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Sample records for 2cusub 3osub 7-delta

  1. YBa2Cu3O(7-delta)/Au/Nb sandwich geometry SNS weak links on c-axis oriented YBa2Cu3O(7-delta)

    NASA Technical Reports Server (NTRS)

    Foote, M. C.; Hunt, B. D.; Bajuk, L. J.

    1991-01-01

    Sandwich geometry superconductor/normal metal/superconductor structures have been fabricated on LaAlO3 and cubic zirconia with laser-ablated, c-axis-oriented YBa2Cu3O(7-delta) base electrodes, 100-600 A of Au, and Nb counter electrodes, all formed in situ without breaking vacuum. Junctions range in size from 5 to 50 micron on a side. Four probe I-V measurements at 4.2 K show RnA products as low as 6 x 10 to the -9th sq cm and critical current densities up to 5.2 kA/sq cm. AC Josephson steps were observed with the application of 10-GHz radiation. The temperature dependence of Jc and the observation of the AC Josephson effect suggest that true supercurrents are present and that they do indeed represent the characteristics of the YBa2Cu3O(7-delta)/Au/Nb structure. The best results were obtained when the devices were annealed at about 450 C in O2 for 30 min after Au deposition.

  2. Near-edge study of gold-substituted YBa2Cu3O(7-delta)

    NASA Technical Reports Server (NTRS)

    Ruckman, Mark W.; Hepp, Aloysius F.

    1991-01-01

    The valence of Cu and Au in YBa2Au0.3Cu2.7O7-delta was investigated using x-ray absorption near edge structure (XANES). X-ray and neutron diffraction studies indicate that Au goes on the Cu(1) site and Cu K-edge XANES shows that this has little effect on the oxidation state of the remaining copper. The Au L3 edge develops a white line feature whose position lies between that of trivalent gold oxide and monovalent potassium gold cyanide, and whose height relative to the edge step is smaller than in the two reference compounds. The appearance of the Au L3 edge suggests that fewer Au 3d states are involved in forming the Au-O bond in YBa2Au0.3Cu2.7O7-delta than in trivalent gold oxide.

  3. Near-edge study of gold-substituted YBa2Cu3O(7-delta)

    NASA Technical Reports Server (NTRS)

    Ruckman, Mark W.; Hepp, Aloysius F.

    1991-01-01

    The valence of Cu and Au in YBa2Au0.3Cu2.7O7-delta was investigated using X-ray absorption near edge structure (XANES). X-ray and neutron diffraction studies indicate that Au goes on the Cu(1) site and Cu K-edge XANES shows that this has little effect on the oxidation state of the remaining copper. The Au L3 edge develops a white line feature whose position lies between that of trivalent gold oxide and monovalent potassium gold cyanide, and whose height relative to the edge step is smaller than in the two reference compounds. The appearance of the Au L3 edge suggests that fewer Au 3d states are involved in forming the Au-O bond in YBa2Au0.3Cu2.7O7-delta than in trivalent gold oxide.

  4. Sandwich-Geometry YBa(2)Cu(3)O(7-delta)/Au/Nb SNS Devices

    NASA Technical Reports Server (NTRS)

    Foote, Marc C.; Hunt, Brian D.

    1993-01-01

    Superconductor/normal-conductor/superconductor (SNS) devices in which electronically active layers consist of high-temperature superconductor YBa(2)Cu(3)O(7-delta), normal conductor Au, and conventional superconductor Nb, fabricated in sandwich geometry. Devices and processes by which fabricated are part of continuing effort to develop SNS microbridges for use in superconducting quantum interference devices (SQUIDS's) or as mixers or local oscillators operating at frequencies of hundreds of gigahertz. Results show promise for manufacture of practical devices.

  5. Anisotropy of oxygen tracer diffusion in YBa sub 2 Cu sub 3 O sub 7-. delta. single crystals

    SciTech Connect

    Rothman, S.J.; Routbort, J.L.; Liu, J.-Z.; Downey, J.W.; Thompson, L.J.; Fang, Y.; Shi, D.; Baker, J.E.; Rice, J.P.; Ginsberg, D.M.; Illinois Univ., Urbana, IL . Materials Research Lab.)

    1989-09-01

    The crystal structure of YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} strongly suggests that the diffusion of oxygen in this material will be highly anisotropic, with diffusion in the ab plane being much faster than diffusion parallel to the c axis, and this has been assumed in most analyses of diffusion in YBa{sub 2}Cu{sub 3}O{sub 7-{delta}}. The present data confirm this hypothesis; the diffusion coefficient in the ab plane is several orders of magnitude greater than the diffusion coefficient along the c axis. Some interesting artifacts of the measurement, due to this strong anisotropy, are also revealed. Oxygen exchange in polycrystalline samples of YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} is discussed in terms of these results. 15 refs., 9 figs.

  6. XANES and EXAFS study of Au-substituted YBa2Cu3O(7-delta)

    NASA Technical Reports Server (NTRS)

    Ruckman, Mark W.; Hepp, Aloysius F.

    1990-01-01

    The near-edge structure (XANES) of the Au L3 and Cu K edges of YBa2Au(0.3)Cu(2.7)O(7-delta) was studied. X ray diffraction suggests that Au goes on the Cu(1) site and XANES shows that this has little effect on the oxidation state of the remaining copper. The gold L3 edge develops a white line feature whose position lies between that of trivalent gold oxide (Au2O3) and monovalent potassium gold cyanide (KAu(CN)2) and whose intensity relative to the edge step is smaller than in the two reference compounds. The L3 EXAFS for Au in the superconductor resembles that of Au2O3. However, differences in the envelope of the Fourier filtered component for the first shell suggest that the local structure of the Au in the superconductor is not equivalent to Au2O3.

  7. Shock wave induced changes in superconductivity in YBa2Cu3O(7-delta)

    NASA Astrophysics Data System (ADS)

    Murr, L. E.; Niou, C. S.; Jin, S.; Tiefel, T. H.; James, A. C. W. P.

    1989-10-01

    Shock wave loading produced significant changes in superconductivity in sintered YBa2Cu3O(7-delta) causing a broad transition with Tc (R = 0) around 40 K. The normal-state resistivity increased by 20-50 times with the rho-T curve exhibiting a semiconducting behavior. Comparative thermogravimetric analysis, however, indicated no loss of oxygen in the shock-loaded sample, and X-ray powder diffraction analysis showed no major changes except for slight line broadening. The observed semiconductive behavior and degradation in superconductivity is thus attributed to a rather subtle disturbance in crystal structure, the nature of which is not clearly understood at present. The lack of sufficient recovery in Tc by post-shock oxygen processing at temperatures as high as 750 C and subsequent cooling implies that the atomic-scale disturbance may not necessarily be related to a simple oxygen disorder. Such defects, if controlled properly, may be advantagenously turned into desirable flux-pinning sites for improved critical currents.

  8. Structural chemistry of Au(III)-substituted Ba2YCu3O(7-delta)

    NASA Technical Reports Server (NTRS)

    Hepp, A. F.; Gaier, J. R.; Pouch, J. J.; Hambourger, P. D.

    1988-01-01

    A series of gold-substituted perovskite superconductors Ba2Y(Cu/1-x/Aux)3O(7-delta)(x = 0-0.1) was synthesized. For x = 0.1, there was no change in the a and b lattice parameters (a = 3.826 A and b = 3.889 A), but a 0.06 A c-axis expansion to 11.75 A was observed. Substituted gold was found to be trivalent by X-ray photoelectron spectroscopy. Replacing Cu(1) in the copper oxide chain with a slight reordering of oxygen is consistent with c-axis expansion. The formal charge of the site remains trivalent, while remaining Cu in the chains is reduced to Cu(I), resulting in an oxygen stoichiometry of less than 7. Finally, no large effect on Tc is observed (Tc = 89 K for x = 0.10), in contrast to the effect of a number of other metal ion dopants. These results are discussed relative to the chemistry of Au(III) and to the use of the metal in structures containing gold and ceramic superconductors.

  9. Electronic Structure of TlBa2CaCu2O(7-Delta)

    NASA Technical Reports Server (NTRS)

    Vasquez, R. P.; Novikov, D. L.; Freeman, A. J.; Siegal, M. P.

    1997-01-01

    The core levels of TlBa2CaCu2O(7-delta) (Tl-1212) epitaxial films have been measured with X-ray photoelectron spectroscopy (XPS). The valence electronic structure has been determined using the full-potential linear muffin-tin-orbital band-structure method and measured with XPS. The calculations show that a van Hove singularity (VHS) lies above the Fermi level (E(sub F)) for the stoichiometric compound (delta = 0.5), while for 50% oxygen vacancies in the Tl-O layer (delta = 0.5) E(sub F) is in close proximity to the VHS. Samples annealed in nitrogen (to reduce the hole overdoping by the removal of oxygen) exhibit higher core-level binding energies and a higher T(sub c), consistent with a shift of E(sub F) closer to the VHS. Comparisons are made to the core levels and valence bands of Tl2Ba2CaCu2O(8 + delta)(Tl-2212) and HgBa2CaCu2O)6 + delta) (Hg- 1212). The similarity of the Cu 2p(sub 3/2) spectra for Tl-1212 and Tl-2212 indicates that the number of Tl-O layers has little effect on the Cu-O bonding. However, the Tl-1212 and Hg-1212 Cu 2p(sub 3/2) signals exhibit differences which suggest that the replacement of T(sup 3+) with Hg(sup 2+) results in a decrease in the O 2p right arrow Cu 3d charge-transfer energy and differences in the probabilities of planar vs apical oxygen charge transfer and/or Zhang-Rice singlet-state formation. Differences between the Tl-1212 and the Tl-2212 and Hg-1212 measured valence bands are consistent with the calculated Cu 3d and (Tl,Hg) 6s/5d partial densities of states.

  10. Broken particle-hole symmetry at atomically flat a-axis YBa2Cu3O7-delta interfaces.

    PubMed

    Davidson, Bruce A; Ramazashvili, Revaz; Kos, Simon; Eckstein, James N

    2004-09-01

    We have studied quasiparticle tunneling into atomically flat a-axis films of YBa(2)Cu(3)O(7-delta) and DyBa(2)Cu(3)O(7-delta) through epitaxial CaTiO3 barriers. The junction heterostructures were grown by oxide molecular beam epitaxy and were carefully optimized using in situ monitoring techniques, resulting in unprecedented crystalline perfection of the superconductor-insulator interface. Below T(c), the tunneling conductance shows the evolution of a large unexpected asymmetrical feature near zero-bias. This is evidence that superconducting YBCO crystals, atomically truncated along the lobe direction with a titanate layer, have intrinsically broken particle-hole symmetry over macroscopically large areas. PMID:15447441

  11. Millimeter wave surface resistance of RBa2Cu3O(7-delta) (R=Y,Eu,Dy,Sm,Er) superconductors

    NASA Technical Reports Server (NTRS)

    Miranda, F. A.; Gordon, W. L.; Eck, T. G.; Bhasin, K. B.; Warner, J. D.; Jenkins, K. A.

    1990-01-01

    The measurements are reported of the millimeter wave surface resistance R(sub s) at 58.6 GHz of bulk samples of RBa2Cu3O(7-delta) (R = Y,Eu,Dy,Sm,Er) and of YBa2Cu3O(7-delta) superconducting films, in the temperature range from 20 to 300 K. The bulk samples were prepared by cold pressing the powders of RBa2Cu3O(7-delta) into one in. disks. The powders were prepared by several sinterings in one atmosphere of oxygen at 925 C, with grindings between sinterings, to obtain the superconducting phase. The thin films were deposited on SrTiO3 and LaGaO3 substrates by pulsed laser ablation. Each sample was measured by replacing the end wall of a gold-plated Te sub 013 circular mode copper cavity with the sample and determining the cavity quality factor . From the difference in the Q-factor of the cavity, with and without the sample, the R(sub s) of the sample was determined.

  12. IL-7 splicing variant IL-7{delta}5 induces human breast cancer cell proliferation via activation of PI3K/Akt pathway

    SciTech Connect

    Pan, Deshun; Liu, Bing; Jin, Xiaobao; Zhu, Jiayong

    2012-06-15

    Highlights: Black-Right-Pointing-Pointer This study confirms the role of IL-7{delta}5 in breast cancer cell proliferation. Black-Right-Pointing-Pointer IL-7{delta}5 promotes breast cancer cell proliferation and cell cycle progression. Black-Right-Pointing-Pointer IL-7{delta}5 promotes cell proliferation via activation of PI3K/Akt pathway. -- Abstract: Various tumor cells express interleukin 7 (IL-7) and IL-7 variants. IL-7 has been confirmed to stimulate solid tumor cell proliferation. However, the effect of IL-7 variants on tumor cell proliferation remains unclear. In this study, we evaluated the role of IL-7{delta}5 (an IL-7 variant lacking exon 5) on proliferation and cell cycle progression of human MDA-MB-231 and MCF-7 breast cancer cells. The results showed that IL-7{delta}5 promoted cell proliferation and cell cycle progression from G1 phase to G2/M phase, associated with upregulation of cyclin D1 expression and the downregulation of p27{sup kip1} expression. Mechanistically, we found that IL-7{delta}5 induced the activation of Akt. Inhibition of PI3K/Akt pathway by LY294002 reversed the proliferation and cell cycle progression of MDA-MB-231 and MCF-7 cells induced by IL-7{delta}5. In conclusion, our findings demonstrate that IL-7{delta}5 variant induces human breast cancer cell proliferation and cell cycle progression via activation of PI3K/Akt pathway. Thus, IL-7{delta}5 may be a potential target for human breast cancer therapeutics intervention.

  13. Boson localization and universality in YBa2Cu(3-x)M(x)O(7-delta)

    NASA Technical Reports Server (NTRS)

    Kallio, A.; Apaja, V.; Poykko, S.

    1995-01-01

    We consider a two component mixture of charged fermions on neutralizing background with all sign combinations and arbitrarily small mass ratios. In the two impurity limit for the heavier component we show that the pair forms a bound state for all charge combinations. In the lowest order approximation we derive a closed form expression Veff(r) for the binding potential which has short-range repulsion followed by attraction. In the classical limit, when the mass of embedded particles is large m2 much greater than m, we can calculate from Veff(r) also the cohesive energy E and the bond length R of a metallic crystal such as lithium. The lowest order result is R = 3.1 A, E = -0.9 eV, not entirely different from the experimental result for lithium metal. The same interaction for two holes on a parabolic band with m2 greater than m gives the quantum mechanical bound state which one may interpret as a boson or local pair in the case of high-Te and heavy fermion superconductors. We also show that for compounds of the type YBa2Cu(3 - x)M(x)O(7 - delta) one can understand most of the experimental results for the superconducting and normal states with a single temperature dependent boson breaking function f(T) for each impurity content x governing the decay of bosons into pairing fermions. In the normal state f(T) turns out to be a linear, universal function, independent of the impurity content I and the oxygen content delta. We predict with universality a depression in Tc(x) with slight down bending in agreement with experiment. As a natural consequence of the model the bosons become localized slightly above Tc due to the Wigner crystallization, enhanced with lattice local field minima. The holes remain delocalized with a linearly increasing concentration in the normal state, thus explaining the rising Hall density. The boson localization temperature T(sub BL) shows up as a minimum in the Hall density R(sub ab)(exp -1). We also give explanation for very recently observed

  14. Y{sub x}Ba{sub y}Cu{sub z}O{sub 7-{delta}} solid solutions

    SciTech Connect

    Nipan, G.D.; Kol`tsova, T.N.; Tishchenko, E.A.

    1996-12-01

    Y{sub x}Ba{sub y}Cu{sub z}O{sub 7-{delta}} ceramics forming at isobaric conditions were studied by x-ray diffraction analysis, dynamic magnetic measurements and potentiometric titration. It was established that compositions: 0.8 {le} x {le} 1.2, y=2, z=3; x=1, 1.8 {le} y {le} 2.2, z=3; x=1, y=2, 2.7 {le} z {le} 3.4: are in the homogeneity range of 123. It was found that compositions with nonstoichiometric cation ratios have minimum {Delta}T{sub c}.

  15. Millimeter-wave surface resistance of laser-ablated YBa2Cu3O(7-delta) superconducting films

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

    The millimeter-wave surface resistance of YBa2Cu3O(7-delta) superconducting films was measured in a gold-plated copper host cavity at 58.6 GHz between 25 and 300 K. High-quality laser-ablated films of 1.2-micron thickness were deposited on SrTiO3 and LaGaO3 substrates. Their transition temperatures were 90.0 and 88.9 K, with a surface resistance at 70 K of 82 and 116 milliohms, respectively. These values are better than the values for the gold-plated cavity at the same temperature and frequency.

  16. High magnetic field trapping in monolithic single-grain YBa2Cu3O(7-delta) bulk materials

    NASA Technical Reports Server (NTRS)

    Gao, L.; Xue, Y. Y.; Ramirez, D.; Huang, Z. J.; Meng, R. L.; Chu, C. W.

    1993-01-01

    Results of our study on high magnetic field trapping in unirradiated, high quality monolithic single-grain YBa2Cu3O(7-delta) disks are reported. A record high 4 T trapped field at the surface of the unirradiated disks is observed. However, below 11 K, large flux avalanches caused by thermal instability severely limit the remnant trapped field. Therefore, flux avalanche, rather than Jc x d, dictates the maximum trapped field at low temperatures. To overcome this problem, a strong high temperature superconductor trapped field magnet is proposed. A novel application of the avalanche effect is also mentioned.

  17. Coaxial line configuration for microwave power transmission study of YBa2Cu3O(7-delta) thin films

    NASA Technical Reports Server (NTRS)

    Chorey, C. M.; Miranda, F. A.; Bhasin, K. B.

    1991-01-01

    Microwave transmission measurements through YBa2Cu3O(7-delta) (YBCO) high-transition-temperature superconducting thin films on lanthanum aluminate (LaAlO3) have been performed in a coaxial line at 10 GHz. LaAlO3 substrates were ultrasonically machined into washer-shaped discs, polished, and coated with laser-ablated YBCO. These samples were mounted in a 50-ohm coaxial air line to form a short circuit. The power transmitted through the films as a function of temperature was used to calculate the normal state conductivity and the magnetic penetration depth for the films.

  18. Proximity effect in gold-coated YBa(2)Cu(3)O(7-delta) films studied by scanning tunneling spectroscopy.

    PubMed

    Sharoni, Amos; Asulin, Itay; Koren, Gad; Millo, Oded

    2004-01-01

    Scanning tunneling spectroscopy on gold layers overcoating c-axis YBa(2)Cu(3)O(7-delta) (YBCO) films reveals proximity-induced gap structures. The gap size reduces exponentially with the distance from a-axis facets, indicating that the proximity effect is primarily due to the (100) YBCO facets. The penetration depth of superconductivity into the gold is approximately 30 nm, in good agreement with estimations for the dirty limit. The extrapolated gap at the interface is approximately 15 meV, similar to the value of an s-wave component of the order parameter measured at the YBCO surface in recent point-contact experiments. PMID:14754012

  19. Conductor-backed coplanar waveguide resonators of YBa2Cu3O(7-delta) on LaAlO3

    NASA Technical Reports Server (NTRS)

    Miranda, Felix A.; Bhasin, Kul B.; Kong, Keon-Shik; Itoh, Tatsuo; Stan, Mark A.

    1992-01-01

    Conductor-backed coplanar waveguide (CBCPW) resonators operating at 10.8 GHz have been fabricated from laser ablated and off-axis magnetron sputtered YBa2Cu3O(7-delta) (YBCO) high-temperature superconducting (HTS) thin films on LaAlO3. These resonators were tested in the temperature range from 14 to 92 K. The unloaded quality factor at 77 K of the HTS CBCPW resonators was 3 to 4 times that of a similar gold resonator. To the authors' knowledge, these results represent the first reported measurements of HTS-based CBCPW resonators.

  20. Analysis of fluctuation conductivity of YBa{sub 2}Cu{sub 3}O{sub 7-{delta}}-PrBa{sub 2}Cu{sub 3}O{sub 7-{delta}} superlattices

    SciTech Connect

    Solovjov, A.L.; Dmitriev, V.M.; Habermeier, H.; Trofimov, I.E.

    1997-04-01

    The fluctuation-induced conductivity measured on YBa{sub 2}Cu{sub 3}O{sub 7-{delta}}-PrBa{sub 2}Cu{sub 3}O{sub 7-{delta}} superlattices (SL) is analyzed using various theoretical models describing weak fluctuations in layered superconductors and considering both Aslamazov-Larkin (AL) and Maki-Thompson (MT) terms. From the analysis {xi}{sub c}(0)=1.6{plus_minus}0.1 {Angstrom} and {tau}{sub {phi}}(100 K){approx_equal}3{times}10{sup {minus}13} s in clean limit are derived for the interlayer coherence length and temperature-dependent phase-relaxation time, respectively. Large {tau}{sub {phi}} values and AL-MT crossover revealed for all samples studied are attributed to the two-dimensional electronic state nature of SL above the crossover temperature. Possible mechanisms of charge scattering in high-T{sub c} superconductors are also discussed. {copyright} {ital 1997} {ital The American Physical Society}

  1. The role of interfacial defects in enhancing the critical current density of YBa2Cu3O7-delta coatings

    SciTech Connect

    Foltyn, Stephen R; Wang, Haiyan; Civale, Leonardo; Maiorov, Boris A; Jia, Quanxi

    2009-01-01

    The critical current density (J{sub c}) of YBa{sub 2}Cu{sub 3}0{sub 7-{delta}} (YBCO) films can approach 10 MA/cm{sup 2} at 77 K in self field , but only for very thin films. We have shown previously that strong thickness dependence results if J{sub c} is enhanced near the film-substrate interface. In the present work we investigate interfacial enhancement using laser-deposited YBCO films on NdGaO{sub 3} substrates, and find that we can adjust deposition conditions to switch the enhancement on and off. Interestingly, we find that the 'on' state is accompanied by interfacial misfit dislocations, establishing an unambiguous correlation between enhanced J{sub c} and dislocations at the film-substrate interface.

  2. Epitaxial CeO2 buffer layers for YBa2Cu3O(7-delta) films on sapphire

    NASA Astrophysics Data System (ADS)

    Maul, M.; Schulte, B.; Haeussler, P.; Frank, G.; Steinborn, T.; Fuess, H.; Adrian, H.

    1993-08-01

    The paper reports the successful in situ preparation of thin epitaxial CeO2 buffer layers and YBa2Cu3O(7-delta) (YBCO) films on (1 -1 0 2) Al2O3 substrates by electron beam coevaporation, using an evaporation system (Leybold L560) with four sources. Electron beam sources were used for Y, Ba, and Ce, while Cu was evaporated from a resistively heated tungsten boat. The buffer layers show very smooth surfaces and structural properties close to those of a single crystal. High quality YBCO films grown on these buffer layers have Tc not 88 K or above and j(c) values of 10 exp 6 A/sq cm or greater.

  3. Ten Ghz YBa2Cu3O(7-Delta) Superconducting Ring Resonators on NdGaO3 Substrates

    NASA Technical Reports Server (NTRS)

    To, H. Y.; Valco, G. J.; Bhasin, K. B.

    1993-01-01

    YBa2Cu3O(7-delta) thin films were formed on NdGaO3 substrates by laser ablation. Critical temperatures greater than 89 K and critical current densities exceeding 2 x 10(exp 8) Acm(sub -2) at 77 K were obtained. The microwave performance of films patterned into microstrip ring resonators with gold ground planes was measured. An unloaded quality factor six times larger than that of a gold resonator of identical geometry was achieved. The unloaded quality factor decreased below 70 K for both the superconducting and gold resonators due to increasing dielectric losses in the substrate. The temperature dependence of the loss tangent of NdGaO3 was extracted from the measurements.

  4. Magnetic hysteresis of p(+) and He-3(2+) irradiated melt-textured YBa2Cu3O(7-delta)

    NASA Technical Reports Server (NTRS)

    Song, S. N.; Liu, J.; Chen, I. G.; Weinstein, Roy

    1992-01-01

    We have measured the magnetic hysteresis loops and temperature dependent trapped fields in melt-textured YBa2Cu3O(7-delta) samples before and after p(+) and He-3(2+) irradiation using a Hall effect magnetometer (HEM) as well as a commercial vibrating sample magnetometer (VSM). For proper He-3(2+) fluence, the critical current density may be enhanced by a factor of 10. Calculations based on various critical state models show that before the irradiation, the hysteresis loops can be well accounted for by a critical current density of a modified power law field dependence. After the irradiation, the best fit has been achieved by using an exponential form. Jc and its field dependence deduced from HEM hysteresis loops are in good agreement with those deduced from the VSM loops, suggesting that the Hall effect magnetometer can be conveniently used to characterize bulk high Tc oxide superconductors.

  5. Large-area YBa2Cu3O(7-delta) thin films on sapphire for microwave applications

    NASA Technical Reports Server (NTRS)

    Cole, B. F.; Liang, G.-C.; Newman, N.; Char, K.; Zaharchuk, G.; Martens, J. S.

    1992-01-01

    We have deposited YBa2Cu3O(7-delta) (YBCO) films with low microwave surface resistance (Rs) on 5-cm-diam, oxide-buffered sapphire substrates by planar magnetron sputtering. MgO buffer layers are used on M-plane (1 0 -1 0) sapphire, and R-plane (1 -1 0 2) sapphire is buffered by CeO2. Rs values of 450-620 microhms at 77 K and 10 GHz were measured across an entire 5-cm diam YBCO film on M-plane sapphire. For YBCO on R-plane sapphire, Rs values at 77 K and 10 GHz were 950 microohms for a 5-cm-diam wafer and 700 microohms for 1 x 1 sq cm samples.

  6. Studies of iron impurities in YxPr1-xBa2Cu3O7-delta

    NASA Technical Reports Server (NTRS)

    Swartzendruber, L. J.; Bennett, L. H.; Ritter, J.; Rubinstein, M.; Harford, M. Z.

    1990-01-01

    Pr is the only rare earth which, when substituted for Y in YBa2Cu3O7, significantly alters the superconducting transition temperature T(sub c) without changing the crystal structure. For YxPr1-xBa2Cu3O7-delta with delta approx. equal to 0, T(sub c) is reduced rapidly as x is increased, reaching zero for x about 0.5. For x above 0.5 the compound is antiferromagnetic with a Neel temperature that increases with increasing x, rising to above room temperature for x near 1. A similar behavior is observed when the oxygen deficit delta is increased from zero to 1 with x=0. For the case of Pr substitution, the drop in T(sub c) is believed due to magnetic interactions. For the case of varying delta with x=0, the drop can be attributed to a combination of magnetic interactions, band filling, and changes in crystal structure. To study these effects, the Mossbauer effect of 57 Fe atoms substituted for the Cu atoms has been observed as a function of delta, x, and temperature. The observed spectra are all well described by a two quadrupole-split pairs, a central singlet, and a six-line magnetic hyperfine field pattern. For several Pr compositions both delta and temperature were varied, and the results support the hypothesis that a magnetic interaction exists between the Fe in the Cu lattice and the substitutional Pr atoms.

  7. Elucidation of the mechanism in fluorine-free prepared YBa2Cu3O(7-delta) coatings.

    PubMed

    Vermeir, Pieter; Cardinael, Iwein; Schaubroeck, Joseph; Verbeken, Kim; Bäcker, Michael; Lommens, Petra; Knaepen, Werner; D'haen, Jan; De Buysser, Klaartje; Van Driessche, Isabel

    2010-05-17

    In this work, the reaction mechanism used in the preparation of fluorine-free superconducting YBa(2)Cu(3)O(7-delta) (YBCO) was investigated. To determine which precursor interactions are dominant, a comprehensive thermal analysis (thermogravimetric analysis-differential thermal analysis) study was performed. The results suggest that a three step reaction mechanism, with a predominant role for BaCO(3), is responsible for the conversion of the initial state to the superconducting phase. In the presence of CuO, the decarboxylation of BaCO(3) is kinetically favored with the formation of BaCuO(2) as a result. BaCuO(2) reacts with the remaining CuO to form a liquid which ultimately reacts with Y(2)O(3) in a last step to form YBCO. High temperature X-ray diffraction experiments confirm that these results are applicable for thin film synthesis prepared from an aqueous fluorine-free sol-gel precursor. PMID:20405962

  8. Electrical transport across grain boundaries in bicrystals of YBa sub 2 Cu sub 3 O sub 7. delta

    SciTech Connect

    Larbalestier, D.C.; Babcock, S.E.; Cai, X.Y.; Field, M.B.; Heinig, N.F.; Williams, L.K.; Zhang, N. . Applied Superconductivity Center); Gao, Y.; Merkle, K.L. ); Kaiser, D.L. , Gaithersburg, MD . Ceramics Div.)

    1991-01-01

    The superconducting properties of about 20 bulk-scale flux-grown bicrystals of YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} have been measured in order to deduce the nature of the coupling across their grain boundaries. Bicrystals with types of misorientation relationship were studies: (1) {theta} (001) (C-type) and (2) 90{degrees} (010) plus an additional rotation about the a{sub I} {vert bar} c{sub II} axis (P-type). A general trend for a transition from flux pinning (FP) to Josephson Junction (JJ) to resistive (R) behavior was observed as the misorientation angle increased. However, FP character was observed well into the high-angle regime, in particular, for P-type bicrystals, and JJ behavior was observed at as low as 10{degrees} (001). The J{sub ct} values of two bicrystals were increased by a second oxygen anneal. In one case (28{degrees} (001) boundary), extended oxygenation produced a change from JJ to mixed JJ/FP behavior, markedly raising the transport critical current density (J{sub ct}) at all fields. HRTEM has been performed on two of the same bicrystals which were electromagnetically characterized. A thin second phase layer unobservable by conventional TEM was observed in a resistive boundary, whereas no such phase was detected at a JJ boundary. We conclude that the character of the boundary cannot be predicted either from its misorientation angle or the magnitude of its J{sub c}. 10 refs., 6 figs., 1 tab.

  9. Demonstration of Y1Ba2Cu3O(7-delta) and complementary metal-oxide-semiconductor device fabrication on the same sapphire substrate

    NASA Technical Reports Server (NTRS)

    Burns, M. J.; De La Houssaye, P. R.; Russell, S. D.; Garcia, G. A.; Clayton, S. R.; Ruby, W. S.; Lee, L. P.

    1993-01-01

    We report the first fabrication of active semiconductor and high-temperature superconducting devices on the same substrate. Test structures of complementary MOS transistors were fabricated on the same sapphire substrate as test structures of Y1Ba2Cu3O(7-delta) flux-flow transistors, and separately, Y1Ba2Cu3O(7-delta) superconducting quantum interference devices utilizing both biepitaxial and step-edge Josephson junctions. Both semiconductor and superconductor devices were operated at 77 K. The cofabrication of devices using these disparate yet complementary electronic technologies on the same substrate opens the door for the fabrication of true semiconductive/superconductive hybrid integrated circuits capable of exploiting the best features of each of these technologies.

  10. The effect of ferroelastic deformations in the parent phase on the superconducting transition temperature of YBa{sub 2}Cu{sub 3}O{sub 7-{delta}}

    SciTech Connect

    Gufan, Yu.M.

    1995-03-01

    High values of superconducting transition temperature in oxide superconductors are hypothetically attributed to the d-pairing of charge carriers in the Bose condensate. The order parameter of the superconducting state forms the basis for the same representation of the crystallographic symmetry group of the parent phase which is used to transform those components of the order parameter, which describe the spontaneous deformation of the parent phase and form a real crystal. The layering of the crystal is assumed to be an unessential factor, although it may govern the type of pairing in YBa{sub 2}Cu{sub 3}O{sub 7-{delta}}. This hypothesis is supported by the model calculations which qualitatively agree with the experimental data on the temperatures of phase transitions in YBa{sub 2}Cu{sub 3}O{sub 7-{delta}}-based solid solutions. 31 refs., 3 figs.

  11. Studies of microstructure/critical current density relationships for grain boundaries in YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} bicrystals

    SciTech Connect

    Babcock, S.E.; Cai, Xue-Yu; Larbalestier, D.C.; Shin, D.H.; Zhang, Na; Gao, Yufei; Merkle, K.L.; Kaiser, D.L.; Zhang, Hong

    1992-11-01

    Results of coupled electromagnetic and microstructural studies of bicrystalline YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} specimens are described from a microstructural perspective. High-spatial-resolution transmission electron microscopy techniques (imaging and energy dispersive x-ray microanalysis) are used to probe the structure and composition of the grain boundaries. All of the boundaries studied possess microstructural features that are consistent with their specific electromagnetic character.

  12. Photoemission studies of Zn, Co, and Gd substituted YBa{sub 2}Cu{sub 3}O{sub 7-{delta}}

    SciTech Connect

    Gu, Chun; Veal, B.W.; Liu, R.

    1993-06-01

    Zn and Co substitute for Cu in YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} at the plane and chain sites, respectively. We report a high resolution angle-resolved photoemission study on Zn and Co substituted YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} single crystals to determine the effects on electronic structure. The valence states near E{sub F} along {Gamma}-S are virtually unaffected by the substitutions for samples that are superconducting. However, the spectral weight near E{sub F} disappears for a higher Co-doped, nonsuperconducting crystal. Results are compared with earlier studies on pure YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} with controlled oxygen stoichiometry. Measurement on Gd-123 crystals with reduced oxygen stoichiometries show gradual reduction of spectral weight for a band along {Gamma}-Y(X), in contrast to the results for the bands along {Gamma}-S. The differences are probably due to a different admix of Cu-O chain and plane characters in these bands. We also measured Gd 4f resonance spectra which exhibit complex structure, indicating the presence of Gd atoms in chemically inequivalent (probably bulk and near surface) sites.

  13. The high temperature superconductor YBa(2)Cu(3)O(7-delta): Symmetry of the order parameter, and gradiometers for biomagnetic applications

    NASA Astrophysics Data System (ADS)

    Kouznetsov, Konstantin Alexander

    The cuprate YBa2Cu3O7-delta is the material that drives the majority of the technological applications of high transition temperature (Tc) superconductors, particularly in the area of superconducting electronics. Despite the widespread use of high-Tc superconducting materials in a variety of applications, the nature of the superconducting state in these materials remains unknown since their discovery more than a decade ago. Many properties of the high-Tc superconductors are determined by their order parameter, which is a wavefunction describing the superconducting condensate. The symmetry of the order parameter in cuprates has been the subject of intensive investigation, leading to conflicting sets of results. Some experiments supported conventional, s-wave symmetry of the order parameter, while others indicated an unconventional, d-wave symmetry. The first part of this thesis is an experimental study of the symmetry of the order parameter in YBa2Cu3O7-delta . A new class of phase sensitive experiments is described that involve Josephson tunneling along the c-axis of twinned crystals of YBa2Cu 3O7-delta. These experiments showed that an s-wave component must reverse sign across the twin boundary, providing direct evidence for a mixed, s+d symmetry of the order parameter in YBa2Cu3O7-delta, and thereby reconciling two conflicting sets of previous findings and establishing the dominant d-wave pairing symmetry. The second part of the thesis focuses on practical applications of YBa 2Cu3O7-delta in superconducting electronics. We introduce a novel Superconducting QUantum. Interference Device (SQUID) gradiometer. The principle of operation of these long baseline high-T c SQUID gradiometers is based on the inductive coupling of the input coil of a planar flux transformer to the pickup up loop of a directly coupled magnetometer. The long baseline of the gradiometer, 48 mm, and the intrinsic balance of better than 1 part in 100 make it an ideal candidate for operation in

  14. Enhanced flux-pinning properties in superconducting YBa2Cu3O(7-delta) thin films with nanoengineering

    NASA Astrophysics Data System (ADS)

    Tsai, Chen-Fong

    Since the discovery of the high temperature superconductor YBa2Cu3O7-delta (YBCO), with transition temperature (Tc = 77 K), above liquid nitrogen point in 1987 many research projects have been dedicated to enhancing the high field performance of this material for practical applications. The 2 nd generation YBCO-based coated conductors are believed to be the most promising approach for commercial applications including power transmission, motors, generators, and high field magnets. With the advances of nanotechnologies, different nanoengineering methods have been demonstrated to enhance the performance of YBCO thin films, include doping with 0-dimensional (0-D) self-assembled nanoparticles, 1-dimensional (1-D) nanorods, and 2-dimensional (2-D) nanolayers. Furthermore, dopants with ferromagnetic properties are also reported to provide enhanced pinning effects by Lorentz force, especially under high-applied magnetic fields. The principle of these methods is to generate high-density defects at the heterogeneous interfaces as artificial pinning centers in an effort to improve the flux-pinning properties. The morphology and dimensions of the nanoinclusions play an important role in pining enhancement. Optimized pinning structures are likely to be located at energetically favorable vortex cores, which form a triangular lattice with dimensions close to the YBCO coherence length xi (xiab ~ 4 nm; xic ~ 0.5 nm at 77 K.) However, it is challenging to achieve small dimensional nanodopants in the vapor deposited YBCO thin films. The purpose of this research is to utilize nanoengineering methods to produce optimized pinning structure in YBCO thin films. In this thesis, we systematically study the effects of different nanoinclusions on the flux-pinning properties of YBCO thin films. The 0-D ferromagnetic Fe 2O3 and CoFe2O4 nanoparticles, 2-D CeO2 multilayers, and tunable vertically aligned nanocomposites (VAN) of (Fe2O3)x:(CeO2) 1-x and (CoFe2O4)x:(CeO2) 1-x systems are introduced

  15. Transport, Structural, and Thermogravimetric Studies of LANTHANUM(1) - BARIUM(2) - COPPER(3) - OXIDE(7-DELTA): Correlations to the Structure and Empirical Superconducting Mechanism.

    NASA Astrophysics Data System (ADS)

    Golben, John Paul

    In this study, the different high temperature superconductor structures are discussed in detail, particularly the differences in the Cu-O structure. These structures are compared to the structure of La_1Ba _2Cu_3O _{7-delta}. The report by this investigation, of tetragonal La_1Ba _2Cu_3O _{7-delta} superconductors at the April (1987) meeting of the Materials Research Society, was one of the first reports of a tetragonal 1:2:3 structure (presumably without CuO "chains") in the superconducting state. This report indicated that the superconducting mechanism was directly inherent to the Cu-O square pyramidal "plane" structure, i.e. the superconducting mechanism was likely two-dimensional. The further structural study on the La_1Ba_2Cu _3O_{7-delta } series, provided information that the Cu -O "chains" were important for obtaining the highest values of T_{rm c} in the 1:2:3 structure. These structural studies were also important in ruling out the "3:3:6" structure that had been proposed as existing in this superconductor series. Changes in processing involved two different preparation methods (the coprecipitation and solid state reaction methods), and changes in processing variables such as temperature, ambient atmosphere (oxygen, air, argon), and time. The range of zero-resistance transition temperatures (T_ {rm c}'s) was markedly different between the coprecipitation and solid state reaction methods. The use of oxygen, air, or argon during the heating process also had substantial effects upon the transport properties and structure. In particular, oxygen diffusion or distribution in the structure was found to be very important for the superconducting state.

