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Sample records for anisotropic superconducting ybco

  1. Anisotropic properties of the fluctuational conductivity in YBCO

    NASA Astrophysics Data System (ADS)

    Sarti, S.; Boffa, V.; Fastampa, R.; Giura, M.; Marcon, R.; Silva, E.

    1996-03-01

    We report on resisitive transitions in YBCO films as a function of strength and orientation of the applied magnetic field. Angular behaviour is found to be markedly different in the upper and lower part of the transition. At high dissipation level, and angular scaling behaviour is observed, following the anisotropic Lawerence-Doniach expression for the upper critical field. The scaling breaks down at the midpoint of the transition. No scaling is observed at lower temperatures, even if different angular scaling functions are used. The results are very well interpreted in terms of superconducting fluctuations above ρ/ρn=0.5 and pinning phenomena below.

  2. Synthesis of nanoscale superconducting YBCO by a novel technique

    NASA Astrophysics Data System (ADS)

    Xu, X. L.; Guo, J. D.; Wang, Y. Z.; Sozzi, A.

    2002-06-01

    A novel technique using citrate pyrolysis was developed to prepare nanoscale superconducting oxide materials. This paper describes the details on synthesizing nanocrystalline YBCO with a Tc of ∼80 K using this method. The morphology and structure of the nanoscale products were characterized by powder X-ray diffraction and scanning electron microscopy. The obtained YBCO grains have a mean particle size of 40-60 nm (for unannealed samples) and 100-150 nm (for the annealed products). The crystalline size was only ∼20 nm. Currently there are attempts at using such fine powder to fabricate longer superconducting tapes, which should induce a technical revolution in the production of superconducting tapes.

  3. Preparation of YBCO-BYTO and YBCO-BZO nanostructured superconducting films by chemical method

    NASA Astrophysics Data System (ADS)

    Garcés, P.; Coll, M.; Castro, H.; Puig, T.; Obradors, X.

    2017-01-01

    YBCO-BYTO6% and YBCO-BZO10% YBa2Cu3O7-d-Ba2YTaO6 6% (YBCO-BYTO6%) and YBa2Cu3O7--BaZrO3 10% (YBCO-BZO 10%) nanostructured films were grown by the Chemical Solution Deposition method, and compared with YBCO pure films. Films were deposited on YSZ substrates, with Ce0.9Zr0.1O2 and Ce0.6Zr0.4O2 buffer layers. They were characterized by GADDS X-ray diffraction, scanning electron microscopy (SEM) and inductive (SQUID) measurements of the critical temperature (Tc) and critical current density (Jc). It was found that YBCO-BZO10% films presented better superconducting properties (Tc=89.2K and Jc=1.3MA/cm2), probably due to an enhanced pinning force, originated by BZO nanoparticles. Additionally, it was found that these films have lower reactivity with the buffer layer.

  4. Evaluating Superconducting YBCO Film Properties Using X-Ray Photoelectron Spectroscopy (Postprint)

    DTIC Science & Technology

    2012-02-01

    AFRL-RZ-WP-TP-2012-0093 EVALUATING SUPERCONDUCTING YBCO FILM PROPERTIES USING X-RAY PHOTOELECTRON SPECTROSCOPY (POSTPRINT) Paul N. Barnes...2012 Conference Paper Postprint 01 January 2002 – 01 January 2004 4. TITLE AND SUBTITLE EVALUATING SUPERCONDUCTING YBCO FILM PROPERTIES USING X-RAY

  5. Fabrication of Large YBCO Superconducting Disks

    NASA Technical Reports Server (NTRS)

    Koczor, Ronald J.; Noever, David A.; Robertson, Glen A.

    1999-01-01

    We have undertaken fabrication of large bulk items to develop a repeatable process and to provide test articles in laboratory experiments investigating reported coupling of electromagnetic fields with the local gravity field in the presence of rotating superconducting disks. A successful process was developed which resulted in fabrication of 30 cm diameter annular disks. The disks were fabricated of the superconductor YBa2Cu3O(7-x). Various material parameters of the disks were measured.

  6. YBCO superconducting ring resonators at millimeter-wave frequencies

    NASA Technical Reports Server (NTRS)

    Chorey, Christopher M.; Kong, Keon-Shik; Bhasin, Kul B.; Warner, J. D.; Itoh, Tatsuo

    1991-01-01

    Microstrip ring resonators operating at 35 GHz were fabricated from laser ablated YBCO films deposited on lanthanum aluminate substrates. They were measured over a range of temperatures and their performances compared to identical resonators made of evaporated gold. Below 60 Kelvin the superconducting strip performed better than the gold, reaching an unloaded Q approximately 1.5 times that of gold at 25 K. A shift in the resonant frequency follows the form predicted by the London equations. The Phenomenological Loss Equivalence Method is applied to the ring resonator and the theoretically calculated Q values are compared to the experimental results.

  7. Anisotropic rectifying characteristics induced by the superconducting gap of YBa2Cu3O7-δ/Nb-doped SrTiO3 heterojunctions

    NASA Astrophysics Data System (ADS)

    Zhang, M. J.; Hao, F. X.; Zhang, C.; Liu, X.; Li, X. G.

    2015-11-01

    In this paper, we investigated the anisotropic rectifying characteristics of a YBa2Cu3O7-δ (YBCO)/Nb-doped SrTiO3 heterojunction in magnetic fields of up to 9 T by rotating the junction from H//c to H//ab of the YBCO film. From the temperature and field dependencies of the diffusion potential Vd, we found that the angle-resolved reductions of Vd from its original value, δVd, were induced by the anisotropic superconducting gap Δ of the YBCO. The anisotropic parameter obtained from Δ was close to that obtained from the angular-dependent upper critical fields of the YBCO. This heterojunction is helpful both in investigating the superconducting gap and in designing sensitive superconducting devices.

  8. Critical Exponents of the Superconducting Transition in Polycrystalline YBCO.

    NASA Astrophysics Data System (ADS)

    Joshi, R. J.; Hallock, R. B.; Taylor, J. A.

    1996-03-01

    We present results of measurements designed to study superconducting I-V scaling in samples of bulk YBCO with varying morphologies and at selected magnetic fields 0.5<= H<= 10 T. I-V isotherm measurements performed near the superconducting transition on the samples are consistent with recent predictions of I-V scaling, with critical exponents ν≈ 1.2-1.5 and z≈ 2.6-4. The values for ν are comparable to those previously(T.K. Worthington, E. Olsson, C.S. Nichols, T.M. Shaw and D.R. Clarke, Phys. Rev. B 43), 10538 (1991) . reported(R.H. Koch, V. Foglietti, W.J. Gallagher,G. Koren, A. Gupta and M.P.A. Fisher, Phys. Rev. Lett. 63), 1511 (1989).. The values for z are consistent with those reported by Tiernan and Hallock(W.M. Tiernan, R. Joshi and R.B. Hallock, Phys. Rev. B. 48), 3423 (1993). but are somewhat lower than what is predicted by the glassy models. The morpholoogy and magnetic field dependence of z will be described.

  9. Ultrasonic signatures at the superconducting and the pseudogap phase boundaries in YBCO cuprates.

    SciTech Connect

    Shehter, Arkady; Migliori, Albert; Betts, Jonathan B.; Balakirev, Fedor F.; McDonald, Ross David; Riggs, Scott C.; Ramshaw, Brad; Liang, Ruixing; Hardy, Walter N.; Bonn, Doug A.

    2012-08-28

    A major issue in the understanding of cuprate superconductors is the nature of the metallic state from which high temperature superconductivity emerges. Central to this issue is the pseudogap region of the doping-temperature phase diagram that extends from room temperature to the superconducting transition. Although polarized neutron scattering studies hint at magnetic order associated with the pseudogap, there is no clear thermodynamic evidence for a phase boundary. Such evidence has a straightforward physical interpretation, however, it is difficult to obtain over a temperature range wide enough to encompass both the pseudogap and superconducting phases. We address this by measuring the elastic response of detwinned single crystals, an underdoped YBCO{sub 6.60} with superconducting transition at T{sub c} = 61.6K and a slightly overdoped YBCO{sub 6.98} with T{sub c} = 88.0K. We observe a discontinuity in the elastic moduli across the superconducting transition. Its magnitude requires that pair formation is coincident with superconducting coherence (the onset of the Meissner effect). For both crystals the elastic response reveals a phase transition at the pseudogap boundary. In slightly overdoped YBCO that transition is 20K below T{sub c}, extending the pseudogap phase boundary inside the superconducting dome. This supports a description of the metallic state in cuprates where a pseudogap phase boundary evolves into a quantum critical point masked by the superconducting dome.

  10. YSZ buffer layers and YBCO superconducting tapes with enhanced biaxial alignment and properties

    NASA Astrophysics Data System (ADS)

    Savvides, N.; Gnanarajan, S.

    2003-05-01

    Commercial applications of YBa 2Cu 3O 7 (YBCO) superconducting cables require viable and scalable manufacturing processes. We have investigated the evolution of the biaxial alignment of yttria-stabilized zirconia (YSZ) buffer layers with increasing film thickness (50-900 nm) and report on a method of fabricating highly aligned YBCO tapes using a thin epitaxial YSZ buffer layer as template. The method employs magnetron and ion beam assisted deposition (IBAD) techniques followed by epitaxial growth to produce the buffer architectures IBAD-YSZ and epi-YSZ/IBAD-YSZ onto optically polished hastelloy metal substrates. Subsequent in situ deposition of YBCO films is used to determine the biaxial alignment at the surface of the buffer architecture, and to show that 100-200 nm thick epi-YSZ layers suffice to yield YBCO tapes that have enhanced biaxial alignment (Δ φ=9-10°) and high critical current densities: J c(77 K)=(1-2)×10 6 A cm -2 and J c(5 K,1 T)=8×10 6 A cm -2. Atomic force microscopy of the surface microstructure of the YSZ buffer layers and YBCO films reveals some grain coarsening in the epi-YSZ layers compared to the IBAD-YSZ layers while the YBCO tapes show significant outgrowths (∼200 nm) and large grains (800-1200 nm) that are similar to high- Jc YBCO films grown on single crystal MgO(1 0 0) substrates.

  11. Exfoliated YBCO filaments for second-generation superconducting cable

    NASA Astrophysics Data System (ADS)

    Solovyov, Vyacheslav; Farrell, Paul

    2017-01-01

    The second-generation high temperature superconductor (2G HTS) wire is the most promising conductor for high-field magnets such as accelerator dipoles and compact fusion devices. The key element of the wire is a thin Y1Ba2Cu3O7 (YBCO) layer deposited on a flexible metal substrate. The substrate, which becomes incorporated in the 2G conductor, reduces the electrical and mechanical performance of the wire. This is a process that exfoliates the YBCO layer from the substrate while retaining the critical current density of the superconductor. Ten-centimeter long coupons of exfoliated YBCO layers were manufactured, and detailed structural, electrical, and mechanical characterization were reported. After exfoliation, the YBCO layer was supported by a 75 μm thick stainless steel foil, which makes for a compact, mechanically stronger, and inexpensive conductor. The critical current density of the filaments was measured at both 77 K and 4.2 K. The exfoliated YBCO retained 90% of the original critical current. Similarly, tests in an external magnetic field at 4.2 K confirmed that the pinning strength of the YBCO layer was also retained following exfoliation.

  12. Fishtail Effect Due To Silver Influenced Sub-precipitate Microstructure in YBCO/Ag Superconducting Composites

    NASA Astrophysics Data System (ADS)

    Parthasarathy, R.; Kumar, N. Devendra; Bai, V. Seshu

    2011-07-01

    We report the existence of a sub-precipitate microstructure and the resulting fishtail effect in YBCO/Ag superconducting composites fabricated by Seeded Infiltration and Growth Processing. The SEM micrographs reveal sub-precipitate microstructure in the form of precipitates of size less than 100 nm within the larger non-superconducting Y-211 precipitates that contributes to the enhancement of Jc in the form of secondary peak effect at lower fields.

  13. Passivation of Flexible YBCO Superconducting Current Lead With Amorphous SiO2 Layer

    NASA Technical Reports Server (NTRS)

    Johannes, Daniel; Webber, Robert

    2013-01-01

    Adiabatic demagnetization refrigerators (ADR) are operated in space to cool detectors of cosmic radiation to a few 10s of mK. A key element of the ADR is a superconducting magnet operating at about 0.3 K that is continually energized and de-energized in synchronism with a thermal switch, such that a piece of paramagnetic salt is alternately warm in a high magnetic field and cold in zero magnetic field. This causes the salt pill or refrigerant to cool, and it is able to suck heat from an object, e.g., the sensor, to be cooled. Current has to be fed into and out of the magnets from a dissipative power supply at the ambient temperature of the spacecraft. The current leads that link the magnets to the power supply inevitably conduct a significant amount of heat into the colder regions of the supporting cryostat, resulting in the need for larger, heavier, and more powerful supporting refrigerators. The aim of this project was to design and construct high-temperature superconductor (HTS) leads from YBCO (yttrium barium copper oxide) composite conductors to reduce the heat load significantly in the temperature regime below the critical temperature of YBCO. The magnet lead does not have to support current in the event that the YBCO ceases to be superconducting. Cus - tomarily, a normal metal conductor in parallel with the YBCO is a necessary part of the lead structure to allow for this upset condition; however, for this application, the normal metal can be dispensed with. Amorphous silicon dioxide is deposited directly onto the surface of YBCO, which resides on a flexible substrate. The silicon dioxide protects the YBCO from chemically reacting with atmospheric water and carbon dioxide, thus preserving the superconducting properties of the YBCO. The customary protective coating for flexible YBCO conductors is silver or a silver/gold alloy, which conducts heat many orders of magnitude better than SiO2 and so limits the use of such a composite conductor for passing current

  14. Coexistence of ferromagnetism and superconductivity in YBCO nanoparticles.

    PubMed

    Zhu, Zhonghua; Gao, Daqiang; Dong, Chunhui; Yang, Guijin; Zhang, Jing; Zhang, Jinlin; Shi, Zhenhua; Gao, Hua; Luo, Honggang; Xue, Desheng

    2012-03-21

    Nanoparticles of superconducting YBa(2)Cu(3)O(7-δ) were synthesized via a citrate pyrolysis technique. Room temperature ferromagnetism was revealed in the samples by a vibrating sample magnetometer. Electron spin resonance spectra at selected temperatures indicated that there is a transition from the normal to the superconducting state at temperatures below 100 K. The M-T curves with various applied magnetic fields showed that the superconducting transition temperatures are 92 K and 55 K for the air-annealed and the post-annealed samples, respectively. Compared to the air-annealed sample, the saturation magnetization of the sample by reheating the air-annealed one in argon atmosphere is enhanced but its superconductivity is weakened, which implies that the ferromagnetism maybe originates from the surface oxygen defects. By superconducting quantum interference device measurements, we further confirmed the ferromagnetic behavior at high temperatures and interesting upturns in field cooling magnetization curves within the superconducting region are found. We attributed the upturn phenomena to the coexistence of ferromagnetism and superconductivity at low temperatures. Room temperature ferromagnetism of superconducting YBa(2)Cu(3)O(7-δ) nanoparticles has been observed in some previous related studies, but the issue of the coexistence of ferromagnetism and superconductivity within the superconducting region is still unclear. In the present work, it will be addressed in detail. The cooperation phenomena found in the spin-singlet superconductors will help us to understand the nature of superconductivity and ferromagnetism in more depth.

  15. Microwave characterization of normal and superconducting states of MOCVD made YBCO tapes

    NASA Astrophysics Data System (ADS)

    Wosik, Jarek; Krupka, Jerzy; Qin, Kuang; Ketharnath, Dhivya; Galstyan, Eduard; Selvamanickam, Venkat

    2017-03-01

    We have used a microwave, non-contact, non-destructive, dielectric resonator (DR) technique to characterize complex conductivity of different quality YBCO/Hastelloy tapes for the purpose of exploring such a technique as a potential quality control method for fabrication of YBCO tapes. The tapes were deposited at different temperatures on Hastelloy-supported oxide buffer layers using the MOCVD technique. The buffer stack consisted of aluminum oxide (Al2O3), yttrium oxide (Y2O3), and textured ion beam assisted deposition-MgO and LaMnO3 layers. Two dielectric resonators (DRs), the single post DR, consisting of high-permittivity barium zirconium titanate ceramic operating at 13 GHz in quasi-TE01δ mode, and the rod DR, consisting of rutile single crystal disk operating at 9.4 GHz in-TE011 mode, were designed to meet sensitivity requirements for characterization of conductivity of the superconductor at normal and superconducting states, respectively. For calculations of complex conductivity from experimental data of Q-factor and resonant frequency shift, a commercial electromagnetic simulator HFSS, based on finite elements analysis, was used. The theoretical Q-factor and resonant frequency on conductivity functions obtained from full wave numerical simulations of microwave fields were matched with the experimental data to determine conductivity of the YBCO tapes in both normal and superconducting states. In addition, for comparison purposes, 280 nm thick high-quality YBCO epitaxial film deposited on a dielectric substrate was also characterized, including frequency dependence of the complex conductivity. Discussion about feasibility of using DR microwave techniques as a quality control tool via measurements of conductivity versus temperature slope of the YBCO/Hastelloy tape in normal state is included. Also, microwave conductivity values of Hastelloy substrate as a function of temperature are reported.

  16. Effect of Al and Ca co-doping, in the presence of Te, in superconducting YBCO whiskers growth.

    PubMed

    Pascale, Lise; Truccato, Marco; Operti, Lorenza; Agostino, Angelo

    2016-10-01

    High-Tc superconducting cuprates (HTSC) such as YBa2Cu3O7 - x (YBCO) are promising candidates for solid-state THz applications based on stacks of intrinsic Josephson junctions (IJJs) with atomic thickness. In view of future exploitation of IJJs, high-quality superconducting YBCO tape-like single crystals (whiskers) have been synthesized from Ca-Al-doped precursors in the presence of Te. The main aim of this paper is to determine the importance of the simultaneous use of Al, Te and Ca in promoting YBCO whiskers growth with good superconducting properties (Tc = 79-84 K). Further, single-crystal X-ray diffraction (SC-XRD) refinements of tetragonal YBCO whiskers (P4/mmm) are reported to fill the literature lack of YBCO structure investigations. All the as-grown whiskers have also been investigated by means of X-ray powder diffraction (XRPD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). Our results demonstrate that the interplay of Ca, Te and Al elements is clearly necessary in order to obtain superconducting YBCO whiskers. The data obtained from SC-XRD analyses confirm the highly crystalline nature of the whiskers grown. Ca and Al enter the structure by replacing the Y and the octahedral coordinated Cu1 site, respectively, as in other similar orthorhombic compounds, while Te does not enter the structure of whiskers but its presence in the precursor is essential to the growth of the crystals.

  17. Continued improvment of large area, in situ sputter deposition of superconducting YBCO thin films

    NASA Technical Reports Server (NTRS)

    Truman, J. K.; White, W. R.; Ballentine, P. H.; Mallory, D. S.; Kadin, A. M.

    1993-01-01

    The deposition of thin films of superconducting YBa2Cu3O7-x onto substrates of up to 3-in diameter by an integrated off-axis sputtering is reported. The substrate is located above the center of an 8-in-diameter YBCO planar target, and, in conjunction with a negative ion shield, negative ion effects are avoided. A large radiant heater provides backside, noncontact heating of the bare substrates. YBCO films have been grown on polished 1-cm2 MgO and LaAlO3 substrates with Tc = 90 K or greater, Jc = 2.5 x 10 exp 6 A/sq cm or greater at 77 K, and microwave surface resistance Rs less than 0.4 micro-ohm at 77 K and 10 GHz. The films have a very smooth surface morphology. Uniformity data for LaAlO3 substrates are less than +/-5 percent in Rs. Thickness uniformity results for 3-in substrates indicate less than 10 percent variation. The growth of epitaxial insulating films for use with YBCO films and application of the YBCO films in microwave devices are briefly discussed.

  18. Understanding the origin of the recovery of superconductivity in halogenated YBCO single crystal: Atomic structure study

    NASA Astrophysics Data System (ADS)

    Dieng, Lamine Mohamed Kollakoye

    The recovery of superconductivity in underdoped YBa2Cu 3O6+y (YBCO) by exposure to bromine, iodine, chlorine and fluorine is a long-standing problem which has not been clearly resolved. The key question concerns the role of these halogens in the lattice. In order to shed light to this problem, we have performed multiple-edge x-ray absorption fine structure (XAFS) measurements about the Y K, Ba L3, I L3, Cu K and Br K-edges at room temperature on brominated (non-brominated) and iodinated (non-iodinated) YBCO single crystals. Our XAFS results at the Br K (brominated) and I L3-edges (iodinated) reveal that bromine and iodine do not enter the perfect YBCO lattice. However, the XAFS fitting results at the Br K and I L3-edges reveal that Br and I do occupy the Cu(1) sites of the oxygen deficient YBCO in nanoclusters. From the polarized x-ray absorption near edge measurements (XANES) at the Cu K-edge, the nanoclusters were found to be randomly oriented with respect to the "host" crystal and with respect to the polarization vector.

  19. Iron-YBCO heterostructures and their application for trapped field superconducting motor

    NASA Astrophysics Data System (ADS)

    Granados, X.; Bartolomé, E.; Obradors, X.; Tornes, M.; Rodrigues, L.; Gawalek, W.; McCulloch, M.; Dew Hughes, D.; Campbell, A.; Coombs, T.; Ausloos, M.; Cloots, R.

    2006-06-01

    In this work we report on the magnetic behavior of the heterostructures formed by bulk based YBCO rings and ferromagnetic yoke. The magnetization cycle has been performed by an In-Field Hall Mapping technique. A video-like recording of the magnetization process makes it possible to obtain the magnetization of selected areas. The current flowing through the superconducting rings can be deduced from the magnetic field maps. The displacement of the peak of magnetization due to the flux reversal produced by the magnetization of the yoke is also considered. These hybrid heterostructures formed by ferromagnetic and superconducting material have been applied in the construction of the rotor for a brushless AC motor. The design and construction of this machine was carried out within the framework of the TMR Network SUPERMACHINES. The rotor has been designed in a quadrupolar configuration by cutting large YBCO ''window frames'' from seeded melt-textured single domain YBCO pellets. This rotor has been coupled to a conventional stator of copper coils wound on an iron armature. The stator can be excited both in bipolar or quadrupolar mode. We report on the behaviour of the motor after a field cooling process when excited in quadrupolar mode.

  20. Mechanical and Superconducting Properties of Ag/YBCO Composite Superconductors Reinforced by the Addition of Zr

    NASA Astrophysics Data System (ADS)

    Oka, Tetsuo; Ogasawara, Fumihiko; Itoh, Yoshitaka; Suganuma, Motohiro; Mizutani, Uichiro

    1990-10-01

    The composite high TC superconductor Ag/YBCO reinforced by adding Zr has been synthesized by sintering a compressed mixture of ZrxYBa2Cu3O7-δ(0≤x≤1.0) and Ag powders at various ratios. The flexural strength in the Ag/ZYBCO reached its maximum value of 280 MPa at the composition x{=}0.8 and 33 vol.%Ag, being more than 5 times as large as that in the sintered YBCO. In addition, the presence of Ag can endow the plasticity while maintaining the superconducting transition temperature above about 80 K. Both the flexural strength and the Vickers hardness are enhanced in magnitude comparable to those for commercial alumina and magnesia. The enhanced mechanical strength is attributed to the unique microstructure, in which dispersed Ag particles remain intact with the Zr-bearing YBCO matrix, whereas CuO and BaZrO3 precipitates in the 123-phase matrix act to reinforce the ceramic without disrupting the superconducting channel.

  1. Mechanical and superconducting properties of Ag/YBCO composite superconductors reinforced by the addition of Zr

    NASA Astrophysics Data System (ADS)

    Tetsuo, Oka; Itoh, Yoshitaka; Ogasawa, Fumihiko; Mizutam, Uichiro; Suganuma, Motohiro

    1990-10-01

    The composite high Tc superconductors Ag/YBCO reinforced by adding Zr has been synthesized by sintering a compressed mixture of Zr(x)YBa2Cu3O(7-delta) (x = 0-1.0) and Ag powders at various ratios. The flexural strength in the Ag/ZYBCO reached its maximum value of 280 MPa at the composition x = 0.8 and 33 vol. pct Ag, being more than 5 times as large as that in the sintered YBCO. In addition, the presence of Ag can endow the plasticity while maintaining the superconducting transition temperature above about 80 K. Both the flexural strength and the Vickers hardness are enhanced in magnitude comparable to those for commerical alumina and magnesia. The enhanced mechanical strength is attributed to the unique microstructure, in which dispersed Ag particles remain intact with the Zr-bearing YBCO matrix, whereas CuO and BaZrO3 precipitates in the 123-phase matrix act to reinforce the ceramic without disrupting the superconducting channel.

  2. Superconductivity, structure visualization, mechanical strength promotion and Raman spectra of hafnium-doped-123-YBCO synthesized via urea precursor route

    NASA Astrophysics Data System (ADS)

    Elsabawy, Khaled M.

    2011-08-01

    The pure YBCO (YBa2Cu3O7) and its variant hafnium containing superconductors with general formula: Y1-xHfxBa2Cu3Oz, where x = 0.1, 0.2, and 0.4 mole, respectively, were synthesized by solution route using urea as precursor forming agent. X-ray measurements indicated that Hf4+ ions have a negligible effect on the main crystalline structure and substitute Y-sites successfully in lattice structure of 123-YBCO at low levels of hafnium doping (x = 0.1 → 0.2 mole). From SE-microscopy mapping and EDX elemental analysis Hf4+ was detected qualitatively with good approximation to the actual molar ratio but not observed at 123-YBCO grain boundaries which confirm that hafnium (IV) has diffused regularly into material bulk of superconducting 123-YBCO-phase at low levels of concentrations. Structure visualization of Hf-doped-123-YBCO was made to confirm success of hafnium substitutions inside crystal lattice on Y-sites of 123-YBCO superconductors. Hafnium dopings affected sharply on the main vibrating modes of YBCO regime particularly on the apical oxygen (O4) vibrational mode A1g. Magnetic susceptibility measurements proved that hafnium dopings have strong effect on the transport properties of YBCO-composites regime. Hafnium promotes mechanical tensile coefficient recording maxima 35.7 MPa for x = 0.4 mole.

  3. Nano-engineered pinning centres in YBCO superconducting films

    NASA Astrophysics Data System (ADS)

    Crisan, A.; Dang, V. S.; Mikheenko, P.

    2017-02-01

    For practical applications of superconducting materials in applied magnetic fields, artificial pinning centres in addition to natural ones are required to oppose the Lorentz force. These pinning centres are actually various types of defects in the superconductor matrix. The pinning centres can be categorised on their dimension (volume, surface or point) and on their character (normal cores or Δκ cores). Different samples have been produced by Pulsed Laser Deposition, with various thicknesses, temperatures and nanostructured additions to the superconducting matrix. They have been characterized by SQUID Magnetic Properties Measurement System and Physical Properties Measurement System, as well as by Transmission Electron Microscopy (TEM). Correlations between pinning architecture, TEM images, and critical currents at various fields and field orientations will be shown for a large number of YBa2Cu3Ox films with various types and architectures of artificial pinning centres.

  4. Competition between charge and superconducting orders in underdoped YBCO

    NASA Astrophysics Data System (ADS)

    Julien, Marc-Henri

    2012-02-01

    We report nuclear magnetic resonance measurements (NMR) showing that high magnetic fields induce a static, unidirectional, modulation of the charge density in the CuO2 planes of underdoped YBa2Cu3Oy [T. Wu et al., Nature 477, 191 (2011)]. The appearance of the charge order coincides with the Fermi surface reconstruction inferred from quantum oscillation and other transport measurements. This charge order appears to be most probably the same 4a-periodic stripe modulation as in La-214 cuprates. That it develops only when superconductivity fades away (no charge order is observed under strong fields parallel to the planes) and near the same 1/8 hole doping as in La-214 suggests that charge order, although visibly pinned by CuO chains in YBa2Cu3Oy, is an intrinsic propensity of the superconducting planes of high-Tc copper oxides. Since field induced stripe order is also compatible with neutron scattering data in La-214 and with STM data in Bi-2212, charge order could be a generic competitor of high Tc superconductivity. [4pt] Work performed with T. Wu, H. Mayaffre, S. Kr"amer, M. Horvatic, C. Berthier (LNCMI Grenoble), W.N. Hardy, R. Liang, D.A. Bonn (University of British Columbia, Vancouver)

  5. Migrating from superconducting to semiconducting YBCO thin film bolometers as future far-infrared imaging pixels

    NASA Astrophysics Data System (ADS)

    Jagtap, Vishal S.; Longhin, Mattia; Kulsreshath, Mukesh K.; Kreisler, Alain J.; Dégardin, Annick F.

    2010-04-01

    YBa2Cu3O6+x compounds are well known to exhibit superconducting properties for x > 0.5 and semiconducting properties for lower oxygen content. Superconducting YBCO was obtained commercially; the semiconducting material was deposited by sputtering at room temperature. In order to migrate from superconducting to uncooled semiconducting far-infrared bolometer technologies, we have first realized and compared the performance of 2 × 2 pixel arrays made from both materials deposited on MgO substrates. Pixels were in the shape of meanders, embedded in an area of about 1 mm2. Pixel detectivity and thermal crosstalk were studied in the 1 Hz to 100 kHz modulation frequency range by using a 850 nm solid state laser. Secondly we have improved the geometry of semiconducting YBCO bolometers fabricated on silicon substrates, in order to match their impedance with the impedance of the antenna required for working in the THz range. First optical results are also presented, where both regular bolometric and pyroelectric responses are exhibited.

  6. System innovations for aerosol MOCVD of YBCO superconducting thin films

    NASA Astrophysics Data System (ADS)

    Nelms, David Martin

    System innovations were developed for metallo-organic chemical vapor deposition (MOCVD) in order to achieve two main objectives: to fully characterize a novel feed system while and to demonstrate uniform, superconducting thin films over a 2 inch diameter. The novel aerosol feed system was fully characterized and improved by performing solubility and carbon tests with different metallo-organic solvents and by thermally mapping the heating section. The gas flow profiles in the reactor chamber were modeled with a finite-element software package called Fluent. This enabled us to study different nozzles for improving the uniformity of the velocity near the substrate and the uniformity of the depositions. Depositions were then performed to test the validity of the computer model and to determine correct molar feed ratios. The uniformity was measured with a scanning electron microscope (SEM) while the film compositions were analyzed with a X-Ray photoelectron spectroscopy system (XPS). Once the correct feed compositions were determined, this ratio was used along with the feed nozzle designed to deposit uniform, superconducting thin films.

  7. Fabrication process and noise properties of antenna-coupled microbolometers based on superconducting YBCO films

    NASA Astrophysics Data System (ADS)

    Karmanenko, S. F.; Semenov, A. A.; Khrebtov, I. A.; Leonov, V. N.; Johansen, T. H.; Galperin, Yu M.; Bobyl, A. V.; Dedoboretz, A. I.; Gaevski, M. E.; Lunev, A. V.; Suris, R. A.

    2000-03-01

    An analysis of how the detectivity and lifetime depend on the fabrication process of superconducting antenna-coupled microbolometers has been carried out. The temperature dependences of responsivity and noise equivalent power (NEP) have been estimated in terms of the thermal model. To reveal the main degradation mechanism, 1/f -noise characterization has been used. Monte-Carlo simulation of the annealing procedure of YBa2 Cu3 O7 (YBCO) films for the operating ranges of frequency and temperature has shown that prevailing sources of flicker noise in superconducting microstrips are associated with transitions of oxygen atoms situated close to low-angle boundaries of the film blocks. The magnetron sputtering technique has been optimized to reduce the Hooge parameter for flicker noise to a record-breaking low value for YBCO films of about 10-4 at 93 K. Comparative analysis of chemical, ion and laser etching techniques by low-temperature scanning electron microscopy and magneto-optics allowed the fabrication of microstrips with uniform current distribution characterized by critical current density higher than 106 A cm-2 at 77 K and long-time stability. The process of low-energy ion milling of YBCO films with an Ar+ beam generated in a duopigatron ion source was used to reach a width resolution at the topology edge better than 0.2 µm. The antenna-coupled bolometers fabricated from the superconducting microstrips were used to register microwave radiation at a frequency of 70.3 GHz and temperature of 93 K. It is demonstrated that the developed technology makes possible the fabrication of long-lived YBCO-based antenna microbolometers with electrical NEPe = 1.5 × 10-12 W Hz-1/2 . The calculated response time of the antenna is about 30-150 ns. Further development is associated with fabrication of coupling microbolometers with immersed lens, with predicted optical detectivity D * = (4 × 109 - 4 × 1010 ) cm Hz1/2 W-1 in the wavelength range 100-1000 µm.

  8. An AFM study of the morphology and local mechanical properties of superconducting YBCO thin films

    NASA Astrophysics Data System (ADS)

    Soifer, Ya. M.; Verdyan, A.; Azoulay, J.; Kazakevich, M.; Rabkin, E.

    2004-02-01

    The morphology of thin superconducting YBCO films deposited on sapphire and on SrTiO 3 was studied with the help of atomic force and scanning electron microscopies. The intrinsic mechanical properties in the flat, particles-free and chemically homogeneous regions of the films were determined with the aid of nanoindenting atomic force microscope. Also the microscopy studies revealed the difference in topography of the films, the nanohardness and Young’s modulus of two films were very close to each other. For the indents shallower than 0.2 of the film thickness the Young’s modulus and hardness of the films on two different substrates converged to the values of 210 and 8.5 GPa, respectively. The possible deformation mechanisms determining the localized deformation of intrinsically brittle ceramic films are discussed.

  9. Detectors of Infrared Radiation Based on High T(c) Superconducting YBCO Films

    DTIC Science & Technology

    1991-06-01

    d4 . mvuAT.OATS 3. AIPOST ’l ’ TE ’OEE FINAL REPORT 1 Dec 87-30 Apr 90 Detectors of Infrared Radiation Based on High T(c) Superconducting YBCO Films...YBa2CU3O7 film on LaAlO3 at 6.8 K biased with 20.6 mA. > .11 --- . I’ M e nsq FW m.. E\\pe of th .5.i.=nl 3(0wnN n UA*. ). l=btototpte vCV ra. dt mdm lenmo ,5,25 ind 9W nj/pu- 4=5mAT=8s’

  10. Anisotropic superconductivity driven by kinematic interaction

    NASA Astrophysics Data System (ADS)

    Ivanov, V. A.

    2000-11-01

    We have analysed the effect of kinematic pairing on the symmetry of superconducting order parameter for a square lattice in the frame of the strongly correlated Hubbard model. It is argued that in the first perturbation order the kinematic interaction renormalizes the Hubbard-I dispersions and provides at low doping the mixed singlet (s + s*)-wave superconductivity, giving way at higher doping to the triplet p-wave superconductivity. The obtained phase diagram depends only on the hopping integral parameter. The influence of the Coulomb repulsion on the kinematic superconducting pairing has been estimated. The (s + s*)-wave gap and the thermodynamic critical magnetic field have been derived.

  11. Superconducting YBCO thin film on multicrystalline Ag film evaporated on MgO substrate

    NASA Astrophysics Data System (ADS)

    Azoulay, Jacob; Verdyan, Armen; Lapsker, Igor

    Superconducting YBa 2Cu 3O 7-δ films were grown by resistive evaporation on multicrystalline silver film which was evaporated on MgO substrate. A simple inexpensive vacuum system equipped with resistively heated boat was used for the whole process. Silver film was first evaporated on MgO substrate kept at 400°C during the evaporation after which with no further annealing a precursor mixture of yttrium small grains and Cu and BaF2 in powder form weighed in the atomic proportion to yield stoichiometric YBa 2Cu 3O 7 was evaporated. The films thus obtained were annealed at 740°C under low oxygen partial pressure of about 1Pa for 30 minutes to form the superconducting phase. X-ray diffraction and scanning electron microscopy techniques were used for texture and surface analysis. Electrical properties were determined using a standard dc four-probe for electrical measurements. The physical and electrical properties of the YBCO films are discussed in light of the fact that X-ray diffraction measurements done on the silver film have revealed a multicrystalline structure

  12. Ideal charge-density-wave order in the high-field state of superconducting YBCO

    PubMed Central

    Jang, H.; Lee, W.-S.; Nojiri, H.; Matsuzawa, S.; Yasumura, H.; Nie, L.; Maharaj, A. V.; Gerber, S.; Liu, Y.-J.; Mehta, A.; Bonn, D. A.; Liang, R.; Hardy, W. N.; Burns, C. A.; Islam, Z.; Song, S.; Hastings, J.; Devereaux, T. P.; Shen, Z.-X.; Kivelson, S. A.; Kao, C.-C.; Zhu, D.; Lee, J.-S.

    2016-01-01

    The existence of charge-density-wave (CDW) correlations in cuprate superconductors has now been established. However, the nature of the CDW ground state has remained uncertain because disorder and the presence of superconductivity typically limit the CDW correlation lengths to only a dozen unit cells or less. Here we explore the field-induced 3D CDW correlations in extremely pure detwinned crystals of YBa2Cu3O2 (YBCO) ortho-II and ortho-VIII at magnetic fields in excess of the resistive upper critical field (Hc2) where superconductivity is heavily suppressed. We observe that the 3D CDW is unidirectional and possesses a long in-plane correlation length as well as significant correlations between neighboring CuO2 planes. It is significant that we observe only a single sharply defined transition at a critical field proportional to Hc2, given that the field range used in this investigation overlaps with other high-field experiments including quantum oscillation measurements. The correlation volume is at least two to three orders of magnitude larger than that of the zero-field CDW. This is by far the largest CDW correlation volume observed in any cuprate crystal and so is presumably representative of the high-field ground state of an “ideal” disorder-free cuprate. PMID:27930313

  13. Ideal charge-density-wave order in the high-field state of superconducting YBCO.

    PubMed

    Jang, H; Lee, W-S; Nojiri, H; Matsuzawa, S; Yasumura, H; Nie, L; Maharaj, A V; Gerber, S; Liu, Y-J; Mehta, A; Bonn, D A; Liang, R; Hardy, W N; Burns, C A; Islam, Z; Song, S; Hastings, J; Devereaux, T P; Shen, Z-X; Kivelson, S A; Kao, C-C; Zhu, D; Lee, J-S

    2016-12-20

    The existence of charge-density-wave (CDW) correlations in cuprate superconductors has now been established. However, the nature of the CDW ground state has remained uncertain because disorder and the presence of superconductivity typically limit the CDW correlation lengths to only a dozen unit cells or less. Here we explore the field-induced 3D CDW correlations in extremely pure detwinned crystals of YBa2Cu3O2 (YBCO) ortho-II and ortho-VIII at magnetic fields in excess of the resistive upper critical field ([Formula: see text]) where superconductivity is heavily suppressed. We observe that the 3D CDW is unidirectional and possesses a long in-plane correlation length as well as significant correlations between neighboring CuO2 planes. It is significant that we observe only a single sharply defined transition at a critical field proportional to [Formula: see text], given that the field range used in this investigation overlaps with other high-field experiments including quantum oscillation measurements. The correlation volume is at least two to three orders of magnitude larger than that of the zero-field CDW. This is by far the largest CDW correlation volume observed in any cuprate crystal and so is presumably representative of the high-field ground state of an "ideal" disorder-free cuprate.

  14. Ideal charge-density-wave order in the high-field state of superconducting YBCO

    DOE PAGES

    Jang, H.; Lee, W. -S.; Nojiri, H.; ...

    2016-12-05

    Here, the existence of charge-density-wave (CDW) correlations in cuprate superconductors has now been established. However, the nature of the CDW ground state has remained uncertain because disorder and the presence of superconductivity typically limit the CDW correlation lengths to only a dozen unit cells or less. Here we explore the field-induced 3D CDW correlations in extremely pure detwinned crystals of YBa2Cu3O2 (YBCO) ortho-II and ortho-VIII at magnetic fields in excess of the resistive upper critical field (Hc2) where superconductivity is heavily suppressed. We observe that the 3D CDW is unidirectional and possesses a long in-plane correlation length as well asmore » significant correlations between neighboring CuO2 planes. It is significant that we observe only a single sharply defined transition at a critical field proportional to Hc2, given that the field range used in this investigation overlaps with other high-field experiments including quantum oscillation measurements. The correlation volume is at least two to three orders of magnitude larger than that of the zero-field CDW. This is by far the largest CDW correlation volume observed in any cuprate crystal and so is presumably representative of the high-field ground state of an “ideal” disorder-free cuprate.« less

  15. Ideal charge-density-wave order in the high-field state of superconducting YBCO

    SciTech Connect

    Jang, H.; Lee, W. -S.; Nojiri, H.; Matsuzawa, S.; Yasumura, H.; Nie, L.; Maharaj, A. V.; Gerber, S.; Liu, Y. -J.; Mehta, A.; Bonn, D. A.; Liang, R.; Hardy, W. N.; Burns, C. A.; Islam, Z.; Song, S.; Hastings, J.; Devereaux, T. P.; Shen, Z. -X.; Kivelson, S. A.; Kao, C. -C.; Zhu, D.; Lee, J. -S.

    2016-12-05

    Here, the existence of charge-density-wave (CDW) correlations in cuprate superconductors has now been established. However, the nature of the CDW ground state has remained uncertain because disorder and the presence of superconductivity typically limit the CDW correlation lengths to only a dozen unit cells or less. Here we explore the field-induced 3D CDW correlations in extremely pure detwinned crystals of YBa2Cu3O2 (YBCO) ortho-II and ortho-VIII at magnetic fields in excess of the resistive upper critical field (Hc2) where superconductivity is heavily suppressed. We observe that the 3D CDW is unidirectional and possesses a long in-plane correlation length as well as significant correlations between neighboring CuO2 planes. It is significant that we observe only a single sharply defined transition at a critical field proportional to Hc2, given that the field range used in this investigation overlaps with other high-field experiments including quantum oscillation measurements. The correlation volume is at least two to three orders of magnitude larger than that of the zero-field CDW. This is by far the largest CDW correlation volume observed in any cuprate crystal and so is presumably representative of the high-field ground state of an “ideal” disorder-free cuprate.

  16. Ideal charge-density-wave order in the high-field state of superconducting YBCO

    DOE PAGES

    Jang, H.; Lee, W. -S.; Nojiri, H.; ...

    2016-12-05

    The existence of charge-density-wave (CDW) correlations in cuprate superconductors has now been established. However, the nature of the CDW ground state has remained uncertain because disorder and the presence of superconductivity typically limit the CDW correlation lengths to only a dozen unit cells or less. Here we explore the field-induced 3D CDW correlations in extremely pure detwinned crystals of YBa2Cu3O2 (YBCO) ortho-II and ortho-VIII at magnetic fields in excess of the resistive upper critical field (Hc2) where superconductivity is heavily suppressed. We observe that the 3D CDW is unidirectional and possesses a long in-plane correlation length as well as significantmore » correlations between neighboring CuO2 planes. It is significant that we observe only a single sharply defined transition at a critical field proportional to Hc2, given that the field range used in this investigation overlaps with other high-field experiments including quantum oscillation measurements. The correlation volume is at least two to three orders of magnitude larger than that of the zero-field CDW. Furthermore, this is by far the largest CDW correlation volume observed in any cuprate crystal and so is presumably representative of the high-field ground state of an “ideal” disorder-free cuprate.« less

  17. Anisotropic resonance modes emerging in an antiferromagnetic superconducting state.

    PubMed

    Waßer, F; Lee, C H; Kihou, K; Steffens, P; Schmalzl, K; Qureshi, N; Braden, M

    2017-09-04

    Two strong arguments in favor of magnetically driven unconventional superconductivity arise from the coexistence and closeness of superconducting and magnetically ordered phases on the one hand, and from the emergence of magnetic spin-resonance modes at the superconducting transition on the other hand. Combining these two arguments one may ask about the nature of superconducting spin-resonance modes occurring in an antiferromagnetic state. This problem can be studied in underdoped BaFe2 As2, for which the local coexistence of large moment antiferromagnetism and superconductivity is well established by local probes. However, polarized neutron scattering experiments are required to identify the nature of the resonance modes. In the normal state of Co underdoped BaFe2 As2 the antiferromagnetic order results in broad magnetic gaps opening in all three spin directions that are reminiscent of the magnetic response in the parent compound. In the superconducting state two distinct anisotropic resonance excitations emerge, but in contrast to numerous studies on optimum and over-doped BaFe2 As2 there is no isotropic resonance excitation. The two anisotropic resonance modes appearing within the antiferromagnetic phase are attributed to a band selective superconducting state, in which longitudinal magnetic excitations are gapped by antiferromagnetic order with sizable moment.

  18. Aspects of passive magnetic levitation based on high-T{sub c} superconducting YBCO thin films

    SciTech Connect

    Schoenhuber, P.; Moon, F.C.

    1995-04-01

    Passive magnetic levitation systems reported in the past were mostly confined to bulk superconducting materials. Here the authors present fundamental studies on magnetic levitation employing cylindrical permanent magnets floating above high-T{sub c} superconducting YBCO thin films (thickness about 0.3 mu m). Experiments included free floating rotating magnets as well as well-established flexible beam methods. By means of the latter, the authors investigated levitation and drag force hysteresis as well as magnetic stiffness properties of the superconductor-magnet arrangement. In the case of vertical motion of the magnet, characteristic high symmetry of repulsive (approaching) and attractive (withdrawing) branches of the pronounced force-displacement hysteresis could be detected. Achievable force levels were low as expected but sufficient for levitation of permanent magnets. With regard to magnetic stiffness, thin films proved to show stiffness-force ratios about one order of magnitude higher than bulk materials. Phenomenological models support the measurements. Regarding the magnetic hysteresis of the superconductor, the Irie-Yamafuji model was used for solving the equation of force balance in cylindrical coordinates allowing for a macroscopic description of the superconductor magnetization. This procedure provided good agreement with experimental levitation force and stiffness data during vertical motion. For the case of (lateral) drag force basic qualitative characteristics could be recovered, too. It is shown that models, based on simple asymmetric magnetization of the superconductor, describe well asymptotic transition of drag forces after the change of the magnet motion direction. Virgin curves (starting from equilibrium, i.e. symmetric magnetization) are approximated by a linear approach already reported in literature only. This paper shows that basic properties of superconducting thin films allow for their application to magnetic levitation.

  19. Aspects of passive magnetic levitation based on high-T(sub c) superconducting YBCO thin films

    NASA Technical Reports Server (NTRS)

    Schoenhuber, P.; Moon, F. C.

