there exist large Cu-Se particles on the film surface. The results from Hall effect measurements for typical samples indicate that CuGaSe2 films are always of p-type semiconductor from Cu-rich to Ga-rich. Stoichiometric CuGaSe2 films exhibit relatively large mobility than any other compositional films. Finally, polycrystalline CuGaSe2 thin film solar cell with a best conversion efficiency of 6.02% has been achieved under the standard air mass (AM)1.5 spectrum for 100 mW/cm2 at room temperature (aperture area, 0.24cm2). The open circuit voltage of the CuGaSe2 solar cells is close to770 mV.

  9. 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.

  10. 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.

  11. Emergent loop-nodal s(±)-wave superconductivity in CeCu(2)Si(2): similarities to the iron-based superconductors.

    Science.gov (United States)

    Ikeda, Hiroaki; Suzuki, Michi-To; Arita, Ryotaro

    2015-04-10

    Heavy-fermion superconductors are prime candidates for novel electron-pairing states due to the spin-orbital coupled degrees of freedom and electron correlations. Superconductivity in CeCu_{2}Si_{2} discovered in 1979, which is a prototype of unconventional (non-BCS) superconductors in strongly correlated electron systems, still remains unsolved. Here we provide the first report of superconductivity based on the advanced first-principles theoretical approach. We find that the promising candidate is an s_{±}-wave state with loop-shaped nodes on the Fermi surface, different from the widely expected line-nodal d-wave state. The dominant pairing glue is magnetic but high-rank octupole fluctuations. This system shares the importance of multiorbital degrees of freedom with the iron-based superconductors. Our findings reveal not only the long-standing puzzle in this material, but also urge us to reconsider the pairing states and mechanisms in all heavy-fermion superconductors.

  12. 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.

  13. 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.

  14. 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.

  15. Composition-dependent nanostructure of Cu(In,Ga)Se{sub 2} powders and thin films

    Energy Technology Data Exchange (ETDEWEB)

    Schnohr, C.S., E-mail: c.schnohr@uni-jena.de [Institut für Festkörperphysik, Friedrich-Schiller-Universität Jena, Max-Wien-Platz 1, 07743 Jena (Germany); Kämmer, H.; Steinbach, T.; Gnauck, M. [Institut für Festkörperphysik, Friedrich-Schiller-Universität Jena, Max-Wien-Platz 1, 07743 Jena (Germany); Rissom, T.; Kaufmann, C.A.; Stephan, C. [Helmholtz-Zentrum Berlin für Materialien und Energie, Hahn-Meitner-Platz 1, 14109 Berlin (Germany); Schorr, S. [Helmholtz-Zentrum Berlin für Materialien und Energie, Hahn-Meitner-Platz 1, 14109 Berlin (Germany); Institut für Geologische Wissenschaften, Freie Universität Berlin, Malteserstr. 74-100, 12249 Berlin (Germany)

    2015-05-01

    Atomic-scale structural parameters of Cu(In,Ga)Se{sub 2} powders and polycrystalline thin films were determined as a function of the In and Cu contents using X-ray absorption spectroscopy. No difference in the two sample types is observed for the average bond lengths demonstrating the strong tendency towards bond length conservation typical for tetrahedrally coordinated semiconductors. In contrast, the bond length variation is significantly smaller in the thin films than in the powders, particularly for Cu-poor material. This difference in the nanostructure is proposed to originate from differences in the preparation conditions, most prominently from the different history of Cu composition. - Highlights: • Cu(In,Ga)Se{sub 2} powders and thin films are studied with X-ray absorption spectroscopy. • Structural parameters are determined as a function of the In and Cu contents. • The element-specific average bond lengths are identical for powders and thin films. • The Ga-Se/In-Se bond length variation is smaller for thin films than for powders. • The differences are believed to stem from the different history of the Cu content.

  16. 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.

  17. 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)

  18. 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.

  19. 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).

  20. 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.

  1. 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.

  2. 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)

  3. 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.)

  4. Synthesis and characterization of ion transport behavior in Cu2+-conducting nano composite polymer electrolyte membranes

    Science.gov (United States)

    Bala Sahu, Tripti; Sahu, Manju; Karan, Shrabani; Mahipal, Y. K.; Sahu, D. K.; Agrawal, R. C.

    2017-07-01

    Synthesis and characterization of ion transport behavior in Cu2+-conducting nano composite polymer electrolyte (NCPE) films: [90PEO: 10Cu(CF3SO3)2]  +  x CuO have been reported. NCPE films have been formed by hot-press casting technique using solid polymer electrolyte (SPE) film composition: [90PEO: 10Cu(CF3SO3)2] as 1st-phase host and nanoparticles of CuO in varying wt.(%) as 2nd-phase active filler. SPE: [90PEO: 10Cu(CF3SO3)2] was identified earlier as highest conducting film with room temperature conductivity (σ rt) ~ 3.0 x 10-6 S cm-1, which is three orders of magnitude higher than that of pure polymer host PEO with σ rt ~ 3.2  ×  10-9 S cm-1. Filler particle concentration dependent conductivity study revealed NCPE film: [90PEO: 10Cu(CF3SO3)2]  +  3%CuO as optimum conducting composition (OCC) exhibiting σ rt ~ 1.14  ×  10-5 S cm-1. Hence, by the fractional dispersal of 2nd-phase active filler into 1st-phase SPE host, σ-enhancement of approximately an order of magnitude has further been obtained. Ion transport behavior in NCPE OCC film has been characterized in terms of basic ionic parameters viz. ionic conductivity (σ), total ionic transference (t ion)/cationic (t +) numbers. Temperature dependent conductivity measurement has also been done to explain the mechanism of ion transport and to compute activation energy (E a). Materials characterization and hence, confirmation of complexation of salt in polymeric host and/or dispersal of filler particles in SPE host have been done by scanning electron microscopy (SEM), energy dispersive x-ray spectrometer (EDS), x-ray diffraction (XRD), Fourier transform infra-red (FTIR), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). All-solid-state battery in the cell configuration: Cu (Anode) || SPE host/NCPE OCC film || C  +  I2  +  Electrolyte) (Cathode) has been fabricated and cell performance has been studied under two load resistances viz

  5. On the magnetization relaxation of ring-shaped Tl 2Ba 2CaCu 2O 8 thin films as determined by superconducting quantum interference device measurements

    Science.gov (United States)

    Wen, Hai-hu; Ziemann, Paul; Radovan, Henri A.; Herzog, Thomas

    1998-09-01

    By using a superconducting quantum interference device (SQUID), the temporal relaxation of the magnetization was determined for ring-shaped Tl 2Ba 2CaCu 2O 8 thin films at various temperatures between 10 K and 80 K in magnetic fields ranging from 2 mT to 0.3 T. Based on these data, a detailed analysis has been performed related to the following methods or models: (1) Fitting the data to the thermally activated flux motion and collective pinning model; (2) Applying the Generalized Inversion Scheme to extract the temperature dependence of the unrelaxed critical current density jc( T) and pinning potential Uc( T); (3) Testing a modified Maley's method to obtain the current dependent activation energy for flux motion; (4) 2D vortex glass scaling. It is found that, for low fields (2 mT, 10 mT, 40 mT) the experimental data can be described by an elastic flux motion, most probably due to 3D single vortex creep. At higher fields (0.1 T, 0.2 T, 0.3 T), the observed behavior can be interpreted in terms of plastic flux motion which is probably governed by dislocation mediated flux creep. These high field data can also be consistently described by the 2D vortex glass scaling with scaling parameters ν2D, T0 and p being consistent with those derived from corresponding transport measurement. Also, results are presented demonstrating the importance of optimizing the scan length of the sample in a moving sample SQUID magnetometer to avoid artifacts.

  6. 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...

  7. 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.

  8. 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)

  9. Tuning the charge density wave and superconductivity in CuxTaS2

    NARCIS (Netherlands)

    Wagner, K.E.; Morosan, E.; Hor, Y.S.; Tao, J.; Zhu, Y.; Sanders, T.; McQueen, T.M.; Zandbergen, H.W.; Williams, A.J.; West, D.V.; Cava, R.J.

    2008-01-01

    We report the characterization of layered 2H-type CuxTaS2 for 0≤x≤0.12. The charge density wave (CDW), at 70 K for TaS2, is destabilized with Cu doping. The sub-1 K superconducting transition in undoped 2H-TaS2 jumps quickly to 2.5 K at low x, increases to 4.5 K at the optimal composition Cu0.04TaS2

  10. 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.

  11. 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.

  12. 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.

  13. Effect of the fluorine substitution on superconducting properties for the multi-layered Ba{sub 2}Ca{sub n-1}Cu{sub n}O{sub 2n}(O, F){sub 2} (n = 5)

    Energy Technology Data Exchange (ETDEWEB)

    Kito, Hijiri [National Institute of Advanced Industrial Science and Technology (A.I.S.T), Tsukuba Central 2, 1-1-1, Umezono, Tsukuba, Ibaraki 305-8568 (Japan)], E-mail: h.kito@aist.go.jp; Iyo, Akira [National Institute of Advanced Industrial Science and Technology (A.I.S.T), Tsukuba Central 2, 1-1-1, Umezono, Tsukuba, Ibaraki 305-8568 (Japan)

    2008-09-15

    We prepared multi-layered oxyfluoride superconductors, Ba{sub 2}Ca{sub n-1}Cu{sub n}O{sub 2n}(O{sub 2-y}F{sub y}){sub 2} (n = 5: 0245-F{sub y}) using high-pressure apparatus. This phase is the n = 5 members of a homologous series, M{sub 2}Ca{sub n-1}Cu{sub n}O{sub 2n}(O,F){sub 2} [0{sup M}2(n-1)n-F] reported previously. Superconducting transition temperature were 80.1 K for the nominal composition y = 1.3, 75.7 K for y = 1.4 and 54.0 K for y = 2.0, respectively. X-ray studies indicated that they have tetragonal structures with structures. The critical current density (J{sub c}) and irreversibility field (H{sub irr}) were determined from M-H curves using the Bean's model. J{sub c} and H{sub irr} of 0245-F decreased rapidly with increasing temperature. J{sub c} (5 K, 1 T) shows 1.93 x 10{sup 5} A/cm{sup 2} for y = 1.4 and 5.15 x 10{sup 4} A/cm{sup 2} for y = 2.0, and the estimated values of H{sub irr} (5 K) are about 17 T(y = 1.4). The relationship between the hole-doping level and the J{sub c} and the H{sub irr} vs. (1-T/T{sub c}) characteristics is discussed.

  14. 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.

  15. 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.

  16. 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.

  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. 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.

  19. 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.)

  20. Dopant rearrangement and superconductivity in Bi(2)Sr(2-x)La(x)CuO(6) thin films under annealing.

    Science.gov (United States)

    Cancellieri, C; Lin, P H; Ariosa, D; Pavuna, D

    2007-06-20

    By combining x-ray diffraction (XRD), x-ray photoemission spectroscopy (XPS) and AC susceptibility measurements we investigate the evolution of structural and superconducting properties of La-doped Bi-2201 thin films grown by pulsed laser deposition (PLD) under different annealing conditions. We find that the main effect of oxygen annealing is to improve the crystal coherence by enabling La cation migration to the Sr sites. This activates the desired hole doping. Short-time Ar annealing removes the interstitial oxygen between the BiO layers, fine adjusting the effective hole doping. The superconducting critical temperature is consequently enhanced. However, longer annealings result in phase separation and segregation of the homologous compound Bi-1201. We attribute this effect to the loss of Bi during the annealing.

  1. Dopant rearrangement and superconductivity in Bi2Sr2-xLaxCuO6 thin films under annealing

    Science.gov (United States)

    Cancellieri, C.; Lin, P. H.; Ariosa, D.; Pavuna, D.

    2007-06-01

    By combining x-ray diffraction (XRD), x-ray photoemission spectroscopy (XPS) and AC susceptibility measurements we investigate the evolution of structural and superconducting properties of La-doped Bi-2201 thin films grown by pulsed laser deposition (PLD) under different annealing conditions. We find that the main effect of oxygen annealing is to improve the crystal coherence by enabling La cation migration to the Sr sites. This activates the desired hole doping. Short-time Ar annealing removes the interstitial oxygen between the BiO layers, fine adjusting the effective hole doping. The superconducting critical temperature is consequently enhanced. However, longer annealings result in phase separation and segregation of the homologous compound Bi-1201. We attribute this effect to the loss of Bi during the annealing.

  2. Anisotropic photoelectric film assembled from mesoporous silica (MS)@CuO@FeS2 composite microspheres for improving photoelectric conversion.

    Science.gov (United States)

    Zong, Jie; Zhu, Yihua; Shen, Jianhua; Yang, Xiaoling; Li, Chunzhong

    2013-07-15

    We report a novel strategy for the fabrication of mesoporous silica (MS)@CuO@FeS2 composite microsphere-based anisotropic films that combine the advantages of the CuO and FeS2 materials to improve photoelectric conversion. This was achieved by aligning MS@CuO@FeS2 composite microspheres in a cross-linked gel under a homogeneous magnetic field. The MS@CuO@FeS2 composite microspheres, which were synthesized by a simple layer-by-layer (LbL) self-assembly technique together with a solvothermal method, can absorb a wide range of light and exhibit ferromagnetic properties. In addition, the resulting MS@CuO@FeS2 composite microsphere-based anisotropic film shows photoelectric anisotropy. Such systems are promising for improving the performance of solar cells.

  3. Electrical potential distribution in terahertz-emitting rectangular mesa devices of high- T c superconducting Bi2Sr2CaCu2O{}_{8+\\delta }

    Science.gov (United States)

    Watanabe, Chiharu; Minami, Hidetoshi; Kitamura, Takeo; Saiwai, Yoshihiko; Shibano, Yuki; Katsuragawa, Takuya; Kubo, Hiroyuki; Sakamoto, Kazuki; Kashiwagi, Takanari; Klemm, Richard A.; Kadowaki, Kazuo

    2016-06-01

    Excessive Joule heating of conventional rectangular mesa devices of the high-transition-temperature {T}{{c}} superconductor Bi2Sr2CaCu2O{}8+δ leads to hot spots, in which the local temperature T({\\boldsymbol{r}})\\gt {T}{{c}}. Similar devices without hot spots are known to obey the ac-Josephson relation, emitting sub-terahertz (THz) waves at frequencies f\\propto V/N, where V is the applied dc voltage or electrostatic potential and N is the number of active junctions in the device. However, it often has been difficult to predict the emission f from the applied V for two reasons: N is generally unknown and therefore has been assumed to be a fitting parameter, and especially when hot spots are present, V could develop a spatial dependence that cannot be accurately determined using two-terminal measurements. To clarify the situation, simultaneous SiC microcrystalline photoluminescence measurements of T({\\boldsymbol{r}}), Fourier-transform infrared (FTIR) measurements of f, and both two and four-terminal measurements of the local V({\\boldsymbol{r}}) were performed. The present four-probe measurements provide strong evidence that when a constant V is measured within the device's superconducting region outside of the hot spot, the only requirement for the accuracy of the ac-Josephson relation is the ubiquitous adjustment of the fitting parameter N. The four-probe measurements demonstrate that the electric potential distribution is strongly non-uniform near to the hot spot, but is essentially uniform sufficiently far from it. As expected, the emission frequency follows the ac-Josephson relation correctly even for low bath temperatures at which the system jumps to inner IV characteristic branches with smaller N values, reconfirming the ac-Josephson effect as the primary mechanism for the sub-THz emission.

  4. 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*.

  5. 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.

  6. 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.

  7. Metal-organic framework derived porous CuO/Cu2O composite hollow octahedrons as high performance anode materials for sodium ion batteries.

    Science.gov (United States)

    Zhang, Xiaojie; Qin, Wei; Li, Dongsheng; Yan, Dong; Hu, Bingwen; Sun, Zhuo; Pan, Likun

    2015-11-25

    Porous CuO/Cu2O composite hollow octahedrons were synthesized simply by annealing Cu-based metal-organic framework templates. When evaluated as anode materials for sodium ion batteries, they exhibit a high maximum reversible capacity of 415 mA h g(-1) after 50 cycles at 50 mA g(-1) with excellent cycling stability and good rate capability.

  8. Structure and composition of the superconducting phase in alkali iron selenide KyFe1.6+xSe2

    Science.gov (United States)

    Carr, Scott V.; Louca, Despina; Siewenie, Joan; Huang, Q.; Wang, Aifeng; Chen, Xianhui; Dai, Pengcheng

    2014-04-01

    We use neutron diffraction to study the temperature evolution of the average structure and local lattice distortions in insulating and superconducting potassium iron selenide KyFe1.6+xSe2. In the high temperature paramagnetic state, both materials have a single phase with a crystal structure similar to that of the BaFe2As2 family of iron pnictides. While the insulating KyFe1.6+xSe2 forms a √5 ×√5 iron vacancy ordered block antiferromagnetic (AF) structure at low temperature, the superconducting compounds spontaneously phase separate into an insulating part with √5 ×√5 iron vacancy order and a superconducting phase with chemical composition of KzFe2Se2 and BaFe2As2 structure. Therefore, superconductivity in alkaline iron selenides arises from alkali deficient KzFe2Se2 in the matrix of the insulating block AF phase.

  9. 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).

  10. Nanomechanical properties and thermal decomposition of Cu-Al2O3 composites for FGM applications

    Directory of Open Access Journals (Sweden)

    Koumoulos Elias P.

    2016-01-01

    Full Text Available It is widely reported that copper-alumina (Cu-Al2O3 nanocomposite materials exhibit high potential for use in structural applications in which enhanced mechanical characteristics are required. The investigation of Cu-Al2O3 nanocomposites which are to form a functionally graded material (FGM structure in terms of nanomechanical/structural integrity and thermal stability is still scarce. In this work, fully characterized nanosized Al2O3 powder has been incorporated in Cu matrix in various compositions (2, 5 and 10 wt.% of Al2O3 content. The produced composites were evaluated in terms of their morphology, structural analysis, thermal behavior, nanomechanical properties and their extent of viscoplasticity. The results reveal that all nanocomposites degrade at elevated temperatures; increased surface mass gain with decreasing Al2O3 content was observed, while no such difference of % mass gain in 5 and 10 wt.% of Al and Al2O3 content in Cu was observed. The increase of Al2O3 wt.% content results in thermal stability enhancement of the nanocomposites. The thermal decomposition process of the material is reduced in the presence of 10 wt.% of Al2O3 content. This result for the matrix decomposition can be explained by a decrease in the diffusion of oxygen and volatile degradation products throughout the composite material due to the incorporation of Al and Al2O3. The Al2O3 powder enhances the overall thermal stability of the system. All samples exhibited significant pile-up of the materials after nanoindentation testing. Increasing the wt.% of Al2O3 content was found to increase the creep deformation of the samples as well as the hardness and elastic modulus values.

  11. 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...

  12. White-light-controlled resistive switching chearacteristics of TiO2/Cu2O composite nanorods array

    Science.gov (United States)

    Sun, Bai; Liu, Yonghong; Lou, Fangming; Chen, Peng

    2015-08-01

    TiO2/Cu2O composite nanorods array were grown on fluorine-doped tin oxide (FTO) substrate by hydrothermal process, and white-light-controlled resistive switching characteristics of Ag/[TiO2/Cu2O]/FTO structure were further investigated. The current-voltage characteristics of the composite nanorods array represent a good rectifying property and bipolar resistive switching behavior. Specially, the resistive switching behavior can be regulated by white-light illuminating at room temperature. This study is helpful for exploring the memory materials and their applications in nonvolatile light-controlled memory devices.

  13. Effects of out-of-plane disorder on the superconductivity of Bi{sub 2}Sr{sub 2-x}La{sub x}CuO{sub 6+{delta}}

    Energy Technology Data Exchange (ETDEWEB)

    Roehler, Juergen; Trabant, Christoph; Frielingsdorf, Johanna; Djemour, Rabia [Universitaet Koeln, 50937 Koeln (Germany); Martovitsky, Victor [Lebedev-Institute, 119991 Moscow (Russian Federation); Dudy, Lenart; Dwelk, Helmut; Krapf, Alica [Humboldt Universitaet Berlin, 12489 Berlin (Germany)

    2008-07-01

    The effects of out-of-plane substitutional order/disorder on cuprate superconductivity remains to a large extent an unresolved issue. We have investigated the connection between superconductivity and the lattice effects arising from the heterovalent doping of Bi{sub 2}Sr{sub 2-x}La{sub x}CuO{sub 6+{delta}}, x = 0.8-0.1. Decreasing lanthanum content tunes the compound through the entire underdoped and overdoped regimes. Cu-K and La- K EXAFS served as local structural probes, and single crystal X-ray diffraction for the determination of the basic unit cell, and the symmetry of the supercell. The oxygen atoms in the CuO{sub 2} planes were found significantly disordered, dependent on doping, and to exhibit minimum disorder around x{sub opt}=0.33. But the degree of substitutional disorder in the out-of-plane La environment turned out independent on the concentration of the La dopants, the superstructure symmetry, and the crystal growth parameters, whereas T{sub c} depends sensitively on them. No evidence was found for possible concentration dependent site changes of the La dopant from the nominal Sr to the Bi sites. We discuss the probably crucial role of the interstitial oxygen atoms for the superconducting properties of the Bi{sub 2}Sr{sub 2-x}La{sub x}CuO{sub 6+{delta}} system.

  14. 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.

  15. Large area superconducting YBa 2Cu 3O 7-x films grown by single target ion beam sputtering

    Science.gov (United States)

    Gauzzi, Andrea; Lucía, Maria L.; Kellett, Bruce J.; James, Jonathan H.; Pavuna, Davor

    1991-10-01

    We have demonstrated, by using a simple single YBa 2Cu 3O 7- x target ion beam system that, with a sufficiently low power ion beam, preferential sputtering is avoided and high-quality YBa 2Cu 3O 7- x films are deposited over areas larger than ≈ 30 cm 2 in a reproducible way. As-deposited films on SrTiO 3 are 50-100 nmthick, c-oriented and show the following reproducible electrical properties (within the given variations): Tc0 =90±0.5 K, transitions widths less than 1 K, j inc(77 K)=1.0-1.2× 10 6 A cm -2, ϱ(300 K)=300±50μΩ cm, ϱ(300 K)/ ϱ(100 K)=2.9±0.1. The extrapolated residual resistivity ϱ res(O K) is between 0 and 5% of ϱ(300 K).

  16. 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.

  17. ab-plane optical spectra of iodine-intercalated Bi1.9Pb0.1Sr2CaCu2O8+δ: Normal and superconducting properties

    Science.gov (United States)

    Liu, H. L.; Tanner, D. B.; Berger, H.; Margaritondo, G.

    1999-04-01

    We report on the ab-plane optical reflectance of an iodine-intercalated Bi1.9Pb0.1Sr2CaCu2O8+δ single crystal in the 80-40 000 cm-1 (10 meV-5 eV) frequency range and at temperatures between 10 and 300 K. As compared to the iodine-free Bi2Sr2CaCu2O8+δ, we find that the visible-ultraviolet interband transitions are strongly modified after intercalation. Estimates of the low-frequency spectral weight indicate that there is an increase of hole concentration in the CuO2 planes. This behavior is a consequence of charge transfer between intercalated iodine atoms and the CuO2 sheets leading to an ionized iodine species. The ab-plane optical conductivity is analyzed in both the one-component and the two-component pictures, suggesting that the intercalated iodine does not have any significant effect on the in-plane scattering rate. In the superconducting state, a sum-rule evaluation finds that the superfluid contains about 25% of the total doping-induced, or nearly 86% of the free-carrier oscillator strength in the normal state. The value of the superconducting penetration depth is estimated to be 1980 Å, slightly larger than the 1860 Å found in iodine-free Bi2Sr2CaCu2O8+δ.

  18. One-pot self-assembly of Cu2O/RGO composite aerogel for aqueous photocatalysis

    Science.gov (United States)

    Cai, Jingyu; Liu, Wenjun; Li, Zhaohui

    2015-12-01

    Cu2O/reduced graphene oxide (RGO) composite aerogel was fabricated by a one-pot hydrothermal method using glucose as a reducing agent and cross-linker. The as-obtained Cu2O/RGO composite aerogel showed superior photocatalytic activity for MO degradation owing to its improved light absorption capability, enhanced adsorption toward pollutant and the RGO promoted charge carrier separation. The Cu2O/RGO composite aerogel can also be facilely separated from the reaction system for recycling, which makes it especially appealing for using as a visible light responsive photocatalyst in aqueous photocatalysis.

  19. Electrokinetic and bioactive properties of CuO∙SiO2 oxide composites.

    Science.gov (United States)

    Nowacka, Magdalena; Modrzejewska-Sikorska, Anna; Chrzanowski, Lukasz; Ambrożewicz, Damian; Rozmanowski, Tomasz; Myszka, Kamila; Czaczyk, Katarzyna; Bula, Karol; Jesionowski, Teofil

    2012-10-01

    CuO∙SiO(2) hybrid oxide precipitated on a semi-technical scale was thoroughly characterised in terms of physicochemical properties. Its particle size distribution and SEM analysis were performed to establish dispersion and surface morphology. Chemical analysis provided information on the content of CuO and SiO(2) oxides in the hybrid systems. The oxide systems were also subjected to elemental analysis. Zeta potential determinations were evaluated to obtain information regarding the interactions between colloidal particles. The stability of copper silicates' water dispersions was estimated on the basis of zeta potential measurements. The obtained oxide systems were used as components of polymer composites with polyester resins, which were subjected to mechanical tests and bactericidal tests against Pseudomonas aeruginosa, a well known biofilm-forming microorganism. The anti-adhesive activity of the CuO·SiO(2) enriched polymers was assessed using a 9-degree scale of adhesion. A significant reduction in the P. aeruginosa biofilm development rate was achieved for Palatal A 400-01 resins enriched with both 2 and 8 phr of the filler. In the case of Aropol M 105 TB resins the introduction of CuO∙SiO(2) caused inhibition of bacterial colonisation but to a smaller extent. These results strongly indicate that the biological activity of Cu was maintained. The release of copper ions into the local environment was examined by atomic absorption spectrometry (AAS). Maximum values of 1.621 and 5.934 mg/dm(3) of released copper were detected. The surface composition of both resins studied by energy dispersive X-ray spectroscopy (EDS) contributed to the data suggesting homogenous distribution of Si; however copper seemed to form local aggregates. The presented results may be of great significance for those dealing with materials tailored for specific needs.

  20. 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

  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. Metal-Insulator Transition and Superconductivity in Y1-xPr(Ce)xBa2Cu3O7

    Institute of Scientific and Technical Information of China (English)

    韩汝珊; 苏肇冰; 王玉鹏

    1994-01-01

    To interpret the metal-insulator transition and depression of Tc induced by Pr-and Ce-doping in YBa2Cu3O7, we propose a model of mixed local hole states which describe a strong admixture of 4f1 state with states of 4f2 plus a hole in the CuO2 planes for Y1-x-Prx-07 and 4f0 state with states of 4f1 plus a hole in Y1-xCex-O7. Our model resolves the controversy between the magnetic and spectroscopic measurements. As a natural consequence, most of the experimental results on Y1-xPrx-O7 can be explained and certain properties of Y1-xCex-O7 are predicted. The critical doping density of Pr will take the value of xc ≈0.5.

  3. Phenomenology and sign change of the Hall resistivity near the superconducting transition of polycrystalline DyBa{sub 2}Cu{sub 3}O{sub 7-{delta}}

    Energy Technology Data Exchange (ETDEWEB)

    Roa-Rojas, J. [Rio Grande do Sul Univ., Porto Alegre (Brazil). Inst. de Fisica; Escuela Colombiana de Ingenieria, Santafe de Bogota (Colombia); Landinez Tellez, D.A. [Pernambuco Univ., Recife (Brazil). Dept. de Fisica; Pureur, P. [Rio Grande do Sul Univ., Porto Alegre (Brazil). Inst. de Fisica

    2000-07-01

    Measurements of the temperature dependence of the electrical resistivity and the Hall effect in the normal and superconducting states of a ceramic DyBa{sub 2}Cu{sub 3}O{sub 7-{delta}} superconductor are reported. In high temperatures the diagonal resistivity is proportional to T, whereas the Hall response exhibits a 1/T dependence and the cotangent of the Hall angle is proportional to T{sup 2}. Upon decreasing the temperature, the Hall response shows a sign reversal close to T{sub c}, goes through a negative maximum and vanishes close to the so-called zero-resistance temperature. The aim of this report is to show that the sign change occurs in the temperature region dominated by thermal fluctuations in the order parameter. (orig.)

  4. Superconducting Bi1.5Pb0.5Sr2Ca2Cu3O(x) ceramics by rapid melt quenching and glass crystallization

    Science.gov (United States)

    Bansal, Narottam P.

    1989-01-01

    A glass of nominal Bi(1.5)Pb(0.5)Sr2Ca2Cu3O(x) composition, prepared by rapid quenching of the melt, showed a glass transition temperature of 383 C, crystallization temperature of 446 C, melting temperature of 855 C, and bulk density of 5.69 g/cu cm in air. The activation energy for crystallization of the glass was estimated to be 292kJ/mol from non-isothermal DSC. On heating in oxygen, the glass showed a slow and continuous weight gain starting at approximately 530 C which reached a plateau at approximately 820 C. The weight gained during heating was retained on cooling to ambient conditions indicating an irreversible oxidation step. The influence of annealing conditions on the formation of various phases in the glass has been investigated. The Bi(2)Sr(2)Ca(0)Cu(1)O(6) phase crystallized out first followed by formation of other phases at higher temperatures. The high-T(sub c) phase, isostructural with Bi(2)Sr(2)Ca(2)Cu(3)O(10) was not detected below 840 C, but its fraction increased with the annealing time at 840 C. A sample annealed at 840 C for 243h in air and furnace cooled showed the highest T(sub c)(R=0) of 107.2K and a narrow transition width, delta T(sub c)(10 to 90 percent), of approximately 2 K. The high T(sub c) phase does not seem to crystallize out directly from the glass but is rather produced at high temperature by reaction between the phases formed at lower temperatures. The kinetics of 110K phase formation was sluggish. It appears that the presence of lead helps in the formation and/or stabilization of the 110 K phase.

  5. 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.

  6. Nodal and nodeless gap in proximity-induced superconductivity: Application to monolayer CuO2 on a Bi2Sr2CaCu2O8 +δ substrate

    Science.gov (United States)

    Wang, Yimeng; Wang, Zhen-Hua; Chen, Wei-Qiang

    2017-09-01

    We present a detailed analysis on the hopping between monolayer CuO2 and bulk CuO2 plane in the Bi2Sr2CaCu2O8 +δ substrate. With a two-band model, we demonstrate that the nodeless gap can only exist when the hole concentration in the monolayer CuO2 plane is very large. We argue that the possible phase separation may play an important role in the recent experimental observation of a nodeless gap.

  7. Large critical current densities and pinning forces in CSD-grown superconducting GdBa2Cu3O7-x -BaHfO3 nanocomposite films

    Science.gov (United States)

    Cayado, Pablo; Erbe, Manuela; Kauffmann-Weiss, Sandra; Bühler, Carl; Jung, Alexandra; Hänisch, Jens; Holzapfel, Bernhard

    2017-09-01

    GdBa2Cu3O7-x -BaHfO3 (GdBCO-BHO) nanocomposite (NC) films containing 12 mol% BHO nanoparticles were prepared by chemical solution deposition (CSD) following the TFA route on SrTiO3 (STO) single crystals and buffered metallic tapes supplied by two different companies: Deutsche Nanoschicht GmbH and SuperOx. We optimized the preparation of our GdBCO-BHO solutions with acetylacetone making the film synthesis very robust and reproducible, and obtained 220 nm films with excellent superconducting properties. We show the structural, morphological and superconducting properties of the films after a careful optimization of the processing parameters (growth temperature, oxygen partial pressure and heating ramp). The films reach critical temperatures (T c) of ˜94 K, self-field critical current densities (J c) of >7 MA cm- 2 and maximum pinning force densities (F p) of ˜16 GN m- 3 at 77 K on STO and T c of ˜94.5 K and J c > 1.5 MA cm- 2 on buffered metallic tapes. The transport properties under applied magnetic fields are significantly improved with respect to the pristine GdBCO films. The GdBCO-BHO NC films on STO present epitaxial c-axis orientation with excellent out-of-plane and in-plane texture. The films are, in general, very dense with a low amount of pores and only superficial indentations. On the other hand, we present, for the first time, a systematic study of CSD-grown GdBCO-BHO NC films on buffered metallic tapes. We have used the optimized growth conditions for STO as a reference and identified some limitations on the film synthesis that should be overcome for further improvement of the films’ superconducting properties.

  8. Synthesis and characterization of YBa2Cu3O7(Y123) via sol-gel method for development of superconducting quantum interference device magnetometer.

    Science.gov (United States)

    Yahya, Noorhana; Zakariah, Muhammad Hanis

    2012-10-01

    Electromagnetic (EM) waves transmitted by Horizontal Electric Dipole (HED) source to detect contrasts in subsurface resistivity termed Seabed Logging (SBL) is now an established method for hydrocarbon exploration. However, currently used EM wave detectors for SBL have several challenges including the sensitivity and its bulk size. This work exploits the benefit of superconductor technology in developing a magnetometer termed Superconducting Quantum Interference Device (SQUID) which can potentially be used for SBL. A SQUID magnetometer was fabricated using hexagon shape-niobium wire with YBa2Cu37O, (YBCO) as a barrier. The YBa2Cu37O, samples were synthesized by sol-gel method and were sintered using a furnace and conventional microwave oven. The YBCO gel was dried at 120 degrees C in air for 72 hours. It was then ground and divided into 12 parts. Four samples were sintered at 750 degrees C, 850 degrees C, 900 degrees C, and 950 degrees C for 12 hours in a furnace to find the optimum temperature. The other eight samples were sintered in a microwave with 1100 Watt (W) with a different sintering time, 5, 15, 45 minutes, 1 hour, 1 hour 15 minutes, 1 hour 30 minutes, 1 hour 45 minutes and 2 hours. A DEWAR container was designed and fabricated using fiberglass material. It was filled with liquid nitrogen (LN2) to ensure the superconducting state of the magnetometer. XRD results showed that the optimum sintering temperature for the formation of orthorhombic Y-123 phase was at 950 degrees C with the crystallite size of 67 nm. The morphology results from Field Emission Scanning Electron Microscopy (FESEM) showed that the grains had formed a rod shape with an average diameter of 60 nm. The fabricated SQUID magnetometer was able to show an increment of approximately 249% in the intensity of the EM waves when the source receiver offset was one meter apart.

  9. Interdiffusion studies on high-Tc superconducting YBa2Cu3O7-δ thin films on Si(111) with a NiSi2/ZrO2 buffer layer

    DEFF Research Database (Denmark)

    Aarnink, W.A.M.; Blank, D.H.A.; Adelerhof, D.J.