  16. Epitaxial yttria-stabilized zirconia on (1 -1 0 2) sapphire for YBa2Cu3O(7-delta) thin films

    NASA Technical Reports Server (NTRS)

    Wu, X. D.; Muenchausen, R. E.; Nogar, N. S.; Pique, A.; Edwards, R.

    1991-01-01

    Epitaxial yttria-stabilized zirconia (YSZ) films were deposited on (1 -1 0 2) sapphire by pulsed laser deposition. The films are formed in a cubic phase with the a axis normal to the substrate surface. Ion beam channeling measurements show that the YSZ films are highly crystalline with a channeling minimum yield of 8 percent. The epitaxial relationship between the film and substrate is further confirmed by a cross-section TEM study. Epitaxial YBa2Cu3O(7-delta) thin films deposited on YSZ/sapphire have Tc and Jc of up to 89 K and 10 to the 6th A/sq cm at 77 K, respectively.

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

    NASA Technical Reports Server (NTRS)

    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.

  18. Effect of proton irradiation and annealing on the critical current density in YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} single crystals

    SciTech Connect

    Viswanathan, H.K. |; Kirk, P.; Baldo, P.; Welp, U.; Crabtree, G.W.; Lee, W.C.; Giapintzakis, J. |

    1994-01-01

    We have studied the effect of annealing up to 350{degrees}C on the critical current densities in YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} single crystals that were irradiated with 3.5 MeV protons to a fluence of 1 {times} 10{sup 16} p+/cm{sup 2}. Large enhancements in the critical current densities, determined from DC-magnetization measurements, were observed immediately after irradiation at all temperatures for magnetic field orientations both parallel and perpendicular to the c-axis. These crystals were then annealed at room temperature, 100, 200, 300, and 350{degrees}C, and the critical current densities were determined after each annealing step. The annealing above room temperature resulted in a reduction of the critical current densities for both directions of the magnetic field. The transition temperatures, determined from low field DC-magnetization measurements at each stage of the measurement sequence, decreased by about 0.5 K following the irradiation and recovered to their original value after annealing at higher temperatures. We propose a defect model to explain the observed pining and its anisotropy observed in this work and earlier work on electron and neutron irradiated YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} single crystals.

  19. Flux pinning defects induced by electron irradiation in Y sub 1 Ba sub 2 Cu sub 3 O sub 7-. delta. single crystals

    SciTech Connect

    Giapintzakis, J.; Lee, W.C.; Rice, J.P.; Ginsberg, D.M.; Robertson, I.M. ); Kirk, M.A.; Wheeler, R. )

    1992-06-01

    Single crystals of R{sub 1}Ba{sub 2}Cu{sub 3}O{sub 7-{delta}}, (R=Y, Eu and Gd), have been irradiated with 0.4--1.0 MeV electrons in directions near the c-axis. An incident threshold electron energy for producing flux pinning defects has been found. In-situ TEM studies found no visible defects induced by electron irradiation. This means that point defects or small clusters ({le} 20 {Angstrom}) are responsible for the extra pinning. A consistent interpretation of the data suggests that the most likely pinning defect is the displacement of a Cu atom from the CuO{sub 2} planes.

  20. Flux pinning defects induced by electron irradiation in Y{sub 1}Ba{sub 2}Cu{sub 3}O{sub 7-{delta}} single crystals

    SciTech Connect

    Giapintzakis, J.; Lee, W.C.; Rice, J.P.; Ginsberg, D.M.; Robertson, I.M.; Kirk, M.A.; Wheeler, R.

    1992-06-01

    Single crystals of R{sub 1}Ba{sub 2}Cu{sub 3}O{sub 7-{delta}}, (R=Y, Eu and Gd), have been irradiated with 0.4--1.0 MeV electrons in directions near the c-axis. An incident threshold electron energy for producing flux pinning defects has been found. In-situ TEM studies found no visible defects induced by electron irradiation. This means that point defects or small clusters ({le} 20 {Angstrom}) are responsible for the extra pinning. A consistent interpretation of the data suggests that the most likely pinning defect is the displacement of a Cu atom from the CuO{sub 2} planes.

  1. Very Large Scale Integration of Nano-Patterned YBa2Cu3O7-delta Josephson Junctions in a Two-Dimensional Array

    SciTech Connect

    Cybart, Shane A; Anton, Steven; Wu, Stephen; Clarke, John; Dynes, Robert

    2009-09-01

    Very large scale integration of Josephson junctions in a two-dimensional series-parallel array has been achieved by ion irradiating a YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} film through slits in a nano-fabricated mask created with electron beam lithography and reactive ion etching. The mask consisted of 15,820 high-aspect ratio (20:1), 35-nm wide slits that restricted the irradiation in the film below to form Josephson junctions. Characterizing each parallel segment k, containing 28 junctions, with a single critical current I{sub ck} we found a standard deviation in I{sub ck} of about 16%.

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

    NASA Technical Reports Server (NTRS)

    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.

  3. Dependence of the critical temperature of laser-ablated YBa2Cu3O(7-delta) thin films on LaAlO3 substrate growth technique

    NASA Technical Reports Server (NTRS)

    Warner, Joseph D.; Bhasin, Kul B.; Miranda, Felix A.

    1991-01-01

    Samples of LaAlO3 made by flame fusion and Czochralski method were subjected to the same temperature conditions that they have to undergo during the laser ablation deposition of YBa2Cu3O(7 - delta) thin films. After oxygen annealing at 750 C, the LaAlO3 substrate made by two methods experienced surface roughening. The degree of roughening on the substrate made by Czochralski method was three times greater than that on the substrate made by flame fusion. This excessive surface roughening may be the origin of the experimentally observed lowering of the critical temperature of a film deposited by laser ablation on a LaAlO3 substrate made by Czochralski method with respect to its counterpart deposited on LaAlO3 substrates made by flame fusion.

  4. Amplitude-dependent magnetic stiffness of melt-quenched YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} superconductors

    SciTech Connect

    Yang, Z.J. |; Moon, F.C.; Murakami, M.

    1995-04-01

    Experimental results are reported on the differential levitation forces (magnetic stiffness) between permanent rare-earth magnets and high-temperature superconductors. Using a clamped beam cantilever, the amplitude-dependent magnetic stiffness for five configurations of the test magnets has been investigated for the melt-quenched YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (Y123) superconductors in a range of 1 {mu}m-1 mm. The configuration where the moment of the magnet and the direction of motion are perpendicular to the upper surface of the superconductor has the highest stiffness value among the five configurations. Compared with the data from a sintered Y123 superconductors, the magnetic stiffness for the melt-quenched materials has a much higher value and a much weaker dependence on the oscillation amplitudes. The results are compared with the current experimental and theoretical results.

  5. Doping directed at the oxygen sites in Y1Ba2Cu3O(7-delta) - The effect of sulfur, fluorine, and chlorine

    NASA Technical Reports Server (NTRS)

    Bansal, N. P.; Boyne, D.; Farrell, D. E.

    1988-01-01

    The effect of three dopants directed at the oxygen sites in Y1Ba2Cu3O(7-delta) have been investigated: sulfur, fluorine, and chlorine. Single-phase material has been obtained up to a (nominal) replacement of about 1 percent of the oxygen. Although the lattice parameters are unchanged, all dopants raise Tc (very slightly), sharpen the resistive transition, reduce the normal state resistivity, and very substantially increase the (magnetically determined) fraction of the material that is superconducting. All of these results differ qualitatively from those obtained with dopants directed at other locations in the 123 structure, and it is suggested that small additions of sulfur, fluorine, or chlorine may help to stabilize the ideal 123 stoichiometry.

  6. Superconductivity and Magnetic Properties of High Superconducting Transition Temperature Lanthanum - Barium - Calcium - COPPER(3) - OXYGEN(7-DELTA), YTTRIUM(1-X) Praseodymium(x) - BARIUM(2) - COPPER(2) - OXYGEN(7-DELTA), and NEODYMIUM(2-X) - Cesium(x) - Copper - OXYGEN(4-DELTA)

    NASA Astrophysics Data System (ADS)

    Peng, Jian-Liang

    A systematic study of the superconducting and normal state properties of LaBaCaCu_3O _{7-delta}, Y_{1-x}Pr_{x} Ba_2 Cu_3 O_{7-delta} and rm Nd_{2-x}Ce _{x} CuO_{4-delta} is reported in this work. X-ray powder diffraction, thermogravimetric analysis, dc electrical resistivity, and dc magnetic susceptibility measurements were used to characterize these samples. The compound LaBaCaCu _3O_{7-delta} belongs to the YBa_2 Cu _3 O_{7-delta} category, with Ca on the Y sites and La on Ba sites. This compound has a tetragonal structure and a superconducting transition temperature (T_{c}) of 78K. The low temperature x-ray powder diffraction indicated that the tetragonal structure of this compound is preserved down to 5K. The achievement of high-T_ {c} superconductivity in this tetragonal compound along with the other tetragonal superconductors indicates that the presence of one dimensional chains is not essential for achieving T_ {c} > 70K. In contrast, the existence of Cu-O planes is crucial in sustaining the high T _{c}. Substitution of Pr for Y in the Y_{1-x} Pr_{x}Ba_2 Cu_3O_{7-delta} system depresses T_{c}, with a behavior which is consistent with the classical Abrikosov-Gor'kov pair breaking theory. The critical field versus temperature shows a "bell"-shaped behavior for some compositions. This discovery is reminiscent of the magnetic superconductors RRh_4B_4 and RMo_6S_8 (R = rare earths), and is consistent with the presence of magnetic pair breaking interactions. The fact that the Pauli susceptibility increases with the addition of Pr and the super-oxygenation studies imply that the effect of the Pr cannot be just to remove holes from the Cu-O planes. A metal-insulator transition is evidenced in the normal state resistivity measurements at x ~ 0.6. Samples of Nd_{2 -x} Ce_{x} CuO_{4-delta } (0 <=q x <=q 0.2) were prepared by annealing both in air and under vacuum (10 ^{-5} torr). Electrical resistivity measurements showed that all Ce doped Nd_2 CuO_{4-delta} samples

  7. Determination of surface resistance and magnetic penetration depth of superconducting YBa2Cu3O(7-delta) thin films by microwave power transmission measurements

    NASA Technical Reports Server (NTRS)

    Bhasin, K. B.; Warner, J. D.; Miranda, F. A.; Gordon, W. L.; Newman, H. S.

    1990-01-01

    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 approx. 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 approx. 0.54 and 0.43 micron, and the surface resistance (R sub s) to be approx. 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 temperature superconducting thin films at microwave frequencies.

  8. Determination of surface resistance and magnetic penetration depth of superconducting YBa2Cu3O(7-delta) thin films by microwave power transmission measurements

    NASA Technical Reports Server (NTRS)

    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.

  9. Characterizing transport current defects in 1-cm-wide YBa[sub 2]Cu[sub 3]O[sub 7-delta] coated conductors.

    SciTech Connect

    Brown, G. W.; Hawley, M. E.; Peterson, E. J.; Coulter, J. Y.; Dowden, P. C.; Arendt, P. N.; Foltyn, S. R.; Mueller, F. M.

    2001-01-01

    We have used a low temperature magnetic imaging system to determine current pathways in 5 cm long 'good' and 'bad' regions of a 1-cm-wide YBa2Cu3O7-{delta} coated conductor. The good and bad regions were identified with 4 point probe measurements taken at 1 cm intervals along the tape length. The current density map from the good region showed the expected edge peaked structure, similar to that seen in previous work on high quality test samples grown on single crystal substrates. The structure was also consistent with theoretical understanding of thin film superconductors where demagnetizing effects are strong. The maps from the bad region showed that the current was primarily confined to the right half of the sample. The left half carried only a small current that reached saturation quickly. Effectively halving the sample width quantitatively explains the critical current measured in that section. Spatially resolved xray analysis with 1 mm resolution was used to further characterize the bad section and suggested an abnormally large amount of a-axis YBCO present. This may be the result of non-uniform heating leading to a low deposition temperature in that area.

  10. Microwave conductivity of laser ablated YBa2Cu3O(7-delta) superconducting films and its relation to microstrip transmission line performance

    NASA Technical Reports Server (NTRS)

    Bhasin, K. B.; Warner, J. D.; Chorey, C. M.; Ebihara, B. T.; Romanofsky, R. R.; Heinen, V. O.; Miranda, F. A.; Gordon, W. L.

    1991-01-01

    The discovery of high temperature superconductor oxides has raised the possibility of a new class of millimeter and microwave devices operating at temperatures considerably higher than liquid helium temperatures. Therefore, materials properties such as conductivity, current density, and sheet resistance as a function of temperature and frequency, possible anisotropies, moisture absorption, thermal expansion, and others, have to be well characterized and understood. The millimeter wave response of laser ablated YBa2Cu3O(7-delta)/LaAlO3 thin films was studied as a function of temperature and frequency. In particular, the evaluation of their microwave conductivity was emphasized, since knowledge of this parameter provides a basis for the derivation of other relevant properties of these superconducting oxides, and for using them in the fabrication of actual passive circuits. The microwave conductivity for these films was measured at frequencies from 26.5 to 40.0 GHz, in the temperature range from 20 to 300 K. The values of the conductivity are obtained from the millimeter wave power transmitted through the films, using a two fluid model.

  11. A Model Approach to Flux-Pinning Properties of YBa2Cu 3O7-delta Thin Film Vortex States via Non-Superconducting Impurities

    NASA Astrophysics Data System (ADS)

    Gamble, Ronald S., Jr.

    Thin film YBa2Cu3O7--delta (YBCO) samples with added non-superconducting nanodot defects of CeO 2 and BaSnO2 are the focus of recent high-temperature superconductor studies. These nanodots allow magnetic flux to penetrate at these sites of the superconducting lattice thus creating a magnetic flux vortex state. Examining the structure shows that these quantized magnetic flux vortices arrange themselves in a self-assembled lattice. The nanodots, with non-superconducting properties, serve to present structural properties to restrict motion of these vorticies under a pinning-force and to enhance the critical current density. A formulation of a new model for the system by a variation in the electron pair velocity via the virtual work from the nanodot defects in accordance to the well-known Superconductivity theories is tested. A solution to the expression for the magnetic flux, zero net force and pair velocity will generate a setting for the optimal deposition parameters of number density, growth geometry and mass density of these nanodot structures. With a calculation of pair velocities from a similar work, a comparison is made between experimental and theoretical velocity calculations using growth geometry and chemical potential. This will yield insight into how the current density for a doped high-temperature superconductor will be modified and tuned based on the dynamics and density of the nanodots themselves.

  12. Refinement of the composition and structure of YBaCo{sub 4-x}Al{sub x}O{sub 7+{delta}} crystals

    SciTech Connect

    Podberezskaya, N. V. Kozeeva, L. P.; Kameneva, M. Yu.; Smolentsev, A. I.; Alekseev, A. V.; Lavrov, A. N.

    2011-05-15

    YBa(Co{sub 4-x}Al{sub x})O{sub 7+{delta}} (114Y) crystals have been grown in the Y-Ba-Co-O system by spontaneous crystallization from a slowly cooled nonstoichiometric melt. To change the oxygen content, the crystals were isothermally annealed in air in the range of 280-490 Degree-Sign C. The crystals grown were characterized by scanning electron microscopy and powder X-ray diffraction. According to the data of an X-ray spectroscopic quantitative microprobe analysis, the average compositions of 'as-grown' and oxygen-saturated crystals were Y{sub 1.04}Ba{sub 1}Co{sub 3.54}Al{sub 0.50}O{sub 7.8} and Y{sub 1.02}Ba{sub 1}Co{sub 3.55}Al{sub 0.51}O{sub 8.4}, respectively. The refinement of the crystal structure after saturation on an automatic Bruker X8APEX diffractometer with a CCD detector (MoK{alpha} radiation, graphite monochromator, {theta}{sub max} = 32.54 Degree-Sign , sp. gr. P6{sub 3}mc, a = 6.2746(9), c = 10.257(3) Angstrom-Sign , V = 349.71(13) Angstrom-Sign {sup 3}, Z = 2, d{sub calcd} = 5.220 g/cm{sup 3}) reveals the location of Al in two independent positions of Co atoms and yields the general formula of the compound as YBaCo{sub 3.26}Al{sub 0.74}O{sub 7}. Problems related to the difference in the compositions obtained by different methods are discussed.

  13. Electronic structure of the quenched superconductivity materials Y/sub 1-x/Pr/sub x/Ba/sub 2/Cu/sub 3/O/sub 7-delta/

    SciTech Connect

    Kang, J.S.; Allen, J.W.; Shen, Z.X.; Ellis, W.P.; Yeh, J.J.; Lee, B.W.; Maple, M.B.; Spicer, W.E.; Lindau, I.

    1988-01-01

    The superconductivity of the Y/sub 1-x/Pr/sub x/Ba/sub 2/Cu/sub 3/O/sub 7-delta/ system is quenched as x increases. It has been speculated that Pr has valence 4+, resulting in extra charge in the Cu-O planes, and causing T/sub c/-quenching. To study the Pr electronic state, we have measured valence band resonant photoemission of the Y/sub 1-x/Pr/sub x/Ba/sub 2/Cu/sub 3/O/sub 7- delta/ system for x = 0, 0.2, 0.4, 0.6, 0.8, and 1.0. We find that the Pr valence is close to 3+ for all x and that the extracted Pr 4f spectral weight has a complex lineshape, implying extensive Pr 4f/O 2p hybridization which probably causes the T/sub c/-quenching by disrupting the electronic or magnetic structure of the x = 0 material, perhaps via a Pr-Cu superexchange interaction. 36 refs., 4 figs.

  14. Low-temperature synthesis and structure characterization of the serials Y{sub 2-{delta}}Bi{sub {delta}}Sn{sub 2}O{sub 7} ({delta}=0-2.0) nanocrystals

    SciTech Connect

    Li Kunwei; Zhang Tingting; Wang Hao . E-mail: haowang@bjut.edu.cn; Yan Hui

    2006-04-15

    A series of Y{sub 2-{delta}}Bi{sub {delta}}Sn{sub 2}O{sub 7} ({delta}=0, 0.1, 0.3, 0.5, 1.0, 1.5, and 2.0) nanocrystals were successfully synthesized by the low-temperature hydrothermal method. The structures of serial compounds were characterized by X-ray diffraction (XRD) and infrared (IR) absorption spectroscopy, and were further refined by TOPAS software by Bruker AXS using the whole powder pattern data. These materials form a series of cubic pyrochlore-type oxides at low temperature and are consistent with Vegards' law, indicating that the hydrothermal synthesis conferred a higher chemical homogeneity and reactivity on the powders, and resulting in low crystallization temperature for the pyrochlore-phase complex oxides.

  15. Polypyrrole growth on YBa{sup 2}Cu{sup 3}O{sup 7-{delta}} modified with a self-assembled monolayer of N-(3-aminopropyl)pyrrole: Hardwiring the `electroactive hot spots` on a superconductor electrode

    SciTech Connect

    Lo, R.K.; Ritchie, J.E.; Zhou, J.P.; Zhao, J.; McDevitt, J.T.; Xu, F.; Mirkin, C.A.

    1996-11-13

    This paper describes a new method for controlling the deposition of conductive polymer systems onto high-T{sup c} superconductor surfaces. This method relies on the spontaneous adsorption of the pyrrole-terminated alkylamine reagent 1 onto YBa{sup 2}Cu{sup 3}O{sup 7-{delta}} prior to polymerization. Large changes in the polymer growth rates and vast improvements in the polymer morphology are obtained with the use of such adsorbed monolayers. As described, the adsorbed monolayer structures promote radically different polymer deposition properties from those observed previously for the more traditional electrode materials (i.e., Au, Pt, etc.). These unusual observations provided valuable insight into the electrochemical characteristics and local surface electroactivity/conductivity properties of oriented cuprate superconductor films. 16 refs., 2 figs.

  16. Hybridization and Electron Doping in the Highly - Electronic Materials YTTRIUM(1-X) Uranium(x) PALLADIUM(3) and YTTRIUM(1-X) Praseodymium(x) BARIUM(2) COPPER(3) OXYGEN(7-DELTA)

    NASA Astrophysics Data System (ADS)

    Seaman, Christopher Lawrence

    Measurements of electrical resistivity rho(T), magnetic susceptibility chi (T), and specific heat C(T) for the system Y_{1-x}U_{x}Pd _3 are presented. The data are consistent with nearly localized tetravalent U ions leading to "Fermi -level tuning" and competition between single ion Kondo (0 < x <= 0.2) and cooperative spin glass-like (0.3 <= x <= 0.5) behavior. The Kondo behavior is unusual and well described by the two-channel quadrupolar Kondo effect which exhibits non-Fermi liquid behavior. At low temperatures T<< T_{K }, where T_{K } is the Kondo temperature, the electrical resistivity varies nearly linearly with temperature rho(T)/rho(0)~1-T/(aT_ {K}), and the electronic specific heat diverges logarithmically Delta C/T ~{-(1}/T_{K})lnT with a finite residual T = 0 entropy S(0) ~ (R/2)ln2. This appears to be the first example of the quadrupolar Kondo effect and two-channel behavior in a dilute alloy with concomitant non-Fermi liquid behavior. The magnetic penetration depth of the high-T _{c} superconducting system Y_{1-x}Pr_{x }Ba_2Cu_3O_{6.97} has been measured for 0.05 <= x <= 0.4 using the technique of transverse -field muon-spin relaxation. The temperature dependence is similar to that of the related compounds rm YBa_2Cu_3O_{7-delta} with varying oxygen content. The zero-temperature relaxation rate sigma(0) and T _{c} both decrease monotonically with x, in a manner similar to that of YBa_2Cu_3O_{7-delta} with increasing delta. This observation is consistent with the interpretation that T_{c} is largely suppressed by means of the annihilation of holes in the conducting CuO_2 planes by the Pr ions. A simple explanation is that Pr is nearly tetravalent in this system. The influence of magnetic pair breaking, finite mean free path, and correlation with results for other high-T_{c} superconductors are discussed. Resistive superconducting transitions have been measured for single crystals of Y_ {1-x}Pr_{x}Ba_2Cu_3O _{7-delta} in applied magnetic fields as high

  17. Superconductivity of the Pr-substituted (Nd/sub 1-x/Pr/sub x/)Ba/sub 2/Cu/sub 3/O/sub 7-/delta// system

    SciTech Connect

    Ku, H.C.; Chen, C.C.; Hsu, S.W.

    1988-12-01

    Electrical, magnetic and crystallographic measurements have been carried out for the pseudoquaternary (Nd/sub 1-x/Pr/sub x/)Ba/sub 2/Cu/sub 3/O/sub 7-/delta// system. Orthorhombic phase persists from chi = 0.0 up to chi = 0.7 and transforms into the tetragonal structure only for chi /ge/ 0.8. Superconducting transition temperature T/sub c/ decreases linearly from 92 K for chi = 0.0 to below 10 K for chi = 0.3 and extrapolated to 0 K around chi = 0.35. Magnetic susceptibility indicates that the valence of the Pr ion is close to 4+. Pr/sup 4+/ is a very powerful oxidizing agent and may distort or move oxygen away from the Cu-O chain and/or the /CuO/sub 2/ planes and seriously suppress superconductivity.

  18. Role of Nd/Ba Disorder on the Penetration Depth of Nd{sub 1+x}Ba{sub 2-x}Cu{sub 3}O{sub 7-{delta}} Thin Films

    SciTech Connect

    Salluzzo, M.; Palomba, F.; Pica, G.; Andreone, A.; Maggio-Aprile, I.; Fischer, Oe.; Cantoni, C.; Norton, D. P.

    2000-07-31

    We report on a study on the effect of Nd/Ba disorder on the ab -plane penetration depth of epitaxial Nd{sub 1+x}Ba {sub 2-x}Cu{sub 3}O{sub 7-{delta}} thin films. While in stoichiometric samples {lambda}(T) at low temperature is linear, Nd-rich films exhibit a quadratic law. For low Nd excess (x<0.04) , a satisfying fit is obtained using the ''dirty'' d -wave model assuming that Nd ions at Ba sites act as strong scattering centers. At high x (x>0.15) the data are explained if Nd/Ba disorder becomes less effective as a source of scattering. The effect of localization has been discussed to account for the experimental results. (c) 2000 The American Physical Society.

  19. Phase relationships and cation disorder in RE{sub 1+x}Ba{sub 2-x}Cu{sub 3}O{sub 7+{delta}}, RE = Pr, Nd, Sm, Gd

    SciTech Connect

    Kramer, M.J.; Wu, H.; Dennis, K.W.; Polzin, B.I.; Falzgraf, D.K.; McCallum, R.W.

    1995-12-31

    Unlike Y123 which forms only a stoichiometric compound, the light arare earth elements (LRE) form a solid solution LRE{sub 1+x}Ba{sub 2-x}Cu{sub 3}O{sub 7+{delta}} (LRE123ss), with increasing substitution of the LRE{sup 3+} for the Ba{sup 2+} as the ionic radii of the LRE increases. The sub-solidus phase relationships around the LRE123ss change for La, Pr and Nd, but are similar for Sm and Gd. However, the solubility limit decreases with decreasing ionic radii. In addition, the solubility limits for Sm and Gd are strongly influenced by PO{sub 2} during high temperature annealing. The range of solubility is, for any given LRE system, strongly dependent on the oxygen partial pressure (PO{sub 2}) providing a new means by which to control the microstructure in the RE123 system.

  20. Formation of Y(x)Nd(1-x) Ba2Cu3O(7-delta) (0 = or < x < or = 0.7) Superconductors from an Undercooled Melt Via Aero-Acoustic Levitation

    NASA Technical Reports Server (NTRS)

    Gustafson, D. E.; Hofmeister, W. H.; Bayuzick, R. J.

    2001-01-01

    Melt processing of RE123 superconductors has gained importance in recent years. While the first high temperature superconductors (HTSCs) were made using traditional ceramic press and sinter technology, recent fabrication efforts have employed alternate processing techniques including laser ablation and ion beam assisted deposition for thin film fabrication of tapes and wires and melt growth for bulk materials. To optimize these techniques and identify other potential processing strategies, phase relation studies on HTSCs have been conducted on a wide variety of superconducting compounds using numerous processing strategies. This data has enhanced the understanding of these complex systems and allowed more accurate modeling of phase interactions. All of this research has proved useful in identifying processing capabilities for HTSCs but has failed to achieve a breakthrough for wide spread application of these materials. This study examines the role of full to partial substitution of Nd in the Y123 structure under rapid solidification conditions. Aero-acoustic levitation (AAL) was used to levitate and undercool RE123 in pure oxygen binary alloys with RE = Nd an Y along a range of compositions corresponding to Y(x)Nd(1-x) Ba2Cu3O(7-delta) (0 = or < x < or = 0.7) which were melted by a CO2 laser. Higher Y content spheres could not be melted in the AAL and were excluded from this report. Solidification structures were examined using scanning electron microscopy, electron dispersive spectroscopy, and powder x-ray diffraction to characterize microstructures and identify phases.

  1. Charge/orbital ordered phases of La{sub 2-2x}Sr{sub 1+2x}Mn{sub 2}O{sub 7-{delta}}.

    SciTech Connect

    Zheng, H.; Li, Q.; Gray, K. E.; Mitchell, J. F.; Materials Science Division

    2008-01-01

    Our studies have significantly modified the conventionally held view of the phase diagram of La{sub 2-2x}Sr{sub 1+2x}Mn{sub 2}O{sub 7-{delta}} for two compositions exhibiting charge (and orbital) order (CO), i.e., at hole-doping levels, h = x-{delta}, of {approx}0.5 and {approx}0.6. These CO states are stable over very narrow doping ranges ({Delta}h {+-} 0.005) at the lowest temperatures, but those ranges increase at higher temperatures (to {Delta}h {+-} 0.02) in a manner consistent with simple entropy considerations. Such narrow ranges dictate the crucial need for crystal homogeneity. Attesting to such homogeneity is a conductivity ratio of >10{sup 10} upon crossing the first-order phase boundary from CO at h = 0.60 to A-type antiferromagnetic (AAFM) at h-0.59 or h-0.61 plus two findings that were missed in the existing literature: that these CO phases are the ground state at the lowest temperatures, and for h-0.5, that coexistence of the CO and AAFM phase is absent at any temperature.

  2. Ion-assisted laser deposition of intermediate layers for YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} thin film growth on polycrystalline and amorphous substrates

    SciTech Connect

    Reade, R.P.

    1993-11-01

    The growth of YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO) high-temperature superconductor thin films has largely been limited to deposition on single-crystal substrates to date. In order to expand the range of potential applications, growth on polycrystalline and amorphous substrates is desirable. In particular, the deposition of YBCO thin films with high critical current densities on polycrystalline metal alloys would allow the manufacture of superconducting tapes. However, it is shown that it is not possible to grow YBCO thin films directly on this type of substrate due to chemical and structural incompatibility. This work investigates the use of a yttria-stabilized zirconia (YSZ) intermediate layer to address this problem. An ion-assisted pulsed-laser deposition process is developed to provide control of orientation during the growth of the YSZ layers. The important properties of YBCO and YSZ are summarized and the status of research on thin film growth of these materials is reviewed. An overview of the pulsed-laser deposition (PLD) technique is presented. The use of ion-assisted deposition techniques to control thin film properties is discussed.

  3. Several Microstrip-Based Conductor/Thin Film Ferroelectric Phase Shifter Designs Using (YBa2Cu3O(7 - Delta), Au)/SrTiO3/LaAlO3 Structures

    NASA Technical Reports Server (NTRS)

    VanKeuls, F. W.; Romanofsky, R. R.; Miranda, F. A.

    1998-01-01

    We have designed, fabricated, and tested several novel microstrip-base YBa2Cu3O7-delta/SrTiO3/LaAlO3 (YBCO/STO/LAO) and Au/SrTiO3ALO3 (Au/STO/LAO) phase shifters. The first design consists of eight coupled microstrip phase shifters (CMPS) in series. This design using YBCO achieved a relative insertion phase shift (Delta f) of 484 degrees with a figure of merit of 80 degrees/dB at Vdc = 375 V, 16 GHz, and 40 K. A Delta f of 290 degrees was observed while maintaining the insertion loss below 4.5 dB. At 77 K, a Delta of 420 degrees was obtained for this phase shifter at the same bias and frequency. Both results correspond to an effective coupling length of 0.33 cm. A second compact design, consisting of an Au meander line and a CMPS section was also tested. Of the two samples tested, the best showed a figure of merit of 43 degrees/dB with Delta f = 290 degrees and 6.8 dB loss, at 40 K, 10 GHz and 400 V. Experimental and modeling results on these circuits will be discussed in the context of potential applications.

  4. Effect of YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} film thickness on the dielectric properties of Ba{sub 0.1}Sr{sub 0.9}TiO{sub 3} in Ag/Ba{sub 0.1}Sr{sub 0.9}TiO{sub 3}/YBa{sub 2}Cu{sub 3}O{sub 7-{delta}}/LaAlO{sub 3} multilayer structures

    SciTech Connect

    Zhu Xiaohong; Peng Wei; Li Jie; Chen Yingfei; Tian Haiyan; Xu Xiaoping; Zheng Dongning

    2005-01-01

    Ferroelectric and superconductor bilayers of Ba{sub 0.1}Sr{sub 0.9}TiO{sub 3} (BSTO)/YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO), with different YBCO film thicknesses, have been fabricated in situ by pulsed-laser deposition on 1.2 deg. vicinal LaAlO{sub 3} substrates. The dielectric properties of BSTO thin films were measured with a parallel-plate capacitor configuration in the temperature range of 77-300 K. We observed a strong dependence of the dielectric properties of BSTO thin films on the thickness of the YBCO layer. As the YBCO-film thickness increases, the temperature of the dielectric permittivity maximum of BSTO thin films shifts to higher values, and the leakage current and dielectric loss increase drastically, while the dielectric constant and dielectric tunability decrease remarkably. The results are explained in terms of the transformation in the growth mode of the YBCO layer from two-dimensional step flow to three-dimensional island that leads to significant deterioration in the dielectric properties of BSTO thin films. We propose that improved dielectric properties could be obtained by reasonably manipulating the growth mode of the YBCO layer in the multilayer structures.

  5. Ceramic wire and coil made of YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} high-temperature superconductor with a critical current density up to 75 A {center_dot}cm{sup {minus}2} at 77 K

    SciTech Connect

    Basalaeva, T.S.; Ordan`yan, S.S.; Polonskii, Y.A.

    1995-03-20

    Processing parameters are refined and a route is found for fabricating wires, coils, and other lengthy electrotechnical elements form high-temperature superconducting ceramic YBa{sub 2}Cu{sub 3}O{sub 7-{delta}}. The superconducting transition temperature of around 90 K and a critical current density in the terrestrial magnetic field of 35-75 A {center_dot} cm{sup {minus}2} at 77 K characterize the performance of the wire.

  6. Thermal fluctuation effects on the magnetization above and below the superconducting transition in Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} and YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} crystals in the weak magnetic field limit

    SciTech Connect

    Mosqueira, J.; Ramallo, M.V.; Torron, C.; Vidal, F.

    1996-12-01

    The authors present detailed experimental data of the magnetization, M{sub ab}(T,H), of Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} and YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} crystals on both sides of the superconducting transition, for magnetic fields, H, applied perpendicularly to the ab (CuO{sub 2}) planes. The data are analyzed in terms of thermal fluctuations in the weak H limit: In the reversible mixed state below the transition, by taking into account the vortex fluctuations, as first proposed by Bulaevskii, Ledvij and Kogan, which are much more important in the Bi-based compounds. Above the transition, by taking into account the order parameter amplitude fluctuations (OPF), through a generalization to multilayered superconductors of the Schmidt-like approach.

  7. Ln{sub 2}Sr{sub 2}PtO{sub 7+{delta}} (Ln=La, Pr, and Nd): Three new Pt-containing [A{sub 2}{sup '}O{sub 1+{delta}}] [A{sub n}B{sub n-1}O{sub 3n}]-type hexagonal perovskites

    SciTech Connect

    Ebbinghaus, Stefan G. Erztoument, Chasanoglou; Marozau, Ivan

    2007-12-15

    Polycrystalline samples of Ln{sub 2}Sr{sub 2}PtO{sub 7+{delta}} (Ln=La, Pr, Nd) were prepared by conventional solid state synthesis. The three compounds are new examples for n=2 members of the [A{sub 2}{sup '}O{sub 1+{delta}}][A{sub n}B{sub n-1}O{sub 3n}] family of hexagonal perovskites containing platinum as the B-type cation. XRD Rietveld refinements show the platinates to crystallize in space group R3-bar and, in the case of Pr and Nd, revealed a complete ordering of Ln/Sr on the two distinct A-type positions, while for La a partial disorder was observed. By XANES investigations at the Pt-L{sub III} threshold the oxidation state +4 for platinum was found. Thermogravimetry revealed a small oxygen excess for Ln=La and Pr ({delta}=0.13 and 0.07), pointing to the presence of peroxide ions as already observed for isostructural Ru- and Ir-based compounds. UV-Vis measurements were done for the yellow lanthanum and the green neodymium compound. They revealed two optical band gaps of 2.52 and 3.05 eV, respectively. Magnetic measurements showed La{sub 2}Sr{sub 2}PtO{sub 7+{delta}} to be diamagnetic as expected for Pt{sup 4+} with low-spin (t{sub 2g}{sup 6}) configuration. For Ln=Pr and Nd the observed strong paramagnetism can be explained solely by the magnetic moments of the rare earths. - Graphical abstract: Hexagonal perovskites of the [A{sub 2}{sup '}O{sub 1+{delta}}][A{sub n}B{sub n-1}O{sub 3n}] family have so far only been known for the transition metals Mn, Nb, Ru, and Ir. In this paper, three new n=2 examples containing platinum as B-type cation are presented. The structure and physical properties of the three title compounds were investigated by XRD Rietveld refinements, thermogravimetry, X-ray absorption spectroscopy, magnetic measurements and optical spectroscopy.

  8. Contrasting Effects of Ca{sup 2+} and Ho{sup 3+} Substitutions on Superconductivity and Excess conductivity of (Ho{sub 1-x}Ca{sub x})(Ba{sub 2-y}Ho{sub y})Cu{sub 3}O{sub 7-{delta}}

    SciTech Connect

    Maulud, M. F.; Hamidi, Z. S.; Yusof, A. A.; Yusof, M. I. M.; Yahya, A. K.

    2010-07-07

    Effects of Ho{sup 3+} and Ca{sup 2+} substitutions in (Ho{sub 1-x}Ca{sub x})(Ba{sub 2-y}Ho{sub y})Cu{sub 3}O{sub 7-{delta}}ceramics on normal and superconducting state behaviour were investigated. Electrical resistivity measurements showed increasing Ho{sup 3+} substitution at Ba{sup 2+} site (x = 0, 0.4, y = 0-0.4) caused normal state resistivity to change from metal-like to semimetal/semiconductor-like behaviour and suppressed T{sub c} from 89 K (y = 0) to 72 K (y = 0.4) while substitution of Ca{sup 2+} for Ho{sup 3+}((x = 0.2) 0.4, (y 0.4)) revives metallic behaviour of the normal state with increasing x. Excess conductivity analysis based on Asmalazov-Larkin theory showed 2D to 3D transition for all superconducting samples but with contrasting effects of the substitutions on AL{sub 2D} and AL{sub 3D} constants. The resistivity and excess conductivity results indicate effective hole filling Ho{sup 3+} and hole doping by by Ca{sup 2+} substitutions.

  9. Manufacture of bulk superconducting YBa2Cu3O(7-delta) by a continuous process

    NASA Technical Reports Server (NTRS)

    Meng, R. L.; Kinalidis, C.; Sun, Y. Y.; Gao, L.; Tao, Y. K.

    1990-01-01

    The development of a continuous process for fabricating large bulk superconductors with a predetermined grain orientation is reported. A bar of the 123 compound with dimensions 5 x 0.5 x about 0.3 cm with excellent grain alignment has been fabricated continuously. The bulk 123 thus obtained has magnetically determined J(c)s of about 30,000 and 12,000 A/sq cm at 0 and 1 T, respectively, and transport J(c)s of 20,000, 11,000, and 7500 A-sq cm at 0, 0.54, and 0.83 T.

  10. Anomalous noise in the pseudogap regime of YBa2Cu3O(7-delta).

    PubMed

    Caplan, D S; Orlyanchik, V; Weissman, M B; Van Harlingen, D J; Fradkin, E H; Hinton, M J; Lemberger, T R

    2010-04-30

    An unusual noise component is found near and below about 250 K in the normal state of underdoped YBCO and Ca-YBCO films. This noise regime, unlike the more typical noise above 250 K, has features expected for a symmetry-breaking collective electronic state. These include large individual fluctuators, a magnetic sensitivity, and aging effects. A possible interpretation in terms of fluctuating charge nematic order is presented. PMID:20482127

  11. Electron irradiation effects in YBa/sub 2/Cu/sub 3/O/sub 7-delta/ single crystals

    SciTech Connect

    Kirk, M.A.; Baker, M.C.; Liu, J.Z.; Lam, D.J.; Weber, H.W.