    1995-01-01

    Passive magnetic levitation systems reported in the past were mostly confined to bulk superconducting materials. Here we present fundamental studies on magnetic levitation employing cylindrical permanent magnets floating above high-T(sub c) superconducting YBCO thin films (thickness about 0.3 mu m). Experiments included free floating rotating magnets as well as well-established flexible beam methods. By means of the latter, we investigated levitation and drag force hysteresis as well as magnetic stiffness properties of the superconductor-magnet arrangement. In the case of vertical motion of the magnet, characteristic high symmetry of repulsive (approaching) and attractive (withdrawing) branches of the pronounced force-displacement hysteresis could be detected. Achievable force levels were low as expected but sufficient for levitation of permanent magnets. With regard to magnetic stiffness, thin films proved to show stiffness-force ratios about one order of magnitude higher than bulk materials. Phenomenological models support the measurements. Regarding the magnetic hysteresis of the superconductor, the Irie-Yamafuji model was used for solving the equation of force balance in cylindrical coordinates allowing for a macroscopic description of the superconductor magnetization. This procedure provided good agreement with experimental levitation force and stiffness data during vertical motion. For the case of (lateral) drag force basic qualitative characteristics could be recovered, too. It is shown that models, based on simple asymmetric magnetization of the superconductor, describe well asymptotic transition of drag forces after the change of the magnet motion direction. Virgin curves (starting from equilibrium, i.e. symmetric magnetization) are approximated by a linear approach already reported in literature only. This paper shows that basic properties of superconducting thin films allow for their application to magnetic levitation or - without need of levitation

  20. Manufacture of YBCO Superconducting Flexible Tapes from Nanoparticle Films Derived from Sedimentation and by Flame Deposition of Nanoparticles from Solution

    SciTech Connect

    Wiesmann, Harold

    2008-02-24

    The objective of this CRADA was to develop the experimental and theoretical basis of a technology to produce yttrium barium copper oxide (YBCO) superconducting flexible tapes derived from nanoparticle metal oxide sols. The CRADA was a joint effort between Oxford Superconducting Technology, Brookhaven National Laboratory and Karpov Institute of Physical Chemistry. The effort was divided into three main tasks, the synthesis of a heteroepitaxial oxide buffer layer, and the manufacture of a flexible biaxially textured metallic substrate and the synthesis of a heteroepitaxial crystalline YBCO layer. The formation of a heteroepitaxial buffer layer was implemented using technology developed at the Karpov Institute of Physical Chemistry for the synthesis, stabilization and deposition of polymer stabilized nanoparticle metal oxide sols. Using this technology, flexible oriented RABiTS nickel tapes, manufactured and supplied by the CRADA partner, Oxford Superconducting Technology, Carteret, New Jersey, were coated with a film of metal oxide nanoparticles. After coating the RABiTS nickel tapes with the nanoparticle sols the nickel tape/nanoparticle composite structure was sintered in order to form a dense crystalline heteroepitaxial oxide layer on the surface of the tape, also known as a ‘buffer’ layer. The final phase of the research was the formation of a heteroepitaxial YBCO layer, grown on top of the metal oxide buffer layer. This work was scheduled to follow the development of the heteroepitaxial oxide buffer layer as described above. Three different polymer stabilized sols, yttrium hydroxide, Y(OH){sub 3}, copper hydroxide, Cu(OH){sub 2}, and barium fluoride, BaF{sub 2}, were synthesized and combined in the appropriate stoichiometric ratio. This metal oxide sol was then be deposited onto the buffer layer and reacted to form a crystalline heteroepitaxial YBCO film ranging from 1–5 microns thick.

  1. Ideal charge-density-wave order in the high-field state of superconducting YBCO

    NASA Astrophysics Data System (ADS)

    Jang, H.; Lee, W.-S.; Nojiri, H.; Matsuzawa, S.; Yasumura, H.; Nie, L.; Maharaj, A. V.; Gerber, S.; Liu, Y.-J.; Mehta, A.; Bonn, D. A.; Liang, R.; Hardy, W. N.; Burns, C. A.; Islam, Z.; Song, S.; Hastings, J.; Devereaux, T. P.; Shen, Z.-X.; Kivelson, S. A.; Kao, C.-C.; Zhu, D.; Lee, J.-S.

    2016-12-01

    The existence of charge-density-wave (CDW) correlations in cuprate superconductors has now been established. However, the nature of the CDW ground state has remained uncertain because disorder and the presence of superconductivity typically limit the CDW correlation lengths to only a dozen unit cells or less. Here we explore the field-induced 3D CDW correlations in extremely pure detwinned crystals of YBa2Cu3O2 (YBCO) ortho-II and ortho-VIII at magnetic fields in excess of the resistive upper critical field (Hc2Hc2) where superconductivity is heavily suppressed. We observe that the 3D CDW is unidirectional and possesses a long in-plane correlation length as well as significant correlations between neighboring CuO2 planes. It is significant that we observe only a single sharply defined transition at a critical field proportional to Hc2Hc2, given that the field range used in this investigation overlaps with other high-field experiments including quantum oscillation measurements. The correlation volume is at least two to three orders of magnitude larger than that of the zero-field CDW. This is by far the largest CDW correlation volume observed in any cuprate crystal and so is presumably representative of the high-field ground state of an “ideal” disorder-free cuprate.

  2. In Situ deposition of YBCO high-T(sub c) superconducting thin films by MOCVD and PE-MOCVD

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

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

  4. Anisotropic thermomagnetic avalanche activity in field-cooled superconducting films

    NASA Astrophysics Data System (ADS)

    Colauto, F.; Carmo, D.; de Andrade, A. M. H.; Oliveira, A. A. M.; Ortiz, W. A.; Johansen, T. H.

    2017-08-01

    The electrodynamic behavior of isotropic superconducting Nb films cooled below their critical temperature in the presence of in-plane applied magnetic fields is investigated using magneto-optical imaging. A specially designed local flux injector is used to show that the frozen-in in-plane vortices strongly guide and enhance the penetration of perpendicular vortices, whereas their penetration across the array of in-plane vortices is essentially unchanged. This result provides the key to understanding why field-cooled square superconducting films show anisotropic nucleation of flux avalanches (jumps) along the four edges. The explanation is based on an analytical model for thermomagnetic avalanche nucleation in type-II superconducting films, and allows one to understand the entire scenario of different flux dynamics observed experimentally.

  5. Anisotropic criteria for the type of superconductivity

    SciTech Connect

    Kogan, Vladimir G; Prozorov, Ruslan

    2014-08-01

    The classical criterion for classification of superconductors as type I or type II based on the isotropic Ginzburg-Landau theory is generalized to arbitrary temperatures for materials with anisotropic Fermi surfaces and order parameters. We argue that the relevant quantity for this classification is the ratio of the upper and thermodynamic critical fields Hc2/Hc, rather than the traditional ratio of the penetration depth and the coherence length λ/ξ. Even in the isotropic case, Hc2/Hc coincides with 2√λ/ξ only at the critical temperature Tc and they differ as T decreases, the long-known fact. Anisotropies of Fermi surfaces and order parameters may amplify this difference and render false the criterion based on the value of κ=λ/ξ.

  6. Fluctuation effects and anomalous diamagnetism in YBCO124 and in underdoped YBCO123 from susceptibility and {sup 63}Cu nuclear relaxation

    SciTech Connect

    Carretta, P.; Lascialfari, A.; Rigamonti, A.; Rosso, A.; Varlamov, A.A.

    1999-04-20

    The effects of superconducting fluctuations on the diamagnetic susceptibility and on the dynamical spin susceptibility involved in {sup 63}Cu NMR-NQR relaxation rate are investigated in oriented powders of underdoped YBCO123 and YBCO124 and compared with the ones in optimally doped YBC0123. While in this latter compound the fluctuation diamagnetism is well described by an anisotropic Ginzburg-Landau (GL) functional, in underdoped YBCO123 an anomalous diamagnetism is observed, with a strong enhancement of the susceptibility, in a wide temperature range. The magnetization curves cannot be described by any GL anisotropic functional. Also in YBCO124 the fluctuation diamagnetism is hard to describe by GL-type approach, although the enhancement is not as marked as in underdoped YBCO123. In YBCO124, and in underdoped YBCO123, the temperature and field dependences of the {sup 63}Cu relaxation rates W appear different from the ones in optimally doped YBCO123. No field-induced decrease of W is observed, as it is expected in the case of a changeover from a to d of the orbital symmetry of the fluctuating pairs or when the character of the fluctuations is different from the GL one.

  7. Systematic Modification of Electrical and Superconducting Properties of YBCO and Nano-Patterning of High-Tc Superconducting Thin Films by Light-Ion Irradiation

    NASA Astrophysics Data System (ADS)

    Pedarnig, J. D.; Bodea, M. A.; Steiger, B.; Markowitsch, W.; Lang, W.

    Irradiation of high-temperature superconducting (HTS) YBa2Cu3O7-d (YBCO) thin films with 75 keV He+ ions leads to a quasi-exponential increase of the in-plane (ρab) and the out-of-plane (ρc) resistivity in the normal state and to a non-linear decrease of the critical temperature Tc with ion dose. In situ electrical measurements at room temperature reveal an irradiation-induced reduction of resistivity anisotropy ρc/ρab and a slight relaxation of film resistivity after the ion irradiation is stopped. Ex situ measurements show a stretched-exponential relaxation of Tc and normal state resistivity that continues for several weeks after the ion irradiation. Irradiation of YBCO thin films by low-energy He+ ions through stencil masks results in local modification of the electrical and superconducting properties of the HTS material. We demonstrate that masked ion-beam lithography enables to produce structures smaller than 100 nm in size that have potential for applications in future superconducting nano-electronics.

  8. Microwave and transport studies of superconducting films of YBCO and fullerenes. Final technical report, 15 February 1993-31 August 1996

    SciTech Connect

    Dresselhaus, M.S.; Dresselhaus, G.

    1996-08-31

    During the 1995-96 year of the research program on `Microwave and Transport Studies of Superconducting Films of YBCO and Fullerenes,` the effort was focused on several projects. The main highlight was a collaborative study of the nonlinear microwave properties of superconducting YBa2Cu3O(7-x) (YBCO) which was carried out with researchers at Rome Labs and the MIT Lincoln Laboratory. During this year Nathan Belk completed his Ph.D. thesis entitled `Electronic Transport and Magnetic Properties of Disordered High-Tc Materials.` Joe Habib made significant progress with his study of microwave losses in individual Josephson junctions. A new graduate student, Chris Lehner, who is an Army Captain, joined the group on assignment from the US Army, and is working on the modeling of microwave losses in superconducting circuits. Continued progress was made with the use of femtosecond optics to study superconductivity and the associated phenomena in alkali metal doped C60 materials.

  9. Detectors of Infrared Radiation Based on High T(c) Superconducting YBCO Films

    DTIC Science & Technology

    1988-02-23

    of the YBCO films. Second, the best (epitaxial) super- conducting YBCO films are grown on the SrTiO3 substrates, which may be disadvantageous for...sintered pellets, thin films, single crystals and fibers. We have grown thin BCSCO films on SrTiO3 substrates( 3 ); they showed zero resistance at Tc...is a "line" .., compound - i.e. it forms at nearly exact stoichiometry composition. As it grows epitaxially on the (001) face of SrTiO3 substrate, it

  10. Dependence of the structural, electrical and magnetic properties of the superconductive YBCO thin films on the deposition rate

    NASA Astrophysics Data System (ADS)

    Karci, A. B.; Tepe, M.; Sozeri, H.

    2009-03-01

    In this study, YBCO thin films on single crystal LaAlO3 (100) substrates have been grown using DC inverted cylindrical magnetron sputtering technique and the effect of the deposition rate on these films is investigated. Three different deposition rates are used to produce superconducting YBCO thin films with 150 nm of thickness on (100) LaAlO3 single crystal substrate at 780 0C. The samples are analyzed in detail by means of XRD, R-T, χ-T, M-H and AFM characterizations and also the critical current densities (Jc) are derived from the magnetic hysteresis curves using the modified Bean formula [1]. The critical current density at 50 K was found to be in the range of 3.107 A/m2 to 8. 107 A/m2 with a deposition rate between 2nm/min and 1.2nm/min. A correlation has been obtained so that as the film deposition rate increases, the surface smoothness and crystalline quality of the films significantly deteriorate, resulting in a significant decrease in Jc.

  11. A flux pumping method applied to the magnetization of YBCO superconducting coils: frequency, amplitude and waveform characteristics

    NASA Astrophysics Data System (ADS)

    Fu, Lin; Matsuda, Koichi; Lecrevisse, Thibault; Iwasa, Yukikazu; Coombs, Tim

    2016-04-01

    This letter presents a flux pumping method and the results gained when it was used to magnetize a range of different YBCO coils. The pumping device consists of an iron magnetic circuit with eight copper coils which apply a traveling magnetic field to the superconductor. The copper poles are arranged vertically with an air gap length of 1 mm and the iron cores are made of laminated electric steel plates to minimize eddy-current losses. We have used this arrangement to investigate the best possible pumping result when parameters such as frequency, amplitude and waveform are varied. We have successfully pumped current into the superconducting coil up to a value of 90% of I c and achieved a resultant magnetic field of 1.5 T.

  12. 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.

  13. An advanced low-fluorine solution route for fabrication of high-performance YBCO superconducting films

    NASA Astrophysics Data System (ADS)

    Chen, Yuanqing; Wu, Chuanbao; Zhao, Gaoyang; You, Caiyin

    2012-06-01

    We have developed a new low-fluorine solution consisting of non-fluorine (F-free) barium and copper salts, and fluorine-containing yttrium trifluoroacetate. Using this new low-fluorine solution, the BaCO3 phase was avoided in the pyrolyzed precursor films. Instead, CuO, Y and Ba fluorides (YF3 and BaF2) were formed in the precursor films pyrolyzed at 450 °C, which was the same as when an All-TFA solution (prepared using Y, Ba, Cu trifluoroacetates as precursors) or other fluorine-reduced solutions were used. This new kind of low-fluorine solution has only 23% of the fluorine content in an All-TFA solution, and the fluorine content was lower than any other fluorine-reduced solution. Thus, rapid production of YBa2Cu3O7-x (YBCO) films can be easily realized. Using a heating rate of 10 °C min-1 in the pyrolysis process, a high critical current density (Jc) of 5 MA cm-2 (at 77 K, 0 T) was obtained in YBCO films fabricated on LaAlO3 (LAO) single crystal substrates from the new starting solution.

  14. Anisotropic effect of appearing superconductivity on the electron transport in FeSe

    NASA Astrophysics Data System (ADS)

    Grigoriev, P. D.; Sinchenko, A. A.; Kesharpu, K. K.; Shakin, A.; Mogilyuk, T. I.; Orlov, A. P.; Frolov, A. V.; Lyubshin, D. S.; Chareev, D. A.; Volkova, O. S.; Vasiliev, A. N.

    2017-06-01

    A theoretical model has been proposed to describe the conductivity of a layered anisotropic normal metal containing small superconducting inclusions at an arbitrary eccentricity of spheroidal superconducting islands. The electron transport and magnetic properties of FeSe single crystals have been measured. The results indicate the existence of superconductivity at temperatures much higher than the critical superconducting transition temperature corresponding to vanishing electrical resistance. Within the proposed model, quantitative agreement has been achieved between the volume fraction of superconducting inclusions and its temperature dependence determined from the transport and magnetic measurements.

  15. S-wave superconductivity in anisotropic holographic insulators

    NASA Astrophysics Data System (ADS)

    Erdmenger, Johanna; Herwerth, Benedikt; Klug, Steffen; Meyer, René; Schalm, Koenraad

    2015-05-01

    Within gauge/gravity duality, we consider finite density systems in a helical lattice dual to asymptotically anti-de Sitter space-times with Bianchi VII symmetry. These systems can become an anisotropic insulator in one direction while retaining metallic be- havior in others. To this model, we add a U(1) charged scalar and show that below a critical temperature, it forms a spatially homogeneous condensate that restores isotropy in a new superconducting ground state. We determine the phase diagram in terms of the helix parameters and perform a stability analysis on its IR fixed point corresponding to a finite density condensed phase at zero temperature. Moreover, by analyzing fluctuations about the gravity background, we study the optical conductivity. Due to the lattice, this model provides an example for a holographic insulator-superfluid transition in which there is no unrealistic delta-function peak in the normal phase DC conductivity. Our results suggest that in the zero temperature limit, all degrees of freedom present in the normal phase condense. This, together with the breaking of translation invariance, has implications for Homes' and Uemuras's relations. This is of relevance for applications to real world condensed matter systems. We find a range of parameters in this system where Homes' relation holds.

  16. Width Dependence of Tc for Photoinduced Superconducting Wires in Underdoped YBCO

    NASA Astrophysics Data System (ADS)

    Palmer, B. S.; Drew, H. D.; Mairov, B.; Osquiguil, E.; Hughes, R. A.; Preston, J. S.

    2003-03-01

    A near-field scanning optical microscope (NSOM) has been used to photogenerate superconducting wires in underdoped YBa_2Cu_3Ox (x ˜6.4) thin films ( ˜100 nm). After the wires are generated at room temperature, the sample is cooled to low temperatures where I-V measurements are performed. We have found that the superconducting transition temperature (T_c) is strongly suppressed for narrow wires (< 500 nm) compared with when the film is photogenerated with the same integrated photon density using far field light to generate a wide (10 μm) wire which produces an enhancement of the superconducting state with an increase in Tc of approximately 10K. We interpret these results in terms of the proximity effect between the superconducting and surrounding non-superconducting material that suppresses the superconducting transition temperature of the narrow wires. The experiment gives a measure of the characteristic length for the proximity effect, which is approximately 1 μm for the underdoped material.

  17. Determination of the symmetry of the superconducting pairing state and formation of a low-temperature normal metallic state in YBCO by electron irradiation

    SciTech Connect

    Giapintzakis, J.; Ginsberg, D.M.; Kirk, M.A.

    1995-10-01

    A key difference between a d-wave and an anisotropic s-wave superconductor is the expected effect of nonmagnetic point defects on T{sub c}. T{sub c} of the former becomes zero whereas T{sub c} of the latter attains a nonzero constant value beyond a critical concentration of impurities. We report the first observation that T{sub c} of an YBCO single crystal becomes zero after 4.1% of the planar oxygens O(2,3) are displaced by 400keV electron irradiation along the c-axis. Our data therefore indicate that YBCO is a d-wave superconductor. We also report evidence of a disorder-induced superconductor-to-normal-metal transition.

  18. Superconducting Generators for Airborne Applications and YBCO-Coated Conductors (Preprint)

    DTIC Science & Technology

    2008-10-01

    design was a homopolar inductor alternator (HIA) which locates the superconductor coil within the stator, thereby eliminating rotational loads on the...advantages over the BSCCO tape previous used in motor and generator demonstrations. The benefits of compact high- power superconducting machinery

  19. Field-Temperature Phase Diagram of Intergrain Ordering in Superconducting Ceramic YBCO

    NASA Astrophysics Data System (ADS)

    Deguchi, H.; Warabino, R.; Ka, S.; Mito, M.; Hagiwara, M.; Koyama, K.

    2017-07-01

    The ceramic YBa2Cu4O8 superconductor composed of submicron grains is considered a random Josephson-coupled network containing the so-called π junctions and shows successive phase transitions. With decreasing temperature, first the intragrain superconductive transition occurs inside each grain at T c1 and then the chiral-glass transition occurs among the grains at T c2 (< T c1). The third transition at T c3 (< T c2) is the intergrain superconducting transition. We measured the nonlinear susceptibility and resistivity of the ceramic YBa2Cu4O8 superconductor to determine the field dependences of the transition temperatures T c2 and T c3. The phase diagram of the intergrain ordering is discussed in light of the result predicted by Kawamura.

  20. Review of High Power Density Superconducting Generators: Present State and Prospects for Incorporating YBCO Windings

    DTIC Science & Technology

    2005-01-01

    efficient cryocoolers such as Stirling and Pulse Tube cryocoolers . Stirling cryocoolers have been used by the military for decades for sensor cool- ing...but these cryocoolers are too small for cooling the lar- ger volume associated with superconducting power applications. Large Stirling and Pulse Tube...Air Force contract for a laser application is a lightweight Stirling cryocooler weighing only 19 lbs and delivering 16 W of refrigeration at 80 K [39

  1. Ultra-Low Heat Leak YBCO Superconducting Leads for Cryoelectronic Applications

    DTIC Science & Technology

    2004-12-31

    reviewing instructions, searching existing data sources , gathering and maintaining the data needed, and completing and reviewing the collection of information...C and the powder then thoroughly mixed with ~ 60% (v/v) α- terpineol (Aldrich Chemical Co.). More terpineol was slowly added, with mixing, until...the superconducting strips. The whole device was then immersed into liquid N2 at 77 K. V-I data was obtained using a Yokogawa 7651 DC source , for

  2. Anisotropic superconducting gaps in YNi2B2C : A first-principles investigation

    NASA Astrophysics Data System (ADS)

    Kawamura, Mitsuaki; Akashi, Ryosuke; Tsuneyuki, Shinji

    2017-02-01

    We calculate superconducting gaps and quasiparticle density of states of YNi2B2C in the framework of the density functional theory for superconductors to investigate the origin of highly anisotropic superconducting gaps in this material. Calculated phonon frequencies, the quasiparticle density of states, and the transition temperature show good agreement with experimental results. From our calculation of superconducting gaps and orbital character analysis, we establish that the orbital character variation of the Fermi surface is the key factor of the anisotropic gap. Since the electronic states that consist of mainly Ni 3 d orbitals couple weakly with phonons, the superconducting gap function is suppressed for the corresponding states, which results in the anisotropy observed in the experiments. These results are hints to increase the transition temperature of materials in the borocarbide family.

  3. Measurement of AC Losses in a Racetrack Superconducting Coil Made from YBCO Coated Conductor

    NASA Astrophysics Data System (ADS)

    Seiler, Eugen; Abrahamsen, Asger B.; Kováč, Ján; Wichmann, Mike; Træholt, Chresten

    We present the results of transport measurements of AC losses in a racetrack shaped superconducting coil made from coated conductor tape. The outer dimensions of the coil are approximately 24 cm × 12 cm and it has 57 turns. The coil is impregnated with epoxy resin and fiberglass tape is used to insulate the individual turns and to improve the mechanical properties of the epoxy when exposed to thermal cycling. The coil is manufactured as a part of the field winding of a small synchronous generator; therefore stainless steel frames are installed on the inner and outer side of the winding to reinforce it. The AC loss is measured versus the transport current Ia with the coil immersed in liquid nitrogen. Measurements at frequencies 21 Hz, 36 Hz and 72 Hz are compared. The AC losses follow Ia2 dependence at low current amplitudes and Ia3 at high amplitudes. After cutting the inner steel frame the low amplitude losses are decreased, their frequency dependence is reduced but their dependence on the current remains unchanged.

  4. Anisotropic superconducting property studies of single crystal PbTaSe2

    NASA Astrophysics Data System (ADS)

    Sankar, Raman; Narsinga Rao, G.; Panneer Muthuselvam, I.; Chang, Tay-Rong; Jeng, H. T.; Senthil Murugan, G.; Lee, Wei-Li; Chou, F. C.

    2017-03-01

    The anisotropic superconducting properties of PbTaSe2 single crystal is reported. Superconductivity with T c  =  3.83  ±  0.02 K has been characterized fully with electrical resistivity ρ(T), magnetic susceptibility χ(T), and specific heat C p (T) measurements using single crystal samples. The superconductivity is type-II with lower critical field H c1 and upper critical field H c2 of 65 and 450 Oe (H⊥  to the ab-plane), 140 and 1500 Oe (H|| to the ab-plane), respectively. These results indicate that the superconductivity of PbTaSe2 is anisotropic. The superconducting anisotropy, electron-phonon coupling λ ep, superconducting energy gap Δ0, and the specific heat jump ΔC/γT c at T c confirms that PbTaSe2 can be categorized as a bulk superconductor.

  5. Anisotropic superconducting property studies of single crystal PbTaSe2.

    PubMed

    Sankar, Raman; Rao, G Narsinga; Muthuselvam, I Panneer; Chang, Tay-Rong; Jeng, H T; Murugan, G Senthil; Lee, Wei-Li; Chou, F C

    2017-03-08

    The anisotropic superconducting properties of PbTaSe2 single crystal is reported. Superconductivity with T c  =  3.83  ±  0.02 K has been characterized fully with electrical resistivity ρ(T), magnetic susceptibility χ(T), and specific heat C p (T) measurements using single crystal samples. The superconductivity is type-II with lower critical field H c1 and upper critical field H c2 of 65 and 450 Oe (H⊥  to the ab-plane), 140 and 1500 Oe (H|| to the ab-plane), respectively. These results indicate that the superconductivity of PbTaSe2 is anisotropic. The superconducting anisotropy, electron-phonon coupling λ ep, superconducting energy gap Δ0, and the specific heat jump ΔC/γT c at T c confirms that PbTaSe2 can be categorized as a bulk superconductor.

  6. Full-wave analysis of superconducting microstrip lines on anisotropic substrates using equivalent surface impedance approach

    SciTech Connect

    Lee, L.H.; Lyons, W.G.; Orlando, T.P.; Ali, S.M. . Dept. of Electrical Engineering and Computer Science); Lyons, W.G. . Lincoln Lab.); Withers, R.S. )

    1993-12-01

    A computationally efficient full-wave technique is developed to analyze single and coupled superconducting microstrip lines on anisotropic substrates. The optic axis of the dielectric is in the plane of the substrate at an arbitrary angle with respect to the propagation direction. A dyadic Green's function for layered, anisotropic media is used to formulate an integral equation for the current in the strips. To increase the efficiency of the method, the superconducting strips are replaced by equivalent surface impedances which account for the loss and kinetic inductance of the superconductors. The validity of this equivalent surface impedance (ESI) approach is verified by comparing the calculated complex propagation constant and characteristic impedance for superconducting microstrip lines on an isotropic substrate to measured results, and to numerical results by the more rigorous volume-integral equation method. The results calculated using the ESI approach for perfectly conducting coupled lines on an anisotropic substrate agree with the results by the finite-difference time-domain method. This efficient ESI technique is then used to study the effects of the optic axis orientation and the strip width on the characteristics of single and coupled superconducting microstrip lines on M-plane sapphire. The effects of the line separation and operating temperature on the coupled lines are also investigated.

  7. Roles of anisotropic and unequal gaps in the quasiparticle interference of superconducting iron pnictides

    NASA Astrophysics Data System (ADS)

    Singh, Dheeraj Kumar

    2017-09-01

    We investigate the role of gap characteristics such as anisotropy or inequality of the gaps in the quasiparticle interferences of iron pnictides using a five-orbital tight-binding model. We examine how the difference in the sensitivities exhibited by the sign-changing and -preserving s-wave superconductivity in an annular region around (π , 0), which can be used to determine the sign change of the superconducting gap, gets affected when the gaps are unequal on the electron and hole pockets. In addition, we also discuss how robust these differentiating features are on changing the quasiparticle energy or when the gap is anisotropic.

  8. Sign change of the vortex Hall effect in superconducting YBCO thin films with a square pattern of ion-irradiated defect columns

    NASA Astrophysics Data System (ADS)

    Zechner, G.; Haag, L. T.; Lang, W.; Dosmailov, M.; Bodea, M. A.; Pedarnig, J. D.

    2017-02-01

    The Hall effect in the mixed state of thin films of the high-temperature superconductor YBa2Cu3O7-δ (YBCO) that were patterned with a square array of regions with suppressed superconducting order parameter is investigated. Cylindrical defect columns penetrating the entire thin YBCO film along its crystallographic c - axis have been created by irradiation with He+ ions through a silicon stencil mask. Distinct peaks of the critical current at commensurate arrangements of magnetic flux quanta with the artificial defect lattice confirm enhanced vortex pinning. Vortex motion not only leads to a dissipative voltage along the current direction but also to a transverse voltage, termed vortex Hall effect. We report on the observation of a novel commensurability effect in the transverse Hall signal. A sign change and a positive peak of the Hall coefficient appear in a narrow magnetic field range around the matching field. The feature appears in the temperature range below the critical temperature, where the Hall effect usually is negative in underdoped and optimally-doped cuprate superconductors. The results indicate that the Hall matching effect originates from enhanced pinning of the vortices along the regular defect columns.

  9. PREFACE: Anisotropic and multiband pairing: from borides to multicomponent superconductivity Anisotropic and multiband pairing: from borides to multicomponent superconductivity

    NASA Astrophysics Data System (ADS)

    Annett, James; Kusmartsev, Feodor; Bianconi, Antonio

    2009-01-01

    In 2001, the discovery of superconductivity in MgB2 rapidly led to the understanding that its complex multi-sheeted Fermi surface had two distinct values of the gap parameter Δ, each with its own characteristic temperature dependence. While the theory of multigap superconductivity had been developed long ago, this was the first well studied example where multigap behaviour was observed clearly, and indeed is essential to understand the full superconducting properties of the material. Following this discovery, evidence for multigap behaviour has appeared in a number of materials, including cuprates, ruthenates, and most recently the iron pnictides. As well as multigap pairing on different Fermi-surface sheets, strong gap anisotropy in k-space and strong modulations of the gap in real space (e.g. stripes and phase separation models) are also important in cuprates. The aim of this special section is to present a selection of high-quality papers from experts in these diverse systems, showing the links and common physical issues arising from the existence of multi-component Cooper pairing. The papers collected together for the special section provide a snapshot of the current state of the understanding of multi-component superconductivity in a wide range of materials. In a model motivated by MgB2, Tanaka and Eschrig describe Abrikosov vortex lattice in a two-gap superconductor, examining how the vortex structure is modified by three-dimensionality or quasi two-dimensionality of the Fermi surface. The multi-sheeted Fermi surfaces of the nickel borocarbides are probed using angle-resolved positron annihilation spectroscopy, described by Dugdale et al, leading to a full three-dimensional picture of the complex Fermi surface in this superconducting material. Possible evidence for multigap superconductivity in the iron pnictides, obtained using Andreev point contact spectroscopy, is described by Samuely et al. The iron pnictides are also the subject of the article by

  10. Fabrication of high critical current density superconducting tapes by epitaxial deposition of YBCO thick films on biaxially textured metal substrates

    SciTech Connect

    Goyal, A.; Norton, D.P.; Paranthaman, M.

    1996-12-31

    High critical current density YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO) tapes were fabricated by epitaxial deposition on rolling- assisted-biaxially-textured-substrates (RABiTS). The RABiTS technique uses well established, industrially scaleable, thermomechanical processes to impart a strong biaxial texture to a base metal. This is followed by vapor deposition of epitaxial buffer layers to yield chemically and structurally compatible surfaces. Epitaxial YBCO films grown on such substrates have critical current densities approaching 10{sup 6} A/cm{sup 2} at 77K in zero field and have field dependences similar to epitaxial films on single crystal ceramic substrates. Deposited conductors made using this technique offer a potential route for fabricating long lengths of high J{sub c} wire capable of carrying high currents in high magnetic fields and at elevated temperatures.

  11. Anisotropic type-I superconductivity and anomalous superfluid density in OsB2

    DOE PAGES

    Bekaert, Jonas; Vercauteren, S.; Aperis, A.; ...

    2016-10-12

    Here, we present a microscopic study of superconductivity in OsB2, and discuss the origin and characteristic length scales of the superconducting state. From first-principles we show that OsB2 is characterized by three different Fermi sheets, and we prove that this fermiology complies with recent quantum-oscillation experiments. Using the found microscopic properties, and experimental data from the literature, we employ Ginzburg-Landau relations to reveal that OsB2 is a distinctly type-I superconductor with a very low Ginzburg-Landau parameter κ—a rare property among compound materials. We show that the found coherence length and penetration depth corroborate the measured thermodynamic critical field. Moreover, ourmore » calculation of the superconducting gap structure using anisotropic Eliashberg theory and ab initio calculated electron-phonon interaction as input reveals a single but anisotropic gap. The calculated gap spectrum is shown to give an excellent account for the unconventional behavior of the superfluid density of OsB2 measured in experiments as a function of temperature. This reveals that gap anisotropy can explain such behavior, observed in several compounds, which was previously attributed solely to a two-gap nature of superconductivity.« less

  12. Anisotropic type-I superconductivity and anomalous superfluid density in OsB2

    NASA Astrophysics Data System (ADS)

    Bekaert, J.; Vercauteren, S.; Aperis, A.; Komendová, L.; Prozorov, R.; Partoens, B.; Milošević, M. V.

    2016-10-01

    We present a microscopic study of superconductivity in OsB2, and discuss the origin and characteristic length scales of the superconducting state. From first-principles we show that OsB2 is characterized by three different Fermi sheets, and we prove that this fermiology complies with recent quantum-oscillation experiments. Using the found microscopic properties, and experimental data from the literature, we employ Ginzburg-Landau relations to reveal that OsB2 is a distinctly type-I superconductor with a very low Ginzburg-Landau parameter κ —a rare property among compound materials. We show that the found coherence length and penetration depth corroborate the measured thermodynamic critical field. Moreover, our calculation of the superconducting gap structure using anisotropic Eliashberg theory and ab initio calculated electron-phonon interaction as input reveals a single but anisotropic gap. The calculated gap spectrum is shown to give an excellent account for the unconventional behavior of the superfluid density of OsB2 measured in experiments as a function of temperature. This reveals that gap anisotropy can explain such behavior, observed in several compounds, which was previously attributed solely to a two-gap nature of superconductivity.

  13. Magnetism and superconductivity in a quasi-2D anisotropic system doped with charge carriers

    SciTech Connect

    Palistrant, M. E.

    2016-07-15

    The theory of multiband superconducting systems with variable density of charge carriers is analyzed. The possibility of emergence of nonphonon high-temperature superconductivity due to the predominance of electron–electron interband interactions over intraband interactions, as well as due to the fact that the thermodynamic and magnetic properties of multiband systems in the superconducting phase differ qualitatively from those of single-band systems, is indicated. Phase transitions in a quasi-2D anisotropic medium upon a change in the carrier concentration, i.e., a transition from the commensurate to the incommensurate state of the spin density wave, are analyzed. Such a transition is observed when the Umklapp processes in the lattice structure are taken into account. These processes facilitate a deviation of wavevector Q of the spin density wave from 2k{sub F}, as well as a displacement of the bandgap relative to the Fermi surface. This leads to the generation of free charge carriers and the possibility of superconductivity. It is shown that superconductivity accompanies the magnetism. The conditions for the coexistence of these two phenomena are determined.

  14. Increasing the sensitivity of the spectrophotometric determinations of the oxygen content in YBCO superconducting samples using the I(3-)-starch compound.

    PubMed

    Nedeltcheva, Tsvetanka K; Georgieva, Stela Iv; Vladimirova, Latinka K; Stoyanova-Ivanova, Angelina K

    2009-03-15

    The conditions for formation of the I(3)(-)-starch compound and measuring its absorbance have been found, and a spectrophotometric method has been developed for the determination of the oxygen content in YBa(2)Cu(3)O(y) superconducting bulk samples. The method involves the following stages: a decomposition of the sample in an acid medium in the presence of iodide ions under inert atmosphere; formation of a complex between Cu(II) and glycine; binding the I(3)(-)-complex with a starch and the absorbance measurement of the colored I(3)(-)-starch compound. The coefficient of the active oxygen is calculated by the ratio of the absorbances of two solutions and the method does not require both calibration and precise measuring sample mass. The accuracy of the results is confirmed applying the comparative spectrophotometric method that uses the yellow I(3)(-)-complex. The precision of the results evaluated by the relative standard deviation is 2%. The developed method is sensitive and allows a sample mass about 2mg to be used. The analysis is rapid and requires a simple and inexpensive apparatus. Thus the new method would be useful for an express analytical control of the oxygen content of YBCO-superconducting materials produced for the electronics.

  15. Anomalous metallic state and anisotropic multiband superconductivity in Nb3Pd0.7Se7

    NASA Astrophysics Data System (ADS)

    Zhang, Q. R.; Rhodes, D.; Zeng, B.; Besara, T.; Siegrist, T.; Johannes, M. D.; Balicas, L.

    2013-07-01

    We report the discovery of superconductivity in Nb3PdxSe7 with an x-dependent superconducting transition temperature as high as Tc≃2.1 K for x≃0.7 (middle point of the resistive transition). Needlelike single crystals display anisotropic upper-critical fields with an anisotropy γ=Hc2b/Hc2a as large as 6 between fields applied along their needle axis (or b axis) or along the a axis. As for the Fe based superconductors γ is temperature-dependent, suggesting that Nb3Pd0.7Se7 is a multiband superconductor. This is supported by band structure calculations which reveal a Fermi surface composed of quasi-one-dimensional and quasi-two-dimensional sheets of hole character, as well as three-dimensional sheets of both hole and electron character. Remarkably, Hc2b is observed to saturate at Hc2b(T→0K)≃14.1 T which is 4.26×Hp where Hp is the Pauli-limiting field in the weak-coupling regime. The synthesis procedure yields additional crystals belonging to the Nb2PdxSe5 phase which also becomes superconducting when the fraction of Pd is varied. For both phases we find that superconductivity condenses out of an anomalous metallic state, i.e., displaying ∂ρ/∂T<0 above Tc similarly to what is observed in the pseudogap phase of the underdoped cuprates. An anomalous metallic state, low-dimensionality, multiband character, extremely high and anisotropic Hc2's are all ingredients for unconventional superconductivity.

  16. Anisotropic superconductivity in La(O,F)BiSeS crystals revealed by field-angle dependent Andreev reflection spectroscopy

    NASA Astrophysics Data System (ADS)

    Aslam, Mohammad; Gayen, Sirshendu; Singh, Avtar; Tanaka, Masashi; Yamaki, Takuma; Takano, Yoshihiko; Sheet, Goutam

    2017-09-01

    From field-angle dependent Andreev reflection spectroscopy on single crystals of La(O,F)BiSeS, which belongs to the recently discovered BiCh 2 (Ch = S, Se) based layered superconductors, we found that the superconductivity in La(O,F)BiSeS is highly anisotropic. We measured a superconducting energy gap of 0.61 meV for current injected along c-axis at 1.5 K. Detailed temperature and magnetic field dependent studies of the gap also reveal the presence of unconventional pairing in La(O,F)BiSeS. We show that the observed anisotropic superconducting properties can be attributed to the anisotropy in the superconducting order parameter with a complex symmetry in superconducting La(O,F)BiSeS.

  17. EPR and speciation simulation study of Cu2+ complexes in an amine-based aqueous precursor system used for preparation of superconducting YBCO coatings.

    PubMed

    Lommens, Petra; Feys, Jonas; Vrielinck, Henk; De Buysser, Klaartje; Herman, Gerrit; Callens, Freddy; Van Driessche, Isabel

    2012-03-28

    In this work, we investigate the chemistry for an aqueous acetate-triethanolamine-ammonia based YBa(2)Cu(3)O(7-δ) (YBCO) precursor system. These precursor solutions are suited for the chemical solution deposition of superconducting YBCO layers on top of single crystal SrTiO(3) or buffered NiW tapes. The development of this kind of precursor inks often involves trial-and-error experimenting and thus is very time-consuming. To reduce labwork to the minimum, the theoretical prediction of pH stability limits and the complexation behaviour of the different metal ions and complexants in the inks are very important. For this purpose, we simulated, based on literature values, the complexation behaviour of Cu(2+) in the aqueous precursor solutions as a function of pH. To validate the used model, we performed potentiometric pH titrations for solutions with similar composition and checked the correctness of fit between experiment and model. The generated complexometric results are coupled with X-band EPR spectra to further confirm the results. EPR spectra for fully prepared precursor solutions as well as for Cu(2+) reference solutions containing only one type of ligand (acetate, triethanolamine or ammonia) were investigated as a function of pH. We find that, in line with speciation simulation, only acetates are actively complexing the Cu(2+) ions at pH values below 7, while when reaching higher pH levels mainly triethanolamine complexes are formed. Over the entire pH range, no trace of free Cu(2+)or Cu(OH)(2), possibly creating precipitation during gelation and thus complicating further processing, could be found.

  18. Radiation and Resonant Frequency of Superconducting Annular Ring Microstrip Antenna on Uniaxial Anisotropic Media

    NASA Astrophysics Data System (ADS)

    Barkat, Ouarda; Benghalia, Abdelmadjid

    2009-10-01

    In this work, the full-wave method is used for computing the resonant frequency, the bandwidth, and radiation pattern of High temperature superconductor, or an imperfectly conducting annular ring microstrip, which is printed on uniaxial anisotropic substrate. Galerkin’s method is used in the resolution of the electric field integral equation. The TM set of modes issued from the cavity model theory are used to expand the unknown currents on the patch. Numerical results concerning the effect of the anisotropic substrates on the antenna performance are presented and discussed. It is found that microstrip superconducting could give high efficiency with high gain in millimeter wavelengths. Results are compared with previously published data and are found to be in good agreement.

  19. Development of HTS power cable using YBCO coated conductor

    NASA Astrophysics Data System (ADS)

    Mukoyama, Shinichi; Yagi, Masashi; Hirano, Hironobu; Yamada, Yutaka; Izumi, Teruo; Shiohara, Yuh

    2006-10-01

    Reductions of AC losses and of cost of HTS power cables are important to put it into practical power networks. Since an YBCO-coated-conductor (YBCO tape) has higher Jc and better magnetic property than a Bi2223-Ag-sheathed-tape, an AC power cable using YBCO tapes will obtain higher performance than XLPE-cables and HTS cables using BSCCO tapes in future. Especially, an YBCO HTS cable will be expected to become a higher economical cable than a Bi cable because an YBCO tape reduced its AC losses and its wire cost. We have started developing HTS power cables using YBCO tapes. Mechanical properties, superconducting properties and other electro magnetic properties of YBCO tapes have been measured to estimate the applicability to the HTS cable. Moreover, we have developed some technologies to bring out latent potentials of YBCO tapes.

  20. Anisotropic superconductivity in β-(BDA-TTP)2SbF6: STM spectroscopy

    NASA Astrophysics Data System (ADS)

    Nomura, K.; Muraoka, R.; Matsunaga, N.; Ichimura, K.; Yamada, J.

    2009-03-01

    We have investigated the gap symmetry in the superconducting phase of β-(BDA-TTP)2SbF6 with use of the scanning tunneling microscope (STM). The tunneling spectra obtained on the conducting surface show a clear superconducting gap structure. Its functional form is of V-shaped similarly to κ-(BEDT-TTF)2X and suggests the anisotropic superconducting gap with line nodes. For lateral surfaces the shape of tunneling spectra varies from the U-shape with relatively large gap to the V-shape with small gap depending on the tunneling direction alternately twice between directional angle 0 and π. From the analysis of conductance curve taking the k dependence of the tunneling probability into account, it is found that the gap has maximum near the a* and c* axes and the nodes appear along near a*+c* and the a-c* directions. These indicate that the d like superconducting pair is formed in this system as the case of κ-(BEDT-TTF)2X. This node direction is consistent with the theoretical prediction based on the spin fluctuation mechanism. However, the zero-bias conductance peak has not been observed yet.

  1. Highly anisotropic superconducting gaps and possible evidence of antiferromagnetic order in FeSe single crystals

    NASA Astrophysics Data System (ADS)

    Chen, Guan-Yu; Zhu, Xiyu; Yang, Huan; Wen, Hai-Hu

    2017-08-01

    Specific heat has been measured in FeSe single crystals down to 0.414 K under magnetic fields up to 16 T. A sharp specific-heat anomaly is observed at the superconducting transition temperature Tc=8.2 K. Another jump of specific-heat coefficient C /T is observed at about 1.08 K which is argued to be the long sought antiferromagnetic transition in bulk FeSe. Global fitting to electronic specific heat in a wide temperature region shows that the models with a single contribution with isotropic s -wave, anisotropic s -wave, and d -wave gaps all do not work well, nor the two isotropic s -wave gaps. We then fit the data by a model with two components in which one has the gap function of Δ0(1 +α cos2 θ ) . To have a good global fitting and the entropy conservation for the low-temperature transition, we conclude that the gap minimum should be smaller than 0.15 meV (α =0.9 to 1), indicating that the superconducting gap(s) are nodeless but highly anisotropic. Our results are quite consistent with the gap structure derived recently from scanning tunneling spectroscopy measurements and yield specific-heat contributions of about 32% weight from the hole pocket and 68% from the electron pockets.

  2. On the suppression of superconducting phase formation in YBCO materials by templated synthesis in the presence of a sulfated biopolymer

    NASA Astrophysics Data System (ADS)

    Smith, Elliott; Schnepp, Zoe; Wimbush, Stuart C.; Hall, Simon R.

    2008-11-01

    The use of biopolymers as templates to control superconductor crystallization is a recent phenomenon and is generating a lot of interest both from the superconductor community and in materials chemistry circles. This work represents a critical finding in the use of such biopolymers, in particular the contraindicatory nature of sulfur when attempting to affect a morphologically controlled synthesis. Synthesis of superconducting nanoparticles was attempted using carrageenan as a morphological template. Reactive sulfate groups on the biopolymer prevent this, producing instead significant quantities of barium sulfate nanotapes. By substituting the biopolymer for structurally analogous, non-sulfated agar, we show that superconducting nanoparticles could be successfully synthesized.

  3. YBCO COATED CONDUCTORS

    SciTech Connect

    Paranthaman, Mariappan Parans

    2010-01-01

    carefully aligning the grains in YBCO films, low angle boundaries between superconducting YBCO grains allow more current to flow. In fact below a critical misalignment angle of 4 , the critical current density approaches that of YBCO films grown on single crystal substrates [10]. Typically, 2G HTS wires have three components, flexible metal substrate, buffer layers, and REBa2Cu3O7- (REBCO: RE = Rare Earth) superconductor layers [1-7]. Several methods were developed to obtain biaxially textured templates suitable for fabricating high-performance YBCO coated conductors. They are Ion-Beam Assisted Deposition (IBAD), Rolling-Assisted Biaxially Textured Substrates (RABiTS) and Inclined-Substrate Deposition (ISD). Compared to 1G wire, for producing 2G wires using RABiTS or IBAD process, silver is replaced by a low cost nickel alloy, which allows for fabrication of less expensive HTS wires.

  4. High Critical Current in Metal Organic Derived YBCO Films

    DTIC Science & Technology

    2010-10-31

    Report 3 BACKGROUND The Second Generation (2G) high temperature superconducting (HTS) YBCO wire is a versatile, potentially transformational...transformers, fault current limiters, superconducting magnetic energy storage, and power transmission lines [ 1 ] require improvement in the performance of 2G...commercialization of 2G superconducting wire. The obvious route to higher Ic is to increase the thickness, t, of the YBa2Cu3O7-x (YBCO) layer

  5. Multiband superconductivity in Ta4Pd3Te16 with anisotropic gap structure.

    PubMed

    Jiao, Wen-He; Liu, Yi; Li, Yu-Ke; Xu, Xiao-Feng; Bao, Jin-Ke; Feng, Chun-Mu; Li, S Y; Xu, Zhu-An; Cao, Guang-Han

    2015-08-19

    We carried out measurements of the magnetoresistance, magnetic susceptibility and specific heat on crystals of the low-dimensional transition metal telluride Ta4Pd3Te16. Our results indicate that Ta4Pd3Te16 is an anisotropic type-II superconductor in the clean limit with the extracted Ginzburg-Landau parameter KGL = 84. The upper critical field Hc2(T) shows an anomalous temperature dependence at low temperatures and the anisotropy of Hc2(T) is strongly T-dependent, both of which indicate a multiband scenario. The electronic specific heat Cel(T) can be consistently described by a two-gap (s   +   d waves) model from the base temperature T/Tc ~ 0.12 up to Tc. Our results suggest nodal and multiband superconductivity in Ta4Pd3Te16.