    1991-01-01

    Interdiffusion studies on high-T(c) superconducting YBa2Cu3O7-delta thin films with thickness in the range of 2000-3000 angstrom, on a Si(111) substrate with a buffer layer have been performed. The buffer layer consists of a 400 angstrom thick epitaxial NiSi2 layer covered with 1200 angstrom...... x 10(4) A/cm2. With X-ray analysis (XRD), only c-axis orientation has been observed. The interdiffusion studies, using Rutherford backscattering spectrometry (RBS) and scanning Auger microscopy (SAM) show that the ZrO2 buffer layer prevents severe Si diffusion to the YBa2Cu3O7-delta layer, the Si...... substrate and Ni segregation to the surface of the ZrO2 layer may be expected. From the results we may conclude that, when using laser ablation, it is well possible to grow polycrystalline, c-axis-oriented high-T(c) superconducting YBa2Cu3O7-delta thin films on a Si(111) substrate with a NiSi2/ZrO2 buffer...

  10. Charge Aspects of Composite Pair Superconductivity

    Science.gov (United States)

    Flint, Rebecca

    2014-03-01

    Conventional Cooper pairs form from well-defined electronic quasiparticles, making the internal structure of the pair irrelevant. However, in the 115 family of superconductors, the heavy electrons are forming as they pair and the internal pair structure becomes as important as the pairing mechanism. Conventional spin fluctuation mediated pairing cannot capture the direct transition from incoherent local moments to heavy fermion superconductivity, but the formation of composite pairs favored by the two channel Kondo effect can. These composite pairs are local d-wave pairs formed by two conduction electrons in orthogonal Kondo channels screening the same local moment. Composite pairing shares the same symmetries as magnetically mediated pairing, however, only composite pairing necessarily involves a redistribution of charge within the unit cell originating from the internal pair structure, both as a monopole (valence change) and a quadrupole effect. This redistribution will onset sharply at the superconducting transition temperature. A smoking gun test for composite pairing is therefore a sharp signature at Tc - for example, a cusp in the Mossbauer isomer shift in NpPd5Al2 or in the NQR shift in (Ce,Pu)CoIn5.

  11. Ti3SiC2-Cu composites by mechanical milling and spark plasma sintering: Possible microstructure formation scenarios

    Science.gov (United States)

    Dudina, Dina V.; Mali, Vyacheslav I.; Anisimov, Alexander G.; Bulina, Natalia V.; Korchagin, Michail A.; Lomovsky, Oleg I.; Bataev, Ivan A.; Bataev, Vladimir A.

    2013-11-01

    We present several possible microstructure development scenarios in Ti3SiC2-Cu composites during mechanical milling and Spark Plasma Sintering (SPS). We have studied the effect of in situ consolidation during milling of Ti3SiC2 and Cu powders and melting of the Cu matrix during the SPS on the hardness and electrical conductivity of the sintered materials. Under low-energy milling, (3-5) vol.%Ti3SiC2-Cu composite particles of platelet morphology formed, which could be easily SPS-ed to 92-95% relative density. Under high-energy milling, millimeter-scale (3-5) vol.%Ti3SiC2-Cu granules formed as a result of in situ consolidation and presented a challenge to be sintered into a bulk fully dense sample; the corresponding SPS-ed compacts demonstrated a finer-grained Cu matrix and more significant levels of hardening compared to composites of the same composition processed by low-energy milling. The 3 vol.% Ti3SiC2-Cu in situ consolidated and Spark Plasma Sintered granules showed an extremely high hardness of 227 HV. High electrical conductivity of the Ti3SiC2-Cu composites sintered from the granules was an indication of efficient sintering of the granules to each other. Partial melting of the Cu matrix, if induced during the SPS, compromised the phase stability and uniformity of the microstructure of the Ti3SiC2-Cu composites and thus it is not to be suggested as a pathway to enhanced densification in this system.

  12. Spin dynamics in the metallic state of the high T{sub c} superconducting system YBa{sub 2}Cu{sub 3}O{sub 6+x}

    Energy Technology Data Exchange (ETDEWEB)

    Bourges, P.; Sidis, Y. [Laboratoire Leon Brillouin (LLB) - Centre d`Etudes de Saclay, 91 - Gif-sur-Yvette (France); Regnault, L.P.; Henry, J.Y.; Burlet, P. [CEA Centre d`Etudes de Grenoble, 38 (France). Dept. de Recherche Fondamentale sur la Matiere Condensee; Vettier, C. [European Synchrotron Research Facility, 38 -Grenoble (France)

    1994-12-31

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

  13. 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.

  14. Investigation of response of high-temperature superconducting Bi sub 2 Sr sub 2 CaCu sub 2 O sub y bolometer at hard substrate on infrared laser pulses of permanent power and variable relative pulse duration

    CERN Document Server

    Antonenko, S V; Korotkov, D P; Maltsev, S N

    2001-01-01

    A method for studying bolometric response of superconducting films to effect of a sequence of IR pulses of identical power and variable relative pulse duration using an optical rod was developed. A semiconductor laser was used as radiation source. Using the method suggested experiments on studying characteristics of a superconducting bolometer on the basis of Bi sub 2 Sr sub 2 CaCu sub 2 O sub y film on a MgO substrate were conducted. It was found that increase in pulse repetition frequency of IR laser in the range of 1-7 kHz brought about a decrease (by a factor of 2.5) of variable component of the bolometer response amplitude

  15. 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.

  16. Strength and thermal stability of Cu-Al2O3 composite obtained by internal oxidation

    Directory of Open Access Journals (Sweden)

    Jovanovic, M. T.

    2010-12-01

    Full Text Available The objective of the work is to study the effects of the high-energy milling on strengthening, thermal stability and electrical conductivity of Cu-Al2O3 composite. The prealloyed copper powders, atomized in inert gas and containing 3 wt. % Al, were milled up to 20 h in the planetary ball mill to oxidize in situ aluminium with oxygen from the air. Composite compacts were obtained by hot-pressing in an argon atmosphere at 800 °C for 3 h under the pressure of 35MPa. The microstructural characterization was performed by the optical microscope, scanning electron microscope (SEM, transmission electron microscope (TEM and X-ray diffraction analysis (XRD. The microhardness, electrical conductivity and density measurements were also carried out. The effect of internal oxidation and high-energy milling on strengthening of Cu-Al2O3 composite was significant, The increase of the microhardness of composite compacts (292 HV is almost threefold comparing to compacts processed from the as-received Cu-3 wt. % Al powder (102 HV. The grain size of Cu-Al2O3 compacts processed from 5 and 20 h-milled powders was 75 and 45 nm, respectively. The small increase in the grain size and the small microhardness drop indicate the high thermal stability of Cu-Al2O3 composite during high-temperature exposure at 800 °C.El objetivo del trabajo es el estudio de los efectos de la pulverización con altas energías sobre la resistencia, estabilidad térmica y conductividad eléctrica del compuesto Cu-Al2O3. El polvo pre-aleado de cobre, obtenido a través de la atomización con gas inerte y con un contenido de 3wt. % Al, se molió durante 20 h en el molino planetario de bolas dando lugar a la oxidación in situ del aluminio con el oxígeno del aire. El compuesto compactado se ha obtenido mediante prensado en caliente en atmósfera de argón a 800 °C durante 3 h y a una presión de 35MPa. La caracterización microestructural se hizo a través de microscopia óptica, microscopia

  17. Double junction photoelectrochemical solar cells based on Cu2ZnSnS4/Cu2ZnSnSe4 thin film as composite photocathode

    Science.gov (United States)

    Zhu, L.; Qiang, Y. H.; Zhao, Y. L.; Gu, X. Q.

    2014-02-01

    A solvothermal method was used to synthesize Cu2ZnSnS4 (CZTS) and Cu2ZnSnSe4 (CZTSe) nanoparticles. CZTS/CZTSe bilayer films have been fabricated via a layer-by-layer blade coating process on the fluorine dope tin oxide (FTO) substrates. We converted conventional dye-sensitized solar cells (DSSCs) into double junction photoelectrochemical solar cells with the replacement of the Pt-coated counter electrode with the as-prepared films as composite photocathodes. Compared with conventional DSSCs, the cells show an increased short circuit current and power conversion efficiency.

  18. Characterization of the current-induced resistive spots in superconducting YBa{sub 2}Cu{sub 3}O{sub 7} strips

    Energy Technology Data Exchange (ETDEWEB)

    Harrabi, K.; Salem, A.F.; Ziq, K.; Mansour, A.I.; Kunwar, S.; Berdiyorov, G. [King Fahd University of Petroleum and Minerals, Physics Department, Dhahran (Saudi Arabia); Maneval, J.P. [Laboratoire Pierre Aigrain, Paris (France)

    2014-12-15

    For over a decade, ultrathin superconducting films have been developed for the detection of single photons at optical or near infrared frequencies, with competitive performances in terms of quantum efficiency, speed, and low dark count rate. In order to avoid the requirement of helium refrigeration, we consider here the use of high temperature materials, known to achieve very fast responsiveness to laser irradiation. We excite thin filaments of the cuprate YBa{sub 2}Cu{sub 3}O{sub 7} by rectangular pulses of supercritical current so as to produce either a phase-slip centre (PSC) or a normal hot spot (HS), according to the temperature and the current amplitude selected. That procedure provides information about the maximum bias current to be used in a particle detector, about the return current back to the quiescent state after excitation, and about the rate of growth and decay of a HS. We also measure the time of PSC nucleation. A unique feature of that approach is to provide the rate of heat transfer between the film and its substrate at whatever temperature, in the superconducting state, in the practical conditions of operation. (orig.)

  19. Effect of microwave-enhanced superconductivity in YBa{sub 2}Cu{sub 3}O{sub 7} bi-crystalline grain boundary weak-links

    Energy Technology Data Exchange (ETDEWEB)

    Fu, C.M.; Chen, C.M.; Lin, H.C. [National Chiao-Tung Univ., Taiwan (China)] [and others

    1994-12-31

    We have studied systematically the effect of microwave irradiation on the temperature dependent resistivity R(T) and the current-voltage (I-V) characteristics of YBa{sub 2}Cu{sub 3}O{sub 7-x} (YBCO) bicrystalline grain boundary weak-links (GBWLs), with grain boundary of three different tilt angles. The superconducting transition temperature, T{sub c}, has significant enhancement upon microwave irradiation. The microwave enhanced T{sub c} is increased as a function of incidence microwave power, but limited to an optimum power level. The GBWLs of 45{degrees} tilt boundary has shown to be most sensitive to the microwave irradiation power, and the GBWLs of 36.8{degrees} tilt boundary has displayed a moderate response. In contrast, no enhancement of T{sub c} was observed in the GBWLs of 24{degrees} tilt boundary, as well as in the uniform films. Under the microwave irradiation, the R(T) dependence is hysteretic as the transition taken from superconducting state to normal state and vice versa. Mechanisms associated with the redistribution of nonequilibrium quasiparticles under microwave irradiation are discussed.

  20. Gap distributions and spatial variation of electronic states in superconducting and pseudogap states of Bi{sub 2}Sr{sub 2}Ca{sub 2}CuO{sub 8+{delta}}

    Energy Technology Data Exchange (ETDEWEB)

    Gomes, K.K.; Pasupathy, A.; Pushp, A. [Department of Physics, Joseph Henry Laboratories, Princeton University, Princeton, NJ 08544 (United States); Ono, S.; Ando, Y. [Central Research Institute of Electric Power Industry, Komae, Tokyo 201-8511 (Japan); Yazdani, A. [Department of Physics, Joseph Henry Laboratories, Princeton University, Princeton, NJ 08544 (United States)], E-mail: yazdani@princeton.edu

    2007-09-01

    High-resolution scanning tunneling microscopy has been used to study the tunneling density of states in lightly underdoped samples of the high-T{sub c} superconductor Bi{sub 2}Sr{sub 2}Ca{sub 2}CuO{sub 8+{delta}} in both the superconducting and pseudogap states. We demonstrate that the tunneling gaps observed in these two states have identical spatial distributions and correlation lengths. This observation suggests that the two gaps, and hence the two phenomena, cannot have a competing origin. In addition, we present measurements that show that in contrast to the superconducting state, in which low energy quasi-particles are homogenous in real space, the states near the Fermi level are spatially inhomogeneous in the pseudogap state. The variation of the low-energy electronic states is spatially correlated with local changes in the pseudogap.

  1. Structural characteristics of the new high-T/sub c/ superconducting phase Bi/sub 2/ Sr/sub 2/ Ca Cu/sub 2/ O/sub 8+x/

    Energy Technology Data Exchange (ETDEWEB)

    Carrillo, E.; Orozco, E.; Fuentes-Maya, J.; Mendoza, A.; Gasga, J.R.; Martinez, L.; Perez, R.; Garcia, A.; Schabes, P.S.; Acosta, D.

    1988-01-01

    A structural characterization of the superconducting phases in Bi/sub 2/ Sr/sub 2/ Ca Cu/sub 2/ O/sub 8+x/ is carried out. X-ray measurements are in agreement with recently reported diffraction patterns indicating an orthorhombic structure with large c-axis parameter (/approx/ 30A). Twin boundaries which are commonly found in high-T/sub c/ superconducting compounds based on Y or rare earths are however not frequent in these new type of superconductors. Transmission Electron Microscope images show a layered type of structure and electron diffraction patterns which confirm the orthorhombic structure. The resistivity measurements show a large drop at 100/sup 0/K with a T/sub c/ of the order of 76/sup 0/K.

  2. Raman studies in off-stoichiometric superconducting compounds of the Type Bi{sub 2-x}Pb{sub y}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub {delta}}

    Energy Technology Data Exchange (ETDEWEB)

    Garcia, C.M.; Valdes, E.D.; Malagon, G.P.; Puente, G.C.; Lopez, J.O. [Instituto Politecnico Nacional (Mexico); Falcony, C.; Gallardo, A.C. [Centro de Investigacion y Estudios Avanzados (Mexico)

    1995-02-01

    Raman measurements performed on superconducting ceramic samples of the type Bi{sub 2-x}Pb{sub y}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub {delta}}, with y = 0.3, 0.6, 0.9 and x = 0.1, 0.2, are reported. All Raman phonons with symmetry A{sub 1g} have been observed. Phonon identification has been carried out using previous reported studies of the Bi{sub 2}Sr{sub 2}Ca{sub n-1}Cu{sub n}O{sub 2n+y} system, for n = 1, 2, 3. A description of the detected Raman active modes in all samples is given, and the study of these modes in terms of the relative amount of lead-to-bismuth content and thermal treatment is also presented.

  3. TEM characterization of Al-C-Cu-Al{sub 2}O{sub 3} composites produced by mechanical milling

    Energy Technology Data Exchange (ETDEWEB)

    Santos-Beltran, A. [Centro de Investigacion en Materiales Avanzados (CIMAV), Miguel de Cervantes No. 120, C.P. 31109, Chihuahua, Chih. (Mexico); Gallegos-Orozco, V. [Centro de Investigacion en Materiales Avanzados (CIMAV), Miguel de Cervantes No. 120, C.P. 31109, Chihuahua, Chih. (Mexico); Estrada-Guel, I. [Centro de Investigacion en Materiales Avanzados (CIMAV), Miguel de Cervantes No. 120, C.P. 31109, Chihuahua, Chih. (Mexico); Bejar-Gomez, L. [Universidad Mich. de San Nicolas de Hidalgo, Edif. ' W' , C.U., C.P. 58000, Morelia, Mich. (Mexico); Espinosa-Magana, F. [Centro de Investigacion en Materiales Avanzados (CIMAV), Miguel de Cervantes No. 120, C.P. 31109, Chihuahua, Chih. (Mexico); Miki-Yoshida, M. [Centro de Investigacion en Materiales Avanzados (CIMAV), Miguel de Cervantes No. 120, C.P. 31109, Chihuahua, Chih. (Mexico); Martinez-Sanchez, R. [Centro de Investigacion en Materiales Avanzados (CIMAV), Miguel de Cervantes No. 120, C.P. 31109, Chihuahua, Chih. (Mexico)]. E-mail: roberto.martinez@cimav.edu.mx

    2007-05-31

    Novel Al-based composites (Al-C-Cu-Al{sub 2}O{sub 3}) obtained by mechanical milling (MM), were characterized by transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS). Analyses of composites were carried out in both, the as-milled and the as-sintered conditions. C nanoparticles were found in the as-milled condition and Al{sub 2}O{sub 3} nanofibers were found in as-sintered products, as determined by EELS. C and Cu react with Al to crystallize in Al{sub 3}C{sub 4} and Al{sub 2}Cu structures, respectively.

  4. Fully Printed Memristors from Cu-SiO2 Core-Shell Nanowire Composites

    Science.gov (United States)

    Catenacci, Matthew J.; Flowers, Patrick F.; Cao, Changyong; Andrews, Joseph B.; Franklin, Aaron D.; Wiley, Benjamin J.

    2017-07-01

    This article describes a fully printed memory in which a composite of Cu-SiO2 nanowires dispersed in ethylcellulose acts as a resistive switch between printed Cu and Au electrodes. A 16-cell crossbar array of these memristors was printed with an aerosol jet. The memristors exhibited moderate operating voltages (˜3 V), no degradation over 104 switching cycles, write speeds of 3 μs, and extrapolated retention times of 10 years. The low operating voltage enabled the programming of a fully printed 4-bit memristor array with an Arduino. The excellent performance of these fully printed memristors could help enable the creation of fully printed RFID tags and sensors with integrated data storage.

  5. Local chemical composition of HgBaCaCuO high-temperature superconductors

    Science.gov (United States)

    Alméras, P.; Dell'Orto, T.; Coluzza, C.; Almeida, J.; Margaritondo, G.; Xue, Y. Y.; Meng, R. L.; Chu, C. W.

    1994-07-01

    The microchemical composition and the electronic structure of the two superconductors HgBa2Ca2Cu3O8+δ (Hg-1223) and HgBa2Ca1Cu2O6+δ (Hg-1212) were analyzed with the technique of photoemission with high spatial resolution. This enabled primary spectral peaks to be separated from their satellites due to local charging induced by the primary photon beam. Each sample contains superconducting and impurity phases with inhomogeneous spatial distributions. The oxygenation-induced increase in the critical temperature is related to a increase in the Cu-O plane carrier concentration.

  6. Non-destructive magneto-strain analysis of YB2Cu3Oy superconducting magnets using neutron diffraction in the time-of-flight mode

    Science.gov (United States)

    Tomita, M.; Muralidhar, M.; Suzuki, K.; Ishihara, A.; Fukumoto, Y.; Osamura, K.; Machiya, S.; Harjo, S.

    2012-09-01

    In general, neutron diffraction allows a non-destructive investigation of bulk samples. In this study, a magneto-strain analysis of the trapped field in YB2Cu3Oy "YBCO" superconducting bulks was carried out at 45 K using neutron diffraction time-of-flight (TOF) method. The TAKUMI TOF neutron diffractometer offers unique advantages, including accommodation of large objectives, control of the experimental set-up using a 4-axial goniometer (XYZθ), and a positional resolution of 0.01 mm allowing an accurate sample positioning. As a result, the lattice strain in the YB2Cu3Oy material could be estimated in both radial and hoop directions by estimating the difference of plane spacing with/without the trapped magnetic field. The results indicate that the samples with a low trapped field values have smaller magnetic strain than those with a high trapped field. Further, the strain in the hoop direction is higher than that in the radial direction. The present results indicate that neutron diffraction measurements are an effective method for evaluating the bulk residual strains in a non-destructive manner.

  7. Manufacturing of superconductive silver/ceramic composites

    DEFF Research Database (Denmark)

    Seifi, Behrouz; Bech, Jakob Ilsted; Eriksen, Morten

    2000-01-01

    Manufacturing of superconducting metal/ceramic composites is a rather new discipline within materials forming processes. High Temperature SuperConductors, HTSC, are manufactured applying the Oxide-Powder-In-Tube process, OPIT. A ceramic powder containing lead, calcium, bismuth, strontium......, and copper oxides is inserted into a silver tube and reduced by multi-step drawing. These single-filaments are packed in a new silver tube thus forming a multi-filament containing e.g. 37 single-filaments, which is subsequently reduced by drawing and rolling to tapes approximately 0.2 mm thick by 3 mm wide...

  8. Magnetic and transport properties of superconducting (YBa sub 2 Cu sub 3 O sub 7-. delta. ) sub 1-x Ag sub x ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Laborde, O.; Guillot, M. (SNCI, CRTBT, Lab. de Crstallographie, C.N.R.S., 38 - Grenoble (France)); Souletie, B.; Lejay, P.; Tholence, J.L. (CRTBT, C.N.R.S., 38 - Grenoble (France)); Capponi, J.J. (Lab. de Cristallographie, C.N.R.S., 38 - Grenoble (France)); Ermolieff, A.; Marthon, S. (LETI, CENG, 38 - Grenoble (France)); Dwir, B.; Pavuna, D. (Swiss Federal Inst. of Tech., Lausanne (Switzerland))

    1989-12-01

    The introduction of silver in the intergranular space of YBa{sub 2}Cu{sub 3}O{sub 7} ceramics improves their normal state electrical and mechanical properties. We report here a study of such composites of which the grain size was found to increase with the annealing temperature, and goes through a maximum around 20% wt.silver for a constant annealing temperature (1000degC). Moreover, a maximum in the filling factor of YBa{sub 2}Cu{sub 3}O{sub 7} is found from a.c. susceptibility measurements for x {approx equal} 15% wt. of silver, which also corresponds to the maximum of the current density. The intergranular silver is found to improve the diamagnetic shielding in very low field. The irreversible fields, H{sub cs}, as determined by magnetoresistance are only decreased by {proportional to}10% for a composite containing {proportional to}15% weight of silver. (orig.).

  9. The electrical and magnetic properties of ferromagnetic-superconducting compound Ru(Gd1.5-xPrxCe0.5Sr2Cu2O10-δ

    Directory of Open Access Journals (Sweden)

    A Khajehnezhad

    2009-08-01

    Full Text Available   Coexistence of superconductivity and magnetic ordering or their mutually exclusive existence in solids is one of the fundamental problems of solid state physics. To determine the effect of Pr substitution for Gd on electrical and magnetic properties of RuGd1.5Ce0.5Sr2Cu2O10-δ (Ru-1222, Ru(Gd1.5-xPrxCe0.5Sr2Cu2O10-δ with x=0.0, 0.01, 0.03, 0.03 3 , 0.04, 0.05, 0.06, 0.1 have been prepared by the standard solid-state reaction technique. The XRD patterns for various x have been obtained to show their phase purity. The resistivity and magnetoresistivity of samples have been measured at various temperatures and different magnetic fields up to 1.5T . Superconductivity and magnetic parameters such as superconducting transition temperature Tc and magnetic transition Tirr, have been obtained through resistivity curves. The sharp decrease in Tc with x in Ru(Gd1.5-xPrxCe0.5Sr2Cu2O10-δ shows competition between pair breaking by magnetic impurity, hole doping because of different valance of ions, difference in ionic radii and oxygen stoichiometry, which affect on superconducting transition. In Pr substitution for Gd, the small difference between Gd3+ and Pr3+,4+ ionic radii decreases the mean Ru-Ru distance, and as a result, the magnetic exchange interaction can become stronger with increasing x. Both Tc and Tirr decrease with external magnetic field .

  10. Surface composition deviation of Cu{sub 2}ZnSnS{sub 4} derivative powdered samples

    Energy Technology Data Exchange (ETDEWEB)

    Harel, S., E-mail: sylvie.harel@cnrs-imn.fr; Guillot-Deudon, C.; Choubrac, L.; Hamon, J.; Lafond, A.

    2014-06-01

    Powdered samples of Cu{sub 2}ZnSnS{sub 4} derivatives prepared through a solid-state route were investigated by both bulk (electron dispersive X-ray spectroscopy) and surface-sensitive (X-ray photoelectron spectroscopy) methods. We observe a deviation in composition between the surface and the bulk for all non-stoichiometric samples (both Cu-poor and Cu-rich). This behavior has already been observed for slightly Cu-poor CZTS thin films and is reminiscent of that of CIGSe compounds.

  11. Tl 2Ba 2- xSr xCuO 6: A system exhibiting a compositionally controlled superconductor-metal transition

    Science.gov (United States)

    Ganguli, A. K.; Subramanian, M. A.

    1991-02-01

    Strontium-substituted thallium cuprates of the type Tl 2Ba 2- xSr xCuO 6 have been synthesized for various values of x. Single phases were obtained for x ≤ 1.2. The compounds crystallize in the tetragonal structure with space group {I4}/{mmm} as the parent Tl 2Ba 2CuO 6 oxide. Both a and c lattice parameter decrease with increase in x. Tc decreases gradually from 92 to 77 K ( x = 0.8). Beyond x = 1.0 superconductivity is lost. The x = 1.2 comparison is metallic down to 4.2 K.

  12. Detailed magnetization study of superconducting properties of YBa{sub 2}Cu{sub 3}O{sub 7-x} ceramic spheres

    Energy Technology Data Exchange (ETDEWEB)

    Landau, I L; Willems, J B; Hulliger, J [Department of Chemistry and Biochemistry, University of Berne, Freiestrasse 3, CH-3012 Berne (Switzerland)], E-mail: landau@iac.unibe.ch

    2008-03-05

    We present a magnetization study of low density YBa{sub 2}Cu{sub 3}O{sub 7-x} ceramics carried out in magnetic fields H such that 0.5 Oesuperconducting links between grains may be completely suppressed either by a magnetic field H{approx}100 Oe (at low temperatures) or by an increase of temperature to above 70 K. This property of the present samples allowed us to evaluate the ratio between the average grain size and the magnetic field penetration depth {lambda}. Furthermore, at temperatures T>85 K, using low field magnetization measurements, we were able to evaluate the temperature dependence of {lambda}, 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 {lambda}{sub ab}(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 H{sub c2}(T). At temperatures close to T{sub c}, the H{sub c2}(T) dependence turned out to be linear, in agreement with Ginzburg-Landau theory. The value of the temperature at which H{sub c2} 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.

  13. Al-Si/Al2O3 in situ composite prepared by displacement reaction of CuO/Al system

    Directory of Open Access Journals (Sweden)

    Zhang Jing

    2010-02-01

    Full Text Available Al2O3 particle-reinforced ZL109 composite was prepared by in situ reaction between CuO and Al. The microstructure was observed by means of OM, SEM and TEM. The Al2O3 particles in sub-micron sizes distribute uniformly in the matrix, and the Cu displaced from the in situ reaction forms net-like alloy phases with other alloy elements. The hardness and the tensile strength of the composites at room temperature have a slight increase as compared to that of the matrix. However, the tensile strength at 350 ℃ has reached 90.23 MPa, or 16.92 MPa higher than that of the matrix. The mechanism of the reaction in the CuO/Al system was studied by using of differential scanning calorimetry(DSC and thermodynamic calculation. The reaction between CuO and Al involves two steps. First, CuO reacts with Al to form Cu2O and Al2O3 at the melting temperature of the matrix alloy, and second, Cu2O reacts with Al to form Cu and Al2O3 at a higher temperature. At ZL109 casting temperature of 750–780 ℃, the second step can also take place because of the effect of exothermic reaction of the first step.

  14. Superconducting properties of (Tl1-xPbx)Sr2CaCu2O7-δ (x = 0.1 - 0.7) prepared using nano-sized PbO

    Science.gov (United States)

    Elmasroub, Hanan Saleh; Abd-Shukor, R.

    2017-05-01

    The effect of Pb substitution on Tl-1212 high Tc superconductor with nominal starting composition (Tl1-xPbx)Sr2CaCu2O7-δ (x = 0.1 - 0.7) has been investigated. Nano-sized PbO (10-30 nm) was used as a starting component. The samples were synthesized using the solid-state reaction technique and studied by powder X-ray diffraction method, electrical resistance measurements and scanning electron microscopy. The resistance-temperature curves showed metallic behavior for all samples. Samples with x = 0.6 showed the highest Tc onset (89 K) and Tc zero (78 K). This sample also showed the highest peak temperature for the derivative of the resistivity (ρ) versus temperature (T) curve, dρ/dT = 85 K. The X-ray diffraction patterns showed a major Tl-1212 phase with few weak diffraction lines of the Tl-1201. The deviation of electrical resistivity from linear behavior near the transition temperature was explained in terms of excess conductivity associated with Cooper pair formation. This work showed that nano-sized PbO could be used to enhance the formation of the superconducting Tl-1212 phase.

  15. Composite conductor containing superconductive wires

    Energy Technology Data Exchange (ETDEWEB)

    Larson, W.L.; Wong, J.

    1974-03-26

    A superconductor cable substitute made by coworking multiple rods of superconductive niobium--titanium or niobium--zirconium alloy with a common copper matrix to extend the copper and rods to form a final elongated product which has superconductive wires distributed in a reduced cross-section copper conductor with a complete metallurgical bond between the normal-conductive copper and the superconductor wires contained therein is described. The superconductor cable can be in the form of a tube.

  16. Composition and growth procedure-dependent properties of electrodeposited CuInSe 2 thin films

    Science.gov (United States)

    Babu, S. Moorthy; Ennaoui, A.; Lux-Steiner, M. Ch.

    2005-02-01

    CuInSe 2 thin films were deposited on molybdenum-coated glass substrates by electrodeposition. Deposition was carried out with a variety of electrochemical bath compositions. The quality of the deposits depends very much on the source materials as well as the concentration of the same in the electrolyte. The deposition potential was varied from -0.4 to -0.75 V vs. SCE. The pH of the solution was adjusted to 1.5-2 using diluted sulphuric acid. Chloride salts containing bath yield good surface morphology, but there is always excess of the metallic content in the deposited films. Different growth procedures, like initial metallic layers of copper or indium, layers of copper selenide or indium selenide before the actual deposition of ternary chalcopyrite layers were attempted. Fabrication pathway, morphological and compositional changes due to the different precursor route has been analysed. The quality of the deposits prepared by one-step electrodeposition is better than the deposits with a two-stage process. The deposited films were characterized with XRD, SEM-EDAX, UV-visible spectroscopy and I- V characteristics. The deposited films were annealed in air as well as in nitrogen atmosphere. The influence of annealing temperature, environment and annealing time on the properties of the films are evaluated. Attempts were made to fabricate solar cell structure from the deposited absorber films. The structure of Mo/CuInSe 2/CdS/ZnO/Ni was characterized with surface, optical and electrical studies.

  17. Compositional and electrical analysis of the multilayers of a CdS/CuInSe/sub 2/ solar cell

    Energy Technology Data Exchange (ETDEWEB)

    Noufi, R.; Dick, J.

    1985-11-15

    The compositional profiles and the electrical properties of the bilayers of CdS and CuInSe/sub 2/ films in CdS/CuInSe/sub 2/ solar cells are presented and compared with those of the individual layers alone. The CuInSe/sub 2/ bilayer shows that the two individual layers have mixed, except for the last-to-deposit 0.2--0.4 ..mu..m, which is semi-insulating and copper poor. This bilayer remains p type and highly resistive during the cell processing steps. The CdS bilayer consists of an almost stoichiometric layer close to the junction and a top In-doped low-resistivity layer. The CdS/CuInSe/sub 2/ may possibly operate as a P-S-N device, where the S layer is defined largely by a semi-insulating CuInSe/sub 2/ layer.

  18. Superconducting YBa 2Cu 3O 7- δ thin film grown on metallic film evaporated on MgO

    Science.gov (United States)

    Verdyan, A.; Azoulay, J.; Lapsker, I.

    2001-03-01

    At present it is commonly accepted that thin film formation of YBa 2Cu 3O 7- δ (YBCO) on conducting substrate is one of the keys to further development of advanced devices in the microelectronic and other applications. We have grown YBCO thin films by resistive evaporation technique on MgO coated with metallic layers (Ni or Ag). A simple inexpensive vacuum system equipped with resistively heated boats for metal and precursor mixture of yttrium, copper and barium fluoride powders was used. X-ray diffraction (XRD) and scanning electron microscopy techniques were used for texture, morphology and surface analyses respectively. Electrical and magnetical properties were determined by a standard dc four-probe method. The way of heating process is shown to be critical parameter in the film quality. The physical and electrical properties of the YBCO films are discussed in light of the fact that XRD measurements done on the metallic buffer layers have revealed a multicrystalline structure.

  19. Growth and superconducting properties of Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} {sub +} {sub δ} thin films incorporated with iridate nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    De Vero, Jeffrey C.; Hwang, Inwoong; Shin, Hyeonseop; Song, Jong Hyun [Department of Physics, Chungnam National University, Daejeon, 305-764 (Korea, Republic of); Santiago, Alvin Carl; Sarmago, Roland V. [National Institute of Physics, University of the Philippines, Diliman, 1101 (Philippines); Lee, Doopyo [Department of Physics, Pohang University of Science and Technology, Pohang, 790-784 (Korea, Republic of); Chang, Jungwon [Department of Display and Semiconductor Physics, Korea University, Sejong Campus, Sejong, 339-700 (Korea, Republic of); Korea Research Institute of Science and Standards, Daejeon, 305-340 (Korea, Republic of); Kim, Jinhee [Korea Research Institute of Science and Standards, Daejeon, 305-340 (Korea, Republic of)

    2014-08-15

    Iridate nanoparticle AIrO{sub 3} (A = Sr, Ba) incorporated Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} {sub +} {sub δ} (Bi-2212) thin films were successfully grown using pulsed laser deposition with post-growth ex situ heat treatment. Nanosized particles of SrIrO{sub 3} (Sr-iridate) and BaIrO{sub 3} (Ba-iridate) were deposited on top of MgO (100) substrate, followed by Bi-2212 layers to investigate their effects on the physical and superconducting properties of Bi-2212 thin films. The number of laser pulses was changed from 450 to 1800 to control the density of iridates in the Bi-2212 matrix. The composite film is then partial-melted at 890 C for 15 min and annealed at 850 C for 5 h in ambient air. Scanning electron microscopy shows that the surfaces of thin films with iridates are more compact with minimal voids and porosity than those of pure Bi-2212 thin films. Both types of iridate incorporation suppress T{sub c-zero} of Bi-2212 thin films. Incorporating Sr-iridate in the Bi-2212 strongly affects T{sub c-zero} than those with Ba-iridate at low density. However, both iridate incorporations result in the expansion of the c-axis lattice constant and variation of Bi/Sr ratio of Bi-2212 films. On the other hand, we observed improvement of the activation energy, U{sub 0}, as well as the self-field critical current density, J{sub c}(0), of Bi-2212 films with incorporated iridates even with suppressed T{sub c-zero}. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  20. Time-resolved X-ray diffraction study on superconducting YBa{sub 2}Cu{sub 3}O{sub 7} epitaxially grown on SrTiO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Luebcke, A.

    2007-07-01

    In this PhD thesis time-resolved X-ray diffraction in optical pump - X-ray probe scheme was applied for the first time to a High-Temperature Superconductor in the superconducting state. The aim was to study the possible lattice response to optical Cooper pair breaking. As sample a thin YBa{sub 2}Cu{sub 3}O{sub 7} film with a superconducting transition temperature of T{sub c}=90 K, epitaxially grown on a SrTiO{sub 3} single crystal was used. (orig.)