    1988-04-01

    Defect structures in YBa/sub 2/Cu/sub 3/O/sub 7/minus/delta/ produced by electron irradiation at 300/degree/K, were investigated by transmission electron microscopy. Threshold energies for the production of visible defects were determined to b 152 keV and 131 keV (+- 7 keV) in directions near the a- and b-axes, respectively (b > a, both perpendicular to c, the long axis in the orthorhombic structure). During above-threshold irradiations in an electron flux of 3 x 10 /sup 18/ cm/sup /minus/2/s/sup /minus/1/, extended defects were observed to form and grow to sizes of 10--50 nm over 15 minutes, in material thicknesses varying between 20 and 200 nm. Upon irradiation between the a- and b-thresholds, movement of twin plane boundaries and shrinkage of twinned volume were observed. All these findings suggest oxygen atom displacements in the basal plane with recoil energies near 20 eV. Above-threshold irradiations also show the collapse of c-axis long-range order into a planar faulted defect structure with short range order peaks at 1.2 c and 1.07 c, depending on the irradiation direction. 9 refs., 4 figs.

  12. Microstructure and composition of electromagnetically-characterized YBa sub 2 Cu sub 3 O sub 7-. delta. grain boundaries

    SciTech Connect

    Babcock, S.E.; Zhang, Na; Cai, Xue Yu; Larbalestier, D.C. ); Gao, Yufei; Merkle, K.L. ); Kaiser, D.L. , Gaithersburg, MD . Ceramics Div.)

    1991-01-01

    The electrical character (flux-pinning, Josephson junction, or resistive) of the grain boundaries in approximately twenty flux-grown YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} bicrystals was determined in previous studies. A selection of these same bicrystals now have been thinned for study by transmission and scanning transmission electron microscopy. High-spatial resolution imaging and analytical techniques reveal microstructural differences among these boundaries that are consistent with their diverse electrical characteristics. The observations offer preliminary insight into some of the feature that control the grain boundary superconducting properties and re-emphasize the very fine scale on which the grain boundary electrical character is determined. 11 refs., 6 figs.

  13. Terahertz emission from YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} thin films

    SciTech Connect

    Siders, J.L.W.; Gosnell, T.R.; Trugman, S.A.; Taylor, A.J.

    1998-12-31

    We report the first observation of terahertz emission from unbiased YBa{sub 2}Cu{sub 3}O{sub 7} thin films at room temperature excited by 1.5 eV femotosecond laser pulses. The strength of the radiated terahertz field depends on the incident angle ({theta}) and depends linearly on incident power. The terahertz emission also depends strongly on the rotation of the film about its surface normal (azimuthal angle, {phi}). The strong anisotropy, with 4{phi} symmetry is demonstrated for different polarizations (incident and detected) and found to be consistent with optical rectification. Because YBCO is centrosymmetric, the second order nonlinear susceptibility vanishes. The next order term in the nonlinear polarizations is the electric quadrupole source term which describes the observed data quite well. The terahertz radiation was found to decrease with decreasing oxygen content, indicating that the carriers in the doped sample enhance the nonlinearity responsible for the terahertz emission.

  14. Effect of Alternative Insulation Materials on Quench Propagation in ReBa2Cu3O7-delta Coils

    NASA Astrophysics Data System (ADS)

    Phillips, Makita R.

    ReBa2Cu3Odelta-7 (REBCO) coils have the potential to impact a variety of magnet applications but due to slow normal zone propagation velocity (NZPV), quench detection and protection remain difficult. It is therefore important to understand how quench behavior is affected by various aspects of coil design, geometric considerations and material properties. Although past studies have explored the effects of varying the conductor properties, it is important to investigate the influence of insulation as well. In this study, the effect of insulation properties on three-dimensional (3D) quench propagation in REBCO-based coils is investigated. At present, superconducting magnets primarily use insulators that are electrically and thermally insulating; typically Kapton. Here the impact of electrically insulating, thermally conducting insulators on quench behavior was studied. In particular, the behavior of a Kapton insulated coil was compared to doped-TiO2 and ideal Al2O3 insulated coils. A non-insulated coil was also evaluated. Using a mixed-dimensional model the effect of various insulation materials on multiple quench parameters in REBCO coated conductor coils was studied. The comparison of the usage alternative insulation was conducted for a 20 mum and 100 mum case using three models: Concept Model 1, 2 and 3. Concept model 1 studied the effects on 3D propagation behavior, including the 3D current sharing volume (CSV) and key quench parameters, including minimum quench energy, hotspot temperature and NZPV. Concept model 2 (CM 2) cooled a room temperature coil configuration from room temperature to 50 K for a 15 min duration. The radial and hoop stresses were observed at the cleavage edge, middle height and along the conductor width in the central conductor. Concept model 3 (CM 3) determined the thermal stresses based upon the thermal development of CM 1 during a quench. Concept model 1 found that ideal Al2O3 insulation resulted in the highest MQE, lowest peak temperature, slowest rate of increase in hotspot temperature, fastest transverse NZPV and smallest CSV. These results indicated that increasing the thermal conductivity of coil insulation can significantly improve coil behavior. Concept model 2 found that doped- TiO 2 and ideal Al2O3 had the most desirable effect by having the most compression within the conductors. The compression present during cool down could lessen the effect of tension during operation. CM 3 showed that NI has less tensile variation between the REBCO layers and could be helpful so that stress is distributed evenly to reduce stress concentrations. Doped -TiO2 had the lower stress values for each insulation thickness. The lower stress is desirable to reduce the risk for delamination.

  15. Chemical solution approaches to YBa2Cu3O7_delta-Au nanocomposite superconducting thin films.

    PubMed

    Martínez-Julián, F; Ricart, S; Pomar, A; Col, M; Abellán, P; Sandiumenge, F; Casanove, M J; Obradors, X; Puig, T; Pastoriza-Santos, I; Liz-Marzán, L M

    2011-04-01

    We explore the feasibility of preparing YBa2CU3O7-Au (YBCO-Au) nanocomposite thin films by chemical solution deposition (CSD). Two approaches were used: (i) A standard in-situ methodology where Au metallorganic salts are added into the precursor solution of YBCO trifluoroacetate (TFA) salts and (ii) a novel approach where stable colloidal solutions of preformed gold nanoparticles (5-15 nm) were homogeneously mixed with TFA-YBCO solutions. A detailed analysis of the microstructure of the films showed that in both cases, there is a strong tendency of gold nanoparticles to migrate to the film surface. However the kinetics of this migration evidences important differences and in the case of preformed nanoparticles their size remains unchanged (a few nanometers) whereas for the in-situ nanocomposites gold ripening leads to large particles (hundreds of nanometers). The grown YBCO-Au films showed good superconducting characteristics (J(c) 2 MA/cm2 at 77 K) but the absence of Au inclusions inside the YBCO matrix explains the fact that no enhancement of vortex pinning was observed. PMID:21776693

  16. Microstructure and properties of YBa2Cu3O7 - delta thin films with BaO precipitates

    NASA Astrophysics Data System (ADS)

    Tian, Y. J.; Guo, L. P.; Li, L.; Zhou, Y. Q.; Yang, Y.; Zhao, Z. X.; Xu, S. F.; Lu, H. B.; Zhou, Y. L.; Chen, Z. H.; Cui, D. F.; Yang, G. Z.

    1994-07-01

    BaO precipitates with sizes between 10-100 nm in laser ablated YBa2Cu3O7-δ (YBCO) thin films on Y-stabilized Zirconia substrates have been identified by x-ray diffraction and transmission electron microscopy. The precipitates exhibit equiaxed shapes and grow epitaxially inside and on the surface of the YBCO films, with (001)BaO plane parallel to the a,b plane of YBCO. Some of these smaller precipitates and BaO/YBCO boundaries probably provide potential pinning sites for magnetic flux lines, which might contribute to the observed increase of critical current density with magnetic field B under B≤500 G in the case of B perpendicular to the c axis of the film.

  17. Flux line lattice disorder induced by pinning centers and critical currents in YBa{sub 2}Cu{sub 3}O{sub 7-{delta}}

    SciTech Connect

    Pan, V.M.; Solovjov, V.F.; Freyhardt, H.C.

    1997-06-01

    Angular dependencies of the critical current density and the irreversible magnetization for single-crystalline and single-domain-melt-textured samples of moderately anisotropic high-T{sub c} superconductor YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} (YBCO) are measured both with transport current and magnetic techniques in the range of temperature between 77.6 K and T{sub c} and applied magnetic field up to 2 T. It is proven that the {open_quotes}cleaner{close_quotes} YBCO single crystals with no dopants and/or fine precipitates show higher critical current densities than melt-textured YBCO materials: J{sub c} up to {approximately}5.5{circ}10{sup 4} A/cm{sup 2} at 77.6 K, {mu}{sub 0}H= 1.5 T and the angle {Theta} between H and C-axis {approx}{+-}20{degrees}. It is also shown the main contribution to the net J{sub c} comes from the oxygen vacancies. The twin boundaries dramatically reduce J{sub c} at orientations close to H{parallel}C (within {+-} 20{degrees} deviation) and at intermediate values of applied field. J{sub c} (H{parallel}C) at 77.6 K and 1.5 T equals to 1.5{circ}10{sup 4} A/cm{sup 2} against 5.5{circ}10{sup 4} A/cm{sup 2} at H inclined with 6-20{degrees} angle. Thus, in contrast to melt-textured samples the J{sub c}({Theta}) dependencies for twinned single crystals reveal a remarkable minimum at H{parallel}C-axis orientation (corresponds to {Theta}=0). This angular dependence of the J{sub c} results from a combination of two contributions into the volume pinning force, F{sub p}: from point-like and planar pis. The random point-like defects are responsible for the major part of measured J{sub c} anisotropy. The role of the twin planes as extended defects, which provide a vortex locking proves out to be more ambiguous due to interference of the correlated disorder induced by the twins with point-like one, induced by the oxygen vacancies. The authors also consider influence of the defect structure of YBCO samples on dynamic properties of the FLL.

  18. Microstructure and composition of electromagnetically-characterized YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} grain boundaries

    SciTech Connect

    Babcock, S.E.; Zhang, Na; Cai, Xue Yu; Larbalestier, D.C.; Gao, Yufei; Merkle, K.L.; Kaiser, D.L.

    1991-12-01

    The electrical character (flux-pinning, Josephson junction, or resistive) of the grain boundaries in approximately twenty flux-grown YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} bicrystals was determined in previous studies. A selection of these same bicrystals now have been thinned for study by transmission and scanning transmission electron microscopy. High-spatial resolution imaging and analytical techniques reveal microstructural differences among these boundaries that are consistent with their diverse electrical characteristics. The observations offer preliminary insight into some of the feature that control the grain boundary superconducting properties and re-emphasize the very fine scale on which the grain boundary electrical character is determined. 11 refs., 6 figs.

  19. Microwave Conductivity of Laser Ablated YBa2Cu3O7-delta Superconducting Films and Its Relation to Microstrip Transmission Line Performance

    NASA Technical Reports Server (NTRS)

    Bhasin, K. B.; Warner, J. D.; Chorey, C. M.; Ebihara, B. T.; Romanofsky, R. R.; Heinen, V. O.

    1990-01-01

    We report on the values of the microwave conductivity in the normal (sigma(subN)) and superconducting (sigma*=sigma(sub1)-j sigma(sub2)) states of two laser ablated YBa2CU3O7(sigma) thin films at 35 GHz, in the temperature range from 20 to 300 K. The films 0.7 and 0.4 micrometers) were deposited on LaA10(sub3) by laser ablation. The conductivity was obtained from the microwave power transmitted through the films and assuming a two-fluid model. Values of sigma(subN) approximately 2.3 X 10(exp5) S/m at room temperature for both films, and of sigma(sub1) approximately 6.3 X 10(exp5) and 4.6 X 10(exp5) S/m at temperatures around 80 K were obtained for the 0.7 and 0.4 micrometer films respectively. For sigma(sub2) values of 4.9 X 10(exp6) and 5.4 X 10(exp6) S/m were obtained for the 0.7 and 0.4 micrometer films at 80 K. The expected conductor losses and Q-factor of a superconducting ring resonator were calculated using these conductivity values. The theoretical values were then compared with the experimental results obtained for a resonator fabricated from one of these films.

  20. Apical Cu-O bond in YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} superconductors by XAFS

    SciTech Connect

    Stern, E.A.; Qian, M.; Yacoby, Y.; Heald, S.M.; Maeda, H.

    1993-04-01

    Careful Cu K-edge X-ray absorption fine structure (XAFS) measurements on oriented powders of YBa{sub 2}CU{sub 3}O{sub 7{minus}} were made as a function of temperature, of {delta}, {Tc} method of preparation and grain size. The XAFS data were analyzed for the Cu(1) - O(4) apical bond distance distribution. AU samples indicated evidence for a double-peak in the distribution with a splitting of 0.1{Angstrom}, with the clearest case for the {delta} {approx} 0 samples occurring for the {Tc} = 89K 20{mu}m grain samples and the least clear one for the 5{mu}m grain {Tc} = 93K sample. There is no significant temperature dependence of the splitting. Because the XAFS evidence for the splitting depends on a small signal, it is prudent to verify its existence by other independent measurements.

  1. Yttrium barium heptaoxocobaltate YBaCo{sub 4}O{sub 7+{delta}}: Refinement of the structure and determination of the composition

    SciTech Connect

    Podberezskaya, N. V. Smolentsev, A. I.; Kozeeva, L. P.; Kameneva, M. Yu.; Lavrov, A. N.

    2013-09-15

    Parameters of the crystal structure of compound YBaCo{sub 4}O{sub 7} are refined. The experimental data [3917 reflections measured, 469 unique I{sub hkl}, and 420 observed reflections with I > 2{sigma}(I)] are obtained on a Bruker X8APEX automated diffractometer equipped with a CCD detector [MoK{sub {alpha}}, graphite monochromator, {theta}{sub max} = 33.09 Degree-Sign , space group P6{sub 3}mc, a = 6.3058(4) A, c = 10.2442(7) A, V = 352.77 A{sup 3}, Z = 2, d{sub calcd} = 5.404 g/cm{sup 3}, R{sub 1} = 0.0183 for 420 observed reflections and 0.0216 for all unique reflections]. The refinement shows that the occupancy factors of all sites of the space group correspond within three standard deviations to the standard values, that is, to the Y: Ba: Co: O = 1: 1: 4: 7 whole-number ratio of elements in the formula of the compound and to the absence of an aluminum impurity in the crystal.

  2. Measurement of penetration depth {lambda}(T) in YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} thin film

    SciTech Connect

    Lee, J.Y.; Lemberger, T.R.; Foltyn, S.; Wu, X.D.

    1993-06-01

    We present the magnetic penetration depth {lambda}(T) in two laser ablated YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} thin films, determined by the two-coil method. The slope of 1/{lambda}{sup 2}(T) near T{sub c}, the only exactly measurable quantity, extrapolates to 930{Angstrom} at T=0, which compares well with 830{Angstrom} in the high quality single crystal recently reported by Hardy et al., and which exhibited a linear T dependence at low T. For T {lt} 30K, we find {lambda}(T)/{lambda}(0){minus}1 = a(T/T{sub c}){sup 2} where a=0.5.

  3. Mechanisms of optical response in superconducting YBa2Cu3O7-delta thin films and grain-boundary weak links

    NASA Technical Reports Server (NTRS)

    Bhattacharya, S.; Rajeswari, M.; Takeuchi, I.; Trajanovic, Z.; Li, QI; Xi, X. X.; Venkatesan, T.

    1994-01-01

    The optical response of single grain-boundary weak links in superconducting YBCO thin films has been investigated. At temperatures well below the transition temperature, the grain boundary exhibits an optical response which is qualitatively different from transition edge response. Using a resistively shunted-junction model for the grain-boundary weak link, we find that the optical response below the transition temperature can be described by radiation induced thermal modulation of the critical currents of the weak links. The dependence on the bias current and the temperature distinguishes the weak-link optical response from the transition edge optical response. We discuss novel aspects of a potential radiation detector based on grain-boundary weak-link junctions.

  4. Controlling BaZrO3 nanostructure orientation in YBa2Cu3O{}_{7-\\delta } films for a three-dimensional pinning landscape

    NASA Astrophysics Data System (ADS)

    Wu, J. Z.; Shi, J. J.; Baca, F. J.; Emergo, R.; Wilt, J.; Haugan, T. J.

    2015-12-01

    The orientation phase diagram of self-assembled BaZrO3 (BZO) nanostructures in c-oriented YBa2Cu3O{}7-δ (YBCO) films on flat and vicinal SrTiO3 substrates was studied experimentally with different dopant concentrations and vicinal angles and theoretically using a micromechanical model based on the theory of elasticity. The organized BZO nanostructure configuration was found to be tunable, between c-axis to ab-plane alignment, by the dopant concentration in the YBCO film matrix strained via lattice mismatched substrates. The correlation between the local strain caused by the BZO doping and the global strain on the matrix provides a unique approach for controllable growth of dopant nanostructure landscapes. In particular, a mixed phase of the c-axis-aligned nanorods and the ab-plane-aligned planar nanostructures can be obtained, leading to a three-dimensional pinning landscape with single impurity doping and much improved J c in almost all directions of applied magnetic field.

  5. Deposition of high quality YBa2Cu3O(7-delta) thin films over large areas by pulsed laser ablation with substrate scanning

    NASA Technical Reports Server (NTRS)

    Davis, M. F.; Wosik, J.; Forster, K.; Deshmukh, S. C.; Rampersad, H. R.

    1991-01-01

    The paper describes thin films deposited in a system where substrates are scanned over areas up to 3.5 x 3.5 cm through the stationary plume of an ablated material defined by an aperture. These YBCO films are deposited on LaAlO3 and SrTiO3 substrates with the thickness of 90 and 160 nm. Attention is focused on the main features of the deposition system: line focusing of the laser beam on the target; an aperture defining the area of the plume; computerized stepper motor-driven X-Y stage translating the heated sampler holder behind the plume-defining aperture in programmed patterns; and substrate mounting block with uniform heating at high temperatures over large areas. It is noted that the high degree of uniformity of the properties in each film batch illustrates that the technique of pulsed laser deposition can be applied to produce large YBCO films of high quality.

  6. Rapid doubling of the critical current of Yba{sub 2}Cu{sub 3}O{sub 7-{delta}} coated conductor for viable high-speed industrial processing.

    SciTech Connect

    Leroux, M.; Kihlstrom, K. J.; Holleis, S.; Rupich, M. W.; Sathyamurthy, S.; Fleshler, S.; Sheng, H. P.; Miller, D. J.; Eley, S.; Civale, L.; Kayani, A.; Niraula, P. M.; Welp, U.; Kwok, W. -K.

    2015-11-09

    We demonstrate that 3.5-MeV oxygen irradiation can markedly enhance the in-field critical current of commercial 2nd generation superconducting tapes with an exposure time of just one second per 0.8 cm2. The speed demonstrated here is now at the level required for an industrial reel-to-reel post-processing. The irradiation is made on production line samples through the protective silver coating and does not require any modification of the growth process. From TEM imaging, we identify small clusters as the main source of increased vortex pinning.

  7. Observation of a Bulk Nodal-Gap in Overdoped Y $_{0.9} 0.9 Ca _{0.1} 0.1 Ba _{2} 2 Cu _{3} 3 O _{7-delta }$ 7 - δ Thin Films

    NASA Astrophysics Data System (ADS)

    Bachar, N.; Bechor, Y.; Gorshunov, B.; Farber, E.

    2015-04-01

    Complex conductivity of overdoped YCaBaCuO thin films was measured in Terahertz frequency using frequency and time domain methods. The films were measured in the frequency range of 3-100 cm and in the temperature range of 20-300 K. Results show a possible deviation from a pure -wave superconductor, indicated by the existence of an energy sub-gap in overdoped YCaBaCuO films. Evidence for this sub-gap appears as non-monotonic behavior of as a function of frequency followed by a sharp decrease at low frequencies, and a dip in the imaginary part of the optical conductivity multiplied by frequency, . The mentioned features were observed at energy of about 1.2 meV in 10 % Ca-doped YBCO thin films. Our complex conductivity spectra are in agreement with the theoretical prediction obtained by using a mixed symmetry order parameter within the Born limit, shown by Schürrer et al. We suggest that these observations are direct evidence for a nodal gap obtained in a -wave superconductor and can be theoretically clarified by adding an imaginary component as or to the main -wave order parameter.

  8. Superconducting properties of YaBa2Cu3O7-delta films deposited on commercial tape substrates, decorated with Pd or Ta nano-islands

    SciTech Connect

    Polat, Ozgur; Ertugrul, Memhet; Thompson, James R; Leonard, Keith J; Sinclair IV, John W; Paranthaman, Mariappan Parans; Wee, Sung Hun; Zuev, Yuri L; Xiong, X.; Selvamanickam, V.; Christen, David K; Aytug, Tolga

    2012-01-01

    To obtain an engineered surface for deposition of high-Tc superconductors, nanoscale modulations of the surface of the underlying LaMnO3 (LMO) cap layer is a potential source for generating microstructural defects in YBa2Cu3O7- (YBCO) films. These defects may improve the flux-pinning and consequently increase the critical current density, Jc. To provide such nanoscale modulation via a practical and scalable process, tantalum (Ta) and palladium (Pd) nano-islands were deposited using dc-magnetron sputtering on the surface of the cap layer of commercial metal tape templates for second-generation wires. The size and density of these nano-islands can be controlled by changing sputtering conditions such as the power and deposition time. Compared to the reference sample grown on an untreated LMO cap layer, the YBCO films grown on the LMO cap layers with Ta or Pd nano-islands exhibited improved in-field Jc performance. Atomic Force Microscopy (AFM) and Transmission Electron Microscopy (TEM) were used to assess the evolving size and density of the nano-islands.

  9. Fabriacation and properties of high-J{sub c}, biaxially aligned YBa{sub 2}Cu{sub 3}O{sub 7-delta} thick films on metallic tape ...

    SciTech Connect

    Christen, D.K.; Norton, D.P.; Goyal, A.

    1997-03-01

    We report the synthesis and properties of high-J{sub c}, biaxially aligned YBCO films deposited on thermo-mechanically textured Ni tapes. Sharply cube-textured Ni tapes, 125 {mu}m thick, were produced by mechanical rolling followed by recrystallization anneal. Short segments were coated with epitaxial oxide buffer layers, followed by fully aligned YBCO films to thicknesses of 1 to 3 {mu}m. In-plane textures of 7-10{degree} FWHM are achieved, with c-perpendicular alignment to 1{degree} FWHM. Typical zero-field J{sub c} values are in the range 5-9x10{sup 5} A/cm{sup 2} at 77 K, with strong behavior in magnetic fields comparable to that of epitaxial films on single crystal oxides. Assessment of properties necessary for a tape conductor technology are discussed.

  10. SNS Device Made With Edge-Defined Geometry

    NASA Technical Reports Server (NTRS)

    Hunt, Brian D.; Foote, Marc C.

    1992-01-01

    YBa(2)Cu(3)O(7-delta)/Au/Nb superconductor/normal-conductor/superconductor (SNS) microbridge devices fabricated using now-standard lithographic techniques and edge geometry to define normally conducting links having submicron-by-several-microns cross-sectional dimensions. Edge geometry allows current to flow only in these planes and takes advantage of longer coherence length at critical YBa(2)Cu(3)O(7-delta)/Au/Nb interface. Sensitivity to damage on edge of YBa(2)Cu(3)O(7-delta)/Au/Nb reduced.

  11. Seed crystals with improved properties for melt processing superconductors for practical applications

    DOEpatents

    Veal, Boyd W.; Paulikas, Arvydas; Balachandran, Uthamalingam; Zhong, Wei

    1997-01-01

    A method of fabricating bulk superconducting material including RBa.sub.2 Cu.sub.3 O.sub.7-.delta. comprising heating compressed powder oxides and/or carbonates of R and Ba and Cu present in mole ratios to form RBa.sub.2 Cu.sub.3 O.sub.7-.delta. in physical contact with an oxide single crystal seed to a temperature sufficient to form a liquid phase in the RBa.sub.2 Cu.sub.3 O.sub.7-.delta. while maintaining the single crystal seed solid to grow the superconducting material and thereafter cooling to provide a material including RBa.sub.2 Cu.sub.3 O.sub.7-.delta.. R is a rare earth or Y or La and the single crystal seed has a lattice mismatch with RBa.sub.2 Cu.sub.3 O.sub.7-.delta. of less than about 2% at the growth temperature. The starting material may be such that the final product contains a minor amount of R.sub.2 BaCuO.sub.5.

  12. Superconductivity and magnetism in rapidly solidified perovskites. Final report, September 1, 1988--August 31, 1991

    SciTech Connect

    O`Handley, R.C.; Kalonji, G.

    1991-12-31

    The report is divided into six parts, reflecting major thrusts of our work since 1987. The six areas are: molecular orbital theory of high {Tc} superconductivity; rapid solidification processing of oxide superconductors; time dependent magnetic and superconducting properties of these inhomogeneous materials; excess Gd in Gd{sub 1+x}Ba{sub 2-x}Cu{sub 3}O{sub 7-{delta}} perovskites; rapid solidification and directional annealing to achieve high Jc; and Mossbauer studies of T = Fe, Co and Ni site selection in YBa{sub 2}(CuT){sub 3}O{sub 7-{delta}} and GdBa{sub 2}(CuT){sub 3}O{sub 7-{delta}}.

  13. Superconductivity and magnetism in rapidly solidified perovskites

    SciTech Connect

    O'Handley, R.C.; Kalonji, G.

    1991-01-01

    The report is divided into six parts, reflecting major thrusts of our work since 1987. The six areas are: molecular orbital theory of high {Tc} superconductivity; rapid solidification processing of oxide superconductors; time dependent magnetic and superconducting properties of these inhomogeneous materials; excess Gd in Gd{sub 1+x}Ba{sub 2-x}Cu{sub 3}O{sub 7-{delta}} perovskites; rapid solidification and directional annealing to achieve high Jc; and Mossbauer studies of T = Fe, Co and Ni site selection in YBa{sub 2}(CuT){sub 3}O{sub 7-{delta}} and GdBa{sub 2}(CuT){sub 3}O{sub 7-{delta}}.

  14. Insert Coil Test for HEP High Field Magnets Using YBCO Coated Conductor Tapes

    SciTech Connect

    Lombardo, V.; Barzi, E.; Turrioni, D.; Zlobin, A.V.; /Fermilab

    2011-06-15

    The final beam cooling stages of a Muon Collider may require DC solenoid magnets with magnetic fields of 30-50 T. In this paper we present progress in insert coil development using commercially available YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} Coated Conductor. Technological aspects covered in the development, including coil geometry, insulation, manufacturing process and testing are summarized and discussed. Test results of double pancake coils operated in liquid nitrogen and liquid helium are presented and compared with the performance of YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} tape short samples.

  15. Levitation of superconducting composites

    NASA Technical Reports Server (NTRS)

    Chiang, C. K.; Turchinskaya, M.; Swartzendruber, L. J.; Shull, R. D.; Bennett, L. H.

    1991-01-01

    The inverse levitation of a high temperature superconductor polymer composite consisting of powdered quench melt growth Ba2YCu3O(7-delta) and cyanoacrylate is reported. Magnetic hysteresis loop measurements for the composite are compared to those measured for the bulk material prior to powdering. Differences in the flux pining capability between the two material forms are small but significant.

  16. The yeast tumor suppressor homologue Sro7p is required for targeting of the sodium pumping ATPase to the cell surface.

    PubMed

    Wadskog, Ingrid; Forsmark, Annabelle; Rossi, Guendalina; Konopka, Catherine; Oyen, Mattias; Goksör, Mattias; Ronne, Hans; Brennwald, Patrick; Adler, Lennart

    2006-12-01

    The SRO7/SOP1 encoded tumor suppressor homologue of Saccharomyces cerevisiae is required for maintenance of ion homeostasis in cells exposed to NaCl stress. Here we show that the NaCl sensitivity of the sro7Delta mutant is due to defective sorting of Ena1p, the main sodium pump in yeast. On exposure of sro7Delta mutants to NaCl stress, Ena1p fails to be targeted to the cell surface, but is instead routed to the vacuole for degradation via the multivesicular endosome pathway. SRO7-deficient mutants accumulate post-Golgi vesicles at high salinity, in agreement with a previously described role for Sro7p in late exocytosis. However, Ena1p is not sorted into these post-Golgi vesicles, in contrast to what is observed for the vesicles that accumulate when exocytosis is blocked in sec6-4 mutants at high salinity. These observations imply that Sro7p has a previously unrecognized role for sorting of specific proteins into the exocytic pathway. Screening for multicopy suppressors identified RSN1, encoding a transmembrane protein of unknown function. Overexpression of RSN1 restores NaCl tolerance of sro7Delta mutants by retargeting Ena1p to the plasma membrane. We propose a model in which blocked exocytic sorting in sro7Delta mutants, gives rise to quality control-mediated routing of Ena1p to the vacuole. PMID:17005914

  17. Fluctuation-induced in-plane magnetoconductivity in bilayered superconductors

    SciTech Connect

    Ramallo, M.V.; Mosqueira, J.; Vidal, F.; Pomar, A.

    1996-11-01

    In this paper the authors summarize some of their theoretical results for the paraconductivity and for the fluctuation-induced in-plane magnetoconductivity in the weak magnetic field limit of layered superconductors with several interlayer separations. Also, they briefly discuss the existing experimental data obtained in untwinned YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} crystals.

  18. Vaporization of a mixed precursors in chemical vapor deposition for YBCO films

    NASA Technical Reports Server (NTRS)

    Zhou, Gang; Meng, Guangyao; Schneider, Roger L.; Sarma, Bimal K.; Levy, Moises

    1995-01-01

    Single phase YBa2Cu3O7-delta thin films with T(c) values around 90 K are readily obtained by using a single source chemical vapor deposition technique with a normal precursor mass transport. The quality of the films is controlled by adjusting the carrier gas flow rate and the precursor feed rate.

  19. Analysis of a High-Tc Hot-Electron Superconducting Mixer for Terahertz Applications

    NASA Technical Reports Server (NTRS)

    Karasik, B. S.; McGrath, W. R.; Gaidis, M. C.

    1996-01-01

    The prospects of a YBa2Cu3O7(delta)(YBCO) hot-electron bolometer (HEB) mixer for a THz heterodyne receiver is discussed. The modeled device is a submicron bridge made from a 10 nm thick film on a high thermal conductance substrate.

  20. Cuprate-titanate superconductor and method for making

    DOEpatents

    Toreki, R.; Poeppelmeier, K.; Dabrowski, B.

    1995-05-23

    A new copper oxide superconductor of the formula Ln{sub 1{minus}x}M{sub x}Sr{sub 2}Cu{sub 3{minus}y}Ti{sub y}O{sub 7+{delta}} is disclosed, and exhibits a {Tc} of 60 K with deviations from linear metallic behavior as high as 130 K. 2 Figs.

  1. Cuprate-titanate superconductor and method for making

    DOEpatents

    Toreki, Robert; Poeppelmeier, Kenneth; Dabrowski, Bogdan

    1995-01-01

    A new copper oxide superconductor of the formula Ln.sub.1-x M.sub.x Sr.sub.2 Cu.sub.3-y Ti.sub.y O.sub.7+.delta. is disclosed, and exhibits a Tc of 60.degree. K. with deviations from linear metallic behavior as high as 130.degree. K.

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

    NASA Technical Reports Server (NTRS)

    Bhasin, Kul B. (Editor); Heinen, Vernon O. (Editor)

    1990-01-01

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

  3. Two actin-related proteins are shared functional components of the chromatin-remodeling complexes RSC and SWI/SNF.

    PubMed

    Cairns, B R; Erdjument-Bromage, H; Tempst, P; Winston, F; Kornberg, R D

    1998-11-01

    The yeast Saccharomyces cerevisiae contains two related chromatin-remodeling complexes, RSC and SWI/SNF, which are shown to share the actin-related proteins Arp7 and Arp9. Depending on the genetic background tested, arp7 delta and arp9 delta mutants are either inviable or show greatly impaired growth and Swi-/Snf- mutant phenotypes. Unlike swi/snf mutants, viable arp7 delta or arp9 delta mutants have an Spt- phenotype, suggesting that RSC affects transcription. Temperature-sensitive mutations in ARP7 and ARP9 were isolated, and the amino acid changes support the structural relationship of Arp7 and Arp9 to actin. However, site-directed mutations predicted to impair ATP binding or hydrolysis did not detectably affect Arp7 or Arp9 function. Our results suggest that actin-related proteins perform important roles in chromatin-remodeling complexes by virtue of structural rather than enzymatic similarities to actin. PMID:9844636

  4. Single-grain growth, microstructure and superconducting properties of (Sm, Eu)123 superconductors with BaCuO2-x addition

    NASA Astrophysics Data System (ADS)

    Hu, A.; Sakai, N.; Zhou, H.; Matsui, M.; Murakami, M.

    2003-01-01

    High quality (Sm0.5, Eu0.5)Ba2Cu3O7-delta single domains were grown in air with BaCuO2-x addition. It was found that a RE-Ba substitution (RE: Sm and Eu) could be effectively suppressed by a small addition of BaCuO2-x. The 94 K superconductivity with sharp transition was obtained in the composition range of 0.16 ~ 0.33 BaCuO2-x and (Sm0.5, Eu0.5)Ba2Cu3O7-delta in a molar ratio. At 77 K, a surface field of 0.8 T was trapped in a single-domain pellet of 3.2 cm diameter. A further addition of BaCuO2-x deteriorated the microstructure and degraded the superconducting performance.

  5. Experimental evidence for flux-lattice melting. [in high-Tc superconductors

    NASA Technical Reports Server (NTRS)

    Farrell, D. E.; Rice, J. P.; Ginsberg, D. M.

    1991-01-01

    A low-frequency torsional oscillator has been used to search for flux-lattice melting in an untwinned single crystal of YBa2Cu3O(7-delta). The damping of the oscillator was measured as a function of temperature, for applied magnetic fields in the range H = 0.1-2.3 T. A remarkably sharp damping peak has been located. It is suggested that the temperature of the peak corresponds to the melting point of the Abrikosov flux lattice.

  6. Melting of the Abrikosov flux lattice in anisotropic superconductors

    NASA Technical Reports Server (NTRS)

    Beck, R. G.; Farrell, D. E.; Rice, J. P.; Ginsberg, D. M.; Kogan, V. G.

    1992-01-01

    It has been proposed that the Abrikosov flux lattice in high-Tc superconductors is melted over a significant fraction of the phase diagram. A thermodynamic argument is provided which establishes that the angular dependence of the melting temperature is controlled by the superconducting mass anisotropy. Using a low-frequency torsional-oscillator technique, this relationship has been tested in untwinned single-crystal YBa2Cu3O(7-delta). The results offer decisive support for the melting proposal.

  7. Superconducting submillimeter and millimeter wave detectors

    SciTech Connect

    Nahum, M.

    1992-10-20

    The series of projects described in this dissertation was stimulated by the discovery of high temperature superconductivity. Our goal was to develop useful applications which would be competitive with the current state of technology. The high-[Tc] microbolometer was developed into the most sensitive direct detector of millimeter waves, when operated at liquid nitrogen temperatures. The thermal boundary resistance of thin YBa[sub 2]Cu[sub 3]0[sub 7-[delta

  8. Processing method for superconducting ceramics

    DOEpatents

    Bloom, Ira D.; Poeppel, Roger B.; Flandermeyer, Brian K.

    1993-01-01

    A process for preparing a superconducting ceramic and particularly YBa.sub.2 Cu.sub.3 O.sub.7-.delta., where .delta. is in the order of about 0.1-0.4, is carried out using a polymeric binder which decomposes below its ignition point to reduce carbon residue between the grains of the sintered ceramic and a nonhydroxylic organic solvent to limit the problems with water or certain alcohols on the ceramic composition.

  9. Processing method for superconducting ceramics

    DOEpatents

    Bloom, Ira D.; Poeppel, Roger B.; Flandermeyer, Brian K.

    1993-02-02

    A process for preparing a superconducting ceramic and particularly YBa.sub.2 Cu.sub.3 O.sub.7-.delta., where .delta. is in the order of about 0.1-0.4, is carried out using a polymeric binder which decomposes below its ignition point to reduce carbon residue between the grains of the sintered ceramic and a nonhydroxylic organic solvent to limit the problems with water or certain alcohols on the ceramic composition.

  10. Oncolytic adenoviruses kill breast cancer initiating CD44+CD24-/low cells.

    PubMed

    Eriksson, Minna; Guse, Kilian; Bauerschmitz, Gerd; Virkkunen, Pekka; Tarkkanen, Maija; Tanner, Minna; Hakkarainen, Tanja; Kanerva, Anna; Desmond, Renee A; Pesonen, Sari; Hemminki, Akseli

    2007-12-01

    Cancer stem cells have been indicated in the initiation of tumors and are even found to be responsible for relapses after apparently curative therapies have been undertaken. In breast cancer, they may reside in the CD44(+)CD24(-/low) population. The use of oncolytic adenoviruses presents an attractive anti-tumor approach for eradication of these cells because their entry occurs through infection and they are, therefore, not susceptible to those mechanisms that commonly render stem cells resistant to many drugs. We isolated CD44(+)CD24(-/low) cells from patient pleural effusions and confirmed stem cell-like features including oct4 and sox2 expression and Hoechst 33342 exclusion. CD44(+)CD24(-/low) cells, including the Hoechst excluding subpopulation, could be effectively killed by oncolytic adenoviruses Ad5/3-Delta24 and Ad5.pk7-Delta24. In mice, CD44(+)CD24(-/low) cells formed orthotopic breast tumors but virus infection prevented tumor formation. Ad5/3-Delta24 and Ad5.pk7-Delta24 were effective against advanced orthotopic CD44(+)CD24(-/low)-derived tumors. In summary, Ad5/3-Delta24 and Ad5.pk7-Delta24 can kill CD44(+)CD24(-/low), and also committed breast cancer cells, making them promising agents for treatment of breast cancer. PMID:17848962

  11. Fabrication, qualification and test of high Jc ROEBEL YBCO coated conductor cable for HEP magnets

    SciTech Connect

    Lombardo, V.; Barzi, E.; Turrioni, D.; Zlobin, A.V.; Long, N.J.; Badcock, R.A.