  6. Scaling behaviour and superconducting instability in anisotropic non-Fermi liquids

    NASA Astrophysics Data System (ADS)

    Mandal, Ipsita

    2017-01-01

    We study the scaling behaviour of the optical conductivity (σ) , free energy density (F) and shear viscosity of the quantum critical point associated with spin density wave phase transition for a two-dimensional metallic system with C2 symmetry. A non-Fermi liquid behaviour emerges at two pairs of isolated points on the Fermi surface due to the coupling of a bosonic order parameter to fermionic excitations at those so-called "hot-spots". We find that near the hot-spots, σ and F obey the scalings expected for such an anisotropic system, and the direction-dependent viscosity to entropy density ratio is not a universal number due to the anisotropy. Lastly, we also estimate the effect of the fermion-boson coupling at the hot-spots on superconducting instabilities.

  7. Isotropic and anisotropic description of superconducting state in CaC6 compound

    NASA Astrophysics Data System (ADS)

    Szczȩśniak, R.; Drzazga, E. A.; Szczȩśniak, D.

    2015-02-01

    The thermodynamic parameters of the superconducting state in CaC6 have been determined in the framework of the isotropic and anisotropic Eliashberg formalism. The obtained results determine the anisotropy effect on the values of the thermodynamic functions. In particular, it has been found that the anisotropy of the electron-phonon coupling constant and the Coulomb pseudopotential significantly affects the order parameter and the wave function renormalization factor, which determines the electron effective mass. These results mean that anisotropy should be also visible in the total normalized density of states. In the case of the thermodynamic critical field, anisotropy lowers its value in the low-temperature area. On the other hand, it does not affect the specific heat jump at the critical temperature.

  8. Influence of annealing in oxygen and argon on the superconducting properties of Li-doped YBCO single-grain bulks

    NASA Astrophysics Data System (ADS)

    Antal, V.; Volochová, D.; Kavečanský, V.; Kováč, J.; Diko, P.

    2017-10-01

    YBa2(Cu1-xLix)3O7-δ single-grain bulk superconductors with different Li concentrations were grown using the top-seeded melt growth process. Structural analysis of the samples and magnetisation measurements showed that substitution of the Cu atoms by the Li atoms took place in the YBa2Cu3O7-δ crystal lattice. This substitution was accompanied by the formation of effective pinning centres, which improved the pinning properties of the samples and increased the critical current density. Additional annealing and reannealing in oxygen and argon showed that the superconducting transition temperature displays substantially more suppression, when the Li-doped YBa2Cu3O7-δ samples were annealed in argon, that was associated with different distribution of the Li atoms between the CuO chains and the CuO2 planes in comparison to annealing in oxygen. Investigation of the critical current densities showed that the pinning properties of YBa2(Cu1-xLix)3O7-δ single-grain bulk superconductors did not depend on the arrangement of the Li atoms in the YBa2Cu3O7-δ crystal lattice. It was also observed that the crystal lattice parameters and the mean diameter of the non-superconducting Y2BaCuO5 particles systematically change with Li concentration.

  9. Anisotropic superconductivity and vortex dynamics in magnetially coupled F/S and F/S/F hybrids.

    SciTech Connect

    Karapetrov, G.; Belkin, A.; Iavarone, M.; Fedor, J.; Novosad, V.; Milosevic, M. V.; Peeters, F. M.

    2011-01-01

    Magnetically coupled superconductor-ferromagnet hybrids offer advanced routes for nanoscale control of superconductivity. Magnetotransport characteristics and scanning tunneling microscopy images of vortex structures in superconductor-ferromagnet hybrids reveal rich superconducting phase diagrams. Focusing on a particular combination of a ferromagnet with a well-ordered periodic magnetic domain structure with alternating out-of-plane component of magnetization, and a small coherence length superconductor, we find directed nucleation of superconductivity above the domain wall boundaries. We show that near the superconductor-normal state phase boundary the superconductivity is localized in narrow mesoscopic channels. In order to explore the Abrikosov flux line ordering in F/S hybrids, we use a combination of scanning tunneling microscopy and Ginzburg-Landau simulations. The magnetic stripe domain structure induces periodic local magnetic induction in the superconductor, creating a series of pinning-anti-pinning channels for externally added magnetic flux quanta. Such laterally confined Abrikosov vortices form quasi-1D arrays (chains). The transitions between multichain states occur through propagation of kinks at the intermediate fields. At high fields we show that the system becomes nonlinear due to a change in both the number of vortices and the confining potential. In F/S/F hybrids we demonstrate the evolution of the anisotropic conductivity in the superconductor that is magnetically coupled with two adjacent ferromagnetic layers. Stripe magnetic domain structures in both F-layers are aligned under each other, resulting in a directional superconducting order parameter in the superconducting layer. The conductance anisotropy strongly depends on the period of the magnetic domains and the strength of the local magnetization. The anisotropic conductivity of up to three orders of magnitude can be achieved with a spatial critical temperature modulation of 5% of T{sub c

  10. Competition between superconductivity and magnetic/nematic order as a source of anisotropic superconducting gap in underdoped Ba1-xKxFe2As2

    SciTech Connect

    Kim, H; Tanatar, M A; Straszheim, W E; Cho, K; Murphy, J; Spyrison, N; Reid, J -Ph; Shen, Bing; Wen, Hai-Hu; Fernandes, R M; Prozorov, R

    2014-07-01

    The in-plane London penetration depth Δλ(T) was measured using a tunnel diode resonator technique in single crystals of Ba1-xKxFe2As2 with doping levels x ranging from heavily underdoped, x=0.16 (Tc=7K), to nearly optimally doped, x=0.34 (Tc=39K). Exponential saturation of Δλ(T) in the T→0 limit is found in optimally doped samples, with the superfluid density ρs(T)≡[λ(0)/λ(T)]2 quantitatively described by a self-consistent γ model with two nodeless isotropic superconducting gaps. As the doping level is decreased towards the extreme end of the superconducting dome at x=0.16, the low-temperature behavior of Δλ(T) becomes nonexponential and is best described by the power law Δλ(T)∝T2, characteristic of strongly anisotropic gaps. The change between the two regimes happens within the range of coexisting magnetic/nematic order and superconductivity, x<0.25, and is accompanied by a rapid rise in the absolute value of Δλ(T) with underdoping. This effect, characteristic of the competition between superconductivity and other ordered states, is very similar to but of significantly smaller magnitude than what is observed in the electron-doped Ba(Fe1-xCox)2As2 compounds. Our study suggests that the competition between superconductivity and magnetic/nematic order in hole-doped compounds is weaker than in electron-doped compounds, and that the anisotropy of the superconducting state in the underdoped iron pnictides is a consequence of the anisotropic changes in the pairing interaction and in the gap function promoted by both magnetic and nematic long-range orders.

  11. Fourcross shaped metamaterial filters fabricated from high temperature superconducting YBCO and Au thin films for terahertz waves

    NASA Astrophysics Data System (ADS)

    Demirhan, Y.; Alaboz, H.; Nebioğlu, M. A.; Mulla, B.; Akkaya, M.; Altan, H.; Sabah, C.; Ozyuzer, L.

    2017-07-01

    In this study, we present a new, unique fourcross shaped metamaterial terahertz (THz) filter fabricated from both gold thin films and YBa2Cu3O7-d high T c superconducting thin films. A commercial electromagnetic simulation software, CST Microwave Studio, is used to design and optimize the metamaterial filter structures. The proposed fourcross shaped rectangular filter structure consists of periodic metallic rings where strip lines are located at the sides of the ring. Fourcross metamaterial filters are fabricated by using e-beam lithography and ion beam etching techniques. Terahertz time-domain spectroscopy measurements validated the design predictions for both the center frequencies and bandwidths of the resonances due to the fourcross structures. The resonance switching of the transmission spectra was investigated by lowering the temperature below the critical transition temperature. This resonance switching effect is not observed in filters made up of metals. This novel fourcross rectangular resonator with a temperature-dependent resonance behavior holds great potential for active, tunable and low loss THz devices for imaging, sensing, and detection applications.

  12. Possible weakly first-order superconducting transition induced by magnetic excitations in the YBCO system: A fluctuation conductivity study

    NASA Astrophysics Data System (ADS)

    Hneda, Marlon Luiz; da Silva Berchon, Luciano; Pureur, Paulo; das Neves Vieira, Valdemar; Jaeckel, Sandra Teixeira; Dias, Fábio Teixeira; Menegotto Costa, Rosângela

    2017-04-01

    Fluctuation conductivity is experimentally studied in the genuine critical region near the superconducting transition of YBa2Cu3O7 - δ, YBa2Cu2.985Fe0.015O7 - δ and Y0.95Ca0.05Ba2Cu3O7 - δ single crystal samples. Two fluctuation regimes where the electrical conductivity diverges as a power-law of the reduced temperature were systematically observed. In the first regime, farther from the critical temperature Tc, the transition behaves as predicted by the thermodynamics of the three dimensional-XY (3D-XY) universality class characteristic of a second-order phase transition. In the asymptotic regime closer to Tc a power-law regime characterized by a much smaller exponent is observed. The smallest value ever reported for the fluctuation conductivity exponent in the high-Tc superconductors is obtained for the Fe- and Ca-doped systems. We suggest that the regime beyond 3D-XY is a crossover towards a weakly first-order transition induced by internal magnetic excitations.

  13. Superconducting properties of nano-sized SiO2 added YBCO thick film on Ag substrate

    NASA Astrophysics Data System (ADS)

    Almessiere, Munirah Abdullah; Al-Otaibi, Amal lafy; Azzouz, Faten Ben

    2017-10-01

    The microstructure and the flux pinning capability of SiO2-added YBa2Cu3Oy thick films on Ag substrates were investigated. A series of YBa2Cu3Oy thick films with small amounts (0-0.5 wt%) of nano-sized SiO2 particles (12 nm) was prepared. The thicknesses of the prepared thick films was approximately 100 µm. Phase analysis by x-ray diffraction and microstructure examination by scanning electron microscopy were performed and the critical current density dependence on the applied magnetic field Jc(H) and electrical resistivity ρ(T) were investigated. The magnetic field and temperature dependence of the critical current density (Jc) was calculated from magnetization measurements using Bean's critical state model. The results showed that the addition of a small amount (≤0.02 wt%) of SiO2 was effective in enhancing the critical current densities in the applied magnetic field. The sample with 0.01 wt% of added SiO2 exhibited a superconducting characteristics under an applied magnetic field for a temperature ranging from 10 to 77 K.

  14. Enhancement of superconducting transition temperature by pointlike disorder and anisotropic energy gap in FeSe single crystals

    DOE PAGES

    Teknowijoyo, S.; Cho, K.; Tanatar, M. A.; ...

    2016-08-29

    A highly anisotropic superconducting gap is found in single crystals of FeSe by studying the London penetration depth Δλ measured down to 50 mK in samples before and after 2.5 MeV electron irradiation. The gap minimum increases with introduced pointlike disorder, indicating the absence of symmetry-imposed nodes. Surprisingly, the superconducting transition temperature Tc increases by 0.4 K from Tc0 ≈ 8.8 K while the structural transition temperature Ts decreases by 0.9 K from Ts0 ≈ 91.2 K after electron irradiation. Finally, we discuss several explanations for the Tc enhancement and propose that local strengthening of the pair interaction by irradiation-inducedmore » Frenkel defects most likely explains the phenomenon.« less

  15. Enhancement of superconducting transition temperature by pointlike disorder and anisotropic energy gap in FeSe single crystals

    SciTech Connect

    Teknowijoyo, S.; Cho, K.; Tanatar, M. A.; Gonzales, J.; Böhmer, A. E.; Cavani, O.; Mishra, V.; Hirschfeld, P. J.; Bud'ko, S. L.; Canfield, P. C.; Prozorov, R.

    2016-08-29

    A highly anisotropic superconducting gap is found in single crystals of FeSe by studying the London penetration depth Δλ measured down to 50 mK in samples before and after 2.5 MeV electron irradiation. The gap minimum increases with introduced pointlike disorder, indicating the absence of symmetry-imposed nodes. Surprisingly, the superconducting transition temperature Tc increases by 0.4 K from Tc0 ≈ 8.8 K while the structural transition temperature Ts decreases by 0.9 K from Ts0 ≈ 91.2 K after electron irradiation. Finally, we discuss several explanations for the Tc enhancement and propose that local strengthening of the pair interaction by irradiation-induced Frenkel defects most likely explains the phenomenon.

  16. Ground State Properties and Localized Excited States around a Magnetic Impurity Described by the Anisotropic s- d Interaction in Superconductivity

    NASA Astrophysics Data System (ADS)

    Yoshioka, Tomoki; Ohashi, Yoji

    1998-04-01

    We investigate the electronic state around a magnetic impurity in thesuperconductivity in order to clarify how the anisotropy of thes-d interaction works in the presence of the superconductingenergy gap. Using the numerical renormalization group method, weobtain regions induced by the anisotropy where two localizedexcited states with different energies appear at the same time; theycannot obtain as far as the isotropic interaction is considered. Thismeans that the anisotropy of the s-d interaction works relevantlyin some cases in the superconducting state. We also examine whether ornot the bound state energy for the anisotropic and antiferromagnetics-d interaction is scaled by T K/Δ (T K: Kondotemperature, Δ: superconducting order parameter), and find thatit does not hold in the regions with two bound states.

  17. Enhancement of superconducting transition temperature by pointlike disorder and anisotropic energy gap in FeSe single crystals

    SciTech Connect

    Teknowijoyo, S.; Cho, K.; Tanatar, M. A.; Gonzales, J.; Böhmer, A. E.; Cavani, O.; Mishra, V.; Hirschfeld, P. J.; Bud'ko, S. L.; Canfield, P. C.; Prozorov, R.

    2016-08-29

    A highly anisotropic superconducting gap is found in single crystals of FeSe by studying the London penetration depth Δλ measured down to 50 mK in samples before and after 2.5 MeV electron irradiation. The gap minimum increases with introduced pointlike disorder, indicating the absence of symmetry-imposed nodes. Surprisingly, the superconducting transition temperature Tc increases by 0.4 K from Tc0 ≈ 8.8 K while the structural transition temperature Ts decreases by 0.9 K from Ts0 ≈ 91.2 K after electron irradiation. Finally, we discuss several explanations for the Tc enhancement and propose that local strengthening of the pair interaction by irradiation-induced Frenkel defects most likely explains the phenomenon.

  18. Anisotropic Field Dependence of the Superconducting Transition in the Magnetic Molecular Superconductor κ-(BETS)2FeBr4

    NASA Astrophysics Data System (ADS)

    Fukuoka, Shuhei; Yamashita, Satoshi; Nakazawa, Yasuhiro; Yamamoto, Takashi; Fujiwara, Hideki

    2017-01-01

    Angle-resolved heat capacity measurements of a π-d interacting system of κ-(BETS)2FeBr4 [BETS = bis(ethylenedithio)tetraselenafulvalene] with in-plane magnetic fields are performed. We observed a thermal anomaly in association with the superconducting transition of the π electrons in the π-d compound for the first time. By pursuing a systematic change in the thermal anomaly, we found that the thermodynamic feature of the superconducting state shows large anisotropy against in-plane magnetic fields. When the field is applied parallel to the c-axis, the thermal anomaly remains up to 2.6 T with a distinct peak structure. On the other hand, it is suppressed in synchrony with the decrease of the antiferromagnetic transition temperature, when the field is applied parallel to the a-axis. Our thermodynamic results indicate that the effect of the π-d interaction appears even when the π electrons are itinerant and that the anisotropic field-direction dependence of the superconducting transition originates from the correlation between superconductivity and magnetism.

  19. Structural Characterization of the Ag/ybco Interface

    NASA Astrophysics Data System (ADS)

    Tidjani, Mohammed Elkhamis

    1990-01-01

    The present research is intended to characterize the interface microstructure and long term stability of the deposited silver metal in contact to the superconducting oxide YBa_2Cu_3O _{rm 7-x} (YBCO). High resolution transmission electron microscopy (HRTEM) observations of the interfacial regions reveal that Ag contacts to YBCO occurred without any intermediate phase formation at the interface. The Ag metal exhibits a preferred orientation relationship with YBCO, in which the densely packed planes and directions of the metal are parallel to those of the superconductor. The formation of (111) interfaces and facets during deposition indicates that these planes are associated with the lowest interfacial energy. The as-deposited Ag film exhibits a granular morphology, and the Ag grains are often twinned along the (111) plane while the surface of YBCO is mostly rough and structurally unstable. Annealing of the Ag/YBCO interface resulted in outdiffusion of yttrium and oxygen at regions where the surface of YBCO was rough. This diffusion, however, did not result in the formation of continuous layers at the Ag/YBCO interface but only to growth of Ag_2 Y and Ag_2O inclusions. Thus it is believed that the stability of the Ag/YBCO depends on the quality of the surface of YBCO, especially its structure. Treatment of the surface of YBCO by ion-bombardment yielded flat surfaces but damaged a layer of about 30A. Such a cleaning process improved the quality of the deposited Ag since the Ag grains were larger and contained low defects concentration. The same orientation relationships between Ag and YBCO were observed after cleaning the surface of YBCO which implied that the destruction of the structure at the surface is only partial. Deposition of Ag in the same chamber where YBCO was initially grown, to minimize the contamination of the surface of YBCO, also was not effective in enhancing the structure of the Ag/YBCO interface. The roughness of the surface of YBCO did not decrease

  20. Near-field techniques for probing collective modes of anisotropic superconducting thin films

    NASA Astrophysics Data System (ADS)

    Stinson, H. T.; Wu, J. S.; Jiang, B. Y.; Fei, Z.; Rodin, A. S.; Chapler, B.; McLeod, A. S.; Castro-Neto, A.; Lee, Y. S.; Fogler, M. M.; Basov, D. N.

    2014-03-01

    We propose the use of scattering-type scanning near-field optical microscopy (s-SNOM) to characterize the collective mode spectrum of anisotropic superconductors. To probe the dispersion of collective modes with large in-plane momenta, specifically surface plasmons and guided wave modes, we model the real-space interference patterns of modes launched by the sharp s-SNOM tip and their reflections off physical and electronic boundaries. In addition, we show that s-SNOM spectroscopy allows for a direct probe of the c-axis superfluid density in underdoped anisotropic superconductors with nanoscale spatial resolution.

  1. Anisotropic behaviour of transmission through thin superconducting NbN film in parallel magnetic field

    NASA Astrophysics Data System (ADS)

    Šindler, M.; Tesař, R.; Koláček, J.; Skrbek, L.

    2017-02-01

    Transmission of terahertz waves through a thin layer of the superconductor NbN deposited on an anisotropic R-cut sapphire substrate is studied as a function of temperature in a magnetic field oriented parallel with the sample. A significant difference is found between transmitted intensities of beams linearly polarised parallel with and perpendicular to the direction of applied magnetic field.

  2. Anomalous anisotropic compression behavior of superconducting CrAs under high pressure

    PubMed Central

    Yu, Zhenhai; Wu, Wei; Hu, Qingyang; Zhao, Jinggeng; Li, Chunyu; Yang, Ke; Cheng, Jinguang; Luo, Jianlin; Wang, Lin; Mao, Ho-kwang

    2015-01-01

    CrAs was observed to possess the bulk superconductivity under high-pressure conditions. To understand the superconducting mechanism and explore the correlation between the structure and superconductivity, the high-pressure structural evolution of CrAs was investigated using the angle-dispersive X-ray diffraction (XRD) method. The structure of CrAs remains stable up to 1.8 GPa, whereas the lattice parameters exhibit anomalous compression behaviors. With increasing pressure, the lattice parameters a and c both demonstrate a nonmonotonic change, and the lattice parameter b undergoes a rapid contraction at ∼0.18−0.35 GPa, which suggests that a pressure-induced isostructural phase transition occurs in CrAs. Above the phase transition pressure, the axial compressibilities of CrAs present remarkable anisotropy. A schematic band model was used to address the anomalous compression behavior of CrAs. The present results shed light on the structural and related electronic responses to high pressure, which play a key role toward understanding the superconductivity of CrAs. PMID:26627230

  3. Preparation and characterization of YBCO coating on metallic RABiT substrates by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Gonal, M. R.; Prajapat, C. L.; Igalwar, P. S.; Maji, B. C.; Singh, M. R.; Krishnan, M.

    2016-05-01

    Superconducting YBCO films are coated on metallic Rolling Assisted Bi-axially Textured Substrates (RABiTS) Ni-5wt % W (NiW) (002) substrate using pulsed laser deposition (PLD) system. Targets of YBa2Cu3O7-δ (YBCO) and buffer layers of Ceria and 8 mole % Yttria Stabilized Zirconia (YSZ) of high density are synthesized. At each stage of deposition coatings are characterized by XRD. Transport studies show superconducting nature of YBCO only when two successive buffer layers of YSZ and CeO2 are used.

  4. [Raman spectra of YBCO superconductor with hot ultrapressing treatment].

    PubMed

    Yang, Hai-feng; Wei, Le-han; Cao, Xiao-wei

    2002-02-01

    Laser Raman spectra of YBCO oxide superconductor with hot ultrapressing and annealing treatment are reported. In addition to improving physical properties, the spectra data show that the processing can also perfect orthorhombie phase and enhance lattice on orientation trend as well as is good for formation of two dimension CuO2 net. The relation between structure and the superconductivity has been discussed.

  5. High Tc YBCO superconductor deposited on biaxially textured Ni substrate

    DOEpatents

    Budai, John D.; Christen, David K.; Goyal, Amit; He, Qing; Kroeger, Donald M.; Lee, Dominic F.; List, III, Frederick A.; Norton, David P.; Paranthaman, Mariappan; Sales, Brian C.; Specht, Eliot D.

    1999-01-01

    A superconducting article includes a biaxially-textured Ni substrate, and epitaxial buffer layers of Pd (optional), CeO.sub.2 and YSZ, and a top layer of in-plane aligned, c-axis oriented YBCO having a critical current density (J.sub.c) in the range of at least 100,000 A/cm.sup.2 at 77 K.

  6. Quasiparticle dynamics in YBCO and YBCO/LSMO Using Femtosecond Optical Pulses

    NASA Astrophysics Data System (ADS)

    Lee, J.; Talbayev, D.; Xiong, J.; Zhu, J.; Jia, Q.; Taylor, A. J.; Prasankumar, R. P.

    2012-02-01

    The properties of various complex oxide systems, such as multiferroics, high-Tc superconductors and colossal magnetoresistance manganites, have been extensively studied for the past ˜25 years. In particular, the interplay between superconductivity (SC) and ferromagnetism (FM) is interesting from both academic and applied viewpoints. we have temporally resolved quasiparticle dynamics in multilayered films composed of the high-temperature superconductor YBCO and the ferromagnetic manganite LaSrMnO3 (LSMO) by performing temperature-dependent UOS experiments. In YBCO alone, we observed two distinct decay relaxation channels that have previously been related to the pseudogap and superconducting gaps and can be explained with the phenomenological Rothwarf-Taylor (RT) model. However, the fast sub-picosecond relaxation related to the pseudogap was not observed in our YBCO/LSMO heterostructures, possibly due to the influence of FM order These first UOS experiments on SC/FM heterostructures demonstrate the ability of UOS to quantify the influence of ferromagnetism on superconductivity through time domain measurements.

  7. Transport AC Losses in Striated YBCO Coated Conductors (Postprint)

    DTIC Science & Technology

    2012-02-01

    Introduction The recent development of Y1Ba2Cu3O7-δ (YBCO) coated conductors has made superconducting machines (such as generators and motors ) for high...where Ploss (in watts) is the power loss of the sample at operating temperature To, Tamb is the ambient temperature and η is the efficiency of the...compared with a conventional one. The relative importance of HTS machine efficiency vs the reduction in weight and volume of a superconducting machine

  8. Anisotropic magnetic and superconducting properties of aligned weak-ferromagnetic superconductor RuSr2GdCu2O8

    NASA Astrophysics Data System (ADS)

    Ku, H. C.; Chang, B. C.; Hsu, C. H.; Chen, Y. F.; Tai, M. F.

    2009-03-01

    The RuSr2GdCu2O8 Ru-1212 cuprate is a weak-ferromagnetic superconductor with a magnetic ordering of Ru moments at TN(Ru) = 131 K, a superconducting transition in the CuO2 layers at Tc = 56 K, and a low temperature Gd antiferromagnetic ordering at TN(Gd) = 2.5 K. The c-axis aligned powder can be achieved at room temperature using the field-rotation method where the tetragonal c-axis is perpendicular to the aligned magnetic field Ba and along the rotation axis. The anisotropic temperature dependence of magnetic susceptibility for the aligned powder down to 2 K indicates weak anisotropy with Xc > Xab at room temperature due to strong anisotropic Gd contribution and Xc < Xab below 185 K where strong Ru anisotropic short-range exchange interaction overtakes the Gd contribution. Anisotropic diamagnetic superconducting intragrain shielding signal of aligned microcrystalline powder-in-epoxy below vortex lattice melting temperature at 39 K in 1-G field is much weaker than the intergrain polycrystalline bulk sample signal due to the small grain size (d ~ 1-10 μm), long penetration depth (λab ~ 0.6 μm, λc ~ 2 μm) and the two-dimensional (2D) character of CuO2 layers.

  9. Anisotropic softening of magnetic excitations along the nodal direction in superconducting cuprates.

    PubMed

    Guarise, M; Dalla Piazza, B; Berger, H; Giannini, E; Schmitt, T; Rønnow, H M; Sawatzky, G A; van den Brink, J; Altenfeld, D; Eremin, I; Grioni, M

    2014-12-18

    The high-Tc cuprate superconductors are close to antiferromagnetic order. Recent measurements of magnetic excitations have reported an intriguing similarity to the spin waves--magnons--of the antiferromagnetic insulating parent compounds, suggesting that magnons may survive in damped, broadened form throughout the phase diagram. Here we show by resonant inelastic X-ray scattering on Bi(2)Sr(2)CaCu(2)O(8+δ) (Bi-2212) that the analogy with spin waves is only partial. The magnon-like features collapse along the nodal direction in momentum space and exhibit a photon energy dependence markedly different from the Mott-insulating case. These observations can be naturally described by the continuum of charge and spin excitations of correlated electrons. The persistence of damped magnons could favour scenarios for superconductivity built from quasiparticles coupled to spin fluctuations. However, excitation spectra composed of particle-hole excitations suggest that superconductivity emerges from a coherent treatment of electronic spin and charge in the form of quasiparticles with very strong magnetic correlations.

  10. Anisotropic type-I superconductivity and anomalous superfluid density in OsB2

    SciTech Connect

    Bekaert, Jonas; Vercauteren, S.; Aperis, A.; Komendova, L.; Prozorov, R.; Partoens, B.; Milosevic, Milorad V.

    2016-10-12

    Here, we present a microscopic study of superconductivity in OsB2, and discuss the origin and characteristic length scales of the superconducting state. From first-principles we show that OsB2 is characterized by three different Fermi sheets, and we prove that this fermiology complies with recent quantum-oscillation experiments. Using the found microscopic properties, and experimental data from the literature, we employ Ginzburg-Landau relations to reveal that OsB2 is a distinctly type-I superconductor with a very low Ginzburg-Landau parameter κ—a rare property among compound materials. We show that the found coherence length and penetration depth corroborate the measured thermodynamic critical field. Moreover, our calculation of the superconducting gap structure using anisotropic Eliashberg theory and ab initio calculated electron-phonon interaction as input reveals a single but anisotropic gap. The calculated gap spectrum is shown to give an excellent account for the unconventional behavior of the superfluid density of OsB2 measured in experiments as a function of temperature. This reveals that gap anisotropy can explain such behavior, observed in several compounds, which was previously attributed solely to a two-gap nature of superconductivity.

  11. High quality uniform YBCO film growth by the metalorganic deposition using trifluoroacetates

    NASA Astrophysics Data System (ADS)

    Wang, S. S.; Zhang, Z. L.; Wang, L.; Gao, L. K.; Liu, J.

    2017-03-01

    A need exists for the large-area superconducting YBa2Cu3O7-x (YBCO) films with high critical current density for microwave communication and/or electric power applications. Trifluoroacetic metalorganic (TFA-MOD) method is a promising low cost technique for large-scale production of YBCO films, because it does not need high vacuum device and is easily applicable to substrates of various shape and size. In this paper, double-sided YBCO films with maximum 2 in diameter were prepared on LaAlO3 substrates by TFA-MOD method. Inductive critical current densitiy Jc, microwave surface resistance Rs, as well as the microstructure were characterized. A newly homemade furnace system was used to epitaxially grown YBCO films, which can improve the uniformity of YBCO film significantly by gas supply and temperature distribution proper design. Results showed that the large area YBCO films were very uniform in microstructure and thickness distribution, an average inductive Jc in excess of 6 MA/cm2 with uniform distribution, and low Rs (10 GHz) below 0.3 mΩ at 77 K were obtained. Andthe film filter may be prepared to work at temperatures lower than 74 K. These results are very close to the highest value of YBCO films made by conventional vacuum method, so we show a very promising route for large-scale production of high quality large-area YBCO superconducting films at a lower cost.

  12. Superconductivity

    DTIC Science & Technology

    1989-07-01

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

  13. Quantitative magneto-optical analysis of the role of finite temperatures on the critical state in YBCO thin films

    NASA Astrophysics Data System (ADS)

    Albrecht, Joachim; Brück, Sebastian; Stahl, Claudia; Ruoß, Stephen

    2016-11-01

    We use quantitative magneto-optical microscopy to investigate the influence of finite temperatures on the critical state of thin YBCO films. In particular, temperature and time dependence of supercurrents in inhomogeneous and anisotropic films are analyzed to extract the role of temperature on the supercurrents themselves and the influence of thermally activated relaxation. We find that inhomogeneities and anisotropies of the current density distribution correspond to a different temperature dependence of local supercurrents. In addition, the thermally activated decay of supercurrents can be used to extract local vortex pinning energies. With these results the modification of vortex pinning introduced by substrate structures is studied. In summary the local investigation of supercurrent densities allows the full description of the vortex pinning landscape with respect to pinning forces and energies in superconducting films with complex properties under the influence of finite temperatures.

  14. Influence of oxygen partial pressure and silver additions on microstructure and related properties of YBCO superconductors

    SciTech Connect

    Singh, J.P.; Joo, J.; Guttschow, R.; Poeppel, R.B.

    1992-02-01

    Microstructure has a great influence on the mechanical and superconducting properties of YBCO. Mechanical properties of YBCO can be improved by both modifying the monolithic microstructure and developing composites of YBCO with silver (Ag). When monolithic YBCO was sintered to high densities ({approx} 91%) at a relatively low temperature ({approx} 910{degrees}C) by controlling oxygen partial pressure during sintering, the result was a small-grain microstructure (average grain size {approx} 5 {mu}m) and hence a high strength of 191 {plus_minus} 7 MPa. Addition of Ag as a second phase further improved the strength of YBCO. Composites of YBCO with 10 to 15 vol % Ag has a strength of 225 {plus_minus} 6 MPa and a fracture toughness of 3.3 {plus_minus} 0.2 MPa{radical}m. These improvements are believed to be due to compressive stresses in the YBCO matrix as a result of thermal mismatch between the YBCO and Ag phases. Furthermore, the Ag particles may provide increased resistance to crack propagation by pinning the crack. On the other hand, addition of Ag as a dopant to substitute for Cu sites in YBCO has a profound but nonmonotonic effect on grain microstructure and the resulting critical current density.

  15. Influence of oxygen partial pressure and silver additions on microstructure and related properties of YBCO superconductors

    SciTech Connect

    Singh, J.P.; Joo, J.; Guttschow, R.; Poeppel, R.B.

    1992-02-01

    Microstructure has a great influence on the mechanical and superconducting properties of YBCO. Mechanical properties of YBCO can be improved by both modifying the monolithic microstructure and developing composites of YBCO with silver (Ag). When monolithic YBCO was sintered to high densities ({approx} 91%) at a relatively low temperature ({approx} 910{degrees}C) by controlling oxygen partial pressure during sintering, the result was a small-grain microstructure (average grain size {approx} 5 {mu}m) and hence a high strength of 191 {plus minus} 7 MPa. Addition of Ag as a second phase further improved the strength of YBCO. Composites of YBCO with 10 to 15 vol % Ag has a strength of 225 {plus minus} 6 MPa and a fracture toughness of 3.3 {plus minus} 0.2 MPa{radical}m. These improvements are believed to be due to compressive stresses in the YBCO matrix as a result of thermal mismatch between the YBCO and Ag phases. Furthermore, the Ag particles may provide increased resistance to crack propagation by pinning the crack. On the other hand, addition of Ag as a dopant to substitute for Cu sites in YBCO has a profound but nonmonotonic effect on grain microstructure and the resulting critical current density.

  16. Anisotropic superconducting states in a CuO{sub 2} layer

    SciTech Connect

    Dickinson, P.H.

    1993-12-31

    The high-temperature superconductors share CuO{sub 2} layers as structural elements in which the Coulomb repulsion between holes on the Cu site is very large. As a result, the authors choose to model the system with a three-band Hubbard model including the Cu 3d(x{sup 2}{minus}y{sup 2}) and the O 2p(x,y) orbitals. The Coulomb repulsion on the Cu site is treated in the U {r_arrow} {infinity} limit using the slave boson formalism. They expand this model`s Lagrangian in a large N expansion considering terms up to order 1/N. The angle-resolved spectral weight determined from the resulting Green`s functions suggests that within this picture higher order corrections in 1/N are necessary for good agreement with the corresponding angle-resolved photoemission data. They phenomenologically add spin-dependent Heisenberg interactions between neighboring Cu sites and neighboring Cu and O sites. These interactions form the basis of a nonretarded calculation of the superconducting state. For an interaction between neighboring Cu spins only, the lowest energy solution possesses d(x{sup 2}{minus}y{sup 2}) symmetry. The use of a three-band model leads to the possibility of the addition of an interaction between Cu and O spins. The resulting novel {open_quotes}d + idp{close_quotes} superconducting state involves pairing of carriers in Cu orbitals both with themselves and with holes on the O orbitals. This additional pairing removes the node in the d-wave state at T = 0 by an amount which depends on the Cu-O coupling parameter; however, the mixed symmetry state occurs only for a narrow range of coupling parameters. The angle-resolved photo-emission and tunneling results are calculated and compared to experimental findings. As a function of decreasing temperature, symmetry arguments require transition to a d-wave state before transition to the d + idp state. A BCS analysis is performed on a tight-binding model.

  17. Soft nanostructuring of YBCO Josephson junctions by phase separation.

    PubMed

    Gustafsson, D; Pettersson, H; Iandolo, B; Olsson, E; Bauch, T; Lombardi, F

    2010-12-08

    We have developed a new method to fabricate biepitaxial YBa2 Cu3 O7-δ (YBCO) Josephson junctions at the nanoscale, allowing junctions widths down to 100 nm and simultaneously avoiding the typical damage in grain boundary interfaces due to conventional patterning procedures. By using the competition between the superconducting YBCO and the insulating Y2 BaCuO5 phases during film growth, we formed nanometer sized grain boundary junctions in the insulating Y2 BaCuO5 matrix as confirmed by high-resolution transmission electron microscopy. Electrical transport measurements give clear indications that we are close to probing the intrinsic properties of the grain boundaries.

  18. Superconductivity

    NASA Astrophysics Data System (ADS)

    Yeo, Yung K.

    Many potential high-temperature superconductivity (HTS) military applications have been demonstrated by low-temperature superconductivity systems; they encompass high efficiency electric drives for naval vessels, airborne electric generators, energy storage systems for directed-energy weapons, electromechanical launchers, magnetic and electromagnetic shields, and cavity resonators for microwave and mm-wave generation. Further HST applications in militarily relevant fields include EM sensors, IR focal plane arrays, SQUIDs, magnetic gradiometers, high-power sonar sources, and superconducting antennas and inertial navigation systems. The development of SQUID sensors will furnish novel magnetic anomaly detection methods for ASW.

  19. A Raman Investigation of YBCO/Linear Low Density Polyethylene (LLDPE) Composites

    NASA Astrophysics Data System (ADS)

    Bhadrakumaria, S.; Predeep, P.

    2011-10-01

    A series of flexible composites are formed by mixing High Temperature Superconducting YBCO and Linear Low Density Polyethylene (LLDPE) and the behaviour of these composites are investigated using Raman Spectroscopy. This study indicated the presence of well defined Raman lines. Raman spectra of pure YBCO and composite samples showed sharp bands and the intensity of these bands is found to decrease with decreasing proportion of the polymer in the composite, indicating the presence of characteristic structural units.

  20. The magnetoresistance of YBCO/BZO composite superconductors

    NASA Astrophysics Data System (ADS)

    Malik, Bilal A.; Asokan, K.; Ganesan, V.; Singh, Durgesh; Malik, Manzoor A.

    2016-12-01

    We study the effect of addition of BaZrO3 (BZO) on normal and superconducting state of YBa2Cu3O7-δ (YBCO). We find that in general both room temperature and residual resistivity increase with the addition of BZO except at low concentration of BZO. The temperature dependence of resistivity in presence of magnetic field also shows less resistivity broadening in composites containing low concentration of BZO below transition temperature (TC). The zero temperature upper critical field (Hc2(0)), estimated by using Werthamer, Helfand and Hohenberg theory and Ginzburg Landau theory, shows an increase by the finite addition of BZO in YBCO. Further, the activation energy (U0) determined from Arrhenius plots and vortex glass transition temperature (Tg) also increase with the limited addition of BZO. Such an enhancement in Hc2(0), Uo and Tg has been attributed to the increase in grain connectivity of YBCO . We conclude that the limited addition of BZO in YBCO significantly improves its superconducting performance in magnetic environment.

  1. Superconductivity:

    NASA Astrophysics Data System (ADS)

    Sacchetti, N.

    In this paper a short historical account of the discovery of superconductivity and of its gradual development is given. The physical interpretation of its various aspects took about forty years (from 1911 to 1957) to reach a successful description of this phenomenon in terms of a microscopic theory At the very end it seemed that more or less everything could be reasonably interpreted even if modifications and refinements of the original theory were necessary. In 1986 the situation changed abruptly when a cautious but revolutionary paper appeared showing that superconductivity was found in certain ceramic oxides at temperatures above those up to then known. A rush of frantic experimental activity started world-wide and in less than one year it was shown that superconductivity is a much more widespread phenomenon than deemed before and can be found at temperatures well above the liquid air boiling point. The complexity and the number of the substances (mainly ceramic oxides) involved call for a sort of modern alchemy if compounds with the best superconducting properties are to be manufactured. We don't use the word alchemy in a deprecatory sense but just to emphasise that till now nobody can say why these compounds are what they are: superconductors.

  2. Architecture for high critical current superconducting tapes

    DOEpatents

    Jia, Quanxi; Foltyn, Stephen R.

    2002-01-01

    Improvements in critical current capacity for superconducting film structures are disclosed and include the use of, e.g., multilayer YBCO structures where individual YBCO layers are separated by a layer of an insulating material such as CeO.sub.2 and the like, a layer of a conducting material such as strontium ruthenium oxide and the like or by a second superconducting material such as SmBCO and the like.

  3. On-line characterization of YBCO coated conductors using Raman spectroscopy methods.

    SciTech Connect

    Maroni, V. A.; Reeves, J. L.; Schwab, G.; Chemical Engineering; SuperPower, Inc.

    2007-04-01

    The use of Raman spectroscopy for on-line monitoring of the production of superconducting YBa2Cu3O6+X (YBCO) thin films on long-length metal tapes coated with textured buffer layers is reported for the first time. A methodology is described for obtaining Raman spectra of YBCO on moving tape exiting a metal-organic-chemical-vapor-deposition (MOCVD) enclosure. After baseline correction, the spectra recorded in this way show the expected phonons of the specific YBCO crystal orientation required for high supercurrent transport, as well as phonons of non-superconducting second-phase impurities when present. It is also possible to distinguish YBCO films that are properly textured from films having domains of misoriented YBCO grains. An investigation of the need for focus control on moving tape indicated that focusing of the laser on the surface of the highly reflective YBCO films exiting the MOCVD enclosure tends to produce aberrant photon bursts that swamp the Raman spectrum. These photon bursts are very likely a consequence of optical speckle effects induced by a combination of surface roughness, crystallographic texture, and/or local strain within the small grain microstructure of the YBCO film. Maintaining a slightly out-of-focus condition provides the best signal-to-noise ratio in terms of the obtained Raman spectra. In addition to examining moving tape at the post-MOCVD stage, Raman spectra of the film surface can also be recorded after the oxygen anneal performed to bring the YBCO to the optimum superconducting state. Consideration is given to data processing methods that could be adapted to the on-line Raman spectra to allow the tagging of out-of-specification tape segments and, at a more advanced level, feedback control to the MOCVD process.

  4. Calculations of superconducting parametric amplifiers performances

    NASA Astrophysics Data System (ADS)

    Goto, T.; Takeda, M.; Saito, S.; Shimakage, H.

    2017-07-01

    A superconducting parametric amplifier is an electromagnetic wave amplifier with high-quality characteristics such as a wide bandwidth, an extremely low noise, and a high dynamic range. In this paper, we report on the estimations of a YBCO superconducting parametric amplifier characteristic. The YBCO thin films were deposited on an MgO substrate by a pulsed laser deposition method. Based on the measured YBCO thin film parameters, theoretical calculations were implemented for evaluations of kinetic inductance nonlinearities and parametric gains. The nonlinearity of the YBCO thin film was estimated to be stronger than a single crystal NbTiN thin film. It is indicated that the YBCO parametric amplifier has a potential to be realized the amplifier with the high parametric gain. It is also expected that it could be operated in the range of the high frequency band, at the high temperature, and low applied current.

  5. Anisotropic structural and magnetic properties of the field-aligned superconducting system SmFeAsO1-xFx (x = 0, 0.1, 0.2, 0.25 and 0.3)

    NASA Astrophysics Data System (ADS)

    You, Y. B.; Hsiao, T. K.; Chang, B. C.; Tai, M. F.; Hsu, Y. Y.; Ku, H. C.; Wei, Z.; Ruan, K. Q.; Li, X. G.

    2011-01-01

    Anisotropic structural and magnetic properties of the field-aligned superconducting system SmFeAsO1-xFx (x = 0, 0.1, 0.2, 0.25 and 0.3) are reported. Due to the Fe spin-orbital related anisotropic exchange coupling, all the tetragonal microcrystalline powders in epoxy were aligned at room temperature using the field-rotation method where the tetragonal ab-plane is parallel to the magnetic alignment field Ba of 0.9 T and the c-axis parallels to the rotating axis. Anisotropic magnetic properties are studied through low temperature magnetic measurements along the c-axis and paralleled to the ab-plane of aligned samples in both zero-field-cooled (ZFC) and field-cooled (FC) modes. The under-doped compound (x = 0.1) is not superconducting with an antiferromagnetic Néel temperature TN ~ 40 K, while the two optimum-doped compounds (x = 0.2 and 0.25) show high superconducting transition temperatures Tc of 49K and 50K, respectively. The variation of anisotropic structural and magnetic properties for this system are discussed and compared with the previously reported 52 K anisotropic superconductor Sm0.95La0.05FeAsO0.85F0.15.

  6. Highly Anisotropic and Twofold Symmetric Superconducting Gap in Nematically Ordered FeSe_{0.93}S_{0.07}.

    PubMed

    Xu, H C; Niu, X H; Xu, D F; Jiang, J; Yao, Q; Chen, Q Y; Song, Q; Abdel-Hafiez, M; Chareev, D A; Vasiliev, A N; Wang, Q S; Wo, H L; Zhao, J; Peng, R; Feng, D L

    2016-10-07

    FeSe exhibits a novel ground state in which superconductivity coexists with a nematic order in the absence of any long-range magnetic order. Here, we report on an angle-resolved photoemission study on the superconducting gap structure in the nematic state of FeSe_{0.93}S_{0.07}, without the complications caused by Fermi surface reconstruction induced by magnetic order. We find that the superconducting gap shows a pronounced twofold anisotropy around the elliptical hole pocket near Z (0, 0, π), with gap minima at the end points of its major axis, while no detectable gap is observed around Γ (0, 0, 0) and the zone corner (π, π, k_{z}). The large anisotropy and nodal gap distribution demonstrate the substantial effects of the nematicity on the superconductivity and thus put strong constraints on current theories.

  7. Maximum permissible voltage of YBCO coated conductors

    NASA Astrophysics Data System (ADS)

    Wen, J.; Lin, B.; Sheng, J.; Xu, J.; Jin, Z.; Hong, Z.; Wang, D.; Zhou, H.; Shen, X.; Shen, C.

    2014-06-01

    Superconducting fault current limiter (SFCL) could reduce short circuit currents in electrical power system. One of the most important thing in developing SFCL is to find out the maximum permissible voltage of each limiting element. The maximum permissible voltage is defined as the maximum voltage per unit length at which the YBCO coated conductors (CC) do not suffer from critical current (Ic) degradation or burnout. In this research, the time of quenching process is changed and voltage is raised until the Ic degradation or burnout happens. YBCO coated conductors test in the experiment are from American superconductor (AMSC) and Shanghai Jiao Tong University (SJTU). Along with the quenching duration increasing, the maximum permissible voltage of CC decreases. When quenching duration is 100 ms, the maximum permissible of SJTU CC, 12 mm AMSC CC and 4 mm AMSC CC are 0.72 V/cm, 0.52 V/cm and 1.2 V/cm respectively. Based on the results of samples, the whole length of CCs used in the design of a SFCL can be determined.

  8. Anisotropic phase diagram and superconducting fluctuations of single-crystalline SmFeAsO0.85F0.15

    NASA Astrophysics Data System (ADS)

    Welp, U.; Chaparro, C.; Koshelev, A. E.; Kwok, W. K.; Rydh, A.; Zhigadlo, N. D.; Karpinski, J.; Weyeneth, S.

    2011-03-01

    We report on the specific-heat determination of the anisotropic phase diagram of single crystals of optimally doped SmFeAsO1-xFx. In zero field, we find a clear cusplike anomaly in C/T with ΔC/Tc=24 mJ/mol K2 at Tc=49.5 K. In magnetic fields along the c axis, pronounced superconducting fluctuations induce broadening and suppression of the specific-heat anomaly which can be described using three-dimensional lowest-Landau-level scaling with an upper critical field slope of -3.5 T/K and an anisotropy of Γ =8. The small value of ΔC/Tc yields a Sommerfeld coefficient γ ˜ 8 mJ/mol K2, indicating that SmFeAsO1-xFx is characterized by a modest density of states and strong coupling.

  9. Anisotropic superconducting gap in the spin-triplet superconductor Sr2RuO4: evidence from a Ru-NQR study

    PubMed

    Ishida; Mukuda; Kitaoka; Mao; Mori; Maeno

    2000-06-05

    We have investigated a gap structure in the spin-triplet superconductor Sr2RuO4 through the measurement of the 101Ru nuclear spin-lattice relaxation rate (101)(1/T1) down to 0.09 K at zero magnetic field. In the superconducting state, 1/T1 in a high-quality sample with T(c) approximately 1.5 K exhibits a sharp decrease without the coherence peak, followed by a T3 behavior down to 0.15 K. This result is in marked contrast to the behavior observed below approximately 0.4 K in samples with lower T(c), where T1T is a constant. This behavior is demonstrated to be not intrinsic. We conclude that the gap structure in Sr2RuO4 is significantly anisotropic, consistent with line-node-like models.