  1. Influence of calcium on transport properties, band spectrum and superconductivity of YBa2Cu3O(y) and YBa(1.5)La(0.5)Cu3O(y)

    Science.gov (United States)

    Gasumyants, V. E.; Vladimirskaya, E. V.; Patrina, I. B.

    1995-01-01

    The comparative investigation of transport phenomena in Y(1-x)Ca(x)Ba2Cu3O(y) (0 is less than x is less than 0.25; 6.96 is greater than y is greater than 6.87 and 6.73 is less than x is less than 6.53); Y(1-x)Ca(x)Ba(1.5)La(0.5)Cu3O(y) (0 is less than x is less than 0.5; 7.12 is greater than y is greater than 6.96) and YBa(2-x)La(x)Cu3O(y) (0 is less than x is less than 0.5; 6.95 is less than y is less than 7.21) systems have been carried out. The temperature dependencies of resistivity and thermopower have been measured. It was found that the S(T) dependencies take some additional features with Ca content increase. The results obtained have been analyzed on the basis of the phenomenological theory of electron transport in the case of the narrow conductive band. The main parameters of the band spectrum (the band filling with electrons degree and the total effective band width) have been determined. The dependencies of these from contents of substituting elements are discussed. Analyzing the results obtained simultaneously with the tendencies in oxygen content and critical temperature change we have confirmed the conclusion that the oxygen sublattice disordering has a determinant effect on band structure parameters and superconductive properties of YBa2Cu3O(y). The results obtained suggest that Ca gives rise to some peculiarities in band spectrum of this compound.

  2. Microstructure and Mechanical Performance of Cu-SnO2-rGO based Composites Prepared by Plasma Activated Sintering

    Institute of Scientific and Technical Information of China (English)

    LUO Guoqiang; HUANG Jing; JIN Zhipeng; LI Meijuan; JIANG Xiaojuan; SHEN Qiang; ZHANG Lianmeng

    2015-01-01

    A novel chemical technique combined with unique plasma activated sintering (PAS) was utilized to prepare consolidated copper matrix composites (CMCs) by adding Cu-SnO2-rGO layered micro powders as reinforced fillers into Cu matrix. The repeating Cu-SnO2-rGO structure was composed of inner dispersed reduced graphene oxide (rGO), SnO2 as intermedia and outer Cu coating. SnO2 was introduced to the surface of rGO sheets in order to prevent the graphene aggregation with SnO2 serving as spacer and to provide enough active sites for subsequent Cu deposition. This process can guarantee rGO sheets to sufifciently disperse and Cu nanoparticles to tightly and uniformly anchor on each layer of rGO by means of the SnO2 active sites as well as strictly control the reduction speed of Cu2+. The complete cover of Cu nanoparticles on rGO sheets thoroughly avoids direct contact among rGO layers. Hence, the repeating structure can simultaneously solve the wettability problem between rGO and Cu matrix as well as improve the bonding strength between rGO and Cu matrix at the well-bonded Cu-SnO2-rGO interface. The isolated rGO can effectively hinder the glide of dislocation at Cu-rGO interface and support the applied loads. Finally, the compressive strength of CMCs was enhanced when the strengthening efifciency reached up to 41.

  3. Crystal structure, superconductivity and magnetic properties of the superconducting ferromagnets Gd{sub 1.4-x}Dy{sub x}Ce{sub 0.6}Sr{sub 2}RuCu{sub 2}O{sub 10} (x=0-0.6)

    Energy Technology Data Exchange (ETDEWEB)

    Kalavathi, S.; Janaki, J.; Reddy, G.V.R.; Rao, G.V.N.; Sankara Sastry, V.; Hariharan, Y

    2003-07-15

    The structural, electrical and magnetic properties of the superconducting ferromagnets, Gd{sub 1.4-x}Dy{sub x}Ce{sub 0.6}Sr{sub 2}RuCu{sub 2}O{sub 10} (x=0-0.6) are systematically investigated as a function of Dy doping and temperature. These compounds are characterized by high temperature superconductivity (T{sub c} ranging from 20 to 40 K depending upon the Dy content) co-existing with weak ferromagnetism with two magnetic transitions (T{sub M2} ranging from 95 to 106 K and T{sub M1} around 120 K). Doping with Dy gives no significant structural changes except for a minor change in the c/a ratio. However the superconducting transition temperature is significantly suppressed and magnetic ordering temperature enhanced on Dy doping. These effects are described and discussed.

  4. Direct Spectroscopic Evidence for Phase Competition between the Pseudogap and Superconductivity in Bi2Sr2CaCu2O8+δ

    Energy Technology Data Exchange (ETDEWEB)

    Hashimoto, Makoto [SLAC National Accelerator Lab., Menlo Park, CA (United States); Nowadnick, Elizabeth A. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Stanford Univ., CA (United States); He, Rui-Hua [SLAC National Accelerator Lab., Menlo Park, CA (United States); Stanford Univ., CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Vishik, Inna M. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Stanford Univ., CA (United States); Moritz, Brian [SLAC National Accelerator Lab., Menlo Park, CA (United States); Univ. of North Dakota, Grand Forks, ND (United States); He, Yu [SLAC National Accelerator Lab., Menlo Park, CA (United States); Stanford Univ., CA (United States); Tanaka, Kiyohisa [SLAC National Accelerator Lab., Menlo Park, CA (United States); Stanford Univ., CA (United States); Osaka Univ. (Japan); Moore, Robert G. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Lu, Donghui [SLAC National Accelerator Lab., Menlo Park, CA (United States); Yoshida, Yoshiyuki [National Institute of Advanced Industrial Science and Technology, Tsukuba (Japan); Ishikado, Motoyuki [National Institute of Advanced Industrial Science and Technology, Tsukuba (Japan); Japan Atomic Energy Agency, Tokai (Japan); Sasagawa, Takao [Tokyo Inst. of Technology (Japan); Fujita, Kazuhiro [Univ. of Tokyo (Japan); Cornell Univ., Ithaca, NY (United States); Ishida, Shigeyuku [Univ. of Tokyo (Japan); Uchida, Shinichi [Univ. of Tokyo (Japan); Eisaki, Hiroshi [National Institute of Advanced Industrial Science and Technology, Tsukuba (Japan); Hussain, Zahid [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Devereaux, Thomas P. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Shen, Zhi-Xun [SLAC National Accelerator Lab., Menlo Park, CA (United States); Stanford Univ., CA (United States)

    2014-11-02

    In the high-temperature (Tc) cuprate superconductors, increasing evidence suggests that the pseudogap, existing below the pseudogap temperature T*, has a distinct broken electronic symmetry from that of superconductivity. Particularly, recent scattering experiments on the underdoped cuprates have suggested that a charge ordering competes with superconductivity. However, no direct link of this physics and the important low-energy excitations has been identified. We report an antagonistic singularity at Tc in the spectral weight of Bi2Sr2CaCu2O8+δ as a compelling evidence for phase competition, which persists up to a high hole concentration p ~ 0.22. Comparison with a theoretical calculation confirms that the singularity is a signature of competition between the order parameters for the pseudogap and superconductivity. Our observation of the spectroscopic singularity at finite temperatures over a wide doping range provides new insights into the nature of the competitive interplay between the two intertwined phases and the complex phase diagram near the pseudogap critical point.

  5. The effect of Al2O3 nanopowder addition on the phase formation and the superconducting properties of Bi1.6Pb0.4Sr1.9Ca2.1Cu3O10-y

    Directory of Open Access Journals (Sweden)

    A Aftabi

    2009-08-01

    Full Text Available   In this work Bi1.6Pb0.4Sr1.9Ca2.1Cu3O10-y superconducting system (Bi2223 has been prepared by solid state reaction and the effect of nanoalumina additive on the phase formation and supercoducting properties have been investigated. XRD investigations show that addition of 0.2 wt% of nanoalumina on the superconducting system improved Bi-2223 phase formation . The results show that Jc increases from 36 A/cm2 for the nanoalumina free sample to 107 A/cm2 for the sample with 0.5 wt% nanoalumina.On the other hand results show that the transition temperature (Tc of all samples is around 108 K and addition of nanoalumina has not affected Tc significantly .

  6. Al2O3/SUS304 Brazing via AgCuTi-W Composite as Active Filler

    Science.gov (United States)

    Su, Cherng-Yuh; Zhuang, Xie-Zongyang; Pan, Cheng-Tang

    2014-03-01

    Alumina ceramic (α-Al2O3) was brazed to stainless steel (SUS304) using an Ag-Cu-Ti + W composite filler and a traditional active brazing filler alloy (CuSil-ABA). Then, the effects of the presence of W particles and of the brazing parameters on the microstructures and mechanical properties of the brazed joints were investigated. The maximum tensile strength of the joints obtained using Ag-Cu-Ti + W composite filler was 13.2 MPa, which is similar to that obtained using CuSil-ABA filler (13.5 MPa). When the joint was brazed at 930 °C for 30 min, the tensile strengths decreased for both kinds of fillers, although the strength was slightly higher for the Ag-Cu-Ti + W composite filler than for the Ag-Cu-Ti filler. The interfacial microstructure results show that the Ti reacts with W to form a Ti-W-O compound in the brazing alloy. When there are more W particles in the brazing alloy, the thickness of the Ti X O Y reaction layer near the alumina ceramic decreases. Moreover, W particles added to the brazing alloy can reduce the coefficient of thermal expansion of the brazing alloy, which results in lower residual stress between the Al2O3 and SUS304 in the brazing joints and thus yields higher tensile strengths as compared to those obtained using the CuSil-ABA brazing alloy.

  7. An Investigation of TiO2 Addition on Microstructure Evolution of Sn-Cu-Ni Solder Paste Composite

    Directory of Open Access Journals (Sweden)

    Saud Norainiza

    2016-01-01

    Full Text Available In this research, varying fraction of titanium oxide (TiO2 reinforcement particles was successfully incorporated into Sn-Cu-Ni solder paste in an effort to study the influence of TiO2 addition on microstructure evolution of Sn-Cu-Ni solder paste composite. Sn-Cu-Ni solder paste composite was produced by mixing TiO2 particle with Sn-Cu-Ni solder paste. The microstructure analysis was carried out by Scanning Electron Microscopy-Energy dispersive X-ray (SEM-EDX. The addition TiO2 particle helps to refine the bulk solder microstructure and suppress the intermetallic compound (IMC formation at the interface as will be discussed further.

  8. Composite metallic sheathes: the key to low-cost, high strength (Bi,Pb)2Sr2Ca2Cu3O10-based tapes?

    DEFF Research Database (Denmark)

    Grivel, Jean-Claude

    2007-01-01

    (Bi, Pb)(2)Sr2Ca2Cu3O10-based superconducting tapes were prepared by the powder- in- tube process, using a bimetallic sheath consisting of Ag and Ni. Ag was in contact with the superconducting ceramic core and acted as a protective layer against reaction between the external Ni sheath and the core......(e) of about 11 000 A cm(-2), were achieved in a single heat-treatment. The efficient protection offered by the Ag layer against Ni diffusion into the ceramic core suggests that Ag layers as thin as 5 mu m may be applied, thus reducing the production costs. The superior stiffness of Ni provides a stronger...

  9. sup 119 Sn-Moessbauer study on the normal lattice vibration of superconducting Bi(Pb) sub 2 Sr sub 2 Ca sub 2 Cu sub 3 Sn sub 0. 015 O sub 10-y

    Energy Technology Data Exchange (ETDEWEB)

    Nishida, Tetsuaki; Takashima, Yoshimasa (Kyushu Univ., Fukuoka (Japan). Faculty of Science); Katada, Motomi; Miura, Norio; Deshimaru, Yuichi; Otani, Tetsuya; Yamazoe, Noboru; Matsumoto, Yasukuni

    1991-04-01

    The {sup 119}Sn-Moessbauer spectrum of superconducting Bi(Pb){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}Sn{sub 0.015}O{sub 10-y} ceramic, having the T{sub c} of 108 K, consists of an intense doublet peak with the {delta} of 0.18 mmcenter dots{sup -1} and the {Delta} of 1.01 mmcenter dot s{sup -1} at room temperature. The {delta} and {Delta} indicate that the Sn{sup 4+} is substituted for the copper ion in the triangular CuO{sub 3} site of the CuO{sub 4} layer. The {delta} and the absorption area increase gradually with decreasing temperature and become saturated at about 30 K, being consistent with the theoretical curves obtained from the 'combined Debye and Einstein model'. Only the normal vibration without the softening is observed in the CuO{sub 4} layer. (author).

  10. Influence of nano-Al2O3-reinforced oxide-dispersion-strengthened Cu on the mechanical and tribological properties of Cu-based composites

    Science.gov (United States)

    Zhao, Xiang; Guo, Lei-chen; Zhang, Long; Jia, Ting-ting; Chen, Cun-guang; Hao, Jun-jie; Shao, Hui-ping; Guo, Zhi-meng; Luo, Ji; Sun, Jun-bin

    2016-12-01

    The mechanical and tribological properties of Cu-based powder metallurgy (P/M) friction composites containing 10wt%-50wt% oxide-dispersion-strengthened (ODS) Cu reinforced with nano-Al2O3 were investigated. Additionally, the friction and wear behaviors as well as the wear mechanism of the Cu-based composites were characterized by scanning electron microscopy (SEM) in conjunction with energy-dispersive X-ray spectroscopy (EDS) elemental mapping. The results indicated that the Cu-based friction composite containing 30wt% ODS Cu exhibited the highest hardness and shear strength. The average and instantaneous friction coefficient curves of this sample, when operated in a high-speed train at a speed of 300 km/h, were similar to those of a commercial disc brake pad produced by Knorr-Bremse AG (Germany). Additionally, the lowest linear wear loss of the obtained samples was (0.008 ± 0.001) mm per time per face, which is much lower than that of the Knorr-Bremse pad ((0.01 ± 0.001) mm). The excellent performance of the developed pad is a consequence of the formation of a dense oxide composite layer and its close combination with the pad body.

  11. 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.

  12. Shape controlled synthesis and characterization of Cu{sub 2}O nanostructures assisted by composite surfactants system

    Energy Technology Data Exchange (ETDEWEB)

    Ahmed, Asar [Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208016, Uttar Pradesh (India); Gajbhiye, Namdeo S., E-mail: nsg@iitk.ac.in [Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208016, Uttar Pradesh (India); Joshi, Amish G. [Physics of Energy Harvesting Division, National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi 110012 (India)

    2011-10-03

    Highlights: {yields} Simple and inexpensive one pot synthesis of various Cu{sub 2}O nanostructures is demonstrated by manipulating the composite surfactant system. {yields} Surface properties are studied by the X-ray photoelectron spectroscopy. {yields} The prepared materials were also used for photocatalysis has in the degradation of organic dye Rhodamine B. - Abstract: A simple methodology has been demonstrated to synthesize various nanocrystalline Cu{sub 2}O materials assisted by composite surfactant system, SDS and Tween 80 using the polyol method. Glycolaldehyde prepared in situ by heating ethylene glycol solvent at 160 deg. C for 2 h, was utilized as the reducing agent. The relative ratio of the two surfactants was manipulated to achieve different Cu{sub 2}O morphologies, e.g. nanocrystalline Cu{sub 2}O flowers, hollow spheres consisting of holes and ring type structure. The FT-IR spectroscopy confirmed that the SDS and Tween 80 moieties were indeed present on the surface as capping agents in order to stabilize the surface nanocrystallites by the co-ordinative interactions between the oxygen atoms of Tween 80 and SDS and the Cu atoms at the surface of the synthesized Cu{sub 2}O particles. These oxygen atoms eventually encourage the oxidation of the surface Cu atoms to form a thin CuO layer, presence of which on the surface was corroborated by the XPS measurements. Sputtering of the samples was also carried out to remove the surface CuO thin layer and expose the inner Cu{sub 2}O. These nanomaterials were then investigated for their potential applications in photocatalytic degradation of Rhodamine B dye.

  13. Superconductivity in ZrCuxTe2

    Science.gov (United States)

    Baptista, Naiara; Grant, Ted; Renosto, Sergio; Fisck, Zack; Jefferson Machado, Antonio

    2012-02-01

    Layered transition metal dichalcogenides of the type MX2 (M is transition metal, X = S, Se, Te) have been studied for their electronic properties due to low dimensionality. In these materials each layer correspond to the hexagonal transition metal intercalated by two similar chalcogen sheets. In ZrTe2 the prototype structure is CdI2. The interaction of layers is weak as van der Walls bonding between chalcogen element (X). In general charge density wave and superconductivity coexist in these of materials. Indeed, various compounds of this material class exhibits this coexistence such as 2H-TaS2, 2H-NbS2 etc. Some results reported in literature about the electrical properties of ZrTe2 show that this material presents metallic behavior at a temperature interval from 4.0 K to 300 K. Thus, in this work we present results about intercalation of Cu in the ZrTe2 compound. The results suggest that the intercalation of Cu is able to induce superconductivity in this compound. The superconducting critical temperature close to 10.2 K is revealed through of magnetization and resistivity measurements. The x-ray result reveals a new compound, originating from Cu intercalation and crystallizes in the LiCrS2 prototype structure.

  14. A study of planar structures formed on the modified Al2O3 surfaces determining the topology of superconducting elements during YBa2Cu3O7- d deposition

    Science.gov (United States)

    Masterov, D. V.; Pavlov, S. A.; Parafin, A. E.; Yunin, P. A.

    2016-06-01

    We investigate the structural and electrical properties of planar superconducting structures based on the YBa2Cu3O7- d (YBCO) epitaxial films obtained by preliminary modification of the substrate surface. A special master mask was formed on the substrates, so that, at the standard YBCO film deposition onto such a substrate, an insulator layer grew in the modified areas and a superconducting film, in the unmodified ones. Thus, the planar superconducting structure of a desired topology was formed, and the YBCO deposition finished the process. Using this technique, YBCO bridges with widths of 4, 10, and 50 μm on films of different thicknesses and a planar inductive coil were formed. The superconducting transition temperature of the bridges was about 90 K, and the critical current density at a temperature of 77 K was up to 3 MA/cm2. The Q factor of the planar inductive coil at a frequency of 85 MHz was 53000 at a temperature of 77 K.

  15. Neutron-scattering study of spin fluctuations in superconducting YBa2Cu3O6+x (x=0.40, 0.45, 0,50)

    DEFF Research Database (Denmark)

    Chou, H.; Tranquada, J.M.; Shirane, G.;

    1991-01-01

    We show by inelastic neutron scattering that dynamic spin correlations coexist with superconductivity in YBa2Cu3O6+x (x = 0.4,0.45,0.5). For the x = 0.5, T(c) = 50 K sample, the inelastic magnetic intensity at DELTA-E = 6 meV does not show any change near T(c) and is approximately constant from 2...

  16. 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...

  17. 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.

  18. Magnetic field expulsion in superconducting granular ceramics and in polymer/superconductor composites

    Energy Technology Data Exchange (ETDEWEB)

    Benlhachemi, A. [Univ. de Toulon et du Var, La Garde (France). Lab. des Materiaux Multiphases et Interfaces]|[Lab. de Chimie des Solides, Faculte des Sciences, Univ. Ibnou Zohr, Agadir (Morocco); Fremy, M.A.; Breandon, C.; Tatarenko, H.; Gavarri, J.R. [Univ. de Toulon et du Var, La Garde (France). Lab. des Materiaux Multiphases et Interfaces; Benyaich, H. [Lab. de Chimie des Solides, Faculte des Sciences, Univ. Ibnou Zohr, Agadir (Morocco)

    1998-05-01

    The magnetic interaction between a permanent magnet and superconducting ceramics such as YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} and Bi{sub 1.6}Pb{sub 0.4}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub (10+} {sub de} {sub lta)} depend on the superconducting state of each phase and on the junctions between grains. In the case of polymer/superconductor composites, screening effects depend on the volume fraction of superconductor. Measurements of the evolution of the levitation force (F=A/d{sup {gamma}}) as a function of the interaction distance d are used to characterize the effective response of the ceramics or composites to the magnetic flux penetration. Some of the abnormal variations of the exponent {gamma} and of the term A (in F=A/d{sup {gamma}}) could be reinterpreted in terms of a change in superconducting regime. Other observed variations of {gamma} should be due to the variation of the effective field from the cylindrical magnet. (orig.) 19 refs.

  19. Tailoring the Composition and Properties of Sprayed CuSbS2 Thin Films by Using Polymeric Additives

    Directory of Open Access Journals (Sweden)

    Ionut Popovici

    2012-01-01

    Full Text Available CuSbS2 thin films were obtained by spray pyrolysis deposition, using polymeric additives for controlling the surface properties and film’s composition. Ternary crystalline chalcostibite compounds have been obtained without any postdeposition treatments. XRD spectra and IR spectroscopy were used to characterize films composition and interactions between components. Films morphology and surface energy were investigated using AFM microscopy and contact angle measurements. Hydrophobic and hydrophilic polymers strongly influence the composition and film morphology.

  20. Foam behavior of solid glass spheres – Zn22Al2Cu composites under compression stresses

    Energy Technology Data Exchange (ETDEWEB)

    Aragon-Lezama, J.A., E-mail: alja@correo.azc.uam.mx [Departamento de Materiales, Universidad Autónoma Metropolitana-A, Avenida San Pablo 180, Colonia Reynosa Tamaulipas, 02200 México, D.F., México (Mexico); Garcia-Borquez, A., E-mail: a.garciaborquez@yahoo.com.mx [Ciencia de Materiales, ESFM – Instituto Politécnico Nacional, Edif. 9, Unid. Prof. A. Lopez Mateos, Colonia Lindavista, 07738 México, D.F., México (Mexico); Torres-Villaseñor, G., E-mail: gtorres@unam.mx [Departamento de Metálicos y Cerámicos, Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, Apdo., P 70-360, México, D.F., México (Mexico)

    2015-06-25

    Solid glass spheres – Zn22Al2Cu composites, having different densities and microstructures, were elaborated and studied under compression. Their elaboration process involves alloy melting, spheres submersion into the liquid alloy and finally air cooling. The achieved composites with densities 2.6884, 2.7936 and 3.1219 g/cm{sup 3} were studied in casting and thermally induced, fine-grain matrix microstructures. Test samples of the composites were compressed at a 10{sup −3} s{sup −1} strain rate, and their microstructure characterized before and after compression by using optical and scanning electron microscopes. Although they exhibit different compression behavior depending on their density and microstructure, all of them show an elastic region at low strains, reach their maximum stress (σ{sub max}) at hundreds of MPa before the stress fall or collapse up to a lowest yield point (LYP), followed by an important plastic deformation at nearly constant stress (σ{sub p}): beyond this plateau, an extra deformation can be limitedly reached only by a significant stress increase. This behavior under compression stresses is similar to that reported for metal foams, being the composites with fine microstructure which nearest behave to metal foams under this pattern. Nevertheless, the relative values of the elastic modulus, and maximum and plateau stresses do not follow the Ashby equations by changing the relative density. Generally, the studied composites behave as foams under compression, except for their peculiar parameters values (σ{sub max}, LYP, and σ{sub p})

  1. Efficient sorption of Cu(2+) by composite chelating sorbents based on potato starch-graft-polyamidoxime embedded in chitosan beads.

    Science.gov (United States)

    Dragan, Ecaterina Stela; Apopei Loghin, Diana Felicia; Cocarta, Ana Irina

    2014-10-08

    Ionic composites based on cross-linked chitosan (CS) as matrix and poly(amidoxime) grafted on potato starch (AOX) as entrapped chelating resin were prepared as beads, for the first time in this work, by two strategies: (1) thorough mixing of previously prepared AOX in the CS solution followed by the bead formation and (2) thorough mixing of the potato starch-g-poly(acrylonitrile) (PS-g-PAN) copolymer in the initial CS solution, followed by bead formation, the amidoximation of the nitrile groups taking place inside the beads. Ionotropic gelation in tripolyphosphate was used to obtain the composite beads, and in situ covalent cross-linking by epichlorohydrin was carried out to stabilize the beads in the acidic pH range. Fourier transform infrared spectroscopy and the swelling ratio values in the acidic pH range confirmed the influence of the synthesis strategy on the structure of the CS/AOX composites. Scanning electron microscopy was employed to reveal the morphology of the novel composites, both before and after their loading with Cu(2+). The binding capacity of Cu(2+) ions as a function of sorbent composition, synthesis strategy, pH, sorbent dose, contact time, initial concentration of Cu(2+), and temperature was examined in batch mode. The main difference between the composites prepared with the two strategies consisted of the higher sorption capacity and the much faster settlement of the equilibrium sorption for the composite prepared by the in situ amidoximation of PS-g-PAN. The Langmuir, Freundlich, Temkin, Dubinin-Radushkevich, and Sips isotherms were applied to fit the sorption equilibrium data. The maximum equilibrium sorption capacity, qm, evaluated by the Langmuir model at 25 °C was 133.15 mg Cu(2+)/g for the CS/AOX composite beads prepared with the first strategy and 238.14 mg Cu(2+)/g for the CS/AOX composite beads prepared with the second strategy, at the same AOX content. The pseudo-second order kinetic model well fitted the sorption kinetics data

  2. Significance of the Nanograin Size on the H2S-Sensing Ability of CuO-SnO2 Composite Nanofibers

    Directory of Open Access Journals (Sweden)

    Akash Katoch

    2015-01-01

    Full Text Available CuO-SnO2 composite nanofibers with various nanograin sizes were synthesized for investigating their sensing properties with respect to H2S gas. The nanograin size in the CuO-SnO2 composite nanofibers was controlled by changing the thermal treatment duration under isothermal conditions. The nanograin size was found to be critical for the sensing ability of the composite nanofibers. The CuO-SnO2 composite nanofibers comprised of small-sized nanograins were more sensitive to H2S than those with larger-sized nanograins. The superior sensing properties of the CuO-SnO2 composite nanofibers with the smaller nanograins were attributed to the formation of the larger number of p-CuO-n-SnO2 junctions and their transformation to metallic-CuS-n-SnO2 contacts upon exposure to H2S gas. The results suggest that smaller nanograins are conducive to obtaining superior H2S-sensing properties in CuO-SnO2 composite nanofibers.

  3. In situ Fenton reagent generated from TiO2/Cu2O composite film: a new way to utilize TiO2 under visible light irradiation.

    Science.gov (United States)

    Zhang, Yong-Gang; Ma, Li-Li; Li, Jia-Lin; Yu, Ying

    2007-09-01

    TiO2/Cu2O composite is prepared by a simple electrochemical method and coated on glass matrix through a spraying method. The obtained composite is characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The effect of TiO2/Cu2O composite films with different ratio of TiO2 and Cu2O on photodegradation of the dye methylene blue under visible light is investigated in detail. It is found that the photocatalytic activity of TiO2/Cu2O composite film with the presence of FeSO4 and EDTA is much higher than that for the similar system with only TiO2 and Cu2O film respectively. Without the presence of FeSO4 and EDTA, there is no degradation for methylene blue. The exploration of the optimized parameters for the degradation of methylene blue by using TiO2/Cu2O composite film as catalyst under visible light was also carried out. The most significant factor is the amount of Ti02 in the composite, and the second significant factor is the concentration of FeSO4. During the degradation of methylene blue under visible light, TiO2/Cu2O composite film generates H202, and Fenton regent is formed with Fe2+ and EDTA, which is detected in this study. The mechanism for the great improvement of photocatalytic activity of TiO2/Cu2O composite film under visible light is proposed by the valence band theory. Electrons excitated from TiO2/Cu2O composite under visible light are transferred from the conduction band of Cu2O to that of Ti02. The formed intermediate state of Ti 3+ ion is observed by X-ray photoelectron spectroscopy (XPS) on the TiO/Cu2O composite film. Additionally, the accumulated electrons in the conduction band of TiO2 are transferred to oxygen on the TiO2 surface for the formation of O2- or O2(2-), which combines with H+ to form H2O2. The evolved H202 with FeSO4 and EDTA forms Fenton reagentto degrade methylene blue. Compared to the traditional Fenton reagent, this new kind of in situ Fenton reagent generated from TiO2/Cu2O composite film does not need to

  4. Growth of single phase Bi sub 2 Sr sub 2 CaCu sub 2 O sub x whiskers using optimized starting compositions for glassy precursors

    CERN Document Server

    Sugimata, E; Kume, E; Sakai, S

    2003-01-01

    Single phase Bi sub 2 Sr sub 2 CaCu sub 2 O sub x whiskers were grown by optimized starting compositions for glassy precursors. The most optimal starting composition ratio and the composition after the whisker growth were found to be Bi : Sr : Ca : Al = 0.96 : 1.10 : 0.37 : 1.21 : 0.61 and Bi sub 2 sub . sub 2 sub 5 Sr sub 2 sub . sub 0 sub 9 Ca sub 0 sub . sub 8 sub 7 Cu sub 2 sub . sub 0 sub 0 O sub x , respectively. From the results of R-T characteristics, it was determined that there was no intergrowth of the Bi sub 2 Sr sub 2 Ca sub 2 Cu sub 3 O sub x phase. (author)

  5. 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.

  6. High Temperature Flow Stress Prediction of Nano-Al2O3/Cu Composite Using an Artificial Neural Network

    Institute of Scientific and Technical Information of China (English)

    GAO Jian-xin; XU Xiao-feng; SONG Ke-xing; LI Pei-quan; GUO Xiu-hua; LIU Rui-hua

    2006-01-01

    Alumina dispersion strengthened copper composite (nano-Al2O3/Cu composite) was recently emerged as a kind of potentially viable and attractive engineering material for applications requiring high strength, high thermal and electrical conductivities and resistance to softening at elevated temperatures. The nano-Al2O3/Cu composite was produced by internal oxidation. The microstructures of the composite were analyzed by the TEM and its hot deformation behavior was investigated by means of continuous compression tests performed on a Gleeble 1500 thermo-simulator. Making use of the modified algorithm-Levenberg-Marquardt (L-M) algorithm BP neural network, a model for predicting the flow stresses during hot deformation was set up on the base of the experimental data. Results show that the microstructures of the composite are characterized by uniform distribution of nano-Al2O3 particles in Cu-matrix. The sliding of dislocations is the main deformation mechanism. The dynamic recovery is the main softening mode with the flow stress decreasing gently from 500 ℃ to 850 ℃. The recrystallization of Cu-matrix can be retarded late into as high as 850 ℃, when it happens only partially. The well-trained BP neural network model can accurately describe the influence of the temperature, strain rate, and true strain on the flow stresses, therefore, it can precisely predict the flow stresses of the composite under given deforming conditions and provide a new way to optimize hot deforming process parameters.

  7. Development of in-Situ Al-Si/CuAl2 Metal Matrix Composites: Microstructure, Hardness, and Wear Behavior

    Directory of Open Access Journals (Sweden)

    Mahmoud M. Tash

    2016-06-01

    Full Text Available In the present work, in-situ metal matrix composites were fabricated through squeeze casting. The copper particles were dispersed with different weight percentages (3%, 6%, 10%, and 15% into Al-12% Si piston alloy. Also, heat treatments were performed at 380 °C and 450 °C for holding times of 6 and 18 h. The microstructures, X-ray diffractometer (XRD pattern, hardness, and wear characteristics were evaluated. The results showed that these copper particles have reacted with the aluminum under all of the aforementioned processing conditions resulting in the formation of fine copper aluminide intermetallics. Most of the intermetallics were CuAl2, while AlCu appeared in a small ratio. Additionally, these intermetallics were homogenously distributed within the alloy matrix with up to 6% Cu addition. The amounts of those intermetallics increased after performing heat treatment. Most of these intermetallics were CuAl2 at 380 °C, while the Cu-rich intermetallics appeared at 450 °C. Increasing the holding time to 18 h, however, led to grain coarsening and resulted in the formation of some cracks. The hardness of the resulting composite materials was improved. The hardness value reached to about 170 HV after heat treating at 380 °C for 8 h. The wear resistance of the resulting composite materials was remarkably improved, especially at lower additions of Cu and at the lower heat treatment temperature.

  8. Development of in-Situ Al-Si/CuAl2 Metal Matrix Composites: Microstructure, Hardness, and Wear Behavior

    Science.gov (United States)

    Tash, Mahmoud M.; Mahmoud, Essam R. I.

    2016-01-01

    In the present work, in-situ metal matrix composites were fabricated through squeeze casting. The copper particles were dispersed with different weight percentages (3%, 6%, 10%, and 15%) into Al-12% Si piston alloy. Also, heat treatments were performed at 380 °C and 450 °C for holding times of 6 and 18 h. The microstructures, X-ray diffractometer (XRD) pattern, hardness, and wear characteristics were evaluated. The results showed that these copper particles have reacted with the aluminum under all of the aforementioned processing conditions resulting in the formation of fine copper aluminide intermetallics. Most of the intermetallics were CuAl2, while AlCu appeared in a small ratio. Additionally, these intermetallics were homogenously distributed within the alloy matrix with up to 6% Cu addition. The amounts of those intermetallics increased after performing heat treatment. Most of these intermetallics were CuAl2 at 380 °C, while the Cu-rich intermetallics appeared at 450 °C. Increasing the holding time to 18 h, however, led to grain coarsening and resulted in the formation of some cracks. The hardness of the resulting composite materials was improved. The hardness value reached to about 170 HV after heat treating at 380 °C for 8 h. The wear resistance of the resulting composite materials was remarkably improved, especially at lower additions of Cu and at the lower heat treatment temperature. PMID:28773564

  9. Cation composition and oxygen content dependence of crystal structure and T sub c for Tl sub 2 sub - sub x Ba sub 2 Ca sub 2 Cu sub 3 sub + sub z O sub y

    CERN Document Server

    Idemoto, Y; Koura, N; Kamiyama, T; Oikawa, K; Izumi, F

    2003-01-01

    Tl sub 2 sub - sub x Ba sub 2 Ca sub 2 Cu sub 3 sub + sub z O sub y (Tl-2223 system) superconducting oxides with various Tl contents and Cu contents were prepared. We investigated the relation between crystal structure and superconducting property dependence of Tl and Cu content. First, we obtained an almost single-phase material at a Tl content 2-x = 1.7 and the Tl-2223 phase remained the main phase in the region of 2 - x >= 0.631 of Tl sub 2 sub - sub x Ba sub 2 Ca sub 2 Cu sub 3 O sub y. T sub c was about 120 K for the Tl-2223 in a wide range of 0.631 <= 2 - x <= 1.761. Second, we obtained a single-phase at 2 - x = 1.777 and Cu content 3 + z = 3.284 of Tl sub 2 sub - sub x Ba sub 2 Ca sub 2 Cu sub 3 sub + sub z O sub y. The T sub c (zero) dependence of Cu/Tl ratio, showed a maximum value of 122 K at Cu/Tl ratio = 2.026. Based on results of crystal structure refinements by powder neutron diffraction, it was found that the change in bond length and angle dependence of average Cu valence were similar fo...