    2010-08-01

    The ROEBEL cable concept allows for a high critical current cable assembled using commercially available YBa{sub 2}Cu{sub 3}O{sub 7-{Delta}} coated conductors. this approach to cable design leads to several technological improvements if applied to the manufacture process of next generation low inductance, high current density HTS coils. A reduction in inductance proves to be extremely important when it comes to protection of coils capable of generating fields in the range of 40-50T, such as the ones needed in the last stage of the cooling channel of a muon collider. In this work several aspects are presented including the qualification and minimum requirements for YBa{sub 2}Cu{sub 3}O{sub 7-{Delta}}coated conductor in terms of 2D current density uniformity and the manufacturing process of ROEBEL cables. Test results achieved using a superconducting transformer for critical current measurements in liquid helium are shown, discussed and compared to the performance of a single YBa{sub 2}Cu{sub 3}O{sub 7-{Delta}} coated conductor tape.

  12. Thin film seeds for melt processing textured superconductors for practical applications

    DOEpatents

    Veal, Boyd W.; Paulikas, Arvydas; Balachandran, Uthamalingam; Zhong, Wei

    1999-01-01

    A method of fabricating bulk superconducting material such as RBa.sub.2 Cu.sub.3 O.sub.7-.delta. where R is La or Y comprising depositing a thin epitaxially oriented film of Nd or Sm (123) on an oxide substrate. The powder oxides of RBa.sub.2 Cu.sub.3 O.sub.7-.delta. or oxides and/or carbonates of R and Ba and Cu present in mole ratios to form RBa.sub.2 Cu.sub.3 O.sub.7-.delta., where R is Y or La are heated, in physical contact with the thin film of Nd or Sm (123) on the oxide substrate to a temperature sufficient to form a liquid phase in the oxide or carbonate mixture while maintaining the thin film solid to grow a large single domain 123 superconducting material. Then the material is cooled. The thin film is between 200 .ANG. and 2000 .ANG.. A construction prepared by the method is also disclosed.

  13. Microwave response of high transition temperature superconducting thin films

    NASA Technical Reports Server (NTRS)

    Miranda, Felix Antonio

    1991-01-01

    We have studied the microwave response of YBa2Cu3O(7 - delta), Bi-Sr-Ca-Cu-O, and Tl-Ba-Ca-Cu-O high transition temperature superconducting (HTS) thin films by performing power transmission measurements. These measurements were carried out in the temperature range of 300 K to 20 K and at frequencies within the range of 30 to 40 GHz. Through these measurements we have determined the magnetic penetration depth (lambda), the complex conductivity (sigma(sup *) = sigma(sub 1) - j sigma(sub 2)) and the surface resistance (R(sub s)). An estimate of the intrinsic penetration depth (lambda approx. 121 nm) for the YBa2Cu3O(7 - delta) HTS has been obtained from the film thickness dependence of lambda. This value compares favorably with the best values reported so far (approx. 140 nm) in single crystals and high quality c-axis oriented thin films. Furthermore, it was observed that our technique is sensitive to the intrinsic anisotropy of lambda in this superconductor. Values of lambda are also reported for Bi-based and Tl-based thin films. We observed that for the three types of superconductors, both sigma(sub 1) and sigma(sub 2) increased when cooling the films below their transition temperature. The measured R(sub s) are in good agreement with other R(sub S) values obtained using resonant activity techniques if we assume a quadratic frequency dependence. Our analysis shows that, of the three types of HTS films studied, the YBa2Cu3O(7 - delta) thin film, deposited by laser ablation and off-axis magnetron sputtering are the most promising for microwave applications.

  14. The Hsp90 molecular chaperone complex regulates maltose induction and stability of the Saccharomyces MAL gene transcription activator Mal63p.

    PubMed

    Bali, Mehtap; Zhang, Bin; Morano, Kevin A; Michels, Corinne A

    2003-11-28

    Induction of the Saccharomyces MAL structural genes encoding maltose permease and maltase requires the MAL activator, a DNA-binding transcription activator. Genetic analysis of MAL activator mutations suggested that protein folding and stability play an important role in MAL activator regulation and led us to explore the role of the Hsp90 molecular chaperone complex in the regulation of the MAL activator. Strains carrying mutations in genes encoding components of the Hsp90 chaperone complex, hsc82 Delta hsp82-T101I and hsc82 Delta cpr7 Delta, are defective for maltase induction and exhibit significantly reduced growth rates on media containing a limiting concentration of maltose (0.05%). This growth defect is suppressed by providing maltose in excess. Using epitope-tagged alleles of the MAL63 MAL activator, we showed that Mal63p levels are drastically reduced following depletion of cellular Hsp90. Overexpression ( approximately 3-fold) of Mal63p in the hsc82 Delta hsp82-T101I and hsc82 Delta cpr7 Delta strains suppresses their Mal- growth phenotype, suggesting that Mal63p levels are limiting for maltose utilization in strains with abrogated Hsp90 activity. Consistent with this, the half-life of Mal63p is significantly shorter in the hsc82 Delta cpr7 Delta strain (reduced about 6-fold) and modestly affected in the Hsp90-ts strain (reduced about 2-fold). Most importantly, triple hemagglutinin-tagged Mal63p protein is found in association with Hsp90 as demonstrated by co-immunoprecipitation. Taken together, these results identify the inducible MAL activator as a client protein of the Hsp90 molecular chaperone complex and point to a critical role for chaperone function in alternate carbon source utilization in Saccharomyces cerevisiae. PMID:14500708

  15. Comparative transport studies of ``1212'' superconductors

    SciTech Connect

    GAPUD,ALBERT; WU,JUDY; YAN,SHAOLIN; XIE,YI-YUAN; KANG,BYEONGWON; SIEGAL,MICHAEL P.; OVERMYER,DONALD L.

    2000-05-17

    HgBa{sub 2}CaCu{sub 2}O{sub 6+{delta}} (Hg-1212) thin films were fabricated by exchanging the TI cations in TlBa{sub 2}CaCu{sub 2}O{sub 7-{delta}} (Tl-1212) thin films with Hg cations, causing a 30-K increase in Tc. To determine how this exchange effects such a Tc increase, the irreversibility lines, temperature dependence of critical current density, and temperature dependence of Hall angle of Hg-1212 and T1-1212 thin films were measured and then compared. The results strongly suggest that the Tc shift is caused by a doubling of charge carrier density.

  16. Slip-Cast Superconductive Parts

    NASA Technical Reports Server (NTRS)

    Wise, Stephanie A.; Buckley, John D.; Vasquez, Peter; Buck, Gregory M.; Hicks, Lana P.; Hooker, Matthew W.; Taylor, Theodore D.

    1993-01-01

    Complex shapes fabricated without machining. Nonaqueous slip-casting technique used to form complexly shaped parts from high-temperature superconductive materials like YBa(2)Cu(3)O(7-delta). Such parts useful in motors, vibration dampers, and bearings. In process, organic solvent used as liquid medium. Ceramic molds made by lost-wax process used instead of plaster-of-paris molds, used in aqueous slip-casting but impervious to organic solvents and cannot drain away liquid medium. Organic-solvent-based castings do not stick to ceramic molds as they do to plaster molds.

  17. Structural relationships in high temperature superconductors

    SciTech Connect

    Schuller, I.K.; Segre, C.U.; Hinks, D.G.; Jorgensen, J.D.; Soderholm, L.; Beno, M.; Zhang, K.

    1987-09-01

    The recent discovery of two types of metallic copper oxide compounds which are superconducting to above 90/sup 0/K has renewed interest in the search for new high temperature superconducting materials. It is significant that both classes of compounds, La/sub 2-x/Sr/sub x/CuO/sub 4-y/ and YBa/sub 2/Cu/sub 3/O/sub 7-delta/ are intimately related to the extensively studied perovskite family. Both compounds contain highly oxidized, covalently bonded Cu-O sublattices, however, they differ in geometry. In this paper we discuss the relationship of these features to the superconducting properties. 30 refs., 6 figs.

  18. Microwave properties of high transition temperature superconducting thin films

    NASA Technical Reports Server (NTRS)

    Gordon, W. L.

    1991-01-01

    Extensive studies of the interaction of microwaves with YBa2Cu3O(7-delta), Bi-based, and Tl-based superconducting thin films deposited in several microwave substrates were performed. The data were obtained by measuring the microwave power transmitted through the film in the normal and the superconducting state and by resonant cavity techniques. The main motives were to qualify and understand the physical parameters such as the magnetic penetration depth, the complex conductivity, and the surface impedance, of high temperature superconducting (HTS) materials at microwave frequencies. Based on these parameters, the suitability of these HTS thin films is discussed for microwave applications.

  19. High-Tc superconductor coplanar waveguide filter

    NASA Technical Reports Server (NTRS)

    Chew, Wilbert; Bajuk, Louis J.; Cooley, Thomas W.; Foote, Marc C.; Hunt, Brian D.; Rascoe, Daniel L.; Riley, A. L.

    1991-01-01

    Coplanar waveguide (CPW) low-pass filters made of YBa2Cu3O(7-delta) (YBCO) on LaAlO3 substrates, with dimensions suited for integrated circuits, were fabricated and packaged. A complete filter gives a true idea of the advantages and difficulties in replacing thin-film metal with a high-temperature superconductor in a practical circuit. Measured insertion losses in liquid nitrogen were superior to the loss of a similar thin-film copper filter throughout the 0- to 9.5-GHz passband. These results demonstrate the performance of fully patterned YBCO in a practical CPW structure after sealing in a hermetic package.

  20. Development and evaluation of superconducting circuit elements

    NASA Technical Reports Server (NTRS)

    Haertling, Gene H.; Lee, Burtrand; Hsi, Dennis; Modi, Vibhakar; Marone, Matt

    1990-01-01

    An approach to the application of high Tc ceramic superconductors to practical circuit elements was developed and demonstrated. This method, known as the rigid-conductor process (RCP), involves the combination of a pre-formed, sintered, and tested superconductor material with an appropriate, rigid substrate via an epoxy adhesive which also serves to encapsulate the element from the ambient environment. Emphasis was on the practical means to achieve functional, reliable, and reproducible components. Although all of the work described in this report involved a YBa2Cu3Osub(7-x) high Tc superconductor material, the techniques developed and conclusions reached are equally applicable to other high Tc materials.

  1. Yeast Skn7p activity is modulated by the Sln1p-Ypd1p osmosensor and contributes to regulation of the HOG pathway.

    PubMed

    Ketela, T; Brown, J L; Stewart, R C; Bussey, H

    1998-09-01

    Activation and control of the yeast HOG (High Osmolarity Glycerol) MAP kinase cascade is accomplished, in part, by a two-component sensory-response circuit comprised of the osmosensing histidine protein kinase Sln1p, the phospho-relay protein Ypd1p, and the response regulator protein Ssk1p. We found that deletion of SLN1 and/or YPD1 reduces reporter gene transcription driven by a second two-component response regulator -- Skn7p. The effect of sln1delta and ypd1delta mutations upon Skn7p activity is dependent on a functional two-component phosphorylation site (D427) in Skn7p, suggesting that Sln1p and Ypd1p may act as phosphodonors for Skn7p. We also observed that loss of PTC1 (a protein serine/threonine phosphatase implicated in negative control of the HOG pathway) in a skn7delta background results in severely retarded growth and in morphological defects. Deletion of either PBS2 or HOG1 alleviates the slow growth phenotype of ptc1delta skn7delta cells, suggesting that Skn7p may participate, in concert with known regulatory components, in modulating HOG pathway activity. The contribution of Skn7p to HOG pathway regulation appears to be modulated by the receiver domain, since non-phosphorylatable Skn7pD427N is unable to fully restore growth to ptc1/skn7 cells. PMID:9790591

  2. Development of mixed conducting dense nickel/Ca-doped lanthanum zirconate cermet for gas separation application

    SciTech Connect

    Nag, S.; Mukhopadhyay, S.; Basu, R.N.

    2012-03-15

    Highlights: Black-Right-Pointing-Pointer Phase pure La{sub 1.95}Ca{sub 0.05}Zr{sub 2}O{sub 7-{delta}} (LCZ) material is prepared by combustion synthesis. Black-Right-Pointing-Pointer LCZ and Ni-LCZ bulk samples are prepared with theoretical density close to 100%. Black-Right-Pointing-Pointer Bulk electrical conductivity {approx}400 S/cm is obtained for Ni-LCZ cermet at 750 Degree-Sign C. -- Abstract: La{sub 1.95}Ca{sub 0.05}Zr{sub 2}O{sub 7-{delta}} (LCZ) and Ni-LCZ cermet have been prepared by combustion synthesis and conventional solid state mixing methods respectively. Both the materials are sintered in air and controlled atmosphere (5% H{sub 2} in Ar). The density obtained for the material sintered at 1400 Degree-Sign C in controlled atmosphere is found to be more than 99.5%. This sintering temperature (1400 Degree-Sign C) is considered to be much lower compared to the conventional sintering temperature. The corresponding total conductivity for such Ni-LCZ cermet materials is {approx}400 S/cm measured at 750 Degree-Sign C having 40 vol% of Ni and 60 vol% LCZ.

  3. Anomalous ion-channeling behavior across the superconducting transition in high-T(sub c) materials

    NASA Astrophysics Data System (ADS)

    Rehn, L. E.; Sharma, R. P.; Baldo, P. M.; Liu, J. Z.

    1989-07-01

    Axial channeling scans with minimum RBS yields of less than or = 2 percent were obtained for 1.5 MeV He-4 ions incident along the c-axis in YBa2Cu3O(7-delta) and ErBa2Cu3O(7-delta) single crystals. Large variations in the FWHM of the (001) channeling dip were observed for temperatures between 30 and 300 K. An abrupt, (approx.) 8 percent increase was measured as the temperature was lowered through the superconducting transition T(sub c); the rela tive increase across T(sub c) in the width of the axial dip was even larger for angles of incidence less than the critical angle. A simple analytical procedure for polyatomic materials yields isotropic, average thermal vibrational amplitudes that agree well with considerably less precise neutron powder diffraction results on sintered samples. The individual contribution to the angular channeling dip from the row of Er and Ba atoms parallel to the c-axis can be isolated in the RBS scans of the Er compound. This separation reveals normal (Debye-type) behavior for atoms in the Er-Ba row, demonstrating that the anomalous changes are due solely to atomic displacements in the Cu-O row. Finally, x ray studies using specimens with different O stoichiometries reveal that the anomalous change in the FWHM shifts in temperature in direct proportion to the change in T(sub c).

  4. Neutron diffraction studies on ABO3 (A=Lanthanum, Strontium, B=Iron, Cobalt , Nickel, Copper, Manganese, Titanium) perovskite used in solid oxide fuel cell (SOFC) and double perovskite Barium2YttriumRuthenium0.85Copper0.15Oxygen6 superconductor

    NASA Astrophysics Data System (ADS)

    Cai, Qingsheng

    ABO3(A=La, Sr, B=Fe, Co, Ni, Cu, Mn, Ti) perovskites are of great interest due to their mixed electronic and oxygen ion conductivity. They are candidates for the electrodes of SOFCs. The mixed conductivity can be enhanced through the substitution of La3+ by Sr2+ at A sites, and the substitution of Fe3+ by other transition metal ions at B sites. The charge imbalance and overall charge neutrality can be maintained by the presence of charged oxygen vacancies and mixed valence state ions at the B sites. These point defects are the origin of the mixed electronic and oxygen ion conductivity. This study investigates the effects of substitutions at A sites and/or B sites on the crystal and magnetic structure, oxygen vacancies, and the thermal expansion coefficients at different temperatures and gaseous environment. The oxygen vacancy concentration can relax the perovskite distortion and has a close relationship with the magnetic properties. La0.6Sr0.4FeO3-delta, La0.6Sr0.4Fe0.8Co0.2O3-delta , and La0.8Sr0.2Fe0.8Co0.2O 3-delta can be good candidates for the cathodes of SOFCs at intermediate temperature. The double perovskite Ba2YRu0.85Cu0.15O 6 superconductor and a mixture of 5wt% YBa2Cu3O 7-delta and undoped Ba2YRuO6 were investigated with the aid of neutron diffraction. The 1:1 B site ordering is observed and long range antiferromagnetic ordering of the Ru sublattice with a type I magnetic structure appears when the temperature is below 38K. An incommensurate antiferromagnetic ordering of Cu is observed in the temperature range 38K-85K. This ordering is not seen in undoped material. The decomposition of Cu-doped Ba2YRuO6 into undoped Ba 2YRuO6 and YBa2Cu3O7-delta is not seen. YBa2Cu3O7-delta is not stable at the temperature used to prepare the Cu-doped Ba2YRuO6 superconductor. These results confirm the presence of superconductivity without CuO2 planes.

  5. Synthesis, Characterization, and Thermoelectric Power Study of Thallium-Based High Critical Transition Temperature Superconductors

    NASA Astrophysics Data System (ADS)

    Xin, Ying

    New Tl-based 1212 type superconductors, 100 K (Tl_{0.8}Pb_ {0.2})-Sr_2(R,Sr)Cu _2O_{7-delta } and 110 K TlSr_2(Ca,Cr)Cu _2O_{7-delta } have been synthesized and studied on superconductivity and crystal structure. Systematical study on the thallium -based nominal MTlBaCuO_{rm x } (M = Zn, Cd, and Hg), TlSr_2 (R,Sr)Cu_2O_ {rm x} (R = rare earths), and Tl _2M_{0.2} Ba_2Ca_2Cu _3O_{rm x} (M = Na, K, Rb, Cr, Re, Zn, Cd, Hg, Se, and Te) samples have been conducted. The investigations were performed by resistance and ac susceptibility measurements, and powder x-ray diffraction. The addition of Zn, Cd, or Hg into Tl-Ba-Cu-O has some remarkable influences on superconductivity and mechanical properties as well as the required preparation condition. For the Tl(Tl,Pb) -Sr-R-Cu-O 1212 type system the optimum composition and the elemental effect of different rare earths are discussed and concluded in terms of the average Cu valence in the CuO_2 plane and the ionic radii of the rare earths. The partial substitution of Pb for Tl raises the Tc in TlSr_2(R,Sr)Cu _2O_{rm x} by about 10 degrees. High quality Tl-(M) -Ba-Ca-Cu-O 2223 superconductors were synthesized by a novel preparation procedure. The 2223 material with Tc of about 120 K and phase purity greater than 95% exhibits much improved mechanical properties. A convenient and reliable thermoelectric power measurement apparatus has been established. Measurements on the 1212 phase TlSr_2(Er _{rm 1-y}Sr_ {rm y})Cu_2O _{7-delta} and 2223 phase Tl_2M_{0.2 }Ba_2Ca_2 Cu_3O_{10 -delta} were carried out. The results show that the hole concentration in the 1212 phase plays a crucial rule on charge transport properties and superconductivity. It is possible that two-band conduction is involved in the charge transport at normal state for the 2223 phase.

  6. Tetragonal YBaFe{sub 4}O{sub 7.0}: A stoichiometric polymorph of the '114' ferrite family

    SciTech Connect

    Duffort, V.; Caignaert, V.; Pralong, V.; Barrier, N.; Raveau, B.; Avdeev, M.; Zheng, H.; Mitchell, J.F.

    2012-07-15

    The exploration of the phase diagram of the ferrite YBaFe{sub 4}O{sub 7+{delta}} versus the oxygen content {delta} and temperature shows the complex crystal chemistry of this system. Besides the cubic form (F4 Macron 3m), which is observed up to 600 Degree-Sign C and for 0<{delta}{<=}0.65, a stoichiometric tetragonal form ({delta}=0) is isolated below 300 Degree-Sign C that is stable only in the absence of oxidizing atmosphere. The resolution of the structure of this new YBaFe{sub 4}O{sub 7.0} form, from combined neutron and synchrotron data, in the space group I4 Macron , shows significant displacements of the atoms with respect to the cubic form, especially concerning the oxygen atoms surrounding the barium cations. The decrease of several Ba-O distances around the underbonded barium cations is explained by the existence of hybridized Ba{sup (2-{delta})+}-O{sup 2-}-Fe{sup (2+{delta})+} bonds, in agreement with Moessbauer spectroscopy. The role of coulombic repulsions in the [Fe{sub 4}O] and [Fe{sub 4}] tetrahedra of the [Fe{sub 4}]{sub {infinity}} sublattice on the structural transition is also discussed. - Graphical abstract: A new form of YBaFe{sub 4}O{sub 7} '114' ferrite which is only stable in oxygen free atmosphere, even at room temperature has been prepared. This new ferrite has its structure closely related to the cubic form YBaFe{sub 4}O{sub 7+{delta}} but differently from the latter which is stable for 0<{delta}<0.65, it requires a rigorous oxygen 'O{sub 7}' stoichiometry, i.e., {delta}=0. We describe herein the phase diagram of the oxides YBaFe{sub 4}O{sub 7+{delta}} and we determine the structure of this new YBaFe{sub 4}O{sub 7.0} form, from combined neutron and synchrotron data. Highlights: Black-Right-Pointing-Pointer Oxygen stoichiometry control in '114' YBaFe{sub 4}O{sub 7+d} ferrites. Black-Right-Pointing-Pointer A new structural transition leading to a new form of YBaFe{sub 4}O{sub 7+d} '114' ferrite for d=0. Black

  7. Pyrochlore-type catalysts for the reforming of hydrocarbon fuels

    SciTech Connect

    Berry, David A.; Shekhawat, Dushyant; Haynes, Daniel; Smith, Mark; Spivey, James J.

    2012-03-13

    A method of catalytically reforming a reactant gas mixture using a pyrochlore catalyst material comprised of one or more pyrochlores having the composition A.sub.2-w-xA'.sub.wA''.sub.xB.sub.2-y-zB'.sub.yB''.sub.zO.sub.7-.DELTA.. Distribution of catalytically active metals throughout the structure at the B site creates an active and well dispersed metal locked into place in the crystal structure. This greatly reduces the metal sintering that typically occurs on supported catalysts used in reforming reactions, and reduces deactivation by sulfur and carbon. Further, oxygen mobility may also be enhanced by elemental exchange of promoters at sites in the pyrochlore. The pyrochlore catalyst material may be utilized in catalytic reforming reactions for the conversion of hydrocarbon fuels into synthesis gas (H.sub.2+CO) for fuel cells, among other uses.

  8. Application of Z-contrast imaging to obtain column-by-column spectroscopic analysis of materials

    SciTech Connect

    Browning, N.D.; Pennycook, S.J.

    1993-01-01

    Z-contrast imaging has been shown to be an effective method for obtaining a high-resolution image from a scanning transmission electron microscope (STEM). The incoherent nature of the high-angle scattering makes image interpretation straightforward and intuitive with the resolution limited only by the 2.2 {Angstrom} electron probe. The optimum experimental conditions for Z-contrast imaging also coincide with those used for analytical microscopy, enabling microanalysis to be performed with the same spatial resolution as the image. The detection limits afforded by a parallel detection system for electron energy loss spectroscopy (EELS) allows column-by-column core-loss spectroscopy to be performed using the Z-contrast image to position the electron probe. Preliminary results from the study of YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} illustrate the spatial resolution available with this technique and the potential applications for materials science.

  9. Laser writing and rewriting on YBa2Cu3O7 films

    NASA Astrophysics Data System (ADS)

    Shen, Y. Q.; Freltoft, T.; Vase, P.

    1991-09-01

    High-resolution patterning (4 microns) has been achieved on epitaxial thin films of the high-temperature superconductor YBa2Cu3O(7-delta) using laser writing. A focused laser beam is applied to write semiconducting patterns on superconducting films in a vacuum or in a nitrogen atmosphere. The semiconducting patterns are shown to be formed by a reduction of the oxygen content due to local heating caused by the laser beam. The process does not cause any structural damage and does not change the surface morphology. When reapplying the same laser beam and rewriting the film in an oxygen atmosphere, it is possible to restore the superconductive properties. The application of this method for production of superconducting microelectronic circuits is discussed.

  10. Coplanar waveguide microwave filter of YBa2Cu3O7

    NASA Technical Reports Server (NTRS)

    Chew, Wilbert; Riley, A. L.; Rascoe, Daniel L.; Hunt, Brian D.; Foote, Marc C.; Cooley, Thomas W.; Bajuk, Louis J.

    1991-01-01

    Thin film low-pass microwave filters have been made with laser-ablated YBa2Cu3O(7-delta) (YBCO) deposited on LaAlO3 substrates, using a coplanar waveguide structure. The coplanar waveguide sections had dimensions suited for integrated circuits. Measured losses in liquid nitrogen were superior to the loss in a similar thin-film copper filter throughout the 0 to 9.5 GHz pass-band. A simple transmission-line model is adequate for filter design using YBCO films with repeatable characteristics. The measured filters demonstrate the performance of fully patterned YBCO after sealing in space-qualifiable hermetic packages. Five packaged filters of this design were delivered to the Naval Research Laboratory as candidates for space flight in the High Temperature Superconductivity Space Experiment.

  11. Coplanar waveguide microwave filter of YBa2Cu3O7

    NASA Astrophysics Data System (ADS)

    Chew, Wilbert; Riley, A. L.; Rascoe, Daniel L.; Hunt, Brian D.; Foote, Marc C.; Cooley, Thomas W.; Bajuk, Louis J.

    1991-07-01

    Thin film low-pass microwave filters have been made with laser-ablated YBa2Cu3O(7-delta) (YBCO) deposited on LaAlO3 substrates, using a coplanar waveguide structure. The coplanar waveguide sections had dimensions suited for integrated circuits. Measured losses in liquid nitrogen were superior to the loss in a similar thin-film copper filter throughout the 0 to 9.5 GHz pass-band. A simple transmission-line model is adequate for filter design using YBCO films with repeatable characteristics. The measured filters demonstrate the performance of fully patterned YBCO after sealing in space-qualifiable hermetic packages. Five packaged filters of this design were delivered to the Naval Research Laboratory as candidates for space flight in the High Temperature Superconductivity Space Experiment.

  12. Application of ceramic superconductors in high speed turbines

    NASA Technical Reports Server (NTRS)

    Mcmichael, C. K.; Lamb, M. A.; Lin, M. W.; Ma, K. B.; Chu, W. K.

    1992-01-01

    A turbine system was modified to adapt melt textured YBa2Cu3O(7-delta) (YBCO) with high energy permanent magnets to form a hybrid superconducting magnetic bearing (HSMB). The HSMB/turbine prototype has achieved a static axial thrust capacity exceeding 41 N/sq cm (60 psi) and a radial magnetic stiffness of 7 N/mm in a field cooled state at 77 K. A comparison was made between different configurations of magnets and superconductor for radial stability, axial instability, and force hystereses. This systematic study lead to a greater understanding of the interactions between YBCO and high energy permanent magnets to define design parameters for high rotational devices using the HSMB design.

  13. Suppression of Vortex Channeling in Meandered YBa2Cu3O7-δ Grain Boundaries

    SciTech Connect

    Durrell, J. H.; Feldmann, D. M.; Cantoni, Claudia

    2007-01-01

    We report on the in-plane magnetic field (H) dependence of the critical current density (J{sub c}) in meandered and planar single grain boundaries (GBs) isolated in YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO) coated conductors. The meandered boundaries resulted from metal-organic deposition, and the planar boundaries resulted from physical vapor deposition. The J{sub c}(H) properties of the planar GB are consistent with those previously seen in single GBs of YBCO films grown on SrTiO{sub 3} bicrystals. In the straight boundary, a characteristic flux channeling regime when H is oriented near the GB plane, associated with a reduced J{sub c}, is seen. The meandered GB does not show vortex channeling since it is not possible for a sufficient length of vortex line to lie within it.

  14. Characterization of the Structure of Y-Ba-Cu-O Coated Conductors

    SciTech Connect

    Kung, H.H.; Foltyn, S.R.; Arendt, P.N.; Maley, M.P.

    1998-09-13

    Transmission electron microscopy (TEM) has been applied to the microstructural investigation of YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO) thick films deposited on polycrystalline Ni-based metal substrates by pulsed laser deposition. The films were found to be strongly textured with c-axis oriented grains aligned perpendicular to the substrates. Despite the large average in-plane misorientation, as was estimated from selected area electron diffraction and x-ray diffraction, TEM inspection reveals colonies of submicron-sized grains with low angle tilt grain boundaries. The linkage of the colony structures may provide a continuous percolation pathway for the supercurrent transport in YBCO, which may provide the mechanism for the higher than expected critical current density J{sub c}. Periodic arrays of grain boundary dislocations were observed, which may serve as effective flux pinners.

  15. Spin dynamics and implications for superconductivity: Some problems with the d-wave scenario

    SciTech Connect

    Levin, K.; Zha, Y.; Radtke, R.J.; Si, Q.; Norman, M.R.; Schuttler, H.B.

    1993-09-01

    We review the spin dynamics of the normal state of the cuprates with special emphasis on neutron data in both the YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} and La{sub 2-x}Sr{sub x}CuO{sub 4} systems. When realistic models of the Fermi surface shapes are incorporated, along with a moderate degree of spin fluctuations, we find good semi-quantiative agreement with experiment for both cuprates. Building on the success of this Fermi-liquid-based scheme, we explore the implications for d-wave pairing from a number of vantage points. We conclude that our present experimental and theoretical understanding is inadequate to confirm or refute the d-wave scenario.

  16. Comparison between the magnetic and transport critical current densities in high critical current density melt-textured yttrium barium copper-oxide

    NASA Technical Reports Server (NTRS)

    Gao, L.; Meng, R. L.; Xue, Y. Y.; Hor, P. H.; Chu, C. W.

    1991-01-01

    Using a recently developed pulsed critical current density (Jc) measuring system, the Jc of the high-Jc melt-textured YBa2Cu3O(7-delta) (Y123) bulk samples has been determined. I-V curves with a voltage resolution of 0.5 microV were obtained, and transport Jc's along the a-b plane as high as 7.2 x 10 to the 4th A/sq cm were extracted. These results are comparable to the values obtained magnetically. On the other hand, transport Jc along the c axis were found to be two orders of magnitude smaller, even though the magnetic Jc along the c axis is only about five times smaller than Jc along the a-b plane. It is suggested that for the high-temperature superconducting materials which are highly anisotropic, caution should be taken when using the nontransport magnetic methods to determine Jc.

  17. Hybrid Superconducting Magnetic Bearing (HSMB) for high load devices

    NASA Technical Reports Server (NTRS)

    Mcmichael, C. K.; Ma, K. B.; Lamb, M. A.; Lin, M. W.; Chow, L.; Meng, R. L.; Hor, P. H.; Chu, W. K.

    1992-01-01

    Lifting capacities greater than 41 N/cm(exp 2) (60 psi) at 77 K have been achieved with a new type of levitation (hybrid) using a combination of permanent magnets and high quality melt-mixtured YBa2Cu3O(7-delta) (YBCO). The key concept of the hybrid superconducting magnetic bearing (HSMB) is the use of strong magnetic repulsion and attraction from permanent magnets for high levitation or suspension forces in conjunction with a superconductor's flux pinning characteristics to counteract the inherent instabilities in a system consisting of magnets only. To illustrate this concept, radial and axial forces between magnet/superconductor, magnet/magnet, and magnet/superconductor/magnet, were measured and compared for the thrust bearing configuration

  18. Superconducting Microwave Electronics at Lewis Research Center

    NASA Technical Reports Server (NTRS)

    Warner, Joseph D.; Bhasin, Kul B.; Leonard, Regis F.

    1991-01-01

    Over the last three years, NASA Lewis Research Center has investigated the application of newly discovered high temperature superconductors to microwave electronics. Using thin films of YBa2Cu3O7-delta and Tl2Ca2Ba2Cu3Ox deposited on a variety of substrates, including strontium titanate, lanthanum gallate, lanthanum aluminate and magnesium oxide, a number of microwave circuits have been fabricated and evaluated. These include a cavity resonator at 60 GHz, microstrip resonators at 35 GHz, a superconducting antenna array at 35 GHz, a dielectric resonator at 9 GHz, and a microstrip filter at 5 GHz. Performance of some of these circuits as well as suggestions for other applications are reported.

  19. Analysis and Optimization of Thin Film Ferroelectric Phase Shifters

    NASA Technical Reports Server (NTRS)

    Romanofsky, Robert R.; VanKeuls, Fred W.; Warner, Joseph D.; Mueller, Carl H.; Alterovitz, Samuel A.; Miranda, Felix A.; Qureshi, A. Haq; Romanofsky, Robert R. (Technical Monitor)

    2000-01-01

    Microwave phase shifters have been fabricated from (YBa2Cu3O(7-delta) or Au)/SrTiO3 and Au/Ba(x)Sr(1-x)TiO3 films on LaAlO3 and MgO substrates. These coupled microstrip devices rival the performance of their semiconductor counter-parts parts at Ku- and K-band frequencies. Typical insertion loss for room temperature ferroelectric phase shifters at K-band is approximately equal 5 dB. An experimental and theoretical investigation of these novel devices explains the role of the ferroelectric film in overall device performance. A roadmap to the development of a 3 dB insertion loss phase shifter that would enable a new type of phased array antenna is discussed.

  20. Fast neutron irradiation effects on magnetization relaxation in YBCO single crystals

    SciTech Connect

    Lensink, J.G.; Griessen, R. . Faculty of Physics and Astronomy); Wiesinger, H.P.; Sauerzopf, F.M.; Weber, H.W. ); Crabtree, G.W. )

    1991-07-01

    A high-quality YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} single crystal has been investigated by torque magnetometry prior to and following fast neutron irradiation to a fluence of 2{times}10{sup 21} m{sup {minus}2} (E > 0.1 MeV). In addition to large enhancements of the critical current densities, which have been observed in similar form previously by Sauerzopf et al, we find a dramatic change in the relaxation behavior following irradiation. At low temperatures ({le} 50 k) the relaxation rates are lowered by factors up to 4 in the irradiated state in a magnetic field of 1.5 T. At higher temperatures, on the other hand, they are enhanced compared to the unirradiated state. Both before and after irradiation, the magnetization relaxation follows a logarithmic time dependence, which we ascribe to thermally activated flux motion.

  1. Miniaturized microstrip multipole low-pass filters using high-temperature superconducting YBa2Cu3O7-x thin films

    NASA Astrophysics Data System (ADS)

    Kim, Jeha; Kang, Kwang-Yong; Han, Seok K.; Lee, Sang Yeol; Ahn, Dal

    1995-09-01

    We have designed the microstrip-type multipole (7-pole and 9-pole) lowpass filters consisting of both transmission lines and open stubs. The filters were fabricated on high temperature superconducting (HTS) YBa2Cu3O7-(delta ) (YBCO) thin films grown on MgO(100) substrates by pulsed laser deposition. For 7-pole lowpass filter, the measured insertion losses were within 0.5 dB, and up to 8 GHz the passband shows very flat with ripples of less than 0.05 dB. For 9-pole filter, we observed the insertion loss of 5.0 dB and the ripples of 0.64 dB. The skirt became steep and the off-band rejection increased large as the number of poles increases.

  2. Enhanced flux pinning in MOCVD-YBCO films through Zr-additions:Systematic feasibility studies

    SciTech Connect

    Aytug, Tolga; Paranthaman, Mariappan Parans; Specht, Eliot D; Kim, Kyunghoon; Zhang, Yifei; Cantoni, Claudia; Zuev, Yuri L; Goyal, Amit; Christen, David K; Maroni, Victor A.

    2009-01-01

    Systematic effects of Zr additions on the structural and flux pinning properties of YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO) films deposited by metal-organic chemical vapor deposition (MOCVD) have been investigated. Detailed characterization, conducted by coordinated transport, x-ray diffraction, scanning and transmission electron microscopy analyses, and imaging Raman microscopy have revealed trends in the resulting property/performance correlations of these films with respect to varying mole percentages (mol%) of added Zr. For compositions {le} 7.5 mol%, Zr additions lead to improved in-field critical current density, as well as extra correlated pinning along the c-axis direction of the YBCO films via the formation of columnar, self-assembled stacks of BaZrO{sub 3} nanodots.

  3. Design and performance of a high-Tc superconductor coplanar waveguide filter

    NASA Technical Reports Server (NTRS)

    Chew, Wilbert; Riley, A. L.; Rascoe, Daniel L.; Hunt, Brian D.; Foote, Marc C.; Cooley, Thomas W.; Bajuk, Louis J.

    1991-01-01

    The design of a coplanar waveguide low-pass filter made of YBa2Cu3O(7-delta) (YBCO) on an LaAlO3 substrate is described. Measurements were incorporated into simple models for microwave CAD analysis to develop a final design. The patterned and packaged coplanar waveguide low-pass filter of YBCO, with dimensions suited for integrated circuits, exhibited measured insertion losses when cooled in liquid nitrogen superior to those of a similarly cooled thin-film copper filter throughout the 0 to 9.5 GHz passband. Coplanar waveguide models for use with thin-film normal metal (with thickness either greater or less than the skin depth) and YBCO are discussed and used to compare the losses of the measured YBCO and copper circuits.

  4. Enhanced flux pinning in MOCVD-YBCO films through Zr additions : systematic feasibility studies.

    SciTech Connect

    Aytug, T.; Paranthaman, M.; Specht, E. D.; Zhang, Y.; Kim, K.; Zuev, Y. L.; Cantoni, C.; Goyal, A.; Christen, D. K.; Maroni, V. A.; Chen, Y.; Selvamanickam, V.; ORNL; SuperPower, Inc.

    2010-01-01

    Systematic effects of Zr additions on the structural and flux pinning properties of YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO) films deposited by metal-organic chemical vapor deposition (MOCVD) have been investigated. Detailed characterization, conducted by coordinated transport, x-ray diffraction, scanning and transmission electron microscopy analyses, and imaging Raman microscopy have revealed trends in the resulting property/performance correlations of these films with respect to varying mole percentages (mol%) of added Zr. For compositions {le} 7.5 mol%, Zr additions lead to improved in-field critical current density, as well as extra correlated pinning along the c-axis direction of the YBCO films via the formation of columnar, self-assembled stacks of BaZrO{sub 3} nanodots.

  5. Transmission Electron Microscope Study on Electrodeposited Gd2O3 and Gd2Zr2O7 Buffer Layers forYBa2Cu307-..delta.. Superconductors

    SciTech Connect

    Zhao, W.; Norman, A.; Phok, S.; Bhattacharya, R.

    2008-01-01

    We have investigated the microstructures of electrodeposited Gd{sub 2}O{sub 3} (GO) and Gd{sub 2}Zr{sub 2}O{sub 7} (GZO) buffer layers for YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO) superconductors with conventional transmission electron microscopy (TEM). A high density of nanoscale voids was present in the GZO buffer layers. No voids were observed in GO buffer layers grown on GZO. YBCO superconductor grown on the GO/GZO buffer layer structure produced a critical current density (J{sub c}) of 3.3 x 10{sup 6} A/cm{sup 2} at 77 K in zero field.