  10. YBCO and LSMO nano-films and sandwiches prepared by magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Nurgaliev, T.; Mateev, E.; Blagoev, B.; Miteva, S.; Neshkov, L.; Strbik, V.; Uspenskaya, L. S.; Benacka, S.; Chromik, S.; Nedkov, I.

    2010-06-01

    DC and RF magnetron sputtering techniques were used for growing nano-films (t<100 nm) of high temperature superconducting (HTS) YBa2Cu3O7 (YBCO) and ferromagnetic (FM) manganite La0.7Sr0.3Mn03 (LSMO) materials on LaAlO3 (LAO) and Al2O3 (ALO) substrates as well as for preparing of single-, double- and three-layer structures in different areas of the same substrates. The procedure allowed growing of structures on LAO substrates where the critical temperature of YBCO thin film components was more than 84 K. The LSMO films grown ALO substrates were ferromagnetic while the YBCO films grown on LSMO/ALO did not demonstrate superconductivity.

  11. Anisotropic superconducting and normal state magnetic properties of single crystals of RNi*2*B*2*C compounds (R = Y, Gd, Dy, Ho, Er, and Tm)

    SciTech Connect

    Cho, Beongki

    1995-09-26

    The interaction of superconductivity with magnetism has been one of the most interesting and important phenomena in solid state physics since the 1950`s when small amounts of magnetic impurities were incorporated in superconductors. The discovery of the magnetic superconductors RNi2B2C (R = rare earth, Y) offers a new system to study this interaction. The wide ranges of superconducting transition (Tc) and antiferromagnetic (AF) ordering temperatures (TN) (0 K ≤ Tc ≤ 16 K, 0 K ≤ TN ≤ 20 K) give a good opportunity to observe a variety of interesting phenomena. Single crystals of high quality with appropriate size and mass are crucial in examining the anisotropic intrinsic properties. Single crystals have been grown successfully by an unusual high temperature flux method and characterized thoroughly by X-ray, electrical transport, magnetization, neutron scattering, scanning electron microscopy, and other measurements.

  12. Improvement of spatial homogeneity in IBAD based YBCO coated conductors

    NASA Astrophysics Data System (ADS)

    Zulkifli, Z.; Kiss, T.; Inoue, M.; Enpuku, K.; Kashima, N.; Watanabe, T.; Mori, M.; Nagaya, S.; Ibi, A.; Miyata, S.; Yamada, Y.; Shiohara, Y.

    2008-09-01

    Prior to the development of fabrication technique for the chemical vapor deposited (CVD) YBa 2Cu 3O 7-δ coated conductor on a IBAD-Gd 2Zr 2O 7, investigations on the improvement of spatial homogeneity have been done. By using spatially resolved measurements and combined multiple microanalysis techniques with length scale of several μm, physical and transport properties of the CVD samples have been investigated before and after fabrication modification. Structural inhomogeneity was visualized using thermoelectric voltage imaging (TVI) technique using a laser scanning microscope. Laser scanning microscopy at superconducting temperature is used to visualize flux flow dissipation; furthermore, mappings of 2D local current flow density distribution have been done using a scanning SQUID microscopy. It has been shown that the superconducting layer consisted of YBCO matrix with localized defects originating from the buffer layer. This led to current non-uniformity and caused high flux flow dissipation within the vicinity of the defects. Process conditions have been modified effectively based on those insights. After fabrication modification, our measurement analyses shows that the texturing of the YBCO layer improved significantly and the appearance of spatially distributed obstacles that are responsible for non-uniform current distribution and localized dissipation are reduced. Our complementing, quick yet non-invasive technique not only can quantify the improvement of YBCO homogeneity but also shed light on the basic understanding of the current limiting mechanism in the IBAD based coated conductors.

  13. YBCO step-edge junctions with high IcRn

    NASA Astrophysics Data System (ADS)

    Mitchell, E. E.; Foley, C. P.

    2010-06-01

    Step-edge junctions represent one type of grain boundary Josephson junction employed in high-temperature superconducting junction technology. To date, the majority of results published in the literature focus on [001]-tilt grain boundary junctions (GBJs) produced using bicrystal substrates. We investigate the step morphology and YBCO (yttrium barium copper oxide) film structure of YBCO-based step-edge junctions on MgO [001] substrates which structurally resemble [100]-tilt junctions. High-resolution electron microscopy reveals a clean GBJ interface of width ~ 1 nm and a single junction at the top edge. The dependence of the transport properties on the MgO step-edge and junction morphology is examined at 4.2 K, to enable direct comparison with results for other junction studies such as [001]-tilt and [100]-tilt junctions and building on previously published 77 K data. MgO step-edge junctions show a slower reduction in critical current density with step angle compared with [001]-tilt junctions. For optimized step parameters, transport measurements revealed large critical current and normal resistance (IcRN) products (~3-5 mV), comparable with the best results obtained in other kinds of [100]-tilt GBJs in YBCO at 4.2 K. Junction-based devices such as SQUIDs (superconducting quantum interference devices) and THz imagers show excellent performance when MgO-based step-edge junctions are used.

  14. Origin of photovoltaic effect in superconducting YBa2Cu3O6.96 ceramics

    PubMed Central

    Yang, F.; Han, M. Y.; Chang, F. G.

    2015-01-01

    We report remarkable photovoltaic effect in YBa2Cu3O6.96 (YBCO) ceramic between 50 and 300 K induced by blue-laser illumination, which is directly related to the superconductivity of YBCO and the YBCO-metallic electrode interface. There is a polarity reversal for the open circuit voltage Voc and short circuit current Isc when YBCO undergoes a transition from superconducting to resistive state. We show that there exists an electrical potential across the superconductor-normal metal interface, which provides the separation force for the photo-induced electron-hole pairs. This interface potential directs from YBCO to the metal electrode when YBCO is superconducting and switches to the opposite direction when YBCO becomes nonsuperconducting. The origin of the potential may be readily associated with the proximity effect at metal-superconductor interface when YBCO is superconducting and its value is estimated to be ~10–8 mV at 50 K with a laser intensity of 502 mW/cm2. Combination of a p-type material YBCO at normal state with an n-type material Ag-paste forms a quasi-pn junction which is responsible for the photovoltaic behavior of YBCO ceramics at high temperatures. Our findings may pave the way to new applications of photon-electronic devices and shed further light on the proximity effect at the superconductor-metal interface. PMID:26099727

  15. Origin of photovoltaic effect in superconducting YBa2Cu3O6.96 ceramics.

    PubMed

    Yang, F; Han, M Y; Chang, F G

    2015-06-23

    We report remarkable photovoltaic effect in YBa2Cu3O6.96 (YBCO) ceramic between 50 and 300 K induced by blue-laser illumination, which is directly related to the superconductivity of YBCO and the YBCO-metallic electrode interface. There is a polarity reversal for the open circuit voltage Voc and short circuit current Isc when YBCO undergoes a transition from superconducting to resistive state. We show that there exists an electrical potential across the superconductor-normal metal interface, which provides the separation force for the photo-induced electron-hole pairs. This interface potential directs from YBCO to the metal electrode when YBCO is superconducting and switches to the opposite direction when YBCO becomes nonsuperconducting. The origin of the potential may be readily associated with the proximity effect at metal-superconductor interface when YBCO is superconducting and its value is estimated to be ~10(-8) mV at 50 K with a laser intensity of 502 mW/cm(2). Combination of a p-type material YBCO at normal state with an n-type material Ag-paste forms a quasi-pn junction which is responsible for the photovoltaic behavior of YBCO ceramics at high temperatures. Our findings may pave the way to new applications of photon-electronic devices and shed further light on the proximity effect at the superconductor-metal interface.

  16. Bipolar electrical coil based on YBCO bulks: initial tests

    NASA Astrophysics Data System (ADS)

    Alvarez, A.; Suárez, P.; Ceballos, J. M.; Pérez, B.; Werfel, F.; Floegel-Delor, U.

    2008-02-01

    In the field of the application of HTS in electrical motors, most prototypes are made using superconducting coils based on tape and located in the position where copper coils work in a similar conventional motor. Other prototypes use superconducting bulks (usually disk-shaped) in those positions where normal magnets should work in similar conventional motors. But it is very unusual to find designs using electrical coils based on bulks. This is a challenge whose main problem is the difficulty in machining the superconductor bulks to get the proper shape because of the impossibility of bending the material to wind coils. The design of a bipolar single-turn coil made from a superconducting YBCO disk was proposed by the group of Electrical Application of Superconductors, at the University of Extremadura, several years ago to be an element for the design of a modular two-phase inductor for an air core axial-flux motor. The shape of each coil looks like an 'S'. When a current flows through the circuit, two opposite magnetic fields appear in the upper and lower halves of the piece. Until now, attempts to get a good superconducting circuit by cutting a YBCO disk into the required shape have failed because of cracks appearing in the crystal during the process. Last year, our group at the University of Extremadura began to work with ATZ GmbH who have improved the machining process and made the coils. In this paper we present the coil and the first tests carried out.

  17. Enhanced pinning in YBCO films with BaZrO.sub.3 nanoparticles

    DOEpatents

    Driscoll, Judith L.; Foltyn, Stephen R.

    2010-06-15

    A process and composition of matter are provided and involve flux pinning in thin films of high temperature superconductive oxides such as YBCO by inclusion of particles including barium and a group 4 or group 5 metal, such as zirconium, in the thin film.

  18. Superconductivity in Cuprate Superlattices

    NASA Astrophysics Data System (ADS)

    Bozovic, Ivan; Eckstein, J. N.

    The following sections are included: * Introduction * YBCO/DBCO superlattices: the commencement * YBCO/PBCO superlattices: conjectures * Bi-2212:2201 superlattices: Q2D superconductivity * YBCO/(Pr,Y,Ca)BCO superlattices: clarification * More Bi-2212 superlattices: afterthoughts * Positive proximity effect in Dy-doped 2212 * Long-range proximity effect in 2201 * HTS in one-unit-cell thick 2212 layer * Inelastic hopping via localized states * Materials and layering * Integrity of ultrathin layers * Thickness dependence of the barrier resistance * Temperature dependence of the barrier resistance * Voltage dependence of current through the barrier * Interpretation: multiple inelastic hopping * Negative proximity effect on 2212 * Interlayer coupling in HTS superlattices: conclusions * The science and technology of HTS superlattices * Vortex dynamics * Critical current scaling law * Thermal activation of vortex motion * Superlattice phonons * Atomic-layer engineering of artificial HTS materials * Technological applications of HTS superlattices * Summary * Intercell coupling in HTS superlattices * Vortex dynamics * Phonon spectra * Atomic-layer engineering of artificial HTS materials * Applications * Acknowledgments * References

  19. Over-current carrying characteristics of rectangular-shaped YBCO thin films prepared by MOD method

    NASA Astrophysics Data System (ADS)

    Hotta, N.; Yokomizu, Y.; Iioka, D.; Matsumura, T.; Kumagai, T.; Yamasaki, H.; Shibuya, M.; Nitta, T.

    2008-02-01

    A fault current limiter (FCL) may be manufactured at competitive qualities and prices by using rectangular-shaped YBCO films which are prepared by metal-organic deposition (MOD) method, because the MOD method can produce large size elements with a low-cost and non-vacuum technique. Prior to constructing a superconducting FCL (SFCL), AC over-current carrying experiments were conducted for 120 mm long elements where YBCO thin film of about 200 nm in thickness was coated on sapphire substrate with cerium oxide (CeO2) interlayer. In the experiments, only single cycle of the ac damping current of 50 Hz was applied to the pure YBCO element without protective metal coating or parallel resistor and the magnitude of the current was increased step by step until the breakdown phenomena occurred in the element. In each experiment, current waveforms flowing through the YBCO element and voltage waveform across the element were measured to get the voltage-current characteristics. The allowable over-current and generated voltage were successfully estimated for the pure YBCO films. It can be pointed out that the lower n-value trends to bring about the higher allowable over-current and the higher withstand voltage more than tens of volts. The YBCO film having higher n-value is sensitive to the over-current. Thus, some protective methods such as a metal coating should be employed for applying to the fault current limiter.

  20. Magnetron sputtering of Fe-oxides on the top of HTS YBCO films

    NASA Astrophysics Data System (ADS)

    Nurgaliev, T.; Blagoev, B.; Buchkov, K.; Mateev, E.; Gajda, G.; Nedkov, I.; Kovacheva, D.; Slavov, L.; Starbova, I.; Starbov, N.; Nankovski, M.

    2017-05-01

    The possibilities for preparation of bilayers containing magnetic Fe-oxide (Fe-O) and high temperature superconducting (HTS) YBa2Cu3O7-x (YBCO) thin films were investigated. For this purpose, Fe-O films were deposited using reactive magnetron sputtering at comparatively low temperatures T≤250 °C onto dielectric (for example, LaAlO3 (LAO)) substrates, covered with a HTS YBCO film. The sputtering of the Fe-O layer at such conditions did not lead to a crucial damage of the critical temperature TC of the YBCO film, but could affect the width of the superconducting transition. A decrease of the critical temperature of the (Fe-O)/YBCO/LAO bilayer kept at ambient conditions was observed, possibly due to the negative effects of the water vapour on the sample characteristics. The double peak structure of the imaginary component of the response signal to the AC harmonic magnetic field, observed in such a (Fe-O)/YBCO/LAO sample, was ascribed from two possible views: as a consequence of morphology determined inter- and intra-granular contributions and/or as transitions from dominant irreversible processes as Bean-Livingston barrier to vortex state chains formation.

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

    NASA Technical Reports Server (NTRS)

    Wu, M. K.

    1987-01-01

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

  2. Fiber optic quench detection via optimized Rayleigh Scattering in high-field YBCO accelerator magnets

    SciTech Connect

    Flanagan, Gene

    2016-02-17

    Yttrium barium copper oxide (YBCO) coated conductors are known for their ability to operate in the superconducting state at relatively high temperatures, even above the boiling point of liquid nitrogen (77 K). When these same conductors are operated at lower temperatures, they are able to operate in much higher magnetic fields than traditional superconductors like NiTi or Nb3Sn. Thus, YBCO superconducting magnets are one of the primary options for generating the high magnetic fields needed for future high energy physics devices. Due to slow quench propagation, quench detection remains one of the primary limitations to YBCO magnets. Fiber optic sensing, based upon Rayleigh scattering, has the potential for spatial resolution approaching the wavelength of light, or very fast temporal resolution at low spatial resolution, and a continuum of combinations in between. This project has studied, theoretically and experimentally, YBCO magnets and Rayleigh scattering quench detection systems to demonstrate feasibility of the systems for YBCO quench protection systems. Under this grant an experimentally validated 3D quench propagation model was used to accurately define the acceptable range of spatial and temporal resolutions for effective quench detection in YBCO magnets and to evaluate present-day and potentially improved YBCO conductors. The data volume and speed requirements for quench detection via Rayleigh scattering required the development of a high performance fiber optic based quench detection/data acquisition system and its integration with an existing voltage tap/thermo-couple based system. In this project, optical fibers are tightly co-wound into YBCO magnet coils, with the fiber on top of the conductor as turn-to-turn insulation. Local changes in the temperature or strain of the conductor are sensed by the optical fiber, which is in close thermal and mechanical contact with the conductor. Intrinsic imperfections in the fiber reflect Rayleigh

  3. Anisotropic Superconducting Gap Revealed by Angle Resolved Specific Heat, Point Contact Tunneling and Scanning Tunneling Microscope in Iron Pnictide Superconductors

    NASA Astrophysics Data System (ADS)

    Wen, Hai-Hu

    2011-03-01

    Angle resolved specific heat was measured in FeSe 0.55 Te 0.45 single crystals. A four-fold oscillation of C/T, with the minimum locating at the Fe-Fe bond direction, was observed when the sample was rotated at 9 T, which can be understood as due to the gap modulation on the electron pocket within the scheme of S +/- pairing. Accordingly, by measuring the point contact Andreev reflection spectrum on the BaFe 2-x Ni x As 2 single crystals in wide doping regimes, we found a crossover from nodeless to nodal feature of the superconducting gap. In K-doped BaFe 2 As 2 single crystals, we performed the low temperature STM measurements and observed a well ordered vortex lattice in local region. In addition, the statistics on over 3000 dI/dV spectra illustrate clear evidence of two gaps with magnitude of 7.6 meV and 3.3 meV, respectively. Detailed fitting to the tunneling spectrum shows an isotropic superconducting gap. Work collaborated with B. Zeng, C. Ren, L. Shan, Y. L. Wang, B. Shen, G. Mu, H. Q. Luo, T. Xiang, H. Yang, I. I. Mazin and P. C. Dai. This work was supported by the Natural Science Foundation of China, the Ministry of Science and Technology of China (2011CB605900, No. 2006CB921802), and Chinese Academy of Sciences. IIM was supported by the Office of the Naval Research.

  4. Origin of the anisotropic upper critical fields in single crystals of superconducting rare-earth ternary borides

    SciTech Connect

    Shenoy, G.K.; Malik, S.K.

    1986-05-01

    Upper-critical-field (H/sub c/2(T)) measurements in single-crystal ErRh/sub 4/B/sub 4/ have revealed a large anisotropy. We show that this anisotropy is a consequence of the crystalline electric fields (CEF's) acting on the Er/sup 3 +/ ion which make the exchange field acting on the conduction electrons anisotropic. A full calculation based on Werthamer-Helfand-Hohenberg theory with the inclusion of CEF's completely explains the observed anisotropy in H/sub c/2(T) for ErRh/sub 4/B/sub 4/. In addition, the critical-field measurements in ErRh/sub 4/B/sub 4/ provide a means for the reliable determination of the magnitude and the sign of the exchange constant J/sub s/f.

  5. Application of melt-textured YBCO to electromagnetic launchers

    NASA Astrophysics Data System (ADS)

    Putman, P. T.; Zhou, Y. X.; Fang, H.; Klawitter, A.; Salama, K.

    2005-02-01

    Melt-textured YBCO superconductors are capable of carrying higher current densities than comparable copper conductors, and can therefore be used in electromechanical devices requiring high power densities. The advantage of textured YBCO superconductors is most pronounced in large systems such as electromagnetic launchers for aircraft carriers. In general, an electromagnetic launcher consists of a series of stationary pulsed electromagnets (the primary), which attract and/or repel a carriage carrying one or more magnets (the secondary). Several possibilities exist for the incorporation of HTSs into EM launchers, with the most direct being upgrading the magnets in the secondary to melt-textured YBCO. A system was developed to study propulsive force in a coaxial-type launcher. Results from this study are presented and their implications for launcher development discussed. A second type of launcher was also studied, with a power supply integrated into the launcher primary, so that the primary serves as a superconducting magnetic energy storage system. A method of optimizing energy conversion in a system of this type has been found. The time dependence of the magnetic field in this type of launcher is presented.

  6. Granular superconductivity and magnetic-field-driven recovery of macroscopic coherence in a cuprate/manganite multilayer

    NASA Astrophysics Data System (ADS)

    Mallett, B. P. P.; Khmaladze, J.; Marsik, P.; Perret, E.; Cerreta, A.; Orlita, M.; Biškup, N.; Varela, M.; Bernhard, C.

    2016-11-01

    We show that in Pr0.5La0.2Ca0.3MnO3 /YBa2Cu3O7 (PLCMO/YBCO) multilayers the low temperature state of YBCO is very resistive and resembles that of a granular superconductor or a frustrated Josephson-junction network. Notably, a coherent superconducting response can be restored with a large magnetic field which also suppresses the charge-orbital order in PLCMO. This coincidence suggests that the granular superconducting state of YBCO is induced by the charge-orbital order of PLCMO. The coupling mechanism and the nature of the induced inhomogeneous state in YBCO remain to be understood.

  7. Magnetic coupling by using levitation characteristics of YBCO superconductors

    NASA Astrophysics Data System (ADS)

    Ishigaki, H.; Ito, H.; Itoh, M.; Hida, A.; Takahata, R.

    1993-03-01

    A mechanical system which uses high lateral restoring forces of high-Tc materials as the driving force for a magnetic coupling is proposed. As the basic study of the superconducting magnetic coupling, the relationship between the lateral restoring force and levitation force, transmitted torque characteristics as a function of a twisting angle and clearance, and damping characteristics of the coupling were examined. Superiorities of the coupling such as high damping coefficients and high stability against time and twisting angle were revealed. A magnetic force sensor system was used to evaluate the superconducting characteristics of materials, and nonuniform distribution of repulsive force was observed for the YBCO pellet fabricated by the melt-powder-melt-growth process. The improvement of the homogeneity was achieved by compensating for the composition rate which had changed during the quenching process.

  8. Properties of biaxially oriented Y 2O 3 based buffer layers deposited on cube textured non-magnetic Ni-V substrates for YBCO coated conductors

    NASA Astrophysics Data System (ADS)

    Fabbri, F.; Annino, C.; Boffa, V.; Celentano, G.; Ciontea, L.; Gambardella, U.; Grimaldi, G.; Mancini, A.; Petrisor, T.

    A study regarding the epitaxial growth of Y 2O 3-based buffer layer architectures on (001)[100] textured Ni-V metallic substrates using both PLD and e-beam evaporation is presented. The as deposited films exhibit good structural and morphological properties indicating that the Y 2O 3 is a suitable layer for epitaxial growth of YBCO superconducting films for power applications. Mainly, YBCO/CeO 2/Y 2O 3/Ni-V and YBCO/CeO 2/Y 2O 3/NiO/Ni-V architectures have been studied.

  9. Magnetic granularity in pulsed laser deposited YBCO films on technical templates at 5 K

    NASA Astrophysics Data System (ADS)

    Lao, M.; Hecher, J.; Pahlke, P.; Sieger, M.; Hühne, R.; Eisterer, M.

    2017-10-01

    The manifestation of granularity in the superconducting properties of pulsed laser deposited YBCO films on commercially available metallic templates was investigated by scanning Hall probe microscopy at 5 K and was related to local orientation mapping of the YBCO layer. The YBCO films on stainless steel templates with a textured buffer layer of yttrium stabilized ZrO2 grown by alternating beam assisted deposition have a mean grain size of less than 1 μ {{m}} with a sharp texture. This results in a homogeneous trapped field profile and spatial distribution of the current density. On the other hand, YBCO films on biaxially textured NiW substrates show magnetic granularity that persists down to a temperature of 5 K and up to an applied magnetic field of 4 T. The origin of the granular field profile is directly correlated to the microstructural properties of the YBCO layer adopted from the granular NiW substrate which leads to a spatially inhomogeneous current density. Grain-to-grain in-plane tilts lead to grain boundaries that obstruct the current while out-of-plane tilts mainly affect the grain properties, resulting in areas with low {J}{{c}}. Hence, not all grain boundaries cause detrimental effects on {J}{{c}} since the orientation of individual NiW grains also contributes to observed inhomogeneity and granularity.

  10. Effects of deposition conditions on the phase formation of YBCO films prepared by spray pyrolysis method

    NASA Astrophysics Data System (ADS)

    Kim, Ho-Jin; Joo, Jinho; Park, Shin-Geun; Hong, Suck-Kwan; Lee, Sun-Wang; Lim, Sun-Weon; Hong, Gye-Won; Lee, Hee-Gyoun

    2006-10-01

    YBa2Cu3Oy superconducting films were deposited on LaAlO3(1 0 0) single crystal substrates by spray pyrolysis method. Two types of ultrasonic and concentric nebulizer were used in order to generate fine droplets of metal-inorganic precursor solution. c-Axis oriented films were obtained at deposition temperature of 750-850 °C and at working pressures of 100 Torr and 500 Torr. In case of ultrasonic nebulizer, the films showed rough surface morphology due to the presence of enormous droplets, whereas smooth and dense films were obtained for concentric nebulizer. The good c-axis oriented YBCO films were formed at the wide range of the oxygen partial pressure. Oxygen which is generated via the decomposition of nitrate precursors is considered to participate in the formation reaction of YBCO film. Microstructures of YBCO films varied depending on oxygen partial pressure and rod-like grains were appeared when the oxygen partial pressure was lower than 30 Torr. YBCO films were deposited epitaxially on LAO(1 0 0) substrate. Δϕ of in-plane and Δω of out-of-plane texture were measured as 3.3° and 1.0°, respectively. A transport Jc value of 0.50 MA/cm2 at 77 K and self-field was achieved for the YBCO film deposited on LaAlO3(1 0 0) single crystal substrate.

  11. A YBCO RF-SQUID magnetometer and its applications

    NASA Technical Reports Server (NTRS)

    Luwei, Zhou; Jingwu, Qiu; Xienfeng, Zhang; Zhiming, Tank; Yongjia, Qian

    1990-01-01

    An applicable RF-superconducting quantum interference detector (SQUID) magnetometer was made using a bulk sintered yttrium barium copper oxide (YBCO). The temperature range of the magnetometer is 77 to 300 K and the field range 0 to 0.1T. At 77 K, the equivalent flux noise of the SQUID is 5 x 10 to minus 4 power theta sub o/square root of Hz at the frequency range of 20 to 200 Hz. The experiments show that the SQUID noise at low-frequency end is mainly from 1/f noise. A coil test shows that the magnetic moment sensitivity delta m is 10 to the minus 6th power emu. The RF-SQUID is shielded in a YBCO cylinder with a shielding ability B sub in/B sub ex of about 10 to the minus 6th power when external dc magnetic field is about a few Oe. The magnetometer is successfully used in characterizing superconducting thin films.

  12. In-situ sputtering of YBCO films for microwave applications

    NASA Technical Reports Server (NTRS)

    Ballentine, P. H.; Kadin, A. M.; Mallory, D. S.

    1991-01-01

    RF magnetron sputtering from a single YBCO target onto a heated substrate (700 C) was used to obtain c-axis-oriented 1-2-3 films that are superconducting without a subsequent annealing or oxygenation step, with Tc(R = 0) as high as 88 K on MgO and LaAlO3 substrates. This process uses an 8-in-diameter target in the sputter-up configuration, with a central grounded shield to eliminate negative ion bombardment. It can reproducibly and uniformly cover substrates as large as 3-in across at rates exceeding 1 A/s. Maintaining film composition very close to stoichiometry is essential for obtaining films with good superconducting properties and surface morphology. Optimum films have critical currents of 1 MA/sq cm at 77 K. Measurements of microwave surface resistance based on a stripline resonator indicate low surface resistance for unpatterned YBCO ground planes, but excess loss and a strong power dependence in a patterned center strip.

  13. Novel Superoxygenated Phases in Superconducting Cuprate Thin Films

    NASA Astrophysics Data System (ADS)

    Zhang, C.; Zhang, H.; Gauquelin, N.; Botton, G. A.; McMahon, C.; Hawthorn, D. G.; Wei, J. Y. T.

    The superconducting critical temperature (Tc) of hole-doped cuprates tends to increase with their lattice complexity, which is generally correlated with higher states of oxidation. For YBa2Cu3O7 - δ (YBCO-123), it is known that solid-state reaction in high-pressure oxygen can induce the formation of more complex and oxidized phases such as Y2Ba4Cu7O15 - δ (YBCO-247) and Y2Ba4Cu8O16 (YBCO-248). In this work, we apply this superoxygenation concept of material synthesis to nanoscale thin films which, owing to their large surface-to-volume ratio, are more thermodynamically reactive than bulk samples. Epitaxial thin films of YBCO-123 were grown by pulsed laser deposition on (La , Sr) (Al , Ta) O3 substrates, and post-annealed in up to 500 atm of oxygen at 800C. Our post-annealed films show robust superconducting transitions with Tc ranging from 80 to 93K. Transmission electron microscopy and X-ray absorption spectroscopy were used to probe the lattice structure and oxygen stoichiometry. Our measurements show clear evidence of conversion to YBCO-247 and YBCO-248 in the superoxygenated films, as well as YBCO-125, a novel YBCO phase that has three CuO chains per unit cell and potentially higher Tc. Work supported by NSERC, CFI/OIT, and CIFAR.

  14. Superconducting optical modulator

    NASA Astrophysics Data System (ADS)

    Bunt, Patricia S.; Ference, Thomas G.; Puzey, Kenneth A.; Tanner, David B.; Tache, Nacira; Varhue, Walter J.

    2000-12-01

    An optical modulator based on the physical properties of high temperature superconductors has been fabricated and tested. The modulator was constructed form a film of Yttrium Barium Copper Oxide (YBCO) grown on undoped silicon with a buffer layer of Yttria Stabilized Zirconia. Standard lithographic procedures were used to pattern the superconducting film into a micro bridge. Optical modulation was achieved by passing IR light through the composite structure normal to the micro bridge and switching the superconducting film in the bridge region between the superconducting and non-superconducting states. In the superconducting state, IR light reflects from the superconducting film surface. When a critical current is passed through the micro bridge, it causes the film in this region to switch to the non-superconducting state allowing IR light to pass through it. Superconducting materials have the potential to switch between these two states at speeds up to 1 picosecond using electrical current. Presently, fiber optic transmission capacity is limited by the rate at which optical data can be modulated. The superconducting modulator, when combined with other components, may have the potential to increase the transmission capacity of fiber optic lines.

  15. Superconducting Materials, Magnets and Electric Power Applications

    NASA Astrophysics Data System (ADS)

    Crabtree, George

    2011-03-01

    The surprising discovery of superconductivity a century ago launched a chain of convention-shattering innovations and discoveries in superconducting materials and applications that continues to this day. The range of large-scale applications grows with new materials discoveries - low temperature NbTi and Nb3 Sn for liquid helium cooled superconducting magnets, intermediate temperature MgB2 for inexpensive cryocooled applications including MRI magnets, and high temperature YBCO and BSSCO for high current applications cooled with inexpensive liquid nitrogen. Applications based on YBCO address critical emerging challenges for the electricity grid, including high capacity superconducting cables to distribute power in urban areas; transmission of renewable electricity over long distances from source to load; high capacity DC interconnections among the three US grids; fast, self-healing fault current limiters to increase reliability; low-weight, high capacity generators enabling off-shore wind turbines; and superconducting magnetic energy storage for smoothing the variability of renewable sources. In addition to these grid applications, coated conductors based on YBCO deposited on strong Hastelloy substrates enable a new generation of all superconducting high field magnets capable of producing fields above 30 T, approximately 50% higher than the existing all superconducting limit based on Nb3 Sn . The high fields, low power cost and the quiet electromagnetic and mechanical operation of such magnets could change the character of high field basic research on materials, enable a new generation of high-energy colliding beam experiments and extend the reach of high density superconducting magnetic energy storage.

  16. Modern superconductive materials for electrical machines and devices working on the principle of levitation

    NASA Astrophysics Data System (ADS)

    Prikhna, T. A.

    2006-04-01

    The peculiarities of high-pressure synthesis of highly dense nanostructural MgB2-based superconductive materials, of thermobaric treatment of MT-YBCO (melt-textured YBa2Cu3O7-δ-based superconductor), high-pressure sintering of YBa2Cu3O7-δ, oxygenation of MT-YBCO under high isostatic pressure of oxygen and processes of formation of superconductive junctions between MT-YBCO blocks are considered. The attained level of superconductive and mechanical properties of such materials and junctions make them promising for application in cryogenic devices working on the principle of levitation: electric motors, generators, pumps for liquid-gas transfer, magnetic bearings, flywheels, fault-current limiters, maglev transport, etc. High-pressure synthesized MgB2 (with Ti additions) blocks were for the first time tried in the superconductive electric motor at 20K and demonstrated an efficiency similar to MT-YBCO (at the same working temperature).

  17. Flux pinning by Al-based nanoparticles embedded in YBCO: A transmission electron microscopic study

    NASA Astrophysics Data System (ADS)

    Ben Azzouz, F.; Zouaoui, M.; Mellekh, A.; Annabi, M.; Van Tendeloo, G.; Ben Salem, M.

    2007-05-01

    A series of YBa2Cu3Oy (YBCO) samples with small amounts (0-0.6 wt.%) of nanosized alumina particles (50 nm) are synthesized in air by solid state reaction. The microstructure has been characterized by transmission electron microscopy (TEM) and the critical current density Jc has been measured by the standard four-probe method in the applied magnetic field at 77 K. TEM and energy dispersive X-ray spectroscopy (EDS) analysis have shown that alumina reacts with the YBCO matrix to form nanometric aluminium-rich inhomogeneities intergrown within the YBCO superconducting matrix. These inhomogeneities reduce the onset transition temperature Tconset and the zero resistance temperature Tc. In spite of the monotonic decrease of the superconducting temperature Tc with increasing alumina addition, the Jc(H) behaviour is remarkably improved. The characteristic behaviour of Jc can be explained in terms of the counterbalance of two effects simultaneously caused by the nanometric alumina addition in the system. One effect is the formation of the Al-rich nanometric inhomogeneities relevant for the flux pinning, and the other effect is the reduction of matrix superconducting volume, which is reflected by a decrease of the critical current density Jc at zero applied magnetic field.

  18. Magnetic suspension using high temperature superconducting cores

    NASA Technical Reports Server (NTRS)

    Scurlock, R. G.

    1992-01-01

    The development of YBCO high temperature superconductors, in wire and tape forms, is rapidly approaching the point where the bulk transport current density j vs magnetic field H characteristics with liquid nitrogen cooling will enable its use in model cores. On the other hand, BSCCO high temperature superconductor in wire form has poor j-H characteristics at 77 K today, although with liquid helium or hydrogen cooling, it appears to be superior to NbTi superconductor. Since liquid nitrogen cooling is approx. 100 times cheaper than liquid helium cooling, the use of YBCO is very attractive for use in magnetic suspension. The design is discussed of a model core to accommodate lift and drag loads up to 6000 and 3000 N respectively. A comparison is made between the design performance of a liquid helium cooled NbTi (or BSCCO) superconducting core and a liquid nitrogen cooled YBCO superconducting core.

  19. Finite-Element Simulations of Field and Current Distributions in Multifilamentary Superconducting Films (Postprint)

    DTIC Science & Technology

    2010-03-01

    coupling and ac losses. 15. SUBJECT TERMS superconductivity, flux pinning, critical current density, magnetic field, YBa2Cu3O7‒z or YBCO , finite...the ends. The dimensions chosen for the system correspond to YBa2Cu3O7−x ( YBCO ) thin films grown by pulsed laser deposition on a LaAlO3 or SrTiO3...1000 Hz. For the superconducting material, we choose Jc = 3 × 1011 A m−2, Ec = 10−4 V m−1 and n = 25 Figure 1. Example of filamentary YBCO thin film

  20. Emergence of Dissipative Structures in Current-Carrying Superconducting Wires (Postprint)

    DTIC Science & Technology

    2009-05-26

    will discuss the transition from superconducting to normal mode of operation in the state-of-the art YBa2Cu3O7−x YBCO coated conductors 2,3. The...main advantage of YBCO coated conductors over conventional low temperature superconducting wires—high operating temperature 65–77 K—has an...very thin a fraction of a micron layer of material between the YBCO and copper that accounts for the resis- tance to the current exchange 4,5

  1. Time-frequency Analyses of AE Signals in YBCO Superconductors

    NASA Astrophysics Data System (ADS)

    Nanato, N.; Takemoto, N.

    AE (Acoustic Emission) measurements are well known methods to detect mechanical signals from superconducting coil The mechanical signals could be generated by micro cracks of epoxy resins, the motion of superconductors and the thermal expansion of superconductors, which were generated before and/or after a quench. We have presented a time-frequency visualization of AE signals as a method to detect the quench. We can detect very small AE signals regardless of lectromagnetic noises and can find the time of the AE occurrence and the frequency bands of AE signals by using this method. Recently it has been presented that YBCO superconductors are delaminated and degraded by a transverse tensile stress. The delamination is accompanied with AE signals. Also, it is known that amplitudes and frequency bands of AE signals vary with causes of AE occurrence. In this paper, we present time-frequency analyses of AE signa s caused by the delamination of a YBCO superconductor and the micro of epoxy resins.

  2. Research on resistance characteristics of YBCO tape under short-time DC large current impact

    NASA Astrophysics Data System (ADS)

    Zhang, Zhifeng; Yang, Jiabin; Qiu, Qingquan; Zhang, Guomin; Lin, Liangzhen

    2017-06-01

    Research of the resistance characteristics of YBCO tape under short-time DC large current impact is the foundation of the developing DC superconducting fault current limiter (SFCL) for voltage source converter-based high voltage direct current system (VSC-HVDC), which is one of the valid approaches to solve the problems of renewable energy integration. SFCL can limit DC short-circuit and enhance the interrupting capabilities of DC circuit breakers. In this paper, under short-time DC large current impacts, the resistance features of naked tape of YBCO tape are studied to find the resistance - temperature change rule and the maximum impact current. The influence of insulation for the resistance - temperature characteristics of YBCO tape is studied by comparison tests with naked tape and insulating tape in 77 K. The influence of operating temperature on the tape is also studied under subcooled liquid nitrogen condition. For the current impact security of YBCO tape, the critical current degradation and top temperature are analyzed and worked as judgment standards. The testing results is helpful for in developing SFCL in VSC-HVDC.

  3. R.F. Sputtering Deposition of Buffer Layers for Si/YBCO Integrated Microelectronics

    NASA Astrophysics Data System (ADS)

    Rombolà, G.; Ballarini, V.; Chiodoni, A.; Gozzelino, L.; Mezzetti, E.; Minetti, B.; Pirri, C. F.; Tresso, E.; Camerlingo, C.

    The aim of the present work is the optimization of the Si/buffer-layer/YBCO multilayer deposition process so as to grow superconducting films of quality suitable for device applications. The structural properties of the Si/CeO2 system, obtained by RF magnetron sputtering of CeO2 targets in Ar atmosphere, have been studied. More than 50 films have been deposited and some of them submitted to post-deposition annealing treatments both in N2 and O2 atmospheres. The presence of an unwanted amorphous SiO2 layer at the Si/CeO2 interface compromises the YBCO c-axis orientation, and therefore the sharpness of the R versus T transition. A newly designed deposition system has been realized: it has been specially conceived for obtaining bi- and tri-layers, adopting two targets in YSZ and CeO2, respectively. Results on YSZ/Si and CeO2/YSZ/Si systems obtained with the new machine are presented and discussed: (100) oriented YSZ films with nominal thickness of 40 nm have been obtained. The CeO2 film subsequently deposited has the desired (100) orientation. The YBCO film, in the final YBCO/YSZ/CeO2/Si configuration, is c-axis oriented.

  4. A single oxide buffer layer on a cube-textured Ni substrate for the development of YBCO coated conductors by photo-assisted MOCVD

    NASA Astrophysics Data System (ADS)

    Zeng, Jianming; Ignatiev, Alex; Zhou, Yuxiang; Salama, Kamel

    2006-08-01

    Large-scale commercial applications of high-temperature superconducting (HTS) YBa2Cu3O7-x (YBCO)-based second generation coated conductors require simple and cost-effective process technologies to fabricate the buffer layer(s) and YBCO superconducting layer. Sm0.2Ce0.8O2+x (SCO) thick films have been epitaxially deposited on roll-textured Ni substrates as the single buffer layer for HTS coated conductors by using high-rate photo-assisted metal-organic chemical vapour deposition (PhAMOCVD) at a relatively low deposition temperature of 600 °C. YBCO superconducting films were then successfully deposited on these thick SCO single buffer layers by the same high-rate PhAMOCVD process, and yielded critical current densities (Jc) of ~0.52 MA cm-2 at 77 K and zero applied field. X-ray diffraction and scanning electron microscope analyses of SCO/Ni samples revealed very good crystalline structure and surface morphology for the SCO single buffer layers. These results suggest that SCO single buffer layer, as well as the YBCO conductors, fabricated by the high-rate PhAMOCVD technique may offer great potential for manufacturing YBCO coated conductors.

  5. ME-μSR study in YBCO vortex states.

    NASA Astrophysics Data System (ADS)

    Le, T. H.; Boekema, C.

    2007-03-01

    We are analyzing μSR vortex data of YBa2Cu3O7-δ (Tc = 91 K). The average superconducting grain size is ˜20 μm. The μSR data are recorded in a transverse 1 kOe field and at temperatures below 10 K. The μSR technique is used to probe the magnetic fields in the cuprate vortex state. The μSR signals show an oscillatory time dependence. To determine the frequency-dependent signals, we use the Maximum Entropy (ME) transform technique. [2] The ME-Burg algorithm removes noise, and does not suffer from Fourier-like truncation effects. The frequency signals are better fit with Lorentzians than static Gaussians. This Lorentzian behavior indicates the existence of dynamic magnetism in and around the vortex cores. This is consistent with earlier YBCO vortex ME-μSR results [3] and the SO(5) modeling [4] of cuprate superconductivity, predicting the existence of antiferromagnetism in the vortex states. Research is supported by NSF-REU and WiSE at SJSU. [1] C. Boekema et al, Physica C282-287 (1997) 2069. [2] J Lee et al, J Appl Phys 95 (2004) 6906 and ref therein; AIP www: Virtual J Appl of Superconductivity 2004 V6 Iss11. [3] C. Boekema et al, 8th Int M2S-HTSC Conf, Physica C in press. [4] H-D Chen et al, Phys Rev B70 (2004) 024516; SC Zhang, Science 275 (1997) 1089.

  6. Gossamer high-temperature bulk superconductivity in FeSe

    NASA Astrophysics Data System (ADS)

    Sinchenko, A. A.; Grigoriev, P. D.; Orlov, A. P.; Frolov, A. V.; Shakin, A.; Chareev, D. A.; Volkova, O. S.; Vasiliev, A. N.

    2017-04-01

    Using the anisotropic electron transport and susceptibility measurements we demonstrate the appearance of inhomogeneous gossamer superconductivity in FeSe single crystals at ambient pressure and at temperature five times higher than its zero resistance Tc. We also find and quantitatively describe a general property: If inhomogeneous superconductivity in a anisotropic conductor first appears in the form of isolated superconducting islands, it reduces electric resistivity anisotropically with maximal effect along the least conducting axis. This gives a simple tool to study inhomogeneous superconductivity in various anisotropic compounds, which helps to investigate the onset of high-temperature superconductivity.

  7. Superconductivity devices: Commercial use of space

    NASA Technical Reports Server (NTRS)

    Haertling, Gene; Furman, Eugene; Hsi, Chi-Shiung; Li, Guang

    1993-01-01

    A YBCO thick film containing 20 percent Ag2O with a T(sub c) of 86.8 K and J(sub c) of 108 A/sq cm was obtained. The film was fabricated by a two-step firing process, i.e., firing the film at 1000 C for 10 minutes and annealing at 970 C for 30 minutes. The two-step firing process, however, was not suitable for the multiple-lead YBCO sample due to the formation of the 211 green phase at 1000 C in the multiple-lead YBCO sample. A BSCCO thick film printed on a MgO coated MSZ substrate and fired at 845 C for 2 hours exhibited a superconducting behavior at 89 K. Because of its porous microstructure, the critical current density of the BSCCO thick film was limited. This report also includes the results of the YBCO and BSCCO materials used as oxide electrodes for ferroelectric materials. The YBCO electroded PLZT showed higher remanent polarization and coercive field than the sample electroded with silver paste. A higher Curie temperature for the PLZT was obtained from the YBCO electroded sample. The BSCCO electroded sample, however, exhibited the same Curie temperature as that of a silver electroded sample. Dissipation factors of the ferroelectric samples increased when the oxide electrode was applied.

  8. Mechanical characterization of GdBCO/Ag and YBCO single grains fabricated by top-seeded melt growth at 77 and 300 K

    NASA Astrophysics Data System (ADS)

    Konstantopoulou, K.; Shi, Y. H.; Dennis, A. R.; Durrell, J. H.; Pastor, J. Y.; Cardwell, D. A.

    2014-11-01

    YBaCuO and GdBaCuO + 15 wt% Ag large, single-grain, bulk superconductors have been fabricated via the top-seeded, melt-growth (TSMG) process using a generic NdBCO seed. The mechanical behavior of both materials has been investigated by means of three-point bending (TPB) and transversal tensile tests at 77 and 300 K. The strength, fracture toughness and hardness of the samples were studied for two directions of applied load to obtain comprehensive information about the effect of microstructural anisotropy on the macroscopic and microscopic mechanical properties of these technologically important materials. Splitting (Brazilian) tests were carried out on as-melt-processed cylindrical samples following a standard oxygenation process and with the load applied parallel to the growth-facet lines characteristic of the TSMG process. In addition, the elastic modulus of each material was measured by three different techniques and related to the microstructure of each sample using optical microscopy. The results show that both the mechanical properties and the elastic modulus of both YBCO and GdBCP/Ag are improved at 77 K. However, the GdBCO/Ag samples are less anisotropic and exhibit better mechanical behavior due to the presence of silver particles in the bulk, superconducting matrix. The splitting tensile strength was determined at 77 K and both materials were found to exhibit similar behavior, independently of their differences in microstructure.

  9. In-Situ Deposition of YBCO/CeO2 on Biaxially Textured Ni Alloy Tapes by Thermal Coevaporation

    NASA Astrophysics Data System (ADS)

    Bindi, M.; Gianni, L.; Zannella, S.; Botarelli, A.; Baldini, A.; Gauzzi, A.; Tuissi, A.

    We report on the in-situ preparation and characterization of coated conductors consisting of a ~ 400 nm thick YBCO superconducting film grown by thermal co-evaporation on a ~ 200 nm thick CeO2 buffer layer grown by e-beam evaporation on biaxially textured Ni-Cr and Ni-V substrates. We studied the degree of texture of both YBCO and CeO2 layers as a function of substrate temperature during deposition and of oxygen partial pressure. X-ray diffraction patterns reveal that the highest degree of (100) texture of the buffer layer, necessary for the subsequent growth of the YBCO film with the desired c-axis orientation, is achieved at substrate temperatures of the order of 670-730°C. The backfilling of the chamber with oxygen during the cooling-down of the substrates after deposition of the CeO2 layer greatly improves the degree of crystallization of the buffer layer. YBCO films show good superconducting properties with critical temperatures Tc of the order of 87 K. Work is in progress to scale up the process for long tapes.

  10. Static Test for a Gravitational Force Coupled to Type 2 YBCO Superconductors

    NASA Technical Reports Server (NTRS)

    Li, Ning; Noever, David; Robertson, Tony; Koczor, Ron; Brantley, Whitt

    1997-01-01

    As a Bose condensate, superconductors provide novel conditions for revisiting previously proposed couplings between electromagnetism and gravity. Strong variations in Cooper pair density, large conductivity and low magnetic permeability define superconductive and degenerate condensates without the traditional density limits imposed by the Fermi energy (approx. 10(exp -6) g cc. Recent experiments have reported anomalous weight loss for a test mass suspended above a rotating type II, YBCO superconductor, with the percentage change (0.05 - 2.1 %) independent of the test mass' chemical composition and diamagnetic properties. A variation of 5 parts per 10' was reported above a stationary (non-rotating) superconductor. In experiments using a sensitive gravimeter, bulk YBCO superconductors were stably levitated in a DC magnetic field. Changes in acceleration were measured to be less than 2 parts in 108 of the normal gravitational acceleration. This result puts new limits on the strength and range of the proposed coupling between static superconductors and gravity.