  10. Rational design of hierarchically-structured CuBi2O4 composites by deliberate manipulation of the nucleation and growth kinetics of CuBi2O4 for environmental applications

    Science.gov (United States)

    Oh, Wen-Da; Lua, Shun-Kuang; Dong, Zhili; Lim, Teik-Thye

    2016-01-01

    A versatile, eco-friendly synthesis scheme was developed to fabricate a series of hierarchically-structured CuBi2O4 composites for environmental applications. By simple tuning of the synthesis protocol (i.e. controlling the ethylene glycol to water ratio in the reaction matrix and employing different auxiliary metal precursors consisting of Cu2+, Co2+ or Fe3+ species), deposition of various metal oxides on CuBi2O4 was achieved. The proposed one-pot synthesis protocol utilizes the fast nucleation and controlled growth kinetics of CuBi2O4 to deliberately immobilize the desired metal oxides on the surface of the CuBi2O4. The manipulation of the diffusion rate, mass transfer kinetics and atomic mobility of the metal precursors by controlling the viscosity and dielectric properties of the reaction matrix lead to the formation of different CuBi2O4 composites with the desired properties. The synergistic coupling effect between the CuBi2O4 and deposited metal oxide contributed to the superior performance of the novel CuBi2O4 composites. The CuBi2O4 composites demonstrate excellent potential for various environmental applications such as being a catalyst for generating sulfate radicals from peroxymonosulfate for organic pollutant removal in water and being a disinfectant. The proposed green synthesis protocol is simple and offers flexibility for fabricating hierarchically-structured CuBi2O4 composites with enhanced properties for targeted applications.A versatile, eco-friendly synthesis scheme was developed to fabricate a series of hierarchically-structured CuBi2O4 composites for environmental applications. By simple tuning of the synthesis protocol (i.e. controlling the ethylene glycol to water ratio in the reaction matrix and employing different auxiliary metal precursors consisting of Cu2+, Co2+ or Fe3+ species), deposition of various metal oxides on CuBi2O4 was achieved. The proposed one-pot synthesis protocol utilizes the fast nucleation and controlled growth kinetics

  11. Compositional dependence of charge carrier transport in kesterite Cu2ZnSnS4 solar cells

    Science.gov (United States)

    Just, Justus; Nichterwitz, Melanie; Lützenkirchen-Hecht, Dirk; Frahm, Ronald; Unold, Thomas

    2016-12-01

    Cu2ZnSnS4 solar cells deposited by thermal co-evaporation have been characterized structurally and electronically to determine the dependence of the electronic properties on the elemental composition of the kesterite phase, which can significantly deviate from the total sample composition. To this end, the kesterite phase content and composition were determined by a combination of X-ray fluorescence and X-ray absorption measurements. The electronic properties, such as carrier density and minority carrier diffusion length, were determined by electron beam induced current measurements and capacitance-voltage profiling. The charge-carrier transport properties are found to strongly depend on the Cu/(Sn+Zn) ratio of the kesterite phase. For the Cu-poor sample, a minority carrier diffusion length of 270 nm and a total collection length of approx. 500 nm are deduced, indicating that current collection should not be an issue in thin devices.

  12. Pb solubility of the high-temperature superconducting phase Bi{sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10+d}

    Energy Technology Data Exchange (ETDEWEB)

    Kaesche, S.; Majewski, P.; Aldinger, F. [Max-Planck-Institut fuer Metallforschung, Stuttgart (Germany)] [and others

    1994-12-31

    For the nominal composition of Bi{sub 2.27x}Pb{sub x}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10+d} the lead content was varied from x=0.05 to 0.45. The compositions were examined between 830{degrees}C and 890{degrees}C which is supposed to be the temperature range over which the so-called 2223 phase (Bi{sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10+d}) is stable. Only compositions between x=0.18 to 0.36 could be synthesized in a single phase state. For x>0.36 a lead containing phase with a stoichiometry of Pb{sub 4}(Sr,Ca){sub 5}CuO{sub d} is formed, for x<0.18 mainly Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+d} and cuprates are the equilibrium phases. The temperature range for the 2223 phase was found to be 830{degrees}C to 890{degrees}C but the 2223 phase has extremely varying cation ratios over this temperature range. Former single phase 2223 samples turn to multi phase samples when annealed at slightly higher or lower temperatures. A decrease in the Pb solubility with increasing temperature was found for the 2223 phase.

  13. Composition control of Cu{sub 2}ZnSnSe{sub 4}-based solar cells grown by coevaporation

    Energy Technology Data Exchange (ETDEWEB)

    Tampo, Hitoshi, E-mail: tampo-21@aist.go.jp; Makita, Kikuo; Komaki, Hironori; Yamada, Akimasa; Furue, Shigenori; Ishizuka, Shogo; Shibata, Hajime; Matsubara, Koji; Niki, Shigeru

    2014-01-31

    The relationship between the composition and conversion efficiency of Cu{sub 2}ZnSnSe{sub 4} (CZTSe)-based solar cells was investigated. CZTSe films were grown by thermal deposition using a coevaporation method. It was found that the composition of CZTSe and Na concentration [Na] have strong correlations to the conversion efficiency, and higher-efficiency samples were obtained with the composition ratios closer to Zn/Sn ∼ 1.6, Cu/(Zn + Sn) ∼ 0.8, and [Na] ∼ 2%. The highest conversion efficiency (η = 2.1%) was obtained in the composition region, and the composition was significantly nonstoichiometric. The CZTSe composition was automatically fixed on a tie line between Cu{sub 2}ZnSnSe{sub 4} and ZnSe, and it was demonstrated that this composition can be expressed by one parameter. The structural and electrical properties of the high- and low-efficiency samples were also investigated. No significant differences in such properties were observed between the high- and low-efficiency samples by surface, x-ray diffraction, and Raman measurements. However, the low-efficiency sample showed a high carrier concentration. - Highlights: • Cu{sub 2}ZnSnSe{sub 4} (CZTSe). • The CZTSe composition and Na concentration strongly affected the efficiency of CZTSe. • The composition of CZTSe was automatically determined on a special tie line. • There were no structural differences between high- and low-efficiency samples. • Low-efficiency samples showed a higher carrier concentration.

  14. Superconducting critical state of Bi[sub 2]Sr[sub 2]CaCu[sub 2]O[sub 8]: two-dimensional effects at low temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez, E. (Comision Nacional de Energia Atomica, Centro Atomico Bariloche (Argentina)); Goffman, M.F. (Comision Nacional de Energia Atomica, Centro Atomico Bariloche (Argentina)); Arribere, A. (Comision Nacional de Energia Atomica, Centro Atomico Bariloche (Argentina)); Cruz, F. de la (Comision Nacional de Energia Atomica, Centro Atomico Bariloche (Argentina)); Schneemeyer, L.F. (AT and T Bell Labs., Murray Hill, NJ (United States))

    1994-02-01

    The critical current in the c direction of Bi[sub 2]Sr[sub 2]CaCu[sub 2]O[sub 8] is shown to increase with temperature in low temperature ZFC measurements. The results are consistent with a loss of the c direction long range phase correlation, induced by the temperature dependent critical current flowing in the ab planes. As a result of this and the loss of the long range correlation induced by thermal disorder, the low temperature electrical resistance of the ZFC critical state is finite at low temperatures, becomes zero and is finite again at higher temperature. (orig.)

  15. Effect of argon-annealing and subsequent oxygen-annealing on the superconductivity and structure of Tl 2CaBa 2Cu 2O 8- x

    Science.gov (United States)

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

    1989-08-01

    Annealing the single-phase Tl 2CaBa 2Cu 2O 8 superconductor ( Tc=108 K) in argon environment at 950 K for 24 h brings the Tc down to ≅80 K. Re-annealing the samples in oxygen under similar conditions restores the Tc to 105±5 K. Rietveld profile refinement of the neutron diffraction spectra of the argon-annealed samples indicates that some Tl-ions, presumably Tl 1+, move from the Tl double-layers to occupy Ca-sites. Upon subsequent annealing in oxygen, however, these Tl-ions escape from the lattice. Implications of this and other structural features are described.

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

    Science.gov (United States)

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

    2014-03-01

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

  17. Influence of the local heating position on the terahertz emission power from high-T{sub c} superconducting Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+δ} mesas

    Energy Technology Data Exchange (ETDEWEB)

    Watanabe, C.; Kitamura, T.; Asanuma, K.; Nakade, K.; Yasui, T.; Saiwai, Y.; Shibano, Y. [Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573 (Japan); Minami, H.; Kashiwagi, T.; Kadowaki, K. [Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573 (Japan); Division of Materials Science, Faculty of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573 (Japan); Yamamoto, T. [Wide Bandgap Materials Group, Optical and Electronic Materials Unit, Environment and Energy Materials Division, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Klemm, Richard A. [Department of Physics, University of Central Florida, Orlando, Florida 32816-2385 (United States)

    2015-01-26

    Simultaneous measurements of spectroscopic terahertz emissions from and SiC photoluminescent local temperature T(r) distributions of high transition temperature T{sub c} superconducting Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+δ} rectangular mesa devices were made. A local region with T(r) > T{sub c} known as a hot spot can emerge with current bias changes. When the hot spot position was moved to a mesa end by locally heating the mesa surface with a laser beam, the intensity of the emission increased, but no changes to its frequency or line width were observed. These results suggest that higher power radiation is attainable by adjusting the hot spot position.

  18. C-axis Josephson plasma resonance observed in Tl(2)Ba(2)CaCu(2)O(8) superconducting thin films by use of terahertz time-domain spectroscopy.

    Science.gov (United States)

    Thorsmølle, V K; Averitt, R D; Maley, M P; Bulaevskii, L N; Helm, C; Taylor, A J

    2001-08-15

    We have unambiguously observed the c -axis Josephson plasma resonance (JPR) in high-critical-temperature (T(c)) cuprate (Tl(2)Ba(2)CaCu(2)O(8)) superconducting thin films, employing terahertz time-domain spectroscopy in transmission as a function of temperature in zero magnetic field. These are believed to be the first measurements of the JPR temperature dependence of a high-T(c) material in transmission. With increasing temperature, the JPR shifts from 705 GHz at 10 K to ~170 GHz at 98 K, corresponding to an increase in c-axis penetration depth from 22.4+/-0.6mum to 94+/-9mum . The linewidth of the JPR peak increases with temperature, which indicates an increase in the quasi-particle scattering rate. We have probed the onset of the c -axis phase coherence to ~0.95T(c) . The JPR vanishes above T(c) as expected.

  19. Manufacturing of superconductive silver/ceramic composites

    DEFF Research Database (Denmark)

    Seifi, Behrouz; Bech, Jakob Ilsted; Eriksen, Morten

    2000-01-01

    Manufacturing of superconducting metal/ceramic composites is a rather new discipline within materials forming processes. High Temperature SuperConductors, HTSC, are manufactured applying the Oxide-Powder-In-Tube process, OPIT. A ceramic powder containing lead, calcium, bismuth, strontium...... and current leading properties of the final superconducting fibres. The present work describes studies on alternative packing geometries and process parameters in the flat rolling operations. The aim is to obtain homogenous filaments with advantageous geometry and good texture while avoiding potential defects...

  20. 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.

  1. High pressure synthesis and superconducting properties for the multi-layered Ba{sub 2}Ca {sub n-1}Cu {sub n}O{sub 2n}(O,F){sub 2} (n = 4 and 5)

    Energy Technology Data Exchange (ETDEWEB)

    Kito, Hijiri [National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 2, 1-1-1, Umezono, Tsukuba, Ibaraki, 305-8568 (Japan)]. E-mail: h.kito@aist.go.jp; Iyo, Akira [National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 2, 1-1-1, Umezono, Tsukuba, Ibaraki, 305-8568 (Japan)

    2006-10-01

    We prepared multi-layered oxyfluoride superconductors, Ba{sub 2}Ca {sub n-1}Cu {sub n}O{sub 2n}(O,F){sub 2} (n = 4 and 5) using high-pressure apparatus. These phase are the n = 4 and 5 members of a homologous series, M{sub 2}Ca {sub n-1}Cu {sub n}O{sub 2n}(O,F){sub 2} [0{sup M}2(n - 1)n-F] reported previously. X-ray studies indicated that they have tetragonal structures with a = 3.863 A, c = 33.75 A for n = 4 and a = 3.862 A, c = 40.18 A for n = 5. Superconducting transition temperature were 86.6 K for n = 4 and 75.7 K for n = 5, respectively. The critical current density (J {sub c}) and irreversibility field (H {sub irr}) were determined from M-H curves using the Bean's model. J {sub c} and H {sub irr} of 0{sup Ba}2(n - 1)n-F (n = 4 and 5) decreased rapidly with increasing temperature. J {sub c} (5 K, 1 T) shows 1.70 x 10{sup 6} A/cm{sup 2} for n = 4 and 1.93 x 10{sup 5} A/cm{sup 2} for n = 5. The estimated values of H {sub irr} (5 K) are about 70 T for n = 4 and 17 T for n = 5.

  2. Processing and fabrication of YBa2Cu3O(x)/Ag composite wires and coils

    Science.gov (United States)

    Ferrando, W. A.; Divecha, A. P.; Mansour, A. N.; Karmarkar, S. D.; Balachandran, U.; Dorris, S. E.; Dusek, J. T.; Picciolo, J. J.; Singh, J. P.; Poeppel, R. B.

    1990-11-01

    Silver was added to YBa2Cu3O(x) (123) powder by a melt technique using AgNO3 and heated to approx. 600 C to decompose the nitrate. This process yields 123 powder that is uniformly coated with Ag, as indicated by optical and scanning electron microscopy (SEM). The composite power is formed into rods (approx. 4 mm diameter) via drawing and swaging through conical converging dies. Wires of finer diameter (approx. 1 mm) and substantially greater linear uniformity were produced by slurry extrusion of the composite powder in a polymeric vehicle. Transport critical current density, J sub c, of these wires at present is about 750 A/sq cm. This value may be expected to rise due to further reduction of second phase impurities localized at grain boundaries and better understanding of the Ag/superconductor interface. The wire fabrication is described in some detail and discusses the results of microscopic analyses by scanning electron microscopy (SEM), x ray photoemission spectroscopy (XPS), and x ray diffraction (XRD).

  3. Dopant-site occupancies and superconducting properties of the Fe-substituted La 2.5Nd 0.5CaBa 3(Cu 1-xFe x) 7O z perovskite

    Science.gov (United States)

    Kundaliya, Darshan C.; Vij, Reeta; Kuberkar, D. G.; Kulkarni, R. G.

    2000-12-01

    The structural and superconducting properties of single-phase Fe-substituted La 2.5Nd 0.5CaBa 3(Cu 1-xFe x) 7O z (LNCBCuFe) with 0.0⩽ x⩽0.06 compounds having triple-perovskite structure are investigated using X-ray diffraction, a.c. susceptibility, d.c. magnetization, oxygen content and Mössbauer effect measurements. Mössbauer spectral analysis of x=0.03 sample displays unusual Fe-dopant site occupancies and the Cu(2) plane to Cu(1) chain site ratio in the LNCBCuFe are quite different from those of the usual Fe-doped YBa 2Cu 3O 7-δ. Specifically, we observe substantial occupation of a new chain-associated quasi-octahedral site, E, at 300 K which transforms into the well-known distorted tetrahedron chain site, A, on lowering the temperature to 78 K. The observed reduction of Tc with increasing x in LNCBCuFe supports the view that the hole filling mechanism contributes predominantly to the suppression of superconductivity by Fe.

  4. Investigation of inter-grain critical current density in Bi2Sr2CaCu2O8+δ superconducting wires and its relationship with the heat treatment protocol

    Science.gov (United States)

    Pallecchi, I.; Leveratto, A.; Braccini, V.; Zunino, V.; Malagoli, A.

    2017-09-01

    In this work we investigate the effect of each different heat treatment stage in the fabrication of Bi2Sr2CaCu2O8+δ superconducting wires on intra-grain and inter-grain superconducting properties. We measure magnetic critical temperature T c values and transport critical current density J c at temperatures from 4 K to 40 K and in fields up to 7 T. From an analysis of the temperature dependence of the self-field critical current density J c(T) that takes into account weak link behavior and the proximity effect, we study grain boundary (GB) transparency to supercurrents; we also establish a relationship between GB oxygenation in the different steps of the fabrication process and GB transparency to supercurrents. We find that GB oxygenation starts in the first crystallization stage, but it becomes complete in the plateau at 836 °C and in slow cooling stages and is further enhanced in the prolonged post-annealing step. Such oxygenation makes GBs more conductive, thus improving the inter-grain J c value and temperature dependence. On the other hand, from inspection of the T c values in the framework of the phase diagram dome, we find that grains are already oxygenated in the crystallization step up to the optimal doping, while successive slow cooling and post-annealing treatments further enhance the degree of overdoping, especially if carried out in oxygen atmosphere rather than in air.

  5. Ultrafast electron relaxation in superconducting Bi(2)Sr(2)CaCu(2)O(8+delta) by time-resolved photoelectron spectroscopy.

    Science.gov (United States)

    Perfetti, L; Loukakos, P A; Lisowski, M; Bovensiepen, U; Eisaki, H; Wolf, M

    2007-11-09

    Time-resolved photoelectron spectroscopy is employed to study the dynamics of photoexcited electrons in optimally doped Bi{2}Sr{2}CaCu{2}O{8+delta} (Bi-2212). Hot electrons thermalize in less than 50 fs and dissipate their energy on two distinct time scales (110 fs and 2 ps). These are attributed to the generation and subsequent decay of nonequilibrium phonons, respectively. We conclude that 20% of the total lattice modes dominate the coupling strength and estimate the second momentum of the Eliashberg coupling function lambdaOmega{0}{2}=360+/-30 meV{2}. For the typical phonon energy of copper-oxygen bonds (Omega{0} approximately 40-70 meV), this results in an average electron-phonon coupling lambda<0.25.

  6. 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.

  7. Synthesis of Ordered Mesoporous CuO/CeO2 Composite Frameworks as Anode Catalysts for Water Oxidation

    Directory of Open Access Journals (Sweden)

    Vassiliki Markoulaki Ι

    2015-11-01

    Full Text Available Cerium-rich metal oxide materials have recently emerged as promising candidates for the photocatalytic oxygen evolution reaction (OER. In this article, we report the synthesis of ordered mesoporous CuO/CeO2 composite frameworks with different contents of copper(II oxide and demonstrate their activity for photocatalytic O2 production via UV-Vis light-driven oxidation of water. Mesoporous CuO/CeO2 materials have been successfully prepared by a nanocasting route, using mesoporous silica as a rigid template. X-ray diffraction, electron transmission microscopy and N2 porosimetry characterization of the as-prepared products reveal a mesoporous structure composed of parallel arranged nanorods, with a large surface area and a narrow pore size distribution. The molecular structure and optical properties of the composite materials were investigated with Raman and UV-Vis/NIR diffuse reflectance spectroscopy. Catalytic results indicated that incorporation of CuO clusters in the CeO2 lattice improved the photochemical properties. As a result, the CuO/CeO2 composite catalyst containing ~38 wt % CuO reaches a high O2 evolution rate of ~19.6 µmol·h−1 (or 392 µmol·h−1·g−1 with an apparent quantum efficiency of 17.6% at λ = 365 ± 10 nm. This OER activity compares favorably with that obtained from the non-porous CuO/CeO2 counterpart (~1.3 µmol·h−1 and pure mesoporous CeO2 (~1 µmol·h−1.

  8. Effect of Pr doping on the growth and superconducting properties of (Y{sub 1-x}Pr{sub x})Ba{sub 2}Cu{sub 3}O{sub 7-{delta}}

    Energy Technology Data Exchange (ETDEWEB)

    Xu, X Q; Cai, Y Q; Yang, C X; Yao, X [Department of Physics, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240 (China); Xu, S [Instrumental Analysis Centre, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240 (China); Kortyka, A; Puzniak, R [Institute of Physics, Polish Academy of Sciences, PL 02-668 Warsaw (Poland)], E-mail: xyao@sjtu.edu.cn

    2009-01-15

    (Y{sub 1-x}Pr{sub x})Ba{sub 2}Cu{sub 3}O{sub 7-{delta}} (Pr-YBCO, x<0.2) single crystals and single domain bulks were grown by the top-seeded solution-growth (TSSG) and the top-seeding melt-textured growth (TSMTG) methods, respectively. The superconducting critical temperature (T{sub c}) was determined by magnetic measurements and the critical current density (J{sub c}) was estimated by applying the modified Bean model. For a low-level substitution (x<0.025), an increase in the J{sub c} value as compared with that for unsubstituted YBCO was found while no apparent change in the T{sub c} value was noticed. On the other hand, Pr substitution in YBCO leads to: (i) increasing liquid solubility of the total rare earth element in the Ba-Cu-O solution, (ii) increasing peritectic temperature (T{sub p}), and (iii) a decrease in the liquidus slope near the T{sub p}. As a result, the driving force for YBCO growth and the region of single grain growth are enhanced. Study of the compositional correlation between liquid and solid additionally indicates that the Pr distribution coefficient is larger than 1 in the Pr-YBCO system. Thus the Pr content and then the T{sub p} value of Pr-YBCO in the bulk reduce with the growth time during TSMTG. The lower T{sub p} value in the final crystallized part is beneficial to a slow cooling process. Using the TSMTG method, Pr-YBCO (x = 0.02) monodomains up to 42 mm in diameter were grown with a high growth rate.

  9. Microstructure and mechanical properties investigation of in situ TiB2 and ZrB2 reinforced Al-4Cu composites

    Science.gov (United States)

    Lutfi Anis, Ahmad; Ramli, Rosmamuhammadani; Darham, Widyani; Zakaria, Azlan; Talari, Mahesh Kumar

    2016-02-01

    Conventional Al-Cu alloys exhibit coarse grain structure leading to inferior mechanical properties in as-cast condition. Expensive thermo-mechanical treatments are needed to improve microstructure and corresponding mechanical properties. In situ Al-based composites were developed to improve mechanical properties by dispersion strengthening and grain refinement obtained by the presence of particulates in the melt during solidification. In this work Al-4Cu - 3TiB2 and Al-4Cu-3ZrB2 in situ composites were prepared by liquid casting method. XRD, electron microscopy and mechanical tests were performed on suitably sectioned and metallographically prepared surfaces to investigate the phase distribution, hardness and tensile properties. It was found that the reinforcement particles were segregated along the grain boundaries of Al dendrites. Tensile fracture morphology for both Al-4Cu - 3TiB2 and Al-4Cu-3ZrB2 were analyzed and compared to determine the fracture propagation mechanism in the composites. Al-4Cu-3ZrB2 in situ composites displayed higher strength and hardness compared to Al-4Cu-3TiB2 which could be ascribed to the stronger interfacial bonding between the Al dendrites and ZrB2 particulates as evidenced from fractographs.

  10. Effect of La2O3 on electrical friction and wear properties of Cu-graphite composites

    Institute of Scientific and Technical Information of China (English)

    莫飞; 凤仪; 陈阳明; 王雨晴; 钱刚; 豆亚坤; 张学斌

    2015-01-01

    Sliding friction and wear experiments using Cu-La2O3-graphite composites against Cu-5 wt.%Ag alloy ring were con-ducted at a constant sliding speed of 10 m/s, a current density of 10 A/cm2 and a load of 2.5 N/cm2. These composites with different La2O3and graphite contents were fabricated by hot-pressing. Physical and mechanical properties of the composites were examined. Morphologies of the worn surface of composites were observed using optical microscopy. X-ray photoelectron spectroscopy spectra were used to study compositions of the lubricating film. The results showed that with the increasing addition of La2O3, hardness, flexural strength and electrical resistivity increased, but the relative density dropped. The friction coefficient increased with the in-creasing addition of La2O3. Composite containing 3 vol.% of La2O3 and 37 vol.% of graphite showed the best wear resistance. The main wear mechanisms of composites were abrasive wear, oxidative wear and adhesive wear.

  11. Crossovers in the out-of-plane resistivity of superconducting Tl2Ba2CaCu2O8 single crystals

    Science.gov (United States)

    Salvetat, J.-P.; Berger, H.; Halbritter, A.; Mihály, G.; Pavuna, D.; Forró, L.

    2000-12-01

    We report the in-plane (ρab) and out-of-plane (ρc) resistivities in the 4 800 K range on single crystals of Tl2Ba2CaCu2O8 high-Tc cuprate with Tc = 111 K (ρc/ρab approx 1000). ρab(T) exhibits "usual" linear behavior and ρc(T) follows generally metallic-like, positive slope in the 150 400 K temperature range. There is a clear crossover to semiconductor-like behavior close to Tc. However, for the first time in a chainless high-Tc cuprate we observe a crossover above 500 K due to hopping conduction. Under high pressures ( < 15 kbar) the magnitude of ρc strongly decreases, yet the ρc(T) slope does not change. This suggests that the out-of-plane charge transport is governed by the interplane tunneling rate.

  12. (Pt{sub 1–x}Cu{sub x}){sub 3}Cu{sub 2}B and Pt{sub 9}Cu{sub 3}B{sub 5}, the first examples of copper platinum borides. Observation of superconductivity in a novel boron filled β-Mn-type compound

    Energy Technology Data Exchange (ETDEWEB)

    Salamakha, Leonid P. [Institute of Solid State Physics, TU Wien, A-1040 Wien (Austria); Sologub, Oksana, E-mail: oksana.sologub@univie.ac.at [Institute of Solid State Physics, TU Wien, A-1040 Wien (Austria); Stöger, Berthold [Institute of Chemical Technologies and Analytics, TU Wien, A-1040 Wien (Austria); Michor, Herwig; Bauer, Ernst [Institute of Solid State Physics, TU Wien, A-1040 Wien (Austria); Rogl, Peter F. [Institute of Physical Chemistry, University of Vienna, A-1090 Wien (Austria)

    2015-09-15

    New ternary copper platinum borides have been synthesized by arc melting of pure elements followed by annealing at 600 °C. The structures have been studied by X-ray single crystal and powder diffraction. (Pt{sub 1−x}Cu{sub x}){sub 3}Cu{sub 2}B (x=0.33) forms a B-filled β-Mn-type structure (space group P4{sub 1}32; a=0.6671(1) nm). Cu atoms are distributed preferentially on the 8c atom sites, whereas the 12d site is randomly occupied by Pt and Cu atoms (0.670(4) Pt±0.330(4) Cu). Boron is located in octahedral voids of the parent β-Mn-type structure. Pt{sub 9}Cu{sub 3}B{sub 5} (space group P-62m; a=0.9048(3) nm, c=0.2908(1) nm) adopts the Pt{sub 9}Zn{sub 3}B{sub 5–δ}-type structure. It has a columnar architecture along the short translation vector exhibiting three kinds of [Pt{sub 6}] trigonal prism columns (boron filled, boron semi-filled and empty) and Pt channels with a pentagonal cross section filled with Cu atoms. The striking structural feature is a [Pt{sub 6}] cluster in form of an empty trigonal prism at the origin of the unit cell, which is surrounded by coupled [BPt{sub 6}] and [Pt{sub 6}] trigonal prisms, rotated perpendicularly to the central one. There is no B–B contact as well as Cu–B contact in the structure. The relationships of Pt{sub 9}Cu{sub 3}B{sub 5} structure with the structure of Ti{sub 1+x}Os{sub 2−x}RuB{sub 2} as well as with the structure families of metal sulfides and aluminides have been elucidated. (Pt{sub 1–x}Cu{sub x}){sub 3}Cu{sub 2}B (x=0.3) (B-filled β-Mn-type structure) is a bulk superconductor with a transition temperature of about 2.06 K and an upper critical field μ{sub 0}H{sub C2}(0){sup WHH} of 1.2 T, whereas no superconducting transition has been observed up to 0.3 K in Pt{sub 9}Cu{sub 3}B{sub 5} (Pt{sub 9}Zn{sub 3}B{sub 5–δ}-type structure) from electrical resistivity measurements. - Highlights: • First two copper platinum borides, (Pt{sub 0.67}Cu{sub 0.33}){sub 3}Cu{sub 2}B and Pt{sub 9}Cu{sub 3}B

  13. New system for manipulation of nanoobjects based on composite Ti2NiCu/Pt nanotweezers with shape memory effect

    Science.gov (United States)

    Zhikharev, A. M.; Irzhak, A. V.; Beresin, M. Y.; Lega, P. V.; Koledov, V. V.; Kasyanov, N. N.; Martynov, G. S.

    2016-08-01

    We report the new system for manipulation of nanoobjects based on composite Ti2NiCu/Pt nanotweezers with shape memory effect. The design consists of the bimetallic Ti2NiCu/Pt shape memory nanotweezers placed on a tip of electrochemically etched tungsten needle. The semiconductor diode placed on the tip of the needle plays both role of resistive element of the heater and temperature sensor for feedback control loop closing. The device is compatible with existing positioning systems like OmniProbe®, Kleindiek®, etc. and may find numerous practical applications in various tasks of nanotechnology connected with 3D manipulation.

  14. The Process of TiB2-Cu Composite Phase and Structure Formation during Combustion Synthesis

    Institute of Scientific and Technical Information of China (English)

    XU Qiang; ZHANG Xinghong; HAN Jiecai; PAN Wei

    2006-01-01

    The reaction process of combustion synthesis for TiB2- Cu was investigated in detail using combustion-wave arresting experiment, X-ray diffraction (XRD) analysis, SEM analysis and differential thermal analysis ( DTA ). The XRD analysis results for the different parts of the quenched specimen shaw that TiCux intermetallic phase firstly forms with the propagation of combustion wave, and then Ti1.87 B50 and Ti3 B4 metastable phases come forth due to the diffusion of B atoms and finally the stable TiB2 phase forms because of the continuous diffusion of B atoms. The formation of TiB2 phase is not completed by one step, but undergoes several transient processes. The process of reaction synthesis for Ti-B-Cu ternary system can be divided into three main stages: melting of Cu and Ti, and the formation of Cu- Ti melt and few TiCux , TiBx intermetallic phases; large numbers of TiCux intermetallic phases formation and some fine TiB2 particles precipitation; and the TiB2 particles coarsening and the stable TiB2 and Cu two phases formation in the final product.

  15. Trapped magnetic-field properties of prototype for Gd-Ba-Cu-O/MgB2 hybrid-type superconducting bulk magnet

    Science.gov (United States)

    Naito, Tomoyuki; Mochizuki, Hidehiko; Fujishiro, Hiroyuki; Teshima, Hidekazu

    2016-03-01

    We have studied experimentally and numerically the trapped magnetic-field properties of a hybrid-type superconducting bulk magnet, which comprised an inner Gd-Ba-Cu-O (GdBCO) disk-bulk and an outer MgB2 ring-bulk, under field-cooled magnetization (FCM) and pulsed-field magnetization (PFM). The trapped field by FCM at the center of the hybrid bulk was 4.5 T at 20 K, which was 0.2 T higher than that of the inner GdBCO disk-bulk without MgB2 ring-bulk. The experimental results by FCM were quantitatively reproduced by the numerical estimations for a model, which makes it possible to understand the trapped field properties of the hybrid bulk. The total magnetic flux by FCM, which was estimated numerically, was enhanced by about 1.7 times from 0.91 mWb of the single GdBCO bulk to 1.53 mWb of the hybrid bulk. We also succeeded in magnetizing the whole hybrid bulk by applying multi-pulsed-fields. The central trapped field of 1.88 T was not enhanced, but the total magnetic flux, which was obtained experimentally, was evidently increased by 2.5 times (0.25 \\to 0.62 mWb) for the hybrid bulk. The obtained results suggest that the hybridization is effective to enhance the total magnetic flux. To confirm the reinforcing effect of the MgB2 ring to the GdBCO disk during the cooling and magnetization processes, we have measured the thermal dilatation, {\\text{}}{dL}({\\text{}}T)/{\\text{}}L(300 K), of the GdBCO, MgB2 and stainless steel. As a result, the thermal dilatation of MgB2 was smaller than that of GdBCO. MgB2 ring-bulk shows no compression effect to resist the hoop stress of the GdBCO disk-bulk during the FCM process. The reinforcing material such as the stainless steel ring must be set outside the GdBCO disk-bulk.

  16. Combinatorial search of superconductivity in Fe-B composition spreads

    Directory of Open Access Journals (Sweden)

    Kui Jin

    2013-10-01

    Full Text Available We have fabricated Fe-B thin film composition spreads in search of possible superconducting phases following a theoretical prediction by Kolmogorov [Phys. Rev. Lett. 105, 217003 (2010]. Co-sputtering was used to deposit spreads covering a large compositional region of the Fe-B binary phase diagram. A trace of superconducting phase was found in the nanocrystalline part of the spread, where the film undergoes a metal to insulator transition as a function of composition in a region with the average composition of FeB2. The resistance drop occurs at 4 K, and a diamagnetic signal has also been detected at the same temperature. From the field-dependent resistive transition behavior, we estimate the upper critical field to be approximately 2 T.

  17. 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.

  18. Effect of Pr doping on the growth and superconducting properties of (Y1-xPrx)Ba2Cu3O7-δ

    Science.gov (United States)

    Xu, X. Q.; Cai, Y. Q.; Yang, C. X.; Yao, X.; Xu, S.; Kortyka, A.; Puzniak, R.

    2009-01-01

    (Y1-xPrx)Ba2Cu3O7-δ (Pr-YBCO, xBean model. For a low-level substitution (x<0.025), an increase in the Jc value as compared with that for unsubstituted YBCO was found while no apparent change in the Tc value was noticed. On the other hand, Pr substitution in YBCO leads to: (i) increasing liquid solubility of the total rare earth element in the Ba-Cu-O solution, (ii) increasing peritectic temperature (Tp), and (iii) a decrease in the liquidus slope near the Tp. As a result, the driving force for YBCO growth and the region of single grain growth are enhanced. Study of the compositional correlation between liquid and solid additionally indicates that the Pr distribution coefficient is larger than 1 in the Pr-YBCO system. Thus the Pr content and then the Tp value of Pr-YBCO in the bulk reduce with the growth time during TSMTG. The lower Tp value in the final crystallized part is beneficial to a slow cooling process. Using the TSMTG method, Pr-YBCO (x = 0.02) monodomains up to 42 mm in diameter were grown with a high growth rate.

  19. Phase transition study in a [Cu2HgI4 : 0.AgI] mixed composite system

    Indian Academy of Sciences (India)

    Noorussaba; Afaq Ahmad

    2010-08-01

    A novel composite superionic system, [Cu2HgI4 : 0.AgI], ( = 0.2, 0.4, 0.6 mol wt.%), was prepared. A [Cu2HgI4] system was used as the host. Electrical conductivity was measured to study the transition behaviour at frequencies of 100 Hz, 120 Hz, 1 kHz and 10 kHz in the temperature range 90–170°C using a Gen Rad 1659 RLC Digibridge. Conductivity increased sharply during the – phase transition. Upon increasing the dopant-to-host ratio, the conductivity of the superionic system exhibited Arrhenius (thermally activated)-type behaviour. DTA, DTG, TGA and X-ray powder diffraction were performed to confirm doping effect and transition in the host. The phase transition temperature increased with an increase in the dopant concentration. Activation energies in eV for pre- and post-transition phase behaviour are also reported. Due to an interaction between [Cu2HgI4] and AgI, the addition of AgI to [Cu2HgI4] shifted the phase transition of the host [Cu2HgI4].