  6. Effect of electronic reconstruction on cuprate-manganite spin switches.

    SciTech Connect

    Liu, Y.; Visani, C.; Nemes, N. M.; Fitzsimmons, M. R.; Zhu, L. Y.; Tornos, J.; Zhernenkov, M.; Hoffmann, A.; Leon, C.; Santamaria, J.; te Velthuis, S. G. E.

    2012-01-01

    We examine the anomalous inverse spin switch behavior in La{sub 0.7}Ca{sub 0.3}MnO{sub 3}(LCMO)/YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO)/LCMO trilayers by combined transport studies and polarized neutron reflectometry. Measuring magnetization profiles and magnetoresistance in an in-plane rotating magnetic field, we prove that, contrary to many accepted theoretical scenarios, the relative orientation between the two LCMO's magnetizations is not sufficient to determine the magnetoresistance. Rather the field dependence of magnetoresistance is explained by the interplay between the applied magnetic field and the (exponential tail of the) induced exchange field in YBCO, the latter originating from the electronic reconstruction at the LCMO/YBCO interfaces.

  7. Buffer layers for high-Tc thin films on sapphire

    NASA Technical Reports Server (NTRS)

    Wu, X. D.; Foltyn, S. R.; Muenchausen, R. E.; Cooke, D. W.; Pique, A.; Kalokitis, D.; Pendrick, V.; Belohoubek, E.

    1992-01-01

    Buffer layers of various oxides including CeO2 and yttrium-stabilized zirconia (YSZ) have been deposited on R-plane sapphire. The orientation and crystallinity of the layers were optimized to promote epitaxial growth of YBa2Cu3O(7-delta) (YBCO) thin films. An ion beam channeling minimum yield of about 3 percent was obtained in the CeO2 layer on sapphire, indicating excellent crystallinity of the buffer layer. Among the buffer materials used, CeO2 was found to be the best one for YBCO thin films on R-plane sapphire. High Tc and Jc were obtained in YBCO thin films on sapphire with buffer layers. Surface resistances of the YBCO films were about 4 mOmega at 77 K and 25 GHz.

  8. Pyrochlore catalysts for hydrocarbon fuel reforming

    DOEpatents

    Berry, David A.; Shekhawat, Dushyant; Haynes, Daniel; Smith, Mark; Spivey, James J.

    2012-08-14

    A method of catalytically reforming a reactant gas mixture using a pyrochlore catalyst material comprised of one or more pyrochlores having the composition A2B2-y-zB'yB"zO7-.DELTA., where y>0 and z.gtoreq.0. Distribution of catalytically active metals throughout the structure at the B site creates an active and well dispersed metal locked into place in the crystal structure. This greatly reduces the metal sintering that typically occurs on supported catalysts used in reforming reactions, and reduces deactivation by sulfur and carbon. Further, oxygen mobility may also be enhanced by elemental exchange of promoters at sites in the pyrochlore. The pyrochlore catalyst material may be utilized in catalytic reforming reactions for the conversion of hydrocarbon fuels into synthesis gas (H2+CO) for fuel cells, among other uses.

  9. International Conference on Infrared and Millimeter Waves, 17th, California Inst. of Technology, Pasadena, Dec. 14-17, 1992, Conference Digest

    NASA Astrophysics Data System (ADS)

    Temkin, Richard J.

    Consideration is given to Smith-Purcell radiation at submillimeter and far-infrared wave-lengths; coherent transition radiation; an effect of spin excitations on the infrared-active phonons in YBa2Cu4O8 and YBa2Cu3O7-delta superconductors; analysis of partially open cavity resonators using complex eigenmodes; mode-coupling in varying-radius coaxial waveguides; a second-harmonic magnicon amplifier experiment; and nonlinear analysis of a magnicon output cavity. Consideration is also given to progress in quasi-optical power combining; the planar varactor diode development; very high frequency electron spin resonance; first results on a 110 GHz evacuated transmission line; effective conversion of high waveguide modes to eigenwaves of open mirror lines; electron trapping in relativistic gyro-devices; and a compact relativistic electron beam source for generation of far infrared radiation. (No individual items are abstracted in this volume)

  10. Far-Infrared Studies of Strongly Correlated Electron Systems

    NASA Astrophysics Data System (ADS)

    George, Anita

    1995-01-01

    Results of far-infrared and IR reflection measurements of Y_{1-x}Pr_ {x}Ba_2Cu _3O_{7-delta} , U_{1-x}Th _{x}NiSn and FeSi are presented. The experiments were performed over a spectral range of 10 -3000 cm^{-1} and a temperature range of 10-300 K using the technique of fast Fourier transform spectroscopy. The films of the Y_{1 -x}Pr_{x}Ba _2Cu_3O _{7-delta} series were grown using a laser ablation technique and included both superconducting and insulating samples. A number of phonon modes were identified in the reflectance spectrum of these compounds. The optical measurements did not show evidence of a BCS gap in the superconducting compounds but were consistent with the resistivity behavior of the samples. The results of the reflectance measurements on U_{1-x}Th_ {x}NiSn alloys are consistent with the semiconducting-to-metallic transition observed in these materials. Four phonon lines were observed in the reflectance spectra at all temperatures. In addition, a temperature and frequency dependent mode was observed at low frequencies. From the conductivity calculations a decrease in the oscillator strength was observed at low temperatures suggesting a partial destruction of the semiconducting gap. The reflectance measurements of FeSi were performed over the spectral range of 10-700 cm^{ -1}. The reflectance shows an unusual temperature dependence between 129 and 95 K, a range where the resistivity shows very little change. This suggests that a new phenomenon might be occurring in this temperature range. Two phonon modes were identified in the conductivity spectra at 200 and 325 cm^{-1}.

  11. Aspects of nodal quasiparticle transport in high-Tc superconductors

    NASA Astrophysics Data System (ADS)

    Smith, Michael F.

    Various low-temperature thermodynamic and transport properties of high TC superconductors at temperatures well below TC are studied theoretically under the assumption that the low-energy excited states can be regarded as independent Bogolubov quasiparticles near the nodes of the superconducting order parameter. In the limiting case of temperatures well above that corresponding to the impurity scattering rate, a Boltzmann-equation description of the quasiparticle distribution is used to study thermal and electrical transport for several scattering mechanisms. In particular, the dominant scattering mechanism for the relaxation of microwave electrical currents well below TC is identified, and the observed temperature dependence of the microwave conductivity data in optimally-doped YBa2Cu3O7-delta thus explained. The Knight shift and nuclear spin relaxation rate at temperatures well above the impurity scattering rate are also calculated and compared with available data. In the opposite limiting case of temperatures well below that corresponding to the impurity scattering rate, the sound attenuation and electron-phonon heat transfer rate are calculated. A model for the electron-phonon interaction in square-lattice tight-binding materials is developed and used to explain the huge measured anisotropy of the normal-state sound attenuation in the unconventional superconductor Sr2RuO4 and to rule out certain candidates for the order parameter symmetry of this material. A calculation of the electron-phonon heat transfer rate for d-wave superconductors gives the dependence of this quantity on various material parameters. Finally, the result for the electron-phonon heat transfer rate is used to explain the origin of the anomalous downturns in the thermal conductivity that have been observed in both the normal and superconducting state of cuprate superconductors, most notably in Pr2-xCe xCuO7-delta.

  12. Electronic properties of superconductors studied using photo induced activation of microwave absorption (PIAMA)

    SciTech Connect

    Feenstra, B.J.; Schooveld, W.A.; Bos, C.

    1995-12-31

    Electronic properties of superconductors are contemporarily being studied using many different experimental techniques, among which infrared spectrometry, photoelectron spectroscopy and microwave cavity techniques play an important role. The data analysis, however, is complicated by the fact that in these materials the phonon-frequency range overlaps with the one in which the energy gap is expected. This problem can be circumvented by making use of two different sources, one to induce the excitations (the Free Electron Laser in Nieuwegein, The Netherlands, FELIX), and one to study the behavior of these excitations (i.e. quasiparticles). In our case the latter source is monochromatic microwave radiation, transmitted through a thin superconducting film. We measured both a conventional superconductor (NbN, T{sub c} = 17 K) and a high T{sub c} superconductor (SmBa{sub 2}Cu{sub 3}O{sub 7-{delta}}, T{sub c} = 92 K). For NbN we observed a positive change in transmission, followed by a relaxation to a transmission smaller than the original value, after which the starting situation was restored within {approximately} 100 {mu}s. In case of SmBa{sub 2}Cu{sub 3}O{sub 7-{delta}}, the changes persisted above T{sub c}. At very low temperatures we observed slow oscillations ({approximately} 4kHz) in the induced signal, which were absent in NbN. The long time scales can possibly be explained by the so-called bottleneck, i.e. quasiparticles excited with a lot of excess energy lose part of their energy by exciting other quasiparticles. In this case the quasiparticle lifetime is enhanced considerably. The oscillations point towards an intrinsic difference of the low energy excitations, i.e. the symmetry of the pairing.

  13. Self-assembled monolayer cleaning methods: Towards fabrication of clean high-temperature superconductor nanostructures

    SciTech Connect

    Kim, Sungwook; Chang, In Soon; McDevitt, John T.

    2005-04-11

    Although extensive amounts of research have been carried out on superconductor-normal metal-superconductor (SNS) electronic devices, the fabrication of superconductor SNS devices still remains difficult. Surface modification of high-temperature superconductors could be a way to control the interface of SNS electronic device fabrication. Here, we developed a cleaning method for thin films of high-temperature superconductor surface based on self-assembled monolayers. High-quality c-axis orientated YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (i.e., YBCO) and Y{sub 0.6}Ca{sub 0.4}Ba{sub 1.6}La{sub 0.4}Cu{sub 3}O{sub 7-{delta}} (i.e., TX-YBCO) thin films were deposited by standard laser ablation methods. YBCO/Au/YBCO and TX-YBCO/Au/TX-YBCO planar type junctions were fabricated by photolithography, focused-ion-beam milling, and ex situ sputter depositions. A 40-50 nm nanotrench was ion milled on the thin film by FIB, and a thin gold layer was deposited by an ex situ method on the nanotrench to connect the two separated high-temperature superconductor electrodes. SEM, AFM, and R vs T resistivity measurements were used to compare the corrosion layer formed in the interface of the SNS junctions with the SAM cleaned SNS junction. Evidence here suggests that the SAM cleaning method can be used to remove the degradation layer on the surface of cuprate superconductors. The obtained contact resistivity value (10{sup -8} {omega} cm{sup 2}) for a SNS junction with SAM treatment is comparable with that of SNS junctions fabricated by the in situ methods.

  14. Partial solubility parameters of lactose, mannitol and saccharose using the modified extended Hansen method and evaporation light scattering detection.

    PubMed

    Peña, M A; Daali, Y; Barra, J; Bustamante, P

    2000-02-01

    The modified extended Hansen method was tested for the first time to determine partial solubility parameters of non-polymeric pharmaceutical excipients. The method was formerly tested with drug molecules, and is based upon a regression analysis of the logarithm of the mole fraction solubility of the solute against the partial solubility parameters of a series of solvents of different chemical classes. Two monosaccharides and one disaccharide (lactose monohydrate, saccharose and mannitol) were chosen. The solubility of these compounds was determined in a series of solvents ranging from nonpolar to polar and covering a wide range of the solubility parameter scale. Sugars do not absorb at the UV-vis region, and the saturated solutions were assayed with a recent chromatographic technique coupled to an evaporative light scattering detector. This technique was suitable to determine the concentration dissolved in most solvents. The modified extended Hansen method provided better results than the original approach. The best model was the four parameter equation, which includes the dispersion delta d, dipolar delta p, acidic delta a and basic delta b partial solubility parameters. The partial solubility parameters obtained, expressed as MPa1/2, were delta d = 17.6, delta p = 28.7, delta h = 19, delta a = 14.5, delta b = 12.4, delta T = 32.8 for lactose, delta d = 16.2, delta p = 24.5, delta h = 14.6, delta a = 8.7, delta b = 12.2, delta T = 32.8 for mannitol and delta d = 17.1, delta p = 18.5, delta h = 13, delta a = 11.3, delta b = 7.6, delta T = 28.4 for saccharose. The high total solubility parameters delta T obtained agree with the polar nature of the sugars. The dispersion parameters delta d are quite similar for the three sugars indicating that the polar delta p and hydrogen bonding parameters (delta h, delta a, delta b) are responsible for the variation in the total solubility parameters delta T obtained, as also found for drugs. The results suggest that the method

  15. Thin Films and Josephson Junctions of Yttrium Barium Copper Oxide

    NASA Astrophysics Data System (ADS)

    Rosenthal, Peter Andrew

    We have studied the growth of superconducting films of rm Y_1Ba_2Cu_3O _{7-delta} using reactive electron beam coevaporation. Emphasis was placed on determining the most important growth parameters, and optimizing the instrumentation for controlling the growth environment. We have experimented with atomic absorption based deposition rate control, quartz lamp based substrate heating, and various forms of activated oxygen. Methods for generating and delivering molecular oxygen, oxygen ion beams, ozone and atomic oxygen were investigated and their effects on film quality were characterized. We found that the specific method of oxidation was not critical to the film quality but that optimal films were produced at lower pressures (~10^{-4} T) for more chemically reactive allotropes of oxygen. Composition was found to be quite important in determining the film properties. These results are discussed in the context of growth kinetics and equilibrium thermodynamics. We have studied the transport properties of artificial grain boundary Josephson junctions of rm Y_1Ba_2Cu_3O_{7-delta }. Measurements and modeling of the magnetic interference patterns of the critical currents revealed the presence of extensive disorder within the junctions. The temperature dependence of the critical currents revealed behavior consistent with the resistively shunted junction (RSJ) model. Modeling the inhomogeneous junctions as parallel arrays of RSJ-like junctions explained the clean RSJ-like current-voltage characteristics even in junctions showing extremely complicated magnetic interference patterns. The observed modulation period of the single junction interference patterns showed an unusual w^{-2} width dependence that could be quantitatively explained by a model of flux focusing based on the London theory. A model of the diffraction patterns for junctions fabricated from extremely thin films shows unexpected deviations from the usual behavior. These peculiarities are understood in terms of

  16. Thin Film Multilayer Conductor/Ferroelectric Tunable Microwave Components for Communication Applications

    NASA Technical Reports Server (NTRS)

    Miranda, Felix A.; Romanofsky, Robert R.; VanKeuls, Frederick W.; Mueller, Carl H.; Treece, Randolph E.; Rivkin, Tania V.

    1997-01-01

    High Temperature Superconductor/Ferroelectric (HTS/FE ) thin film multilayered structures deposited onto dielectric substrates are currently being investigated for use in low loss, tunable microwave components for satellite and ground based communications. The main goal for this technology is to achieve maximum tunability while keeping the microwave losses as low as possible, so as to avoid performance degradation when replacing conventional technology (e.g., filters and oscillators) with HTS/FE components. Therefore, for HTS/FE components to be successfully integrated into current working systems, full optimization of the material and electrical properties of the ferroelectric films, without degrading those of the HTS film; is required. Hence, aspects such as the appropriate type of ferroelectric and optimization of the deposition conditions (e.g., deposition temperature) should be carefully considered. The tunability range as well as the microwave losses of the desired varactor (i.e., tunable component) are also dependent on the geometry chosen (e.g., parallel plate capacitor, interdigital capacitor, coplanar waveguide, etc.). In addition, the performance of the circuit is dependent on the location of the varactor in the circuit and the biasing circuitry. In this paper, we will present our results on the study of the SrTiO3/YBa2Cu3O(7-delta)/LaAl03 (STO/YBCO/LAO) and the Ba(x)Sr(1-x)TiO3/YBa2Cu3O(7-delta)/LaAl03(BSTO/YBCO/ILAO) HTS/FE multilayered structures. We have observed that the amount of variation of the dielectric constant upon the application of a dc electric field is closely related to the microstructure of the film. The largest tuning of the STO/YBCO/LAO structure corresponded to single-phased, epitaxial STO films deposited at 800 C and with a thickness of 500 nm. Higher temperatures resulted in interfacial degradation and poor film quality, while lower deposition temperatures resulted in films with lower dielectric constants, lower tunabilities, and

  17. Characterization of Hybrid Ferroelectric/HTS Thin Films for Tunable Microwave Components

    NASA Technical Reports Server (NTRS)

    Winters, M. D.; Mueller, C. H.; Bhasin, K. B.; Miranda, F. A.

    1996-01-01

    Since the discovery of High-Temperature-Superconductors (HTS) in 1986, a diversity of HTS-based microwave components has been demonstrated. Because of their low conductor losses, HTS-based components are very attractive for integration into microwave circuits for space communication systems. Recent advancements have made deposition of ferroelectric thin films onto HTS thin films possible. Due to the sensitivity of the ferroelectric's dielectric constant (epsilon(sub r)) to an externally applied electric field (E), ferroelectric/superconducting structures could be used in the fabrication of low loss, tunable microwave components. In this paper, we report on our study of Ba(0.5)Sr(0.5)TiO3/YBa2Cu3O(7-delta) and Ba(0.08)Sr(0.92)TiO3/YBa2Cu3O(7-delta) ferroelectric/superconducting thin films on lanthanum aluminate (LaAlO3) substrates. For the (Ba:Sr, 0.50:0.50) epitaxial sample, a epsilon(sub r) of 425 and a loss tangent (tan delta) of 0.040 were measured at 298 K, 1.0 MHz, and zero applied E. For the same sample, a epsilon(sub r) of 360 and tan delta of 0.036 were obtained at 77 K, 1.0 MHz, and zero applied E. Variations in epsilon(sub r) from 180 to 360 were observed over an applied E range of 0V/cm less than or equal to E less than or equal to 5.62 x 10(exp 4) V/cm with little change in tan delta. However, the range of epsilon(sub r) variation for the polycrystalline (Ba:Sr, 0.08:0.92) sample over 0V/cm less than or equal to E less than or equal to 4.00 x 10(exp 4) V/cm was only 3.6 percent while tan delta increased markedly. These results indicate that a lack of epitaxy between the ferroelectric and superconducting layers decreases tuning and increases microwave losses.

  18. High Performance High-Tc Superconducting Wires

    SciTech Connect

    Kang, Sukill; Goyal, Amit; Li, Jing; Gapud, Albert Agcaoili; Martin, Patrick M; Heatherly Jr, Lee; Thompson, James R; Christen, David K; List III, Frederick Alyious; Paranthaman, Mariappan Parans; Lee, Dominic F

    2006-01-01

    We demonstrated short segments of a superconducting wire that meets or exceeds performance requirements for many large-scale applications of high-temperature superconducting materials, especially those requiring a high supercurrent and/or a high engineering critical current density in applied magnetic fields. The performance requirements for these varied applications were met in 3-micrometer-thick YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} films epitaxially grown via pulsed laser ablation on rolling assisted biaxially textured substrates. Enhancements of the critical current in self-field as well as excellent retention of this current in high applied magnetic fields were achieved in the thick films via incorporation of a periodic array of extended columnar defects, composed of self-aligned nanodots of nonsuperconducting material extending through the entire thickness of the film. These columnar defects are highly effective in pinning the superconducting vortices or flux lines, thereby resulting in the substantially enhanced performance of this wire.

  19. The mechanism of high-T(sub c) superconductivity due to bound hole mediators: Relationship to ferroelectricity

    NASA Technical Reports Server (NTRS)

    Vezzoli, G. C.; Stanley, William

    1990-01-01

    The mediation by bound holes creating Cooper pairing in high T(sub c) superconductors has its origin in charge transfer excitations on the multivalence cation (virtual excitions) and in bound excitions or polarizations associated with the oxygen 2p electrons. These phenomena are produced and/or enhanced by a high internal electric field which is itself created by virtue of the unique crystal structures and polyhedral building blocks of high T(sub c) materials. The polarizations which can create oxygen holes (in addition to excitions) may be due to simply the internal electric field or to polaronic and electron-deficient bond behavior. This gives rise to two energy-dependent oxygen bands near the Fermi level. The magnitude and direction of the internal electric fields were calculated for Y1Ba2Cu3O(7-delta) (1-2-3) and show strong z-direction fields at the Cu(2), O2, and O3 sites and an even stronger -z direction field at the O4 site. The field calculations also show why electrical conductivity in the 1-2-3 material is essentially in the base plane of the CuO5 pyramid (the CuO2 plane).

  20. Particle Engulfment and Pushing Micro-Gravity Experiments and Mathematical Modeling

    NASA Technical Reports Server (NTRS)

    Stefanescu, Doru M.; Catalina, A. V.; Juretzko, F.; Mukherjee, S.; Sen, S.

    2000-01-01

    The phenomenon of interaction of particles with solid-liquid interfaces that results in particle engulfment or pushing (PEP) has been Studied since mid 1960's. While the original interest stemmed from geology applications (frost heaving in soil), it was recognized early that understanding particle behavior at solidifying interfaces mi ht yield 9 practical benefits in other fields. In metallurgical applications the issue is the location of particles with respect to grain boundaries at the end of solidification. Considerable amount of experimental and theoretical research was lately focused on applications to metal matrix composites produced by casting; or spray forming techniques. Another application of PEP is in the growing of Y1Ba2CU3O7-delta(123) superconductor crystals from an undercooled liquid. The oxide melt contains Y2Ba1CU1O5 (211) precipitates, which act as flux pinning sites. The paper presents results of PEP micro-gravity research performed by the authors on two shuttle missions using metallic and polymeric materials. In addition. a discussion on the theoretical aspects of the physics of PEP is offered. Analytical and numerical models for planar solidification interfaces developed by the authors are used to explain the experimental results. Shortcomings of steady-state models are emphasized. A numerical model that includes the effect of the solutal field and of natural convection is introduced. A discussion of phenomena associated with dendritic solidification based on experimental observations is also offered. A mechanism of engulfment is proposed.

  1. Point contact spectroscopy in oriented La[sub 2-x]Sr[sub x]CuO[sub 4] superconductors; energy gap and Fermi velocity

    SciTech Connect

    Hass, N. ); Deutscher, G. ); Revcolevschi, A.; Dhalenne, G. )

    1994-08-01

    Point contact measurements in oriented La[sub 2-x]Sr[sub x]CuO[sub 4] samples were performed using metal tips. The current-voltage curves measured along the CuO plane direction (ab) are characteristic of the Andreev reflection phenomenon. The superconducting energy gap in the ab plane is determined, [Delta][sub ab] = 6 [+-] 1 meV, with a possibility for the existence of a lower subgap in the plane. A lower limit for the Fermi velocity in the CuO planes is also set by the measurements; V[sub F] [ge] 6 [times] 10[sup 7] cm/sec, which is significantly higher than the average velocity obtained by band calculations. The results are discussed in the context of different models for superconductivity in the layered oxides. In particular, the authors raise the possibility of an anisotropic gap parameter which may indicate a nonstandard s-wave pairing in La[sub 2-x]Sr[sub x]CuO[sub 4]. A comparison with previous results obtained on YBa[sub 2]Cu[sub 3]O[sub 7-[delta

  2. Superconductivity and ceramic superconductors II; Proceedings of the Symposium, Orlando, FL, Nov. 12-15, 1990

    NASA Astrophysics Data System (ADS)

    Nair, K. M.; Balachandran, U.; Chiang, Y.-M.; Bhalla, A. S.

    The present symposium on superconductivity and ceramic superconductors discusses fundamentals and general principles, powder processing and properties, fabrication and properties, and device reliability and applications. Attention is given to phase formation in the Tl-Ca-Ba-Cu-O system, comparative defect studies in La2CuO4 and La2NiO4, solid solution and defect behavior in high Tc oxides, oxygen ion transport and disorder in cuprates, and Sr-free Bi-Ln-Ca-Cu-O superconductors. Topics addressed include the preparation of superconductor Y-Ba-Cu-O powder by single-step calcining in air, low-temperature synthesis of YBa2Cu3O(7-x), synthesis of high-phase purity ceramic oxide superconductors by the xerogel method, and the preparation and characterization of the BYa2Cu4O8 superconductor. Also discussed are optical studies of humidity-based corrosion effects on thin film and bulk ceramic YBa2Cu3O(7-delta), thermomechanical processing of YBa2Cu3O(x)/Ag sheathed wires, and the expansion of high-Tc superconducting ceramics.

  3. Progress in Wind-and-React Bi-2212 Accelerator Magnet Technology

    SciTech Connect

    Godeke, A.; Cheng, D.; Dietderich, D.R.; Hannaford, C.R.; Prestemon, S.O.; Sabbi, G.; Wang, X.; Hikichi, Y.; Nishioka, J.; Hasegawa, T.

    2009-08-16

    We report on our progress in the development of the technology for the application of Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+x}(Bi-2212) in Wind-and-React accelerator magnets. A series of superconducting subscale coils has been manufactured at LBNL and reacted at the wire manufacturer SWCC. Selected coils are impregnated and tested in self-field, even though the coils exhibited leakage during the partial melt heat treatment. Other coils have been disassembled after reaction and submitted to critical current (Ic) tests on individual cable sections. We report on the results of the current carrying capacity of the coils. Voltage-current (VI) transitions were reproducibly measured up to a quench currents around 1400 A, which is 25% of the expected performance. The results indicate that the coils are limited by the inner windings. We further compare possibilities to use Bi-2212 and Nb{sub 3}Sn tilted solenoid, and YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO) racetrack inserts to increase the magnetic field in HD2, a 36 mm bore Nb{sub 3}Sn dipole magnet which recently achieved a bore magnetic field of 13.8 T. The application of Bi-2212 and/or YBCO in accelerator type magnets, if successful, will open the road to higher magnetic fields, far surpassing the limitations of Nb{sub 3}Sn magnet technology.

  4. The YTA7 gene is involved in the regulation of the isoprenoid pathway in the yeast Saccharomyces cerevisiae.

    PubMed

    Kuranda, Klaudia; Grabinska, Kariona; Berges, Thierry; Karst, Francis; Leberre, Veronique; Sokol, Serguei; François, Jean; Palamarczyk, Grazyna

    2009-05-01

    The isoprenoid pathway in yeasts is important not only for sterol biosynthesis but also for the production of nonsterol molecules, deriving from farnesyl diphosphate (FPP), implicated in N-glycosylation and biosynthesis of heme and ubiquinones. FPP formed from mevalonate in a reaction catalyzed by FPP synthase (Erg20p). In order to investigate the regulation of Erg20p in Saccharomyces cerevisiae, we searched for its protein partners using a two-hybrid screen, and identified five interacting proteins, among them Yta7p. Subsequently, we showed that Yta7p was a membrane-associated protein localized both to the nucleus and to the endoplasmic reticulum. Deletion of YTA7 affected the enzymatic activity of cis-prenyltransferase (the enzyme that utilizes FPP for dolichol biosynthesis) and the cellular levels of isoprenoid compounds. Additionally, it rendered cells hypersensitive to lovastatin, an inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR) that acts upstream of FPP synthase in the isoprenoid pathway. While HMGR is encoded by two genes, HMG1 and HMG2, only HMG2 overexpression was able to restore growth of the yta7Delta cells in the presence of lovastatin. Moreover, the expression level of the S. cerevisiae YTA7 gene was altered upon impairment of the isoprenoid pathway not only by lovastatin but also by zaragozic acid, an inhibitor of squalene synthase. Altogether, these results provide substantial evidence of Yta7p involvement in the regulation of isoprenoid biosynthesis. PMID:19416104

  5. Modified two-fluid model of conductivity for superconducting surface resistance calculation. Master's thesis

    SciTech Connect

    Linden, D.S.

    1993-05-01

    The traditional two-fluid model of superconducting conductivity was modified to make it accurate, while remaining fast, for designing and simulating microwave devices. The modification reflects the BCS coherence effects in the conductivity of a superconductor, and is incorporated through the ratio of normal to superconducting electrons. This modified ratio is a simple analytical expression which depends on frequency, temperature and material parameters. This modified two-fluid model allows accurate and rapid calculation of the microwave surface impedance of a superconductor in the clean and dirty limits and in the weak- and strong-coupled regimes. The model compares well with surface resistance data for Nb and provides insight into Nb3Sn and Y1Ba2Cu3O(7-delta). Numerical calculations with the modified two-fluid model are an order of magnitude faster than the quasi-classical program by Zimmermann (1), and two to five orders of magnitude faster than Halbritter's BCS program (2) for surface resistance.

  6. Etude des phenomenes dynamiques ultrarapides et des caracteristiques impulsionnelles d'emission terahertz du supraconducteur YBCO

    NASA Astrophysics Data System (ADS)

    Savard, Stephane

    Les premieres etudes d'antennes a base de supraconducteurs a haute temperature critique emettant une impulsion electromagnetique dont le contenu en frequence se situe dans le domaine terahertz remontent a 1996. Une antenne supraconductrice est formee d'un micro-pont d'une couche mince supraconductrice sur lequel un courant continu est applique. Un faisceau laser dans le visible est focalise sur le micro-pont et place le supraconducteur dans un etat hors-equilibre ou des paires sont brisees. Grace a la relaxation des quasiparticules en surplus et eventuellement de la reformation des paires supraconductrices, nous pouvons etudier la nature de la supraconductivite. L'analyse de la cinetique temporelle du champ electromagnetique emis par une telle antenne terahertz supraconductrice s'est averee utile pour decrire qualitativement les caracteristiques de celle-ci en fonction des parametres d'operation tels que le courant applique, la temperature et la puissance d'excitation. La comprehension de l'etat hors-equilibre est la cle pour comprendre le fonctionnement des antennes terahertz supraconductrices a haute temperature critique. Dans le but de comprendre ultimement cet etat hors-equilibre, nous avions besoin d'une methode et d'un modele pour extraire de facon plus systematique les proprietes intrinseques du materiau qui compose l'antenne terahertz a partir des caracteristiques d'emission de celle-ci. Nous avons developpe une procedure pour calibrer le spectrometre dans le domaine temporel en utilisant des antennes terahertz de GaAs bombarde aux protons H+ comme emetteur et detecteur. Une fois le montage calibre, nous y avons insere une antenne emettrice dipolaire de YBa 2Cu3O7-delta . Un modele avec des fonctions exponentielles de montee et de descente du signal est utilise pour lisser le spectre du champ electromagnetique de l'antenne de YBa 2Cu3O7-delta, ce qui nous permet d'extraire les proprietes intrinseques de ce dernier. Pour confirmer la validite du modele

  7. Motivational effects of smoked marijuana: behavioral contingencies and low-probability activities.

    PubMed Central

    Foltin, R W; Fischman, M W; Brady, J V; Bernstein, D J; Capriotti, R M; Nellis, M J; Kelly, T H

    1990-01-01

    Six adult male research volunteers, in two groups of 3 subjects each, lived in a residential laboratory for 15 days. All contact with the experimenters was through a networked computer system, and subjects' behavior was monitored continuously and recorded. During the first part of each day, they were allowed to socialize. Two cigarettes containing active marijuana (2.7% delta 9-THC) or placebo were smoked during the private work period and the period of access to social activities. Three-day contingency conditions requiring subjects to engage in a low-probability work activity (instrumental activity) in order to earn time that could be spent engaging in a high-probability work activity (contingent activity) were programmed during periods of placebo and active-marijuana smoking. During placebo administration, the contingency requirement reliably increased the amount of time that subjects spent engaged in the low-probability instrumental activity and decreased the time spent engaged in the high-probability activity. During active-marijuana administration, however, the increases in instrumental activity were consistently larger than observed under placebo conditions. The decreases in contingent activity were similar to those seen under placebo conditions. Smoking active marijuana was thus observed to produce increments in instrumental activity under motivational conditions involving contingencies for "work activities." PMID:2299291

  8. High Temperature Superconducting RF Resonators for Resonator Stabilized Oscillators

    NASA Astrophysics Data System (ADS)

    Goettee, Jeffrey David

    Electromagnetic resonators made of superconducting materials show unusually sharp resonances because resistive losses are minimized. The availability of high quality thin films of YB_2CU_3 O_{7-delta} (YBCO) with superconducting transitions at 92K has aroused interest in thin film resonators at microwave frequencies for use in filters and oscillators in communication and radar systems. I have investigated the design and radio frequency (rf) properties of superconducting resonators in microstrip geometries (in which the resonant element and a single ground plane are on opposite faces of the LaAlO_3 substrates). This monolithic approach minimizes vibration sensitivity, but exposes the resonators to interactions with the packaging structure. I used niobium (Nb) superconducting 2 GHz resonators at 4.2K to investigate the geometry dependence of the quality factor Q and the high frequency phase noise S_ {y}(f). Q's in excess of 250,000 and S_{y}(1 Hz) = -227 were achieved. Desirable geometries were then fabricated in YBCO thin films produced by coevaporation or sputtering. They typically showed Q's that are a factor of four lower than the comparable Nb resonator, but retained their usefulness to substantially higher temperatures ( ~60K). One of these YBCO resonators was successfully operated to stabilize an oscillator operating at 2 GHz with overall single-sideband phase noise }(1 Hz) = -30 dBc/Hz comparable to the best available competing technologies.

  9. The anisotropic microwave electrodynamics of YBCO

    NASA Astrophysics Data System (ADS)

    Hosseini-Gheinani, Ahmad Reza

    The anisotropic microwave surface impedance of the high temperature superconductor, YBa2Cu3O7-delta, has been investigated. Microwave spectroscopy using five microwave cavities has been used to show clearly the development of long lived quasiparticles (QP) in the ab-plane of YBa2Cu3O6.99. Two regimes of transport are found, one below 20 K where the quasiparticle (QP) dynamics is with residual impurities, and above 20 K where umklapp QP-QP interactions dictate the temperature dependence of the transport lifetimes. The C-axis microwave surface impedance of YBa2Cu 3O6.95 has been studied into the superconducting state. The long QP lifetimes found in the planes of this material are found to be absent in the conductivity observed along the c-axis, indicating that the confinement of carriers to the planes is an inherent feature of the cuprates. The highly underdoped superconducting state has also been investigated with microwave techniques. The temperature dependence of the c -axis superfluid stiffness is found to scale over a range of hole dopings, corresponding to Tc's in the range 9--19 K. We further find that the magnitude of the zero temperature c -axis superfluid stiffness grows rapidly with doping, initially as fast as T2c .

  10. Novel structural phenomena at the maximum T{sub c} in 123 and HgBa{sub 2}CuO{sub 4+{delta}} superconductors : evidence for a structural response that competes with superconductivity.

    SciTech Connect

    Jorgensen, J. D.

    1998-06-03

    Structural distortions that compete with superconductivity have been investigated in two systems where oxygen content can be used to vary the doping continuously from the under doped state, through the maximum T{sub c} into the over doped state. In the 123 system, (La{sub 1{minus}x}Ca{sub x})(Ba{sub 1.75{minus}x}La{sub 0.25+x})Cu{sub 3}O{sub 7+{delta}}, the buckling of the CuO{sub 2} planes goes through a maximum at the maximum T{sub c}. In HgBa{sub 2}CuO{sub 4+{delta}}, where buckling of the CuO{sub 2} planes is not available as a structural degree of freedom, there is a plateau at the maximum T{sub c} where the unit cell volume expands as oxygen is added while the charge transfer and T{sub c} remain constant. These unusual structural phenomena upon crossing through the maximum T{sub c} are hypothesized to be a response of the crystal structure to the electronic structure, with the structural distortions competing with superconductivity, or lowering the T{sub c} from what it would otherwise be.

  11. Conductors with small Fermi energies and small gap energies

    SciTech Connect

    Thorn, R.J.

    1993-09-01

    If the Fermi energy is of the order of meV`s, the usual treatment of the density of free electrons is not valid, but use can be made of an averaged density of states that depends weakly on temperature, so that the temperature variation of the conductivity can be expressed by the equation: {sigma} {congruent} CT{sup (1-s)} 1n{l_brace}[(exp({beta}E{sub f}) + 1)/2][exp({minus}{beta}(E{sub g} {minus} E{sub f})) + 1)]{r_brace} in which E{sub f} is the Fermi energy, E{sub g} is the top of the energy gap for thermal activation, s is the exponent of the temperature-dependent scattering. This equation serves to define a class of solids consisting of a microcomposite with a narrow conduction band for which E{sub f} of the order of ceV`s or less and a thermal activated conduction for which E{sub g} is of the order of ceV`s. It describes quantitatively the conductivity, {sigma}(T;{Delta}, for YBa{sub 2}Cu{sub 3}O{sub 7-{Delta}} and {sigma}(T;p) as the hydrostatic pressure p is varied for {kappa}-(BEDT-TTF){sub 2}CuN(CN){sub 2}Br.

  12. Iridium: An Oxygen Diffusion Barrier and a Conductive Seed Layer for RABiTS-Based Coated Conductors

    SciTech Connect

    Aytug, Tolga; Paranthaman, Mariappan Parans; Zhai, Hong-Ying; Leonard, Keith J; Gapud, Albert Agcaoili; Thompson, James R; Martin, Patrick M; Goyal, Amit; Christen, David K

    2005-01-01

    For power applications of YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO) coated conductors, it is necessary to electrically stabilize the conductor. An economic way to achieve this, which also benefits the engineering J{sub E}, is to grow conductive buffer layers directly on textured Cu or Ni metal surfaces. However, due to poor oxidation resistance and high reactivity/diffusivity of Cu or Ni, an insulating oxide layer usually forms at the metal/substrate interface, degrading the electrical connectivity of the entire architecture. To overcome this problem, we have developed a new conductive, nonmagnetic buffer layer architecture of La{sub 0.7}Sr{sub 0.3}MnO{sub 3}/Ir on textured Ni-based tapes. This structure serves as a barrier to both inward diffusion of oxygen and outward diffusion of metal cations. Using PLD to grow YBCO, we demonstrate ideal electrical coupling to the metal substrate. Critical current (I{sub c}) values for 1 {mu}m thick YBCO coatings exceed 100 A/cm-width at 77 K on a Ni-W RABiTS template.

  13. Gluon-spin contribution to the proton spin from the double-helicity asymmetry in inclusive pi0 production in polarized p+p collisions at [sqrt]s=200 GeV.