  11. Study of microstructure and electrical properties of bulk YBCO prepared by melt textured growth technique

    SciTech Connect

    Gonal, M. R.; Krishnan, Madangopal; Tewari, R.; Tyagi, A. K.; Gyore, A.; Vajda, I.

    2015-06-24

    Bulk YBCO components were prepared using Melt Texture Growth (MTG) technique. Components were fabricated using MTG by addition of Y{sub 2}BaCuO{sub 5} (Y211) and Ag to YBCO, which leads to improved grain size without affecting superconducting properties. Green compacts prepared by cold isostatic pressing were pre-sintered at 930°C before subjecting melt texturing. Cooling rates lower than 1 °C.h{sup −1} was used, in between (peritectic) temperature of about 995 and 1025°C, to obtain large grained components. Microstructure studies in details were carried out by Scanning Electron Microscope (SEM), Electron Probe Micro Analysis (EPMA), Orientation Imaging Microscope (OIM) and TEM correlated with electrical properties like Critical current density (J{sub c})

  12. Microstructural studies of YBCO/LLDPE superconductor/polymer composites using XRD and Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Predeep, P.; Bhadrakumari, S.

    2011-06-01

    Strong Meissner effect properties of High Temperature Superconducting YBCO materials make them ideal candidates for magnetic shielding applications. A series of flexible composites formed by mixing such high T c YBCO superconductor with linear low density polyethylene (LLDPE) are synthesized and their crystalline structure, average grain size, and the crystallinity of the composite samples are investigated using X-ray diffraction measurement. Further, Raman scattering experiments from these composites indicated the presence of well-defined lines as well as a broadband of impurity phase. The intensity of the lines is found to decrease with decreasing proportion of the polymer and increasing proportion of the superconductor in the composites indicating that the composites remained phase separated during the formation process.

  13. Study of YBCO tape anisotropy as a function of field, field orientation and operating temperature

    SciTech Connect

    Lombardo, v.; Barzi, E.; Turrioni, D.; Zlobin, A.V.

    2011-06-01

    Superconducting magnets with magnetic fields above 20 T will be needed for a Muon Collider and possible LHC energy upgrade. This field level exceeds the possibilities of traditional Low Temperature Superconductors (LTS) such as Nb{sub 3}Sn and Nb{sub 3}Al. Presently the use of high field high temperature superconductors (HTS) is the only option available for achieving such field levels. Commercially available YBCO comes in tapes and shows noticeable anisotropy with respect to field orientation, which needs to be accounted for during magnet design. In the present work, critical current test results are presented for YBCO tape manufactured by Bruker. Short sample measurements results are presented up to 14 T, assessing the level of anisotropy as a function of field, field orientation and operating temperature.

  14. Magnetization of YBCO film with ac travelling magnetic waves of relatively short wavelengths

    NASA Astrophysics Data System (ADS)

    Wang, Wei; Coombs, Tim

    2017-02-01

    The magnetizations of the YBCO film with ac travelling magnetic waves of relatively short wavelengths were studied. The results have verified that the reported "intermediate value" of the superconducting current density [Wang et al., Appl. Phys. Lett. 104(3), 032602 (2014)] was caused by the existence of multiple transition regions in the sample: the magnetic poles induce ±JC in the pole regions, which produces two transition regions within each wavelength λ ( +JC→-JC→+JC , and vice versa, while the symbol → indicates the transition region). The current densities in the transition region are with intermediate values, which are smaller than the critical value. In case of relatively short wavelength, there are multiple transition regions, which occupy a large fraction of the YBCO sample with intermediate current values. Moreover, the wavelike current distributions might help explain the flux transportation and dc output voltage in HTS flux pump.

  15. Improved noise performance of ultrathin YBCO Dayem bridge nanoSQUIDs

    NASA Astrophysics Data System (ADS)

    Arpaia, R.; Arzeo, M.; Baghdadi, R.; Trabaldo, E.; Lombardi, F.; Bauch, T.

    2017-01-01

    We have fabricated YBa2Cu3O{}7-δ (YBCO) nano superconducting quantum interference devices (nanoSQUIDs), realized in Dayem bridge configuration, on films with thickness down to 10 nm. The devices, which have not been protected by a Au capping layer during the nanopatterning, show modulations of the critical current as a function of the externally applied magnetic field from 300 mK up to the critical temperature of the nanobridges. The absence of the Au shunting layer and the enhancement of the sheet resistance in ultrathin films lead to very large voltage modulations and transfer functions, which make these nanoSQUIDs highly sensitive devices. Indeed, by using bare YBCO nanostructures, we have revealed an upper limit for the intrinsic white flux noise level {S}{{Φ },{{w}}}1/2\\lt 450 {{n}}{{{Φ }}}0 {{Hz}}-1/2.

  16. Introduction of Artificial Pinning Center into PLD-YBCO Coated Conductor on IBAD and Self-Epitaxial CeO2 Buffered Metal Substrate

    SciTech Connect

    Kobayashi, H.; Yamada, Y.; Ishida, S.; Takahashi, K.; Konishi, M.; Ibi, A.; Miyata, S.; Kato, T.; Hirayama, T.; Shiohara, Y.

    2006-03-31

    In order to fabricate YBa2Cu3O7-x (YBCO) coated conductors with high critical current density Jc in magnetic fields, we fabricated YBCO coated conductors with artificial pinning centers by the pulsed laser deposition (PLD) method on a self epitaxial PLD-CeO2 layer and ion-beam assisted deposition (IBAD)-Gd2Zr2O7 (GZO) buffered Hastelloy tape. Artificial pinning centers were introduced by the PLD deposition using the yttria-stabilized zirconia (YSZ) oxide target (nano-dot method) and YBCO target including YSZ particles (mixed target method). In the experiments using YSZ oxide target, YSZ nano-dots were observed. They were approximately 15 nm in height and 10 nm to 70 nm in diameter. We found that the density of nano-dots was controlled by the number of laser pulses. These samples exhibited higher Jc than YBCO films in magnetic fields. Furthermore, a similar improvement of Jc was observed in the experiments using YBCO target including YSZ particles. TEM observation revealed that columnar nano-structure made of BaZrO3 was formed during YBCO deposition and it was effective for pinning. We call this new epitaxial nano-structure 'bamboo structure' from its anisotropic growth and morphology.

  17. Nano Josephson superconducting tunnel junctions in YBa2Cu3O(7-δ) directly patterned with a focused helium ion beam.

    PubMed

    Cybart, Shane A; Cho, E Y; Wong, T J; Wehlin, Björn H; Ma, Meng K; Huynh, Chuong; Dynes, R C

    2015-07-01

    Since the discovery of the high-transition-temperature superconductors (HTSs), researchers have explored many methods to fabricate superconducting tunnel junctions from these materials for basic science purposes and applications. HTS circuits operating at liquid-nitrogen temperatures (∼77 K) would significantly reduce power requirements in comparison with those fabricated from conventional superconductors. The difficulty is that the superconducting coherence length is very short and anisotropic in these materials, typically ∼2 nm in the a-b plane and ∼0.2 nm along the c axis. The electrical properties of Josephson junctions are therefore sensitive to chemical variations and structural defects on atomic length scales. To make multiple uniform HTS junctions, control at the atomic level is required. In this Letter we demonstrate all-HTS Josephson superconducting tunnel junctions created by using a 500-pm-diameter focused beam of helium ions to directly write tunnel barriers into YBa2Cu3O(7-δ) (YBCO) thin films. We demonstrate the ability to control the barrier properties continuously from conducting to insulating by varying the irradiation dose. This technique could provide a reliable and reproducible pathway for scaling up quantum-mechanical circuits operating at liquid-nitrogen temperatures, as well as an avenue to conduct novel planar superconducting tunnelling studies for basic science.

  18. Nano Josephson superconducting tunnel junctions in YBa2Cu3O7-δ directly patterned with a focused helium ion beam

    NASA Astrophysics Data System (ADS)

    Cybart, Shane A.; Cho, E. Y.; Wong, T. J.; Wehlin, Björn H.; Ma, Meng K.; Huynh, Chuong; Dynes, R. C.

    2015-07-01

    Since the discovery of the high-transition-temperature superconductors (HTSs), researchers have explored many methods to fabricate superconducting tunnel junctions from these materials for basic science purposes and applications. HTS circuits operating at liquid-nitrogen temperatures (˜77 K) would significantly reduce power requirements in comparison with those fabricated from conventional superconductors. The difficulty is that the superconducting coherence length is very short and anisotropic in these materials, typically ˜2 nm in the a-b plane and ˜0.2 nm along the c axis. The electrical properties of Josephson junctions are therefore sensitive to chemical variations and structural defects on atomic length scales1. To make multiple uniform HTS junctions, control at the atomic level is required. In this Letter we demonstrate all-HTS Josephson superconducting tunnel junctions created by using a 500-pm-diameter focused beam of helium ions to directly write tunnel barriers into YBa2Cu3O7-δ (YBCO) thin films. We demonstrate the ability to control the barrier properties continuously from conducting to insulating by varying the irradiation dose. This technique could provide a reliable and reproducible pathway for scaling up quantum-mechanical circuits operating at liquid-nitrogen temperatures, as well as an avenue to conduct novel planar superconducting tunnelling studies for basic science.

  19. Spatial variation of the two-fold anisotropic superconducting gap in a monolayer of FeS e0.5T e0.5 on a topological insulator

    NASA Astrophysics Data System (ADS)

    Kamlapure, A.; Manna, S.; Cornils, L.; Hänke, T.; Bremholm, M.; Hofmann, Ph.; Wiebe, J.; Wiesendanger, R.

    2017-03-01

    We present a low temperature scanning tunneling spectroscopy (STS) study of the superconducting properties of monolayers of FeS e0.5T e0.5 grown on the three-dimensional (3D) topological insulator B i2S e1.2T e1.8 . While the morphology and the overall transition temperature resembles those of similarly doped bulk crystals, we find a two-fold anisotropic s -wave gap function. The two-fold nature of the gap symmetry is evident from the Bogoliubov quasiparticle interference (QPI) pattern, which shows distinct C2 symmetric scattering intensities. Spatially resolved spectroscopic data shows a strong inhomogeneity in the size and anisotropy strength of the energy gaps, which cannot be correlated merely to the local chemical disorder. Instead, we argue that the gap inhomogeneity emerges with a similar mechanism as in disordered superconductors. Our sample system provides an ideal platform to study unconventional superconductivity in close proximity to a topological insulator.

  20. 2D SQIF arrays using 20 000 YBCO high R n Josephson junctions

    NASA Astrophysics Data System (ADS)

    Mitchell, E. E.; Hannam, K. E.; Lazar, J.; Leslie, K. E.; Lewis, C. J.; Grancea, A.; Keenan, S. T.; Lam, S. K. H.; Foley, C. P.

    2016-06-01

    Superconducting quantum interference filters (SQIFs) have been created using two dimensional arrays of YBCO step-edge Josephson junctions connected together in series and parallel configurations via superconducting loops with a range of loop areas and loop inductances. A SQIF response, as evidenced by a single large anti-peak at zero applied flux, is reported at 77 K for step-edge junction arrays with the junction number N = 1 000 up to 20 000. The SQIF sensitivity (slope of peak) increased linearly with N up to a maximum of 1530 V T-1. Array parameters related to geometry and average junction characteristics are investigated in order to understand and improve the SQIF performance in high temperature superconducting arrays. Initial investigations also focus on the effect of the SQUID inductance factor on the SQIF sensitivity by varying both the mean critical current and the mean inductance of the loops in the array. The RF response to a 30 MHz signal is demonstrated.

  1. Ferromagnetic/superconducting proximity effect in La0.7Ca0.3MnO3/YBa2Cu3O7-δ superlattices

    NASA Astrophysics Data System (ADS)

    Sefrioui, Z.; Arias, D.; Peña, V.; Villegas, J. E.; Varela, M.; Prieto, P.; León, C.; Martinez, J. L.; Santamaria, J.

    2003-06-01

    We study the interplay between magnetism and superconductivity in high-quality YBa2Cu3O7(YBCO)/La0.7Ca0.3MnO3(LCMO) superlattices. We find evidence for the YBCO superconductivity depression in the presence of the LCMO layers. We show that due to its short coherence length, superconductivity survives in the YBCO down to a much smaller thickness in the presence of the magnetic layer than in low Tc superconductors. We also find that for a fixed thickness of the superconducting layer, superconductivity is depressed over a thickness interval of the magnetic layer in the 100 nm range. This is a much longer length scale than that predicted by the theory of ferromagnetic/superconducting proximity effect.

  2. Incorporating YBCO Coated Conductors in High-speed Superconducting Generators

    DTIC Science & Technology

    2008-07-01

    4.0 kW/lb (8.82 kW/kg). The machine configuration chosen by GE for design was a homopolar inductor alternator (HIA) which locates the...extremely severe ac loss environment. Even if this is ultimately impossible for high speed generators, it may not preclude lower speed motors and

  3. Bulk YBCO seeded with 45°-45° bridge-seeds of different lengths

    NASA Astrophysics Data System (ADS)

    Shi, Y.-H.; Durrell, J. H.; Dennis, A. R.; Cardwell, D. A.

    2013-01-01

    Single grain, (RE)BCO (rare earth-barium-copper oxide) bulk superconductors in large or complicated geometries are required for a variety of potential applications, such as in motors and generators and magnetic shielding devices. As a result, top, multi-seeded, melt growth has been investigated over the past 15 years in an attempt to enlarge the size of (RE)BCO single grains specifically for such applications. Of these multi-seeding techniques, so-called bridge-seeding provides the best alignment of two seeds in a single grain growth process. Here we report, for the first time, the successful growth of YBCO (yttrium-barium-copper oxide) using a special, 45°-45°, arrangement of bridge-seeds. The superconducting properties, including trapped field, of the multi-seeded YBCO grains have been measured for different bridge lengths of the 45°-45° bridge-seeds. The boundaries at the impinging growth front and the growth features of the top, multi-seeded surface and cross-section of the multi-seeded, samples have been analysed using optical microscopy. The results suggest that an impurity-free boundary between the two seeds of each leg of the bridge-seed can form when 45°-45° bridge-seeds are used to enlarge the size of YBCO grains.

  4. Effect of Au nano-particles doping on polycrystalline YBCO high temperature superconductor

    NASA Astrophysics Data System (ADS)

    Dadras, Sedigheh; Gharehgazloo, Zahra

    2016-07-01

    In this research, we prepared different Au nanoparticles (0.1-2 wt%) doped YBCO high temperature superconductor samples by sol-gel method. To characterize the samples, we used X-Ray diffraction (XRD) and scanning electron microscope (SEM) analysis. Results show the formation of orthorhombic phase of superconductivity for all prepared samples. We observed that by adding Au nanoparticles, the grains' size of the samples reduces from 76 nm to 47 nm as well. The critical current density (Jc) and transition temperature (Tc) were determined using current versus voltage (I-V) and resistivity versus temperature (ρ-T) measurements, respectively. We found that by increasing Au nanoparticles in the compound, in comparison to the pure YBCO sample, the transition temperature, pinning energy and critical current density will increase. Also, the highest Jc is for 1 wt% Au doped YBCO compound that its critical current density is about 8 times more than the Jc of pure one in 0.7 T magnetic field.

  5. Modeling of planar quasi-TEM superconducting transmission lines

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

    An application of the phenomenological loss equivalence method (Lee and Itoh, 1989) in modeling the microwave behavior of planar quasi-TEM superconducting transmission lines is presented. For validation of the model, data are used from measurements of a YBCO superconducting thin-film coplanar-waveguide lowpass filter on a lanthanum aluminate substrate. Measured and modeled S-parameters of an existing superconducting coplanar waveguide lowpass filter agree to within 0.3 dB in magnitude and 0.5 radians in phase. Extracted values for penetration depth and real part of the conductivity of the superconducting film are within 10 percent of other researchers' findings.

  6. Ultrafast Broadband Photodetectors for High-Tc Superconductive Optoelectronics

    DTIC Science & Technology

    1997-01-01

    TITLE AND SUBTITLE Ultrafast Broadband Photodetectors for High-Tc Supercondcutive Optoelectronics 6. AUTHOR(S) Dr. Roman Sobolewski (PI) Dr...The rapid suppression of the Maki-Thompson process for the oxygen-deficient YBCO films, indicated an unconventional symmetry of the superconducting

  7. High Tc superconducting bolometric and nonbolometric infrared (IR) detectors

    NASA Technical Reports Server (NTRS)

    Lakeou, Samuel; Rajeswari, M.; Goyal, Anuja

    1995-01-01

    The workplan for the period August 1994 through August 1995 includes the following: (1) expand the Applied Superconductivity Laboratory to include stand-alone optical response and noise measurement setups; (2) pursue studies of the low frequency excess electrical noise in YBCO films; and (3) enhance the academic support component of the project through increased student and faculty participation.

  8. General approach for the determination of the magneto-angular dependence of the critical current of YBCO coated conductors

    NASA Astrophysics Data System (ADS)

    Zhang, X.; Zhong, Z.; Ruiz, H. S.; Geng, J.; Coombs, T. A.

    2017-02-01

    The physical understanding and numerical modelling of superconducting devices which exploit the high performance of second generation high temperature superconducting tapes (2G-HTS), is commonly hindered by the lack of accurate functions which allow the consideration of the in-field dependence of the critical current. This is true regardless of the manufacturer of the superconducting tape. In this paper, we present a general approach for determining a unified function I c(B, θ), ultimately capable of describing the magneto-angular dependence of the in-field critical current of commercial 2G-HTS tapes in the Lorentz configuration. Five widely different superconducting tapes, provided by three different manufacturers, have been tested in a liquid nitrogen bath and external magnetic fields of up to 400 mT. The critical current was recorded at 90 different orientations of the magnetic field ranging from θ = 0°, i.e., with B aligned with the crystallographic ab-planes of the YBCO layer, towards ±90°, i.e., with B perpendicular to the wider surfaces of the 2G-HTS tape. The whole set of experimental data has been analysed using a novel multi-objective model capable of predicting a sole function I c(B, θ). This allows an accurate validation of the experimental data regardless of the fabrication differences and widths of the superconducting tapes. It is shown that, in spite of the wide set of differences between the fabrication and composition of the considered tapes, at liquid nitrogen temperature the magneto-angular dependence of the in-field critical current of YBCO-based 2G-HTS tapes, can be described by a universal function I c(f(B), θ), with a power law field dependence dominated by the Kim’s factor B/B 0, and an angular dependence moderated by the electron mass anisotropy ratio of the YBCO layer.

  9. Influence of Both Cooling Rate and TeO2 Addition on the Properties of YBCO Superconductor

    NASA Astrophysics Data System (ADS)

    Ahmed, Yasser Momtaz Zaki; Hassan, Mervat Said; Abd-Elatif, Hassan

    2016-12-01

    Composite of superconducting system YBCO-TeO2 was synthesized utilizing solid-state reaction technique. Different weight percentages of TeO2 were mixed with a basic mixture [YBCO] for the synthesis of [YBa2Cu3O7- y ]1- x (TeO2) x composites. These mixtures were sintered at 1213 K (940 °C) for 24 hours and the samples cooled down by two different ways. The first way carried out via slowly cooling in furnace with the rate of 274 K/min to 275 K/min (1 °C/min to 2 °C/min) and the second one is quenching in oxygen gas. The XRD analysis showed that YBCO orthorhombic phase is the major phase appeared in all samples with different TeO2 content regardless of the cooling way. Additionally, minor unknown secondary phases appeared and enlarged with increasing TeO2 addition. Although quenched samples showed a phase difference between the sample's outer surface (orthorhombic) and its interior (tetragonal), the slowly cooled one did not clearly show such distinction. Moreover, doping YBCO with TeO2 leads to increase in the sample bulk density and reduction in their degradation degree in the wet atmosphere.

  10. Design of a Cryogen Free Cryo-flipper using a High Tc YBCO Film

    NASA Astrophysics Data System (ADS)

    Parnell, S. R.; Kaiser, H.; Washington, A. L.; Li, F.; Wang, T.; Baxter, D. V.; Pynn, R.

    It is well-known that the Meissner effect in superconducting materials can be used to provide a well-defined non- adiabatic magnetic field transition that can be utilised to produce an efficient white beam neutron spin flipper. Typically these devices utilise niobium and hence require continuous use of liquid helium in order to maintain the device tem- perature. The use of high Tc materials removes the need for cryogens and has been explored previously and shown to provide efficient flipping of the neutron spin. Improvements in thin high Tc films over the past few years make these materials even more attractive. Here we present a design using a 350-nm-thick YBCO film capped with 100 nm of gold on a 78 x 100 x 0.5 mm sapphire substrate (Theva, Germany). The apparatus is compact (200 mm in length along the neutron beam), consisting of an oxygen-free high-conductivity copper frame, which holds the YBCO film and is mounted to the cold finger of a closed-cycle refrigerator. The part of the vacuum chamber, where the YBCO film is located, is ≈ 50 mm wide, which allows us to minimise the distance from the film to the external magnets. This distance is 26 mm on each side. The details of the guide field design are also discussed. In this design, the maximum neutron beam size that can be used is 40 × 40 mm2 and we can easily switch from a vertical to a horizontal guide field on either side of the YBCO film.

  11. Superconductivity in Cuba: Reaching the Frontline

    NASA Astrophysics Data System (ADS)

    Arés Muzio, Oscar; Altshuler, Ernesto

    The start of experimental research in the field of superconductivity was a very special moment for Cuban physics: Cuban scientists at the Physics Faculty, University of Havana, synthesized the first Cuban superconductor (a 123-YBCO ceramic sample) just 2 months after the publication of the famous paper by Wu and co-workers that triggered the frantic race of High Tc superconductors all over the world. We timely joined the world's frontline in superconductor research.

  12. Preparation of high grade YBCO powders and pellets through the glycerol route

    NASA Astrophysics Data System (ADS)

    Kamat, R. V.; Vittal Rao, T. V.; Pillai, K. T.; Vaidya, V. N.; Sood, D. D.

    1991-10-01

    Superconducting powders and pellets of Y-Ba-Cu-O were prepared by a new solution route. Nitrates of Y, Ba and Cu were heated with a controlled amount of glycerol to get a dry powder which on suitable heat treatment gave high grade YBCO powder/pellets. Characterisation was done by X-ray diffractometry, thermogravimetry, differential thermal analysis and also by measuring the surface area, carbon-content, bulk-density, transition temperature and the critical current. The pellets could be densified to 94% theoretical density (TD) and had a superconducting transition width of 1 K. The critical current densities were in the range of 200-500 A/cm 2.

  13. Thickness and field dependent superconductivity in YBa2Cu3O7/La0.7Sr0.3MnO3 bilayers

    NASA Astrophysics Data System (ADS)

    Lin, J. G.; Hsu, Daniel; Song, M. Y.; Chiang, C. H.; Chan, W. C.

    2010-05-01

    Transport and magnetization properties of superconducting/ferromagnetic bilayers YBa2Cu3O7/La0.7Sr0.3MnO3 (YBCO/LSMO) are investigated with the thickness of bottom LSMO layer fixed at 50 nm and that of top YBCO (t) layer varied from 20 to 100 nm. Compared to bulk YBCO, the off set of superconducting temperature TSC-off is suppressed by 10 K for t =20 nm. The suppression rate of TSC versus magnetic field H is obtained as 1.2±0.2 K/T for all bilayers. Considering the polarization effect of LSMO on superconductivity is similar to the field effect, the internal field created by the LSMO in the YBCO(20nm)/LSMO(50nm) bilayer is estimated as 40 T.

  14. Fabrication of high-Tc superconducting hot electron bolometers for terahertz mixer applications

    NASA Astrophysics Data System (ADS)

    Villegier, Jean-Claude; Degardin, Annick F.; Guillet, Bruno; Houze, Frederic; Kreisler, Alain J.; Chaubet, Michel

    2005-03-01

    Superconducting Hot Electron Bolometer (HEB) mixers are a competitive alternative to Schottky diode mixers or other conventional superconducting receiver technologies in the terahertz frequency range because of their ultrawide bandwidth (from millimeter waves to the visible), high conversion gain, and low intrinsic noise level, even at 77 K. A new technological process has been developed to realize HEB mixers based on high temperature superconducting materials, using 15 to 40 nm thick layers of YBa2Cu3O7-δ (YBCO), sputtered on MgO (100) substrates by hollow cathode magnetron sputtering. Critical temperature values of YBCO films were found in the 85 to 91 K range. Sub-micron HEB bridges (0.8 μm x 0.8 μm) were obtained by combining electronic and UV lithography followed by selective etching techniques. Realization of YBCO HEB coupling to planar integrated gold antennas was also considered.

  15. Improved transport properties of polycrystalline YBCO thin-films

    NASA Astrophysics Data System (ADS)

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

    1994-12-01

    Resistive evaporation technique was used to fabricate polycrystalline YBaCuO and YBaNaCuO thin films on MgO substrates. Heat treatment was carried out in a low oxygen partial pressure. Polycrystalline YBCO and Na doped YBCO thin films samples were thus obtained using the same technique and conditions. The critical current density of Na doped YBCO sample was measured to be significantly higher than that of the undoped YBCO one. The results are discussed in terms of the Na contribution to the intragrain conductivity.

  16. A simple multi-seeding approach to growth of large YBCO bulk with a diameter above 53 mm

    NASA Astrophysics Data System (ADS)

    Tang, Tian-wei; Wu, Dong-jie; Wu, Xing-da; Xu, Ke-Xi

    2015-12-01

    A successful simple multi-seeding approach to growing large size Y-Ba-C-O (YBCO) bulks is reported. Compared with the common single seeding method, our multi-seeding method is more efficient. By using four SmBa2Cu3O7-δ (Sm-123) seeds cut from a large size Sm-Ba-C-O (SmBCO) single domain, large YBCO samples up to 53 mm in diameter could be produced successfully and 100 mm diameter samples can also be grown. Experimental results show that the processing time can be shortened greatly by using this new approach, and the superconducting properties can also be improved. The Hall probe mapping shows that the trapped field distribution of 53 mm diameter multi-seeded sample is homogeneous and the peak value is up to 0.53 T. The magnetic levitation force density reaches to 14.7 N/cm2 (77 K, 0.5 T).

  17. Superconductivity suppression in YBa2Cu3O7-δ/La0.7Sr0.3MnO3 bilayer films

    NASA Astrophysics Data System (ADS)

    Sharma, Minaxi; Sharma, K. K.; Choudhary, R. J.; Kumar, Ravi

    2014-12-01

    We study the thickness effect of YBa2Cu3O7-δ (YBCO) in YBCO/La0.7Sr0.3MnO3 (LSMO) bilayer films, fabricated on LaAlO3 (001) substrate using pulsed laser deposition technique. The thickness dependent transport behavior of YBCO layer in considered bilayer systems demonstrate a clear onset critical temperature at 60 K and 80 K for 100 nm and 200 nm thick YBCO layer systems, respectively, whereas 50 nm thick YBCO system reveals complete suppression in the superconductivity. With the increase in thickness of YBCO layer, the magnetoresistance (MR) data show both positive and negative MR. The positive MR in superconducting regime dominates the negative MR, suppress the double exchange interaction. The maximum magnetoresistance ratio ˜81% at 64 K and ˜47% at 30 K temperature are observed for 200 nm and 100 nm YBCO layers, respectively. In YBCO(200 nm)/LSMO(200 nm) bilayer specimen, the temperature co-efficient of resistance is ˜8.4% K-1 at 72 K which can be practical for bolometric performances and temperature sensors.

  18. Preferred Orientation Contribution to the Anisotropic Normal State Resistivity in Superconducting Melt-Cast Processed Bi2Sr2CaCu2O8+δ

    PubMed Central

    Dellicour, Aline; Vertruyen, Benedicte; Rikel, Mark O.; Lutterotti, Luca; Pautrat, Alain; Ouladdiaf, Bachir; Chateigner, Daniel

    2017-01-01

    We describe how the contribution of crystallographic texture to the anisotropy of the resistivity of polycrystalline samples can be estimated by averaging over crystallographic orientations through a geometric mean approach. The calculation takes into account the orientation distribution refined from neutron diffraction data and literature values for the single crystal resistivity tensor. The example discussed here is a melt-cast processed Bi2Sr2CaCu2O8+δ (Bi-2212) polycrystalline tube in which the main texture component is a <010> fiber texture with relatively low texture strength. Experimentally-measured resistivities along the longitudinal, radial, and tangential directions of the Bi-2212 tube were compared to calculated values and found to be of the same order of magnitude. Calculations for this example and additional simulations for various texture strengths and single crystal resistivity anisotropies confirm that in the case of highly anisotropic phases such as Bi-2212, even low texture strengths have a significant effect on the anisotropy of the resistivity in polycrystalline samples. PMID:28772894

  19. Performance of a polarised neutron cryo-flipper using a high TcYBCO film

    NASA Astrophysics Data System (ADS)

    Parnell, S. R.; Washington, A. L.; Kaiser, H.; Li, F.; Wang, T.; Hamilton, W. A.; Baxter, D. V.; Pynn, R.

    2013-09-01

    It is well-known that the Meissner effect in superconducting materials can be used to provide a well-defined, non-adiabatic, magnetic-field transition. This can be utilised to produce a highly efficient neutron spin flipper that is suitable for use with neutrons of multiple wavelengths. Devices of this type using superconducting niobium have been deployed on neutron diffractometers for several decades but have required liquid helium to maintain the correct temperature. The use of high Tc materials, which removes the need for cryogens and simplifies the device, was first explored by Fitzsimmons et al. in [1]. In this communication, we describe a π flipper which uses commercially available films consisting of a 350-nm-thick YBCO film capped with 100 nm of gold on a 78×100×0.5 mm sapphire substrate. We discuss the design and performance of this device. The apparatus is compact (≈200 mm in length along the neutron beam), consisting of an oxygen-free high-conductivity copper frame, which holds the YBCO film and is mounted to the cold finger of a closed-cycle He refrigerator. The part of the vacuum chamber, where the YBCO film is located, is 5 cm wide, which allows us to minimise the distance from the film to the magnetic guide fields. Negligible small angle neutron scattering is observed from the flipper and its transmission is measured to be greater than 98.5% over a wide band of neutron wavelengths. In this design, the maximum neutron beam size that can be used is 42×42 mm2 and we can easily switch from a vertical to a horizontal guide field (both perpendicular to the neutron beam) on either side of the YBCO film. Data are reported for neutron wavelengths between 4 and 8.5 Å and flipping efficiencies under a variety of conditions are discussed. Under optimum conditions an efficiency of 99.5±0.3% was achieved for 4-8 Å neutrons on a pulsed source and 99.4±0.5% was achieved at a monochromatic source using a neutron wavelength of 4.2 Å.

  20. Superconductivity in MgB 2

    NASA Astrophysics Data System (ADS)

    Akimitsu, Jun; Muranaka, Takahiro

    2003-05-01

    We recently discovered that the intermetallic compound magnesium diboride (MgB2) exhibits the highest superconducting transition temperature (Tc=39 K) of all the metallic superconductors. In this paper we report on the basic superconducting characteristics of MgB2 and the current status of the research for the unanswered problem in this superconductivity. Especially, we review the several reports for the superconducting gap (Δ) by the spectroscopic measurements. Moreover we introduce the research into its anisotropic parameter (γ), which is important for the understanding of this superconducting states in this material.

  1. Processing and property evaluation of metal matrix superconducting materials

    NASA Technical Reports Server (NTRS)

    Rao, Appajosula S.

    1995-01-01

    Metal - superconductor (YBCO) systems have been prepared and characterized by resistivity, ac susceptibility and dc SQUID magnetic moment measurements. The silver composites showed superconducting transition for all the composites processed and the superconducting transition temperature tends to depend upon the concentration of the silver in the composite. Aluminum composites showed an unusual resistivity results with two transitions around 90 K and 120 K. The superconducting property of silver composites can be explained qualitatively in terms of the proximity theory that has been suggested for the low temperature superconductors.

  2. Vortex motion in YBCO thin films

    NASA Astrophysics Data System (ADS)

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

    1999-09-01

    Hall resistivity measurements as function of temperature in the vicinity of Tc were carried out on a thin films YBCO superconductors. A sign reversal of Hall voltage with external magnetic field applied along c axis have been observed upon crossing Tc. Hall voltage in the mixed state was found to be insensitive to the external magnetic field inversion. These effects are discussed and explained in terms of vortex motion under the influence of Magnus force balanced by large damping force. It is argued that in this model the flux-line velocity has component opposite to the superfluid current direction thus yielding a negative Hall voltage.

  3. Fast infrared response of YBCO thin films

    NASA Technical Reports Server (NTRS)

    Ballentine, P. H.; Kadin, A. M.; Donaldson, W. R.; Scofield, J. H.; Bajuk, L.

    1990-01-01

    The response to short infrared pulses of some epitaxial YBCO films prepared by sputter deposition and by electron-beam evaporation is reported. The response is found to be essentially bolometric on the ns timescale, with some indirect hints of nonequilibrium electron transport on the ps scale. Fast switching could be obtained either by biasing the switch close to the critical current or by cooling the film below about 20 K. These results are encouraging for potential application to a high-current optically-triggered opening switch.

  4. Anisotropic Nonmonotonic Behavior of the Superconducting Critical Current in Thin YBa2Cu3O7-δ Films on Vicinal SrTiO3 Surfaces

    SciTech Connect

    Cantoni, Claudia; Verebelyi, Darren; Specht, Eliot D; Budai, John D; Christen, David K

    2005-01-01

    The critical current density of epitaxial YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO) films grown on vicinal SrTiO{sub 3} substrates was investigated by electrical transport measurements along and across the steps of the SrTiO{sub 3} surface for a range of temperatures of 10 to 85 K and in applied magnetic fields varying from 0 to 14 T. For vicinal angles of 4{sup o} and 8{sup o}, we found evidence of enhanced pinning in the longitudinal direction at low magnetic fields for a wide region of temperatures and attribute this phenomenon to antiphase boundaries in the YBCO film. The transverse J{sub c} data showed a peak in the J{sub c}(H) curve at low magnetic fields, which was explained on the basis of magnetic interaction between Abrikosov and Abrikosov-Josephson vortices. The in-plane J{sub c} anisotropy observed for vicinal angles of 0.4{sup o} was reversed with respect to the 8{sup o} and 4{sup o} samples. This phenomenon was interpreted on the basis of strain induced in the YBCO film by the stepped substrate's surface.

  5. Disorder-controlled superconductivity at YBa2Cu3O7/SrTiO3 interfaces

    NASA Astrophysics Data System (ADS)

    Garcia-Barriocanal, J.; Perez-Muñoz, A. M.; Sefrioui, Z.; Arias, D.; Varela, M.; Leon, C.; Pennycook, S. J.; Santamaria, J.

    2013-06-01

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

  6. Buffer layers for deposition of superconducting YBaCuO thin film on polycrystalline diamond

    NASA Astrophysics Data System (ADS)

    Beetz, Charles P.; Cui, G. J.; Lincoln, B. A.; Kirlin, Peter S.

    1992-09-01

    In an attempt to combine the properties of high temperature superconductors with the high thermal conductivity and low specific heat of diamond, we have explored the deposition of in- situ YBa(subscript 2)Cu(subscript 3)O(subscript 7-(delta) ) (YBCO) superconducting films on polycrystalline diamond thin films. We demonstrate for the first time superconducting YBCO films on diamond employing multiple layer buffer layer systems. Three different composite buffer layer systems were explored for this purpose: (1) Diamond/Zr/YSZ/YBCO, (2) Diamond/Si(subscript 3)N(subscript 4)/YSZ/YBCO, and (3) Diamond/SiO(subscript 2)/YSZ/YBCO. Adherent thin Zr films were deposited by dc sputtering on the diamond films at 450 to 820 degree(s)C. The yttria stabilized zirconia (YSZ) was deposited by reactive RF sputtering at 680 to 750 degree(s)C. The Si(subscript 3)N(subscript 4) and SiO(subscript 2) were also deposited by on-axis RF sputtering at 400 to 700 degree(s)C. YBCO films were grown on the buffer layers by off-axis RF sputtering at substrate temperatures between 690 degree(s)C and 750 degree(s)C. In all cases, the as-deposited YBCO films were superconducting above 77 K. This demonstration enables the fabrication of low heat capacity, fast response time bolometric far IR detectors and paves the way for the use of HTSC as a high frequency interconnect metallization on thick diamond film based multichip modules.

  7. Multi-Aperture Shower Design for the Improvement of the Transverse Uniformity of MOCVD-Derived GdYBCO Films.

    PubMed

    Zhao, Ruipeng; Liu, Qing; Xia, Yudong; Zhang, Fei; Lu, Yuming; Cai, Chuanbing; Tao, Bowan; Li, Yanrong

    2017-09-15

    A multi-aperture shower design is reported to improve the transverse uniformity of GdYBCO superconducting films on the template of sputtered-LaMnO₃/epitaxial-MgO/IBAD-MgO/solution deposition planarization (SDP)-Y₂O₃-buffered Hastelloy tapes. The GdYBCO films were prepared by the metal organic chemical vapor deposition (MOCVD) process. The transverse uniformities of structure, morphology, thickness, and performance were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), step profiler, and the standard four-probe method using the criteria of 1 μV/cm, respectively. Through adopting the multi-aperture shower instead of the slit shower, measurement by step profiler revealed that the thickness difference between the middle and the edges based on the slit shower design was well eliminated. Characterization by SEM showed that a GdYBCO film with a smooth surface was successfully prepared. Moreover, the transport critical current density (Jc) of its middle and edge positions at 77 K and self-field were found to be over 5 MA/cm² through adopting the micro-bridge four-probe method.

  8. Multi-Aperture Shower Design for the Improvement of the Transverse Uniformity of MOCVD-Derived GdYBCO Films

    PubMed Central

    Zhao, Ruipeng; Liu, Qing; Xia, Yudong; Zhang, Fei; Lu, Yuming; Cai, Chuanbing; Tao, Bowan; Li, Yanrong

    2017-01-01

    A multi-aperture shower design is reported to improve the transverse uniformity of GdYBCO superconducting films on the template of sputtered-LaMnO3/epitaxial-MgO/IBAD-MgO/solution deposition planarization (SDP)-Y2O3-buffered Hastelloy tapes. The GdYBCO films were prepared by the metal organic chemical vapor deposition (MOCVD) process. The transverse uniformities of structure, morphology, thickness, and performance were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), step profiler, and the standard four-probe method using the criteria of 1 μV/cm, respectively. Through adopting the multi-aperture shower instead of the slit shower, measurement by step profiler revealed that the thickness difference between the middle and the edges based on the slit shower design was well eliminated. Characterization by SEM showed that a GdYBCO film with a smooth surface was successfully prepared. Moreover, the transport critical current density (Jc) of its middle and edge positions at 77 K and self-field were found to be over 5 MA/cm2 through adopting the micro-bridge four-probe method. PMID:28914793

  9. An electron backscatter diffraction investigation of crystallographic orientations of embedded nanoparticles within melt-textured YBCO high temperature superconductors

    NASA Astrophysics Data System (ADS)

    Koblischka-Veneva, A.; Koblischka, M. R.; Babu, N. Hari; Cardwell, D. A.; Shlyk, L.; Krabbes, G.

    2006-07-01

    Microstructures of melt-textured YBCO samples with embedded nanosized particles of Y2BaCuO5 (Y-211) and Y2Ba4CuMOx (M-2411 with M = U,Zr) are analysed by means of electron backscatter diffraction (EBSD). With the recent developments of the EBSD technique, we can directly measure the crystallographic orientation of the embedded nanoparticles, employing a spatial resolution of about 40 nm. The high image quality of the Kikuchi patterns allows true three-phase (YBCO, Y-211 and M-2411) scans to be performed. The Y-211 particles do not exhibit any preferred orientation, even if their size is considerably reduced, to the 100 nm range. The size reduction reduces the negative influence of the Y-211 particles on the YBCO matrix, however. U-2411 particles, which are formed during the processing stage, do not show any orientation, and with increasing concentration, some texture develops. In contrast to this, embedded Zr-2411 particles are fully oriented in the (001) orientation according to the surrounding superconducting matrix.

  10. Role of nano and micron-sized inclusions on the oxygen controlled preform optimized infiltration growth processed YBCO superconductors

    NASA Astrophysics Data System (ADS)

    Pavan Kumar Naik, S.; Bai, V. Seshu

    2017-02-01

    In the present work, with the aim of improving the local flux pinning at the unit cell level in the YBa2Cu3O7-δ (YBCO) bulk superconductors, 20 wt% of nanoscale Sm2O3 and micron sized (Nd, Sm, Gd)2BaCuO5 secondary phase particles were added to YBCO and processed in oxygen controlled preform optimized infiltration growth process. Nano Dispersive Sol Casting method is employed to homogeneously distribute the nano Sm2O3 particles of 30-50 nm without any agglomeration in the precursor powder. Microstructural investigations on doped samples show the chemical fluctuations as annuli cores in the 211 phase particles. The introduction of mixed rare earth elements at Y-site resulted in compositional fluctuations in the superconducting matrix. The associated lattice mismatch defects have provided flux pinning up to large magnetic fields. Magnetic field dependence of current density (Jc(H)) at different temperatures revealed that the dominant pinning mechanism is caused by spatial variations of critical temperatures, due to the spatial fluctuations in the matrix composition. As the number of rare earth elements increased in the YBCO, the peak field position in the scaling of the normalized pinning force density (Fp/Fp max) significantly gets shifted towards the higher fields. The curves of Jc(H) and Fp/Fp max at different temperatures clearly indicate the LRE substitution for LRE' or Ba-sites for δTc pinning.

  11. Solderability Study of RABiTS-Based YBCO Coated Conductors

    SciTech Connect

    Zhang, Yifei; Duckworth, Robert C; Ha, Tam T; Gouge, Michael J

    2011-01-01

    The solderability of commercially available YBa{sub 2}Cu{sub 3}O{sub 7-x} (YBCO) coated conductors that were made from Rolling Assisted Biaxially Textured Substrates (RABiTS)-based templates was studied. The coated conductors, also known as second-generation (2G) high temperature superconductor (HTS) wires (in the geometry of flat tapes about 4 mm wide), were laminated with copper, brass, or stainless steel strips as stabilizers. To understand the factors that influence their solderability, surface profilometry and scanning electron microscopy were used to characterize the wire surfaces. The solderability of three solders, 52In48Sn, 67Bi33In, and 100In (wt.%), was evaluated using a standard test (IPC/ECA J-STD-002) and with two different commercial fluxes. It was found that the solderability varied with the solder and flux but the three different wires showed similar solderability for a fixed combination of solder and flux. Solder joints of the 2G wires were fabricated using the tools and the procedures recommended by the HTS wire manufacturer. The solder joints were made in a lap-joint geometry and with the superconducting sides of the two wires face-to-face. The electrical resistances of the solder joints were measured at 77 K, and the results were analyzed to qualify the soldering materials and evaluate the soldering process. It was concluded that although the selection of soldering materials affected the resistance of a solder joint, the resistivity of the stabilizer was the dominant factor.

  12. Effect of metal oxides addition on the superconducting properties of YBaCuO.

    PubMed

    Lee, Sang-Heon; Choi, Yong

    2011-07-01

    The superconducting properties of YBCO superconductor with ZrO2 addition prepared by different contents were prepared by a unique method so called thermal pyrolysis process to study the effect of the zirconium oxide on the electromagnetic properties and superconducting mechanism of the superconductor. The critical temperature of YBCO superconductor was not predominately dependent upon the zirconium oxide. The maximum magnetism was observed by adding 2% zirconium oxide. The addition of zirconium oxide forming a pinning center of magnetic flux due to ZrO2 phase which was related to the change of electromagnetic properties of the YBCO superconductor. The result indicates that magnetization is proportional to the number of magnetic flux lines passing through the sample. The added ZrO2 appear to contribute the increasing Vickers hardness.

  13. Fabrication of cube textured NiO seed layer for YBCO coated conductor

    NASA Astrophysics Data System (ADS)

    Yang, J.; Shi, D. Q.; Park, C.; Song, K. J.; Ko, R. K.; Liu, H. Z.; Gu, H. W.

    2004-10-01

    The cube textured NiO was formed on pure Ni tape using a simple approach of oxidizing the surface of the Ni tape for 3-20 min in air at 1130-1200 °C. The thickness of the NiO layer was about 1-5 μm. X-ray diffraction (XRD) θ-2 θ scan, ω-scan, ϕ-scan, and pole figure were employed to characterize the in-plane alignment and cube texture of NiO film, and they showed that the NiO film was cube textured. The integrated intensity ratio of NiO I(2 0 0)/{I(2 0 0) + I(1 1 1)} was more than 99%, and the in-plane and out of plane full width at half maximum (FWHM) of the NiO buffer layer were 6.8° and 6.6°, respectively. Yttria-stabilized zirconia (YSZ) as a barrier layer and CeO 2 as a cap one were deposited by pulsed laser deposition (PLD), and YBa 2Cu 3O 7- x (YBCO) layer was prepared on them by PLD as well. YBCO superconducting layer with critical temperature ( Tc)>88 K and critical current density ( Jc)>4×10 5 A/cm 2 (77 K, 0 T) has been obtained successfully on Ni tape with a textured NiO seed layer.

  14. Epitaxial YSZ/CeO 2 and YBCO on cube textured nickel

    NASA Astrophysics Data System (ADS)

    Yang, Jian; Shi, Dongqi; Wang, Xiaohua; Liu, Ansheng; Yuan, Guansen

    2000-07-01

    The YBa 2Cu 3O 7- x (YBCO) superconducting films deposited on the polycrystal metallic substrates by using the rolling assisted biaxially textured substrates (RABiTS) method is reported in this paper. The sharp cube texture in Ni was produced by cold-rolling and recrystallization. The CeO 2 and yttria-stabilized-zirconia (YSZ) films were fabricated by magnetron sputtering technique using plane target. Ar and H 2 were used as sputtering gas while CeO 2 film was deposited. If the pressure of hydrogen is appropriate, NiO can be inhibited while CeO 2 is stable. The full width half maximum (FWHM) of the φ-scan of CeO 2 (220) is 11°, showing a good in-plane orientation. Using Ar and O 2 sputtering gas YSZ film was deposited. The FWHM of the φ-scan of YSZ (220) is 15°. The conditions of both CeO 2 and YSZ films grown on Ni substrates are more severe than those on single crystal substrates. YBCO film was deposited on YSZ/CeO 2/Ni by using cylinder target in a dc magnetron sputtering system. The transport Jc (77 K, 0 T) was 6×10 5 A/cm 2. The microstructure of the deposited films was observed by scanning electron microscopy (SEM) and Auger electron spectrum (AES).