  20. Negative oxygen isotope effect on the static spin stripe order in superconducting La(2-x)Ba(x)CuO(4) (x=1/8) observed by muon-spin rotation.

    Science.gov (United States)

    Guguchia, Z; Khasanov, R; Bendele, M; Pomjakushina, E; Conder, K; Shengelaya, A; Keller, H

    2014-08-01

    Large negative oxygen-isotope (^{16}O and ^{18}O) effects (OIEs) on the static spin-stripe-ordering temperature T_{so} and the magnetic volume fraction V_{m} were observed in La_{2-x}Ba_{x}CuO_{4}(x=1/8) by means of muon-spin-rotation experiments. The corresponding OIE exponents were found to be α_{T_{so}}=-0.57(6) and α_{V_{m}}=-0.71(9), which are sign reversed to α_{T_{c}}=0.46(6) measured for the superconducting transition temperature T_{c}. This indicates that the electron-lattice interaction is involved in the stripe formation and plays an important role in the competition between bulk superconductivity and static stripe order in the cuprates.

  1. Fabrication of Cu2O-TiO2 Nano-composite with High Photocatalytic Performance under Simulated Solar Light

    Directory of Open Access Journals (Sweden)

    Yi Wentao

    2016-01-01

    Full Text Available Cu2O-P25 (TiO2 nano-heterostructures with different mass ratios were synthesized via a wet chemical precipitation and hydrothermal method, and were characterized by X-ray diffraction (XRD, field-emission scanning electron microscopy (FESEM, UV-vis diffuse reflectance spectra (DRS, and X-ray photoelectron spectroscopy (XPS. DRS results showed that the light absorption of P25 extended to the visible light region with the loading of Cu2O. XPS results showed that Cu existed in the state of Cu+ in the presence of hydroxylamine hydrochloride, confirming the formation of Cu2O. The obtained products exhibited efficient photocatalytic performance in degradation of methyl orange (MO and methylene blue (MB under simulated solar light. The sample of 5% Cu2O-P25 exhibited the highest photocatalytic activity among all as-prepared samples. And the photocatalysts can be recycled without obvious loss of photocatalytic activity.

  2. Study of structural and magnetic properties of (Co–Cu)Fe{sub 2}O{sub 4}/PANI composites

    Energy Technology Data Exchange (ETDEWEB)

    Hashim, Mohd., E-mail: md.hashim09@gmail.com [Department of Applied Physics, Aligarh Muslim University, Aligarh 202 002 (India); Alimuddin [Department of Applied Physics, Aligarh Muslim University, Aligarh 202 002 (India); Shirsath, Sagar E. [Spin Device Technology Centre, Department of Information Engineering, Shinshu University, Nagano 380-8553 (Japan); Meena, S.S. [Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Kotnala, R.K. [National Physical Laboratory (CSIR), Dr. K.S. Krishnan Road, New Delhi 110 012 (India); Kumar, Shalendra [Department of Physics, Pohang University of Science and Technology, Pohang 790-784 (Korea, Republic of); Bhatt, Pramod [Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Jotania, R.B. [Department of Physics, School of Science, Gujarat University, Ahmedabad 380 009 (India); Kumar, Ravi [Centre for Material Science Engineering, National Institute of Technology, Hamirpur 171 005, HP (India)

    2013-08-15

    The nanocomposites of the polyaniline and Co{sub 1−x}Cu{sub x}Fe{sub 2}O{sub 4} (PANI/CoCuFe) were prepared by in-situ oxidative polymerization of aniline. Prepared nanocomposites samples were characterized by using various experimental techniques like X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FT-IR), field emission scanning electron microscope (FE-SEM), vibrating sample magnetometer (VSM), Mössbauer spectroscopy and ultraviolet–visible spectrophotometry (UV–VIS). The elemental analysis as obtained from the energy dispersive X-ray spectroscopy (EDAX) measurement is in close agreement with the expected composition from the stoichiometry of the reactant solutions. XRD result confirms that all the samples have the single phase cubic spinel structure. Unit cell parameter ‘a’ is found to decrease with the increase in copper ion substitution. The crystallite size was investigated by using the Debye–Scherer formula and it was found in the range of ∼28–37 nm. FE-SEM confirmed the homogeneous and well defined surface morphology of the synthesized samples. FT-IR study showed the main absorption bands corresponding to the spinel structure those arose due to the tetrahedral and octahedral stretching vibrations. Cation distribution was estimated using XRD data. Hysteresis measurements revealed that the saturation magnetization decreased with increase in Cu{sup 2+} substitution. Magnetic environment of {sup 57}Fe in Cu-doped cobalt ferrite was investigated by using Mössbauer spectroscopy. Mössbauer study evidenced the ferrimagnetic behavior of the synthesized samples. - Highlights: • Crystallite size decreases with increasing Cu{sup 2+} substitution. • The prepared samples show the formation of single phase cubic spinel structure. • Cation distribution shows that Cu and Co ions shows strong preference toward octahedral B site. • Magnetization decreases with increasing Cu{sup 2+} substitution. • Mössbauer study shows

  3. 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.

  4. 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.

  5. 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.

  6. Preparation of CuAlO2 and Photocatalytic Performance of Composite Catalysts%CuAlO2的合成及其复合催化剂的光催化性能

    Institute of Scientific and Technical Information of China (English)

    康园丽; 王桂赟; 刘宗园; 王延吉

    2012-01-01

    Delafossite CuA102 is prepared by thermal treatment the precursor obtained via a serai-wet method using Cu(N03)2 and A1(NO3)3 as raw material ,and oxalic acid as precipitant of copper ion under nitrogen atmosphere. The samples are characterized by thermal gravimetric analysis (TG), X-ray diffraction (XRD), ultraviolet visible diffuse reflectance(UV-Vis-DR) and transmission electron microscope(TEM). The formation process of the CuA102 is researched. With increasing the thermal treatment temperature of the precursor, firstly the CuO and Cu2O are generated, and then intermediate phase of CuAl2O4 appeared, finally no impurity phase CuA102 formed. The results shows that the synthesized CuA102 has good crystal perfection and its direct band gap is about 3.1 eV. The n-p composite photocatalysts W0rCuA102, Ti0rCuA102 and Zn0-CuA102 are prepared by precipitation composite method. The composite photocatalysts are characterized by XRD and TEM, and the photocatalytic performance of the catalysts are tested, and the results indicate that all the composite catalysts mentioned above are all made up two phases, and they all have photocatalytic activity for decomposing pure water into hydrogen under the UV-light irradiation.%以硝酸铜和硝酸铝为原料,草酸为铜离子的沉淀剂,半湿法制得前驱体,再于氮气气氛下热处理形成了铜铁矿结构的CuAlO2.对样品进行热失重(TG),X射线衍射(XRD),紫外-可见漫反射(UV-Vis-DR)及透射电镜(rEM)表征分析,探讨了CuAlO2的形成过程.结果显示,随着热处理温度的升高,含铜物质经历了由CuO、Cu2O到CuAl2O4,再到CuAlO2的变化历程;制得的CuAlO2晶体结晶完整性较好,直接禁带宽度为3.1 eV左右.用沉淀复合的方法制备出了n-p异质复合型光催化剂WO3-CuAlO2、TiO2-CuAlO2和ZnO-CuAlO2,对复合催化剂进行了XRD和TEM表征分析,并测试了复合催化剂的光催化活性.结果表明,上述催化剂均由两种物相复合而成,且在紫外光

  7. Investigation of lattice defects and compositional gradients in Cu(In,Ga)Se{sub 2} thin films for solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Dietrich, Jens; Boit, Christian [Department of Semiconductor Devices, Berlin University of Technology, Einsteinufer 19, 10587 Berlin (Germany); Abou-Ras, Daniel; Rissom, Thorsten; Unold, Thomas; Schock, Hans-Werner [Helmholtz-Zentrum Berlin fuer Materialien und Energie, Hahn-Meitner-Platz 1, 14109 Berlin (Germany)

    2011-07-01

    Cu(In,Ga)Se{sub 2} absorber layers used in thin-film solar cells exhibit, when grown in a multi-stage process, compositional gradients of gallium and indium, dependent on process parameters such as the Ga content. The high lateral resolution of transmission electron microscopy (TEM) imaging and energy-dispersive X-ray spectroscopy (EDX) allows the determination of lattice defects and the elemental concentrations at identical sample positions. Cross-sectional TEM samples of ZnO/CdS/Cu(In,Ga)Se{sub 2}/Mo/glass stacks were prepared with varying [Ga]/([In]+[Ga]) ratio in the absorber. The shape of the Ga distribution was measured by means of EDX and differs for the various [Ga]/([In]+[Ga]) ratios. Linear (dislocations) and planar defects (stacking faults, microtwins) were studied by means of TEM bright field and dark field images along the lengths of the Cu(In,Ga)Se{sub 2} layers. Strong Ga compositional gradients were found even within individual grains. It appears that these Ga gradients correlate with the occurrence of dislocation networks in large grains (diameter > 1 {mu}m). We assume that these dislocations compensate for lattice mismatch due to the change in composition in this area of the lattice.

  8. Influence of Milling Time on the Crystallite Size of AlSi5Cu2/SiC Composite Powder

    Directory of Open Access Journals (Sweden)

    Suśniak M.

    2016-06-01

    Full Text Available AlSi5Cu2/SiC nanocrystalline composite powder was successfully obtained by mechanical alloying of AlSi5Cu2 chips with reinforcement of 0, 10, 15, 20 wt. % of silicon carbide. X-ray powder diffraction was used to characterize obtained material. Detailed analyses using transmission and scanning electron microscopy have been conducted in order to collaborate the grain size measurement determined from the XRD analyses. Powders produced in a planetary ball mill with milling time: 1, 5, 10, 15, 20 and 40 hours, have shown shape and size evaluation during mechanical alloying process. It can be seen tendency to decrease the size of the grain as the milling time is increased. It is also noted that the grains of composites (AlSi5Cu2/SiC are smaller than samples prepares without SiC addition. 40 hours of milling lead to formed very small grains of Al phase (20 nm in average in composite powder.

  9. Composition-dependent photoluminescence properties of CuInS{sub 2}/ZnS core/shell quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Hua, Jie [Key Laboratory of Functional Materials Physics and Chemistry of the Ministry of Education, Jilin Normal University, Siping 136000, Jilin (China); College of Information Technology, Jilin Normal University, Siping 136000, Jilin (China); Du, Yuwei; Wei, Qi [College of Information Technology, Jilin Normal University, Siping 136000, Jilin (China); Yuan, Xi; Wang, Jin [Key Laboratory of Functional Materials Physics and Chemistry of the Ministry of Education, Jilin Normal University, Siping 136000, Jilin (China); College of Information Technology, Jilin Normal University, Siping 136000, Jilin (China); Zhao, Jialong [Key Laboratory of Functional Materials Physics and Chemistry of the Ministry of Education, Jilin Normal University, Siping 136000, Jilin (China); Li, Haibo, E-mail: lihaibo@jlnu.edu.cn [Key Laboratory of Functional Materials Physics and Chemistry of the Ministry of Education, Jilin Normal University, Siping 136000, Jilin (China)

    2016-06-15

    CuInS{sub 2}/ZnS (CIS/ZnS) core/shell quantum dots (QDs) with various Cu/In ratios were synthesized using the hot-injection method, and their photoluminescence (PL) properties were investigated by measuring steady-state and time-resolved PL spectroscopy. The emission peak of the CIS/ZnS QDs were tuned from 680 to 580 nm by decreasing the Cu/In precursor ratio from 1/1 to 1/9. As the Cu/In ratio decreases, the PL lifetimes and PL quantum yields (QYs) of CIS/ZnS core/shell QDs increased firstly and then decreased. Two dominant radiative recombination processes were postulated to analyze composition-dependent PL properties, including the recombination from a quantized conduction band to deep defects state and donor-acceptor pair (DAP) recombination. The decrease of PL efficiency resulted from high density defects and traps, which formed at the interface between CIS core and ZnS shell due to the large off-stoichiometry composition. The PL intensity and peak energy for CIS/ZnS core/shell QDs as a function of temperature were also provided. The thermal quenching further confirmed that the PL emission of CIS/ZnS QDs did not come from the recombination of excitons but from the recombination of many kinds of intrinsic defects inside the QDs as emission centers.

  10. Impact of Precursor Compositions on the Structural and Photovoltaic Properties of Spray-Deposited Cu2 ZnSnS4 Thin Films.

    Science.gov (United States)

    Nguyen, Thi Hiep; Fujikawa, Shotaro; Harada, Takashi; Chantana, Jakapan; Minemoto, Takashi; Nakanishi, Shuji; Ikeda, Shigeru

    2016-09-08

    Pure sulfide Cu2 ZnSnS4 thin films were fabricated on Mo-coated glass substrates by facile spray deposition of aqueous precursor solutions containing Cu(NO3 )2 , Zn(NO3 )2 , Sn(CH3 SO3 )2 , and thiourea followed by annealing at 600 °C. When a precursor solution containing a stoichiometric composition of Cu, Zn, and Sn was used, the resulting Cu2 ZnSnS4 thin film contained a Cu2-x S impurity phase owing to the evaporation of Sn components during the annealing process. The Cu2-x S impurity in the Cu2 ZnSnS4 thin film was removed by reducing the concentration of Cu in the precursor solution. This resulted in an improvement of the structural features (i.e., grain sizes and compactness) as well as the electric properties such as acceptor densities, the nature of the acceptor defects, and carrier lifetimes. A solar cell based on the Cu2 ZnSnS4 film with an empirically optimal composition showed conversion efficiency of 8.1 %. The value achieved was one of the best efficiencies of Cu2 ZnSnS4 -based cells derived from a non-vacuum process. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Spectroscopic Fingerprint of Phase-Incoherent Superconductivity in the Underdoped Bi2Sr2CaCu2O8+δ

    Energy Technology Data Exchange (ETDEWEB)

    Lee, J.; Davis, J.; Fujita, K.; Schmidt, A.R.; Kim, C.K.; Eisaki, H.; Uchida, S.

    2009-08-28

    A possible explanation for the existence of the cuprate 'pseudogap' state is that it is a d-wave superconductor without quantum phase rigidity. Transport and thermodynamic studies provide compelling evidence that supports this proposal, but few spectroscopic explorations of it have been made. One spectroscopic signature of d-wave superconductivity is the particle-hole symmetric 'octet' of dispersive Bogoliubov quasiparticle interference modulations. Here we report on this octet's evolution from low temperatures to well into the underdoped pseudogap regime. No pronounced changes occur in the octet phenomenology at the superconductor's critical temperature T{sub c}, and it survives up to at least temperature T {approx} 1.5 T{sub c}. In this pseudogap regime, we observe the detailed phenomenology that was theoretically predicted for quasiparticle interference in a phase-incoherent d-wave superconductor. Thus, our results not only provide spectroscopic evidence to confirm and extend the transport and thermodynamics studies, but they also open the way for spectroscopic explorations of phase fluctuation rates, their effects on the Fermi arc, and the fundamental source of the phase fluctuations that suppress superconductivity in underdoped cuprates.

  12. On the role of precursor powder composition in controlling microstructure, flux pinning, and the critical current density of Ag/Bi2Sr2CaCu2Ox conductors

    Science.gov (United States)

    Li, Pei; Naderi, Golsa; Schwartz, Justin; Shen, Tengming

    2017-03-01

    Precursor powder composition is known to strongly affect the critical current density (J c) of Ag/Bi2Sr2CaCu2Ox (Bi-2212) wires. However, reasons for such J c dependence have not yet been fully understood, compromising our ability to achieve further optimization. We systematically examined superconducting properties, microstructural evolution and phase transformation, and grain boundaries of Bi-2212 conductors fabricated from precursor powders with a range of compositions using a combination of transport-current measurements, a quench technique to freeze microstructures at high temperatures during heat treatment, and scanning transmission electron microscopy (STEM). Samples include both dip-coated tapes and round wires, among which a commercial round wire carries a high J c of 7600 A mm-2 at 4.2 K, self-field and 2600 A mm-2 at 4.2 K, 20 T, respectively. In the melt, this high-J c conductor, made using a composition of Bi2.17Sr1.94Ca0.89Cu2Ox, contains a uniform dispersion of fine alkaline-earth cuprate (AEC) and copper-free solid phases, whereas several low-J c conductors contain large AEC particles. Such significant differences in the phase morphologies in the melt are accompanied by a drastic difference in the formation kinetics of Bi-2212 during recrystallization cooling. STEM studies show that Bi-2212 grain colonies in the high-J c conductors have a high density of Bi2Sr2CuO y (Bi-2201) intergrowths, whereas a low-J c conductor, made using Bi2.14Sr1.66Ca1.24Cu1.96O x , is nearly free of them. STEM investigation shows grain boundaries in low-J c conductors are often insulated with a Bi-rich amorphous phase. High-J c conductors also show higher flux-pinning strength, which we ascribe to their higher Bi-2201 intergrowth density.

  13. A novel solid digestate-derived biochar-Cu NP composite activating H2O2 system for simultaneous adsorption and degradation of tetracycline.

    Science.gov (United States)

    Fu, Dun; Chen, Zheng; Xia, Dong; Shen, Liang; Wang, Yuanpeng; Li, Qingbiao

    2017-02-01

    Solid digestate, a by-product of anaerobic digestion systems, has led to a range of environmental issues. In the present study, a novel composite based on a solid digestate-biochar-Cu NP composite was synthesized for tetracycline removal from an aqueous medium. The removal efficiency values for tetracycline (200 mg L(-1)) were 31.5% and 97.8%, respectively, by the biochar-Cu NP composite (0.5 g L(-1)) in the absence and presence of hydrogen peroxide (H2O2, 20 mM) within 6 h of reaction time. The possible degradation pathway of tetracycline was investigated using liquid chromatography-mass spectrometry. The desorption experiment results suggested that no significant concentration of tetracycline was detected on the composite after the reaction, but a small amount of intermediates in terms of total organic carbon (TOC) accounting for 3.1%, and 23.3% of the end-product NH4(+) was adsorbed onto the biochar sheets. The dispersive Cu NPs on the biochar resulted in an increase in the surface area and pore volume of the biochar-Cu NP composite, which enhanced tetracycline adsorption as well as the degradation efficiency. Relative tetracycline removal mechanisms were dominantly ascribed to ·OH generation from the Cu(II)/Cu(I) redox reaction with H2O2 and the electron-transfer process of free radicals (FRs) in biochar. The proposed approach serves dual purposes of waste digestate reuse and treatment of antibiotic pollutants. This study highlights the activation of H2O2 by the dispersive Cu NPs coupling with biochar derived from a waste solid digestate for tetracycline treatment. Copyright © 2016. Published by Elsevier Ltd.

  14. Low-temperature Sn-119-Moessbauer study of superconducting Bi4Sr(3.5)Ca(2.5)Cu4Sn(0.015)O(16-y) ceramic (2212 phase)

    Science.gov (United States)

    Nishida, Tetsuaki; Katada, Motomi; Miura, Norio; Deshimaru, Yuichi; Yamazoe, Noboru; Matsumoto, Yasukuni; Takashima, Yoshimasa

    1992-04-01

    The Sn-119-Moessbauer spectra of superconducting Bi4Sr(3.5)Ca(2.5)Cu4Sn(0.015)O(16-y) ceramic (2212 phase, Tc, 77 K), measured between 298 K and 7 K, consist of singlet peaks of Sn(4+) with the deltas and Gammas of -0.01-0.07 and 1.05-1.27 mm/s, respectively. The ln A (absorption area)-vs.-T plot shows that the recoil-free fraction f increases with decreasing temperature, and that the Debye and Einstein temperatures are 340 and 185 K, respectively. The Theta(D) of 340 K suggests that the Sn(4+) is in the BiO5 pyramids. The ln A shows a 'normal' lattice vibration, probably because of the long Cu-O(3) distance and the displacement of O(3).

  15. Electrostatic-assembly three-dimensional CNTs/rGO implanted Cu2O composite spheres and its photocatalytic properties

    Science.gov (United States)

    Zeng, Bin; Chen, Xiaohua; Ning, Xutao; Chen, Chuansheng; Deng, Weina; Huang, Qun; Zhong, Wenbin

    2013-07-01

    Carbon nanotubes/reduced graphene oxides (CNTs/rGO) implanting cuprous oxide (Cu2O) composite spheres have been successfully prepared via an electrostatic self-assemble with microwave-assisted. Scanning electron microscopy and transmission electron microscopy observations confirmed that the hybrid of CNTs and rGO was implanted into Cu2O matrix and formed a three-dimensional embedded micrometer sphere structure. The possible formation mechanism of this architecture was also proposed. The photocatalytic properties were further investigated by evaluating on photo-degradation of a pollutant methyl orange (MO). The experimental results indicated that this novel architecture enhanced photocatalytic performance with 99.8% decomposition of MO after 40 min in the presence of H2O2 under visible light irradiation, which was much higher than that of pure Cu2O powders (67.9%). This study provides a convenient method for assembling various CNTs/rGO-semiconductor composites in the future applications of water purification as well as optoelectronic fields at a large scale.

  16. Novel-structured electrospun TiO2/CuO composite nanofibers for high efficient photocatalytic cogeneration of clean water and energy from dye wastewater.

    Science.gov (United States)

    Lee, Siew Siang; Bai, Hongwei; Liu, Zhaoyang; Sun, Darren Delai

    2013-08-01

    It is still a challenge to photocatalytically cogenerate clean water and energy from dye wastewater owing to the relatively low photocatalytic efficiency of photocatalysts. In this study, novel-structured TiO2/CuO composite nanofibers were successfully fabricated via facile electrospinning. For the first time, the TiO2/CuO composite nanofibers demonstrated multifunctional ability for concurrent photocatalytic organic degradation and H2 generation from dye wastewater. The enhanced photocatalytic activity of TiO2/CuO composite nanofibers was ascribed to its excellent synergy of physicochemical properties: 1) mesoporosity and large specific surface area for efficient substrate adsorption, mass transfer and light harvesting; 2) red-shift of the absorbance spectra for enhanced light utilization; 3) long nanofibrous structure for efficient charge transfer and ease of recovery, 4) TiO2/CuO heterojunctions which enhance the separation of electrons and holes and 5) presence of CuO which serve as co-catalyst for the H2 production. The TiO2/CuO composite nanofibers also exhibited rapid settleability by gravity and uncompromised reusability. Thus, the as-synthesized TiO2/CuO composite nanofibers represent a promising candidate for highly efficient concurrent photocatalytic organic degradation and clean energy production from dye wastewater. Copyright © 2013 Elsevier Ltd. All rights reserved.

  17. Preparation and characterization of electroless Ni–B/nano-SiO2, Al2O3, TiO2 and CuO composite coatings

    Indian Academy of Sciences (India)

    Dursun Ekmekci̇; Ferhat Bülbül

    2015-06-01

    Ni–B/SiO2, Al2O3, TiO2 and CuO composite coatings were successfully obtained by the electroless plating technique. Dispersible SiO2, Al2O3, TiO2 and CuO nanoparticles were co-deposited with electroless Ni–B coating onto AISI-304 steel substrates. Deposits were characterized for its structural properties by X-ray diffraction (XRD). XRD results showed a broad peak of Ni–B and low intensity composite nanoparticle peaks. The surface and cross-section morphology of samples were analysed using a scanning electron microscope (SEM). Surface analysis showed that the incorporation in Ni–B matrix of nano-SiO2, Al2O3, TiO2 and CuO particles increases the nodularity of composite coatings. The deposits are composed of a columnar structure grown along the vertical direction of the substrate surface. The results also show that electroless nanocomposite coatings tend to have greater microhardness compared with the coating without nanoparticles. The increase in the microhardness of the nanocomposite coatings reported in this study is attributed to an effect of dispersion strengthening of ceramic particles in the Ni–B matrix.

  18. Preparation and characterization of Ag-added Bi1.84Pb0.4Sr2Ca2.2Cu3O10+ bulk tube conductors for cryogen free superconducting magnet

    Indian Academy of Sciences (India)

    S N Ekbote; G K Padam; M Sharma; N K Arora; B S Khurana; R C Goel; D K Suri; N Mehra; B K Das

    2001-12-01

    Bulk tube conductors of Bi1.84Pb0.4Sr2Ca2.2Cu3O10+ with addition of silver varying from 0 to 25 wt% (not reported earlier) were systematically studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), electrical transport and a.c. susceptibility techniques. The tube conductors formed by cold isostatic pressing (CIP) of the powders obtained from spray drying method have been made successfully. It was found that Ag addition has not only affected the formation of the desired Bi-2223 phase and the microstructure of these large bulk tube samples thereby influencing on the critical current (c), it also reduces the contact resistance to minimize the cryogen losses. These variations have been found to be Ag content dependent. An optimized value of 10 wt% Ag has been found to produce the best quality tubes showing reproducible c value > 120 Amp at 77 K which is in general a requirement to energies of the cryogen free conventional/HTSC superconducting magnets below 20 K.

  19. Composite ceramic superconducting wires for electric motor applications

    Science.gov (United States)

    Halloran, John W.

    1990-07-01

    Several types of HTSC wire have been produced and two types of HTSC motors are being built. Hundreds of meters of Ag- clad wire were fabricated from YBa2Cu3O(7-x) (Y-123) and Bi2Ca2Sr2Cu3O10 (BiSCCO). The dc homopolar motor coils are not yet completed, but multiple turns of wire have been wound on the coil bobbins to characterize the superconducting properties of coiled wire. Multifilamentary conductors were fabricated as cables and coils. The sintered polycrystalline wire has self-field critical current densities (Jc) as high as 2800 A/sq cm, but the Jc falls rapidly with magnetic field. To improve Jc, sintered YBCO wire is melt textured with a continuous process which has produced textures wire up to 0.5 meters long with 77K transport Jc above 11, 770 A/sq cm2 in self field and 2100 A/sq cm2 at 1 telsa. The Emerson Electric dc homopolar HTSC motor has been fabricated and run with conventional copper coils. A novel class of potential very powerful superconducting motors have been designed to use trapped flux in melt textures Y-123 as magnet replicas in an new type of permanent magnet motor. The stator element and part of the rotor of the first prototype machine exist, and the HTSC magnet replica segments are being fabricated.

  20. Depression of superconducting transition temperature due to Pr in the (La 2.5- xPr xNd 0.5)CaBa 3Cu 7O z system

    Science.gov (United States)

    Kundaliya, Darshan C.; Vij, Reeta; Kulkarni, R. G.; Yelon, W. B.; Malik, S. K.

    2002-03-01

    Structural and superconducting properties of (La2.5-xPrxNd0.5)CaBa3Cu7Oz (0⩽x⩽0.7) compounds have been investigated. Neutron diffraction studies reveal that these crystallize in the triple-perovskite structure (space group P4/mmm) with an oxygen content of 16.6 per formula unit nearly independent of the Pr content. The superconducting transition temperature, Tc, of x=0 compound is ∼79 K and decreases almost linearly with increasing x to ∼42 K for x=0.7. In order to see if the depression of Tc due to Pr can be compensated by Ca, we examined the compounds (La2.5-x-yPrxCayNd0.5)CaBa3Cu7Oz with x=0.7 and y=0 and 0.4. The observed Tc in these compound is almost independent of Ca content suggesting the absence of a contribution from hole filling in the depression of Tc by Pr. The observed depression of Tc with increasing Pr content in the title compound is analyzed on the basis of magnetic pair breaking by the Pr-4f electrons.

  1. Composition and structure of CuInSe2 thin films prepared by vacuum evaporation of the constituent elements

    Science.gov (United States)

    Dhere, N. G.; Lourenco, M. C.; Dhere, R. G.; Kazmerski, L. L.

    1984-11-01

    The characteristics of CuInSe2 thin film solar cells produced by a three-source deposition method were investigated. The films were deposited at 350 C, followed by 30 min annealing at the same temperature. The compositions of the cells and intracell fractional variations were dependent on the proximity to the film source during formation. A chalcopyrite CuInSe2 structure was observed in X-ray diffraction patterns and high energy electron diffraction studies of the films on NaCl single crystal substrates. Grain sizes ranged from 0.2-0.6 micron, and the films had a band gap in the 1.02-1.04 eV interval.

  2. Surface-Mechanical Properties of Electrodeposited Cu-Al2O3 Composite Coating and Effects of Processing Parameters

    Science.gov (United States)

    Maharana, H. S.; Ashok, Akarapu; Pal, S.; Basu, A.

    2016-01-01

    Cu/Al2O3 composite coatings were prepared from acidic copper sulfate bath containing ultrafine Al2O3 particles by direct current plating method to increase the surface-mechanical property of Cu for its possible use as electrical contact. Effect of ultrafine Al2O3 particle concentration in electrolyte and deposition current density on the surface-mechanical properties of the coatings was investigated. Coatings were characterized by scanning electron microscopy and X-ray diffraction (XRD) techniques for the purpose of surface morphology and phase study. From XRD data, crystallographic texture of the coating was also analyzed. To study the mechanical properties, microhardness testing, adhesion, and wear test were carried out. Improved hardness of the resultant coatings was observed and was correlated with the wt pct of ultrafine particle in the Cu matrix, matrix structure, and crystallographic orientation. Better wear property of the composite coating was also reported from the wear plot and wear track morphology. Altogether, better coating property was attributed toward finer matrix, hard reinforced phase, and preferred orientation in selected conditions. Electrical conductivity of the coating was affected by grain size and second-phase concentration, and the values obtained were in the usable range required for electrical applications.

  3. Microstructures and mechanical properties of Cu/Ti{sub 3}SiC{sub 2}/C/MWCNTs composites prepared by vacuum hot-pressing sintering

    Energy Technology Data Exchange (ETDEWEB)

    Xiaosong, Jiang, E-mail: xsjiang@yeah.net [School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu, Sichuan 610031 (China); Liu, Wanxia; Li, Jingrui [School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu, Sichuan 610031 (China); Shao, Zhenyi [Department of Mechanical Engineering, Chengdu Technological University, Chengdu, Sichuan 610031 (China); Zhu, Degui [School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu, Sichuan 610031 (China)

    2015-01-05

    Highlights: • Cu/Ti{sub 3}SiC{sub 2}/C/MWCNTs composites were prepared using vacuum hot-pressing sintering. • Dispersions of MWCNTs were prepared using 10 μg/ml gallic acid aqueous solution. • MWCNTs content has no effect on generation of TiC and Cu{sub 9}Si to effect matrix’s performance. - Abstract: Cu/Ti{sub 3}SiC{sub 2}/C/MWCNTs composites were prepared by vacuum hot-pressing sintering. Microstructures and mechanical properties of Cu/Ti{sub 3}SiC{sub 2}/C/MWCNTs composites with different multi-walled carbon nanotubes contents have been systematically investigated. The microstructures of the composites were examined by optical microscopy, X-ray diffraction, back scattered electron imaging, scanning electron microscope and energy dispersive spectrometer. The mechanical properties were determined from Brinell hardness and tensile tests. The results demonstrated that there was an optimum value of MWCNTs content which has an impact on microstructures and mechanical properties of Cu/Ti{sub 3}SiC{sub 2}/C/MWCNTs composites. Based on MWCNTs content on properties and microstructure of Cu/Ti{sub 3}SiC{sub 2}/C/MWCNTs composites, effects of MWCNTs on improvement of the composites and strengthening mechanism have been analyzed.

  4. 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)

  5. Preparation and characterization of superconducting MgB{sub 2} rods

    Energy Technology Data Exchange (ETDEWEB)

    Orlinska, N. [Institute of Materials Science, University of Silesia, Katowice (Poland); Zaleski, A. [Institute of Low Temperature and Structure Research, Wroclaw (Poland); Paszula, J.M. [Faculty of Armament and Aviation Technology, Military University of Technology, Warsaw (Poland); Wokulski, Z.

    2007-12-15

    Superconducting Cu/Fe/MgB{sub 2} and Steel/Cu/MgB{sub 2} rods were prepared through the ex-situ modified PIT technique with explosive consolidation method. The phase composition, microstructural features were investigated by X-ray diffraction and scanning electron microscope. The AC susceptibility for a core samples was measured by the AC susceptometry. Measurements of the magnetization hysteresis loops were also carried out. It is found that no impurity phase was formed in MgB{sub 2} rods. In addition, it was found that grains in both Cu/Fe/MgB{sub 2} and Steel/Cu/MgB{sub 2} rods are densely packed. The magnetic measurements show that the critical temperature of Cu/Fe/MgB{sub 2} and Steel/Cu/MgB{sub 2} rods is 37.7 K and 37.6 K, respectively. The high critical current density of 9.22 x 10{sup 5} A/cm{sup 2} (4.1 K, 0.2 T) was obtained for Steel/Cu/MgB{sub 2} rod. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  6. Characterization of the insulator barrier and the superconducting transition temperature in GdBa{sub 2}Cu{sub 3}O{sub 7−δ}/BaTiO{sub 3} bilayers for application in tunnel junctions

    Energy Technology Data Exchange (ETDEWEB)

    Navarro, H., E-mail: henrynavarro@cab.cnea.gov.ar; Sirena, M.; Haberkorn, N. [Instituto Balseiro, Universidad Nacional de Cuyo and CNEA, 8400 Bariloche (Argentina); Centro Atómico Bariloche, Comisión Nacional de Energía Atómica. Av. Bustillo 9500, 8400 San Carlos de Bariloche (Argentina); Yang, Ilkyu [Department of Physics, Pohang University of Science and Technology, Pohang (Korea, Republic of); Kim, Jeehoon [Department of Physics, Pohang University of Science and Technology, Pohang (Korea, Republic of); CALDES, Institute for Basic Science, Pohang (Korea, Republic of)

    2015-07-28

    The optimization of the superconducting properties in a bottom electrode and the quality of an insulator barrier are the first steps in the development of superconductor/insulator/superconductor tunnel junctions. Here, we study the quality of a BaTiO{sub 3} tunnel barrier deposited on a 16 nm thick GdBa{sub 2}Cu{sub 3}O{sub 7−δ} thin film by using conductive atomic force microscopy. We find that the tunnel current is systematically reduced (for equal applied voltage) by increasing the BaTiO{sub 3} barrier thickness between 1.6 and 4 nm. The BaTiO{sub 3} layers present an energy barrier of ≈1.2 eV and an attenuation length of 0.35–0.5 nm (depending on the applied voltage). The GdBa{sub 2}Cu{sub 3}O{sub 7−δ} electrode is totally covered by a BaTiO{sub 3} thickness above 3 nm. The presence of ferroelectricity was verified by piezoresponse force microscopy for a 4 nm thick BaTiO{sub 3} top layer. The superconducting transition temperature of the bilayers is systematically suppressed by increasing the BaTiO{sub 3} thickness. This fact can be associated with stress at the interface and a reduction of the orthorhombicity of the GdBa{sub 2}Cu{sub 3}O{sub 7−δ}. The reduction in the orthorhombicity is expected by considering the interface mismatch and it can also be affected by reduced oxygen stoichiometry (poor oxygen diffusion across the BaTiO{sub 3} barrier)

  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. Highly coercive cobalt ferrite nanoparticles-CuTl-1223 superconductor composites

    Energy Technology Data Exchange (ETDEWEB)

    Jabbar, Abdul; Qasim, Irfan; Khan, Shahid A.; Nadeem, K.; Waqee-ur-Rehman, M.; Mumtaz, M., E-mail: mmumtaz75@yahoo.com; Zeb, F.