    PubMed

    Adare, A; Afanasiev, S; Aidala, C; Ajitanand, N N; Akiba, Y; Al-Bataineh, H; Alexander, J; Aoki, K; Aphecetche, L; Asai, J; Atomssa, E T; Averbeck, R; Awes, T C; Azmoun, B; Babintsev, V; Bai, M; Baksay, G; Baksay, L; Baldisseri, A; Barish, K N; Barnes, P D; Bassalleck, B; Basye, A T; Bathe, S; Batsouli, S; Baublis, V; Baumann, C; Bazilevsky, A; Belikov, S; Bennett, R; Berdnikov, A; Berdnikov, Y; Bickley, A A; Boissevain, J G; Borel, H; Boyle, K; Brooks, M L; Buesching, H; Bumazhnov, V; Bunce, G; Butsyk, S; Camacho, C M; Campbell, S; Chand, P; Chang, B S; Chang, W C; Charvet, J-L; Chernichenko, S; Chi, C Y; Chiu, M; Choi, I J; Choudhury, R K; Chujo, T; Chung, P; Churyn, A; Cianciolo, V; Citron, Z; Cole, B A; Constantin, P; Csanád, M; Csörgo, T; Dahms, T; Dairaku, S; Das, K; David, G; Denisov, A; d'Enterria, D; Deshpande, A; Desmond, E J; Dietzsch, O; Dion, A; Donadelli, M; Drapier, O; Drees, A; Drees, K A; Dubey, A K; Durum, A; Dutta, D; Dzhordzhadze, V; Efremenko, Y V; Egdemir, J; Ellinghaus, F; Engelmore, T; Enokizono, A; En'yo, H; Esumi, S; Eyser, K O; Fadem, B; Fields, D E; Finger, M; Finger, M; Fleuret, F; Fokin, S L; Fraenkel, Z; Frantz, J E; Franz, A; Frawley, A D; Fujiwara, K; Fukao, Y; Fusayasu, T; Garishvili, I; Glenn, A; Gong, H; Gonin, M; Gosset, J; Goto, Y; de Cassagnac, R Granier; Grau, N; Greene, S V; Perdekamp, M Grosse; Gunji, T; Gustafsson, H-A; Henni, A Hadj; Haggerty, J S; Hamagaki, H; Han, R; Hartouni, E P; Haruna, K; Haslum, E; Hayano, R; Heffner, M; Hemmick, T K; Hester, T; He, X; Hill, J C; Hohlmann, M; Holzmann, W; Homma, K; Hong, B; Horaguchi, T; Hornback, D; Huang, S; Ichihara, T; Ichimiya, R; Ikeda, Y; Imai, K; Imrek, J; Inaba, M; Isenhower, D; Ishihara, M; Isobe, T; Issah, M; Isupov, A; Ivanischev, D; Jacak, B V; Jia, J; Jin, J; Johnson, B M; Joo, K S; Jouan, D; Kajihara, F; Kametani, S; Kamihara, N; Kamin, J; Kang, J H; Kapustinsky, J; Kawall, D; Kazantsev, A V; Kempel, T; Khanzadeev, A; Kijima, K M; Kikuchi, J; Kim, B I; Kim, D H; Kim, D J; Kim, E; Kim, S H; Kinney, E; Kiriluk, K; Kiss, A; Kistenev, E; Klay, J; Klein-Boesing, C; Kochenda, L; Kochetkov, V; Komkov, B; Konno, M; Koster, J; Kozlov, A; Král, A; Kravitz, A; Kunde, G J; Kurita, K; Kurosawa, M; Kweon, M J; Kwon, Y; Kyle, G S; Lacey, R; Lai, Y S; Lajoie, J G; Layton, D; Lebedev, A; Lee, D M; Lee, K B; Lee, T; Leitch, M J; Leite, M A L; Lenzi, B; Liebing, P; Liska, T; Litvinenko, A; Liu, H; Liu, M X; Li, X; Love, B; Lynch, D; Maguire, C F; Makdisi, Y I; Malakhov, A; Malik, M D; Manko, V I; Mannel, E; Mao, Y; Masek, L; Masui, H; Matathias, F; McCumber, M; McGaughey, P L; Means, N; Meredith, B; Miake, Y; Mikes, P; Miki, K; Milov, A; Mishra, M; Mitchell, J T; Mohanty, A K; Morino, Y; Morreale, A; Morrison, D P; Moukhanova, T V; Mukhopadhyay, D; Murata, J; Nagamiya, S; Nagle, J L; Naglis, M; Nagy, M I; Nakagawa, I; Nakamiya, Y; Nakamura, T; Nakano, K; Newby, J; Nguyen, M; Niita, T; Nouicer, R; Nyanin, A S; O'Brien, E; Oda, S X; Ogilvie, C A; Okada, H; Okada, K; Oka, M; Onuki, Y; Oskarsson, A; Ouchida, M; Ozawa, K; Pak, R; Palounek, A P T; Pantuev, V; Papavassiliou, V; Park, J; Park, W J; Pate, S F; Pei, H; Peng, J-C; Pereira, H; Peresedov, V; Peressounko, D Yu; Pinkenburg, C; Purschke, M L; Purwar, A K; Qu, H; Rak, J; Rakotozafindrabe, A; Ravinovich, I; Read, K F; Rembeczki, S; Reuter, M; Reygers, K; Riabov, V; Riabov, Y; Roach, D; Roche, G; Rolnick, S D; Rosati, M; Rosendahl, S S E; Rosnet, P; Rukoyatkin, P; Ruzicka, P; Rykov, V L; Sahlmueller, B; Saito, N; Sakaguchi, T; Sakai, S; Sakashita, K; Samsonov, V; Sato, T; Sawada, S; Sedgwick, K; Seele, J; Seidl, R; Semenov, A Yu; Semenov, V; Seto, R; Sharma, D; Shein, I; Shibata, T-A; Shigaki, K; Shimomura, M; Shoji, K; Shukla, P; Sickles, A; Silva, C L; Silvermyr, D; Silvestre, C; Sim, K S; Singh, B K; Singh, C P; Singh, V; Slunecka, M; Soldatov, A; Soltz, R A; Sondheim, W E; Sorensen, S P; Sourikova, I V; Staley, F; Stankus, P W; Stenlund, E; Stepanov, M; Ster, A; Stoll, S P; Sugitate, T; Suire, C; Sukhanov, A; Sziklai, J; Takagui, E M; Taketani, A; Tanabe, R; Tanaka, Y; Taneja, S; Tanida, K; Tannenbaum, M J; Taranenko, A; Tarján, P; Themann, H; Thomas, T L; Togawa, M; Toia, A; Tomásek, L; Tomita, Y; Torii, H; Towell, R S; Tram, V-N; Tserruya, I; Tsuchimoto, Y; Vale, C; Valle, H; van Hecke, H W; Veicht, A; Velkovska, J; Vertesi, R; Vinogradov, A A; Virius, M; Vrba, V; Vznuzdaev, E; Walker, D; Wang, X R; Watanabe, Y; Wei, F; Wessels, J; White, S N; Williamson, S; Winter, D; Woody, C L; Wysocki, M; Xie, W; Yamaguchi, Y L; Yamaura, K; Yang, R; Yanovich, A; Ying, J; Yokkaichi, S; Young, G R; Younus, I; Yushmanov, I E; Zajc, W A; Zaudtke, O; Zhang, C; Zhou, S; Zolin, L

    2009-07-01

    The double helicity asymmetry in neutral pion production for pT=1 to 12 GeV/c was measured with the PHENIX experiment to access the gluon-spin contribution, DeltaG, to the proton spin. Measured asymmetries are consistent with zero, and at a theory scale of micro2=4 GeV2 a next to leading order QCD analysis gives DeltaG[0.02,0.3]=0.2, with a constraint of -0.7<DeltaG[0.02,0.3]<0.5 at Deltachi2=9 (approximately 3sigma) for the sampled gluon momentum fraction (x) range, 0.02 to 0.3. The results are obtained using predictions for the measured asymmetries generated from four representative fits to polarized deep inelastic scattering data. We also consider the dependence of the DeltaG constraint on the choice of the theoretical scale, a dominant uncertainty in these predictions. PMID:19659137

  14. Glass precursor approach to high-temperature superconductors

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.

    1992-01-01

    The available studies on the synthesis of high T sub c superconductors (HTS) via the glass precursor approach were reviewed. Melts of the Bi-Sr-Ca-Cu-O system as well as those doped with oxides of some other elements (Pb, Al, V, Te, Nb, etc.) could be quenched into glasses which, on further heat treatments under appropriate conditions, crystallized into the superconducting phase(s). The nature of the HTS phase(s) formed depends on the annealing temperature, time, atmosphere, and the cooling rate and also on the glass composition. Long term annealing was needed to obtain a large fraction of the 110 K phase. The high T sub c phase did not crystallize out directly from the glass matrix, but was preceded by the precipitation of other phases. The 110 K HTS was produced at high temperatures by reaction between the phases formed at lower temperatures resulting in multiphase material. The presence of a glass former such as B2O3 was necessary for the Y-Ba-Cu-O melt to form a glass on fast cooling. A discontinuous YBa2Cu3O(7-delta) HTS phase crystallized out on heat treatment of this glass. Attempts to prepare Tl-Ba-Ca-Cu-O system in the glassy state were not successful.

  15. Measurements on Subscale Y-Ba-Cu-O Racetrack Coils at 77 K and Self-Field

    SciTech Connect

    Wang, X.; Caspi, S.; Cheng, D. W.; Dietderich, D. R.; Felice, H.; Ferracin, P.; Godeke, A.; Joseph, J. M.; Lizarazo, J.; Prestemon, S. O.; Sabbi, G.

    2009-10-19

    YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO) tapes carry significant amount of current at fields beyond the limit of Nb-based conductors. This makes the YBCO tapes a possible conductor candidate for insert magnets to increase the bore field of Nb{sub 3}Sn high-field dipoles. As an initial step of the YBCO insert technology development, two subscale racetrack coils were wound using Kapton-insulated commercial YBCO tapes. Both coils had two layers; one had 3 turns in each layer and the other 10 turns. The coils were supported by G10 side rails and waxed strips and not impregnated. The critical current of the coils was measured at 77 K and self-field. A 2D model considering the magnetic-field dependence of the critical current was used to estimate the expected critical current. The measured results show that both coils reached 80%-95% of the expected values, indicating the feasibility of the design concept and fabrication process.

  16. Gluon-Spin Contribution to the Proton Spin from the Double-Helicity Asymmetry in Inclusive pi(0) Production in Polarized p plus p Collisions at s = 200 GeV

    SciTech Connect

    Adare, A.; Awes, Terry C; Cianciolo, Vince; Enokizono, Akitomo; Read Jr, Kenneth F; Silvermyr, David O; Sorensen, Soren P; Stankus, Paul W; Young, Glenn R; PHENIX, Collaboration

    2009-01-01

    The double helicity asymmetry in neutral pion production for p{sub T} = 1 to 12 GeV/c was measured with the PHENIX experiment to access the gluon-spin contribution, {Delta}G, to the proton spin. Measured asymmetries are consistent with zero, and at a theory scale of {mu}{sup 2} = 4 GeV{sup 2} a next to leading order QCD analysis gives {Delta}G{sup [0.02,0.3]} = 0.2, with a constraint of -0.7 < {Delta}G{sup [0.02,0.3]} < 0.5 at {Delta}{chi}{sup 2} = 9 (-3{sigma}) for the sampled gluon momentum fraction (x) range, 0.02 to 0.3. The results are obtained using predictions for the measured asymmetries generated from four representative fits to polarized deep inelastic scattering data. We also consider the dependence of the {Delta}G constraint on the choice of the theoretical scale, a dominant uncertainty in these predictions.

  17. Late-Glacial to Late-holocene Shifts in Global Precipitation Delta(sup 18)O

    NASA Technical Reports Server (NTRS)

    Jasechko, S.; Lechler, A.; Pausata, F.S.R.; Fawcett, P.J.; Gleeson, T.; Cendon, D.I.; Galewsky, J.; LeGrande, A. N.; Risi, C.; Sharp, Z. D.; Welker, J. M.; Werner, M.; Yoshimura, K.

    2015-01-01

    Reconstructions of Quaternary climate are often based on the isotopic content of paleo-precipitation preserved in proxy records. While many paleo-precipitation isotope records are available, few studies have synthesized these dispersed records to explore spatial patterns of late-glacial precipitation delta(sup 18)O. Here we present a synthesis of 86 globally distributed groundwater (n 59), cave calcite (n 15) and ice core (n 12) isotope records spanning the late-glacial (defined as 50,000 to 20,000 years ago) to the late-Holocene (within the past 5000 years). We show that precipitation delta(sup 18)O changes from the late-glacial to the late-Holocene range from -7.1% (delta(sup 18)O(late-Holocene) > delta(sup 18)O(late-glacial) to +1.7% (delta(sup 18)O(late-glacial) > delta(sup 18)O(late-Holocene), with the majority (77) of records having lower late-glacial delta(sup 18)O than late-Holocene delta(sup 18)O values. High-magnitude, negative precipitation delta(sup 18)O shifts are common at high latitudes, high altitudes and continental interiors.

  18. [Involvement of PHO80 and PHO85 genes in Saccharomyces cerevisiae ion tolerance].

    PubMed

    Mao, Xi-Cheng; Xia, Yu-Lei; Hu, Ya-Fang; Lu, Chang-De

    2003-01-01

    PHO85 is a versatile gene in Saccharomyces cerevisiae, which is involved in metabolism of inorganic phosphate and usage of carbon source, accumulation of glycogen, regulation of protein stability and cell cycle control. The viability of wild type budding yeast strain YPH499 and its derivative pho85Delta mutant, pho80 mutant, and pap1(pcl-7)Delta mutant in different cations were investigated and their tolerance to the cations(LC(50)) was measured. The results showed that the deletion of PHO85 or PHO80 gene both increased sensibility of Sacchromyces cerevisiae to ions K(+), Mg(2+), Zn(2+), Ca(2+) and Mn(2+), while the deletion of pap1(pcl-7) gene did not lead to such phenotype. The difference between the patterns of relative growth curve of the mutants and wild type strain in the above ions also implied that PHO80 was the unique PCLs in complex with PHO85 CDK, that were contributed to K(+) and Mg(2+) ion homeostasis control and there were some other PCLs besides PHO80 that were involved in Zn(2+), Ca(2+) and Mn(2+) tolerance regulation as cyclin of PHO85 CDK. Furthermore, the amount of the total cellular calcium of pho85Delta mutant, pho80Delta mutant and YPH499 indicated that the ability of calcium accumulation of pho85 mutant and pho80Delta mutant was impaired. PMID:12518234

  19. Fixed-frequency and Frequency-agile (au, HTS) Microstrip Bandstop Filters for L-band Applications

    NASA Technical Reports Server (NTRS)

    Saenz, Eileen M.; Subramanyam, Guru; VanKeuls, Fred W.; Chen, Chonglin; Miranda, Felix A.

    2001-01-01

    In this work, we report on the performance of a highly selective, compact 1.83 x 2.08 cm(exp 2) (approx. 0.72 x 0.82 in(exp 2) microstrip line bandstop filter of YBa2CU3O(7-delta) (YBCO) on LaAlO3 (LAO) substrate. The filter is designed for a center frequency of 1.623 GHz for a bandwidth at 3 dB from reference baseline of less than 5.15 MHz, and a bandstop rejection of 30 dB or better. The design and optimization of the filter was performed using Zeland's IE3D circuit simulator. The optimized design was used to fabricate gold (Au) and High-Temperature Superconductor (HTS) versions of the filter. We have also studied an electronically tunable version of the same filter. Tunability of the bandstop characteristics is achieved by the integration of a thin film conductor (Au or HTS) and the nonlinear dielectric ferroelectric SrTiO3 in a conductor/ferroelectric/dielectric modified microstrip configuration. The performance of these filters and comparison with the simulated data will be presented.

  20. Superconducting submillimeter and millimeter wave detectors

    SciTech Connect

    Nahum, M.

    1992-10-20

    The series of projects described in this dissertation was stimulated by the discovery of high temperature superconductivity. Our goal was to develop useful applications which would be competitive with the current state of technology. The high-{Tc} microbolometer was developed into the most sensitive direct detector of millimeter waves, when operated at liquid nitrogen temperatures. The thermal boundary resistance of thin YBa{sub 2}Cu{sub 3}0{sub 7-{delta}} films was subsequently measured and provided direct evidence for the bolometric response of high-{Tc} films to fast (ns) laser pulses. The low-{Tc} microbolometer was developed and used to make the first direct measurements of the frequency dependent optical efficiency of planar lithographed antennas. The hot-electron microbolometer was invented less than a year prior to the writing of this dissertation. Our analysis, presented here, indicates that it should be possible to attain up to two orders of magnitude higher sensitivity than that of the best available direct detectors when operated at the same temperature. The temperature readout scheme for this device could also be used to measure the intrinsic interaction between electrons and phonons in a metal with a sensitivity that is five orders of magnitude better than in previous measurements. Preliminary measurements of quasiparticle trapping effects at the interface between a metal and a superconductor are also presented.

  1. [Production and properties of chitinase from Beauveria bassiana Bb174 in solid state fermentation].

    PubMed

    Zhang, Jie; Cai, Jingmin; Wu, Ke; Jin, Shengxian; Pan, Renrui; Fan, Meizhen

    2004-05-01

    This paper studied the chitinase production of Beauveria bassiana Bb174 under solid state fermentation condition. The optimal medium consisted of wheat bran and silkworm chrysalis at the ratio of 4:1, supplemented with 1 g peptone L(-1) as nitrogen source and some other mineral nutrients. The enzyme activity reached 126 units per gram dry medium after cultured for 2 days at 28 degrees C and natural pH by inoculated 3 ml spore suspension into this medium. The optimal temperature and pH for chintinase production were 40 degrees C and 5.0, respectively. The temperature to lose 50% activity of the enzyme was 48 degrees C after incubated at 30-70 degrees C for 1 h. The enzyme was stable at 30-40 degrees C and pH 4-6, and the Km and Vmax values were 0.52 mg x ml(-1) and 0.7 deltaE680 x h(-1), respectively. PMID:15320411

  2. Normal Liver Tissue Density Dose Response in Patients Treated With Stereotactic Body Radiation Therapy for Liver Metastases

    SciTech Connect

    Howells, Christopher C.; Stinauer, Michelle A.; Diot, Quentin; Westerly, David C.; Schefter, Tracey E.; Kavanagh, Brian D.; Miften, Moyed

    2012-11-01

    Purpose: To evaluate the temporal dose response of normal liver tissue for patients with liver metastases treated with stereotactic body radiation therapy (SBRT). Methods and Materials: Ninety-nine noncontrast follow-up computed tomography (CT) scans of 34 patients who received SBRT between 2004 and 2011 were retrospectively analyzed at a median of 8 months post-SBRT (range, 0.7-36 months). SBRT-induced normal liver tissue density changes in follow-up CT scans were evaluated at 2, 6, 10, 15, and 27 months. The dose distributions from planning CTs were mapped to follow-up CTs to relate the mean Hounsfield unit change ({Delta}HU) to dose received over the range 0-55 Gy in 3-5 fractions. An absolute density change of 7 HU was considered a significant radiographic change in normal liver tissue. Results: Increasing radiation dose was linearly correlated with lower post-SBRT liver tissue density (slope, -0.65 {Delta}HU/5 Gy). The threshold for significant change (-7 {Delta}HU) was observed in the range of 30-35 Gy. This effect did not vary significantly over the time intervals evaluated. Conclusions: SBRT induces a dose-dependent and relatively time-independent hypodense radiation reaction within normal liver tissue that is characterized by a decrease of >7 HU in liver density for doses >30-35 Gy.

  3. Search for Cosmic-Ray-Induced Gamma-Ray Emission in Galaxy Clusters

    NASA Technical Reports Server (NTRS)

    Ackermann, M.; Ajello, M.; Albert, A.; Allafort, A.; Atwood, W. B.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Bloom, E. D.; Bonamente, E.; Bottacini, E.; Brandt, T. J.; Bregeon, J.; Brigida, M.; Bruel, P.; Buehler, R.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Caraveo, P. A.; Cavazzuti, E.; Chaves, R. C. G.; Kuss, M.; Pesce-Rollins, M.; Sgro, C.; Spandre, G.; Tinivella, M.

    2014-01-01

    Current theories predict relativistic hadronic particle populations in clusters of galaxies in addition to the already observed relativistic leptons. In these scenarios hadronic interactions give rise to neutral pions which decay into gamma rays that are potentially observable with the Large Area Telescope (LAT) on board the Fermi space telescope. We present a joint likelihood analysis searching for spatially extended gamma-ray emission at the locations of 50 galaxy clusters in four years of Fermi-LAT data under the assumption of the universal cosmic-ray (CR) model proposed by Pinzke & Pfrommer. We find an excess at a significance of 2.7 delta, which upon closer inspection, however, is correlated to individual excess emission toward three galaxy clusters: A400, A1367, and A3112. We discuss these cases in detail and conservatively attribute the emission to unmodeled background systems (for example, radio galaxies within the clusters).Through the combined analysis of 50 clusters, we exclude hadronic injection efficiencies in simple hadronic models above 21% and establish limits on the CR to thermal pressure ratio within the virial radius, R(sub 200), to be below 1.25%-1.4% depending on the morphological classification. In addition, we derive new limits on the gamma-ray flux from individual clusters in our sample.

  4. Experimental Investigation of High Temperature Superconducting Imaging Surface Magnetometry

    SciTech Connect

    Espy, M.A.; Matlachov, A.N.; Kraus, R.H., Jr.

    1999-06-21

    The behavior of high temperature superconducting quantum interference devices (SQUIDs) in the presence of high temperature superconducting surfaces has been investigated. When current sources are placed close to a superconducting imaging surface (SIS) an image current is produced due to the Meissner effect. When a SQUID magnetometer is placed near such a surface it will perform in a gradiometric fashion provided the SQUID and source distances to the SIS are much less than the size of the SIS. We present the first ever experimental verification of this effect for a high temperature SIS. Results are presented for two SQUID-SIS configurations, using a 100 mm diameter YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} disc as the SIS. These results indicate that when the current source and sensor coil (SQUID) are close to the SIS, the behavior is that of a first-order gradiometer. The results are compared to analytic solutions as well as the theoretical predictions of a finite element model.

  5. Specificities of the Acyl-Acyl Carrier Protein (ACP) Thioesterase and Glycerol-3-Phosphate Acyltransferase for Octadecenoyl-ACP Isomers (Identification of a Petroselinoyl-ACP Thioesterase in Umbelliferae).

    PubMed Central

    Dormann, P.; Frentzen, M.; Ohlrogge, J. B.

    1994-01-01

    This study was designed to address the question: How specific for double bond position and conformation are plant enzymes that act on oleoyl-acyl carrier protein (ACP)? Octadecenoyl-ACPs with cis double bonds at positions [delta]6, [delta]7, [delta]8, [delta]9, [delta]10, [delta]11, or [delta]12 and elaidyl (18:1[delta]9trans)-ACP were synthesized and used to characterize the substrate specificity of the acyl-ACP thioesterase and acyl-ACP:sn-glycerol-3-phosphate acyltransferase. The two enzymes were found to be specific for the [delta]9 position of the double bond. The thioesterase was highly specific for the [delta]9 cis conformation, but the transferase was almost equally active with the cis and the trans isomer of 18:1[delta]9-ACP. In plants such as the Umbelliferae species coriander (Coriandrum sativum L.) that accumulate petroselinic acid (18:1[delta]6cis) in their seed triacylglycerols, a high petroselinoyl-ACP thioesterase activity was found in addition to the oleoyl-ACP thioesterase. The two activities could be separated by anion-exchange chromatography, indicating that the petroselinoyl-ACP thioesterase is represented by a distinct polypeptide. PMID:12232130

  6. Transinhibition of C1 inhibitor synthesis in type I hereditary angioneurotic edema.

    PubMed Central

    Kramer, J; Rosen, F S; Colten, H R; Rajczy, K; Strunk, R C

    1993-01-01

    To ascertain the mechanism for decreased synthesis of C1 inhibitor (C1 INH) in certain patients with the autosomal dominant disorder hereditary angioneurotic edema, we studied expression of C1 INH in fibroblasts in which the mutant and wild type mRNA and protein could be distinguished because of deletion of exon 7 (delta Ex7). In the HANE delta Ex7 cells, the amount of wild type mRNA (2.1 kb) was expressed at 52 +/- 2% (n = 5) of normal, whereas the mutant mRNA was 17 +/- 1% (n = 5) of normal. Rates of synthesis of both wild type and mutant proteins (11 +/- 3 and 3 +/- 1% of normal, respectively) were lower than predicted from the mRNA levels. There was no evidence of increased C1 INH protein catabolism. These data indicate that there are multiple levels of control of C1 INH synthesis in type I hereditary angioneurotic edema. Pretranslational regulation results in < 50% of the mutant truncated 1.9-kb mRNA. In addition, translational regulation results in decreased synthesis of both wild type and mutatn C1 INH proteins. These data suggest a transinhibition of wild type C1 INH translation by mutant mRNA and/or protein. Images PMID:8450054

  7. Twin engineering for high critical current densities and twin boundary energy measurement in melt processed YBCO

    NASA Astrophysics Data System (ADS)

    Mei, Linfeng

    It has been proven that twin boundaries in YBa2Cu 3O7-delta (YBCO) are effective flux pinning centers. By increasing the twin density of a YBCO sample, it is possible to achieve a high critical current density (Jc). In this work, twin engineering for high critical current densities and strong flux pinning has been achieved in melt processed YBCO by increasing the annealing temperature up to 680°C. When the isothermal oxygenation temperature increases from 450°C to 680°C, the average twin boundary spacing of the samples decreases significantly, and its critical current density and flux pinning force are greatly increased. The prerequisites for twin boundary engineering for high critical current densities and strong flux pinning are also pointed out. For the first time, temperature dependent twin boundary energies (gammatw's) of melt processed YBCO are measured by the twin spacing method and the twin tip or shape method, and the geometrical factor alpha in the twin spacing method is estimated. As expected, the twin boundary energy of YBCO decreases with increasing temperature. In addition, the correlation between Jc and the concentrations of Y2BaCuO5 (211) and Samarium (Sm) in the melt-textured growth (MTG) YBCO has been studied, as well as the distributions of 211 and Sm in the MTG YBCO pellets. All our results can be applied towards microstructure tailoring for a high Jc and strong flux pinning in YBCO, especially in bulk YBCO samples.

  8. Enhanced current transport at grain boundaries in high-T(c) superconductors.

    PubMed

    Klie, R F; Buban, J P; Varela, M; Franceschetti, A; Jooss, C; Zhu, Y; Browning, N D; Pantelides, S T; Pennycook, S J

    2005-05-26

    Large-scale applications of high-transition-temperature (high-T(c)) superconductors, such as their use in superconducting cables, are impeded by the fact that polycrystalline materials (the only practical option) support significantly lower current densities than single crystals. The superconducting critical current density (J(c)) across a grain boundary drops exponentially if the misorientation angle exceeds 2 degrees -7 degrees. Grain texturing reduces the average misorientation angle, but problems persist. Adding impurities (such as Ca in YBa2Cu3O7-delta; YBCO) leads to increased J(c) (refs 9, 10), which is generally attributed to excess holes introduced by Ca2+ substituting for Y3+ (ref. 11). However, a comprehensive physical model for the role of grain boundaries and Ca doping has remained elusive. Here we report calculations, imaging and spectroscopy at the atomic scale that demonstrate that in poly-crystalline YBCO, highly strained grain-boundary regions contain excess O vacancies, which reduce the local hole concentration. The Ca impurities indeed substitute for Y, but in grain-boundary regions under compression and tension they also replace Ba and Cu, relieving strain and suppressing O-vacancy formation. Our results demonstrate that the ionic radii are more important than their electronic valences for enhancing J(c). PMID:15917804

  9. A K-band Frequency Agile Microstrip Bandpass Filter using a Thin Film HTS/Ferroelectric/dielectric Multilayer Configuration

    NASA Technical Reports Server (NTRS)

    Subramanyam, Guru; VanKeuls, Fred; Miranda, Felix A.

    1998-01-01

    We report on YBa2Cu3O(7-delta) (YBCO) thin film/SrTiO3 (STO) thin film K-band tunable bandpass filters on LaAlO3 (LAO) dielectric substrates. The 2 pole filter has a center frequency of 19 GHz and a 4% bandwidth. Tunability is achieved through the non-linear dc electric field dependence of the relative dielectric constant of STO(epsilon(sub rSTO). A large tunability ((Delta)f/f(sub 0) = (f(sub Vmax) - f(sub 0)/f(sub 0), where f(sub 0) is the center frequency of the filter at no bias and f(sub Vmax) is the center frequency of the filter at the maximum applied bias) of greater than 10% was obtained in YBCO/STO/LAO microstrip bandpass filters operating below 77 K. A center frequency shift of 2.3 GHz (i.e., a tunability factor of approximately 15%) was obtained at a 400 V bipolar dc bias, and 30 K, with minimal degradation in the insertion loss of the filter. This paper addresses design, fabrication and testing of tunable filters based on STO ferroelectric thin films. The performance of the YBCO/STO/LAO filters is compared to that of gold/STO/LAO counterparts.

  10. Multifunctional, Phase-Separated, BaTiO3 + CoFe2O4 Cap Buffer Layers for Improved Flux-Pinning in YBa2Cu3O7- Based Coated Conductors

    SciTech Connect

    Wee, Sung Hun; Shin, Junsoo; Cantoni, Claudia; Zuev, Yuri L; Cook, Sylvester W; Goyal, Amit

    2010-01-01

    Phase separated, epitaxial, nanostructured film comprised of BaTiO{sub 3} (BTO) and CoFe{sub 2}O{sub 4} (CFO) composite has been developed as a potential multifunctional cap buffer layer for improved flux-pinning in YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO) films. All films were deposited by pulsed laser deposition on SrTiO{sub 3} (STO) (100) single crystal substrates. The CFO fraction and growth temperature were identified as key factors for determining the areal number density and mean diameter of the CFO nanocolumns. Compared to the reference sample grown on a pure BTO cap layer, the YBCO films grown on BTO+CFO cap layers show a remarkable improvement in isotropic flux-pinning and, consequently, J{sub c} over the entire field and angle ranges. Transmission electron microscopy analysis confirmed the presence of a very defective YBCO layer containing a high density of randomly distributed defects at the interface area, induced by nanostructural modulation on the surface of the BTO+CFO composite cap layer.

  11. High-sensitive scanning laser magneto-optical imaging system

    SciTech Connect

    Murakami, Hironaru; Tonouchi, Masayoshi

    2010-01-15

    A high-sensitive scanning laser magneto-optical (MO) imaging system has been developed. The system is mainly composed of a laser source, galvano meters, and a high-sensitive differential optical-detector. Preliminary evaluation of system performance by using a Faraday indicator with a Faraday rotation coefficient of 3.47x10{sup -5} rad/{mu}m Oe shows a magnetic sensitivity of about 5 {mu}T, without any need for accumulation or averaging processing. Using the developed MO system we have succeeded in the fast and quantitative imaging of a rotationally symmetric magnetic field distribution around an YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO) strip line applied with dc-biased current, and also succeeded in the detection of quantized fine signals corresponding to magnetic flux quantum generation in a superconducting loop of an YBCO Josephson vortex flow transistor. Thus, the developed system enables us not only to do fast imaging and local signal detection but also to directly evaluate both the strength and direction of a magnetic signal.

  12. High-sensitive scanning laser magneto-optical imaging system.

    PubMed

    Murakami, Hironaru; Tonouchi, Masayoshi

    2010-01-01

    A high-sensitive scanning laser magneto-optical (MO) imaging system has been developed. The system is mainly composed of a laser source, galvano meters, and a high-sensitive differential optical-detector. Preliminary evaluation of system performance by using a Faraday indicator with a Faraday rotation coefficient of 3.47 x 10(-5) rad/microm Oe shows a magnetic sensitivity of about 5 microT, without any need for accumulation or averaging processing. Using the developed MO system we have succeeded in the fast and quantitative imaging of a rotationally symmetric magnetic field distribution around an YBa(2)Cu(3)O(7-delta) (YBCO) strip line applied with dc-biased current, and also succeeded in the detection of quantized fine signals corresponding to magnetic flux quantum generation in a superconducting loop of an YBCO Josephson vortex flow transistor. Thus, the developed system enables us not only to do fast imaging and local signal detection but also to directly evaluate both the strength and direction of a magnetic signal. PMID:20113101

  13. Formation of Self-Assembled Ba2YNbO6 Nanocolumns and their Contribution to Flux-Pinning and Jc in Nb-doped YBa2Cu3O7- Films

    SciTech Connect

    Wee, Sung Hun; Goyal, Amit; Zuev, Yuri L; Cantoni, Claudia; Selvamanickam, V.; Specht, Eliot D

    2010-01-01

    Ba{sub 2}RENbO{sub 6} (RE = rare earth elements including Y) compounds are considered new additives for superior flux-pinning in YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO) films due to their excellent chemical inertness to and large lattice mismatches with YBCO. Simultaneous laser ablation of a YBCO target and a Nb metal foil attached to the surface of the target resulted in epitaxial growth of YBCO films having columnar defects comprised of self-aligned Ba{sub 2}YNbO{sub 6} (BYNO) nanorods parallel to the c-axis of the film. Compared to pure YBCO, YBCO+BYNO films exhibited no T{sub c} reduction as well as superior J{sub c} performance with higher self- and in-field J{sub c} by a factor of 1.5-7 and also exhibited a strong J{sub c} peak for H {parallel} c indicative of strong c-axis correlated flux-pinning.

  14. Structural and Flux-Pinning Properties of Laser Ablated YBa2Cu3O7-δ Thin Films: Effects of Self-Assembled CeO2 Nanodots and LaAlO3 Substrates

    SciTech Connect

    Haywood, Talisha M; Oh, Sang Ho; Kebede, Abede; Pai, Devdas M.; Sankar, Jag; Christen, David K; Pennycook, Stephen J; Kumar, Dhananjay

    2008-01-01

    Self-assembled nanodots of CeO{sub 2} on (1 0 0) LaAlO{sub 3} substrates, generated in situ by means of a pulsed laser deposition method prior to the deposition of YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO) films, have been used to modify the superconducting properties of resulting YBCO films. Structural characterization has indicated that CeO{sub 2} layers grow via van der Merwe three-dimensional mode and the islands eventually acquire a pancake type of structure with lateral dimension several times larger than vertical dimension. The three-dimensional growth of CeO{sub 2} islands with (1 0 0) preferred orientation is believed to be associated with its surface energy anisotropy. The magnetization versus temperature and magnetization versus field measurements and analysis have suggested that CeO{sub 2} can affect the superconducting properties of YBCO films favorably or adversely depending on the density of CeO{sub 2} nanodots on the substrate surfaces prior to the deposition of YBCO films.

  15. Development of Modified MOD-TFA Approach for YBCO Film Growth

    SciTech Connect

    Bhuiyan, Md S; Paranthaman, Mariappan Parans; Sathyamurthy, Srivatsan; Hunt, Rodney Dale; List III, Frederick Alyious; Duckworth, Robert C

    2007-01-01

    Low-cost coated-conductor fabrication methods are essential for various electric-power applications. Metal-organic-deposition (MOD) approach to grow both YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO) and buffer layers on textured metal substrates is very promising towards fabrication of lower-cost second generation wires. YBCO coated conductors (CC) are being developed with high critical currents that should be sufficient for their extensive use in power applications. However, the present CC has high energy losses in ac magnetic field that are unacceptable. We have developed a modified MOD precursor route to deposit {approx} 0.8 {micro}m thick YBCO films in a single coat that requires less than one-fifth of the pyrolysis time compared to the traditional MOD approach. We have also developed a filamentization technique of CC using ink-jet printing to reduce ac losses due to applied ac fields. The preliminary results of YBCO films deposited on standard RABiTS template yielded an of 140 A/cm at 77 K and self- field. A modest reduction of ac loss was observed for the solution ink-jet printed filamentary conductor.

  16. Much simplified ion-beam assisted deposition-TiN template for high-performance coated conductors

    SciTech Connect

    Xiong, J.; Matias, V.; Zhai, J. Y.; Maiorov, B.; Trugman, D.; Jia, Q. X.; Wang, H.; Tao, B. W.; Li, Y. R.

    2010-10-15

    A much simplified template, i.e., two nonsuperconducting layers between the superconducting YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO) and the polycrystalline metal substrate, has been developed for high-performance coated conductors by using biaxially aligned TiN as a seed layer. A combination of a thin TiN ({approx}10 nm by ion-beam assisted deposition) layer and an epitaxial buffer LaMnO{sub 3} layer ({approx}120 nm) allows us to grow epitaxial YBCO films with values of full width at half-maximum around 3.5 deg. and 1.7 deg. for the {phi}-scan of (103) and rocking curve of (005) YBCO, respectively. The YBCO films grown on electropolished polycrystalline Hastelloy using this two-layer template exhibited a superconducting transition temperature of 89.5 K, a critical current density of 1.2 MA/cm{sup 2} at 75.5 K, and an {alpha} value (proportional factor of critical current density J{sub c}{approx}H{sup -}{alpha}) of around 0.33, indicating a high density of pinning centers and an absence of weak links.

  17. Substrate Surface Decoration With CeO2 Nanoparticles: An Effective Method for Improving Flux Pinning in YBa2Cu3O7 Films

    SciTech Connect

    Aytug, Tolga; Paranthaman, Mariappan Parans; Gapud, Albert Agcaoili; Kang, Sukill; Varela del Arco, Maria; Martin, Patrick M; Raitano, J. M.; Chan, S. W.; Thompson, James R; Christen, David K

    2007-01-01

    We have demonstrated improved critical current density, J{sub c}, in YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO) films through a controlled study of substrate surface modifications with nano-sized second-phase pre-formed CeO{sub 2} particles. Nanoparticles were applied to single crystal SrTiO{sub 3} surfaces using suspension-based techniques prior to YBCO film growth. With the introduction of CeO{sub 2} nanoparticles, YBCO films showed more robust field dependence at intermediate fields (J{sub c} {infinity} B{sup -{infinity}}), where a smaller power law exponent of {alpha} {approx} 0.3 is obtained. The self-field J{sub c}(77 K, B{parallel}c) values of the YBCO films on reference and CeO{sub 2} modified substrates are 1.1 and 1.9 MA/cm2; and at 1 Tesla 0.1 and 0.52 MA/cm2, respectively. Consistent with this {alpha}-value, angular field dependent J{sub c} and transmission electron microscopy studies indicate the presence of c-axis aligned correlated defects in these modified samples.

  18. Progress in Nanoengineered Microstructures for Tunable High-Current, High-Temperature Superconducting Wires

    SciTech Connect

    Holesinger, T. G.; Civale, L.; Maiorov, B.; Feldmann, D. M.; Coulter, Yates; Miller, D. J.; Maroni, Victor A.; Chen, Zhijun; Larbalestier, D. C.; Feenstra, Roeland; Li, Xiaoping; Huang, Y.; Kodenkandath, Thomas; Zhang, W.; Rupich, Marty; Malozemoff, Alex

    2008-01-01

    High critical current densities (J{sub c}) in thick films of the Y{sub 1}Ba{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO, {Tc}{approx}92 K) superconductor directly depend upon the types of nanoscale defects and their densities within the films. A major challenge for developing a viable wire technology is to introduce nanoscale defect structures into the YBCO grains of the thick film suitable for flux pinning and the tailoring of the superconducting properties to specific, application-dependent, temperature and magnetic field conditions. Concurrently, the YBCO film needs to be integrated into a macroscopically defect-free conductor in which the grain-to-grain connectivity maintains levels of inter-grain J{sub c} that are comparable to the intra-grain J{sub c}. That is, high critical current (I{sub c}) YBCO coated conductors must contain engineered in homogeneities on the nanoscale, while being homogeneous on the macroscale. An analysis is presented of the advances in high-performance YBCO coated-conductors using chemical solution deposition (CSD) based on metal trifluoroacetates and the subsequent processing to nano-engineer the microstructure for tunable superconducting wires. Multi-scale structural, chemical, and electrical investigations of the CSD film processes, thick film development, key microstructural features, and wire properties are presented. Prospects for further development of much higher I{sub c} wires for large-scale, commercial application are discussed within the context of these recent advances.