  15. Test Status for Proposed Coupling of a Gravitational Force to Extreme Type II YBCO Ceramic Superconductors

    NASA Technical Reports Server (NTRS)

    Noever, David; Li, Ning; Robertson, Tony; Koczor, Ron; Brantley, Whitt

    1999-01-01

    As a Bose condensate, superconductors provide novel conditions for revisiting previously proposed couplings between electromagnetism and gravity. Strong variations in Cooper pair electron density, large conductivity and low magnetic permeability define superconductive and degenerate condensates without the traditional density limits imposed by the Fermi energy (about 10-6 g/cu cm). Recent experiments have reported anomalous weight loss for a test mass suspended above a rotating Type II, YBCO superconductor, with the percentage change (0.05-2.1%) independent of the test mass' chemical composition and diamagnetic properties. A variation of 5 parts per 10(exp 4) was reported above a stationary (non-rotating) superconductor. In the present experiments reported using a sensitive gravimeter (resolution <10(exp -9) unit gravity or variation of 10(exp -6) cm/sq s in accelerations), bulk YBCO superconductors were stably levitated in a DC magnetic field (0.6 Tesla) subject to lateral AC fields (60 Gauss at 60 Hz) and rotation. With magnetic shielding, thermal control and buoyancy compensation, changes in acceleration were measured to be less than 2 parts in 10(exp 8) of the normal gravitational acceleration. This result puts new limits on the strength and range of the proposed coupling between high-Tc superconductors and gravity. Latest test results will be reported, along with status for future improvements and prospects.

  16. Inkjet printing of multifilamentary YBCO for low AC loss coated conductors

    NASA Astrophysics Data System (ADS)

    Hopkins, S. C.; Joseph, D.; Mitchell-Williams, T. B.; Calleja, A.; Vlad, V. R.; Vilardell, M.; Ricart, S.; Granados, X.; Puig, T.; Obradors, X.; Usoskin, A.; Falter, M.; Bäcker, M.; Glowacki, B. A.

    2014-05-01

    Considerable progress has been made with the development of REBCO coated conductors in recent years, and high performance conductors are available commercially. For many applications, however, the cost remains prohibitive, and AC losses discourage their selection for higher frequency applications. Chemical solution deposition (CSD) methods are attractive for low-cost, scalable preparation of buffer and superconductor layers, and in many respects inkjet printing is the method of choice, permitting non-contact deposition with minimal materials wastage and excellent control of coating thickness. Highly textured coatings of YBCO and Gd-doped CeO2 have previously been reported on buffered metal substrates. Inkjet printing also introduces the possibility of patterning - directly depositing two and three dimensional structures without subtractive processing - offering a low-cost route to coated conductors with reduced AC losses. In this contribution, the inkjet deposition of superconducting YBCO tracks is reported on industrially relevant buffered metal substrates both by direct printing and an inverse patterning approach. In the latter approach, ceria tracks were printed reported, which are a candidate both for resistive filament spacers and buffer layers. TFA-based precursor solutions have been printed on SS/ABAD-YSZ/CeO2 and Ni-W/LZO/CeO2 RABiTS substrates, and the resulting multifilamentary samples characterised by microscopy and scanning Hall probe measurements. The prospects for future inkjet-printed low AC loss coated conductors are discussed, including control of interfilamentary resistivity and bridging, transposed filamentary structures and stabilisation material.

  17. ARPES study of the YBCO phase diagram by in-situ K evaporation

    NASA Astrophysics Data System (ADS)

    Fournier, D.; Levy, G.; McCheyney, J. L.; Bostwick, A.; Rotenberg, E.; Hardy, W. N.; Liang, R. X.; Bonn, D. A.; Elfimov, I. S.; Damascelli, A.

    2010-03-01

    The study of the YBCO phase diagram by ARPES has become of central interest since the observation of quantum oscillations in high-magnetic field [1]. However, until recently accessing the various electronic phases by photoemission has been hampered by the so-called polar catastrophe [2]. In this work, the overdoped metal (OD, p=0.37, Tc=0), the superconducting phase (OP, TYBCO, we are able to identify the doping value at which the Luttinger description breaks down upon underdoping.[1] N. Doiron-Leyraud et al., Nature 447, 565 (2007).[2] M. A. Hossain et al., Nat. Phys. 4, 527 (2008).[3] K. M. Shen et al., Science 307, 901 (2005).

  18. Preparation of YBCO single-crystal surfaces for angularly resolved planar tunneling studies

    NASA Astrophysics Data System (ADS)

    Lussier, Benoit; Charalambous, M.; Guillou, H.; Chaussy, J.; Lejay, P.; Pissas, M.

    1998-03-01

    For BCS superconductors, tunneling has proven to be a valuable tool. Indeed, using multiple recrystallisation techniques, planar junctions could be prepared along various crystalline directions enabling a direct mapping of the superconducting gap. For various reasons, such techniques are difficult (if not impossible) to apply to high-Tc materials. Furthermore, due to the small thickness of the single crystals, very few planar tunneling results into the basal plane are availlable. We present a new sample preparation technique which enables us to prepare surfaces for planar tunneling in any direction in the basal plane. After proper orientation of the high-Tc single crystal, the surface is mechanically polished using fine diamond paste. Such process routinely yields samples with rms surface roughness as low as 15ÅThe sample is then ion-polished with normal incidence xenon atoms and the tunneling barrier and counter-electrode are evaporated in-situ. Preliminary tunneling results for Au/YBCO and Nb/YBCO will be presented for twinned single crystals with tunneling in the (100) and (110) directions.

  19. YBCO microwave grain boundary mixer using a SrTiO[sub 3] bicrystal substrate

    SciTech Connect

    Seed, R.G.; Dorsey, P.C.; How, H.; Widom, A.; Vittoria, C. )

    1993-11-01

    A microwave mixer was patterned on a microstrip transmission line of superconducting YBCO (YBa[sub 2]Cu[sub 3]O[sub 7[minus]x]). The YBCO film was epitaxially laser deposited on a SrTiO[sub 3] bicrystal substrate. A weak link was constructed by patterning a microbridge In the microstrip at the bicrystal boundary. Two microwave signals were applied at the input of the microstrip line, one signal at 9.000 GM and the other signal at 9.941 GHz. An output intermediate frequency signal was observed at 941 MHz and was detected as the transmitted signal. The microbridge junction, which behaved as a resistively shunted Josephson junction (RSJ), was current biased slightly above the critical current I[sub c]. The mixer conversion loss was measured at the input and output ports of the device package. With these measurements, the mixing efficiency was determined at the device junction, and this measured efficiency was compared with the calculated efficiency. The calculated efficiency was determined by numerical solution of the Josephson equation for the weak link junction.

  20. YBCO hot-electron bolometers dedicated to THz detection and imaging: Embedding issues

    NASA Astrophysics Data System (ADS)

    Aurino, M.; Kreisler, A. J.; Türer, I.; Martinez, A.; Gensbittel, A.; Dégardin, A. F.

    2010-06-01

    High-Tc hot-electron bolometers (HEB) are an interesting alternative to other superconducting heterodyne mixers in the terahertz frequency range because of low-cost cooling investment, ultra-wide instantaneous bandwidth and low intrinsic noise level, even at 80 K. A technological process to fabricate stacked yttrium-based (YBCO) / praseodymium-based (PBCO) ultra-thin films (in the 15 to 40 nm thickness range) etched to form 0.5 μm × 0.5 μm constrictions, elaborated on (100) MgO substrates, has been previously described. Ageing effects were also considered, with the consequence of increased electrical resistance, significant degradation of the regular THz response and no HEB mixing action. Electron and UV lithography steps are revisited here to realize HEB mixers based on nano-bridges covered by a log-periodic planar gold antenna, dedicated to the 1 to 7 THz range. Several measures have been attempted to reduce the conversion losses, mainly by considering the embedding issues related to the YBCO nano-bridge impedance matching to the antenna and the design of optimized intermediate frequency circuitry. Antenna simulations were performed and validated through experiments on scaled models at GHz frequencies. Electromagnetic coupling to the incoming radiation was also studied, including crosstalk between neighbour antennas forming a linear imaging array.

  1. Remarkable weakness against cleavage stress for YBCO-coated conductors and its effect on the YBCO coil performance

    NASA Astrophysics Data System (ADS)

    Yanagisawa, Y.; Nakagome, H.; Takematsu, T.; Takao, T.; Sato, N.; Takahashi, M.; Maeda, H.

    2011-08-01

    Cleavage strength for an YBCO-coated conductor at 77 K was investigated with a model experiment. The nominal cleavage strength for an YBCO-coated conductor is extremely low, typically 0.5 MPa. This low nominal cleavage strength is due to stress concentration on a small part of the YBCO-coated conductor in cleavage fracture. Debonding by the cleavage stress occurs at the interface between the buffer layer and the Hastelloy substrate. The nominal cleavage strength for a slit edge of the conductor is 2.5-times lower than that for the original edge of the conductor; cracks and micro-peel existing over the slit edge reduce the cleavage strength for the slit edge. Cleavage stress and peel stress should be avoided in coil winding, as they easily delaminate the YBCO-coated conductor, resulting in substantial degradation of coil performance. These problems are especially important for epoxy impregnated YBCO-coated conductor coils. It appears that effect of cleavage stress and peel stress are mostly negligible for paraffin impregnated YBCO-coated conductor coils or dry wound YBCO-coated conductor coils.

  2. Probes for investigating the effect of magnetic field, field orientation, temperature and strain on the critical current density of anisotropic high-temperature superconducting tapes in a split-pair 15 T horizontal magnet

    NASA Astrophysics Data System (ADS)

    Sunwong, P.; Higgins, J. S.; Hampshire, D. P.

    2014-06-01

    We present the designs of probes for making critical current density (Jc) measurements on anisotropic high-temperature superconducting tapes as a function of field, field orientation, temperature and strain in our 40 mm bore, split-pair 15 T horizontal magnet. Emphasis is placed on the design of three components: the vapour-cooled current leads, the variable temperature enclosure, and the springboard-shaped bending beam sample holder. The vapour-cooled brass critical-current leads used superconducting tapes and in operation ran hot with a duty cycle (D) of ˜0.2. This work provides formulae for optimising cryogenic consumption and calculating cryogenic boil-off, associated with current leads used to make Jc measurements, made by uniformly ramping the current up to a maximum current (Imax) and then reducing the current very quickly to zero. They include consideration of the effects of duty cycle, static helium boil-off from the magnet and Dewar (b'), and the maximum safe temperature for the critical-current leads (Tmax). Our optimized critical-current leads have a boil-off that is about 30% less than leads optimized for magnet operation at the same maximum current. Numerical calculations show that the optimum cross-sectional area (A) for each current lead can be parameterized by LI_{max} /A = [1.46D^{ - 0.18} L^{0.4} (T_{max } - 300)^{0.25D^{ - 0.09} } + 750(b^' /I_{max })D^{10^{ - 3} I_{max } - 2.87b^' }] × 10^6 A m^{ - 1} where L is the current lead's length and the current lead is operated in liquid helium. An optimum A of 132 mm2 is obtained when Imax = 1000 A, Tmax = 400 K, D = 0.2, b' = 0.3 l h-1 and L = 1.0 m. The optimized helium consumption was found to be 0.7 l h-1. When the static boil-off is small, optimized leads have a boil-off that can be roughly parameterized by: b/Imax ≈ (1.35 × 10-3)D0.41 l h-1 A-1. A split-current-lead design is employed to minimize the rotation of the probes during the high current measurements in our high-field horizontal

  3. A concrete realization of specific heat-phonon spectrum inversion for YBCO

    NASA Astrophysics Data System (ADS)

    XianXi, Dai; Wen, Tao; Ma, GuiCun; Dai, JiXin

    1999-12-01

    In this Letter, a phonon spectrum of YBCO is obtained from its experimental specific heat data by an exact inversion formula with eliminating divergence parameter [Dai Xianxi, Xu Xinwen and Dai Jiqiong, Proceedings of Beijing International Conference on High Tc Superconductivity, Sept. 4-8 Beijing, China, (1989) 521], [Dai Xianxi, Xu Xinwen and Dai Jiqiong, Phys. Lett. A 147 (1990) 445]. The results are comparable to that from neutron inelastic scattering. Some key points of specific heat-phonon spectrum inversion (SPI) theory as well as a method of asymptotic behavior control are discussed. An improved unique existence theorem is presented. A universal function set for the numerical calculation in SPI is obtained, which will make the inversion method applicable and convenient in practice. This is the first time to realize the specific heat-phonon spectrum inversion in a concrete system.

  4. Grain boundary degradation of YBCO superconductors sintered in CO{sub 2}-containing atmospheres

    SciTech Connect

    Balachandran, U.; Merkle, K.L.; Mundy, J.N.; Gao, Y.; Zhang, C.; Xu, D.; Selvaduray, G.

    1993-11-01

    The transport critical current density (J{sub c}) of YBCO superconductors decreased with increasing CO{sub 2} partial pressure in the sintering atmosphere and ultimately reached zero, even though magnetization measurements showed that the bulk of the samples with zero J{sub c} remained superconducting. The microstructure and composition of the samples was investigated by high resolution transmission electron microscopy and secondary-ion mass spectroscopy (SIMS). Microbeam SIMS indicated carbon segregation at grain boundaries (GBs). Approximately 10% of the GBs were coated with a thin layer of a second phase, deduced to be BaCuO{sub 2} and BaCu{sub 2}O{sub 2}. Near some grain boundaries, the structure was tetragonal within several tens of nm of the boundaries. The degradation of J{sub c} is discussed in terms of the partial pressure of CO{sub 2} and the processing temperatures. Detailed examination of GB microstructures is given in this paper.

  5. Scanning hall probe microscopy of AC losses in YBCO coated conductors

    NASA Astrophysics Data System (ADS)

    Dinner, Rafael; Daniels, George; Larbalestier, David; Gibbons, Brady; Matias, Vladimir; Moler, Kathryn; Beasley, Malcolm

    2005-03-01

    Magnetic imaging of current-induced vortex movement in superconducting films yields detailed information about dissipation and the path of an applied current. In our large-area scanning hall probe microscope, a flow cryostat cools a sample while a micro-Hall probe is rastered near its surface using a 3-axis stepper-motor-based stage with submicron resolution and centimeter scan range. Hall probe time traces taken at each point are assembled into movies of the flux penetration as a function of time over a cycle of AC sample current. YBCO films grown on several substrates are examined, including bicrystal substrates that induce a single grain boundary across the current path and metal tapes that give rise to a grain boundary network. An extended Bean model allows us to extract pinning forces and critical currents of the intragrain film and its grain boundaries.

  6. Magnetic levitation and its application for education devices based on YBCO bulk superconductors

    NASA Astrophysics Data System (ADS)

    Yang, W. M.; Chao, X. X.; Guo, F. X.; Li, J. W.; Chen, S. L.

    2013-10-01

    A small superconducting maglev propeller system, a small spacecraft model suspending and moving around a terrestrial globe, several small maglev vehicle models and a magnetic circuit converter have been designed and constructed. The track was paved by NdFeB magnets, the arrangement of the magnets made us easy to get a uniform distribution of magnetic field along the length direction of the track and a high magnetic field gradient in the lateral direction. When the YBCO bulks mounted inside the vehicle models or spacecraft model was field cooled to LN2 temperature at a certain distance away from the track, they could be automatically floating over and moving along the track without any obvious friction. The models can be used as experimental or demonstration devices for the magnetic levitation applications.

  7. The Charging Effect in High-T sub c Superconducting Thin Films

    DTIC Science & Technology

    1994-01-01

    fabricate superconducting, MOSFET-like, structures ( SuperFETs ) with the thick, partially oxygen-depleted YBCO channel and fully superconducting source and...drain electrodes. 3. The third objective of this research was to observe the free-carrier density modulation in SuperFET test devices, including a...properties of SuperFETs with different dielectric gates. 5. The fifth objective of this research was to extend our results and investigate "transient

  8. Numerical simulation and analysis of single grain YBCO processed from graded precursor powders

    NASA Astrophysics Data System (ADS)

    Zou, J.; Ainslie, M. D.; Hu, D.; Zhai, W.; Devendra Kumar, N.; Durrell, J. H.; Shi, Y.-H.; Cardwell, D. A.

    2015-03-01

    Large single-grain bulk high-temperature superconducting materials can trap high magnetic fields in comparison with conventional permanent magnets, making them ideal candidates to develop more compact and efficient devices, such as actuators, magnetic levitation systems, flywheel energy storage systems and electric machines. However, macro-segregation of Y-211 inclusions in melt processed Y-Ba-Cu-O (YBCO) limits the macroscopic critical current density Jc of such bulk superconductors, and hence, the potential trapped field. Recently, a new fabrication technique with graded precursor powders has been developed, which results in a more uniform distribution of Y-211 particles, in order to further improve the superconducting properties of such materials. In order to develop this graded fabrication technique further, a 3D finite-element numerical simulation based on the H-formulation is performed in this paper. The trapped field characteristics of a graded YBCO sample magnetized by the field cooling method are simulated to validate the model, and the simulation results are consistent with the experimental measurements. In addition, the influence of the graded technique and various graded Jc distributions for pulsed field magnetization, recognized widely as a practical route for magnetizing samples in bulk superconductor applications, is also investigated, with respect to the trapped field and temperature profiles of graded samples. This modelling framework provides a new technique for assessing the performance of various sizes and geometries of graded bulk superconductors, and by adjusting the Y-211, and hence Jc, distribution, samples can be fabricated based on this concept to provide application-specific trapped field profiles, such as the generation of either a high magnetic field gradient or a high level of uniformity for the traditionally conical, trapped field profile.

  9. Processing of YBCO superconductors for improved levitation force

    SciTech Connect

    Balachandran, U.; Zhong, W.

    1993-05-01

    One objective of the ANL superconductor program is to develop improved processing methods for production of YBCO superconductors with higher levitation forces suitable for low-friction, superconductor/permanent-magnet bearings and flywheel-energy-storage applications. From the standpoint of these applications, melt-processed bulk YBCO superconductors are of considerable interest. Levitation force and flux-pinning properties depend on microstructural features of the superconductors. We have added several chemical species to YBCO to alter the microstructure and have used a seeding technique to induce crystallization during melt processing. In this paper, we discuss the effects of various process parameters, additives, and a seeding technique on the properties of melt-processed bulk YBCO samples and compare the results with solid-state-sintered superconductors.

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

    NASA Astrophysics Data System (ADS)

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

    2013-11-01

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

  11. Fabrication of Filamentary YBCO Coated Conductor by Inkjet Printing

    SciTech Connect

    List III, Frederick Alyious; Kodenkandath, Thomas; Rupich, Marty

    2007-01-01

    Inkjet printing is a potentially low cost, high rate method for depositing precursors for filamentary YBCO coated conductors. The method offers considerable flexibility of filament pattern, width, and thickness. Using standard solution precursors and RABiTSTM substrates, the printing, processing, and properties of some inkjet-derived filamentary YBCO coated conductors for Second Generation (2G) wire are demonstrated on a laboratory scale. Some systematic variations of growth rate and critical transport current with filament width are observed and discussed.

  12. Fabrication and Characterization of Ultrathin PBCO/YBCO/PBCO Constrictions for Hot Electron Bolometer THz Mixing Application

    NASA Astrophysics Data System (ADS)

    Peroz, Christophe; Degardin, Annick F.; Villegier, Jean-Claude; Kreisler, Alain J.

    2007-06-01

    Superconducting Hot Electron Bolometer (HEB) mixers are a competitive alternative to conventional mixer technologies in the terahertz range because of their ultrawide bandwidth, high conversion gain, and low intrinsic noise level, even at 77 K. A technological process to realize HEBs based on high-Tc YBa2Cu3O7-delta (YBCO) materials is described. Ultra-thin 12 to 40 nm layers were sputtered on MgO (100) substrates, sub-micrometer constrictions (0.5 mum times 0.5 mum) were etched on these and log-periodic gold antennas were then integrated. Good superconducting properties were measured after the whole process. Electrical transport characteristics of the device are discussed, aging effects are considered and regular bolometric THz response results are given.

  13. Scientific Presentations on Superconductivity from 2002-2005

    DTIC Science & Technology

    2006-01-01

    homopolar and synchronous superconducting motors to drive the US Navy’s future all-electric ship. HTS wire technology can be used in many of the system...components for these military applications such as motors , power generators, transformers, power converters/inductors, primary power cabling, and high...capability for the YBCO conductor leads to commercialization in electric power applications such as transformers, transmission cables, motors , fault

  14. High Tc superconducting bolometric and nonbolometric infrared (IR) detectors

    NASA Technical Reports Server (NTRS)

    Lakeou, Samuel

    1995-01-01

    Activities carried out during the reporting period are summarized. The workplan for the period August 1994 to August 1995 included the following: (1) expansion of the Applied Superconductivity Laboratory to include stand-alone optical response and noise measurement setups; (2) study the low frequency excess electrical noise in YBCO films; and (3) enhancement of the academic support component of the project through increased student and faculty participation. Abstracts of papers submitted for publication during this reporting period are included as attachments.

  15. Microstructural mechanism for attenuation of superconductivity in manganite/cuprate thin-film heterostructures

    NASA Astrophysics Data System (ADS)

    Wei, J. Y. T.; Zhang, H.; Gauquelin, N.; Botton, G. A.

    2014-03-01

    Anomalously long-ranged proximity effects have recently been reported in manganite/cuprate heterostructures, and attributed to spin-triplet correlations for odd-frequency pairing. To elucidate this exotic scenario microscopically, we studied multilayer La2 / 3Ca1 / 3MnO3 /YBa2Cu3O7 - δ (LCMO/YBCO) thin films using scanning transmission electron microscopy (STEM), x-ray diffraction (XRD) and electrical transport. The atomic-scale STEM data revealed double CuO-chain intergrowths which effectively form regions with the 247 lattice structure in the YBCO layer. These nanoscale 247 regions do not show up in XRD, but can physically account for the reduction in superconducting critical temperature (Tc) as a function of YBCO thickness. We also observed similar Tc reduction in LaNiO3 / YBCO heterostructures, where LaNiO3 is also epitaxially-matched with YBCO but is not ferromagnetic. These results suggest that microstructural defects, rather than magnetism, are responsible for the attenuation of superconductivity occuring in manganite/cuprate heterostructures. Work supported by NSERC, CFI/OIT, and the Canadian Institute for Advanced Research.

  16. 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.

  17. Anisotropic universe with anisotropic sources

    SciTech Connect

    Aluri, Pavan K.; Panda, Sukanta; Sharma, Manabendra; Thakur, Snigdha E-mail: sukanta@iiserb.ac.in E-mail: snigdha@iiserb.ac.in

    2013-12-01

    We analyze the state space of a Bianchi-I universe with anisotropic sources. Here we consider an extended state space which includes null geodesics in this background. The evolution equations for all the state observables are derived. Dynamical systems approach is used to study the evolution of these equations. The asymptotic stable fixed points for all the evolution equations are found. We also check our analytic results with numerical analysis of these dynamical equations. The evolution of the state observables are studied both in cosmic time and using a dimensionless time variable. Then we repeat the same analysis with a more realistic scenario, adding the isotropic (dust like dark) matter and a cosmological constant (dark energy) to our anisotropic sources, to study their co-evolution. The universe now approaches a de Sitter space asymptotically dominated by the cosmological constant. The cosmic microwave background anisotropy maps due to shear are also generated in this scenario, assuming that the universe contains anisotropic matter along with the usual (dark) matter and vacuum (dark) energy since decoupling. We find that they contribute dominantly to the CMB quadrupole. We also constrain the current level of anisotropy and also search for any cosmic preferred axis present in the data. We use the Union 2 Supernovae data to this extent. An anisotropy axis close to the mirror symmetry axis seen in the cosmic microwave background data from Planck probe is found.

  18. Superconductivity program for electric systems, Superconductivity Technology Center, Los Alamos National Laboratory, annual progress report for fiscal year 1997

    SciTech Connect

    Willis, J.O.; Newnam, B.E.; Peterson, D.E.

    1999-03-01

    Development of high-temperature superconductors (HTS) has undergone tremendous progress during the past year. Kilometer tape lengths and associated magnets based on BSCCO materials are now commercially available from several industrial partners. Superconducting properties in the exciting YBCO coated conductors continue to be improved over longer lengths. The Superconducting Partnership Initiative (SPI) projects to develop HTS fault current limiters and transmission cables have demonstrated that HTS prototype applications can be produced successfully with properties appropriate for commercial applications. Research and development activities at LANL related to the HTS program for Fiscal Year 1997 are collected in this report. LANL continues to support further development of Bi2223 and Bi2212 tapes in collaboration with American Superconductor Corporation (ASC) and Oxford Superconductivity Technology, Inc. (OSTI), respectively. The tape processing studies involving novel thermal treatments and microstructural characterization have assisted these companies in commercializing these materials. The research on second-generation YBCO-coated conductors produced by pulsed-laser deposition (PLD) over buffer template layers produced by ion beam-assisted deposition (IBAD) continues to lead the world. The applied physics studies of magnetic flux pinning by proton and heavy ion bombardment of BSCCO and YBCO tapes have provided many insights into improving the behavior of these materials in magnetic fields. Sections 4 to 7 of this report contain a list of 29 referred publications and 15 conference abstracts, a list of patent and license activities, and a comprehensive list of collaborative agreements in progress and completed.

  19. Fluctuation-induced anisotropic magnetoconductivity in oxygen-deficient YBa 2Cu 3O 7-δthin films

    NASA Astrophysics Data System (ADS)

    Göb, W.; Lang, W.; Kula, W.; Sobolewski, Roman

    1997-04-01

    We report on measurements of both the longitudinal and transverse magnetoresistivity (MR) of oxygen-reduced YBa2Cu3O7-δ(YBCO) thin films with critical temperatures betweenTc = 55 K andTc = 89 . We find the MR solely caused by the suppression of superconducting fluctuations by a magnetic field. In fully oxygenated samples both the Aslamazov-Larkin process (AL) and another, presumably the Maki-Thompson process (MT), contribute to the MR. In oxygen-deficient samples the MT process unambiguously is absent, thus indicating an unconventional (non-s-wave) pairing symmetry in YBCO.

  20. Growth and barium zirconium oxide doping study on superconducting M-barium copper oxide (M = yttrium, samarium) films using a fluorine-free metal organic decomposition process

    NASA Astrophysics Data System (ADS)

    Lu, Feng

    We present a fluorine-free metal organic deposition (F-free MOD) process - which is possibly a rapid and economic alternative to commercial trifluoroacetates metal organic deposition (TFA-MOD) and metal organic chemical vapor deposition (MOCVD) processes - for the fabrication of high quality epitaxial high temperature superconducting YBa2Cu3O7-x (YBCO) films on both Rolling-Assisted Biaxially Textured Substrates (RABiTS) and single crystal substrates. We first studied the growth of YBCO and SmBCO films, and their resulting microstructure and superconducting properties. We produced epitaxial c-axis YBCO films with high critical current density (Jc) in excess of 106 A/cm2 at 77K in self field at the thickness of ˜1 mum. Because industrial applications demand high quality YBCO films with very high Jc, we investigated introducing BaZrO3 (BZO) nano-pinning sites in HTS thin films by our F-free MOD technique to improve Jc and the global pinning force (Fp). BZO-doped YBCO films were fabricated by adding extra Ba and Zr in the precursor solutions, according to the molar formula 1 YBCO + x BZO. We found the BZO content affects the growth of YBCO films and determined the optimum BZO content which leads to the most effective pinning enhancement and the least YBCO degradation. We achieved the maximum pinning force of ˜ 10 GN/m3 for x = 0.10 BZO-doped, 200 nm thick YBCO film on SrTiO3 single crystal substrates by modifying the pyrolysis from a one-step to a two-plateau decomposition during the F-free MOD process. For growing optimum BZO-doped YBCO films on RABiTS substrates, the F-free MOD process was also optimized by adjusting the maximum growth temperature and growth time to achieve stronger pinning forces. Through-process quenching studies indicate that BZO form 10--25 nm nanoparticles at the early stage of the process and are stable during the following YBCO growth, demonstrating that chemically doping YBCO films with BZO using the F-free MOD process is a very effective

  1. Contribution of ion beam analysis methods to the development of second generation high temperature superconducting wires

    NASA Astrophysics Data System (ADS)

    Usov, I. O.; Arendt, P. N.; Foltyn, S. R.; Stan, L.; DePaula, R. F.; Holesinger, T. G.

    2010-06-01

    One of the crucial steps in the second generation high temperature superconducting wire program was development of the buffer-layer architecture. The architecture designed at the Superconductivity Technology Center at Los Alamos National Laboratory consists of several oxide layers wherein each layer plays a specific role, namely: nucleation layer, diffusion barrier, biaxially textured template, and intermediate layer providing a suitable lattice match to the superconducting Y 1Ba 2Cu 3O 7 (YBCO) compound. This report demonstrates how a wide range of ion beam analysis techniques (SIMS, RBS, channeling, PIXE, PIGE, NRA and ERD) was employed for analysis of each buffer layer and the YBCO film. These results assisted in understanding of a variety of physical processes occurring during the buffer layer fabrication and helped to optimize the buffer-layer architecture as a whole.

  2. Voltage-ampere characteristics of YBCO coated conductor under inhomogeneous oscillating magnetic field

    NASA Astrophysics Data System (ADS)

    Geng, J.; Shen, B.; Li, C.; Zhang, H.; Matsuda, K.; Li, J.; Zhang, X.; Coombs, T. A.

    2016-06-01

    Direct current carrying type II superconductors present a dynamic resistance when subjected to an oscillating magnetic field perpendicular to the current direction. If a superconductor is under a homogeneous field with high magnitude, the dynamic resistance value is nearly independent of transport current. Hoffmann and coworkers [Hoffmann et al., IEEE Trans. Appl. Supercond. 21, 1628 (2011)] discovered, however, flux pumping effect when a superconducting tape is under an inhomogeneous field orthogonal to the tape surface generated by rotating magnets. Following their work, we report the whole Voltage-Ampere (V-I) curves of an YBCO coated conductor under permanent magnets rotating with different frequencies and directions. We discovered that the two curves under opposite rotating directions differ from each other constantly when the transport current is less than the critical current, whereas the difference gradually reduces after the transport current exceeds the critical value. We also find that for different field frequencies, the difference between the two curves decreases faster with lower field frequency. The result indicates that the transport loss is dependent on the relative direction of the transport current and field travelling, which is distinct from traditional dynamic resistance model. The work may be instructive for the design of superconducting motors.

  3. Superconductive wire

    DOEpatents

    Korzekwa, David A.; Bingert, John F.; Peterson, Dean E.; Sheinberg, Haskell

    1995-01-01

    A superconductive article is made by inserting a rigid mandrel into an internal cavity of a first metallic tube, said tube having an interior surface and an exterior surface, said interior surface defining the interior cavity, forming a layer of a superconductive material or superconductive precursor upon the exterior surface of said first metallic tube, machining the layer of superconductive material or superconductive precursor to a predetermined diameter to form an intermediate article configured for insertion into a second metallic tube having an interior diameter corresponding to the predetermined diameter, inserting the machined intermediate article into a second metallic tube having an internal diameter corresponding to the predetermined diameter of the intermediate article to form a composite intermediate article, reducing or ironing the composite intermediate article to a predetermined cross-sectional diameter, and sintering the reduced or ironed composite intermediate article at temperatures and for time sufficient for the superconductive material or superconductive precursor to exhibit superconductivity.

  4. Superconductive wire

    DOEpatents

    Korzekwa, D.A.; Bingert, J.F.; Peterson, D.E.; Sheinberg, H.

    1995-07-18

    A superconductive article is made by inserting a rigid mandrel into an internal cavity of a first metallic tube, said tube having an interior surface and an exterior surface, said interior surface defining the interior cavity, forming a layer of a superconductive material or superconductive precursor upon the exterior surface of said first metallic tube, machining the layer of superconductive material or superconductive precursor to a predetermined diameter to form an intermediate article configured for insertion into a second metallic tube having an interior diameter corresponding to the predetermined diameter, inserting the machined intermediate article into a second metallic tube having an internal diameter corresponding to the predetermined diameter of the intermediate article to form a composite intermediate article, reducing or ironing the composite intermediate article to a predetermined cross-sectional diameter, and sintering the reduced or ironed composite intermediate article at temperatures and for time sufficient for the superconductive material or superconductive precursor to exhibit superconductivity. 2 figs.

  5. Superconducting fault current limiter with bulk materials

    NASA Astrophysics Data System (ADS)

    Tixador, P.; Buzon, D.; Floch, E.; Porcar, L.; Isfort, D.; Chaud, X.; Tournier, R.; Bourgault, D.; Barbut, J. M.; Bach, J.

    2002-10-01

    Superconducting materials offer the unique possibility to limit fault currents by their self-triggering quench to a resistive state above a given threshold current. Their use in power networks would improve the power quality, which is a real need today. YBCO or BSCO bulk materials are good candidates for current limitation. Their behaviours are rather different, in particular the electric field versus current characteristics. BSCO compounds are protected by their homogeneous quench due to the numerous defects (grain boundaries) distributed along the material. An assembling of 60 sintered Bi bars was tested under 1 kV. The current limitation is effective (a 5000 A short-circuit has been limited to 1080 A) but it occurs at 24 times the critical current. The increase of the critical current density of Bi compounds by their texturation reduces the current excursion above the critical value. In YBCO bulk elements, the defects are localized and make YBCO very sensitive to hot spots. Those are unavoidable and the operating conditions should be adapted in order to make them non-destructive. That is the self-protection concept. To fulfil it, we chose to operate near the critical temperature (above 90 K) to reduce the critical current density. The small difference with Tc is very favourable for the quench. A fault current limiter based on 43 YBCO meanders working at 90.5 K in a pressurized liquid nitrogen bath is presented. The meanders are cut in 45 mm in diameter single domain pellets elaborated using the top-seeding technique. Supplied under a maximum voltage of 1 kV, the current was limited at 740 A instead of the theoretical value of 6500 A without quench.

  6. Transmission Level High Temperature Superconducting Fault Current Limiter

    SciTech Connect

    Stewart, Gary

    2016-10-05

    The primary objective of this project was to demonstrate the feasibility and reliability of utilizing high-temperature superconducting (HTS) materials in a Transmission Level Superconducting Fault Current Limiter (SFCL) application. During the project, the type of high-temperature superconducting material used evolved from 1st generation (1G) BSCCO-2212 melt cast bulk high-temperature superconductors to 2nd generation (2G) YBCO-based high-temperature superconducting tape. The SFCL employed SuperPower's “Matrix” technology, that offers modular features to enable scale up to transmission voltage levels. The SFCL consists of individual modules that contain elements and parallel inductors that assist in carrying the current during the fault. A number of these modules are arranged in an m x n array to form the current-limiting matrix.

  7. Superconducting transistor

    DOEpatents

    Gray, Kenneth E.

    1979-01-01

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

  8. Developments of high- Tc superconducting current feeders for a large-scale superconducting coil system

    NASA Astrophysics Data System (ADS)

    Mito, T.; Maehata, K.; Mizokami, M.; Ishibashi, K.; Takeo, M.; Iwamoto, A.; Hirano, N.; Shintomi, T.; Kimura, K.; Sawamura, M.; Yamada, S.; Satoh, S.; Motojima, O.

    1998-10-01

    A large-scale superconducting coil system, which is an essential technology for a fusion reactor, requires large capacity and high performance current feeders from the power supplies at the room temperature to the superconducting coils at the operating temperature, which is usually liquid helium temperature at present. The superconducting current feeders are being considered as a promising application of a high temperature superconductor (HTS), which can satisfy the requirements of a large current capacity and a low heat in-leak, simultaneously. To study the feasibility of the HTS current feeders, a melt-textured YBCO bulk superconductor was selected as a candidate material because of its high current transport characteristics. The YBCO disk fabricated by quench and melt growth process was cut into a short sample with the cross section of 7 mm × 7 mm and the length of 40 mm and was mounted on the copper bars to perform the actual large current transport tests. The sample could be successfully excited up to 20 kA at 4.2 K and 10 kA at 77 K. These performance test results and the further R&D items for the HTS current feeders are discussed.

  9. STANFORD IN-SITU HIGH RATE YBCO PROCESS: TRANSFER TO METAL TAPES AND PROCESS SCALE UP

    SciTech Connect

    Malcolm R. Beasley; Robert H.Hammond

    2009-04-14

    Executive Summary The materials science understanding of high rate low cost processes for Coated Conductor will benefit the application to power utilities for low loss energy transportation and power generation as well for DOD applications. The research in this program investigated several materials processing approaches that are new and original, and are not being investigated elsewhere. This work added to the understanding of the material science of high rate PVD growth of HTSC YBCO assisted by a liquid phase. A new process discovered uses amorphous glassy precursors which can be made at high rate under flexible conditions of temperature and oxygen, and later brought to conditions of oxygen partial pressure and temperature for rapid conversion to YBCO superconductor. Good critical current densities were found, but further effort is needed to optimize the vortex pinning using known artificial inclusions. A new discovery of the physics and materials science of vortex pinning in the HTSC system using Sm in place of Y came at growth at unusually low oxygen pressure resulting in clusters of a low or non superconducting phase within the nominal high temperature phase. The driving force for this during growth is new physics, perhaps due to the low oxygen. This has the potential for high current in large magnetic fields at low cost, applicable to motors, generators and transformers. The technical demands of this project were the motivation for the development of instrumentation that could be essential to eventual process scale up. These include atomic absorption based on tunable diode lasers for remote monitoring and control of evaporation sources (developed under DARPA support), and the utility of Fourier Transform Infrared Reflectivity (FTIR) for aid in the synthesis of complex thin film materials (purchased by a DURIP-AFOSR grant).

  10. Fabrication of interface-modified ramp-edge junction on YBCO ground plane with multilayer structure

    NASA Astrophysics Data System (ADS)

    Wakana, H.; Adachi, S.; Kamitani, A.; Sugiyama, H.; Sugano, T.; Horibe, M.; Ishimaru, Y.; Tarutani, Y.; Tanabe, K.

    2003-10-01

    We examined the fabrication conditions to obtain high-quality ramp-edge Josephson junctions on a liquid-phase-epitaxy YBa 2Cu 3O y (LPE-YBCO) ground plane, in particular, focusing on the fabrication of a suitable insulating layer on the ground plane and the post-annealing conditions to load oxygen to the ground plane. A (LaAlO 3) 0.3-(SrAl 0.5Ta 0.5O 3) 0.7 (LSAT) insulating film on the ground planes exhibited a conductance ranging from 10 -4 to 10 -8 S after deposition of an upper superconducting film, suggesting existence of some leak paths through the LSAT insulating layer. By introducing approximately 30 nm thick SrTiO 3 (STO) buffer layers on both side of the LSAT insulating layer. We reproducibly obtained a conductance lower than 10 -8 S. The dielectric constant of the STO/LSAT/STO layer was 32, which was slightly larger than that of the single LSAT layer. It was found that a very slow cooling rate of 1.0 °C/h in oxygen was needed to fully oxidize the ground plane through the STO/LSAT/STO insulating layers, while the oxidation time could be effectively reduced by introducing via holes in the insulating layer at an interval of 200 μm. Ramp-edge junctions on LPE-YBCO ground planes with STO/LSAT/STO insulating layers exhibited a 1 σ-spread in Ic of 8% for 100-junction series-arrays and a sheet inductance of 0.7 pH/□ at 4.2 K.

  11. Particle size effect on the superconducting properties of YBa2Cu3O7-x particles.

    PubMed

    Blanco-Gutiérrez, V; Torralvo-Fernández, M J; Alario-Franco, M Á

    2017-09-12

    YBCO samples with different microstructures were prepared after the thermal treatment of a precursor previously obtained by autocombustion. A drastic influence of the particle size on the magnetic behavior of the samples was observed. Thus, particles smaller than 110 nm do not exhibit superconducting properties and for those ranging around 200 nm the diamagnetic signal characteristic of the superconductivity at low temperature disappears in a large applied magnetic field. Particles larger than 300 nm do not exhibit the particle size effect. Accompanying such a phenomenon, an increase of the superconducting critical temperature is observed with the augmentation of the particle size, the lowest value being 18 K which corresponds to 110 nm particles.

  12. Removal of degradation of the performance of an epoxy impregnated YBCO-coated conductor double pancake coil by using a polyimide-electrodeposited YBCO-coated conductor

    NASA Astrophysics Data System (ADS)

    Yanagisawa, Y.; Sato, K.; Piao, R.; Nakagome, H.; Takematsu, T.; Takao, T.; Kamibayashi, H.; Takahashi, M.; Maeda, H.

    2012-06-01

    Degradation of the epoxy impregnated YBCO coil performance is due to tensile radial stress concentration on the outer edge of the conductor during cool down. This stress acts as a cleavage stress and opens the conductor edge, fracturing the YBCO layer. The fracture propagates to another edge of the conductor, resulting in degradation of the coil performance. Degradation of the epoxy impregnated YBCO coil is eliminated, if we use a polyimide-electrodeposited YBCO-coated conductor: tensile radial stress concentration on the outer edge of the conductor is reduced due to plastic deformation of the ductile polyimide. Polyimide electrodeposition onto the YBCO-coated conductor is reliable, uniform, easy to apply, and can be extended to larger YBCO magnets, removing the risk of coil degradation.

  13. Local Cu and Br environments and their relationship to superconductivity restoration in brominated YBa{sub 2}Cu{sub 3}O{sub y}

    SciTech Connect

    Potrepka, D.M.; Fenner, D.B.; Balasubramanian, M.; Hines, W.A.; Budnick, J.I.

    1998-08-01

    {sup 63,65}Cu nuclear quadrupole resonance (NQR) and Br {ital k}-edge x-ray absorption fine structure (XAFS) have been used to study the local structures in well-characterized samples of deoxygenated and brominated YBa{sub 2}Cu{sub 3}O{sub y}(YBCO). NQR shows that after bromination of YBa{sub 2}Cu{sub 3}O{sub 6.1} at 260thinsp{degree}C, oxygen has repopulated the chain sites. From XAFS, it is concluded that Br does not enter the YBCO lattice, but rather precipitates out as small nanoscale particles of BaBr{sub 2}. These results provide clear evidence of the role of Br in reoxygenating the YBCO structure and an explanation for the partial restoration of superconductivity in the YBCO system. {copyright} {ital 1998 American Institute of Physics.}

  14. Fermi surface of YBCO by DHVA

    SciTech Connect

    Smith, J.L.; Fowler, C.M.; Freeman, B.L.; Hults, W.L.; King, J.C.; Mueller, F.M.

    1991-01-01

    These proceedings demonstrate how far scientist have come in the last four years of high temperature superconductivity. Knowledge of the energy bands and Fermi surfaces from experiment has come rather late. Photoemission, first showed proof of the validity of the energy band calculations. Positron annihilation, presented by West, after a rough start, is now giving evidence of the Fermi surface. Both of these techniques involve electronic excitations and hence, although they show the Fermi surface, do not put as severe a constraint on various models for superconductivity as does the de Haas-van Alphen (dHvA) effect. This is a true measurement of the electronic ground state in an applied magnetic field where the frequency of oscillatory magnetization yields extremal cross-sectional areas of the Fermi surface. The authors have already reported some of their Fermi surface work at two conferences but present here discussion of several more important aspects of the work. 11 refs., 2 figs.

  15. Improving YBCO Coated Conductors for Applications (Postprint)

    DTIC Science & Technology

    2012-02-01

    Dec 2006. 14. ABSTRACT Superconducting power devices made of high temperature superconductors (HTS) can enable megawatt-class power systems which... superconductors (HTS) can enable megawatt-class power systems which are lighter in weight and smaller in size than their conventional counterparts. The... motors , and transformers are being developed to address these power concerns. HTS conductors make the development of these HTS power devices

  16. Superconductivity devices: Commercial use of space

    NASA Technical Reports Server (NTRS)

    Haertling, Gene; Furman, Eugene; Hsi, Chi-Shiung; Li, Guang

    1993-01-01

    The processing and screen printing of the superconducting BSCCO and 123 YBCO materials on substrates is described. The resulting superconducting properties and the use of these materials as possible electrode materials for ferroelectrics at 77 K are evaluated. Also, work performed in the development of solid-state electromechanical actuators is reported. Specific details include the fabrication and processing of high strain PBZT and PLZT electrostrictive materials, the development of PSZT and PMN-based ceramics, and the testing and evaluation of these electrostrictive materials. Finally, the results of studies on a new processing technology for preparing piezoelectric and electrostrictive ceramic materials are summarized. The process involves a high temperature chemical reduction which leads to an internal pre-stressing of the oxide wafer. These reduced and internally biased oxide wafers (RAINBOW) can produce bending-mode actuator devices which possess a factor of ten more displacement and load bearing capacity than present-day benders.

  17. Superconductivity devices: Commercial use of space

    NASA Astrophysics Data System (ADS)

    Haertling, Gene; Furman, Eugene; Hsi, Chi-Shiung; Li, Guang

    1993-09-01

    The processing and screen printing of the superconducting BSCCO and 123 YBCO materials on substrates is described. The resulting superconducting properties and the use of these materials as possible electrode materials for ferroelectrics at 77 K are evaluated. Also, work performed in the development of solid-state electromechanical actuators is reported. Specific details include the fabrication and processing of high strain PBZT and PLZT electrostrictive materials, the development of PSZT and PMN-based ceramics, and the testing and evaluation of these electrostrictive materials. Finally, the results of studies on a new processing technology for preparing piezoelectric and electrostrictive ceramic materials are summarized. The process involves a high temperature chemical reduction which leads to an internal pre-stressing of the oxide wafer. These reduced and internally biased oxide wafers (RAINBOW) can produce bending-mode actuator devices which possess a factor of ten more displacement and load bearing capacity than present-day benders.

  18. Superconductive wire

    SciTech Connect

    Korzekwa, D.A.; Bingert, J.F.; Peterson, D.E.; Sheinberg, H.

    1992-12-31

    This invention is comprised of a superconductive article including a first metallic tube having an interior surface and an exterior surface, said interior surface defining an interior hollow cavity, a layer of superconductive material surrounding said exterior surface of said first metallic tube, and, a second metallic tube having an interior surface and an exterior surface, said interior surface adjacent to said layer of superconductive material is provided together with processes of making such a superconductive article including, e.g., inserting a rigid mandrel into an internal cavity of a first metallic tube, said tube having an interior surface and an exterior surface, said interior surface defining the interior cavity, forming a layer of a superconductive material or superconductive precursor upon the exterior surface of said first metallic tube, machining the layer of superconductive material or superconductive precursor to a predetermined diameter to form an intermediate article configured for insertion into a second metallic tube having an interior diameter corresponding to the predetermined diameter, inserting the machined intermediate article into a second metallic tube having an internal diameter corresponding to the predetermined diameter of the intermediate article to form a composite intermediate article, reducing and/or ironing the composite intermediate article to a predetermined cross-sectional diameter, and sintering the reduced or ironed composite intermediate article at temperatures and for time sufficient for the superconductive material or superconductive precursor to exhibit superconductivity.

  19. Superconducting bolometers: high-Tc and low-Tc

    NASA Astrophysics Data System (ADS)

    Richards, Paul L.