    2015-03-01

    We explored the effects of highly coercive cobalt ferrite (CoFe{sub 2}O{sub 4}) nanoparticles addition on structural, morphological, and superconducting properties of Cu{sub 0.5}Tl{sub 0.5}Ba{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10-δ} (CuTl-1223) matrix. Series of (CoFe{sub 2}O{sub 4}){sub x}/CuTl-1223 (x=0 ∼2.0 wt%) composites samples were synthesized and were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) absorption spectroscopy, and dc-resistivity versus temperature measurements. The magnetic behavior of CoFe{sub 2}O{sub 4} nanoparticles was determined by MH-loops with the help of superconducting quantum interference device (SQUID). MH-loops analysis showed that these nanoparticles exhibit high saturation magnetization (86 emu/g) and high coercivity (3350 Oe) at 50 K. The tetragonal structure of host CuTl-1223 superconducting matrix was not altered after the addition of CoFe{sub 2}O{sub 4} nanoparticles, which gave us a clue that these nanoparticles had occupied the inter-granular sites (grain-boundaries) and had filled the pores. The increase of mass density with increasing content of these nanoparticles in composites can also be an evidence of filling up the voids in the matrix. The resistivity versus temperature measurements showed an increase in zero resistivity critical {T_c(0)}, which could be most probably due to improvement of weak-links by the addition of these nanoparticles. But the addition of these nanoparticles beyond an optimum level caused the agglomeration and produced additional stresses in material and suppressed the superconductivity. - Highlights: • T{sub c}(0) increased with increasing CoFe{sub 2}O{sub 4} nanoparticles up to x=1.5. • CoFe{sub 2}O{sub 4} nanoparticles addition has not affected the structure of CuTl-1223. • Addition of CoFe{sub 2}O{sub 4} nanoparticles has improved inter-grains weak links. • Non-monotonic variation of ρ{sub (300} {sub K)} (Ω-cm) is due to

  10. Critical currents of superconducting BiPbSrCaCuO tapes in the magnetic flux density range 0--19. 75 T at 4. 2, 15, and 20 K

    Energy Technology Data Exchange (ETDEWEB)

    Sato, K.; Hikata, T. (Osaka Research Laboratories, Sumitomo Electric Industries, Osaka (Japan)); Iwasa, Y. (Francis Bitter National Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, MA (USA))

    1990-10-29

    Critical currents of superconducting silver-sheathed tapes of Bi{sub 1.8}Pb{sub 0.4}Sr{sub 2}Ca{sub 2.2}Cu{sub 3}O{sub {ital x}} have been measured in the magnetic flux density range 0--19.75 T at 4.2, 15, and 20 K. One tape achieved a critical current of 60.6 A at 19.75 T and 20 K; the corresponding critical current density is 551 A/mm{sup 2}. In the same field, the tape has critical currents of 72.3 A (657 A/mm{sup 2}) at 15 K and 94.2 A (856 A/mm{sup 2}) at 4.2 K. At 77 K and in zero field, the tape carries 32.9 A (299 A/mm{sup 2}). These results indicate that high {ital T}{sub {ital c}}'' superconducting magnets of engineering interest may soon be feasible.

  11. 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...

  12. Novel Preparation of Nano-Composite CuO-Cr2O3 Using Ctab-Template Method and Efficient for Hydrogenation of Biomass-Derived Furfural

    Science.gov (United States)

    Yan, Kai; Wu, Xu; An, Xia; Xie, Xianmei

    2013-02-01

    A simple route to fabricate nano-composite oxides CuO-Cr2O3 using hexadecyltrimethylammonium bromide (CTAB)-templated Cu-Cr hydrotalcite as the precursor is presented. This novel method is based on CTAB-templating effect for mesostructure directing and using the cheap metal nitrate, followed by removal of CTAB. It was indicated that the nano-composite CuO-Cr2O3 was formed during the removal of CTAB. X-ray diffraction (XRD) and transitional electronic microscopy (TEM) revealed nice nano-composite oxides CuO-Cr2O3 were formed with high crystallinity. N2 adsorption and desorption indicated that a high surface area of 170.5 m2/g with a pore size of 2.7 nm of the nano-composite CuO-Cr2O3 was facilely resulted. The as-synthesized nano-composite oxides CuO-Cr2O3 display good catalytic activities for hydrogenation of furfural to furfuryl alcohol, whereas 86% selectivity was achieved at 75% conversion of furfural.

  13. Discrepancy between integral and local composition in off-stoichiometric Cu2ZnSnSe4 kesterites: A pitfall for classification

    Science.gov (United States)

    Schöppe, Philipp; Gurieva, Galina; Giraldo, Sergio; Martínez-Criado, Gema; Ronning, Carsten; Saucedo, Edgardo; Schorr, Susan; Schnohr, Claudia S.

    2017-01-01

    High-efficiency kesterite-based thin film solar cells typically feature Cu-poor, Zn-rich absorbers although secondary phases occur easily in non-stoichiometric Cu2ZnSnSe4. We therefore applied high-resolution X-ray fluorescence analysis using a synchrotron nanobeam to study the local composition of a CZTSe cross section lamella cut from a sample with an integral composition of Zn/Sn = 1.37 and Cu/(Zn+Sn) = 0.55. We find submicrometer-sized ZnSe-, SnSe/SnSe2-, and even CuSe/Cu2Se-like secondary phases, while the local compositions of the kesterite are highly Zn-rich yet barely Cu-poor with 1.5 ≤ Zn/Sn ≤ 2.2 and Cu/(Zn+Sn) ˜ 1.0. Consequently, great care must be taken when relating the integral composition to other material properties including the device performance.

  14. The effect of multilayered Bi1.8Pb0.4Ca2.2Sr2Cu3Ox/Ag on superconducting and microstructure properties of Bi1.8Pb0.4Ca2.2Sr2Cu3Ox

    Science.gov (United States)

    Akdogan, Mustafa; Terzioglu, Cabir; Belenli, Ibrahim

    2010-03-01

    A precursor powder with a nominal chemical composition of Bi1.8Pb0.4Ca2.2Sr2Cu3Ox was used to fabricate the multilayered Bi1.8Pb0.4Ca2.2Sr2Cu3Ox/Ag samples (number of layers was 2, 4 and 8) using the powder-in-tube method (PIT). The density of powder increases during the drawing procedure and inside the composite wires of the final diameter is 3.54 mm. By an intermediate rolling, pressing and annealing procedure, the wires were rolled to obtain tapes. The rolling process was not effective in obtaining further substantially increase of the powder density, but greatly improved the orientation of ceramic grains inside the silver sheath. The sample is composed of a highly oriented Bi-2223 phase in the region near to the Ag layer. The eight-layered sample exhibits a rather high Ic value of 110 A. Tc and Jc are enhanced by increasing the number of Ag layers. The formation of the dense oriented structure is near the interface between oxide and the Ag layer. This suggests that Ag plays an important role in the improvement of Jc.

  15. Catalytic evaluation on liquid phase oxidation of vanillyl alcohol using air and H2O2 over mesoporous Cu-Ti composite oxide

    Science.gov (United States)

    Saha, Subrata; Hamid, Sharifah Bee Abd; Ali, Tammar Hussein

    2017-02-01

    A mesoporous, highly crystalline Cu-Ti composite oxide catalyst was prepared via facile, simple and modified solution method varying Cu and Ti ratio for selective liquid phase oxidation of vanillyl alcohol. Various spectroscopic procedures were employed to systematically characterize the catalyst structural and physicochemical properties. The defect chemistry of the catalyst was confirmed from the presence of surface defects revealed through HRTEM imagery between the TiO2 (101) and Cu3TiO4 (012) planes, complemented by the XRD profiling. Further, presence of oxygen vacancy evidenced by O 1s XPS spectra were observed on the catalyst surface. Moreover, the stoichiometry of Cu and Ti in the catalyst synthesis protocol was notably found to be the vital determinant to alter the redox properties of Cu-Ti composite oxide catalyst supported by H2-TPR. O2-TPD analysis. Moreover, a rational investigation was done using different oxidants such as air and H2O2 with variables reaction conditions. The catalyst was active for liquid phase oxidation of vanillyl alcohol to vanillin with performance of 66% conversion and 71% selectivity using H2O2 in base free condition. And also, catalytic activity was significantly improved by 94% conversion with 86% selectivity to vanillin in liquid phase aerobic oxidation at the optimum reaction conditions. To expand the superiority of the catalyst, three times reusability study was also examined with appreciable catalytic activity.

  16. The influence of growth parameters on the structure and composition of CuGaS{sub 2} epilayers grown by MOVPE

    Energy Technology Data Exchange (ETDEWEB)

    Branch, M.S. [Physics Department, Nelson Mandela Metropolitan University, Port Elizabeth 6031 (South Africa)]. E-mail: Matthew.Branch@nmmu.ac.za; Berndt, P.R. [Physics Department, Nelson Mandela Metropolitan University, Port Elizabeth 6031 (South Africa); Leitch, A.W.R. [Physics Department, Nelson Mandela Metropolitan University, Port Elizabeth 6031 (South Africa); Botha, J.R. [Physics Department, Nelson Mandela Metropolitan University, Port Elizabeth 6031 (South Africa); Weber, J. [Institute for Low Temperature Physics, University of Technology, D-01062 Dresden (Germany)

    2006-04-01

    The influence of various growth parameters on the composition and structure of MOVPE-grown CuGaS{sub 2} is presented. The Cu content of the grown layers is shown to decrease in the direction of the carrier gas flow, whilst the Ga and S content are shown to increase. Changing the flow of Cu(hfac){sub 2}.Et{sub 3}N to vary the I/III ratio in the vapour phase has a greater effect on the composition of grown epilayers than changing the flow of TEGa. This is indicative of Cu being the minority species present at the growth interface. A larger rate of decrease in the Cu content with an increase in both TEGa and DtBS flows suggests pre-reactions between Cu(hfac){sub 2}.Et{sub 3}N and both TEGa and DtBS precursors. Lower substrate temperatures are suggested to be thermodynamically unfavourable for the growth of CuGaS{sub 2}, yet enhance the formation of Ga{sub x}S{sub y} phases. The surface morphology of Cu-rich layers are typically inferior with a high density of crystallites, whilst Cu-poor epilayers are characteristically smooth with a single XRD reflection attributed to the (004) plane of c-axis-orientated epitaxial material.

  17. Dopant rearrangement and superconductivity in Bi{sub 2}Sr{sub 2-x}La{sub x}CuO{sub 6} thin films under annealing

    Energy Technology Data Exchange (ETDEWEB)

    Cancellieri, C [EPFL, Institute of Physics of Complex Matter, LPRX, Lausanne (Switzerland); Lin, P H [EPFL, Institute of Physics of Complex Matter, LPRX, Lausanne (Switzerland); Ariosa, D [EPFL, Institute of Physics of Complex Matter, LPRX, Lausanne (Switzerland); Pavuna, D [EPFL, Institute of Physics of Complex Matter, LPRX, Lausanne (Switzerland)

    2007-06-20

    By combining x-ray diffraction (XRD), x-ray photoemission spectroscopy (XPS) and AC susceptibility measurements we investigate the evolution of structural and superconducting properties of La-doped Bi-2201 thin films grown by pulsed laser deposition (PLD) under different annealing conditions. We find that the main effect of oxygen annealing is to improve the crystal coherence by enabling La cation migration to the Sr sites. This activates the desired hole doping. Short-time Ar annealing removes the interstitial oxygen between the BiO layers, fine adjusting the effective hole doping. The superconducting critical temperature is consequently enhanced. However, longer annealings result in phase separation and segregation of the homologous compound Bi-1201. We attribute this effect to the loss of Bi during the annealing.

  18. 含B2-CuZr相CuZr基块体金属玻璃复合材料应变速率敏感性的变化%Strain Rate Sensitivity Variation in CuZr-based Bulk Metallic Glass Composites Containing B2-CuZr Phase

    Institute of Scientific and Technical Information of China (English)

    魏然; 昌云; 杨森; 张长军; 贺林

    2016-01-01

    通过应变速率跳跃模式下的单轴压缩试验,研究了含有不同体积分数B2-CuZr相的CuZr基块体金属玻璃复合材料的应变速率敏感性.结果发现,随着B2-CuZr相体积分数的增加,在3.7×10-5s-1至3.7×10-3 s-1的应变速率范围中,该复合材料的应变速率敏感指数可由负值变化为正值.但是,对于B2-CuZr相体积分数高达约80%的复合材料,其应变速率敏感指数的正值仍然是反常的低.这一现象与B2-CuZr相自身力学行为所呈现的有限应变速率依赖性有关,是由于变形过程中B2-CuZr相的马氏体相变效应所致.研究结果显示,CuZr基块体金属玻璃复合材料的极限应变速率敏感性受制于B2-CuZr相.%The strain rate sensitivity (SRS) of CuZr-based bulk metallic glass composites (BMGCs) containing a B2-CuZr phase with different volume fractions was investigated by performing uniaxial compression tests in a strain-rate-jump mode.It is found that the SRS exponents of the BMGCs can vary from negative to positive in the strain-rate range from 3.7× 10-5 s-1 to 3.7× 103 s-1 with increasing of the B2-CuZr phase volume fraction.However,the positive SRS exponent of the BMGC with a higher B2-CuZr phase volume fraction up to about 80% is still unexpectedly low.This is attributed to the limited strain-rate-dependence of mechanical behavior of the B2-CuZr phase,which is induced by the martensitic transformation effect of the phase during deformation.It is obvious that the SRS ceiling of the CuZr-based BMGCs is controlled by the B2-CuZr phase.

  19. Al2O3/Al2O3 Joint Brazed with Al2O3-particulate-contained Composite Ag-Cu-Ti Filler Material

    Institute of Scientific and Technical Information of China (English)

    Jianguo YANG; Hongyuan FANG; Xin WAN

    2005-01-01

    Microstructure and interfacial reactions of Al2O3 joints brazed with Al2O3-particulate-contained composite Ag-Cu-Ti filler material were researched by scanning electron microscopy (SEM), electron probe microscopy analysis (EPMA),energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The interfacial reaction layer thickness of joints brazed with conventional active filler metal and active composite filler materials with different volume fraction of Al2O3 particulate was also studied. The experimental results indicated although there were Al2O3 particulates added into active filler metals, the time dependence of interfacial layer growth of joints brazed with active composite filler material is t1/2 as described by Fickian law as the joints brazed with conventional active filler metal.

  20. Effects of critical fluctuations and dimensionality on the jump in specific heat at the superconducting transition temperature: Application to YBa2Cu3O7 -δ ,Bi2Sr2CaCu2O8 +δ , and KOs2O6 compounds

    Science.gov (United States)

    Keumo Tsiaze, R. M.; Wirngo, A. V.; Mkam Tchouobiap, S. E.; Fotue, A. J.; Baloïtcha, E.; Hounkonnou, M. N.

    2016-06-01

    We report on a study of the superconducting order parameter thermodynamic fluctuations in YBa2Cu3O7 -δ ,Bi2Sr2CaCu2O8 +δ , and KOs2O6 compounds. A nonperturbative technique within the framework of the renormalized Gaussian approach is proposed. The essential features are reported (analytically and numerically) through Ginzburg-Landau (GL) model-based calculations which take into account both the dimension and the microscopic parameters of the system. By presenting a self-consistent approach improvement on the GL theory, a technique for obtaining corrections to the asymptotic critical behavior in terms of nonuniversal parameters is developed. Therefore, corrections to the specific heat and the critical transition temperature for one-, two-, and three-dimensional samples are found taking into account the fact that fluctuations occur at all length scales as the critical point of a system is approached. The GL model in the free-field approximation and the 3D-X Y model are suitable for describing the weak and strong fluctuation regimes respectively. However, with a modified quadratic coefficient, the renormalized GL model is able to explain certain experimental observations including the specific heat of complicated systems, such as the cup-rate superconductors and the β -pyrochlore oxides. It is clearly shown that the enhancement, suppression, or rounding of the specific heat jump of high-Tc cup-rate superconductors at the transition are indicative of the order parameter thermodynamic fluctuations according to the dimension and the nature of interactions.

  1. Effects of critical fluctuations and dimensionality on the jump in specific heat at the superconducting transition temperature: Application to YBa_{2}Cu_{3}O_{7-δ},Bi_{2}Sr_{2}CaCu_{2}O_{8+δ}, and KOs_{2}O_{6} compounds.

    Science.gov (United States)

    Keumo Tsiaze, R M; Wirngo, A V; Mkam Tchouobiap, S E; Fotue, A J; Baloïtcha, E; Hounkonnou, M N

    2016-06-01

    We report on a study of the superconducting order parameter thermodynamic fluctuations in YBa_{2}Cu_{3}O_{7-δ},Bi_{2}Sr_{2}CaCu_{2}O_{8+δ}, and KOs_{2}O_{6} compounds. A nonperturbative technique within the framework of the renormalized Gaussian approach is proposed. The essential features are reported (analytically and numerically) through Ginzburg-Landau (GL) model-based calculations which take into account both the dimension and the microscopic parameters of the system. By presenting a self-consistent approach improvement on the GL theory, a technique for obtaining corrections to the asymptotic critical behavior in terms of nonuniversal parameters is developed. Therefore, corrections to the specific heat and the critical transition temperature for one-, two-, and three-dimensional samples are found taking into account the fact that fluctuations occur at all length scales as the critical point of a system is approached. The GL model in the free-field approximation and the 3D-XY model are suitable for describing the weak and strong fluctuation regimes respectively. However, with a modified quadratic coefficient, the renormalized GL model is able to explain certain experimental observations including the specific heat of complicated systems, such as the cup-rate superconductors and the β-pyrochlore oxides. It is clearly shown that the enhancement, suppression, or rounding of the specific heat jump of high-T_{c} cup-rate superconductors at the transition are indicative of the order parameter thermodynamic fluctuations according to the dimension and the nature of interactions.

  2. Optimization of TiO2/Cu/TiO2 multilayers as a transparent composite electrode deposited by electron-beam evaporation at room temperature

    Institute of Scientific and Technical Information of China (English)

    孙洪涛; 王小平; 寇志起; 王丽军; 王金烨; 孙义清

    2015-01-01

    Highly transparent indium-free composite electrodes of TiO2/Cu/TiO2 are deposited by electron-beam evaporation at room temperature. The effects of Cu thickness and annealing temperature on the electrical and optical properties of the multilayer film are investigated. The critical thickness of Cu mid-layer to form a continuous conducting layer is found to be 11 nm. The multilayer with a mid-Cu thickness of 11 nm is optimized to obtain a resistivity of 7.4×10−5 Ω·cm and an average optical transmittance of 86%in the visible spectral range. The figure of merit of the TiO2/Cu(11 nm)/TiO2 multilayer annealed at 150 ◦C reaches a minimum resistivity of 5.9×10−5 Ω·cm and an average optical transmittance of 88%in the visible spectral range. The experimental results indicate that TiO2/Cu/TiO2 multilayers can be used as a transparent electrode for solar cell and other display applications.

  3. 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.

  4. Anisotropic magnetoresistance in the normal state of oxygen-deficient YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} thin films induced by superconducting fluctuations

    Energy Technology Data Exchange (ETDEWEB)

    Lang, W. [Ludwig-Boltzmann-Institut fuer Festkoerperphysik, Vienna (Austria); Goeb, W. [Ludwig-Boltzmann-Institut fuer Festkoerperphysik, Vienna (Austria); Kula, W. [Rochester Univ., NY (United States). Dept. of Electrical Engineering; Sobolewski, R. [Rochester Univ., NY (United States). Dept. of Electrical Engineering

    1995-10-01

    We have investigated both the transverse and the longitudinal magnetoresistance of oxygen-deficient YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} thin films above their critical temperature T{sub c} = 55 K. The magnetoresistance is solely caused by the magnetic-field suppression of superconducting order-parameter fluctuations, existing in the films up to 143 K, i.e. 2.6 T{sub c}. The fluctuation effect provides a reliable determination of the Ginzburg-Landau coherence lengths, {xi}{sub ab} = 2.5 nm and {xi}{sub c} = 0.09 nm, with the anisotropy enhanced by oxygen depletion. No signature of the Maki-Thompson fluctuation process or a magnetoresistance resulting from the cyclotron motion of the normal-state quasiparticles was found. (orig.)

  5. CNTs Modified and Enhanced Cu Matrix Composites

    Directory of Open Access Journals (Sweden)

    ZHANG Wen-zhong

    2016-12-01

    Full Text Available The composite powders of 2%-CNTs were prepared by wet ball milling and hydrogen annealing treatment-cold pressing sintering was used to consolidate the ball milled composite powders with different modifications of the CNTs. The results show that the length of the CNTs is shortened, ports are open, and amorphous carbon content is increased by ball milling. And after a mixed acid purification, the impurity on the surface of the CNTs is completely removed,and a large number of oxygen-containing reactive groups are introduced; the most of CNTs can be embedded in the Cu matrix and the CNTs have a close bonding with the Cu matrix, forming the lamellar composite structure, then, ultrafine-grained composite powders can be obtained by hydrogen annealing treatment. Shortening and purification of the CNTs are both good for dispersion and bonding of CNTs in the Cu matrix, and the tensile strength and hardness of the composites after shortening and purification reaches the highest, and is 296MPa and 139.8HV respectively, compared to the matrix, up to 123.6% in tensile strength and 42.9% in hardness, attributed to the fine grain strengthening and load transferring.

  6. The effect of r f sputtering conditions on the morphological and superconducting properties in thin films of YBa{sub 2}Cu{sub 3}O{sub 7-{delta}}; Efecto de las condiciones de rf sputtering en las propiedades morfologicas y superconductoras en peliculas delgadas de YBa{sub 2}Cu{sub 3}O{sub 7-{delta}}

    Energy Technology Data Exchange (ETDEWEB)

    Acosta, M.; Ares, O.; Sosa, V.; Acosta, C.; Ceh, O. [Departamento deFisica Aplicada, Centro de Investigacion y de Estudios Avanzados, InstitutoPolitecnico Nacional, Unidad Merida, Apartado Postal 73, Cordemex, 97310Merida, Yucatan (Mexico)

    1998-12-31

    Using an off-axis configuration we have prepared in situ superconducting YBaCu{sub 3}O{sub 7-{delta}} (YBaCuO) thin films on SrTiO{sub 3} single-crystal (100) substrates. We have studied the effect of the distance from the target-substrate on the critical temperature (T{sub c}) and current density (J{sub c}) of our films. Our best samples had T{sub c} {approx} 85 K and J{sub c} {approx} 10{sup 6} A/cm{sup 2} at 20 K. Surface topography was examined by atomic force microscopy (AFM) and scanning electron microscopy (Sem), showing the growth of spiral-shaped terraces. The height between steps was of the order of the c-axis length. Samples grown at not optimized positions presented non superconducting regions. The damage of this regions was related to the bombardment of negative oxygen ions or highly-energetic particles present in the plasma. (Author)

  7. Percolation and electronic properties of superconducting (YBa sub 2 Cu sub 3 O sub 7 minus. delta. ) sub 1 minus x Ag sub x ceramics and thick films

    Energy Technology Data Exchange (ETDEWEB)

    Dwir, B.; Pavuna, D.; Affronte, M.; Berger, H. (Swiss Federal Institute of Technology, Lausanne (Switzerland)); Tholence, J.L. (C.R.T.B.T., Grenoble (France))

    1989-09-01

    The authors present the percolation and electronic properties of (Y{sub 1}Ba{sub 2}Cu{sub 3}O{sub 7{minus}{delta}}){sub 1{minus}x}Ag{sub x} compounds in which silver fills the intergranular space without reducing {Tc}, which remains at 92 {plus minus} 1 K. Normal-state resistivity is decreased by up to two orders of magnitude when adding up to 50 wt.% Ag({Tc} = 87 K), and samples exhibit improved contact resistance, better mechanical properties, and resistance to water. They analyzed the percolation properties of these compounds and found that the critical indices t, s are in agreement with percolation theory, but p{sub c} is higher than expected, probably due to the effect of holes. The J{sub c} estimated from magnetization reaches 5 {center dot} 10{sup 4} A/cm{sup 2} (at T = 4.2 K, H = 0) and shows enhancement of 15-50% by addition of {approximately} 10 wt.% Ag, which exists also in samples having a higher J{sub c} due to preparation conditions (temperature). They present preliminary results on the 2D percolation problem in (Y{sub 1}Ba{sub 2}Cu{sub 3}O{sub 7{minus}{delta}}){sub 1{minus}x}Ag{sub x} samples, obtained by preparing Y{sub 1}Ba{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} thick films using the spin-on technique. Preliminary results show good adhesion but a reduced {Tc} of Y{sub 1}Ba{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} films compared with bulk samples.

  8. Brianyoungite/Graphene Oxide Coordination Composites for High-Performance Cu(2+) Adsorption and Tunable Deep-Red Photoluminescence.

    Science.gov (United States)

    Zhu, Xiaobin; Shan, Yun; Xiong, Shijie; Shen, Jiancang; Wu, Xinglong

    2016-06-22

    Graphene oxide (GO) is a good adsorbent for heavy-metal ions because the oxygen functional groups offer active adsorption sites, but a small-size GO with dense oxygen-containing groups has high water solubility causing difficulty in separation. Herein, GO is bound to large brianyoungite (BY) by Zn-O coordination via a hydrothermal reaction that produces BY-GO composites with hollow spherical and flakelike morphologies that are easy to remove. By producing abundant oxygen-containing groups on GO, the Cu(2+) adsorption capacity increases to 1724.1 mg/g, which is the highest value in graphene-related materials. The experimental and theoretical analysis clearly shows that the infrared spectral shifts toward the low-frequency side of C-O-H and O═C-O bending vibrations in the BY-GO composites stem from the Zn(2+) (or Cu(2+)) coordination with O atoms in GO. The BY-GO also exhibits tunable deep-red photoluminescence up to 750 nm with a quantum yield of about 1%, which may be useful in infrared optoelectronic devices and solar energy exploitation. The photoluminescence which is different from that previously reported from chemically derived GO can be attributed to the optical transition in the disorder-induced localized states of the carbon-oxygen functional groups.

  9. Depairing current density of Nd{sub 2−x}Ce{sub x}CuO{sub 4−δ} superconducting films

    Energy Technology Data Exchange (ETDEWEB)

    Kunchur, Milind N., E-mail: kunchur@sc.edu [Department of Physics and Astronomy, University of South Carolina, Columbia, SC 29208 (United States); Dean, Charles; Liang, Manlai; Moghaddam, Nahid S. [Department of Physics and Astronomy, University of South Carolina, Columbia, SC 29208 (United States); Guarino, Anita; Nigro, Angela; Grimaldi, Gaia; Leo, Antonio [CNR-SPIN UOS Salerno, Dipartimento di Fisica “E.R. Caianiello”, Universit di Salerno, I-84084 Fisciano (Salerno) (Italy)

    2013-12-15

    Highlights: •Depairing critical current density of electron-doped Nd{sub 2−x}Ce{sub x}CuO{sub 4−δ} (NCCO). •Independent confirmation of unusually low superfluid density. •Alternative determination of the absolute value of the penetration depth λ(0). -- Abstract: We report a measurement of the depairing critical current density in the electron-doped Nd{sub 2−x}Ce{sub x}CuO{sub 4−δ} cuprate superconductor. Resistance-versus-temperature transition curves measured at high pulsed current densities show the classic proportionality between the transition-temperature shift and the two-thirds power of the applied current. The measurement provides an alternative method for obtaining the penetration depth purely through transport measurements that is not affected by the large paramagnetic background that arises from the Nd{sup 3+} ions, which affects inductive investigations of this quantity.

  10. 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.

  11. Modification of superconducting and resistive properties of HoBa2Cu3O7-δ single crystals under application-removal of high hydrostatic pressure

    Science.gov (United States)

    Vovk, R. V.; Khadzhai, G. Ya.; Dobrovolskiy, O. V.; Kamchatna, S. N.; Chroneos, A.

    2016-06-01

    The influence of a high hydrostatic pressure on the basal-plane electrical resistance along the twin boundaries in underdoped HoBa2Cu3O7-δ single crystals is investigated. An enhancement of the phase segregation caused by the high-pressure-induced redistribution of the labile oxygen has been revealed. The temperature dependences of the electrical resistance above Tc can be approximated well within the framework of the model of s - d electron-phonon scattering.

  12. Microwave dielectric properties of CaCu3Ti4O12-Al2O3 composite

    Science.gov (United States)

    Rahman, Mohd Fariz Ab; Abu, Mohamad Johari; Karim, Saniah Ab; Zaman, Rosyaini Afindi; Ain, Mohd Fadzil; Ahmad, Zainal Arifin; Mohamed, Julie Juliewatty

    2016-07-01

    (1-x)CaCu3Ti4O12 + (x)Al2O3 composite (0 ≤ x ≤0.25) was prepared via conventional solid-state reaction method. The fabrication of sample was started with synthesizing stoichiometric CCTO from CaCO3, CuO and TiO2 powders, then wet-mixed in deionized water for 24 h. The process was continued with calcined CCTO powder at 900 °C for 12 h before sintered at 1040 °C for 10 h. Next, the calcined CCTO powder with different amount of Al2O3 were mixed for 24 h, then palletized and sintered at 1040 °C for 10. X-ray diffraction analysis on the sintered samples showed that CCTO powder was in a single phase, meanwhile the trace of secondary peaks which belong to CaAl2O4 and Corundum (Al2O3) could be observed in the other samples Scanning electron microscopy analysis showed that the grain size of the sample is firstly increased with addition of Al2O3 (x = 0.01), then become smaller with the x > 0.01. Microwave dielectric properties showed that the addition of Al2O3 (x = 0.01) was remarkably reduced the dielectric loss while slightly increased the dielectric permittivity. However, further addition of Al2O3 was reduced both dielectric loss and permittivity at least for an order of magnitude.

  13. 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.

  14. {sup 27}Al and {sup 45}Sc NMR spectroscopy on ScT{sub 2}Al and Sc(T{sub 0.5}T{sup '}{sub 0.5}){sub 2}Al (T = T{sup '} = Ni, Pd, Pt, Cu, Ag, Au) Heusler phases and superconductivity in Sc(Pd{sub 0.5}Au{sub 0.5}){sub 2}Al

    Energy Technology Data Exchange (ETDEWEB)

    Benndorf, Christopher [Institut fuer Anorganische und Analytische Chemie, Westfaelische Wilhelms-Universitaet Muenster (Germany); Institut fuer Physikalische Chemie, Westfaelische Wilhelms-Universitaet Muenster (Germany); Niehaus, Oliver; Janka, Oliver [Institut fuer Anorganische und Analytische Chemie, Westfaelische Wilhelms-Universitaet Muenster (Germany); Eckert, Hellmut [Institut fuer Physikalische Chemie, Westfaelische Wilhelms-Universitaet Muenster (Germany)

    2015-02-15

    The intermetallic Heusler compounds with ScT{sub 2}Al and Sc(T{sub 0.5}T{sup '}{sub 0.5}){sub 2}Al composition with T = T{sup '} = Ni, Pd, Pt, Cu, Ag, Au were synthesized from the elements by arc melting. They crystallize in the cubic MnCu{sub 2}Al type structure, space group Fm anti 3m. The unit cell parameters were determined by powder X-ray diffraction and the structure of Sc(Pd{sub 0.5}Au{sub 0.5}){sub 2}Al was refined on the basis of single-crystal X-ray diffraction. While the majority of the compounds show Pauli-paramagnetism, ScAu{sub 2}Al and the newly synthesized solid solution Sc(Pd{sub 0.5}Au{sub 0.5}){sub 2}Al exhibit superconductivity with transition temperatures of T{sub C} = 4.4 K and T{sub C} = 3.0(1) K, respectively. The superconducting state of Sc(Pd{sub 0.5}Au{sub 0.5}){sub 2}Al was also investigated by electrical resistivity measurements. All the synthesized compounds were furthermore studied by {sup 27}Al and {sup 45}Sc MAS-NMR spectroscopy. The resonance shifts of the synthesized compounds were determined and in Sc(Pd{sub 1-x}Au{sub x}){sub 2}Al a linear relationship between the resonance shifts and the composition was found. Line broadening effects and enhanced quadrupolar interaction strengths observed in the mixed samples can be attributed to the effect of Pd/Au mixing on the 8c Wyckoff site. The NMR spectroscopic data give no clear evidence for or against Sc/Al site disordering. (Copyright copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  15. 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.

  16. Cu2O/ZnO复合光催化剂的制备及对甲基蓝的降解%Preparation of Cu2O/ZnO composite photocatalyst and degradation of methyl blue

    Institute of Scientific and Technical Information of China (English)

    谷芳

    2013-01-01

    Cu2O was fixed by ZnO carrier,Cu2O/ZnO composite photocatalyst was prepared by dip-reduction-air oxidation process in this paper.Cu2O/ZnO composite photocatalyst had better light catalytic properties by controlling reactant ratio,drying temperature and drying time.The composite photocatalyst was used to degrade difficult degradation of acid dye methyl blue in the environment of the common.The influence factors of illumination time,catalyst dosing quantity,pH and initial concentration of solution were investigated.The results showed that the removal rate of methyl blue was 92% incandescent lamp irradiation 60 min.%以ZnO为载体,用其固定Cu2O,利用浸渍-还原-空气氧化法制备Cu2O/ZnO复合光催化剂.通过控制投料比、干燥温度和干燥时间等因素,得到了具有较好光催化性能的Cu2O/ZnO复合光催化剂.利用这种复合光催化剂对环境中常见的难降解的酸性染料甲基蓝进行降解,考察了光照时间、催化剂投加量、溶液pH值、溶液的初始质量浓度等因素对光催化性能的影响.结果表明,在白炽灯照射下反应60 min后,甲基蓝的去除率为92%.