  19. Tetragonal YBaFe{sub 4}O{sub 7.0}: a stoichiometric polymorph of the '114' ferrite family

    SciTech Connect

    Duffort, V.; Caignaert, V.; Pralong, V.; Barrier, N.; Raveau, B.; Avdeev, M.; Zheng, H.; Mitchell, J. F.

    2012-03-01

    The exploration of the phase diagram of the ferrite YBaFe{sub 4}O{sub 7+{delta}} versus the oxygen content {delta} and temperature shows the complex crystal chemistry of this system. Besides the cubic form (F4{sup -}3m), which is observed up to 600 C and for 0 < {delta} {le} 0.65, a stoichiometric tetragonal form ({delta} = 0) is isolated below 300 C that is stable only in the absence of oxidizing atmosphere. The resolution of the structure of this new YBaFe{sub 4}O{sub 7.0} form, from combined neutron and synchrotron data, in the space group I4{sup -}, shows significant displacements of the atoms with respect to the cubic form, especially concerning the oxygen atoms surrounding the barium cations. The decrease of several Ba-O distances around the underbonded barium cations is explained by the existence of hybridized Ba{sup (2-{delta})+}-O{sup 2-}-Fe{sup (2+{delta})+} bonds, in agreement with Moessbauer spectroscopy. The role of coulombic repulsions in the [Fe{sub 4}O] and [Fe{sub 4}] tetrahedra of the [Fe{sub 4}]{infinity} sublattice on the structural transition is also discussed.

  20. Space qualified hybrid superconductor/semiconductor planar oscillator circuit

    NASA Technical Reports Server (NTRS)

    Miranda, F. A.; Chorey, C. M.; Romanofsky, R. R.; Bhasin, K. B.

    1995-01-01

    We report on the space qualification of a hybrid superconductor/semiconductor planar local oscillator (LO) at 8.4 GHz. This oscillator was designed, fabricated, and tested as a component for the High Temperature Superconductivity Space Experiment 2 (HTSSE-2). The LO consisted of a GaAs MESFET and microstrip circuitry patterned onto a YBa2Cu3O(7-delta) high temperature superconducting (HTS) thin film on a 1.0 x 1.0 sq cm lanthanum aluminate (LaAlO3) substrate. At 77 K, this oscillator achieved power output levels up to 10 dBm into a 50 Ohm load. When incorporated into a full cryogenic receiver, the LO provided output powers within 0.0-3.0 dBm with less than 50 mW of dc power dissipation. Space qualification data on the sensitivity of the HTS films to the processing steps involved in the fabrication of HTS-based components are presented. Data on ohmic contacts, strength of wire bonds made to such contacts, and aging effects as well as vibration test results are discussed.

  1. Anisotropic superconductivity observed by magneto-optical imaging: A case study of yttrium barium copper oxide

    NASA Astrophysics Data System (ADS)

    Wang, Chong

    This work studies direct Magneto-Optical Imaging (MOI) as a means to directly observe anisotropic superconductivity using (110)-oriented YBa 2Cu3O7-delta (YBCO) thin film. The MOI technique can translate magnetic field distribution directly into an optical image. It has been used to study supercurrent distribution in a superconducting thin film. A fast Fourier transform method was developed to convert the MO image into maps of current density distribution independent of the underlying models that are used to extract the critical current densities. By using this method, the inhomogeneous critical current distribution can be deduced, and current stream maps can be constructed. High quality single phase YBCO (110) thin films were fabricated by magnetron sputtering. Characterizations by X-ray diffraction, Rutherford backscattering and channeling, a scanning electron microscope, an atomic force microscope, and electric transport measurement indicates that the (110) films are single-phased, strain-free, highly oxygenated, and have a relatively smooth surface compared to the c-axis oriented counterpart prepared by the same technique. Direct imaging of the anisotropic magnetic field distribution at the surface of YBCO (110) thin film has been realized, where the unique stripe-like pattern is interpreted as based on the anisotropic critical current density model developed in this work. Geometric effects on anisotropic critical current flow have been examined. The characteristic behaviors of parabola-shaped discontinuity-lines (d-line) in an anisotropic thin film sample are discussed. Calculations of the critical currents at step-edged defects on anisotropic thin-films strip were conducted. The magnetic field pattern derived from the calculation is in good agreement with the stripe pattern of the experiment. Such step-edges are representative of physical imperfections that dictate the presence or absence of the stripe pattern in an anisotropic superconductor.

  2. Free energy of formation of Cs{sub 3}PuCl{sub 6} and CsPu{sub 2}Cl{sub 7}

    SciTech Connect

    Willamson, M.A.; Kleinschmidt, P.D.

    1992-09-01

    The free energy, enthalpy and entropy of formation of the compounds Cs{sub 3}PuCl{sub 6} and CsPu{sub 2}Cl{sub 7} have been determined by measuring the sublimation pressures for the reactions: CsCl(s) = CsCl(g), 2/5 Cs{sub 3}PuCl{sub 6}(s) = 1/5 CsPu{sub 2}Cl{sub 7}(s) + CsCl(g), and CsPu{sub 2}Cl{sub 7}(s) = 2 PuCl{sub 3}(s) + CsCl(g). The pressures are measured using Knudsen effusion mass spectrometry over the temperature range 600 to 850 K. For the formation of Cs{sub 3}PuCl{sub 6} from CsCl and PuCl{sub 3}, {Delta}G{sub 298}{sup 0} = {minus}77.3 +/{minus} 8.5 kJ/mole, {Delta}H{sub 298}{sup 0} = {minus}82.1 +/{minus} 7.8 kJ mole, and {Delta}S{sup 298}{sup 0} = {minus}16.2 +/{minus} 10.9 J/K mole. For CsPu{sub 2}Cl{sub 7}, {Delta}G{sub 298}{sup 0} = {minus}39.4 +/{minus} 3.5 kJ/mole, {Delta}H{sub 298}{sup 0} = {minus}40.8 +/{minus} 3.2 kJ/mole, and {Delta}S{sub 298}{sup 0} = {minus}4.6 +/{minus} 4.2 J/K mole.

  3. Free energy of formation of Cs sub 3 PuCl sub 6 and CsPu sub 2 Cl sub 7

    SciTech Connect

    Willamson, M.A.; Kleinschmidt, P.D.

    1992-01-01

    The free energy, enthalpy and entropy of formation of the compounds Cs{sub 3}PuCl{sub 6} and CsPu{sub 2}Cl{sub 7} have been determined by measuring the sublimation pressures for the reactions: CsCl(s) = CsCl(g), 2/5 Cs{sub 3}PuCl{sub 6}(s) = 1/5 CsPu{sub 2}Cl{sub 7}(s) + CsCl(g), and CsPu{sub 2}Cl{sub 7}(s) = 2 PuCl{sub 3}(s) + CsCl(g). The pressures are measured using Knudsen effusion mass spectrometry over the temperature range 600 to 850 K. For the formation of Cs{sub 3}PuCl{sub 6} from CsCl and PuCl{sub 3}, {Delta}G{sub 298}{sup 0} = {minus}77.3 +/{minus} 8.5 kJ/mole, {Delta}H{sub 298}{sup 0} = {minus}82.1 +/{minus} 7.8 kJ mole, and {Delta}S{sup 298}{sup 0} = {minus}16.2 +/{minus} 10.9 J/K mole. For CsPu{sub 2}Cl{sub 7}, {Delta}G{sub 298}{sup 0} = {minus}39.4 +/{minus} 3.5 kJ/mole, {Delta}H{sub 298}{sup 0} = {minus}40.8 +/{minus} 3.2 kJ/mole, and {Delta}S{sub 298}{sup 0} = {minus}4.6 +/{minus} 4.2 J/K mole.

  4. Formation of the peroxisome lumen is abolished by loss of Pichia pastoris Pas7p, a zinc-binding integral membrane protein of the peroxisome.

    PubMed Central

    Kalish, J E; Theda, C; Morrell, J C; Berg, J M; Gould, S J

    1995-01-01

    We have cloned and sequenced PAS7, a gene required for peroxisome assembly in the yeast Pichia pastoris. The product of this gene, Pas7p, is a member of the C3HC4 superfamily of zinc-binding proteins. Point mutations that alter conserved residues of the C3HC4 motif abolish PAS7 activity and reduce zinc binding, suggesting that Pas7p binds zinc in vivo and that zinc binding is essential for PAS7 function. As with most pas mutants, pas7 cells exhibit a pronounced deficiency in import of peroxisomal matrix proteins that contain either the type 1 peroxisomal targeting signal (PTS1) or the type 2 PTS (PTS2). However, while other yeast and mammalian pas mutants accumulate ovoid, vesicular peroxisomal intermediates, loss of Pas7p leads to accumulation of membrane sheets and vesicles which lack a recognizable lumen. Thus, Pas7p appears to be essential for protein translocation into peroxisomes as well as formation of the lumen of the organelle. Consistent with these data, we find that Pas7p is an integral peroxisomal membrane protein which is entirely resistant to exogenous protease and thus appears to reside completely within the peroxisome. Our observations suggest that the function of Pas7p defines a previously unrecognized step in peroxisome assembly: formation of the peroxisome lumen. Furthermore, because the peroxisomal intermediates in the pas7 delta mutant proliferate in response to peroxisome-inducing environmental conditions, we conclude that Pas7p is not required for peroxisome proliferation. PMID:7565793

  5. Microgravity Processing of Oxide Superconductors

    NASA Technical Reports Server (NTRS)

    Olive, James R.; Hofmeister, William H.; Bayuzick, Robert J.; Vlasse, Marcus

    1999-01-01

    Considerable effort has been concentrated on the synthesis and characterization of high T(sub c) oxide superconducting materials. The YBaCuO system has received the most intense study, as this material has shown promise for the application of both thin film and bulk materials. There are many problems with the application of bulk materials- weak links, poor connectivity, small coherence length, oxygen content and control, environmental reactivity, phase stability, incongruent melting behavior, grain boundary contamination, brittle mechanical behavior, and flux creep. The extent to which these problems are intrinsic or associated with processing is the subject of controversy. This study seeks to understand solidification processing of these materials, and to use this knowledge for alternative processing strategies, which, at the very least, will improve the understanding of bulk material properties and deficiencies. In general, the phase diagram studies of the YBaCuO system have concentrated on solid state reactions and on the Y2BaCuO(x) + liquid yields YBa2Cu3O(7-delta) peritectic reaction. Little information is available on the complete melting relations, undercooling, and solidification behavior of these materials. In addition, rare earth substitutions such as Nd and Gd affect the liquidus and phase relations. These materials have promising applications, but lack of information on the high temperature phase relations has hampered research. In general, the understanding of undercooling and solidification of high temperature oxide systems lags behind the science of these phenomena in metallic systems. Therefore, this research investigates the fundamental melting relations, undercooling, and solidification behavior of oxide superconductors with an emphasis on improving ground based synthesis of these materials.

  6. Measurement on electrical tunability of microstrip line resonators using YBa2Cu3O7-δ/SrTiO3/MgO multilayer thin films

    NASA Astrophysics Data System (ADS)

    Han, Seok K.; Kim, Jeha; Lee, Sang Yeol; Kang, Kwang-Yong

    1995-09-01

    We have fabricated YBa2Cu3O7-(delta ) (YBCO) superconducting line resonator and tunable line resonator on ferroelectric Sr0.5Ba0.5TiO3 (SBTO) buffered MgO(100) substrate and discussed the frequency shift mechanism of superconductor as a function of temperature and bias voltage, respectively. The resonators were designed using superconducting YBCO epitaxial thin films. Optimized resonator shown the resonant frequency of 10 GHz at 77 K. The YBCO films were grown in situ by pulsed laser deposition technique at 750 degree(s)C and oxygen partial pressure of 200 mTorr. The resonators have linear microstrip line separated by a gap of 5 micrometers and 0.5 mm, respectively. A gap is intentionally introduced to generate mainly a capacitive series reactance. The equivalence circuit of line resonator is a II network consisted of three capacitances. As the series capacitance C12 of SBTO ferroelectric thin films was changed by a bias voltage applied on the strip conductors including the gap, resonance frequency was shifted about 20 MHz from the unbiased center frequency of 10 GHz. The variation of resonance peak could be explained by a serial capacitance model. To find a central frequency mechanism depending on temperature, we fit the raw data using f(T)/f(10 K) and simple power law model. The shifting of the resonant frequencies due to temperature was fit to a two-fluid model, BCS theory and empirical formula. Also the surface impedance of superconducting YBCO films as a function of temperature at 10 GHz has been estimated by a transmission line method.

  7. Characterization of a high-temperature superconducting conductor on round core cables in magnetic fields up to 20 T

    SciTech Connect

    van der Laan, D. C.; Noyes, P. D.; Miller, G. E.; Weijers, H. W.; Willering, G. P.

    2013-02-13

    The next generation of high-ï¬eld magnets that will operate at magnetic ï¬elds substantially above 20 T, or at temperatures substantially above 4.2 K, requires high-temperature superconductors (HTS). Conductor on round core (CORC) cables, in which RE-Ba{sub 2}Cu{sub 3}O{sub 7-{delta}} (RE = rare earth) (REBCO) coated conductors are wound in a helical fashion on a flexible core, are a practical and versatile HTS cable option for low-inductance, high-field magnets. We performed the first tests of CORC magnet cables in liquid helium in magnetic fields of up to 20 T. A record critical current I{sub c} of 5021 A was measured at 4.2 K and 19 T. In a cable with an outer diameter of 7.5 mm, this value corresponds to an engineering current density J{sub e} of 114 A mm{sup -2} , the highest J{sub e} ever reported for a superconducting cable at such high magnetic fields. Additionally, the first magnet wound from an HTS cable was constructed from a 6 m-long CORC cable. The 12-turn, double-layer magnet had an inner diameter of 9 cm and was tested in a magnetic field of 20 T, at which it had an I{sub c} of 1966 A. The cables were quenched repetitively without degradation during the measurements, demonstrating the feasibility of HTS CORC cables for use in high-field magnet applications.

  8. Lunar Limb Observatory: An Incremental Plan for the Utilization, Exploration, and Settlement of the Moon

    NASA Technical Reports Server (NTRS)

    Lowman, Paul. D., Jr.

    1996-01-01

    This paper proposes a comprehensive incremental program, Lunar Limb Observatory (LLO), for a return to the Moon, beginning with robotic missions and ending with a permanent lunar settlement. Several recent technological developments make such a program both affordable and scientifically valuable: robotic telescopes, the Internet, light-weight telescopes, shared- autonomy/predictive graphics telerobotic devices, and optical interferometry systems. Reasons for focussing new NASA programs on the Moon include public interest, Moon-based astronomy, renewed lunar exploration, lunar resources (especially helium-3), technological stimulus, accessibility of the Moon (compared to any planet), and dispersal of the human species to counter predictable natural catastrophes, asteroidal or cometary impacts in particular. The proposed Lunar Limb Observatory would be located in the crater Riccioli, with auxiliary robotic telescopes in M. Smythii and at the North and South Poles. The first phase of the program, after site certification, would be a series of 5 Delta-launched telerobotic missions to Riccioli (or Grimaldi if Riccioli proves unsuitable), emplacing robotic telescopes and carrying out surface exploration. The next phase would be 7 Delta-launched telerobotic missions to M. Smythii (2 missions), the South Pole (3 missions), and the North Pole (2 missions), emplacing robotic telescopes to provide continuous all-sky coverage. Lunar base establishment would begin with two unmanned Shuttle/Fitan-Centaur missions to Riccioli, for shelter emplacement, followed by the first manned return, also using the Shuttle/Fitan-Centaur mode. The main LLO at Riccioli would then be permanently or periodically inhabited, for surface exploration, telerobotic rover and telescope operation and maintenance, and support of Earth-based student projects. The LLO would evolve into a permanent human settlement, serving, among other functions, as a test area and staging base for the exploration

  9. How close to ideal is the photon gas Corrections to Planck's laws at kT. much lt. m sub e

    SciTech Connect

    Barton, G. )

    1991-01-01

    At temperatures well below the electron rest mass, the electron-positron concentrations in black-body radiation (BBR) are negligible, and deviations from Planck's laws are due to the photon-photon coupling described (in natural units) by the classic Euler-Heisenberg local interaction Lagrangean density ({alpha}{sup 2}/360{pi}{sup 2}m{sub e}{sup 4})((E{sup 2}{minus}B{sup 2}){sup 2}+7(E{center dot}B){sup 2}). Though unobservably small, these corrections answer the question in the title. They are best expressed in terms of the (frequency-independent) shift in the refractive index {kappa} = (1+{Delta}{kappa}) of BBR, where {Delta}{kappa} = {alpha}{sup 2}(kT/m{sub e}){sup 4}44{pi}{sup 2}/2025 {approx} 7.5 {times} 10{sup {minus}35}(T/300){sup 4}. There are fractional changes of 3 {Delta}{kappa}/2 in the free-energy density and the pressure; 7 {Delta}{kappa}/2 in the energy density; and 2 {Delta}{kappa} in the mean-square electric field in any frequency range, whence only the intensity of the Planck spectrum is shifted but not its shape. The dielectric constant {var epsilon} = (1 + {Delta}{var epsilon}) and magnetic susceptibility {mu} = (1 + {Delta}{mu}) of BBR are equal, with {Delta}{var epsilon} = {Delta}{mu} = {Delta}{kappa}, whence the author compares the BBR shifts with those in an ordinary linear nondispersive medium having {var epsilon} = {mu} = {kappa} {triple bond} {radical}{epsilon}{mu}.

  10. Regioselective Porphyrin Bridge Cleavage Controlled by Electronic Effects. Coupled Oxidation of 3-Demethyl-3-(trifluoromethyl)mesohemin IX and Identification of Its Four Biliverdin Derivatives.

    PubMed

    Crusats, Joaquim; Suzuki, Akihiro; Mizutani, Tadashi; Ogoshi, Hisanobu

    1998-02-01

    This report describes the nonenzymatic oxidative cleavage of the title porphyrin (2) performed with oxygen and ascorbic acid in aqueous pyridine at 37 degrees C (coupled oxidation), via hydrolysis of the corresponding verdoheme intermediates, followed by esterification of the resulting free acid mesobiliverdin analogues to their dimethyl esters 4 (alpha isomer), 5 (beta isomer), 6 (gamma isomer), and 7 (delta isomer). The four biliverdin derivatives were purified by HPLC, and their structures were confirmed by FAB MS and also by UV-vis and (1)H NMR spectroscopies. The purity of each compound was checked by (19)F NMR, and the four regioisomers were assigned through their 2D-NMR ROESY spectra and confirmed by UV-vis spectroscopy. The ratio of regioisomers was determined by (19)F NMR spectroscopy before any purification of single compounds was attempted: alpha:beta:gamma:delta 11:6:26:57 (%). This unusually high regioselectivity was attributed to the electron-withdrawing effect of the CF(3) group on the electronic structure of porphyrin as shown considering the ab initio calculations of an iron(II) beta-substituted (trifluoromethyl)porphyrin used as a model compound. In porphyrin 2, the oxidation clearly takes place at the electron richest meso positions, the order of reactivity strictly following that of electron density, pointing out that the regiospecificity of the bridge cleavage can be effectively controlled by the electronic effects of some strategic substituents in the chromophore. The relevance of all these results in the study of the mechanism of the reactions involved in the natural catabolism of heme, catalyzed by heme oxygenase, is discussed. The advantages of 2 derived from this work, which make it a suitable model compound for the enzymatic reaction, are also discussed. PMID:11672050

  11. ADAPTIVE OPTICS IMAGES. II. 12 KEPLER OBJECTS OF INTEREST AND 15 CONFIRMED TRANSITING PLANETS

    SciTech Connect

    Adams, E. R.; Dupree, A. K.; Kulesa, C.; McCarthy, D.

    2013-07-01

    All transiting planet observations are at risk of contamination from nearby, unresolved stars. Blends dilute the transit signal, causing the planet to appear smaller than it really is, or producing a false positive detection when the target star is blended with an eclipsing binary. High spatial resolution adaptive optics images are an effective way of resolving most blends. Here we present visual companions and detection limits for 12 Kepler planet candidate host stars, of which 4 have companions within 4''. One system (KOI 1537) consists of two similar-magnitude stars separated by 0.''1, while KOI 174 has a companion at 0.''5. In addition, observations were made of 15 transiting planets that were previously discovered by other surveys. The only companion found within 1'' of a known planet is the previously identified companion to WASP-2b. An additional four systems have companions between 1'' and 4'': HAT-P-30b (3.''7, {Delta}Ks = 2.9), HAT-P-32b (2.''9, {Delta}Ks = 3.4), TrES-1b (2.''3, {Delta}Ks = 7.7), and WASP-P-33b (1.''9, {Delta}Ks = 5.5), some of which have not been reported previously. Depending on the spatial resolution of the transit photometry for these systems, these companion stars may require a reassessment of the planetary parameters derived from transit light curves. For all systems observed, we report the limiting magnitudes beyond which additional fainter objects located 0.''1-4'' from the target may still exist.

  12. Particle Engulfment and Pushing By Solidifying Interfaces

    NASA Technical Reports Server (NTRS)

    Stefanescu, Doru M.; Mukherjee, Sundeep; Juretzko, Frank Robert; Catalina, A.drian V.; Sen, Subhayu; Curreri, P. A.

    2001-01-01

    The phenomenon of interaction of particles with solid-liquid interfaces (SLI) has been studied since the mid 1960's. While the original interest stemmed from geology applications (frost heaving in soil), researchers soon realized that fundamental understanding of particles behavior at solidifying interfaces might yield practical benefits in other fields, including metallurgy. In materials engineering the main issue is the location of particles with respect to grain boundaries at the end of solidification. Considerable experimental and theoretical research was lately focused on applications to metal matrix composites produced by casting or spray forming techniques, and on inclusion management in steel. Another application of particle SLI interaction is in the growing of Y1Ba2Cu3O(7-delta) (123) superconductor crystals from an undercooled liquid. The oxide melt contains Y2Ba1Cu1O5 (211) precipitates, which act as flux pinning sites. The experimental evidence on transparent organic materials, as well as the recent in situ observations on steel demonstrates that there exist a critical velocity of the planar SLI below which particles are pushed ahead of the interface, and above which particles are engulfment. The engulfment of a SiC particle in succinonitrile is exemplified. However, in most commercial alloys dendritic interfaces must be considered. Indeed, most data available on metallic alloys are on dendritic structures. The term engulfment is used to describe incorporation of a particle by a planar or cellular interface as a result of local interface perturbation, as opposed to entrapment that implies particle incorporation at cells or dendrites boundaries. During entrapment the particles are pushed in the intercellular or interdendritic regions and then captured when local solidification occurs. The physics of these two phenomena is fundamentally different.

  13. Functions of the periplasmic loop of the porin MspA from Mycobacterium smegmatis.

    PubMed

    Huff, Jason; Pavlenok, Mikhail; Sukumaran, Suja; Niederweis, Michael

    2009-04-10

    MspA is the major porin of Mycobacterium smegmatis and mediates diffusion of small and hydrophilic solutes across the outer membrane. The octameric structure of MspA, its sharply defined constriction zone, and a large periplasmic loop L6 represent novel structural features. L6 consists of 13 amino acids and is directly adjacent to the constriction zone. Deletion of 3, 5, 7, 9, and 11 amino acids of the L6 loop resulted in functional pores that restored glucose uptake and growth of a porin mutant of M. smegmatis. Lipid bilayer experiments revealed that all mutant channels were noisier than wild type (wt) MspA, indicating that L6 is required for pore stability in vitro. Voltage gating of the Escherichia coli porin OmpF was attributed to loops that collapse into the channel in response to a strong electrical field. Here, we show that deletion mutants Delta7, Delta9, and Delta11 had critical voltages similar to wt MspA. This demonstrated that the L6 loop is not the primary voltage-dependent gating mechanism of MspA. Surprisingly, large deletions in L6 resulted in 3-6-fold less extractable pores, whereas small deletions did not alter expression levels of MspA. Pores with large deletions in L6 were more permissive for glucose than smaller deletion mutants, whereas their single channel conductance was similar to that of wt MspA. These results indicate that translocation of ions through the MspA pore is governed by different mechanisms than that of neutral solutes. This is the first study identifying a molecular determinant of solute translocation in a mycobacterial porin. PMID:19208627

  14. A Meaurement of the W+- production cross section in p anti-p collisions at sqroot(s)=1.96 TeV in the DiLepton channel and limits on anomalous WWZ/gamma couplings

    SciTech Connect

    McGivern, Dustin; /University Coll. London

    2005-12-01

    Measurements of the production cross section of W{sup +}W{sup -} pairs in p{bar p} collisions at 1.96 TeV and limits on trilinear gauge boson coupling (TGC) parameters are presented. The data were recorded with the CDF experiment at Tevatron during the 2001 and 2002 data taking periods in which a total integrated luminosity of 184 pb{sup -1} was collected. The data sample was filtered for events with two leptonic w boson decays where the charged leptons can be either electrons or muons. 17 events are observed against an expected background of 5.0{sub -0.8}{sup +2.2} events. The resulting cross-section is found to be {sigma}(p{bar p} {yields} W{sup +}W{sup -}) = 14.5{sub -5.1}{sup +5.8}(stat){sub -3.0}{sup +1.8}(syst) {+-} 0.9(lum) pb and agrees well with the Standard Model expectation. Limits on the TGC parameters {Delta}{kappa} and {lambda} are set under both the equal coupling scheme, that assumes the W boson couples identically to the Z and {gamma}, and the HISZ coupling scheme, that requires the couplings to respect SU(2){sub L} x &(1){sub Y} gauge symmetry. In both cases this is achieved by using a likelihood fit to the lepton-P{sub T} distribution of the 17 candidate events. The resulting limits are found to be: -0.4 < {Delta}{kappa} < +0.6({lambda} = 0); -0.3 < {lambda} < +0.4 ({Delta}{kappa} = 0) for the EQUAL couplings and -0.7 < {Delta}{kappa} < +0.9 ({lambda} = 0); -0.4 < {lambda} < +0.4 ({Delta}{kappa} = 0) for the HISZ couplings.

  15. Electrodeposited Biaxially Textured Buffer Layers for YBCO Superconductors

    SciTech Connect

    Bhattacharya, R.; Phok, S.; Zhao, W.; Norman, A.

    2009-06-01

    Non-vacuum electrodeposition (ED) was used to prepare simplified Gd{sub 2}O{sub 3}/Gd{sub 2}Zr{sub 2}O{sub 7} and CeO{sub 2}/Gd{sub 2}Zr{sub 2}O{sub 7} buffer layers on a Ni-W substrate. Post-annealing conditions of electrodeposited precursor films were optimized to obtain high-quality biaxially textured buffer layers. The buffer layers were characterized by X-ray diffraction, optical profiling, and transmission electron microscopy (TEM). The effect of the cap layer thickness on the surface morphology and texture of the buffers was also studied. The microstructure of CeO{sub 2}/Gd{sub 2}Zr{sub 2}O{sub 7} was analyzed and compared to Gd{sub 2}O{sub 3}/Gd{sub 2}Zr{sub 2}O{sub 7}. The high-resolution TEM shows biaxially textured crystalline elctrodeposited Gd{sub 2}O{sub 3} and CeO{sub 2} cap layers on the electrodeposited Gd{sub 2}Zr{sub 2}O{sub 7} layers without any defects. YBa{sub 2}Cu{sub 3}O{sub 7}-delta (YBCO) superconductor was deposited by pulsed laser deposition (PLD) on the simplified ED-Gd{sub 2}O{sub 3}/Gd{sub 2}Zr{sub 2}O{sub 7} and ED-CeO{sub 2}/Gd{sub 2}Zr{sub 2}O{sub 7} buffers. Transport current density of 3.3 MA/cm{sup 2} at 77 K was obtained for PLD YBCO deposited on ED-Gd{sub 2}O{sub 3}/Gd{sub 2}Zr{sub 2}O{sub 7} buffer layers.

  16. YBCO High-Temperature Superconducting Filters on M-Plane Sapphire Substrates

    NASA Technical Reports Server (NTRS)

    Sabataitis, J. C.; Mueller, C. H.; Miranda, F. A.; Warner, J.; Bhasin, K. B.

    1996-01-01

    Since the discovery of High Temperature Superconductors (HTS) in 1986, microwave circuits have been demonstrated using HTS films on various substrates. These HTS-based circuits have proven to operate with less power loss than their metallic film counterparts at 77 K. This translates into smaller and lighter microwave circuits for space communication systems such as multiplexer filter banks. High quality HTS films have conventionally been deposited on lanthanum aluminate (LaAlO3) substrates. However, LaAlO3 has a relative dielectric constant (epsilon(sub r)) of 24. With a epsilon(sub r) approx. 9.4-11.6, sapphire (Al2O3) would be a preferable substrate for the fabrication of HTS-based components since the lower dielectric constant would permit wider microstrip lines to be used in filter design, since the lower dielectric constant would permit wider microstrip lines to be used for a given characteristic impedance (Z(sub 0)), thus lowering the insertion losses and increasing the power handling capabilities of the devices. We report on the fabrication and characterization of YBa2Cu3O(7-delta) (YBCO) on M-plane sapphire bandpass filters at 4.0 GHz. For a YBCO 'hairpin' filter, a minimum insertion loss of 0.5 dB was measured at 77 K as compared with 1.4 dB for its gold counterpart. In an 'edge-coupled' configuration, the insertion loss went down from 0.9 dB for the gold film to 0.8 dB for the YBCO film at the same temperature.

  17. Enhancement of critical current density of YBa2Cu3O7-x thin films by self-assembly of Y2O3 nanoparticles

    SciTech Connect

    Vishwanathan, S.; Gapud, Albert Agcaoili; Varela del Arco, Maria; Abiade, J.; Christen, David K; Pennycook, Stephen J; Kumar, Dhananjay

    2007-01-01

    YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO) thin films, possessing high critical current density (J{sub c}), have been synthesized by embedding a homogeneous array of Y2O3 non-superconducting nanoclusters/nanoparticles using a pulsed laser deposition technique. The size, interparticle spacing, and density of Y2O3 nanoparticles in YBCO thin films were tailored by varying the number of laser pulses in order to determine the optimum size for effective immobilization of vortices. Scanning transmission electron microscopy with atomic number contrast and X-ray diffraction techniques were used to determine the size and structure of the nanoparticles. Both techniques indicate that the Y{sub 2}O{sub 3} particles are epitaxial with respect to the surrounding YBCO matrix. The information about pinning of vortices by the nanoparticles was obtained by investigating the behavior of critical current density as a function of temperature and applied field, which in turn determines the vortex density in the sample. The superconducting transition temperature ({Tc}) of YBCO films with the inclusion of nanoparticles was observed to remain almost the same or decrease marginally (1-2 K) with respect to Tc of pure YBCO films deposited under identical conditions. However, JcS of YBCO films embedded with self-assembled nanoparticles were found to be significantly higher than that of pure YBCO films. The Jc enhancement was up to five times in high magnetic field, which is a key requirement for practical application of high-{Tc} materials.

  18. Sequentially evaporated thin Y-Ba-Co-O superconducting films on microwave substrates

    NASA Technical Reports Server (NTRS)

    Valco, G. J.; Rohrer, N. J.; Warner, J. D.; Bhasin, K. B.

    1989-01-01

    The development of high T sub c superconducting thin films on various microwave substrates is of major interest in space electronic systems. Thin films of YBa2Cu3O(7-Delta) were formed on SrTiO3, MgO, ZrO2 coated Al2O3, and LaAlO3 substrates by multi-layer sequential evaporation and subsequent annealing in oxygen. The technique allows controlled deposition of Cu, BaF2 and Y layers, as well as the ZrO buffer layers, to achieve reproducibility for microwave circuit fabrication. The three layer structure of Cu/BaF2/Y is repeated a minimum of four times. The films were annealed in an ambient of oxygen bubbled through water at temperatures between 850 C and 900 C followed by slow cooling (-2 C/minute) to 450 C, a low temperature anneal, and slow cooling to room temperature. Annealing times ranged from 15 minutes to 5 hrs. at high temperature and 0 to 6 hr. at 450 C. Silver contacts for four probe electrical measurements were formed by evaporation followed with an anneal at 500 C. The films were characterized by resistance-temperature measurements, energy dispersive X-ray spectroscopy, X-ray diffraction, and scanning electron microscopy. Critical transition temperatures ranged from 30 K to 87 K as a function of the substrate, composition of the film, thicknesses of the layers, and annealing conditions. Microwave ring resonator circuits were also patterned on these MgO and LaAlO3 substrates.

  19. Experimental transport studies of yttrium barium copper oxide and lambda-DNA

    NASA Astrophysics Data System (ADS)

    Zhang, Yuexing

    This dissertation consists of two parts. In Part I, we focus on the quasi-particle transport properties in the high temperature superconductor YBa2Cu3O7-delta (YBCO), probed by the thermal Hall conductivity (kappa xy). The thermal Hall conductivity selectively reflects the transport behaviors of the charge carriers. By measuring kappaxy in the normal state YBCO, we established a new method to determine the Wiedemann-Franz (WF) ratio in cuprates. We determined the Hall-channel WF ratio kappa xy/sigmaxyT in Cu and YBCO. In the latter, we uncovered a T-linear dependence and suppression of the Hallchannel WF ratio. The suppression of the Hall-channel WF ratio in systems with predominant electron-electron scattering will be discussed. Thermal transport behaviors of the quasi-particles in the mixed state were studied by measuring kappaxx and kappa xy in a high-purity YBCO crystal. From the field-dependence of the thermal conductivity kappaxx, we separated the quasi particle contribution (kappae) from the phonon background. In the Hall channel, we observed that the (weak-field) kappa xy increased 103-fold between T c (90 K) and 30 K, implying a 100-fold enhancement of the quasi-particle lifetime. We found that kappaxy exhibited a specific scaling behavior below ˜30 K. The implication of the scaling behavior will be discussed. In Part II, we describe an experiment on determining the electrical conductivity of the bacteriophage lambda-DNA, an issue currently under intense debate. We covalently bonded the DNA to Au electrodes by incorporating thiol modified dTTP into the 'sticky' ends of the lambda-DNA. Two-probe measurements on such molecules provided a lower bound for the resistivity rho > 10 6 mum at bias potentials up to 20 V, in conflict with recent claims of moderate to high conductivity. We stress the importance of eliminating salt residues in these measurements.

  20. Scanning Hall probe microscopy of supercurrents in YBCO films

    NASA Astrophysics Data System (ADS)

    Dinner, Rafael Baruch

    High-temperature superconductors were discovered 20 years ago, inspiring dreams of levitating trains fed by superconducting power lines. The cuprates, particularly YBa2Cu3O7-delta (YBCO), still promise to fulfill such applications, but must be made to carry higher current density, Jc, which is limited by the rapid onset of dissipation. The dissipation arises from the movement of magnetic vortices in the material, driven by the magnetic field of the current. It is therefore natural to use magnetic imaging to understand these limits on the current. Initially, I fix a mesoscopic ring of YBCO to a micro-Hall sensor and demonstrate that the sensor is capable of detecting small numbers of vortices. I then proceed with magnetic imaging, constructing a cryogenic scanning Hall probe microscope that combines a 1 x 4 cm scan range with 200 nm positioning resolution by coupling stepper motors to high-resolution drivers and reducing gears. It enables me to image an entire sample, then zoom in on regions of interest, down to the level of an individual quantized vortex. Applying this capability to current-carrying YBCO strips, I generate magnetic movies of the materials' periodic response to applied ac currents. From the movies, I reconstruct current density by inverting the Biot-Savart law, and electric field by approximating dB/dt and using Faraday's law. I thereby obtain complete, space- and time-resolved characterizations of the materials, including maps of ac power losses. After demonstrating this analysis on a single-crystal film, I image two "coated conductors"---YBCO grown on metal tape. I find relatively homogeneous flux penetration in a film grown by pulsed laser deposition (PLD) on an ion beam assisted deposition (IBAD) substrate, which contrasts with the weak-link behavior of grain boundaries in a film grown by metalorganic deposition (MOD) on rolling assisted biaxially textured substrate (RABiTS). Nonetheless, the in-plane meandering of the MOD film's boundaries

  1. The Search for Anyon Superconductivity: do High - Superconductors Exhibit a Spontaneous T-Violating Circular Dichroism?

    NASA Astrophysics Data System (ADS)

    Lawrence, Taylor Walton

    The subject of this thesis is an investigation of whether a class of cuprate compounds having superconducting transition temperatures as high as 100 K change the optical properties of reflected light in such a way that would indicate the violation of time-reversal symmetry (T-violation), analogous to that observed in ferromagnets. Such an effect could be interpreted as evidence that anyons are the fundamental microscopic charge carriers responsible for the superconductivity. An "anyon" is a new, fundamental, excitation of a strongly -correlated two-dimensional electron gas which can obey particle-exchange statistics anywhere between the Fermi -Dirac or Bose-Einstein limits. In this thesis, I report on an experiment in which I attempted to reproduce the data originally reported by K. B. Lyons, et al., of AT&T Bell Laboratories. Their data purportedly showed that certain high temperature superconducting compounds exhibit a spontaneous circular dichroism in reflection, below about 200 K. I show a simple extension to their original experiment, which I discovered, that discriminates against an important spurious term, and makes my apparatus exclusively sensitive to T-violating circular dichroism. I found no evidence for a temperature dependent signal in both thin films and an untwinned single crystal of YBa _2Cu_3O _{7-delta} (T_ {rm c} ~ 90 K), to an accuracy approaching 10^{ -6}. However, my data does show a temperature independent "background" signal which is correlated with the optical quality of the sample's surface. I offer a detailed explanation of the origins of this background signal, and show how it can become a temperature dependent signal when there are changes to the surface properties of the sample due to condensation of residual gases in a poor vacuum. Although this experiment shows no evidence for the macroscopic breakdown of time-reversal symmetry, anyons could still be at the heart of high temperature superconductivity, since there are numerous

  2. Magnetic biosensor using a high transition temperature SQUID

    NASA Astrophysics Data System (ADS)

    Grossman, Helene Lila

    A high transition temperature (Tc) Superconducting QUantum Interference Device (SQUID) is used to detect magnetically-labeled microorganisms. The targets are identified and quantified by means of magnetic relaxation measurements, with no need for unbound magnetic labels to be washed away. The binding rate between antibody-linked magnetic particles and targets can be measured with this technique. Installed in a "SQUID microscope," a YBa2Cu 3O7-delta SQUID is mounted on a sapphire rod thermally linked to a liquid nitrogen can; these components are enclosed in a fiberglass vacuum chamber. A thin window separates the vacuum chamber from the sample, which is at room temperature and atmospheric pressure. In one mode of the experiment, targets are immobilized on a substrate and immersed a suspension of ˜50 nm diameter superparamagnetic particles, coated with antibodies. A pulsed magnetic field aligns the magnetic dipole moments, and the SQUID measures the magnetic relaxation signal each time the field is turned off. Unbound particles relax within ˜50 mus by Brownian rotation, too fast for the SQUID system to measure. In contrast, particles bound to targets have their Brownian motion inhibited. These particles relax in ˜1 s by rotation of the internal dipole moment, and this Neel relaxation process is detected by the SQUID. This assay is demonstrated with a model system of liposomes carrying the FLAG epitope; the detection limit is (2.7 +/- 0.2) x 105 particles. The replacement of the SQUID with a gradiometer improves the detection limit to (7.0 +/- 0.7) x 103 particles. In an alternate mode of the experiment, freely suspended targets (larger than ˜1 mum diameter) are detected. Since the Brownian relaxation time of the targets is longer than the measurement time, particles bound to targets are effectively immobilized and exhibit Neel relaxation. Listeria monocytogenes are detected using this method; the sensitivity is (1.1 +/- 0.2) x 105 bacteria in 20 muL. For a 1 n

  3. Association quotients of aluminum sulphate complexes in NaCl media from 50 to 125 C: Results of a potentiometric and solubility study

    SciTech Connect

    Ridley, M.K.; Kettler, R.M.; Wesolowski, D.J.; Palmer, D.A.