    1991-07-01

    A description is given of recent work at Berkeley on superconducting detectors and mixers for infrared and millimeter wavelengths. The first report is a review article which summarizes the status of development of superconducting components for infrared and millimeter wave receivers. Next, a report is given on measurements and theoretical modeling of the absorptivity (surface resistance) of high quality epitaxial films of the high-Tc superconductor YBCO from 750 GHz to 21 THz. The next report describes measurements of the thermal boundary resistance between YBCO films and various substrates. This resistance is much larger than expected from the acoustic impedance mismatch model and gives a thermal time constant in the nanosecond range for typical YBCO films. Reports are also included on the design and experimental performance of two different types of high-Tc bolometric detectors. One is a conventional bolometer with a gold-black absorber. The other is an antenna coupled microbolometer. The properties of a low-Tc microbolometer are also described. The last reports describe accurate measurements and also theoretical modeling of an SIS quasi-particle waveguide mixer for W-band which uses very high quality Ta junctions. The best mixer noise is only 1.3 times the quantum limit. Both the mixer gain and the noise are in quantitative agreement with the quantum theory.

  20. Correlation of local structure peculiarities and critical current density of 2G MOCVD YBCO tapes with BaZrO3 nanoinclusions

    NASA Astrophysics Data System (ADS)

    Menushenkov, A. P.; Ivanov, V. G.; Chepikov, V. N.; Nygaard, R. R.; Soldatenko, A. V.; Rudnev, I. A.; Osipov, M. A.; Mineev, N. A.; Kaul, A. R.; Mathon, O.; Monteseguro, V.

    2017-04-01

    We have studied the influence of BaZrO3 nanoinclusions on the local structure and critical current density of second-generation high temperature superconducting tapes based on YBa2Cu3O7‑δ (YBCO) films. The films were made by metal–organic chemical vapor deposition (MOCVD). The crystal and local structure of the materials under study were analysed by x-ray diffraction and x-ray absorption spectroscopy (EXAFS + XANES). We have found that, being added at MOCVD process, Zr forms BaZrO3 nanoinclusions in YBCO matrix. The distance between Zr and the neighboring atoms is shorter than that one in a bulk crystalline BaZrO3, so we conclude that the nanoinclusions are in compressed state. The incorporation of 5 mol% BaZrO3 minimizes the static disorder of Cu–O bonds and maximizes their stiffness in YBCO. We show that the local structure peculiarities correlate well with the observed critical current behavior and consider this to be additional evidence in favor of small amounts of BaZrO3 nanoinclusions as efficient pinning centers.

  1. 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.

  2. Thickness-Dependent Properties of YBCO Films Grown on GZO/CLO-Buffered NiW Substrates

    NASA Astrophysics Data System (ADS)

    Malmivirta, M.; Huhtinen, H.; Zhao, Y.; Grivel, J.-C.; Paturi, P.

    2017-01-01

    To study the role of novel Gd_2Zr_2O_7/Ce_{0.9}La_{0.1}O_2 buffer layer structure on a biaxially textured NiW substrate, a set of YBa_2Cu_3O_{7-δ } (YBCO) films with different thicknesses were prepared by pulsed laser deposition (PLD). Interface imperfections as well as thickness-dependent structural properties were observed in the YBCO thin films. The structure is also reflected into the improved superconducting properties with the highest critical current densities in films with intermediate thicknesses. Therefore, it can be concluded that the existing buffer layers need more optimization before they can be successfully used for films with various thicknesses. This issue is linked to the extremely susceptible growth method of PLD when compared to the commonly used chemical deposition methods. Nevertheless, PLD-grown films can give a hint on what to concentrate to be able to further improve the buffer layer structures for future coated conductor technologies.

  3. Pr Doped YBCO Films Produced by Pulsed Laser Deposition (Postprint)

    DTIC Science & Technology

    2012-02-01

    found that the substituent was dispersed throughout the film and led to an increase in nanoparticles. EXPERIMENT Thin films of (Y1-x, Prx )Ba2Cu3O7-d...were produced by PLD using conditions previously optimized for pure YBCO. PLD targets were prepared with the composition (Y1-x, Prx )Ba2Cu3O7- d

  4. Superconducting and semiconducting YBaCuO thin film bolometer investigations for future THz imaging arrays

    NASA Astrophysics Data System (ADS)

    Jagtap, Vishal S.; Dégardin, Annick F.; Longhin, Mattia; Aurino, Mario; Kreisler, Alain J.

    2008-10-01

    There is a strong need for wideband and sensitive THz receivers for radio astronomy and remote sensing applications, for which superconducting Hot Electron Bolometer (HEB) mixers are very competitive. Besides, new THz applications have arisen because of interesting interaction with various media, for which room temperature detectors are highly attractive. We have used YBa2Cu3O7-d (YBCO) oxides to fabricate bolometers, either of high-Tc superconducting HEB type (high oxygen content, δ < 0.3) or semiconducting type (low oxygen content, δ > 0.5). Firstly, we fabricated HEBs made from superconducting YBCO ultrathin films (15 to 40 nm thick) etched to form submicrometer constrictions. In order to investigate the feasibility of highly sensitive HEB linear arrays for passive THz imaging applications, extensive technological runs were performed to prevent ageing effects on both the pixel electrical and optical characteristics. Secondly, we designed YBCO semiconducting bolometric pixels for room temperature operation. Due to the reduced sensitivity and bandwidth with respect to superconducting HEBs, we considered the feasibility of 2D arrays for active THz imaging. As a first experimental step, pixel responsivity and thermal crosstalk between pixels were studied in the 1 Hz to 100 kHz modulation frequency range, so to evaluate the adequate frame refreshing rate.

  5. Microstructure and superconductivity of highly ordered YBa(2)Cu(3)O(7-δ) nanowire arrays.

    PubMed

    Zhang, Genqiang; Lu, Xiaoli; Zhang, Tao; Qu, Jifeng; Wang, Wei; Li, Xiaoguang; Yu, Shuhong

    2006-08-28

    In order to explore the fundamental properties of one-dimensional nanostructured high-temperature superconductors and enhance their promising applications, a universal and general method for the synthesis of high-quality YBa(2)Cu(3)O(7-δ) (YBCO) nanowire arrays is developed, which involves the combination of a novel sol-gel process to lower the crystallization temperature of YBCO, and porous anodic alumina (PAA) as an effective morphology-directing hard template. Field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) results indicate that the as-prepared YBCO nanowires have average diameters of about 50 nm and lengths up to several microns. The structures of the samples were analysed by x-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), energy-dispersive x-ray spectroscopy (EDX) and inductively coupled plasma (ICP) analysis, which indicate that the nanowires are well crystallized with orthorhombic YBCO-123 structure. The magnetization measurement under zero-field-cooled (ZFC) mode indicates that the superconducting transition temperature (T(c)) of the nanowires is about 92 K, which is in agreement with that of a bulk YBCO sample.

  6. Deposition and characterization of high temperature superconducting YBa2Cu3O7-δ films obtained by DC magnetron sputtering and thermal annealing modification

    NASA Astrophysics Data System (ADS)

    Beshkova, M.; Blagoev, B.; Kovacheva, D.; Mladenov, G.; Nurgaliev, T.

    2008-05-01

    C-axis oriented 100-nm thick YBCO films were deposited on LaAlO3 (100) substrates at substrate temperature of 780°C in a mixed oxygen/argon atmosphere (1:3) of 0.3 Torr by DC off-axis magnetron sputtering. The samples deposited were thermally annealed in oxygen ambient of 600 Torr at 530°C for 40 min. Superconductivity with zero resistance 89.1K was observed for the YBCO films after annealing. These results show that thermal annealing is an important technique for improving the parameters of thin superconducting films. A correlation between the YBCO layers properties before and after annealing was established.

  7. Superconducting Cable

    SciTech Connect

    Hughey, Raburn L.; Sinha, Uday K.; Reece, David S.; Muller, Albert C.

    2005-07-22

    In order to provide a flexible oxide superconducting cable which is reduced in AC loss, tape-shaped superconducting wires covered with a stabilizing metal are wound on a flexible former. The superconducting wires are preferably laid on the former at a bending strain of not more than 0.2%. In laying on the former, a number of tape-shaped superconducting wires are laid on a core member in a side-by-side manner, to form a first layer. A prescribed number of tape-shaped superconducting wires are laid on top of the first layer in a side-by-side manner, to form a second layer. The former may be made of a metal, plastic, reinforced plastic, polymer, or a composite and provides flexibility to the superconducting wires and the cable formed therewith.

  8. Superconducting Cable

    DOEpatents

    Hughey, Raburn L.; Sinha, Uday K.; Reece, David S.; Muller, Albert C.

    2005-03-08

    In order to provide a flexible oxide superconducting cable which is reduced in AC loss, tape-shaped superconducting wires covered with a stabilizing metal are wound on a flexible former. The superconducting wires are preferably laid on the former at a bending strain of not more than 0.2%. In laying on the former, a number of tape-shaped superconducting wires are laid on a core member in a side-by-side manner, to form a first layer. A prescribed number of tape-shaped superconducting wires are laid on top of the first layer in a side-by-side manner, to form a second layer. The former may be made of a metal, plastic, reinforced plastic, polymer, or a composite and provides flexibility to the superconducting wires and the cable formed therewith.

  9. Operation and design selection of high temperature superconducting magnetic bearings

    NASA Astrophysics Data System (ADS)

    Werfel, F. N.; Floegel-Delor, U.; Riedel, T.; Rothfeld, R.; Wippich, D.; Goebel, B.

    2004-10-01

    Axial and radial high temperature superconducting (HTS) magnetic bearings are evaluated by their parameters. Journal bearings possess advantages over thrust bearings. High magnetic gradients in a multi-pole permanent magnet (PM) configuration, the surrounding melt textured YBCO stator and adequate designs are the key features for increasing the overall bearing stiffness. The gap distance between rotor and stator determines the specific forces and has a strong impact on the PM rotor design. We report on the designing, building and measuring of a 200 mm prototype 100 kg HTS bearing with an encapsulated and thermally insulated melt textured YBCO ring stator. The encapsulation requires a magnetically large-gap (4-5 mm) operation but reduces the cryogenic effort substantially. The bearing requires 3 l of LN2 for cooling down, and about 0.2 l LN2 h-1 under operation. This is a dramatic improvement of the efficiency and in the practical usage of HTS magnetic bearings.

  10. Laser ablation synthesis and properties of epitaxial YBa sub 2 Cu sub 3 O sub 7-. delta. /PrBa sub 2 Cu sub 3 O sub 7-. delta. superconducting superlattices

    SciTech Connect

    Lowndes, D.H.; Norton, D.P.; Zheng, X.Y. ); Zhu, Shen . Dept. of Physics and Astronomy)

    1991-09-01

    Pulsed laser ablation has been used to fabricate epitaxial superlattices in which c-axis-perpendicular YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO) layers as thin as a single unit cell are separated by semiconducting PrBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (PBCO) layers. The superlattice {Tc} (R=0) decreases rapidly with increasing PBCO thickness, but then saturates at {Tc}{approximately}19 K, 54 K, 71 K, or 80 K, for structures containing isolated, 1-,2-,3-, or 4-cell-thick YBCO layers, respectively. Recent theoretical analyses suggest that the decrease of {Tc} and broadening of the resistive transition for the thinnest YBCO layers is most likely due either to a crossover from 3D to 2D resistive behavior, or to hole-filling in the YBCO layers caused by electron transfer from the PBCO. We find that the resistance in the superconducting transition region scales with temperature as expected for dissipation by characteristically 2D (vortex) excitations. Departures from the universal'' resistance behavior expected for a 2D Ginzburg-Landau Coulomb gas, as the YBCO thickness is increased or the PBCO thickness is decreased, can be attributed to the onset of phase coupling between the YBCO layers. Thus, the experiments show that YBCO's effective anisotropy can be greatly increased by separating very thin YBCO layers by thicker PBCO layers in superlattice structures. As a results, characteristic 2D dissipation can be observed over a greatly expanded temperature range, relative to both thicker-film and single-crystal YBCO specimens. Experiments also were carried out using two additional isostructural sets of superlattices in which the PBCO layers were replaced by more conductive Y- or Ca-doped PBCO layers, in order to alter any electron transfer from PBCO to YBCO.

  11. Enhanced resonant soft X-ray scattering of YBa2Cu3O7-x (YBCO) 50 nm c-axis film on bi-crystalline substrates

    NASA Astrophysics Data System (ADS)

    Anavacerrada, Maria A.; Sahibudeen, Hizam; Acrivos, Juana V.; Kortright, Jeff B.

    2004-03-01

    The disorder induced by the grain boundary in Josepshon junctions fabricated with 50 nm YBCO films deposited on SrTiO3 bi-crystalline substrates [1] has been investigated by YBCO [001] enhanced resonant soft X-ray scattering. Spectra have been collected in the back scattering geometry near the O(K), Cu(L3,2) and Ba(M5,4) edges at three different positions across the grain boundary. The experiments were performed at the 6.3.1-Jeff B. Kortright station of the Advanced Light Source, LBNL. The strain fields of dislocations perturb the grain boundary local structure, mainly the YBCO oxygen sublattice leading to non-superconducting zones near the grain boundary. By comparison to published spectra near the Cu(L3,2) and Ba(M5,4) edges [2] the oxygen content 7-x is greater than 6.5 at any position in the film. The decrease in the relative intensity of the Cu(L3,2) main peaks in the spectra observed at positions close to the grain boundary suggest a high concentration of holes in the CuO2 layers in this region. Information on the oxygen composition across the grain boundary can be obtained by comparison of the O(K) edge spectra with data previously published on YBCO single crystal with different oxygen content [3]. [1] M. A. Navacerrada, M. L. Lucía and F. Sánchez Quesada, Europhys. Lett. 54, 387 (2001); [2] N. Nücker, E.Pellegrin, P. Schweiss, J. Fink, S. L. Molodtsov, C.T. Simmons, G. Kaindl, A. Erb and G. Müller Vogt, Phys. Rev. B 51, 8529 (1995); [3] J.- H. Guo, S. M. Butorin, N. Wassdahl and J. Nordgren, Phys. Rev. B 61, 9140 (2000) and references therein.

  12. RAPID COMMUNICATION: High performance superconducting wire in high applied magnetic fields via nanoscale defect engineering

    NASA Astrophysics Data System (ADS)

    Wee, Sung Hun; Goyal, Amit; Zuev, Yuri L.; Cantoni, Claudia

    2008-09-01

    High temperature superconducting (HTS) wires capable of carrying large critical currents with low dissipation levels in high applied magnetic fields are needed for a wide range of applications. In particular, for electric power applications involving rotating machinery, such as large-scale motors and generators, a high critical current, Ic, and a high engineering critical current density, JE, in applied magnetic fields in the range of 3-5 Tesla (T) at 65 K are required. In addition, exceeding the minimum performance requirements needed for these applications results in a lower fabrication cost, which is regarded as crucial to realize or enable many large-scale bulk applications of HTS materials. Here we report the fabrication of short segments of a potential superconducting wire comprised of a 4 µm thick YBa2Cu3O7-δ (YBCO) layer on a biaxially textured substrate with a 50% higher Ic and JE than the highest values reported previously. The YBCO film contained columns of self-assembled nanodots of BaZrO3 (BZO) roughly oriented along the c-axis of YBCO. Although the YBCO film was grown at a high deposition rate, three-dimensional self-assembly of the insulating BZO nanodots still occurred. For all magnetic field orientations, minimum Ic and JE at 65 K, 3 T for the wire were 353 A cm-1 and 65.4 kA cm-2, respectively.

  13. High Performance Superconducting Wire in High Applied Magnetic Fields via Nanoscale Defect Engineering

    SciTech Connect

    Goyal, Amit; Wee, Sung Hun; Zuev, Yuri L; Cantoni, Claudia

    2008-01-01

    High temperature superconducting (HTS) wires capable of carrying large critical currents with low dissipation levels in high applied magnetic fields are needed for a wide range of applications. In particular, for electric power applications involving rotating machinery, such as large-scale motors and generators, a high critical current, Ic, and a high engineering critical current density, JE, in applied magnetic fields in the range of 3 5 Tesla (T) at 65 K are required. In addition, exceeding the minimum performance requirements needed for these applications results in a lower fabrication cost, which is regarded as crucial to realize or enable many large-scale bulk applications of HTS materials. Here we report the fabrication of short segments of a potential superconducting wire comprised of a 4 m thick YBa2Cu3O7− (YBCO) layer on a biaxially textured substrate with a 50% higher Ic and JE than the highest values reported previously. The YBCO film contained columns of self-assembled nanodots of BaZrO3 (BZO) roughly oriented along the c-axis of YBCO. Although the YBCO film was grown at a high deposition rate, three-dimensional self-assembly of the insulating BZO nanodots still occurred. For all magnetic field orientations, minimum Ic and JE at 65 K, 3 T for the wire were 353 A cm−1 and 65.4 kA cm−2, respectively.

  14. Superconducting Mixers for Far-Infrared Spectroscopy

    NASA Technical Reports Server (NTRS)

    Betz, A. L.; Boreiko, R. T.; Grossman, E. R.; Reintsema, C. D.; Ono, R. H.; Gerecht, E.

    2002-01-01

    The goal of this project was to fabricate and test planar arrays of superconducting mixers for the 2-6 THz band. The technology is intended for multi-beam receivers aboard Explorer-class missions and the SOFIA Airborne Observatory. The mixer technology is the superconducting transition-edge microbolometer, which is more commonly known as the Hot-Electron micro-Bolometer (HEB). As originally proposed, two superconducting technologies were to be developed: (1) low-Tc niobium HEBs which could approach quantum-noise-limited sensitivities but require cooling to 2- 4 K, and (2) high-Tc YBCO HEBs with sensitivities 10 times worse but with a relaxed cooling requirement of 30-60 K. The low-Tc devices would be best for astronomy applications on SOFIA, whereas the high-Tc devices would be more suitable for planetary missions using systems without stored cryogens. The work plan called for planar micro-fabrication and initial testing of HEB devices at the NIST Boulder clean-room facility. Subsequent assembly and RF testing of selected devices would be done at the CASA laboratory at U. Colorado. Approximately 1-year after work began on this project, Dr. Eyal Gerecht joined the NIST group, and assumed day-to-day responsibility for Nb-HEB development at NIST outside of micro-fabrication. The YBCO-HEB work was to be guided by Dr. Ron Ono, who was the NIST expert in YBCO technology. Unfortunately, recurrent health problems limited the time Ron could devote to the project in its first year. These problems became aggravated in early 2001, and sadly led to Ron's death in October, 2001. His loss was not only a blow to his friends and associates at NIST, but was mounted by the US superconductivity community at large. With his passing, work on high-Tc HEBs ceased at NIST. There was no one to replace him or his expertise. Our work subsequently shifted solely to Nb-HEB devices. In the sections which follow, our progress in the development of diffusion-cooled Nb-HEB mixers is detailed. To

  15. Superconductor-Mediated Modification of Gravity? AC Motor Experiments with Bulk YBCO Disks in Rotating Magnetic Fields

    NASA Technical Reports Server (NTRS)

    Noever, David A.; Koczor, Ronald J.; Roberson, Rick

    1998-01-01

    We have previously reported results using a high precision gravimeter to probe local gravity changes in the neighborhood of large bulk-processed high-temperature superconductors. Podkietnov, et al (Podkietnov, E. and Nieminen, R. (1992) A Possibility of Gravitational Force Shielding by Bulk YBa2 Cu3 O7-x Superconductor, Physica C, C203:441-444.) have indicated that rotating AC fields play an essential role in their observed distortion of combined gravity and barometric pressure readings. We report experiments on large (15 cm diameter) bulk YBCO ceramic superconductors placed in the core of a three-phase, AC motor stator. The applied rotating field produces up to a 12,000 revolutions per minute magnetic field. The field intensity decays rapidly from the maximum at the outer diameter of the superconducting disk (less than 60 Gauss) to the center (less than 10 Gauss). This configuration was applied with and without a permanent DC magnetic field levitating the superconducting disk, with corresponding gravity readings indicating an apparent increase in observed gravity of less than 1 x 10(exp -6)/sq cm, measured above the superconductor. No effect of the rotating magnetic field or thermal environment on the gravimeter readings or on rotating the superconducting disk was noted within the high precision of the observation. Implications for propulsion initiatives and power storage flywheel technologies for high temperature superconductors will be discussed for various spacecraft and satellite applications.

  16. Superconductor-Mediated Modification of Gravity? AC Motor Experiments with Bulk YBCO Disks in Rotating Magnetic Fields

    NASA Technical Reports Server (NTRS)

    Noever, David A.; Koczor, Ronald J.; Roberson, Rick

    1998-01-01

    We have previously reported results using a high precision gravimeter to probe local gravity changes in the neighborhood of large bulk-processed high-temperature superconductors. Podkietnov, et al (Podkietnov, E. and Nieminen, R. (1992) A Possibility of Gravitational Force Shielding by Bulk YBa2 Cu3 O7-x Superconductor, Physica C, C203:441-444.) have indicated that rotating AC fields play an essential role in their observed distortion of combined gravity and barometric pressure readings. We report experiments on large (15 cm diameter) bulk YBCO ceramic superconductors placed in the core of a three-phase, AC motor stator. The applied rotating field produces up to a 12,000 revolutions per minute magnetic field. The field intensity decays rapidly from the maximum at the outer diameter of the superconducting disk (less than 60 Gauss) to the center (less than 10 Gauss). This configuration was applied with and without a permanent DC magnetic field levitating the superconducting disk, with corresponding gravity readings indicating an apparent increase in observed gravity of less than 1 x 10(exp -6)/sq cm, measured above the superconductor. No effect of the rotating magnetic field or thermal environment on the gravimeter readings or on rotating the superconducting disk was noted within the high precision of the observation. Implications for propulsion initiatives and power storage flywheel technologies for high temperature superconductors will be discussed for various spacecraft and satellite applications.

  17. Contribution of ion beam analysis methods to the development of 2nd generation high temperature superconducting (HTS) wires

    SciTech Connect

    Usov, Igor O; Arendt, Paul N; Stan, Liliana; Holesinger, Terry G; Foltyn, Steven R; Depaula, Raymond F

    2009-01-01

    One of the crucial steps in the second generation high temperature superconducting wire program was development of the buffer layer architecture. The architecture designed at the Superconductivity Technology Center at Los Alamos National Laboratory consists of several oxide layers wherein each layer plays a specific role, namely: nucleation layer, diffusion barrier, biaxially textured template, and an intermediate layer with a good match to the lattice parameter of superconducting Y{sub 1}Ba{sub 2}Cu{sub 3}O{sub 7} (YBCO) compound. This report demonstrates how a wide range of ion beam analysis techniques (SIMS, RBS, channeling, PIXE, PIGE, NRA, ERD) was employed for analysis of each buffer layer and the YBCO films. These results assisted in understanding of a variety of physical processes occurring during the buffet layer fabrication and helped to optimize the buffer layer architecture as a whole.

  18. High Temperature Superconducting Underground Cable

    SciTech Connect

    Farrell, Roger, A.

    2010-02-28

    The purpose of this Project was to design, build, install and demonstrate the technical feasibility of an underground high temperature superconducting (HTS) power cable installed between two utility substations. In the first phase two HTS cables, 320 m and 30 m in length, were constructed using 1st generation BSCCO wire. The two 34.5 kV, 800 Arms, 48 MVA sections were connected together using a superconducting joint in an underground vault. In the second phase the 30 m BSCCO cable was replaced by one constructed with 2nd generation YBCO wire. 2nd generation wire is needed for commercialization because of inherent cost and performance benefits. Primary objectives of the Project were to build and operate an HTS cable system which demonstrates significant progress towards commercial progress and addresses real world utility concerns such as installation, maintenance, reliability and compatibility with the existing grid. Four key technical areas addressed were the HTS cable and terminations (where the cable connects to the grid), cryogenic refrigeration system, underground cable-to-cable joint (needed for replacement of cable sections) and cost-effective 2nd generation HTS wire. This was the world’s first installation and operation of an HTS cable underground, between two utility substations as well as the first to demonstrate a cable-to-cable joint, remote monitoring system and 2nd generation HTS.

  19. Recent developments in superconducting receivers

    NASA Astrophysics Data System (ADS)

    Richards, Paul L.

    1990-09-01

    A description is given of recent work at Berkeley on superconducting mixers and detectors for infrared and millimeter wavelengths. The first report is a review article which summarizes the status of development of superconducting components for infrared and millimeter wave receivers. The next report describes accurate measurements and also theoretical modeling of an SIS quasiparticle waveguide mixer for W-band which uses very high quality Ta junctions. The best mixer noise is only 1.3 times the quantum limit. Both the mixer gain and the noise are in quantitative agreement with the quantum theory. Next, a report is given on measurements and theoretical modeling of the absorptivity (surface resistance) of high quality epitaxial films of the high Tc superconductor YBCO from 750 GHz to 21 THz. Finally, there are reports on the design and experimental performance of two different types of high Tc bolometric detectors. One is a conventional bolometer with a gold-black absorber. The other is an antenna coupled microbolometer.

  20. Recent developments in superconducting receivers

    SciTech Connect

    Richards, P.L.

    1990-09-01

    A description is given of recent work at Berkeley on superconducting mixers and detectors for infrared and millimeter wavelengths. The first report is a review article which summarizes the status of development of superconducting components for infrared and millimeter wave receivers. The next report describes accurate measurements and also theoretical modeling of an SIS quasiparticle waveguide mixer for W-band which uses very high quality Ta junctions. The best mixer noise is only 1.3 times the quantum limit. Both the mixer gain and the noise are in quantitative agreement with the quantum theory. Next, a report is given on measurements and theoretical modeling of the absorptivity (surface resistance) of high quality epitaxial films of the high {Tc} superconductor YBCO from 750 GHz to 21 THz. Finally, there are reports on the design and experimental performance of two different types of high {Tc} bolometric detectors. One is a conventional bolometer with a gold-black absorber. The other is an antenna coupled microbolometer.

  1. Crossover between superconductivity and magnetism in SrRuO3 mesocrystal embedded YBa2Cu3O7-x heterostructures.

    PubMed

    Suresh, Vandrangi; Lin, Jheng-Cyuan; Liu, Heng-Jui; Zhang, Zaoli; Chiang, Ping-Chih; Hsun, Yu-Ching; Chen, Yi-Chun; Lin, Jiunn-Yuan; Chu, Ying-Hao

    2016-11-03

    The competition between superconductivity and ferromagnetism poses great challenges and has attracted renewed interest for applications in novel spintronic devices. In order to emphasize their interactions, we fabricated a heterostructure composed of superconducting YBa2Cu3O7-δ (YBCO) film embedded with itinerant ferromagnetic SrRuO3 (SRO) mesocrystals. Starting from a doping concentration of 10 vol% of SRO mesocrystal in a YBCO matrix, corresponding to the density of SRO nanocrystals ∼5 × 10(9) cm(-2), which exhibits the typical characteristic of a metal-superconductor transition, and then increasing the magnetic interactions as a function of SRO embedment, the electronic correlation and the interplay between superconductivity and magnetism throughout the temperature regime were investigated. A metal-insulator transition in the normal state of YBCO and a crossover between superconductivity and magnetism at low temperatures were found upon increasing the density of nano-size SRO crystallites in the YBCO matrix as a consequence of competing interactions between these two ordered phases.

  2. Numerical Simulation of Explosive Consolidation of Superconducting Bulk Components

    NASA Astrophysics Data System (ADS)

    Mamalis, A. G.; Vottea, I. N.; Manolakos, D. E.; Szalay, A.; Kladas, A.

    The explosive compaction technique has been used for manufacturing bulk superconducting components, e.g. three dimensional plates and axisymmetric billets, rods, discs and tubes, with high density and good electrical and magnetic characteristics. The high pressures and temperatures developed in a very short time result in sintering and in fracturing of the original grains, inducing primarily line defects that would provide flux pinning centers in Type II superconductors. Densified superconducting ceramic YBCO bulk components of various geometries were produced by this dynamic technique and the whole process was simulated by the explicit finite element code LS-DYNA3D. In this paper, experimental and numerical results of the fabricated superconducting bulks are reported and discussed. Applications are also briefly outlined.

  3. Magnetic Excitations and the Exchange Energy Available for Superconductivity

    NASA Astrophysics Data System (ADS)

    Dahm, Thomas

    2007-03-01

    We have made detailed comparisons of theoretical calculations and experimental neutron scattering results in absolute units in order to determine the temperature change of the nearest neighbor spin correlations in optimally doped YBCO as one goes from the normal to the superconducting state [1]. This allows us to estimate the magnetic exchange energy change that becomes available for superconducting condensation. Our results show that the available magnetic energy change is about 10-15 times larger than the energy necessary for superconducting condensation [1]. We discuss the issue of the spin sum rule and implications for a spin fluctuation driven pairing interaction as well as implications for low energy excitations in angular photoemission spectroscopy [2]. [1] H. Woo et al, Nature Physics 2, 600 (2006). [2] T. Dahm et al, Phys. Rev. B 72, 214512 (2005).

  4. Superconducting devices

    SciTech Connect

    Ruggiero, S.T. . Dept. of Physics); Rudman, D.A. . Dept. of Materials Science and Engineering)

    1990-01-01

    This book presents a discussion of the theory, fabrication, and qualification of superconducting device elements and integrated circuitry. A look at issues key to the development of practical superconducting devices and systems is presented. Integrated systems, including the fabrication and application of SQUIDs, Josephson arrays, microwave detectors, digital signal processors and computers, and analog signal processors are discussed.

  5. Superconducting Materials

    NASA Technical Reports Server (NTRS)

    1995-01-01

    After working with Lewis Research Center and Jet Propulsion Laboratory, Superconducting Technologies, Inc. (STI) adapted NASA requirements and refined its own standard production recipe. STI uses high temperature superconducting (HTS) materials in its basic products: high quality thin films, circuits and components. Applications include microwave circuits for radar to reduce interference.

  6. Growth of YBCO Thin Films on TiN(001) and CeO2-Coated TiN Surfaces

    DTIC Science & Technology

    2012-02-01

    substrates. Thin CeO2 (~200 nm thick) and YBCO (~300 nm thick) layers were grown on TiN-coated MgO substrates, using pulsed laser deposition. While YBCO ...and YBCO (300 nm thick) layers were grown on TiN-coated MgO substrates, using pulsed laser deposition. While YBCO grown directly on TiN was of poor...grown on the TiN-coated MgO and then an 300 nm thick YBCO layers was subsequently depos- ited. For other samples, YBCO deposition directly on the

  7. Homoepitaxial growth of MOD-YBCO thick films on evaporated and MOD templates

    NASA Astrophysics Data System (ADS)

    Tanabe, D.; Yamaguchi, I.; Sohma, M.; Tsukada, K.; Matsui, M.; Kumagai, T.; Manabe, T.

    2011-11-01

    We have prepared metal organic deposition (MOD)-YBCO thick films by repeating the coating-pyrolysis-crystallization procedure onto ∼100-nm-thick evaporated and MOD templates. Surface morphology of the template was found to strongly affect the homoepitaxial growth of MOD-YBCO layers on the template; namely, the epitaxial growth of MOD-YBCO on the evaporated template was much easier than that on the MOD template. A 220-nm-thick epitaxial MOD-YBCO film was successfully prepared on the 100-nm-thick evaporated-YBCO template to obtain a 320-nm-thick YBCO film, which exhibited Jc = 2.44 MA/cm2 and Ic = 78 A/cm. The Ic value has significantly increased from 37 A/cm for the evaporated-template.

  8. Superconducting structure

    DOEpatents

    Kwon, Chuhee; Jia, Quanxi; Foltyn, Stephen R.

    2003-04-01

    A superconductive structure including a dielectric oxide substrate, a thin buffer layer of a superconducting material thereon; and, a layer of a rare earth-barium-copper oxide superconducting film thereon the thin layer of yttrium-barium-copper oxide, the rare earth selected from the group consisting of samarium, gadolinium, ytterbium, erbium, neodymium, dysprosium, holmium, lutetium, a combination of more than one element from the rare earth group and a combination of one or more elements from the rare earth group with yttrium, the buffer layer of superconducting material characterized as having chemical and structural compatibility with the dielectric oxide substrate and the rare earth-barium-copper oxide superconducting film is provided.

  9. Superconducting Structure

    DOEpatents

    Kwon, Chuhee; Jia, Quanxi; Foltyn, Stephen R.

    2005-09-13

    A superconductive structure including a dielectric oxide substrate, a thin buffer layer of a superconducting material thereon; and, a layer of a rare earth-barium-copper oxide superconducting film thereon the thin layer of yttrium-barium-copper oxide, the rare earth selected from the group consisting of samarium, gadolinium, ytterbium, erbium, neodymium, dysprosium, holmium, lutetium, a combination of more than one element from the rare earth group and a combination of one or more elements from the rare earth group with yttrium, the buffer layer of superconducting material characterized as having chemical and structural compatibility with the dielectric oxide substrate and the rare earth-barium-copper oxide superconducting film is provided.

  10. Critical Current in YBCO Coated Conductors in the Presence of a Macroscopic Defect (POSTPRINT)

    DTIC Science & Technology

    2010-03-01

    AFRL-RZ-WP-TP-2010-2084 CRITICAL CURRENT IN YBCO COATED CONDUCTORS IN THE PRESENCE OF A MACROSCOPIC DEFECT (POSTPRINT) Milan Polak and...CRITICAL CURRENT IN YBCO COATED CONDUCTORS IN THE PRESENCE OF A MACROSCOPIC DEFECT (POSTPRINT) 5a. CONTRACT NUMBER In-house 5b. GRANT NUMBER 5c...display, or disclose the work. 14. ABSTRACT We have studied the effects of localized defects in the YBCO coated conductors on the critical current. The

  11. Pulsed Laser Deposition of YBCO With Yttrium Oxide Buffer Layers (Postprint)

    DTIC Science & Technology

    2012-02-01

    AFRL-RZ-WP-TP-2012-0092 PULSED LASER DEPOSITION OF YBCO WITH YTTRIUM OXIDE BUFFER LAYERS (POSTPRINT) Paul N. Barnes, Timothy J. Haugan...Paper Postprint 01 January 2002 – 01 January 2004 4. TITLE AND SUBTITLE PULSED LASER DEPOSITION OF YBCO WITH YTTRIUM OXIDE BUFFER LAYERS (POSTPRINT...Textured metallic substrate based HTS coated conductors with the YBCO /CeO2/YSZ/CeO2/Ni architecture have already been shown to exhibit high current

  12. Stability and Normal Zone Propagation Speed in YBCO Coated Conductors with Increased Interfacial Resistance (PREPRINT)

    DTIC Science & Technology

    2010-03-01

    AFRL-RZ-WP-TP-2010-2085 STABILITY AND NORMAL ZONE PROPAGATION SPEED IN YBCO COATED CONDUCTORS WITH INCREASED INTERFACIAL RESISTANCE...August 2006 – 25 August 2008 4. TITLE AND SUBTITLE STABILITY AND NORMAL ZONE PROPAGATION SPEED IN YBCO COATED CONDUCTORS WITH INCREASED INTERFACIAL...reproduce, release, perform, display, or disclose the work. 14. ABSTRACT We will discuss how stability and speed of normal zone propagation in YBCO

  13. AFM investigations of the morphology features and local mechanical properties of HTS YBCO thin films

    NASA Astrophysics Data System (ADS)

    Soifer, Yakov M.; Verdyan, Armen; Lapsker, Igor; Azoulay, Jacob

    2004-08-01

    In the paper presented here the application of the atomic force microscope (AFM) is considered for evaluation of hardness and Young's modulus of high Tc superconducting YBCO thin films of different thickness (from 0.05 to 1 μm) grown on unbuffered SrTiO 3 (film I) and on sapphire with a buffer layer of CeO 2 (film II). The best film features a transition temperature Tc of 90 K, critical current density Jc ( H=0) of 3 × 10 7 A/cm 2 at 4.2 K and 2 × 10 6 A/cm 2 at 77 K. The relationship between mechanical properties and microstructure of these films was investigated. It was found that all the films comprised well-defined Cu-rich precipitates of different size and with different density on their surface. For both type of films the hardness was measured to be in the range of 12-18 GPa. The Young's modulus of the films was about 180-200 GPa. The nanoindentation and nanoscratching measurements showed that the mechanical strength of the films studied was determined mainly by mechanical failure and surface defects (secondary phases).

  14. Microstructural evolution in multiseeded YBCO bulk samples grown by the TSMG process

    NASA Astrophysics Data System (ADS)

    Goodfellow, A.; Shi, Y.-H.; Durrell, J. H.; Dennis, A. R.; Cardwell, D. A.; Grovenor, C. R. M.; Speller, S. C.

    2016-11-01

    Superconducting single-grain YBCO bulk samples with the ability to trap high magnetic fields can be grown using the top-seeded melt-growth process. Multiseeding techniques have the potential to enable larger diameter bulks to be grown, but the performance of these materials is not yet comparable to the single-seeded bulks. Here we carry out detailed three-dimensional microstructural characterisation on a multiseeded sample grown with the seeds aligned in the 0°-0° geometry using high resolution microanalysis techniques. Chemical and structural variations have been correlated with the trapped field distribution in three separate slices of the sample. The top slice of the sample shows four peaks in trapped field, indicating that the current flows in four separate loops rather than in one large loop within the sample. This has been explained by the build-up in insulating Y-211 particles where the growth fronts from the two seeds meet, forming a barrier to current flow, as well as the low Y-211 content (and hence low J c) of the large c-axis growth sector.

  15. Microstructure of Josephson junctions: Effect on supercurrent transport in YBCO grain boundary and barrier layer junctions

    SciTech Connect

    Merkle, K.L.; Huang, Y.

    1998-01-01

    The electric transport of high-temperature superconductors, such as YBa{sub 2}Cu{sub 3}O{sub 7{minus}x} (YBCO), can be strongly restricted by the presence of high-angle grain boundaries (GB). This weak-link behavior is governed by the macroscopic GB geometry and the microscopic grain boundary structure and composition at the atomic level. Whereas grain boundaries present a considerable impediment to high current applications of high T{sub c} materials, there is considerable commercial interest in exploiting the weak-link-nature of grain boundaries for the design of microelectronic devices, such as superconducting quantum interference devices (SQUIDs). The Josephson junctions which form the basis of this technology can also be formed by introducing artificial barriers into the superconductor. The authors have examined both types of Josephson junctions by EM techniques in an effort to understand the connection between microstructure/chemistry and electrical transport properties. This knowledge is a valuable resource for the design and production of improved devices.

  16. Pseudogap signatures measured in the Fermi surface of underdoped YBCO by quantum oscillations

    NASA Astrophysics Data System (ADS)

    Sebastian, Suchitra E.

    2013-03-01

    Solving the riddle of the pseudogap state in underdoped high temperature superconductors is critical to the understanding of the origin of high temperature superconductivity. Quantum oscillations performed on single crystals of the family of underdoped YBCO cuprates reveal small Fermi surface pockets in the normal state accessed at low temperatures and high magnetic fields. It has been widely thought, however, that high magnetic fields cause this state to be significantly different from the mysterious pseudogap state measured at high temperatures and low magnetic fields. In this talk I will present a quantum oscillation study of underdoped YBa2Cu3O6+x up to magnetic fields of 100 T that reveals a dimensional collapse of the Fermi surface due to a drastic reduction in c-axis hopping, identical to the pseudogap signature measured in the low magnetic field regime. We therefore conclude that the fundamental properties of the pseudogap are encoded in the Fermi surface, an understanding of which is critical to uncovering the origin of the pseudogap in high temperature superconductors. Possible mechanisms are discussed to explain the origin of the Fermi surface in underdoped YBa2Cu3O6+x. This work was performed in collaboration with G. Lonzarich (University of Cambridge), N. Harrison, M. Altarawneh, F. Balakirev (Los Alamos National Laboratory), and R. Liang, W. Hardy, D. Bonn (University of British Columbia)

  17. Superconductivity in 4 angstrom single-walled carbon nanotubes.

    PubMed

    Tang, Z K; Zhang, L; Wang, N; Zhang, X X; Wen, G H; Li, G D; Wang, J N; Chan, C T; Sheng, P

    2001-06-29

    Investigation of the magnetic and transport properties of single-walled small-diameter carbon nanotubes embedded in a zeolite matrix revealed that at temperatures below 20 kelvin, 4 angstrom tubes exhibit superconducting behavior manifest as an anisotropic Meissner effect, with a superconducting gap and fluctuation supercurrent. The measured superconducting characteristics display smooth temperature variations owing to one-dimensional fluctuations, with a mean-field superconducting transition temperature of 15 kelvin. Statistical mechanic calculations based on the Ginzburg-Landau free-energy functional yield predictions that are in excellent agreement with the experiments.

  18. Electrodeposited Ag-Stabilization Layer for High Temperature Superconducting Coated Conductors: Preprint

    SciTech Connect

    Bhattacharya, R. N.; Mann, J.; Qiao, Y.; Zhang, Y.; Selvamanickam, V.

    2010-11-01

    We developed a non-aqueous based electrodepostion process of Ag-stabilization layer on YBCO superconductor tapes. The non-aqueous electroplating solution is non-reactive to the HTS layer thus does not detoriate the critical current capability of the superconductor layer when plated directly on the HTS tape. The superconducting current capabilities of these tapes were measured by non-contact magnetic measurements.

  19. Scientific Presentations on High Temperature Superconductivity and Cryogenic Power Research from 2005-2013

    DTIC Science & Technology

    2013-11-01

    A. Campbell, I. Maartense, G. Cryogenic Characterization of Superconducting YBCO Films on Strontium Titanate Bicrystals using Evanescent 1...Haugan, C.V. Varanasi, M. Rane, F. Ramos Minute doping with deleterious rare earths in YBa2Cu3O7-δ films for flux pinning enhancements 89 ...coated conductors with minimized coupling losses 89 12506 2006 Adv. Cryo. Eng. Chakrapani V. Varanasi, Chuck Leon, Andrew D. Chaney, Nicholas

  20. A superconducting hydrogen maser resonator made from electrophoretic YBa sub 2 Cu sub 3 O sub 7 minus. delta

    SciTech Connect

    Opie, D.; Schone, H. . Dept. of Physics); Hein, M.; Muller, G.; Piel, H.; Wehler, D. ); Folen, V.; Wolf, S. )

    1991-03-01

    This paper reports on a compact loop-gap hydrogen maser resonator constructed by electrophoretic deposition of YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} (YBCO) onto silver. The resonator is tuned to operate at the hyperfine transition frequency of hydrogen (1.42 GHz). This device is considered to be the first step towards a superconducting cavity for a compact hydrogen maser to be used in the Global Positioning System (GPS). The required miniaturization of the resonator reduces its Q value. This effect can be compensated for by the low surface resistance of YBCO at 77 K. Large and curved polycrystalline YBCO layers can be obtained by the electrophoretic deposition technique. In this contribution we report on the construction and the test of High Temperature Superconductor Space Experiment (HTSSE).

  1. A Thermally Actuated Flux Pump for Energizing YBCO Pucks

    DTIC Science & Technology

    2016-05-01

    magnetic circuit. The circuit was cooled using a cryocooler and heat pulses were applied to the dysprosium by turning the cold head on and off. These...on parts of the circuit. Currents through the coils generated flux in the magnetic circuit. The circuit was cooled using a cryocooler and heat pulses...Division Defence Science and Technology Group DST-Group-TN-1527 ABSTRACT This paper presents results for the magnetization of a disc of YBCO

  2. High temperature superconducting films and multilayers for electronics

    NASA Astrophysics Data System (ADS)

    Gavaler, John R.; Talvacchio, John

    1994-04-01

    The overall objective of this program was to develop a materials and fundamental device base for high-transition-temperature superconducting (HTS) electronics capable of operating at greater than 50K. Progress is reported on four tasks which address problems fundamental to the understanding of the superconducting state in HTS films, the application of HTS films in passive microwave circuits, the realization of HTS digital electronics, and the development of new superconducting devices. Large-area epitaxial YBCO films with low RF losses developed under this program and techniques for depositing them on both sides of single-crystal substrates were used in other Westinghouse and government-funded programs to develop HTS channelized filterbanks, delay lines, UHF antenna matching networks, and low-phase-noise resonators. An understanding was achieved of the role of oxygenation during film growth and the effect of film microstructure on RF losses. For HTS digital circuit fabrication, both active devices step-edge and edge-type YBCO Josephson junctions and trilayer BKBO junctions and passive structures were developed, such as crossovers, vias, and contacts. These capabilities were transfered to other Westinghouse and government-funded programs which demonstrated the first HTS SFQ circuits and SQUID's with integrated ground planes.

  3. Superconducting electronics

    NASA Astrophysics Data System (ADS)

    Gubankov, V. N.

    The current status and principal trends, recent achievements, and future prospects of superconducting electronics are reviewed. In particular, attention is given to developments in high-temperature superconductivity; contribution of high-temperature superconductors to superconducting electronics; problems associated with high-temperature superconductor devices and recent achievements in this area; and goals in the field of electronics employing high-temperature superconductor components in comparison with the use of traditional superconductors. Applications discussed include ultrasensitive detection of weak electromagnetic radiation, SQUID-based magnetometry; cryogenic logic and memory systems, and measuring instruments.

  4. The Effect of Axial Stress on YBCO Coils

    SciTech Connect

    Sampson, W.; Anerella, M.; Cozzolino, J.P.; Gupta, R.C.; Shiroyanagi, Y.; Evangelou, E.

    2011-03-28

    The large aspect ratio of typical YBCO conductors makes them ideal for constructing solenoids from pancake style coils. An advantage of this method is that each subunit can be tested before assembly into the finished magnet. The fact that conductors are available in relatively short lengths is another reason for using such a fabrication technique. The principal drawback is the large number of joints required to connect the coils together. When very high field solenoids such as those contemplated for the muon collider are built in this way the magnetic forces between pancakes can be very large. Extensive measurements have been made on the effect of stress on short lengths of conductor, but there is little or no data on the effect of intercoil loading. The experiment described in this paper was designed to test the ability of YBCO coils to withstand these forces. A spiral wound 'pancake' coil made from YBCO coated conductor has been stressed to a pressure of 100MPa in the axial direction at 77K. In this case axial refers to the coil so that the force is applied to the edge of the conductor. The effect on the critical current was small and completely reversible. Repeatedly cycling the pressure had no measureable permanent effect on the coil. The small current change observed exhibited a slight hysteretic behaviour during the loading cycle.

  5. Superconducting magnetic coil

    DOEpatents

    Aized, Dawood; Schwall, Robert E.

    1999-06-22

    A superconducting magnetic coil includes a plurality of sections positioned axially along the longitudinal axis of the coil, each section being formed of an anisotropic high temperature superconductor material wound about a longitudinal axis of the coil and having an associated critical current value that is dependent on the orientation of the magnetic field of the coil. The cross section of the superconductor, or the type of superconductor material, at sections along the axial and radial axes of the coil are changed to provide an increased critical current at those regions where the magnetic field is oriented more perpendicularly to the conductor plane, to thereby increase the critical current at these regions and to maintain an overall higher critical current of the coil.

  6. Superconducting magnetic coil

    DOEpatents

    Aized, D.; Schwall, R.E.