  17. Solvothermal fabrication and enhanced visible light photocatalytic activity of Cu{sub 2}O-reduced graphene oxide composite microspheres for photodegradation of Rhodamine B

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Lingling [Hubei Collaborative Innovation Center for Rare Metal Chemistry, Hubei Normal University, Huangshi 435002 (China); Hubei Key Laboratory of Pollutant Analysis and Reuse Technology, Hubei Normal University, Huangshi 435002 (China); Wang, Guohong, E-mail: wanggh2003@163.com [Hubei Collaborative Innovation Center for Rare Metal Chemistry, Hubei Normal University, Huangshi 435002 (China); Hubei Key Laboratory of Pollutant Analysis and Reuse Technology, Hubei Normal University, Huangshi 435002 (China); Hao, Ruirui [Hubei Collaborative Innovation Center for Rare Metal Chemistry, Hubei Normal University, Huangshi 435002 (China); Hubei Key Laboratory of Pollutant Analysis and Reuse Technology, Hubei Normal University, Huangshi 435002 (China); Han, Deyan, E-mail: handeyan@sohu.com [Hubei Collaborative Innovation Center for Rare Metal Chemistry, Hubei Normal University, Huangshi 435002 (China); Hubei Key Laboratory of Pollutant Analysis and Reuse Technology, Hubei Normal University, Huangshi 435002 (China); Cao, Sheng [Hubei Collaborative Innovation Center for Rare Metal Chemistry, Hubei Normal University, Huangshi 435002 (China); Hubei Key Laboratory of Pollutant Analysis and Reuse Technology, Hubei Normal University, Huangshi 435002 (China)

    2015-12-15

    Graphical abstract: - Highlights: • Cu{sub 2}O-reduced graphene oxide composite spheres were successfully prepared. • The graphene oxide loading played an important role in photocatalytic activity. • A possible enhanced photocatalytic mechanism was proposed. - Abstract: The addition of graphene oxide (GO) in the semiconductors has been regarded as one of the effective methods to enhance their photocatalytic activity. In this study, Cu{sub 2}O-reduced graphene oxide (Cu{sub 2}O-rGO) composites with low loading (0–0.5 wt.%) of graphene oxide (GO) were produced by a one-step green solvothermal method in ethanol system by using Cu(NO{sub 3}){sub 2}·3H{sub 2}O and glutamic acid as copper precursor and reducing agent, respectively. During the solvothermal treatment, GO was reduced to rGO. The as-prepared Cu{sub 2}O-reduced graphene oxide composite microspheres exhibited enhanced photocatalytic activity toward the degradation of RhB aqueous solution under visible light irradiation. At the optimal loading of graphene oxide (0.05 wt.%), Cu{sub 2}O-rGO composites showed the highest photocatalytic activity, exceeding that of pure Cu{sub 2}O and commercial Degussa P25 by a factor of 2.9 and 7.9, respectively. The enhanced photocatalytic activity may be ascribed to the strong coupling interaction between Cu{sub 2}O particles and rGO nanosheets, which reduces the recombination of charge carriers.

  18. 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).

  19. 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.

  20. Effect of Ca substitution on crystal structure and superconducting properties of ferromagnetic superconductor RuSr{sub 2-x}Ca{sub x}Gd{sub 1.4}Ce{sub 0.6}Cu{sub 2}O{sub 10-{delta}}

    Energy Technology Data Exchange (ETDEWEB)

    Fallahi, S.; Mazaheri, M. [Magnet Research Laboratory (MRL), Department of Physics, Sharif University of Technology, P.O. Box 11365-9161, Tehran (Iran, Islamic Republic of); Nikseresht, N.; Ronnow, H.M. [Laboratory for Quantum Magnetism, Ecole Polytechnique Federale de Lausanne (EPFL), CH-1015 Lausanne (Switzerland); Akhavan, M., E-mail: akhavan@sharif.edu [Magnet Research Laboratory (MRL), Department of Physics, Sharif University of Technology, P.O. Box 11365-9161, Tehran (Iran, Islamic Republic of)

    2012-03-15

    We have investigated the effect of Ca substitution for Sr site on structural, magnetic and superconducting properties of RuSr{sub 2-x}Ca{sub x}Gd{sub 1.4}Ce{sub 0.6}Cu{sub 2}O{sub 10-{delta}} system. In this system, the magnetic coupling of RuO{sub 2} and CuO{sub 2} plays an important role in magnetic and superconducting states. X-ray diffraction analysis shows that all samples are single phase and the lattice parameters decrease continuously by increasing Ca content. The onset superconducting transition temperature is found to decrease with Ca substitution. As Ca content increases, rotation of the RuO{sub 6} octahedron increases and Ru-O(1)-Ru angle decreases. These variations strengthen the magnetic moments in the RuO{sub 2} planes. The enhancement of weak ferromagnetic component and hole trapping by Ru magnetic moments in RuO{sub 2} planes reduces the electrical conduction, and destroys the superconducting state in the system. Analysis of the resistivity data ({rho}) based on the hoping conduction mechanism, indicates a variation of the hoping exponent (p) across the magnetic transition at T{sub m}. The hoping exponent p is not affected sharply by Ca concentration. - Highlights: Black-Right-Pointing-Pointer We examined the effect of Ca substitution for Sr on electrical and magnetic properties of Ru1222. Black-Right-Pointing-Pointer Replacement of Sr with Ca reduces the interlayer distance of CuO{sub 2} and RuO{sub 2} layers. Black-Right-Pointing-Pointer The onset superconducting transition temperature is dropped by Ca substitution. Black-Right-Pointing-Pointer We observed the variation of the hopping exponent p across magnetic transition at T{sub m}.

  1. Nano-fabricated superconducting radio-frequency composites, method for producing nano-fabricated superconducting rf composites

    Science.gov (United States)

    Norem, James H.; Pellin, Michael J.

    2013-06-11

    Superconducting rf is limited by a wide range of failure mechanisms inherent in the typical manufacture methods. This invention provides a method for fabricating superconducting rf structures comprising coating the structures with single atomic-layer thick films of alternating chemical composition. Also provided is a cavity defining the invented laminate structure.

  2. Synthesis and properties of a new superconducting compound (ZrCuxSe2)

    Science.gov (United States)

    Generoso, Ana Carolina; Baptista, Naiara; Renosto, Sergio; Jefferson Machado, Antonio

    2012-02-01

    Since the discovery of superconductivity in chalcogenides in Fe-Se system and in iron pnictides much attention have been give for synthesis of new materials which can exhibit superconductivity. Within this context in this work we show results which suggest the existence of a new selenite intercalate with copper atoms in the ZrCuxSe2 nominal composition, where x is 0.1 <= x <= 0.4 interval. A superconductor behavior begins in the ZrCu0.3Se2 with superconducting critical temperature close to 9.0 K. ZrSe2 is a compound which crystallize in the hexagonal symmetry with CdI2 prototype structure belongs to the space group P-32/m1. Indeed, copper is intercalating between Se-Se which have van der Walls interaction in the ZrSe2 compound. This intercalation with copper atoms, produce superconductivity in the matrix compound (ZrSe2) which is not superconductor. The copper intercalation in the matrix compound crystallizes in a LiCrS2 prototype structure.

  3. THE EPITAXIALLY GROWTH AND GD DOPING EFFECT OF YBa2Cu3O7-δ SUPERCONDUCTING THIN FILMS BY LOW-FLUORINE MOD METHOD%低氟MOD法YBa2Cu3O7-δ超导薄膜外延生长及Gd掺杂效应

    Institute of Scientific and Technical Information of China (English)

    孙梅娟; 刘志勇; 白传易; 李敏娟; 郭艳群; 蔡传兵

    2013-01-01

    A series of Y1-xGdxBa2Cu3O7-δ(x=0,0.23,0.5,0.77,1)superconducting thin films were prepared on Hastelloy substrate by low fluorine MOD process.The X ray diffraction (XRD) analysis showed that the epitaxial growth of Gd doped YBa2Cu3O7-δ superconducting thin film is easier to form.The pole figures showed the he inplane orientation of FWHM of Y1-xGdxBa2Cu3O7-δ changes nonlinearly with increasing the nominal amount of Gddoping.The doped films have higher performance and better surface morphology,compared with pure YBCO thin films.Appropriate doping may lead to the enhancement of critical current density in 77K,self field,which may due to modulation structure formed by doping can be effective flux pinning centers.%通过低氟金属有机物沉积方法(MOD)在哈氏合金基底上制备了一系列Y1-xGdxBa2Cu3O7-δ(x=0,0.23,0.5,0.77,1)超导薄膜.X光衍射(XRD)分析表明:Gd3+掺杂使YBa2Cu3 O7-δ超导薄膜外延生长易于形成,X光极图显示,随掺杂量增加,其面内取向半高宽随名义掺杂量的增加呈非线性变化.与纯YBCO相比,掺杂薄膜具有更好的表面形貌.Gd3+掺杂的样品的超导性能均优于纯YBCD的性能.在77K、自场下适当掺杂量有助于超导薄膜临界电流密度的提高,这可能由于掺杂形成的调制结构可以作为磁通钉扎中心.

  4. Cryogenic deformation of high temperature superconductive composite structures

    Energy Technology Data Exchange (ETDEWEB)

    Roberts, Peter R. (Groton, MA); Michels, William (Brookline, MA); Bingert, John F. (Jemez Springs, NM)

    2001-01-01

    An improvement in a process of preparing a composite high temperature oxide superconductive wire is provided and involves conducting at least one cross-sectional reduction step in the processing preparation of the wire at sub-ambient temperatures.

  5. Photo-degradation of Methyl Orange by Polysaccharides/LaFe0.8Cu0.2O3 Composite Films

    Directory of Open Access Journals (Sweden)

    Aojie Deng

    2014-03-01

    Full Text Available The objective of this work was to prepare a series of composite films (polysaccharides with LaFe0.8Cu0.2O3 for the degradation of methyl orange under ultraviolet irradiation. LaFe0.8Cu0.2O3 was prepared by a sol-gel method, and the composite films were obtained by cross-linking reactions between polysaccharides (xylan and chitosan and LaFe0.8Cu0.2O3. Physical and chemical properties of the composite films were investigated by XRD, FTIR, SEM, and BET. Moreover, the influence of the weight ratio of polysaccharide to LaFe0.8Cu0.2O3 on the methyl orange degradation reaction was also studied. Results showed that 67% of the degradation efficiency was achieved within 480 min using chitosan/LaFe0.8Cu0.2O3 (2:1 as photocatalysts, while 58% was for xylan/LaFe0.8Cu0.2O3 (1:1. The difference was due to the variety in the structure of chitosan and xylan.

  6. An investigation of stoichiometry and thermo-mechanical processing parameters of (Pb,Bi) $_{2}Sr _{2}Ca _{2}Cu _{3}O _{x}$ superconducting tapes

    CERN Document Server

    Feltham, S P

    2001-01-01

    excess tapes, with an l sub c of 17 A and 14 A, respectively. The mechanical deformation experienced by 37 filament multifilamentary tapes before thermal processing was studied. The final wire diameter, the rolling steps used to convert the wire to a tape were investigated. It was found that tapes with thin, high aspect ration filaments produced a higher critical current density. High aspect ration filaments were produced within the conductor using small rolling steps of 20 mu m followed by one or two 100 mu m steps to the as-rolled thickness. Through attempting to optimise both the diameter and the rolling regime a 20 % improvement in the J sub c was obtained from 12 KAcm sup - sup 2 to 14.5 KAcm sup - sup 2. Using the improved deformation scheme from the above tapes were subjected to various cooling rates. The magnetic field dependence of the tapes was improved using a slow cooling rate (1 deg C/hr 818- 730 deg C). The critical current density of the tapes could be improved from a maximum of 13 KAcm sup - s...

  7. Preparation of Cu/n-TiO2/PBO composite fibers%Cu/n-TiO2/PBO复合纤维的制备

    Institute of Scientific and Technical Information of China (English)

    刘雪峰; 隋守军; 谢建新

    2008-01-01

    以PBO纤维为基体,采用浸渍涂覆法在PBO纤维表面包覆纳米TiO2膜,采用化学镀法将Cu沉积到纳米TiO2膜表面,制备了Cu/n-TiO2/PBO复合纤维,研究了影响纳米TiO2沉积速率和Cu沉积速率的主要因素.结果表明,纳米TiO2与偶联剂的浓度配比是影响纳米TiO2包膜形成的主要因素,当纳米TiO2与偶联剂浓度配比为1:1.2时,制备的n-TiO2/PBO复合纤维界面结合力较好,且纳米TiO2包覆层比较均匀.影响化学镀铜的主要因素有镀液成分、反应时间和反应温度.在镀液成分的浓度配比为CuSO4·5H2O 12 g·L-1、KNaC4 H4O68 g·L-1、HCHO 6 mL·L-1和NaOH 10 g·L-1,反应温度50℃,镀铜时间20 min的条件下,制备了负载均匀,界面结合力较好的Cu/n-TiO2/PBO复合纤维.

  8. Structural and low-field magnetic characterization of superconducting MgB{sub 2} wires

    Energy Technology Data Exchange (ETDEWEB)

    Kilic, A. [Faculty of Sciences, Department of Physics, Ankara University, 06100-Tandogan/Ankara (Turkey); Okur, S. [Izmir Institute of Technology, Department of Physics, 35437-Urla/Izmir (Turkey); Gueclue, N. [Faculty of Sciences and Art, Department of Physics, Gaziosmanpasa University, 60100-Taslicftlik/Tokat (Turkey)]. E-mail: guclu06@hotmail.com; Koelemen, U. [Faculty of Sciences and Art, Department of Physics, Gaziosmanpasa University, 60100-Taslicftlik/Tokat (Turkey); Uzun, O. [Faculty of Sciences and Art, Department of Physics, Gaziosmanpasa University, 60100-Taslicftlik/Tokat (Turkey); Oezyuezer, L. [Izmir Institute of Technology, Department of Physics, 35437-Urla/Izmir (Turkey); Gencer, A. [Faculty of Sciences, Department of Physics, Ankara University, 06100-Tandogan/Ankara (Turkey)

    2004-10-01

    Superconducting MgB{sub 2} composite wires were prepared by packing blend of MgB{sub 2} inside of Cu tubes using powder in tube (PIT) method. The produced samples of the wires were then characterised by using SEM, XRD and AC susceptibility measurements. The measured fundamental susceptibility is compared with Bean model. We have obtained an empirical functions for the penetration field H{sub p} = H{sub {alpha}}(1-t){sup {beta}}, where t is the reduced temperature. In addition, ac losses were calculated at the same fixed temperatures to compare theoretical solutions. There is a qualitative agreement between the experimental results and theory.

  9. Tribological properties of Cu based composite materials strengthened with Al2O3 particles

    Directory of Open Access Journals (Sweden)

    J. W. Kaczmar

    2012-12-01

    Full Text Available In the present work copper was strenghtened with 20 and 30 vol. % of alumina particles characterized by diameter of 3-6μm. The copperbased composite materials were manufactured by the squeeze casting method. Preheated preforms made from Al2O3 particles were placedin the desired place in the heated cast die and the squeeze casting process with liquid copper was performed applying the infiltrationpressure of 90MPa and pressure was kept for 10-15s until solidification was complete. The microstructure and physical properties: Brinell hardness (HBW and density were characterized. Metallografic examinations showed that alumina particles were uniformly distributed in the copper matrix. Hardness of 208 HBW for composite materials containing 30 vol.% of particles was achieved. Wear investigations were performed applying the tribological pin-on-disc tester. Friction forces between copper based composite materials containing 20 and 30 vol. % of Al2O3 particles and cast iron were registered and wear was determined on the base of the specimen mass loss after 1.0, 3.5 and 8.5 km friction distance.

  10. The influence of powder particle size on properties of Cu-Al2O3 composites

    Directory of Open Access Journals (Sweden)

    Rajković V.

    2009-01-01

    Full Text Available Inert gas atomized prealloyed copper powder containing 2 wt.% Al (average particle size ≈ 30 μm and a mixture consisting of copper (average particle sizes ≈ 15 μm and 30 μm and 4 wt.% of commercial Al2O3 powder particles (average particle size ≈ 0.75 μm were milled separately in a high-energy planetary ball mill up to 20 h in air. Milling was performed in order to strengthen the copper matrix by grain size refinement and Al2O3 particles. Milling in air of prealloyed copper powder promoted formation of finely dispersed nano-sized Al2O3 particles by internal oxidation. On the other side, composite powders with commercial micro-sized Al2O3 particles were obtained by mechanical alloying. Following milling, powders were treated in hydrogen at 400 0C for 1h in order to eliminate copper oxides formed on their surface during milling. Hot-pressing (800 0C for 3 h in argon at pressure of 35 MPa was used for compaction of milled powders. Hot-pressed composite compacts processed from 5 and 20 h milled powders were additionally subjected to high temperature exposure (800°C for 1 and 5h in argon in order to examine their thermal stability. The results were discussed in terms of the effects of different size of starting powders, the grain size refinement and different size of Al2O3 particles on strengthening, thermal stability and electrical conductivity of copper-based composites.

  11. Structural studies of type N superconductive compounds: R{sub 2-x}Ce{sub x}CuO{sub 4{+-}{delta}} (R = Gd, Eu, Sm, Nd, Pr); influences of chemical treatments on physical properties; Etudes structurales des composes supraconducteurs de type N: R{sub 2-x}Ce{sub x}CuO{sub 4{+-}{delta}} (R = Gd, Eu, Sm, Nd, Pr); influences des traitements chimiques sur les proprietes physiques

    Energy Technology Data Exchange (ETDEWEB)

    Vigoureux, P.

    1995-06-01

    Different chemical treatments of R{sub 2-x}Ce{sub x}CuO{sub 4{+-}{delta}} compounds monocrystals (gadolinium, europium, samarium, neodymium and praseodymium cuprates) modify their physical properties especially their superconductive properties. The presented chemical treatments are: the substitution of the trivalent rare earth element R by an other trivalent lanthanide, its substitution by tetravalent cerium, and heat treatment under low oxygen pressure. After these chemical treatments, structural modifications are observed by neutrons and X-rays diffraction, and allow to precise their actions: size effect of the rare earth element on the deformation of the CuO{sub 2} planes, links between deformation and superconductivity and magnetic properties. (A.B.). 394 refs/.

  12. Large area superconducting YBa sub 2 Cu sub 3 O sub 7-x films grown by single target ion beam sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Gauzzi, A.; Lucia, M.L.; Kellett, B.J.; James, J.H.; Pavuna, D. (Inst. of Micro- and Optoelectronics, Swiss Federal Inst. of Tech., Lausanne (Switzerland))

    1991-10-20

    We have demonstrated, by using a simple single YBa{sub 2}Cu{sub 3}O{sub 7-x} target ion beam system that, with a sufficiently low power ion beam, preferential sputtering is avoided and high-quality YBa{sub 2}Cu{sub 3}O{sub 7-x} films are deposited over areas larger than {approx equal}30 cm{sup 2} in a reproducible way. As-deposited films on <100>SrTiO{sub 3} are 50-100 nm thick, c-oriented and show the following reproducible electrical properties (within the given variations): Tc{sub 0}=90{+-}0.5 K, transitions widths less than 1 K, j{sub c}(77K)=1.0-1.2x10{sup 6} A cm{sup -2}, {rho}(300K)=300{+-}50 {mu}{Omega} cm, {rho}(300 K)/{rho}(100 K)=2.9{+-}0.1. The extrapolated residual resistivity {rho}{sub res}(0 K) is between 0 and 5% of {rho}(300 K). (orig.).

  13. Study by neutrons diffusion and X-rays of structural and magnetic properties of Bi{sub 2}Sr{sub 2}Ca{sub n-1}Cu{sub n}O{sub 2n+4+{delta}} type superconductive cuprates; Etude par diffusion des neutrons et des rayons X des proprietes structurales et magnetiques des cuprates supraconducteurs de type Bi{sub 2}Sr{sub 2}Ca{sub n-1}Cu{sub n}O{sub 2n+4+{delta}}

    Energy Technology Data Exchange (ETDEWEB)

    Vasiliu-Doloc, L.

    1995-09-22

    In this work we have used inelastic and elastic neutron and X-ray scattering techniques for characterizing the incommensurate structural distortions in compounds belonging to the family Bi{sub 2}Sr{sub 2}Ca{sub n-1}Cu{sub n}O{sub 2n+4+{delta}} of high-Tc superconducting cuprates. We have searched the existence of structural instabilities specific of the CuO{sub 2} planes and of magnetic instabilities. The modulated structure of the 2212 phase has been refined from single-crystal neutron diffraction results and importance of distortion of CuO{sub 2} planes has thus been determined. It is shown that the additional oxygen is not ordered three-dimensionally within the modulated structure and that the information about it is contained in diffuse scattering results. A model of the short-range order associated with additional oxygen atoms is proposed and discussed. The temperature studies of the long-range order have shown a great stability of the amplitude and period of the incommensurate distortion wave in the one-layer, as well as in the double-layer compounds, either superconducting or insulating. We find such a behaviour to be highly incompatible with a distortion resulting from a charge-density-wave instability. The results we have obtained indicate that the bismuth-based high-Tc superconducting cuprates have essentially the same physics of the CuO{sub 2} planes as the previous two families, La{sub 2-x}Sr{sub x}CuO{sub 4} and YBa{sub 2}Cu{sub 3}O{sub 6+{delta}}, being at the proximity of three instabilities: a metal-insulator transition, an antiferromagnetic instability and a structural instability specific of the CuO{sub 2} planes. (author).

  14. Effect of Ag2O addition on the intergranular properties of the superconducting Bi-(Pb)-Sr-Ca-Cu-O system

    Science.gov (United States)

    Karaca, I.; Çelebi, S.; Varilci, A.; Malik, A. I.

    2003-01-01

    The effect of Ag2O addition on the Bi-(Pb)-Sr-Ca-Cu-O system has been investigated in terms of ac susceptibility, phase evolution, critical current density and critical temperature. It was found that as the amount of Ag2O addition increases, the intergranular critical current density decreases in our samples (Bi1.84Pb0.34Sr1.91Ca2.03Cu3.06O10) fabricated by ammonium nitrate technique. The analysis for comparison is based on the suppression degree of the diamagnetic behaviour with respect to fields, rapid or slow shift of the summit in chi'(T) to lower temperature with increasing field amplitude and the sharpness of the transition of chi'(T) for intergranular component for the same field amplitude. We also qualitatively discuss experimental results in the framework of the critical state model. The room temperature XRD diagram indicates the presence of large amount of high-Tc (2223) phase. The percentage of Bi-2223 phase in the phase mixture was estimated from the intensities of high-Tc (2223) and low-Tc (2212) phase peaks as 78% for the pure BSCCO sample. Among the Ag2O-added BSCCO samples studied, the one in which 5 wt%Ag2O was added shows the highest rate of Bi-2223 formation as 92%. The SEM analysis reveals some morphological changes induced by silver addition.

  15. Effects of lithium (Li) on lithium-cuprous-oxide (Li-Cu2O) composite films grown by using electrochemical deposition for a PEC photoelectrode

    Science.gov (United States)

    Kim, Tae Gyoum; Ryu, Hyukhyun; Lee, Won-Jae

    2016-01-01

    In this study, Li-Cu2O composite films were grown on fluorine-doped tin-oxide (FTO) substrates by using the electrochemical deposition method. Various amounts of lithium (Li) were added to grow the Li-Cu2O composite films. We analyzed the morphology, structure, photocurrent density and photo-stability of the Li-Cu2O composite films by using various measurements such as field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD) and potentiostat/galvanostat measurements, respectively. As a result, the highest XRD Cu2O (111)/ LiO (011) peak intensity ratio was obtained for the 10-wt% sample, which also had the highest photocurrent density value of -5.00 mA/cm2. The highest photocurrent density value for the 10-wt% sample was approximately 5 times greater than that of the 0-wt% sample. As shown by this result, we found that adding Li could improve the photocurrent values of Li-Cu2O composite films.

  16. 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}.

  17. Improved structural properties and crystal coherence of superconducting NdBa2Cu3O7-δ films grown by pulsed laser ablation

    Science.gov (United States)

    Abrecht, M.; Ariosa, D.; Schmauder, T.; Saleh, S. A.; Rast, S.; Pavuna, D.

    2000-11-01

    We report on improved structural, crystallographic and electrical properties of epitaxial NdBa2Cu3O7-δ (NBCO) films grown on SrTiO3 by `off-axis' pulsed laser deposition (PLD). Transport and XRD studies show that the c-axis-oriented epitaxial films, with critical temperatures of 90-92 K, are mono phase and single-crystalline. Furthermore, very smooth, almost outgrowth-free surfaces and crystal coherences of up to 0.8 µm (to our knowledge the best value ever reported for high-Tc films) were obtained.

  18. 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.

  19. Synthesis and analysis of nanocrystalline β1-Cu3Al and β2-NiAl intermetallic-reinforced aluminum matrix composite by high energy ball milling

    Science.gov (United States)

    Nguyen, Hong-Hai; Nguyen, Minh-Thuyet; Kim, Won Joo; Kim, Jin-Chun

    2017-01-01

    Nanocrystalline β1-Cu3Al and β2-NiAl intermetallic compounds were in-situ reinforced in the aluminum matrix with the atomic composition of Al67Cu20Ni13 by the mechanical alloying of elemental powders. Both β1-Cu3Al, β2-NiAl phases that can be only co-synthesized in Cu base alloys have been obtained after 15h milling in this study. The phase evolution during milling process was investigated by X-ray diffraction. The β1-Cu3Al, β2-NiAl phases were metastable with further milling time up to 40 h. Specially, unreacted Al matrix has been totally transformed to amorphous state in the final powder. A remarkable crystalline size of 6.5 nm was reached after 15 h milling time. Thermal stability of the milled powder was also studied by differential thermal analysis. It is shown that β1-Cu3Al, β2-NiAl phases were stable up to higher than 550 °C. Moreover, the inter-diffusion between Al matrix and Cu3Al within the temperature range of 620-740 °C led to the formation of superstructure ζ1-Al3Cu4 phase.

  20. Momentum dependence of the electron-phonon coupling and self-energy effects in superconducting YBa2Cu3O7 within the local density approximation.

    Science.gov (United States)

    Heid, Rolf; Bohnen, Klaus-Peter; Zeyher, Roland; Manske, Dirk

    2008-04-04

    Using the local density approximation and a realistic phonon spectrum we determine the momentum and frequency dependence of alpha(2)F(k,omega) in YBa(2)Cu(3)O(7) for the bonding, antibonding, and chain band. The resulting self-energy Sigma is rather small near the Fermi surface. For instance, for the antibonding band the maximum of ReSigma as a function of frequency is about 7 meV at the nodal point in the normal state and the ratio of bare and renormalized Fermi velocities is 1.18. These values are a factor of 3-5 too small compared to the experiment showing that only a small part of Sigma can be attributed to phonons. Furthermore, the frequency dependence of the renormalization factor Z(k,omega) is smooth and has no anomalies at the observed kink frequencies which means that phonons cannot produce well-pronounced kinks in stoichiometric YBa(2)Cu()3)O(7), at least, within the local density approximation.

  1. Effects of TiO{sub 2} addition and electron irradiation on superconducting and mechanical properties of Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} (Bi-2212) superconductor

    Energy Technology Data Exchange (ETDEWEB)

    Hamid, Nasri A., E-mail: Nasri@uniten.edu.my; Abdullah, Mohamad Hafizi Pandak [Nuclear Energy Center, College of Engineering, Universiti Tenaga Nasional, Jalan IKRAM-UNITEN, 43000 Kajang, Selangor (Malaysia); Abdullah, Yusof [Materials Technology Group, Industrial Technology Division, Malaysian Nuclear Agency, Bangi, 43000 Kajang, Selangor (Malaysia)

    2014-02-12

    Titanium Oxide (TiO{sub 2}) compounds having very high melting point with lower heat capacity, is an excellent candidate for reinforcement of brittle materials such as superconductor ceramics. In addition to high melting point, the TiO{sub 2} is also capable of establishing flux pinning centers in bismuth-based superconductors such as the Bi-2212. To further enhance the flux pinning properties, irradiation is one of the techniques that can be used to re-create the required point defects. In this study, the effects of TiO{sub 2} addition and electron irradiation on Bi-2212 superconductor were studied. TiO{sub 2} added Bi-2212 superconductor samples with 5%, 10% and 15% weight percentage addition respectively, were prepared using the conventional solid-state reaction method. The samples were irradiated with electron beam with radiation dose of 100 KGray. Characterization was performed by X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). The transition temperature (T{sub c}) and the critical current density (J{sub c}) of the samples were also measured. The XRD patterns for all the samples show well-defined peaks all of which could be indexed on the basis of a Bi-2212 phase structure. In addition, the XRD patterns indicate that electron irradiation did not change the structure of Bi-2212 superconducting phase. Results of SEM micrographs show disorientation in the texture of the microstructure for samples that are subjected to electron irradiation. The grains are seen to align randomly with higher degree of orientation. With regard to TiO{sub 2} additions, only small TiO{sub 2} addition sustained the superconducting properties upon irradiation. Addition of more than 5% weight percentage of TiO{sub 2} degrades the superconducting properties of the irradiated samples. Formation of weak-links may result in higher grain boundaries orientation within the superconducting grains and thus deteriorates the inter-grains connectivity and resulted in lower T{sub c

  2. Elaboration and performances of bulk textured superconducting YBa{sub 2}Cu{sub 3}O{sub 7} materials of increasing size; Elaboration et performances de materiaux supraconducteurs YBa{sub 2}Cu{sub 3}O{sub 7} massifs textures de taille croissante

    Energy Technology Data Exchange (ETDEWEB)

    Chaud, X.; Gautier-Picard, P.; Beaugnon, E.; Bourgault, D.; Tournier, R. [CNRS, Grenoble (France). EPM-Matformag; Porcar, L. [CNRS, Grenoble (France). EPM-Matformag]|[Schneider Electric S.A., Grenoble (France); Erraud, A.; Tixador, P. [CNRS, Grenoble (France). CRTBT-LEG

    1998-03-01

    Industrial applications of the bulk superconducting YBa{sub 2}Cu{sub 3}O{sub 7} material imply to control the growth of large oriented monodomains in samples of big size (several centimeters). The laboratory EPM-Matformag is committed to produce such materials according to three different methods (zone melting, solidification controlled by a magnetic field, crystal growth from a seed). The results obtained show that it is possible by such methods to elaborate a material with high performances at the centimeter scale and to produce it in series. The availability of such materials allows the measure of physical properties on a large scale and the testing of prototypes for cryo-electrotechnical applications (magnetic bearing, flywheel, coupling device, current lead..). (orig.). 17 refs.

  3. 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.

  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. Microfluidic reactor synthesis and photocatalytic behavior of Cu@Cu{sub 2}O nanocomposite

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Lei, E-mail: xulei_kmust@aliyun.com [National Local Joint Laboratory of Engineering Application of Microwave Energy and Equipment Technology, Faculty of Metallurgical and Energy Engineering, Kunming University of Science and Technology, Kunming 650093 (China); Mechanical Engineering, University of Washington, Seattle, WA 98195 (United States); Srinivasakannan, C. [Chemical Engineering Program, The Petroleum Institute, PO Box 253, Abu Dhabi (United Arab Emirates); Peng, Jinhui, E-mail: jhpeng@kmust.edu.cn [National Local Joint Laboratory of Engineering Application of Microwave Energy and Equipment Technology, Faculty of Metallurgical and Energy Engineering, Kunming University of Science and Technology, Kunming 650093 (China); Yan, Mi [Faculty of Mathematical and Physical Sciences, University College London, London WC1E 6BT (United Kingdom); Zhang, Di [Mechanical Engineering, University of Washington, Seattle, WA 98195 (United States); Zhang, Libo [National Local Joint Laboratory of Engineering Application of Microwave Energy and Equipment Technology, Faculty of Metallurgical and Energy Engineering, Kunming University of Science and Technology, Kunming 650093 (China)

    2015-03-15

    Highlights: • The Cu@Cu{sub 2}O nanocomposites were synthesized in microfluidic reactor followed by oxidation process. • The Cu@Cu{sub 2}O composite particle is on nanoscale exhibiting an open bicontinuous structure. • The amount of Cu{sub 2}O can be controlled by varying drying temperature. • The binary Cu@Cu{sub 2}O–H{sub 2}O{sub 2} systems exhibit an excellent photocatalyst for degradation methylene blue under UV irradiation. - Abstract: The Cu@Cu{sub 2}O nanocomposites were synthesized by solution-phase synthesis of Cu nanoparticles in microfluidic reactor at room temperature, followed by controlling the oxidation process. The size, morphology, elemental compositions, and the chemical composition on the surface of Cu@Cu{sub 2}O nanocomposite were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Experimental results demonstrated that the surface of the Cu nanoparticles was oxidized to Cu{sub 2}O which serves as the shell of nanoparticle. The amount of Cu{sub 2}O can be controlled by varying the drying temperature. Additionally the binary Cu@Cu{sub 2}O nanocomposite along with H{sub 2}O{sub 2} exhibited its potential as an excellent photocatalyst for degradation of methylene blue (MB) under UV irradiation.

  6. Creation of Cu2O@TiO2 composite photocatalysts with p-n heterojunctions formed on exposed Cu2O facets, their energy band alignment study, and their enhanced photocatalytic activity under illumination with visible light.

    Science.gov (United States)

    Liu, Lingmei; Yang, Weiyi; Sun, Wuzhu; Li, Qi; Shang, Jian Ku

    2015-01-28

    The creation of photocatalysts with controlled facets has become an important approach to enhance their activity. However, how the formation of heterojunctions on exposed facets could affect their photocatalytic performance ranking had not yet been investigated. In this study, Cu2O@TiO2 core-shell structures were created, and Cu2O/TiO2 p-n heterojunctions were formed on various exposed facets of Cu2O cubes, Cu2O cuboctahedra, and Cu2O octahedra, respectively. These Cu2O@TiO2 polyhedra demonstrated an enhanced photocatalytic degradation effect on Methylene Blue (MB) and 4-nitrophenol (4-NP) under visible light illumination, because of the enhanced charge carrier separation by the formation of Cu2O@TiO2 p-n heterojunctions. It was further found that their photocatalytic performance was also facet-dependent as pure Cu2O polyhedra, while the photocatalytic performance ranking of these Cu2O@TiO2 polyhedra was different with that of their corresponding Cu2O polyhedron cores. By the combination of optical property measurement and XPS analysis, the energy band alignments of these Cu2O@TiO2 polyhedra were determined, which demonstrated that Cu2O@TiO2 octahedra had the highest band offset for the separation of charge carriers. Thus, the charge-carrier-separation-driven force in Cu2O@TiO2 polyhedra was different from their corresponding Cu2O polyhedron cores, which resulted in their different surface photovoltage spectrum (SPS) responses and different photocatalytic performance rankings.

  7. Removal of Cu 2+ Ions from Aqueous Medium Using Clinoptilolite/Emeraldine Base Composite

    Directory of Open Access Journals (Sweden)

    Silviya I. Lavrova

    2016-12-01

    Full Text Available The aim of this study was to investigate the removal efficiency of in situ synthesized composites consisted of emeraldine base and clinoptilolite on copper ions removal from aqueous medium. Two composite materials (Composite I and Composite II with different quantity of clinoptilolite were synthesised. The influence of the composite dosage, the contact time and the initial copper ions concentration has been studied. The results show that the significant removal of the copper ions becomes at the first minute of the contact between the composite material and the aqueous medium and the longer contact time leads to increasing of the copper ions removal. The removal efficiency at the 1st minute was 57.5% and 77.3% using Composite Iand Composite II, respectively. Maximum removal efficiency of 87.3% and 96.8% was achieved at the same dosage of Composite I and Composite II, respectively, at contact time of 360 minutes and temperature of 24 °C.