    1999-02-01

    The speciation and molal formation quotients for the complexation of aluminum with sulphate were measured based on potentiometric and solubility experiments. Potentiometric titrations, utilizing a hydrogen-electrode concentration cell, were performed from 50 to 125 C at ionic strengths of 0.1, 0.3 and 1.0 molal in aqueous NaCl media. Two aluminum-sulphate species, AlSO{sub 4}{sup +} and Al(SO{sub 4}){sub 2}{sup {minus}}, were identified from the titration data and the formation quotients for these species were modeled by empirical equations to describe their temperature and ionic strength dependencies. Thermodynamic parameters for the complexation reactions were obtained by differentiating the empirical equations with respect to temperature. The thermodynamic quantities obtained for the formation of AlSO{sub 4}{sup +} at 50 C and infinite dilution are: logK{sub 1} = 3.7 {+-} 0.4, {Delta}H{sub 1}{degree} = {minus}10 {+-} 30 kJ/mol, {Delta}S{sub 1}{degree} = 40 {+-} 100 J/K{center_dot}mol and {Delta}C{sub p 1}{degree} = 1900 {+-} 800 J/K{center_dot}mol; whereas the values for Al(SO{sub 4}){sub 2}{sup {minus}} are: logK{sub 2} = 5.6 {+-} 0.7, {Delta}H{sub 2}{degree} = 10 {+-} 50 kJ/mol, {Delta}S{sub 2}{degree} = 100 {+-} 100 J/K{center_dot}mol and {Delta}C{sub p 2}{degree} = 2800 {+-} 800 J/K{center_dot}mol. A solubility study, which was undertaken to verify the 50 C potentiometric data, was performed by reacting powdered gibbsite (Al(OH){sub 3}) with sulphate solutions at 10{sup {minus}3.5} and 10{sup {minus}4} molal H{sup +}, total sulphate concentrations from 0.005 to 0.080 molal, and 0.1 and 1.0 molal ionic strength in aqueous NaCl media. The results of the solubility study are in good agreement with the potentiometric data and establish that Al-sulphate complexation substantially enhances the equilibrium solubility of gibbsite.

  4. Improved Dark Energy Constraints From ~ 100 New CfA Supernova Type Ia Light Curves

    SciTech Connect

    Hicken, Malcolm; Wood-Vasey, W.Michael; Blondin, Stephane; Challis, Peter; Jha, Saurabh; Kelly, Patrick L.; Rest, Armin; Kirshner, Robert P.; /Harvard-Smithsonian Ctr. Astrophys.

    2012-04-06

    We combine the CfA3 supernovae Type Ia (SN Ia) sample with samples from the literature to calculate improved constraints on the dark energy equation of state parameter, w. The CfA3 sample is added to the Union set of Kowalski et al. to form the Constitution set and, combined with a BAO prior, produces 1 + w = 0.013{sub -0.068}{sup +0.066} (0.11 syst), consistent with the cosmological constant. The CfA3 addition makes the cosmologically useful sample of nearby SN Ia between 2.6 and 2.9 times larger than before, reducing the statistical uncertainty to the point where systematics play the largest role. We use four light-curve fitters to test for systematic differences: SALT, SALT2, MLCS2k2 (R{sub V} = 3.1), and MLCS2k2 (R{sub V} = 1.7). SALT produces high-redshift Hubble residuals with systematic trends versus color and larger scatter than MLCS2k2. MLCS2k2 overestimates the intrinsic luminosity of SN Ia with 0.7 < {Delta} < 1.2. MLCS2k2 with R{sub V} = 3.1 overestimates host-galaxy extinction while R{sub V} {approx} 1.7 does not. Our investigation is consistent with no Hubble bubble. We also find that, after light-curve correction, SN Ia in Scd/Sd/Irr hosts are intrinsically fainter than those in E/S0 hosts by 2{sigma}, suggesting that they may come from different populations. We also find that SN Ia in Scd/Sd/Irr hosts have low scatter (0.1 mag) and reddening. Current systematic errors can be reduced by improving SN Ia photometric accuracy, by including the CfA3 sample to retrain light-curve fitters, by combining optical SN Ia photometry with near-infrared photometry to understand host-galaxy extinction, and by determining if different environments give rise to different intrinsic SN Ia luminosity after correction for light-curve shape and color.

  5. IMPROVED DARK ENERGY CONSTRAINTS FROM {approx}100 NEW CfA SUPERNOVA TYPE Ia LIGHT CURVES

    SciTech Connect

    Hicken, Malcolm; Challis, Peter; Kirshner, Robert P.; Wood-Vasey, W. Michael; Blondin, Stephane; Jha, Saurabh; Kelly, Patrick L.; Rest, Armin E-mail: kirshner@cfa.harvard.edu

    2009-08-01

    We combine the CfA3 supernovae Type Ia (SN Ia) sample with samples from the literature to calculate improved constraints on the dark energy equation of state parameter, w. The CfA3 sample is added to the Union set of Kowalski et al. to form the Constitution set and, combined with a BAO prior, produces 1 + w = 0.013{sup +0.066} {sub -0.068} (0.11 syst), consistent with the cosmological constant. The CfA3 addition makes the cosmologically useful sample of nearby SN Ia between 2.6 and 2.9 times larger than before, reducing the statistical uncertainty to the point where systematics play the largest role. We use four light-curve fitters to test for systematic differences: SALT, SALT2, MLCS2k2 (R{sub V} = 3.1), and MLCS2k2 (R{sub V} = 1.7). SALT produces high-redshift Hubble residuals with systematic trends versus color and larger scatter than MLCS2k2. MLCS2k2 overestimates the intrinsic luminosity of SN Ia with 0.7 < {delta} < 1.2. MLCS2k2 with R{sub V} = 3.1 overestimates host-galaxy extinction while R{sub V} {approx} 1.7 does not. Our investigation is consistent with no Hubble bubble. We also find that, after light-curve correction, SN Ia in Scd/Sd/Irr hosts are intrinsically fainter than those in E/S0 hosts by 2{sigma}, suggesting that they may come from different populations. We also find that SN Ia in Scd/Sd/Irr hosts have low scatter (0.1 mag) and reddening. Current systematic errors can be reduced by improving SN Ia photometric accuracy, by including the CfA3 sample to retrain light-curve fitters, by combining optical SN Ia photometry with near-infrared photometry to understand host-galaxy extinction, and by determining if different environments give rise to different intrinsic SN Ia luminosity after correction for light-curve shape and color.

  6. Seasonal Variations in the Flux and Isotopic Composition of Nitrate in the Upper Illinois River

    NASA Astrophysics Data System (ADS)

    Huang, S.; Sturchio, N. C.; Gonzales-Meler, M.; Bohlke, J. F.; Sopcak, M.

    2005-12-01

    The Upper Illinois River is a primary channel for transportation and receives effluent of municipal and industrial wastewater treatment facilities as well as runoff from urbanized and agricultural land within its watershed. Archived data on river discharge and nitrate concentrations are available from long-term monitoring programs of the USGS and the Metropolitan Water Reclamation District of Greater Chicago (MWRDGC). These data show that water discharge and nitrate concentration in the Upper Illinois River vary seasonally. The isotopic composition of N and O in dissolved nitrate was measured during October 2004 and May 2005, in conjunction with the seasonal water quality monitoring program of the MWRDGC, at 49 mid-channel sampling points along a 133-mile segment of the Illinois River from Lockport to Peoria. The purpose of this study is to determine the extent to which isotopic data can be used to identify and quantify the sources and fate of nitrate in the Illinois River. In October 2004, the nitrate flux decreased from approx. 3 kg/sec at Lockport to approx. 1 kg/sec at Peoria, while the N and O isotopic compositions changed from delta-15N = +7.8, delta-18O = +0.10 at Lockport to delta-15N = +13.5, delta-18O = +5.4 at Peoria. The decrease in nitrate flux and the positively correlated increases in delta-15N and delta-18O are consistent with the interpretation that the major input of nitrate to the Upper Illinois River occurred upstream of Lockport and substantial denitrification or assimilation may have occurred downstream from Lockport. In contrast, during May 2005, the nitrate flux increased from approx. 2 kg/sec at Lockport to approx. 10 kg/sec at Peoria, while the N and O isotopic compositions changed from delta-15N = +9.7, delta-18O = +2.3 at Lockport to delta-15N = +8.9, delta-18O = +6.5 at Peoria. The increase in nitrate flux and the inverse relation between delta-15N and delta-18O are consistent with the interpretation that the major input of nitrate

  7. Overview of Results from the National Spherical Torus Experiment (NSTX)

    SciTech Connect

    Gates, D; Ahn, J; Allain, J; Andre, R; Bastasz, R; Bell, M; Bell, R; Belova, E; Berkery, J; Betti, R; Bialek, J; Biewer, T; Bigelow, T; Bitter, M; Boedo, J; Bonoli, P; Bozzer, A; Brennan, D; Breslau, J; Brower, D; Bush, C; Canik, J; Caravelli, G; Carter, M; Caughman, J; Chang, C; Choe, W; Crocker, N; Darrow, D; Delgado-Aparicio, L; Diem, S; D'Ippolito, D; Domier, C; Dorland, W; Efthimion, P; Ejiri, A; Ershov, N; Evans, T; Feibush, E; Fenstermacher, M; Ferron, J; Finkenthal, M; Foley, J; Frazin, R; Fredrickson, E; Fu, G; Funaba, H; Gerhardt, S; Glasser, A; Gorelenkov, N; Grisham, L; Hahm, T; Harvey, R; Hassanein, A; Heidbrink, W; Hill, K; Hillesheim, J; Hillis, D; Hirooka, Y; Hosea, J; Hu, B; Humphreys, D; Idehara, T; Indireshkumar, K; Ishida, A; Jaeger, F; Jarboe, T; Jardin, S; Jaworski, M; Ji, H; Jung, H; Kaita, R; Kallman, J; Katsuro-Hopkins, O; Kawahata, K; Kawamori, E; Kaye, S; Kessel, C; Kim, J; Kimura, H; Kolemen, E; Krasheninnikov, S; Krstic, P; Ku, S; Kubota, S; Kugel, H; La Haye, R; Lao, L; LeBlanc, B; Lee, W; Lee, K; Leuer, J; Levinton, F; Liang, Y; Liu, D; Luhmann, N; Maingi, R; Majeski, R; Manickam, J; Mansfield, D; Maqueda, R; Mazzucato, E; McCune, D; McGeehan, B; McKee, G; Medley, S; Menard, J; Menon, M; Meyer, H; Mikkelsen, D; Miloshevsky, G; Mitarai, O; Mueller, D; Mueller, S; Munsat, T; Myra, J; Nagayama, Y; Nelson, B; Nguyen, X; Nishino, N; Nishiura, M; Nygren, R; Ono, M; Osborne, T; Pacella, D; Park, H; Park, J; Paul, S; Peebles, W; Penaflor, B; Peng, M; Phillips, C; Pigarov, A; Podesta, M; Preinhaelter, J; Ram, A; Raman, R; Rasmussen, D; Redd, A; Reimerdes, H; Rewoldt, G; Ross, P; Rowley, C; Ruskov, E; Russell, D; Ruzic, D; Ryan, P; Sabbagh, S; Schaffer, M; Schuster, E; Scott, S; Shaing, K; Sharpe, P; Shevchenko, V; Shinohara, K; Sizyuk, V; Skinner, C; Smirnov, A; Smith, D; Smith, S; Snyder, P; Soloman, W; Sontag, A; Soukhanovskii, V; Stoltzfus-Dueck, T; Stotler, D; Strait, T; Stratton, B; Stutman, D; Takahashi, R; Takase, Y; Tamura, N; Tang, X; Taylor, G; Taylor, C; Ticos, C; Tritz, K; Tsarouhas, D; Turrnbull, A; Tynan, G; Ulrickson, M; Umansky, M; Urban, J; Utergberg, E; Walker, M; Wampler, W; Wang, J; Wang, W; Weland, A

    2009-01-05

    The mission of NSTX is the demonstration of the physics basis required to extrapolate to the next steps for the spherical torus (ST), such as a plasma facing component test facility (NHTX) or an ST based component test facility (ST-CTF), and to support ITER. Key issues for the ST are transport, and steady state high {beta} operation. To better understand electron transport, a new high-k scattering diagnostic was used extensively to investigate electron gyro-scale fluctuations with varying electron temperature gradient scale-length. Results from n = 3 braking studies confirm the flow shear dependence of ion transport. New results from electron Bernstein wave emission measurements from plasmas with lithium wall coating applied indicate transmission efficiencies near 70% in H-mode as a result of reduced collisionality. Improved coupling of High Harmonic Fast-Waves has been achieved by reducing the edge density relative to the critical density for surface wave coupling. In order to achieve high bootstrap fraction, future ST designs envision running at very high elongation. Plasmas have been maintained on NSTX at very low internal inductance l{sub i} {approx} 0.4 with strong shaping ({kappa} {approx} 2.7, {delta} {approx} 0.8) with {beta}{sub N} approaching the with-wall beta limit for several energy confinement times. By operating at lower collisionality in this regime, NSTX has achieved record non-inductive current drive fraction f{sub NI} {approx} 71%. Instabilities driven by super-Alfvenic ions are an important issue for all burning plasmas, including ITER. Fast ions from NBI on NSTX are super-Alfvenic. Linear TAE thresholds and appreciable fast-ion loss during multi-mode bursts are measured and these results are compared to theory. RWM/RFA feedback combined with n = 3 error field control was used on NSTX to maintain plasma rotation with {beta} above the no-wall limit. The impact of n > 1 error fields on stability is a important result for ITER. Other highlights are

  8. Fabrication, characterization, and analysis of nanofabricated ion damage high temperature Josephson junctions

    NASA Astrophysics Data System (ADS)

    Katz, Andrew Steven

    The 1986 discovery of high temperature superconductivity in copper oxide perovskite compounds (a.k.a., cuprates) set off an avalanche of research with the twin goals of understanding the origin of the superconducting state and of developing practical superconducting technologies. Proponents of superconducting technology were renewed with the possibility of achieving devices with cheaper, simpler coolants such as liquid nitrogen rather than the more expensive and exotic liquid helium. While the underlying origin of the superconducting state in the cuprates is still elusive, great strides towards applications of the new superconductors have been made over the past decade. The primary element in active superconducting electronics is the Josephson junction. In the case of the cuprates, numerous techniques have been tried to produce Josephson junctions for use in superconducting electronics. Each has some advantages and some limitations. None to date, however, have been reliable enough to imagine manufacturing devices with more than a few Josephson elements. High temperature superconducting electronics of the future will require the reliable and reproducible fabrication of dozens and even hundreds of Josephson elements on a single chip. This dissertation attempts to address this problem by presenting a technique for fabricating reliable, reproducible, controllable, and manufacturable Josephson junctions in the superconductor YBasb2Cusb3CuOsb{7-delta}. A process has been developed to fabricate planar high-Tsb{c} Josephson junctions using nanolithography and a 200 keV ion implanter. Conduction occurs in the ab-plane and is interface free. Devices may be tuned to operate at temperatures between 1 K and the Tsb{c} of the undamaged superconducting material by varying the length of the weak link and by changing the amount of ion damage. The normal state and superconducting state properties of these films have been examined and analyzed in the contexts of a de Gennes dirty

  9. Multiple origins of Canadian Cordilleran gold deposits: geochemical characteristics

    SciTech Connect

    Murowchick, J.B.; Nesbitt, B.E.; Muehlenbachs, K.

    1985-01-01

    Two types of lode Au mineralization (Mother Lode and Epithermal) can be recognized in the Canadian Cordillera by geochemical characteristics. The Coquihalla Au belt, a typical ML district, has steeply-dipping Q-cc-ab-Au veins. Host rocks are greywackes, slates and greenstones in fault contact with a serpentinite body. Isotopic analyses: Q-cc and antigorite-mt paris gives temperatures around 250/sup 0/C. delta/sup 18/O/sub SMOW/ are exceptionally high: vein Q = 16 to 18 per thousand, antigorite = 7.4 to 9.5 per thousand, and cc = 14 to 18 per thousand with delta/sup 13/C/sub PDB/ =-2.9 to -6.9 per thousand. deltaD are low: -111 to -142 for the serpentines and -84 to -100 for fluid inclusion waters extracted by crushing vein Q. These fluids have low salinity and contain CO/sub 2/. The delta/sup 18/O for the ore fluid is about 8 per thousand and was also the serpentinizing fluid. The deltaD suggest that the fluid was dominantly meteoric, but evolved by reaction with the metasediments during deep circulation. The typical ML assemblage is Q-cc-ab with aspy, py, po, Au, +/-AU tellurides +/- scheelite; Au/Ag = 4 to 7 in this belt. Other ML deposits in BC show similar isotopic and mineralogic traits. Epithermal deposits in the Canadian Cordillera are comparable to well-studied US examples: their fluids were shallow-circulated meteoric waters (delta/sup 18/O=-14 to -7), delta/sup 18/O=-5 to +2, T=200-300/sup 0/C, Au/Ag<1, and have Q, chalcedony, cc, hematite, adularia, barite, py, cpy, Ag/sub 2/S, Au, electrum and anomalous Hg, As, and Tl contents. The association of Hg and Sb occurrences near many B.C. ML deposits suggests that these may be the epithermal expression of deeper ML mineralization.

  10. The Dopants and Doping Level Dependence of the Structure and Magnetic Properties of the Eu (BA1-xLRx)2Cu3O7+Theta

    SciTech Connect

    Yu Lin

    2002-12-31

    Eu(Ba{sub 1-x}Nd{sub x}){sub 2}Cu{sub 3}O{sub 7+{delta}} were systematically studied in order to understand how the valence of the rear earth elements, ionic sizes and magnetic moment affect the crystal structure and magnetic and electrical properties. Differential thermal analyses were carried out to check the phase purity, X-ray data were least-squares fitted to determine the lattice parameters, and DC-SQUID magnetometry was used to characterize the superconducting properties. These results showed that the crystallography is consistent with other EuLR123ss series, LR = La, Pr, Eu. The lattice parameters vary with the ionic radii of the rare earth ions. Unlike the uniform change in lattice parameter, the superconducting transition did not vary systematically with the ionic size of the dopants. Although the general trend was for T{sub c} to decrease with decreasing ionic size of the dopant, for the same doping level, Pr was anomalous, depressing T{sub c} faster. Although the exact mechanism is not clear, this result is consistent with the depression of T{sub c} for Pr substitution for the rare earth in R123. The critical current J{sub c} was determined using the Bean model from magnetization versus field measurements as a function of temperature and field. The effect of the dopants on J{sub c} with the increasing of temperature or applied field was determined. For T < 77 K and small values of x, the value of J{sub c} was increased over that of the x = 0 sample. In addition, the smaller the substituting atom, the higher the J{sub c} becomes. For instance, at x = 0.025, Eu123 < EuLa.025 < EuPr.025 < EuNd.025 < EuEu.025. The enhancement of J{sub c} disappears for x > 0.05 and T > 0.5T{sub c}.

  11. Infrared Detection with High Transition Temperature Bolometers and Response of Niobium Tunnel Junctions to Picosecond Voltage Pulses.

    NASA Astrophysics Data System (ADS)

    Verghese, Simon

    1993-01-01

    Oxide superconductors with high critical temperature T_{rm c} make sensitive thermometers for several types of infrared bolometers. We built composite bolometers with rm YBa_2Cu _3O_{7-delta} thermometers on sapphire substrates which have higher sensitivity than competing thermal detectors which operate at temperatures above 77 K. A 1 x 1 mm bolometer with gold black serving as the radiation absorber has useful sensitivity for wavelengths 20-100 mum. A 3 x 3 mm bolometer with a bismuth film as the absorber operates from 20-100 mum. High-T_{ rm c} bolometers which are fabricated with micromachining techniques on membranes of Si or Si _3N_4 have potential application to large-format arrays which are used for infrared imaging. Thermal isolation is achieved by suspending the membrane on two thin legs of the membrane material. A nonisothermal high-T_{ rm c} bolometer can be fabricated on a membrane of yttria-stabilized zirconia (YSZ) which is in thermal contact with the heat sink along the perimeter of the membrane. A thermal analysis indicates that the YSZ membrane bolometer can have improved sensitivity compared to the sapphire bolometer for spectrometer applications. The quasiparticle tunneling current in a superconductor -insulator-superconductor (SIS) junction is highly nonlinear in the applied voltage. If an SIS junction is excited with photons of energy hbaromega, where hbaromega/e is larger than the width of the nonlinearity in the I-V curve, the response of the quasiparticle current is retarded and depends strongly on omega. We have made the first measurement of the linear response of the quasiparticle current in a Nb/AlO_{rm x} /Nb junction over a broad bandwidth from 75-200 GHz. We used picosecond pulses of millimeter wave radiation which were generated by illuminating a photoconductive switch with a mode-locked laser. The data are in agreement with the theory of linear photon-assisted tunneling. Nonlinear measurements made with these pulses may provide

  12. Hydrostatic pressure study on high temperature superconductors: HgBa(2)Casb(m-1)Cu(m)O(2m+2+delta) (m = 1 to 6) and (Cu,C)Ba(2)Ca(m-1)Cu(m)O(2m+3) (m = 3 and 4)

    NASA Astrophysics Data System (ADS)

    Cao, Yong

    1998-12-01

    Over the last decade, numerous extensive as well as intensive experimental and theoretical investigations have been carried out since the great discovery of high temperature superconductivity (HTSy) in cuprate superconductors Lasb{2-x}Basb{x}CuOsb4,\\ YBasb2Cusb2Osb{7-delta} and other compounds. Although there is still no widely accepted microscopic theory on the mechanism responsible for such high superconducting transition temperatures (Tsb{c}), systematic trends of the evolution of HTSy with various parameters have been studied and analyzed. One of them is the universal inverse parabolic correlation between the Tsb{c} and the number of carriers per CuOsb2 plane (n) in various cuprate superconductors. The high pressure technique provides a clean way to change the distance between atoms without causing the side effects typical of chemical doping, and thus has long been used to test and provide guidance for theoretical models, as well as give hints about the synthesis of compounds with higher Tsb{c}. Therefore, we have done a systematic study on the pressure effect on Tsb{c} of two homologous superconducting compound series: HgBasb2Casb{m-1}Cusb{m}Osb{2m+2+delta} (Hg-12(m-1)m) (m = 1 to 6) and (Cu,C)Basb2Casb{m-1}Cusb{m}Osb{2m+3+delta} ((Cu,C)-12(m-1)m) (m = 3 and 4). Several factors which influence the hydrostatic pressure effect on Tsb{c} have been systematically analyzed. They include the n, the type of charge reservoir layer, and the number of CuOsb2 layers per unit cell (m). We came to several conclusion: (1) The inverse parabolic Tsb{c}(n) correlation and its universal parameters are valid only under conditions more restrictive than originally expected, and the rigid band model may not hold for some cuprate superconductors under pressure. (2) The pressure coefficient (dTsb{c}/dP) may have a different dependence on n. The compounds with Cu-O chains in their charge reservoir usually show a large linear variation of dTsb{c}/dP with n, while no significant

  13. Aspects of the SrO-CuO-TiO2 Ternary System Related to the Deposition of SrTiO3 and Copper-Doped SrTiO3 Thin-Film Buffer Layers

    SciTech Connect

    A. Ayala

    2004-12-20

    YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO) coated conductors are promising materials for large-scale superconductivity applications. One version of a YBCO coated conductor is based on ion beam assisted deposition (IBAD) of magnesium oxide (MgO) onto polycrystalline metal substrates. SrTiO{sub 3} (STO) is often deposited by physical vapor deposition (PVD) methods as a buffer layer between the YBCO and IBAD MgO due to its chemical stability and lattice mismatch of only {approx}1.5% with YBCO. In this work, some aspects of the stability of STO with respect to copper (Cu) and chemical solution deposition of STO on IBAD MgO templates were examined. Solubility limits of Cu in STO were established by processing Cu-doped STO powders by conventional bulk preparation techniques. The maximum solubility of Cu in STO was {approx}1% as determined by transmission electron microscopy (TEM) and Rietveld refinements of x-ray diffraction (XRD) data. XRD analysis, performed in collaboration with NIST, on powder compositions on the STO/SrCuO{sub 2} tie line did not identify any ternary phases. SrCu{sub 0.10}Ti{sub 0.90}O{sub y} buffer layers were prepared by pulsed laser deposition (PLD) and CSD on IBAD MgO flexible metallic textured tapes. TEM analysis of a {approx}100 nm thick SrCu{sub 0.10}Ti{sub 0.90}O{sub y} buffer layer deposited by PLD showed a smooth Cu-doped STO/MgO interface. A {approx}600 nm thick YBCO film, deposited onto the SrCu{sub 0.10}Ti{sub 0.90}O{sub y} buffer by PLD, exhibited a T{sub c} of 87 K and critical current density (J{sub c}) of {approx}1 MA/cm{sup 2}. STO and Cu-doped STO thin films by CSD were {approx}30 nm thick. The in plane alignment (FWHM) after deposition of the STO improved by {approx}1{sup o} while it degraded by {approx}2{sup o} with the SrCu{sub 0.05}TiO{sub y} buffer. YBCO was deposited by PLD on the STO and SrCu{sub 0.05}TiO{sub y} buffers. The in plane alignment (FWHM) of the YBCO with the STO buffer layer slightly improved while that of the

  14. Novel processing and properties of high efficiency superconducting infrared bolometric detectors

    NASA Astrophysics Data System (ADS)

    Moxey, Donovan E.

    1998-12-01

    The work in this dissertation involves the design, fabrication, and analysis of superconducting infrared bolometric detectors. These bolometers have been made from superconducting YBasb2Cusb3Osb{7-delta} (YBCO) deposited on silicon (100) substrates utilizing a buffer layer of yttria stabilized zirconia (YSZ). Thin films of undoped and silver(Ag) doped YBCO, as well as stacked layers of undoped/Ag-doped YBCO have been deposited by pulsed laser deposition (PLD). The microstructure and materials properties of these films have been studied using X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and secondary ion mass spectroscopy (SIMS). The electrical and transport properties of these films have been investigated using four-point resistance versus temperature measurements. The results of the investigations of the materials and electrical properties of these films show that they are of high quality, and exhibit superconducting characteristics that are conducive for bolometer device applications. For the first time superconducting bolometric detectors have been fabricated using a novel photolithographic and anti-reflective coating (ARC) process. This fabrication process can be used to fabricate any type of device structure that utilizes superconducting YBCO. The use of an anti-reflective coating simplifies the overall device fabrication process and allows this process to be easily integrated with conventional silicon device processing steps. The anti-reflective coating serves as a barrier to moisture and other contaminants that react with YBCO, as well as act as an absorption medium that improves the optical collection efficiency of the device. Optical analysis of these three bolometer device structures has been carried out using a helium neon (HeNe; lambda = 632.8nm) laser. At a bias of 1mA, and chopping frequency of 100Hz; we have measured photoresponse as a function of device temperature, calculated responsivity, and

  15. Time-resolved magnetic flux and AC-current distributions in superconducting yttrium barium copper oxide thin films and multifilaments

    NASA Astrophysics Data System (ADS)

    Yang, Ran

    Time-resolved magneto-optical imaging (TRMOI) technique allows dynamic ac transport measurements on superconductors. The high time and spatial resolutions of the measurements also offer good quantitative data analysis of the MO images. YBa2Cu 3O7-delta (YBCO) was discovered as a high-temperature superconductor (HTSC) which has wide applications due to its high critical temperature of Tc = 91 K, and high critical current density Jc in the order of 106-7 Acm-2. Many of the applications require high ac current load and a high magnetic field. We study the interaction behavior of YBCO thin films in an ac transport current and a dc magnetic field by the TRMOI technique. In this dissertation, I first introduce the applications of high-temperature superconductors with focus on YBCO and describe the advantages of the TRMOI technique we developed over other methods to map the magnetic flux distribution of superconductors. The theories to understand the magnetic properties of HTSC are presented, followed by theoretical models. I also introduce a newly developed finite elemental method (FEM) simulation which is proved to be a better theoretical guideline to our data analysis. The TRMOI experimental setup and the procedures are discussed in detail. I show step-by-step the calibration of light intensity profiles averaged from MO images to determine magnetic field distribution, and a numerical inversion of the Biot-Savart law to calculate the current density distributions. The current density evolution in YBCO thin films is studied by TRMOI as a function of the phase of an ac current applied simultaneously with a perpendicular dc magnetic field. The measurements show that an ac current enables the vortex matter in YBCO thin films to reorganize into two coexisting steady states of driven vortex motion with different characteristics. To study the transport current effects in YBCO thin films, we present a new empirical method to separate the total current distribution into a

  16. Synthesis, Characterization, Phase Diagrams and Superconducting and Normal State Magnetic Properties of LANTHANUM(2-X) Strontium(x) Copper OXYGEN(4) (0 <= X <= 0.08) and Electrochemically Oxidized LANTHANUM(2-X) Strontium(x) Copper OXYGEN(4+DELTA) (0 <= X <= 0.33, 0 <= Delta <= 0.12)

    NASA Astrophysics Data System (ADS)

    Chou, Fangcheng

    La_{2-x}Sr _{x}CuO _4 (0 <= x <= 0.15) can all be intercalated with oxygen by an novel electrochemical oxidation method. Bulk superconductivity is found with an onset T_{c} ~ 40 K for the whole range 0.01 <= x <= 0.15; for x = 0.25 and 0.33, the electrochemical oxidation did not improve the superconducting properties. The magnetic susceptibility chi(T = 50-320 K) data for La _2CuO_{4.11} and La_{1.92}Sr _{0.08}CuO_{4.07 } are nearly identical with those of conventionally prepared La_{1.85}Sr _{0.15}CuO_4, indicating that the hole doping level (p) in the CuO _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 -1. The maximum doped -hole concentration in the CuO_2 planes that can be achieved from combined Sr-doping and electrochemical oxygen doping for 0 <= x <= 0.15 is p ~ 0.16 holes/formula unit. Oxygen can also intercalate into single crystal La_2CuO_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_2CuO _{4+delta} as well as of YBa_2Cu_3O _{7-delta} and La _{2-x}Sr _{x}CuO_4 single crystals. The single crystal La _2CuO_{4+delta } has a maximum T_{c} ~ 40 K, which is lower than that (T_{c} ~ 42-45) of the corresponding polycrystalline samples. The magnetic phase diagram of La_ {2-x}Sr_{x}CuO_4 in the antiferromagnetic (AF) regime (0 <= x <= 0.02) has been derived from ^{139}La NQR studies from 4 to 250 K. The data demonstrate localization of the doped holes' charge below ~30 K, followed by freezing of the holes' effective spin degrees of freedom below T_{f} ~ (815 x) K into a spin

  17. The Growth and Characterization of Germanium-Carbon Alloy Thin Films and Solid Phase Equilibria for Metal-Silicon - Ternary Systems: Magnesium, Calcium, Strontium, Barium, Scandium, Yttrium, Lanthanum, Titanium, Zirconium and Hafnium

    NASA Astrophysics Data System (ADS)

    Yuan, Haojie

    1992-09-01

    that the film grown contains a mixture of sp^2 and sp^3 hybridized carbon. By using x-ray powder diffraction and magnetic susceptibility measurements methods, we studied the chemical stability of candidate interlayer materials between YBa _2Cu_3O _7-delta and Si. The results show that CaF_2 reacts with YBCO while BaF_2 is chemically stable with YBCO. LaGaO_3 and Ca _2SiO_4 are chemically stable with Si and more investigations need to be made on the reactivity between Ca_2SiO _4 and YBCO.

  18. A Magnetic Bumper-Tether System Using ZFC Y123

    NASA Technical Reports Server (NTRS)

    Weinstein, Roy; Parks, Drew; Sawh, Ravi-Persad; Obot, Victor; Liu, Jianxiong; Arndt, G. D.

    1996-01-01

    We consider the use of magnetic forces in a bumper system, to soften docking procedures. We investigate a system which exhibits no magnetic field except during the docking process, which, if desired, can automatically tether two craft together, and which provides lateral stability during docking. A system composed of zero field cooled Y(1.7)Ba2Cu3O(7-delta) (Y123) tiles and electromagnets is proposed. The Y123 high temperature superconductor (HTS) is mounted on one craft, and the electromagnet on the other. Results of small prototype laboratory experiments are reported. The electromagnet has, for convenience, been replaced by a permanent SmCo ferromagnet in these measurements. When the two craft approach, a mirror image of the ferromagnet is induced in the Y123, and a repulsive bumper force, F(sub B), results. F(sub B) is velocity dependent, and increases with v. For presently available HTS materials, bumper pressure of approx. 3.7 N/cm(exp 2) is achieved using SmCo. This extrapolates to approx. 18 N/cm(exp 2) for an electromagnet, or a force of up to 20 tons for a 1 m(exp 2) system. After reaching a minimum distance of approach, the two colliding craft begin to separate. However, the consequent change of SmCo magnetic field at the Y123 results in a reversal of current in the Y123 so that the Y123 is attractive to the SmCo. The attractive (tether) force, F(sub T), is a function of R = B(sub Fe)/B(sub t, max), where B(sub Fe) is the field at the surface of the ferromagnet, and B(sub t, max) is the maximum trapped field of the Y123, i.e., the trapped field in the so-called critical state. For R greater than or equal to 2, F(sub T) saturates at a value comparable to F(sub B). For a range of initial approach velocities the two craft are tethered following the bumper sequence. Most of the kinetic energy of the collision is first converted to magnetic field energy in the Y123, and then into heat via the creep mechanism. About 15% of the work done against magnetic forces

  19. Thermodynamics of the magnetic-field-induced "normal" state in an underdoped high Tc superconductor

    NASA Astrophysics Data System (ADS)

    Riggs, Scott Chandler

    High magnetic fields are used to kill superconductivity and probe what happens to system when it cannot reach the ideal ground state, i.e. what is the normal-state ground state? Early work in High-Tc, where the application of magnetic field destroyed the zero resistance state and recovered a resistivity value that connected continuously with the zero field curve, lead people to believe this magnetic-field-induced-state had fully driven the system normal, revealing the true underlying ground state, without any vestige of superconductivity. Many experiments done in this region of phase space have results interpreted as coming from the low energy ground state excitations. With the emergence of ultra-clean crystals in a unique family of hole doped high-Tc superconductors, YBa2Cu3O 7-delta, YBCO, a new and highly unexpected phenomena of quantum oscillations were discovered, and they followed the standard Liftshitz-Kosevich (LK) theory for a normal metal. The results suddenly made the problem of high-T c appear to be analogous to superconductivity in the organics, which is brought about by a wave-vector nesting and Fermi surface reconstruction. The only problem, it appeared, that needed to be reconciled was with Angle Resolved Photo-Emission Spectroscopy (ARPES) and Scanning Tunneling Microscopy (STM) data that claimed to see no such Fermi surface, instead only "arcs", a set of disconnected segments in the Brillouin zone which quasiparticle peaks are observed at the Fermi energy, which in a mean field description does not allow for a continuous Fermi surface contour. These two discrepancies led to the "arc vs pocket" debate, which is still unresolved. The other kink in the quantum oscillation armor is that, to this date, quantum oscillations in the hole-doped cuprates have only been seen in YBCO, the only cuprate structure to have CuO chains, which conduct and are located in between two CuO2 superconducting planes in the unit cell. In an attempt to reconcile the "arc vs

  20. Use of Physio-Hydrological Units for SMOS Validation at the Valencia Anchor Station Study Area

    NASA Astrophysics Data System (ADS)

    Millán-Scheiding, C.; Antolín, C.; Marco, J.; Soriano, M. P.; Torre, E.; Requena, F.; Carbó, E.; Cano, A.; Lopez-Baeza, E.

    2009-04-01

    The SMOS space mission will soil moisture over the continents and ocean surface salinity with the sufficient resolution to be used in global climate change studies. With the aim of validating SMOS land data and products at the Valencia Anchor Station site (VAS) in a Mediterranean Ecosystem area of Spain, we have designed a sample methodology using a subdivision of the landscape in environmental units related to the spatial variability of soil moisture (Millán-Scheiding, 2006; Lopez-Baeza, et al. 2008). These physio-hydrological units are heterogeneously structured entities which present a certain degree of internal uniformity of hydrological parameters. The units are delimited by integrating areas with the same physio-morphology, soil type, vegetation, geology and topography (Flugel, et al 2003; Millán-Scheiding et al, 2007). Each of these units presented over the same pedological characteristics, vegetation cover, and landscape position should have a certain degree of internal uniformity in its hydrological parameters and therefore similar soil moisture (SM). The main assumption for each unit is that the dynamical variation of the hydrological parameters within one unit should be minimum compared to the dynamics of another unit. This methodology will hopefully provide an effective sampling design consisting of a reduced number of measuring points, sparsely distributed over the area, or alternatively, using SM validation networks where each sampling point is located where it is representative of the mean soil moisture of a complete unit area. The Experimental Plan for the SMOS Validation Rehearsal Campaign at the VAS area of April-May 2008 used this environmental subdivision in the selection and sampling of over 21.000 soil moisture points in a control area of 10 x 10 km2. The ground measurements were carried out during 4 nights corresponding to a drying out period of the soil. The sampling consisted of 700 plots with 4 volumetric SM cylinders and 7 Delta-T Theta