  8. Observation of magnetic order in a superconducting YBa2Cu36.6

    Energy Technology Data Exchange (ETDEWEB)

    Mook Jr, Herbert A [ORNL; Sidis, Y. [Laboratoire Leon Brillouin, France; Fauque, B. [Laboratoire Leon Brillouin, France; Baledent, V. [Laboratoire Leon Brillouin, France; Bourges, P. [Laboratoire Leon Brillouin, France

    2008-07-01

    Polarized beam neutron-scattering measurements on a highly perfect crystal of YBa{sub 2}Cu{sub 3}O{sub 6.6} show a distinct magnetic transition to a different phase with an onset at about 235 K, the temperature expected for the pseudogap transition. The moment is found to be about 0.1{micro}{sub B} for each sublattice and has a correlation length of at least 75 {angstrom}. We found the critical exponent for the magnetic neutron intensity to be 2=0.37 {+-} 0.12. This is the proper range for the class of transition that has no specific-heat divergence possibly explaining why none is found at the pseudogap transition.

  9. A multiscale and multiphysics model of strain development in a 1.5 T MRI magnet designed with 36 filament composite MgB2 superconducting wire

    Science.gov (United States)

    Amin, Abdullah Al; Baig, Tanvir; Deissler, Robert J.; Yao, Zhen; Tomsic, Michael; Doll, David; Akkus, Ozan; Martens, Michael

    2016-05-01

    High temperature superconductors such as MgB2 focus on conduction cooling of electromagnets that eliminates the use of liquid helium. With the recent advances in the strain sustainability of MgB2, a full body 1.5 T conduction cooled magnetic resonance imaging (MRI) magnet shows promise. In this article, a 36 filament MgB2 superconducting wire is considered for a 1.5 T full-body MRI system and is analyzed in terms of strain development. In order to facilitate analysis, this composite wire is homogenized and the orthotropic wire material properties are employed to solve for strain development using a 2D-axisymmetric finite element analysis (FEA) model of the entire set of MRI magnet. The entire multiscale multiphysics analysis is considered from the wire to the magnet bundles addressing winding, cooling and electromagnetic excitation. The FEA solution is verified with proven analytical equations and acceptable agreement is reported. The results show a maximum mechanical strain development of 0.06% that is within the failure criteria of -0.6% to 0.4% (-0.3% to 0.2% for design) for the 36 filament MgB2 wire. Therefore, the study indicates the safe operation of the conduction cooled MgB2 based MRI magnet as far as strain development is concerned.

  10. 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.

  11. Structural characterization and colour of MgxCu3-xV2O8 (0 ≤ x ≤ 3) and MgyCu2-yV2O7 (0 ≤ y ≤ 2) compositions.

    Science.gov (United States)

    Tena, M A; García-Granda, Santiago

    2015-01-01

    In this study, MgxCu3-xV2O8 (0 ≤ x ≤ 3) and MgyCu2-yV2O7 (0 ≤ y ≤ 2) compositions were synthesized by the chemical coprecipitation method and characterized by X-ray diffraction, UV-vis-NIR spectroscopy and CIE L* a* b* parameters measurements. Melting points of compounds Cu3V2O8 and Cu2V2O7 are 780°C and 790°C, respectively. The addition of small amounts of Mg (II), MgxCu3-xV2O8 (x < 1.0) and MgyCu2-yV2O7 (y < 0.5) fused compositions, was not sufficient to stabilize structures at 800°C. For the Mg2CuV2O8 (x = 2.0) composition fired at 800°C, Mg (II) incorporated into the monoclinic Cu3V2O8 structure stabilizes this crystalline phase. At 1000°C, orthorhombic Mg3V2O8 structure from this composition was obtained. Solid solutions with orthorhombic symmetry were detected from the prepared compositions fired at 1000°C when 1.0 ≤ x ≤ 3.0. The difference of coloration of Cu, Mg vanadates might be explained by the presence of a strong charge transfer band in visible spectra.

  12. Phase-glass scaling near the coherence transition in granular HoBa{sub 2}Cu{sub 3}O{sub 7-{delta}} superconducting thin films

    Energy Technology Data Exchange (ETDEWEB)

    Roa-Rojas, J.; Landinez Tellez, D.A. [Grupo de Fisica de Nuevos Materiales, Departamento de Fisica, Universidad Nacional de Colombia, A. A. 14490, Bogota DC (Colombia); Prieto, P. [Grupo de Peliculas Delgadas, Departamento de Fisica, Universidad del Valle, A. A. 25360, Cali (Colombia)

    2005-07-01

    Systematic measurements of electrical magnetoconductivity near the coherence transition of granular HoBa{sub 2}Cu{sub 3}O{sub 7-{delta}} thin films are reported. Experiments performed in magnetic fields ranging from 0 to 2500 Oe reveal that close to the coherence transition temperature T{sub c0}(H), the correlation length scales as a power law of temperature with a thermal-dependent critical exponent, {nu}. In low external fields the corresponding value of {nu} is consistent with the two-dimensional phase-glass model, which is in the same dynamical universality class of the so-called vortex-glass model. At applied fields H > 1000 Oe, the vortex dynamics becomes stronger and the coherence transition is not observed. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  13. Influence of gold diffusion-doped on phase formation, superconducting and microstructure properties of Bi1.8Pb0.35Sr1.9Ca2.1Cu3Oy superconductors

    Science.gov (United States)

    Ozturk, O.; Akdogan, M.; Terzioglu, C.; Gencer, A.

    2009-03-01

    We report on low-field magnetic properties of gold diffusion-doped Bi1.8Pb0.35Sr1.9Ca2.1Cu3Oy superconducting bulk samples by performing ac susceptibility measurements. The undoped samples were prepared by the standard solid-state reaction method. Doping of Bi1.8Pb0.35Sr1.9Ca2.1Cu3Oy was carried out by means of Au-diffusion during sintering from an evaporated gold film on pellets. To investigate the effect of gold-diffusion and diffusion-annealing duration on transport, magnetic and microstructure properties of the superconducting samples we performed magnetoresistivity, scanning electron microscopy (SEM) and X-ray diffraction (XRD) measurements. The ac susceptibility as a function of temperature measurements were carried out at different values of the ac magnetic field amplitudes (Hac) in the range between 20A/m and 320 A/m for 211 Hz. The imaginary part of ac susceptibility measurements is used to calculate intergranular critical current density Jc(Tp) using the Bean Model. Jc(Tp) is seen to increase from 60 A cm-2 to 90 A cm-2 with increasing diffusion-annealing time from 10 h to 50 h. The peak temperature, Tp, in the imaginary part of the ac susceptibility is shifted to a lower temperature with decreasing diffusion-annealing duration as well as increasing ac magnetic fields. The force pinning density (αjj (0)) increased with increasing diffusion annealing time. The value of Tc in gold-diffused samples, in comparison with the undoped samples, increased from 100 ± 0.2 K to 104 ± 0.2 K. It was observed that the value of Tc-offset of the gold-doped samples enhanced with further increasing diffusion-annealing duration. XRD patterns and SEM micrographs are used to obtain information about Bi-2223 phase ratio, lattice parameters and grain size of the samples. Gold doping enhanced the formation high-Tc phase and increased the grain size. The possible reasons for the observed improvements in transport, microstructure and magnetic properties due to Au diffusion and

  14. Structures of incommensurate and commensurate composite crystals NaxCuO2 (x=1.58, 1.6, 1.62).

    Science.gov (United States)

    van Smaalen, Sander; Dinnebier, Robert; Sofin, Mikhail; Jansen, Martin

    2007-02-01

    NaxCuO2 (x approximately 1.6) has been synthesized for different compositions x, resulting in both commensurate and incommensurate composite crystals. The crystal structures are reported for two incommensurate compounds (x=1.58 and 1.62) determined by Rietveld refinements against X-ray powder diffraction data. The incommensurate compounds and commensurate Na8Cu5O10 (x=1.6) are found to possess similar structures, with valence fluctuations of Cu2+/Cu3+ as the origin of the modulations of the CuO2 subsystems; the displacive modulations of Na being defined by the closest Na-O contacts between the subsystems. A comparison of the structure models obtained from single-crystal X-ray diffraction, synchrotron-radiation X-ray powder diffraction and X-ray powder diffraction with Cu Kalpha1 radiation indicates that single-crystal X-ray diffraction is by far the most accurate method, while powder diffraction with radiation from an X-ray tube provides the least accurate structure model.

  15. Structures of incommensurate and commensurate composite crystals Na{sub x}CuO{sub 2} (x=1.58,1.6,1.62)

    Energy Technology Data Exchange (ETDEWEB)

    Smaalen, S. van [Bayreuth Univ. (Germany). Lab. of Crystallography; Dinnebier, R.; Sofin, M.; Jansen, M. [Max-Planck-Institute for Solid State Research, Stuttgart (Germany)

    2007-02-15

    Na{sub x}CuO{sub 2} (x{approx_equal}1.6) has been synthesized for different compositions x, resulting in both commensurate and incommensurate composite crystals. The crystal structures are reported for two incommensurate compounds (x=1.58 and 1.62) determined by Rietveld refinements against X-ray powder diffraction data. The incommensurate compounds and commensurate Na{sub 8}Cu{sub 5}O{sub 10} (x=1.6) are found to possess similar structures, with valence fluctuations of Cu{sup 2+}/Cu{sup 3+} as the origin of the modulations of the CuO{sub 2} subsystems; the displacive modulations of Na being defined by the closest Na-O contacts between the subsystems. A comparison of the structure models obtained from single-crystal X-ray diffraction, synchrotron-radiation X-ray powder diffraction and Xray powder diffraction with Cu K{alpha}{sub 1} radiation indicates that single-crystal X-ray diffraction is by far the most accurate method, while powder diffraction with radiation from an Xray tube provides the least accurate structure model. (orig.)

  16. Structures of Incommensurate and Commensurate Composite Crystals NaxCuO2(x=1.58, 1.6, 1.62)

    Energy Technology Data Exchange (ETDEWEB)

    van Smaalen,S.; Dinnebier, R.; Sofin, M.; Jansen, M.

    2007-01-01

    NaxCuO2 (x {approx_equal} 1.6) has been synthesized for different compositions x, resulting in both commensurate and incommensurate composite crystals. The crystal structures are reported for two incommensurate compounds (x = 1.58 and 1.62) determined by Rietveld refinements against X-ray powder diffraction data. The incommensurate compounds and commensurate Na{sub 8}Cu{sub 5}O{sub 10} (x = 1.6) are found to possess similar structures, with valence fluctuations of Cu{sup 2+}/Cu{sup 3+} as the origin of the modulations of the CuO{sub 2} subsystems; the displacive modulations of Na being defined by the closest Na-O contacts between the subsystems. A comparison of the structure models obtained from single-crystal X-ray diffraction, synchrotron-radiation X-ray powder diffraction and X-ray powder diffraction with Cu K{sub 1} radiation indicates that single-crystal X-ray diffraction is by far the most accurate method, while powder diffraction with radiation from an X-ray tube provides the least accurate structure model.

  17. Preparation of Cu-based Bulk Metallic Glass Matrix Composites

    Institute of Scientific and Technical Information of China (English)

    Yufeng SUN; Yuren WANG; Bingchen WEI; Weihuo LI

    2006-01-01

    Cu47Ti34Zr11Ni8 bulk metallic glass (BMG) matrix composites containing in situ formed TiC particles and δ-TiCu dendrite phase were developed by copper mold cast. The thermal stability and microstructure of the composites are investigated. Room temperature compression tests reveal that the composite samples exhibit higher fracture strength and distinct plastic strain of 0.2%~0.5%, comparing with that of the corresponding Cu47Ti34Zr11 Ni8 monolithic BMG.

  18. Structural and H2 sorption properties of MgH2-10 wt%ZrCrM (M = Cu, Ni) nano-composites

    Science.gov (United States)

    Agarwal, Shivani; Aurora, Annalisa; Jain, Ankur; Montone, Amelia

    2011-11-01

    Magnesium and its hydride MgH2 are widely regarded as promising candidates for hydrogen storage materials due to its benefits of high gravimetric and volumetric capacity, excellent reversibility, abundance in the earth and a low cost. Much attention has been paid to improve its absorption/desorption kinetics, trying to make it useful for practical applications. To make composite of MgH2 with other hydrogen storage compounds is an effective method to improve the hydrogen storage properties. In this study nano-composite of MgH2 with ZrCrCu alloy was prepared using high energy ball-milling for 5 h under Ar atmosphere. Microstructure and morphology of the composites were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM). XRD patterns show that no alloy formation between MgH2 and elements of the alloys takes place during milling. Different morphology of the powders as-milled and after cycling was observed by SEM. Pressure-composition isotherms of these composites have been obtained in the pressure range 0.1-10 bar at 275 and 300 °C. The absorption/desorption kinetics data have been analyzed using pressure 0.1-5.0 bar at 275 and 300 °C to understand the mechanism of the hydriding/dehydriding reaction processes. A comparison of these results has been attempted with our previous published results of MgH2-10 wt%ZrCrNi in order to find the better composite for storage applications. It is observed by DSC curves that the onset temperature of hydrogen desorption is decreased for MgH2-10%ZrCrNi in comparison to MgH2 which further decreased for MgH2-10%ZrCrCu. However, little loss in hydrogen absorption/desorption capacity is also observed for ZrCrCu composite in comparison to that of ZrCrNi composite.

  19. Transport properties of a Josephson-coupled network in a superconductive ceramic of YBa{sub 2}Cu{sub 4}O{sub 8}

    Energy Technology Data Exchange (ETDEWEB)

    Deguchi, H; Nawa, D; Hashimoto, Y; Mito, M; Takagi, S [Faculty of Engineering, Kyushu Institute of Technology, Kitakyushu 804-8550 (Japan); Hagiwara, M [Faculty of Engineering and Design, Kyoto Institute of Technology, Kyoto 606-8585 (Japan); Koyama, K, E-mail: deguchi@tobata.isc.kyutech.ac.j [Faculty of Integrated Arts and Sciences, University of Tokushima, Tokushima 770-8502 (Japan)

    2009-03-01

    Ceramic YBa{sub 2}Cu{sub 4}O{sub 8} samples composed of sub-micron size grains are considered as random Josephson-coupled networks of 0 and pi junctions, and they show successive phase transitions. The first transition occurs inside each grain at T{sub c1} and the second transition occurs among the grains at T{sub c2} (> T{sub c1}), where a negative divergence of nonlinear susceptibility is found. This critical phenomenon at T{sub c2} suggests the onset of the chiral-glass phase, as predicted by Kawamura and Li. We measured the temperature dependencies of the current-voltage characteristics of the samples and derived the linear and nonlinear resistivities. With decreases in temperature, linear resistivity decreased monotonously and remained at a finite value at temperatures less than T{sub c2}, while nonlinear resistivity diminished continuously for temperatures moving towards T{sub c2}. These results are consistent with the theoretical predictions.

  20. Microstructural and magneto-transport properties of Bi{sub 1.6}Pb{sub 0.4}Sr{sub 2}Ca{sub 1−x}Gd{sub x}Cu{sub 2}O{sub 8+δ} superconducting ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Boudjadja, Y., E-mail: yazid.bouj@Gmail.com [NDT Laboratory, Faculty of Science and Technology, Jijel University, Jijel 18000 (Algeria); Amira, A.; Mahamdioua, N.; Saoudel, A. [NDT Laboratory, Faculty of Science and Technology, Jijel University, Jijel 18000 (Algeria); Menassel, S. [MSAR Unit, Physics Department, Constantine 1 University, Constantine 25017 (Algeria); Varilci, A.; Terzioglu, C.; Altintas, S.P. [Department of Physics, Faculty of Arts and Sciences, AIB University, Bolu 14280 (Turkey)

    2017-01-15

    This study aims to investigate the effect of Gd doping on the phase formation, microstructure, transport and magnetic properties of the Bi(Pb)-2212 system. A series of superconducting bulks with a nominal composition of Bi{sub 1.6}Pb{sub 0.4}Sr{sub 2}Ca{sub 1−x}Gd{sub x}Cu{sub 2}O{sub 8+δ} with x=0, 0.05, 0.10 and 0.15 are synthesized by the solid state synthesis route. The formed samples are characterized by means of X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectrometer (EDS), electrical transport and magnetic measurements. The experiment results reveal that all the samples doped are composed of Bi-2212 phase and traces of Bi-2201 secondary phase when compared to the undoped sample. The refinement of cell parameters shows that the doping reduces the cell volume of the samples. The texture degree decreases with doping while the degree of orthorhombicity increases. Quantitative EDS analysis confirms that Gd atoms are successfully introduced into crystalline structure. The SEM micrographs show randomly distributed grains with a flake-like shape. The highest value of onset critical transition temperatures is obtained for x=0.10 and is about 90.22 K, which correlates well with the observed slope of resistivity and the hole concentration of the CuO{sub 2} layers. Magnetic hysteresis loops suggest that the diamagnetism, remanant magnetization and lower critical field are better for x=0.10. Based on the enhancements of both grain boundary weak-links and flux pinning centers, improvement of the critical current densities and flux pinning density is obtained with this kind of doping.

  1. Cu2O/累托石纳米复合材料处理模拟染料废水试验%Treating dye wastewater by nano-composites with Cu2O/rectorite

    Institute of Scientific and Technical Information of China (English)

    段颖姗; 陈云; 张文蓉; 陈金毅; 蔡忠丽; 孙家寿

    2011-01-01

    The Cu2O/rectorite composite which took the rectoite as the carrier was prepared by liquid phase synthesis and was characterized by means of SEM and XRD. The adsorption performances and photocatalysis properties of the composite was based on the photocatalytic degradation of simulate xylenol orange dye wastewater. The results indicate that the photodegradation efficiency of rectorite / CU2O is 81. 56% when stirring time is 40 min,initial pH of 13;simulate xylenol orange dye wastewater is 20-30 mg/L and the addtion of composite is 5 g/L. The photodegradation rate still reaches 70% even after repeated use for three times.%以累托石为载体,用液相合成法制备和表征了Cu2 O/累托石纳米复合材料,并以吸附降解二甲酚橙的效果,探讨复合材料的吸附及光催化氧化性能.试验结果表明:当模拟二甲酚橙染料废水的初始质量浓度为20~30 mg/L,初始pH值为13,搅拌时间为40 min,纳米累托石/Cu2O复合材料的投加量为5 g/L时,对模拟二甲酚橙染料废水中二甲酚橙的去除率可达81.56%.三次重复使用后的复合材料对二甲酚橙的去除率仍可达70%.

  2. The Influence of Al2O3 Powder Morphology on the Properties of Cu-Al2O3 Composites Designed for Functionally Graded Materials (FGM)

    Science.gov (United States)

    Strojny-Nędza, Agata; Pietrzak, Katarzyna; Węglewski, Witold

    2016-08-01

    In order to meet the requirements of an increased efficiency applying to modern devices and in more general terms science and technology, it is necessary to develop new materials. Combining various types of materials (such as metals and ceramics) and developing composite materials seem to be suitable solutions. One of the most interesting materials includes Cu-Al2O3 composite and gradient materials (FGMs). Due to their potential properties, copper-alumina composites could be used in aerospace industry as rocket thrusters and components in aircraft engines. The main challenge posed by copper matrix composites reinforced by aluminum oxide particles is obtaining the uniform structure with no residual porosity (existing within the area of the ceramic phase). In the present paper, Cu-Al2O3 composites (also in a gradient form) with 1, 3, and 5 vol.% of aluminum oxide were fabricated by the hot pressing and spark plasma sintering methods. Two forms of aluminum oxide (αAl2O3 powder and electrocorundum) were used as a reinforcement. Microstructural investigations revealed that near fully dense materials with low porosity and a clear interface between the metal matrix and ceramics were obtained in the case of the SPS method. In this paper, the properties (mechanical, thermal, and tribological) of composite materials were also collected and compared. Technological tests were preceded by finite element method analyses of thermal stresses generated in the gradient structure, and additionally, the role of porosity in the formation process of composite properties was modeled. Based on the said modeling, technological conditions for obtaining FGMs were proposed.

  3. Fabrication of low adhesive superhydrophobic surfaces using nano Cu/Al{sub 2}O{sub 3} Ni–Cr composited electro-brush plating

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Tianchi [College of Mechanical & Electrical Engineering, Xu Zhou 221116 (China); Ge, Shirong [College of Mechanical & Electrical Engineering, Xu Zhou 221116 (China); College of Materials Science and Engineering, China University of Mining and Technology, Xu Zhou 221116 (China); Liu, Hongtao, E-mail: liuht100@126.com [College of Materials Science and Engineering, China University of Mining and Technology, Xu Zhou 221116 (China); Sun, Qinghe; Zhu, Wei; Yan, Wei; Qi, Jianwei [College of Materials Science and Engineering, China University of Mining and Technology, Xu Zhou 221116 (China)

    2015-11-30

    Highlights: • We fabricate a low adhesive superhydrophobic nano Cu/Al{sub 2}O{sub 3} composited Ni–Cr coating via brush plating. • We investigate the influence of process parameters on hydrophobic properties process. • We discuss the formation mechanism of structures on the surface and using water rebound height to explain the low adhesive force mechanism. - Abstract: Superhydrophobic nano Cu/Al{sub 2}O{sub 3} Ni–Cr composited coating with a low adhesive force was deposited onto the Q345 carbon steel via electro-brush plating. Surface morphologies of nano Cu/Al{sub 2}O{sub 3} Ni–Cr composited coating were investigated by scanning electron microscope (SEM). Chemical compositions were characterized by energy dispersive spectroscopy (EDS). First of all, by adjusting different process parameters such as working voltage, relative velocity, Cu particles concentration and plating time, we obtain the most optimal parameters: working voltage is 15 V, relative velocity is 4.8 m/min, Cu particles concentration is 5 g/L and plating time is 60 s. Under the best process parameters, the water contact angle reaches to 156° and a sliding angle is less than 2° on the nano Cu/Al{sub 2}O{sub 3} Ni–Cr coating. Then the mechanism of the superhydrophobic and low adhesion characteristic of this surface were explained by Cassie's model. Low adhesive force can be characterized by max rebound height of water droplet. As a result, to achieve low adhesive surface it is necessary to decrease the fraction of the solid/liquid interface under the water droplet. Finally the coating was proved to have an excellent self-cleaning performance.

  4. 中子辐照对GdBa2Cu3O7-δ单畴超导性能的影响%Effects of Neutron Irradiation on Superconducting Properties of GdBa2Cu3O7-δ Single Domain Superconductor

    Institute of Scientific and Technical Information of China (English)

    张红; 李广; 周桃飞; 刘勇; 李晓光; 陈羽

    2007-01-01

    研究了中子辐照对GdBa2Cu3O7-δ单畴超导性能的影响,使用的辐照剂量为1015 n/cm2.通过高分辨电镜观察发现中子辐照产生球形的缺陷和小的点缺陷,这些球形缺陷的尺寸在4~7 nm,与高温超导相干长度相当,并且在退火过程中稳定存在,而小的点缺陷在退火过程中消失.磁测量结果显示中子辐照使样品的超导电性严重退化,临界电流密度下降并且鱼尾峰效应几乎消失.然而对辐照的样品退火处理后,其超导电性明显改善,临界电流密度显著提高并超过了未经辐照的样品,鱼尾峰也向高场移动.这些结果表明中子辐照和退火处理使GdBa2Cu3O7-δ单畴样品中引入了有效的磁通钉扎中心(即球型的缺陷)从而导致其临界电流密度大幅提高.%The effects of neutron irradiation with a fluence of 1015 n/cm2 on the superconducting properties of GdBa2Cu3O7-δ single domain sample were studied. The point and cascade defects produced by the neutron irradiation were observed by high-resolution transmission electron microscopy. The cascade defects were found to have the sizes of about 4-7 nm which is comparable to the coherence lengths of high temperature superconductors. The point defects disappear while the cascades still exist through thermal annealing.The temperature dependence of magnetization for the magnetic field parallel to the crystallographic c axis shows that the neutron irradiation leads to a dramatic degradation of superconductivity for the as-irradiated sample, a decrease of critical current density (Jc), and the weakening of the fishtail effect in the Jc versus magnetic induction B curve. However, for the as-irradiated sample annealed in the flowing oxygen atmosphere, it shows that Jc under high magnetic fields is greatly enhanced, the fishtail shifts towards higher magnetic fields, and its superconductivity is partially recovered as well due to the remaining effective pinning centers of the cascades

  5. Isothermal sintering, microstructure and superconducting properties of Y{sub 1}Ba{sub 2}Cu{sub 3}O{sub 7-x} compound

    Energy Technology Data Exchange (ETDEWEB)

    Viswanath, R.N.; Ramasmay, S. [Madras Univ. (India). Dept. of Nuclear Physics; Schaper, W.; Gehrke, K. [Univ., of Gottingen, (Germany). Inst. for Metal Physics; Balachandran, U. [Argonne National Lab., IL (United States)

    1994-03-01

    Polycrystalline Y{sub 1}Ba{sub 2}Cu{sub 3}O{sub 7{minus}x} was prepared by the solid state reaction method and characterized by x-ray powder diffraction method, Meissner effect, resistivity by four probe method and iodometric titrations. The material was processed at 930C and isothermal sintering behavior up to 96 was studied using positron lifetime, x-ray powder diffraction (SEM), four probe method for resistivity and critical current vs magnetic field and differential thermal analysis (DTA). Two types of grain morphology are, observed by SEM, one below 36 and one above 36 sintering. DTA show one peak around 954C, above 36 sintering. Positron lifetime results reveal that the lifetime values and {tau}{sub 1} and {tau}{sub 2} arise from positron trapping in strained/deformed regions and-microvoids formed in the triple defect junctions (TDJ), respectively. Size of defect responsible for the pinning centers is estimated from positron lifetime data. Reasons for the lesser value of transport J{sub c} (24.72 A/cm{sup 2}), obtained in the compound sintered at 930C are explained. Nature of defects related to the resistivity component in the compound is also discussed.

  6. Magnetically separable CuFe2O4/AgBr composite photocatalysts: Preparation, characterization, photocatalytic activity and photocatalytic mechanism under visible light

    Science.gov (United States)

    Zhao, Yalei; Lin, Cuiping; Bi, Huijie; Liu, Yonggang; Yan, Qishe

    2017-01-01

    The CuFe2O4 and CuFe2O4/AgBr composites with different CuFe2O4 contents were prepared by a facile sol-gel and hydrothermal method, respectively. The as-synthesized photocatalysts were characterized by means of powder X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), and UV-vis diffuse reflectance spectrum (UV-vis DRS). Their magnetic properties, photocatalytic degradation activities on methyl orange (MO) and tetracycline hydrochloride (TC) solution and photocatalytic mechanism were investigated in detail. The results revealed that the CuFe2O4/AgBr composites exhibited significantly higher photocatalytic activities than the pure CuFe2O4. The enhanced photocatalytic activity could be attributed to the matched band structure of two components and more effective charge transportation and separations. In addition, the quenching investigation of different scavengers demonstrated that h+, rad OH, rad O2- reactive species played different roles in the decolorization of MO and degradation of TC.

  7. 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.).

  8. Fracture behaviour and its relation to critical current of silver-sheathed Ba2YCu3O(7-x) superconducting composite wires and tapes

    Science.gov (United States)

    Ochiai, Shojiro; Hayashi, Kenji; Osamura, Kozo

    1990-08-01

    Silver-sheathed Ba2YCu3O(7-x) superconducting composite wires and tapes were prepared by rolling, drawing, swaging and pressing methods. The fracture behavior and its influence on critical current at 0T at 77 K of the Ba2YCu3O(7-x) were investigated. The oxide was found to show multiple fracture under applied tensile stress, and the critical current density and tensile strength of the oxide in the rolled, swaged and pressed samples were higher than those in the drawn samples. When the working amount was high, the current density and the strength of the oxide were found to become high. Within the present conditions, there was a correlation between critical current density and cracking stress: the higher the cracking stress, the higher the critical current density became. The cracking stress of the present oxide was determined to be 50 MPa at most, being far lower than that of the Nb3Sn compound (800 to 2000 MPa). The critical current density of the rolled, swaged and pressed samples was reduced rapidly when exerted stress on the oxide exceeded the cracking stress, while the reduction in the drawn samples occurred gradually. A strong dependence of the critical current, as a function of applied stress and cracking stress of the oxide, on the measured portion due to scatter in the size of defects contained in the oxide, was found.

  9. Preparation and characterization of (CuInSe{sub 2}){sub 1-x}(CoSe){sub x} alloys in the composition range 0{<=}x{<=}2/3

    Energy Technology Data Exchange (ETDEWEB)

    Grima-Gallardo, P.; Munoz, M.; Ruiz, J.; Power, C.; Gonzalez, J. [Centro de Estudios en Semiconductores (C.E.S.), Dpto. Fisica, Fac. Ciencias, Universidad de Los Andes, La Hechicera, Merida (Venezuela); LeGodec, Y.; Munsch, P.; Itie, J.P. [Laboratoire de Physique des Milieux Condenses, Universite Pierre et Marie Curie, Paris VI, Paris (France); Briceno, V. [Facultad Experimental de Ciencias y Tecnologia (FACYT), Dpto. Fisica, Universidad de Carabobo, Valencia (Venezuela); Briceno, J.M. [Laboratorio de Analisis Quimico y Estructural (LAQUEM), Dpto. Fisica, Fac. Ciencias, La Hechicera, Merida (Venezuela)

    2004-07-01

    Polycrystalline samples of (CuInSe{sub 2}){sub 1-x}(CoSe){sub x} alloys were prepared by the normal melt and anneal technique in the composition range 02/3. The obtained ingots were characterized by scanning electron microscopy, X-ray diffraction and differential thermal analysis techniques. A sample with x=2/3 (prepared a posteriori) was also studied by the Raman shift technique. The results showed a complex behavior of the phase diagram. The phase ({alpha}) with chalcopyrite structure exists in a narrow interval 0composition range; then, for 0.1Cu, Co and In) at random. For 0.252/3, another chalcopyrite-like phase ({alpha}{sup ''}) was observed together with traces of the {gamma} phase. The sequence of phase transformations in the studied composition range seems to be {alpha} {yields} {alpha}' {yields} {alpha}'+{gamma} {yields} {alpha}{sup ''}+{gamma}. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  10. YBa2Cu3O7 thin films on nanocrystalline diamond films for HTSC bolometer

    Science.gov (United States)

    Cui, G.; Beetz, C. P., Jr.; Boerstler, R.; Steinbeck, J.

    1993-03-01

    Superconducting YBa2Cu3O(7-x) films on nanocrystalline diamond thin films have been fabricated. A composite buffer layer system consisting of diamond/Si3N4/YSZ/YBCO was explored for this purpose. The as-deposited YBCO films were superconducting with Tc of about 84 K and a relatively narrow transition width of about 8 K. SEM cross sections of the films showed very sharp interfaces between diamond/Si3N4 and between Si3N4/YSZ. The deposited YBCO film had a surface roughness of about 1000 A, which is suitable for high-temperature superconductive (HTSC) bolometer fabrication. It was also found that preannealing of the nanocrystalline diamond thin films at high temperature was very important for obtaining high-quality YBCO films.

  11. Solute segregation in an Al2O3f/Al-4.5Cu alloy composite during solidification at different cooling rates

    Institute of Scientific and Technical Information of China (English)

    LIU Zheng; JING Qingxiu

    2005-01-01

    An Al2O3f/Al-4.5Cu composite was made by squeeze casting. The solute segregation in the composite at different cooling rates was studied. The results indicate that the primary crystal of Al-4.5Cu alloy nucleates and grows in the interstice between fibers. The fiber surface cannot serve as site for the heterogeneous nucleation of α primary dendrite. There exists an increasing Cu concentration gradient from the center of the interstice between fibers to the interface or the grain boundaries. There are the eutectic phases around the fibers. The solute segregation in the matrix increases with the cooling rate rising. The amount of eutectic phases followed by imbalance crystalline can be numerically calculated with Clyne-Kurz formula.

  12. 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.

  13. Normal zone propagation in adiabatic superconducting magnets: Pt. 1; Normal zone propagation velocity in superconducting composites

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Z.P.; Iwasa, Y. (Massachusetts Inst. of Tech., Cambridge, MA (United States). Francis Bitter National Magnet Lab. Massachusetts Inst. of Tech., Cambridge, MA (United States). Plasma Fusion Center)

    1991-09-01

    A normal zone propagation model has been developed for superconducting composites under adiabatic conditions. It is based on the Whetstone-Roos model, originally developed for normal zone propagation in adiabatic wires of unclad superconductor. The model takes into account the temperature and magnetic field dependent material properties, for both superconductor and matrix metal. Analytical results agree well with experimental data. (author).

  14. High catalytic activity of magnetic CuFe2O4/graphene oxide composite for the degradation of organic dyes under visible light irradiation

    Science.gov (United States)

    Chen, Peng; Xing, Xiang; Xie, Huifang; Sheng, Qi; Qu, Hongxia

    2016-09-01

    Magnetic CuFe2O4/graphene oxide composite (CuFe2O4/GO) has been synthesized by hydrothermal method and showed excellent visible-light-photocatalytic activity for the degradation of different dyes as Rhodamine B (RhB) and acid orange II (AO7) with no need of H2O2. The Structure and morphology were investigated by XRD, FTIR and TEM and the performance of the catalyst was systematically investigated under various experimental conditions as pH, the dosage of catalyst, dye initial concentration, etc. The dyes degradation on CuFe2O4/GO was also remained in a level in the presence of *OH2- radical scavenger (2-propanol), while it decreased in the presence of *O2- radical scavenger (benzoquinone) and h+ radical scavenger (ammonium oxalate), indicating that *O2- and h+ radicals were responsible for the dye degradation. The magnetic CuFe2O4/GO composite shows potential applications in organic dye water treatment due to its magnetically recyclability and powerful visible-light-photocatalytic activity.

  15. 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.

  16. 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.

  17. Multistable current states in high-temperature superconducting composites

    Science.gov (United States)

    Romanovskii, V. R.

    2016-09-01

    Conditions for current instabilities that arise in high-temperature superconducting composites with essentially nonlinear dependences of the critical current densities and resistivity on the temperature and magnetic induction have been studied. The analysis has been conducted in terms of zero-dimensional models, which has made it possible to formulate general physical mechanisms behind the formation of currents states in superconducting composites according to the external magnetic field induction, cooling conditions, and the properties of the superconductor and cladding. The possible existence of current and temperature stable steps, as well as stable steps of the electric field strength, in the absence of the superconducting-normal transition, has been demonstrated. Reasons for instabilities under multistable current states have been discussed.

  18. 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.).