    1999-06-22

    A superconducting magnetic coil includes a plurality of sections positioned axially along the longitudinal axis of the coil, each section being formed of an anisotropic high temperature superconductor material wound about a longitudinal axis of the coil and having an associated critical current value that is dependent on the orientation of the magnetic field of the coil. The cross section of the superconductor, or the type of superconductor material, at sections along the axial and radial axes of the coil are changed to provide an increased critical current at those regions where the magnetic field is oriented more perpendicularly to the conductor plane, to thereby increase the critical current at these regions and to maintain an overall higher critical current of the coil. 15 figs.

  7. Superconducting magnetic coil

    DOEpatents

    Aized, Dawood; Schwall, Robert E.

    1996-06-11

    A superconducting magnetic coil includes a plurality of sections positioned axially along the longitudinal axis of the coil, each section being formed of an anisotropic high temperature superconductor material wound about a longitudinal axis of the coil and having an associated critical current value that is dependent on the orientation of the magnetic field of the coil. The cross section of the superconductor, or the type of superconductor material, at sections along the axial and radial axes of the coil are changed to provide an increased critical current at those regions where the magnetic field is oriented more perpendicularly to the conductor plane, to thereby increase the critical current at these regions and to maintain an overall higher critical current of the coil.

  8. Superconductivity: Phenomenology

    SciTech Connect

    Falicov, L.M.

    1988-08-01

    This document discusses first the following topics: (a) The superconducting transition temperature; (b) Zero resistivity; (c) The Meissner effect; (d) The isotope effect; (e) Microwave and optical properties; and (f) The superconducting energy gap. Part II of this document investigates the Ginzburg-Landau equations by discussing: (a) The coherence length; (b) The penetration depth; (c) Flux quantization; (d) Magnetic-field dependence of the energy gap; (e) Quantum interference phenomena; and (f) The Josephson effect.

  9. Superconducting gap structure of FeSe.

    PubMed

    Jiao, Lin; Huang, Chien-Lung; Rößler, Sahana; Koz, Cevriye; Rößler, Ulrich K; Schwarz, Ulrich; Wirth, Steffen

    2017-03-07

    The microscopic mechanism governing the zero-resistance flow of current in some iron-based, high-temperature superconducting materials is not well understood up to now. A central issue concerning the investigation of these materials is their superconducting gap symmetry and structure. Here we present a combined study of low-temperature specific heat and scanning tunnelling microscopy measurements on single crystalline FeSe. The results reveal the existence of at least two superconducting gaps which can be represented by a phenomenological two-band model. The analysis of the specific heat suggests significant anisotropy in the gap magnitude with deep gap minima. The tunneling spectra display an overall "U"-shaped gap close to the Fermi level away as well as on top of twin boundaries. These results are compatible with the anisotropic nodeless models describing superconductivity in FeSe.

  10. Superconducting gap structure of FeSe

    NASA Astrophysics Data System (ADS)

    Jiao, Lin; Huang, Chien-Lung; Rößler, Sahana; Koz, Cevriye; Rößler, Ulrich K.; Schwarz, Ulrich; Wirth, Steffen

    2017-03-01

    The microscopic mechanism governing the zero-resistance flow of current in some iron-based, high-temperature superconducting materials is not well understood up to now. A central issue concerning the investigation of these materials is their superconducting gap symmetry and structure. Here we present a combined study of low-temperature specific heat and scanning tunnelling microscopy measurements on single crystalline FeSe. The results reveal the existence of at least two superconducting gaps which can be represented by a phenomenological two-band model. The analysis of the specific heat suggests significant anisotropy in the gap magnitude with deep gap minima. The tunneling spectra display an overall “U”-shaped gap close to the Fermi level away as well as on top of twin boundaries. These results are compatible with the anisotropic nodeless models describing superconductivity in FeSe.

  11. Superconducting gap structure of FeSe

    PubMed Central

    Jiao, Lin; Huang, Chien-Lung; Rößler, Sahana; Koz, Cevriye; Rößler, Ulrich K.; Schwarz, Ulrich; Wirth, Steffen

    2017-01-01

    The microscopic mechanism governing the zero-resistance flow of current in some iron-based, high-temperature superconducting materials is not well understood up to now. A central issue concerning the investigation of these materials is their superconducting gap symmetry and structure. Here we present a combined study of low-temperature specific heat and scanning tunnelling microscopy measurements on single crystalline FeSe. The results reveal the existence of at least two superconducting gaps which can be represented by a phenomenological two-band model. The analysis of the specific heat suggests significant anisotropy in the gap magnitude with deep gap minima. The tunneling spectra display an overall “U”-shaped gap close to the Fermi level away as well as on top of twin boundaries. These results are compatible with the anisotropic nodeless models describing superconductivity in FeSe. PMID:28266654

  12. 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.

  13. Ultra low noise YBa{sub 2}Cu{sub 3}O{sub 7−δ} nano superconducting quantum interference devices implementing nanowires

    SciTech Connect

    Arpaia, R.; Arzeo, M.; Nawaz, S.; Charpentier, S.; Lombardi, F.; Bauch, T.

    2014-02-17

    We present results on ultra low noise YBa{sub 2}Cu{sub 3}O{sub 7–δ} (YBCO) nano Superconducting QUantum Interference Devices (nanoSQUIDs). To realize such devices, we implemented high quality YBCO nanowires, working as weak links between two electrodes. We observe critical current modulation as a function of an externally applied magnetic field in the full temperature range below the transition temperature T{sub C}. The white flux noise below 1μΦ{sub 0}/√(Hz) at T=8 K makes our nanoSQUIDs very attractive for the detection of small spin systems.

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

    PubMed

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

    2016-05-21

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

  16. High Critical Current Density of YBa2Cu3O7‑x Superconducting Films Prepared through a DUV-assisted Solution Deposition Process

    NASA Astrophysics Data System (ADS)

    Chen, Yuanqing; Bian, Weibai; Huang, Wenhuan; Tang, Xinni; Zhao, Gaoyang; Li, Lingwei; Li, Na; Huo, Wen; Jia, Jiqiang; You, Caiyin

    2016-12-01

    Although the solution deposition of YBa2Cu3O7‑x (YBCO) superconducting films is cost effective and capable of large-scale production, further improvements in their superconductivity are necessary. In this study, a deep UV (DUV) irradiation technique combined with a low-fluorine solution process was developed to prepare YBCO films. An acrylic acidic group as the chelating agent was used in the precursor solution. The acrylic acidic group was highly sensitive to DUV light at 254 nm and significantly absorbed UV light. The coated gel films exposed to DUV light decomposed at 150 °C and copper aggregation was prevented. The UV irradiation promoted the removal of the carbon residue and other by-products in the films, increased the density and enhanced the crystallinity and superconductivity of the YBCO films. Using a solution with F/Ba = 2, YBCO films with thicknesses of 260 nm and enhanced critical current densities of nearly 8 MA/cm2 were produced on the LaAlO3 (LAO) substrates.

  17. High Critical Current Density of YBa2Cu3O7-x Superconducting Films Prepared through a DUV-assisted Solution Deposition Process.

    PubMed

    Chen, Yuanqing; Bian, Weibai; Huang, Wenhuan; Tang, Xinni; Zhao, Gaoyang; Li, Lingwei; Li, Na; Huo, Wen; Jia, Jiqiang; You, Caiyin

    2016-12-01

    Although the solution deposition of YBa2Cu3O7-x (YBCO) superconducting films is cost effective and capable of large-scale production, further improvements in their superconductivity are necessary. In this study, a deep UV (DUV) irradiation technique combined with a low-fluorine solution process was developed to prepare YBCO films. An acrylic acidic group as the chelating agent was used in the precursor solution. The acrylic acidic group was highly sensitive to DUV light at 254 nm and significantly absorbed UV light. The coated gel films exposed to DUV light decomposed at 150 °C and copper aggregation was prevented. The UV irradiation promoted the removal of the carbon residue and other by-products in the films, increased the density and enhanced the crystallinity and superconductivity of the YBCO films. Using a solution with F/Ba = 2, YBCO films with thicknesses of 260 nm and enhanced critical current densities of nearly 8 MA/cm(2) were produced on the LaAlO3 (LAO) substrates.

  18. High Critical Current Density of YBa2Cu3O7−x Superconducting Films Prepared through a DUV-assisted Solution Deposition Process

    PubMed Central

    Chen, Yuanqing; Bian, Weibai; Huang, Wenhuan; Tang, Xinni; Zhao, Gaoyang; Li, Lingwei; Li, Na; Huo, Wen; Jia, Jiqiang; You, Caiyin

    2016-01-01

    Although the solution deposition of YBa2Cu3O7−x (YBCO) superconducting films is cost effective and capable of large-scale production, further improvements in their superconductivity are necessary. In this study, a deep UV (DUV) irradiation technique combined with a low-fluorine solution process was developed to prepare YBCO films. An acrylic acidic group as the chelating agent was used in the precursor solution. The acrylic acidic group was highly sensitive to DUV light at 254 nm and significantly absorbed UV light. The coated gel films exposed to DUV light decomposed at 150 °C and copper aggregation was prevented. The UV irradiation promoted the removal of the carbon residue and other by-products in the films, increased the density and enhanced the crystallinity and superconductivity of the YBCO films. Using a solution with F/Ba = 2, YBCO films with thicknesses of 260 nm and enhanced critical current densities of nearly 8 MA/cm2 were produced on the LaAlO3 (LAO) substrates. PMID:27905544

  19. Synthesis of YBa2Cu3O(7-δ) and Y2BaCuO5 nanocrystalline powders for YBCO superconductors using carbon nanotube templates.

    PubMed

    Shi, Yunhua; Hasan, Tawfique; Babu, Nadendla H; Torrisi, Felice; Milana, Silvia; Ferrari, Andrea C; Cardwell, David A

    2012-06-26

    We fabricate nanosized superconducting YBa(2)Cu(3)O(7-δ) (Y-123) and nonsuperconducting Y(2)BaCuO(5) (Y-211) powders using carbon nanotubes as template. The mean particle size of Y-123 and Y-211 is 12 and 30 nm, respectively. The superconducting transition temperature of the Y-123 nanopowder is 90.9 K, similar to that of commercial, micrometer-scale powders fabricated by conventional processing. The elimination of carbon and the formation of a high purity superconducting phase both on the micro- and macroscale is confirmed by Raman spectroscopy and X-ray diffraction. We also demonstrate improvement in the superconducting properties of YBCO single grain bulk samples fabricated using the nanosize Y-211 powder, both in terms of trapped field and critical current density. The former reaches 553 mT at 77 K, with a ∼20% improvement compared to samples fabricated from commercial powders. Thus, our processing method is an effective source of pinning centers in single grain superconductors.

  20. Superconducting Fault Current Limiter for Transmission Voltage

    NASA Astrophysics Data System (ADS)

    Kraemer, Hans-Peter; Schmidt, Wolfgang; Cai, Hong; Gamble, Bruce; Madura, David; MacDonald, Tim; McNamara, Joe; Romanosky, Walther; Snitchler, Greg; Lallouet, Nicolas; Schmidt, Frank; Ahmed, Syed

    Within a collaboration of American Superconductor, Siemens, Nexans and Southern California Edison one electrical phase of a resistive superconducting fault current limiter for the 115 kV transmission voltage level has been designed and manufactured. The active part of the limiter consists of 63 bifilar coils made of 12 mm wide steel-stabilized YBCO conductor and is housed in a cryostat operated at 5 bar and 74 K. The first phase was completely assembled and successfully subjected to power switching tests and high voltage tests. The basic design of the system and the test results are reported. The work was funded in part by US-DOE under Contract Number DE-FC26-07NT43243.

  1. Superconductivity in Russia: Update and prospects

    NASA Technical Reports Server (NTRS)

    Ozhogin, V.

    1995-01-01

    The research projects and new technological developments that have occured in Russia are highlighted in this document. Some of the research discussed includes: x-ray structure analysis of YBCO superconducting single crystals and accompanying phase transformations; the role of electron-electron interaction in High Temperature Superconductors (HTSC); the formation of Cooper pairs in crystals; the synthesis and research on a new family of superconductors based on complex copper and mercury oxides (HgBa2CuO4 + alpha and HgBa2CaCu2O6 + alpha); methods for the extraction of higher (up to C200) fullerenes and metalfullerenides has been developed; and process of production of Josephson junctions and development of SQUID's.

  2. Experimental studies of diffusion welding of YBCO to copper using solder layers

    NASA Astrophysics Data System (ADS)

    Xie, Y.; Ouyang, Z.; Shi, L.; Kuang, Z.; Meng, M.

    2017-02-01

    The welding technology is of great importance in YBCO application. To make better joints, the diffusion welding of YBCO tape to copper has been carried out in a vacuum environment. In consideration of high welding temperature (above 200°C) could do damage to the material performance, a new kind of diffusion welding method with temperature below 200 °C has been developed recently. A new welding appliance which can offer pressure over 35Kg/mm2 and controlled temperature has been designed and built; several YBCO coated conductors joints soldered with different melting points of tins has been tested. The results showed that the diffusion can perfectly connect YBCO to copper as well as stainless steel and resistance of the joint was low, and the YBCO tape could bear 217°C for at least 15mins.

  3. Rapid and semi-analytical design and simulation of a toroidal magnet made with YBCO and MgB2 superconductors

    DOE PAGES

    Dimitrov, I. K.; Zhang, X.; Solovyov, V. F.; ...

    2015-07-07

    Recent advances in second-generation (YBCO) high-temperature superconducting wire could potentially enable the design of super high performance energy storage devices that combine the high energy density of chemical storage with the high power of superconducting magnetic storage. However, the high aspect ratio and the considerable filament size of these wires require the concomitant development of dedicated optimization methods that account for the critical current density in type-II superconductors. In this study, we report on the novel application and results of a CPU-efficient semianalytical computer code based on the Radia 3-D magnetostatics software package. Our algorithm is used to simulate andmore » optimize the energy density of a superconducting magnetic energy storage device model, based on design constraints, such as overall size and number of coils. The rapid performance of the code is pivoted on analytical calculations of the magnetic field based on an efficient implementation of the Biot-Savart law for a large variety of 3-D “base” geometries in the Radia package. The significantly reduced CPU time and simple data input in conjunction with the consideration of realistic input variables, such as material-specific, temperature, and magnetic-field-dependent critical current densities, have enabled the Radia-based algorithm to outperform finite-element approaches in CPU time at the same accuracy levels. Comparative simulations of MgB2 and YBCO-based devices are performed at 4.2 K, in order to ascertain the realistic efficiency of the design configurations.« less

  4. Rapid and semi-analytical design and simulation of a toroidal magnet made with YBCO and MgB2 superconductors

    SciTech Connect

    Dimitrov, I. K.; Zhang, X.; Solovyov, V. F.; Chubar, O.; Li, Qiang

    2015-07-07

    Recent advances in second-generation (YBCO) high-temperature superconducting wire could potentially enable the design of super high performance energy storage devices that combine the high energy density of chemical storage with the high power of superconducting magnetic storage. However, the high aspect ratio and the considerable filament size of these wires require the concomitant development of dedicated optimization methods that account for the critical current density in type-II superconductors. In this study, we report on the novel application and results of a CPU-efficient semianalytical computer code based on the Radia 3-D magnetostatics software package. Our algorithm is used to simulate and optimize the energy density of a superconducting magnetic energy storage device model, based on design constraints, such as overall size and number of coils. The rapid performance of the code is pivoted on analytical calculations of the magnetic field based on an efficient implementation of the Biot-Savart law for a large variety of 3-D “base” geometries in the Radia package. The significantly reduced CPU time and simple data input in conjunction with the consideration of realistic input variables, such as material-specific, temperature, and magnetic-field-dependent critical current densities, have enabled the Radia-based algorithm to outperform finite-element approaches in CPU time at the same accuracy levels. Comparative simulations of MgB2 and YBCO-based devices are performed at 4.2 K, in order to ascertain the realistic efficiency of the design configurations.

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

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

  6. Superconducting Memristors

    NASA Astrophysics Data System (ADS)

    Peotta, Sebastiano; Di Ventra, Massimiliano

    2014-09-01

    In his original work, Josephson predicted that a phase-dependent conductance should be present in superconducting tunnel junctions, an effect difficult to detect, mainly because it is hard to single it out from the usual nondissipative Josephson current. We propose a solution for this problem that consists of using different superconducting materials to realize the two junctions of a superconducting interferometer. According to the Ambegaokar-Baratoff relation the two junctions have different conductances if the critical currents are equal, thus the Josephson current can be suppressed by fixing the magnetic flux in the loop at half of a flux quantum without canceling the phase-dependent conductance. Our proposal can be used to study the phase-dependent conductance, an effect present in principle in all superconducting weak links. From the standpoint of nonlinear circuit theory, such a device is in fact an ideal memristor with possible applications to memories and neuromorphic computing in the framework of ultrafast and low-energy-consumption superconducting digital circuits.

  7. Development of hybrid bearing system with thrust superconducting magnetic bearing and radial active electromagnetic bearing

    NASA Astrophysics Data System (ADS)

    Nicolsky, R.; Pereira, A. S.; de Andrade, R.; David, D. F. B.; Santisteban, J. A.; Stephan, R. M.; Ripper, A.; Gawalek, W.; Habisreuther, T.; Strasser, T.

    A superconducting/electromagnetic hybrid bearing system is currently under development and test. This system consists of a thrust superconducting magnetic bearing and a double radial active electromagnetic bearing/motor devices. The thrust bearing has been designed using NdFeB permanent magnets levitating on a set of superconducting monoliths of YBCO, prepared by top seeded melt texturing technique, which supports the weight of the rotor. The bearing/motor devices were conceived as 4-pole 2-phase induction machine using stator windings for delivering torque and radial positioning simultaneously. Using this superconducting axial bearing and the active bearings for the rotor radial positioning, a fully levitating vertical-shaft inductive machine has been tested. The tests were successful in reaching a controlled levitation up to 6,300 rpm.

  8. Protection of high temperature superconducting thin-films in a semiconductor processing environment

    SciTech Connect

    Xu, Yizi; Fiske, R.; Sanders, S.C.; Ekin, J.W.

    1996-12-31

    Annealing studies have been carried out for high temperature superconductor YBaCuO{sub 7{minus}{delta}} in a reducing ambient, in order to identify insulator layer(s) that will effectively protect the superconducting film in the hostile environment. While a layer of magnesium oxide (MgO) sputter deposited directly on YBaCuO{sub 7{minus}{delta}} film provides some degree of protection, the authors found that a composite structure of YBCO/SrTiO{sub 3}/MgO, where the SrTiO{sub 3} was grown by laser ablation immediately following YBCO deposition (in-situ process), was much more effective. They also address the need for a buffer layer between YBCO and aluminum (Al) during annealing. Al is most commenly used for semiconductor metalization, but is known to react readily with YBCO at elevated temperatures. The authors found that the most effective buffer layers are platinum (Pt) and gold/platinum (Au/Pt).

  9. Superconducting magnets

    SciTech Connect

    Willen, E.; Dahl, P.; Herrera, J.

    1985-01-01

    This report provides a self-consistent description of a magnetic field in the aperture of a superconducting magnet and details how this field can be calculated in a magnet with cos theta current distribution in the coils. A description of an apparatus that can be used to measure the field uniformity in the aperture has been given. Finally, a detailed description of the magnet being developed for use in the Superconducting Super Collider is given. When this machine is built, it will be by far the largest application of superconductivity to date and promises to make possible the experimental discoveries needed to understand the basic laws of nature governing the world in which we live.

  10. Anisotropic Landau-Lifshitz-Gilbert models of dissipation in qubits

    NASA Astrophysics Data System (ADS)

    Crowley, Philip J. D.; Green, A. G.

    2016-12-01

    We derive a microscopic model for dissipative dynamics in a system of mutually interacting qubits coupled to a thermal bath that generalizes the dissipative model of Landau-Lifshitz-Gilbert to the case of anisotropic bath couplings. We show that the dissipation acts to bias the quantum trajectories towards a reduced phase space. This model applies to a system of superconducting flux qubits whose coupling to the environment is necessarily anisotropic. We study the model in the context of the D-Wave computing device and show that the form of environmental coupling in this case produces dynamics that are closely related to several models proposed on phenomenological grounds.

  11. Quench propagation studies using a small bifilar YBCO coil

    SciTech Connect

    Shiroyanagi, Y.; Sampson, W. B.; Ghosh, Arup

    2012-01-01

    Quench propagation was studied in a small bifilar coil wound from YBCO tape. Measurements were made at 77 K in self-field and at 4.2 K with an applied field. The velocity of quench propagation at 4.2 K was observed to be about an order of magnitude faster than at 77 K both in the longitudinal and transverse directions. During the course of this experiment the conductor damage limit characterized by ∫I2dt was also estimated. Details of the experiment and results are presented in this paper

  12. Microstructure and levitation properties of floating zone melted YBCO samples

    SciTech Connect

    Bashkirov, Yu.A.; Fleishman, L.S.; Vdovin, A.B.; Zubritsky, I.A.; Smirnov, V.V.; Vinogradov, A.V.

    1994-07-01

    Radiation zone melting has been used to produce texture in sintered YBCO cylindrical samples. Microstructural analysis by electron microscopy and pole figure measurements reveals that the production process gives rise to a preferential orientation within large domains. D.C. transport measurements show that changes in alignment orientation can result in the inability to carry a transport current. Both a.c. magnetic field shielding and levitation properties are substantially improved by the floating zone melting, the levitation force being increased with the texture domain size growth.

  13. PREFACE: Superconducting materials Superconducting materials

    NASA Astrophysics Data System (ADS)

    Charfi Kaddour, Samia; Singleton, John; Haddad, Sonia

    2011-11-01

    The discovery of superconductivity in 1911 was a great milestone in condensed matter physics. This discovery has resulted in an enormous amount of research activity. Collaboration among chemists and physicists, as well as experimentalists and theoreticians has given rise to very rich physics with significant potential applications ranging from electric power transmission to quantum information. Several superconducting materials have been synthesized. Crucial progress was made in 1987 with the discovery of high temperature superconductivity in copper-based compounds (cuprates) which have revealed new fascinating properties. Innovative theoretical tools have been developed to understand the striking features of cuprates which have remained for three decades the 'blue-eyed boy' for researchers in superconductor physics. The history of superconducting materials has been notably marked by the discovery of other compounds, particularly organic superconductors which despite their low critical temperature continue to attract great interest regarding their exotic properties. Last but not least, the recent observation of superconductivity in iron-based materials (pnictides) has renewed hope in reaching room temperature superconductivity. However, despite intense worldwide studies, several features related to this phenomenon remain unveiled. One of the fundamental key questions is the mechanism by which superconductivity takes place. Superconductors continue to hide their 'secret garden'. The new trends in the physics of superconductivity have been one of the two basic topics of the International Conference on Conducting Materials (ICoCoM2010) held in Sousse,Tunisia on 3-7 November 2010 and organized by the Tunisian Physical Society. The conference was a nice opportunity to bring together participants from multidisciplinary domains in the physics of superconductivity. This special section contains papers submitted by participants who gave an oral contribution at ICoCoM2010

  14. Sputter Synthesis of c-axis YBCO Films with Excellent Surface Smoothness and Fabrication of Sandwich type Junctions with Interface Engineered Barrier

    NASA Astrophysics Data System (ADS)

    Ohk, K.; Iwashita, N.; Kikunaga, K.; Okuda, T.; Obara, K.; Terada, N.

    2006-06-01

    Flat surface is essential to base electrodes of sandwich type Josephson junctions. In the present study, c-axis YBa2Cu3O7 (c-YBCO) films with excellent surface smoothness were fabricated by off-axis sputtering. For the flat surfaces, key parameters in the sputtering process were growth temperature, atmosphere conditions and surface nature of substrates. The correlation between the sputtering conditions and the characteristic of the c-YBCO films reveal the following phenomena; i) The films deposited at low temperature of 660 °C showed a low zero-resistance temperature because of a poor connection between the c-axis crystallites. Surfaces of these low temperature grown films involve large and rectangular shaped a-axis grains, thereby the peak-to-valley (PV) amplitude of the surface was beyond 80 nm. The experiments indicate that the growth of the grains should be caused by low surface diffusion of adatoms at the low growth temperature. ii) Contrarily, at high Ts above 770 °C, a serious deviation of film composition from the stoichiometry took places, which also promoted an outgrowth of a-axis grains. Consequently, the high temperature grown films had seriously rough surfaces (PV amplitude > 25 nm). iii) The growth at the optimised Ts of 765 °C led a remarkable reduction of surface roughness (root-mean-square (RMS) of the roughness < 1.8 nm) without any degradation of superconducting properties. The achieved surface morphology is classified as one of the smoothest surfaces of the YBCO film grow by sputtering. iv) A density of the a-axis outgrowth was related to the surface defects of the substrate. The usage of SrTiO3 (100) plane consists of atomically flat and wide terraces and unit-cell high steps resulted in almost outgrowth-face surface with an excellent smoothness (PV amplitude < 10 nm, RMS of the roughness < 1.0 nm).

  15. A fully superconducting bearing system for flywheel applications

    NASA Astrophysics Data System (ADS)

    Xu, Ke-xi; Wu, Dong-jie; Jiao, Y. L.; Zheng, M. H.

    2016-06-01

    A fully superconducting magnetic suspension structure has been designed and constructed for the purpose of superconducting bearing applications in flywheel energy storage systems. A thrust type bearing and two journal type bearings, those that are composed of melt textured high-Tc superconductor YBCO bulks and Nd-Fe-B permanent magnets, are used in the bearing system. The rotor dynamical behaviors, including critical speeds and rotational loss, are studied. Driven by a variable-frequency three-phase induction motor, the rotor shaft attached with a 25 kg flywheel disc can be speeded up to 15 000 rpm without serious resonance occurring. Although the flywheel system runs stably in the supercritical speeds region, very obvious rotational loss is unavoidable. The loss mechanism has been discussed in terms of eddy current loss and hysteresis loss.

  16. Mirage phenomena in superconducting quantum corrals

    NASA Astrophysics Data System (ADS)

    Schmid, M.; Kampf, A. P.

    2005-09-01

    [Dedicated to Bernhard Mühlschlegel on the occasion ofhis 80th birthday]We investigate the local density of states and the order parameter structure inside an elliptic quantum corral on surfaces of isotropic and anisotropic superconductors. The Bogoliubov-de Gennes equations are solved in the presence of non-magnetic and magnetic impurities. We observe and discuss a variety of mirage and anti-mirage phenomena, which specifically reflect the nature of the superconducting pairing state.

  17. Fabrication of YBCO-LSMO-YBCO Lateral Structure with AFM Lithography

    NASA Astrophysics Data System (ADS)

    Ishii, K.; Tachiki, M.; Ooi, S.; Hirata, K.

    We have tried to make the superconductor/half metal/superconductor (SC/HF/SC) Josephson junction to make clear a long range proximity effect. The structure was consisted of high-Tc superconductor YBa2Cu3O7-x and half metallic ferromagnet La0.7Sr0.3MnO3 thin films deposited by pulse laser deposition on SrTiO3(100) single crystal substrates. The SC/HF/SC lateral structure was made by scratching with the atomic force microscope (AFM) probe. We could cut the ditch which has 30 nm width and 50 nm depth. We have investigated the I-V and R-T measurements of the structure. The structure after the fabrication did not show the superconducting state and we could not find the Josephson current.

  18. Superconducting Microelectronics.

    ERIC Educational Resources Information Center

    Henry, Richard W.

    1984-01-01

    Discusses superconducting microelectronics based on the Josephson effect and its advantages over conventional integrated circuits in speed and sensitivity. Considers present uses in standards laboratories (voltage) and in measuring weak magnetic fields. Also considers future applications in superfast computer circuitry using Superconducting…

  19. Superconducting magnets

    SciTech Connect

    Not Available

    1994-08-01

    This report discusses the following topics on superconducting magnets: D19B and -C: The next steps for a record-setting magnet; D20: The push beyond 10 T: Beyond D20: Speculations on the 16-T regime; other advanced magnets for accelerators; spinoff applications; APC materials development; cable and cabling-machine development; and high-{Tc} superconductor at low temperature.

  20. Superconducting Microelectronics.

    ERIC Educational Resources Information Center

    Henry, Richard W.

    1984-01-01

    Discusses superconducting microelectronics based on the Josephson effect and its advantages over conventional integrated circuits in speed and sensitivity. Considers present uses in standards laboratories (voltage) and in measuring weak magnetic fields. Also considers future applications in superfast computer circuitry using Superconducting…

  1. Growth of YBCO single crystals by the self-flux technique

    NASA Astrophysics Data System (ADS)

    Liang, Ruixing; Bonn, Douglas A.; Hardy, Walter N.

    2012-07-01

    Preparation of high purity, highly perfect and homogeneous YBa2Cu3O6+ δ (YBCO) single crystals is a lengthy procedure that consists of five major steps. They are (a) fabrication of BaZrO3 ceramic crucibles, (b) self-flux growth of YBCO crystals using BaZrO3 crucibles, (c) setting of the oxygen content in the crystals, (d) removal of twins and homogenisation of oxygen content, and (e) formation of oxygen vacancy ordered superstructures by low temperature annealing. To obtain BaZrO3 ceramic impervious to the BaO-CuO melt, the volume of the grain boundary glass phase must be reduced to a very low level through the use of high purity starting materials and precise BaO:ZrO mole ratio control. The best quality YBCO crystals are obtained by slow cooling of YO1.5-BaO-CuO melt in the primary crystallisation region of YBCO. Oxygen content in heavily twinned orthorhombic YBCO is inhomogeneous due to the stress caused by twins. Therefore, homogenisation annealing must be carried out after removal of twin boundaries or, alternatively, under conditions where YBCO is tetragonal. In high purity YBCO, randomly distributed oxygen vacancies are the main source of charge carrier scattering. However, ordered superstructures of oxygen vacancies with significantly lower scattering rates can be generated by careful annealing at low temperatures.

  2. Thermal stability of NdBCO/YBCO/MgO thin film seeds

    NASA Astrophysics Data System (ADS)

    Volochová, D.; Kavečanský, V.; Antal, V.; Diko, P.; Yao, X.

    2016-04-01

    Thermal stability of the Nd1+x Ba2-x Cu3O7-δ (Nd-123 or NdBCO) thin films deposited on MgO substrate, with YBa2Cu3O7-δ (Y-123 or YBCO) buffer layer (NdBCO/YBCO/MgO thin film), has been experimentally studied in order to determine the optimal film thickness acting as seed for bulk YBCO growth. YBCO bulk superconductors with Y2BaCuO5 (Y-211) and CeO2 addition were prepared by the top seeded melt growth process in a chamber furnace using NdBCO/YBCO/MgO thin film seeds of different thicknesses (200-700 nm with 20 nm YBCO buffer layer) and different maximum temperatures, T max. The maximum temperatures varied in the range of 1040 °C-1125 °C. The highest thermal stability 1118 °C was observed in the case of NdBCO/YBCO/MgO thin film of 300 nm thickness. These results are corroborated with differential scanning calorimetry and high temperature x-ray diffraction measurements, as well as microstructure observations.

  3. Magnetism in EuBCO and YBCO vortex states near and below Tc

    NASA Astrophysics Data System (ADS)

    Schwartz, R.; Browne, M. C.; Boekema, C.

    2012-02-01

    By means of MaxEnt-μSR [1] analysis, we investigate transverse field μSR data [2] of EuBa2Cu3O7-δgEuBCO; Tc = 93 K). Our focus is on a temperature interval near Tc to search for precursor effects, [3] and for predicted [4a] pseudogap loop currents above and below Tc, already observed [4b] above Tc for GdBCO. Further, we continue to study the field-direction dependence of the predicted [5a] and observed [5b] antiferromagnetism (AF) below 0.5Tc for the vortex states in c-axis-oriented YBCO. This AF in and near the vortex cores is likely three-dimensional. In sum, magnetic roots of cuprate superconductivity are well plausible. Research is supported by LANL-DOE, REU-NSF and AFC. [4pt] [1] C Boekema and MC Browne, AIP Conf Proc #1073 (2008) 260.[0pt] [2] DW Cooke et al, Phys Rev B 39 (1989) 2748.[0pt] [3] B Aguilar, C Boekema et al, Bull Am Phys Soc 37 (1992).[0pt] [4a] CM Varma, Phys Rev Lett 83 (1999) 3538.[0pt] [4b] T Songatikamas et al, J Supercond & Novel Magn 23 (2010) 793.[0pt] [5a] S-C Zhang, Science 275 (1997) 1089; H-D Chen et al, Phys Rev B70 (2004) 024516.[0pt] [5b] C. Boekema et al, J Phys Conf Series, 150 (2009) 052022. http://jpcs.iop.org/LT25

  4. Thin YBCO films on ? (001) substrates grown by injection MOCVD

    NASA Astrophysics Data System (ADS)

    Abrutis, A.; Sénateur, J. P.; Weiss, F.; Kubilius, V.; Bigelyte, V.; Saltyte, Z.; Vengalis, B.; Jukna, A.

    1997-12-01

    YBCO thin (about 0953-2048/10/12/021/img10) films were deposited at 0953-2048/10/12/021/img11 on 0953-2048/10/12/021/img12 (001) by single-source injection CVD. Precisely controlled microamounts of organometallic 0953-2048/10/12/021/img13-diketonates dissolved in an organic solvent were injected sequentially into the evaporator by means of a computer-driven injector and the resultant vapour was transported into the deposition zone. The influence of the vapour phase composition on films' properties was investigated. A mixture of 0953-2048/10/12/021/img14 and 0953-2048/10/12/021/img15-oriented YBCO crystallites exists in all deposited films and its ratio depends on the vapour phase composition. For both a and c perpendicular crystallites only 0953-2048/10/12/021/img16 in-plane orientation with respect to substrate axes was found. Bidirectional twinning was established in the crystallites of both types. 0953-2048/10/12/021/img17 of the films (about 90 K) was almost independent of the vapour phase composition in the studied range. However, the critical current density 0953-2048/10/12/021/img18 depended clearly on the vapour phase composition in relation to the 0953-2048/10/12/021/img19 ratio variation. 0953-2048/10/12/021/img18 of the films varied in the range 0953-2048/10/12/021/img21.

  5. Superconducting bolometers: High-T(sub c) and low-T(sub c)

    NASA Astrophysics Data System (ADS)

    Richards, P. L.

    1991-04-01

    A description is given of recent work at Berkeley on superconducting detectors and mixers for infrared and millimeter wavelengths. The first report is a review article which summarizes the status of development of superconducting components for infrared and millimeter wave receivers. Next, a report is given on measurements and theoretical modeling of the absorptivity (surface resistance) of high quality epitaxial films of the high-(Tc) superconductor YBCO from 750 GHz to 21 THz. The next report describes measurements of the thermal boundary resistance between YBCO films and various substrates. This resistance is much larger than expected from the acoustic impedance mismatch model and gives a thermal time constant in the nanosecond range for typical YBCO films. Then, there are reports on the design and experimental performance of two different types of high-(Tc) bolometric detectors. One is a conventional bolometer with a gold-black absorber. The other is an antenna coupled microbolometer. The properties of a low-(Tc) microbolometer are also described. The last reports describe accurate measurements and also theoretical modeling of an SIS quasiparticle waveguide mixer for W-band which uses very high quality Ta junctions. The best mixer noise is only 1.3 times the quantum limit. Both the mixer gain and the noise are in quantitative agreement with the quantum theory.

  6. Dynamic investigations on the influence of epitaxial strain on the superconducting transition in YBa2Cu3O7-x

    NASA Astrophysics Data System (ADS)

    Hühne, R.; Okai, D.; Dörr, K.; Trommler, S.; Herklotz, A.; Holzapfel, B.; Schultz, L.

    2008-07-01

    YBa2Cu3O7-x (YBCO) films have been prepared on piezoelectric (001) Pb(Mg1/3Nb2/3)0.72Ti0.28O3 (PMN-PT) substrates for dynamic investigations on the influence of strain on the superconducting transition temperature. The YBCO films deposited by off-axis pulsed laser deposition showed a perfect epitaxial growth on the piezocrystals but also significant surface roughness due to the miscut of the substrate. The in-plane lattice constant of the PMN-PT substrate was varied dynamically by the application of an electric field of <=10 kV cm-1. As a result, a reversible shift of the superconducting transition by about 0.1 K was found on an optimally doped YBCO film for an applied strain of 0.05%. The results show for the first time that this approach is suitable for studying the strain dependence of superconducting properties in detail.

  7. Inter-strand current sharing and ac loss measurements in superconducting YBCO Roebel cables

    DOE PAGES

    sumption, Mike; Majoros, Milan; Collings, E. W.; ...

    2014-11-07

    A Roebel cable, one twist pitch long, was modified from its as-received state by soldering copper strips between the strands to provide inter-strand connections enabling current sharing. Various DC transport currents (representing different percentages of its critical current) were applied to a single strand of such a modified cable at 77 K in a liquid nitrogen bath. Simultaneous monitoring of I–V curves in different parts of the strand as well as in its interconnections with other strands was made using a number of sensitive Keithley nanovoltmeters in combination with a multichannel high-speed data acquisition card, all controlled via LabView software.more » Current sharing onset was observed at about 1.02 of strand Ic. At a strand current of 1.3Ic about 5% of the current was shared through the copper strip interconnections. A finite element method modeling was performed to estimate the inter-strand resistivities required to enable different levels of current sharing. The relative contributions of coupling and hysteretic magnetization (and loss) were compared, and for our cable and tape geometry, and at dB/dt=1 T s-1, and our inter-strand resistance of 0.77 mΩ, (enabling a current sharing of 5% at 1.3Ic ) the coupling component was 0.32% of the hysteretic component. However, inter-strand contact resistance values of 100–1000 times smaller (close to those of NbTi and Nb3Sn based accelerator cables) would make the coupling components comparable in size to the hysteretic components.« less

  8. Inter-strand current sharing and ac loss measurements in superconducting YBCO Roebel cables

    DOE PAGES

    Majoros, M.; Sumption, M. D.; Collings, E. W.; ...

    2015-04-08

    A Roebel cable, one twist pitch long, was modified from its as-received state by soldering copper strips between the strands to provide inter-strand connections enabling current sharing. Various DC transport currents (representing different percentages of its critical current) were applied to a single strand of such a modified cable at 77 K in a liquid nitrogen bath. Simultaneous monitoring of I–V curves in different parts of the strand as well as in its interconnections with other strands was made using a number of sensitive Keithley nanovoltmeters in combination with a multichannel high-speed data acquisition card, all controlled via LabView software.more » Current sharing onset was observed at about 1.02 of strand Ic. At a strand current of 1.3Ic about 5% of the current was shared through the copper strip interconnections. A finite element method modeling was performed to estimate the inter-strand resistivities required to enable different levels of current sharing. The relative contributions of coupling and hysteretic magnetization (and loss) were compared, and for our cable and tape geometry, and at dB/dt=1 T s-1, and our inter-strand resistance of 0.77 mΩ, (enabling a current sharing of 5% at 1.3Ic) the coupling component was 0.32% of the hysteretic component. However, inter-strand contact resistance values of 100–1000 times smaller (close to those of NbTi and Nb3Sn based accelerator cables) would make the coupling components comparable in size to the hysteretic components.« less

  9. Inter-strand current sharing and ac loss measurements in superconducting YBCO Roebel cables

    NASA Astrophysics Data System (ADS)

    Majoros, M.; Sumption, M. D.; Collings, E. W.; Long, N. J.

    2015-05-01

    A Roebel cable, one twist pitch long, was modified from its as-received state by soldering copper strips between the strands to provide inter-strand connections enabling current sharing. Various DC transport currents (representing different percentages of its critical current) were applied to a single strand of such a modified cable at 77 K in a liquid nitrogen bath. Simultaneous monitoring of I-V curves in different parts of the strand as well as in its interconnections with other strands was made using a number of sensitive Keithley nanovoltmeters in combination with a multi-channel high-speed data acquisition card, all controlled via LabView software. Current sharing onset was observed at about 1.02 of strand Ic. At a strand current of 1.3Ic about 5% of the current was shared through the copper strip interconnections. A finite element method modeling was performed to estimate the inter-strand resistivities required to enable different levels of current sharing. The relative contributions of coupling and hysteretic magnetization (and loss) were compared, and for our cable and tape geometry, and at dB/dt = 1 T s-1, and our inter-strand resistance of 0.77 mΩ, (enabling a current sharing of 5% at 1.3Ic ) the coupling component was 0.32% of the hysteretic component. However, inter-strand contact resistance values of 100-1000 times smaller (close to those of NbTi and Nb3Sn based accelerator cables) would make the coupling components comparable in size to the hysteretic components.

  10. Inter-strand current sharing and ac loss measurements in superconducting YBCO Roebel cables

    SciTech Connect

    sumption, Mike; Majoros, Milan; Collings, E. W.; Van der Laan, D. C.

    2014-11-07

    A Roebel cable, one twist pitch long, was modified from its as-received state by soldering copper strips between the strands to provide inter-strand connections enabling current sharing. Various DC transport currents (representing different percentages of its critical current) were applied to a single strand of such a modified cable at 77 K in a liquid nitrogen bath. Simultaneous monitoring of I–V curves in different parts of the strand as well as in its interconnections with other strands was made using a number of sensitive Keithley nanovoltmeters in combination with a multichannel high-speed data acquisition card, all controlled via LabView software. Current sharing onset was observed at about 1.02 of strand Ic. At a strand current of 1.3Ic about 5% of the current was shared through the copper strip interconnections. A finite element method modeling was performed to estimate the inter-strand resistivities required to enable different levels of current sharing. The relative contributions of coupling and hysteretic magnetization (and loss) were compared, and for our cable and tape geometry, and at dB/dt=1 T s-1, and our inter-strand resistance of 0.77 mΩ, (enabling a current sharing of 5% at 1.3Ic ) the coupling component was 0.32% of the hysteretic component. However, inter-strand contact resistance values of 100–1000 times smaller (close to those of NbTi and Nb3Sn based accelerator cables) would make the coupling components comparable in size to the hysteretic components.

  11. Inter-strand current sharing and ac loss measurements in superconducting YBCO Roebel cables

    SciTech Connect

    Majoros, M.; Sumption, M. D.; Collings, E. W.; Long, N. J.

    2015-04-08

    A Roebel cable, one twist pitch long, was modified from its as-received state by soldering copper strips between the strands to provide inter-strand connections enabling current sharing. Various DC transport currents (representing different percentages of its critical current) were applied to a single strand of such a modified cable at 77 K in a liquid nitrogen bath. Simultaneous monitoring of I–V curves in different parts of the strand as well as in its interconnections with other strands was made using a number of sensitive Keithley nanovoltmeters in combination with a multichannel high-speed data acquisition card, all controlled via LabView software. Current sharing onset was observed at about 1.02 of strand Ic. At a strand current of 1.3Ic about 5% of the current was shared through the copper strip interconnections. A finite element method modeling was performed to estimate the inter-strand resistivities required to enable different levels of current sharing. The relative contributions of coupling and hysteretic magnetization (and loss) were compared, and for our cable and tape geometry, and at dB/dt=1 T s-1, and our inter-strand resistance of 0.77 mΩ, (enabling a current sharing of 5% at 1.3Ic) the coupling component was 0.32% of the hysteretic component. However, inter-strand contact resistance values of 100–1000 times smaller (close to those of NbTi and Nb3Sn based accelerator cables) would make the coupling components comparable in size to the hysteretic components.

  12. Grain morphology of YBCO coated superconductors prepared by spin process on Ni substrate

    NASA Astrophysics Data System (ADS)

    Liu, C. F.; Du, S. J.; Yan, G.; Xi, W.; Wu, X.; Pang, Y.; Wang, F. Y.; Liu, X. H.; Feng, Y.; Zhang, P. X.; Wu, X. Z.; Zhou, L.

    2003-04-01

    The YBCO thick films with c-axis preferred orientation were prepared by spin and printing processes on Ni substrates (including cold rolling Ni, cube textured Ni, and cube textured Ni+ self-oxided NiO ). The results show that the chrysanthemum (or spherulite) and polygon morphology grains dominate the microstructure of YBCO films. The chrysanthemum size is about 0.2-0.5 mm range, some reaches 1 mm, and polygon grains normally are placed in the center of the chrysanthemum grains. No chrysanthemum grains appear in the thick films prepared on the substrate with Ag or YBCO intermediate layers.

  13. In Situ Creation of Nanoparticles from YBCO by Pulsed Laser Deposition (Postprint)

    DTIC Science & Technology

    2012-02-01

    entailed pulsed laser deposition (PLD) of YBCO at a high background pressure of 5 Torr O2. The sizes of the nanoparticles range from ~3 to 5 nm and...pulsed laser deposition (PLD) of YBCO at a high background pressure of 5 Torr O2. The sizes of the nanoparticles range from 3 to 5 nm and are typical...are extremely small pieces of matter that have dimensions on the order of a few nm . It may well be possible to use nanoparti- cles of YBCO itself as

  14. Flux Pinning Effects of Y2O3 Nanoparticulate Dispersions in Multilayered YBCO Thin Films

    DTIC Science & Technology

    2012-02-01

    substrates with a Y2O3 nanoparticulate pseudo-layer thickness ranging from 0.2 to 1.4 nm , and YBCO layer thickness varying from 7 to 50 nm . Scanning...with a Y2O3 nanoparticulate pseudo-layer thickness ranging from 0.2 to 1.4 nm , and YBCO layer thickness varying from 7 to 50 nm . Scanning electron...2.0 nm [3,4] compared to about 0.7 nm for Y2O3.4. Conclusion The use of Y2O3 nanoparticulates showed potential as flux pinning centers in YBCO thin

  15. Tailoring Superconductivity with Quantum Dislocations.

    PubMed

    Li, Mingda; Song, Qichen; Liu, Te-Huan; Meroueh, Laureen; Mahan, Gerald D; Dresselhaus, Mildred S; Chen, Gang

    2017-08-09

    Despite the established knowledge that crystal dislocations can affect a material's superconducting properties, the exact mechanism of the electron-dislocation interaction in a dislocated superconductor has long been missing. Being a type of defect, dislocations are expected to decrease a material's superconducting transition temperature (Tc) by breaking the coherence. Yet experimentally, even in isotropic type I superconductors, dislocations can either decrease, increase, or have little influence on Tc. These experimental findings have yet to be understood. Although the anisotropic pairing in dirty superconductors has explained impurity-induced Tc reduction, no quantitative agreement has been reached in the case a dislocation given its complexity. In this study, by generalizing the one-dimensional quantized dislocation field to three dimensions, we reveal that there are indeed two distinct types of electron-dislocation interactions. Besides the usual electron-dislocation potential scattering, there is another interaction driving an effective attraction between electrons that is caused by dislons, which are quantized modes of a dislocation. The role of dislocations to superconductivity is thus clarified as the competition between the classical and quantum effects, showing excellent agreement with existing experimental data. In particular, the existence of both classical and quantum effects provides a plausible explanation for the illusive origin of dislocation-induced superconductivity in semiconducting PbS/PbTe superlattice nanostructures. A quantitative criterion has been derived, in which a dislocated superconductor with low elastic moduli and small electron effective mass and in a confined environment is inclined to enhance Tc. This provides a new pathway for engineering a material's superconducting properties by using dislocations as an additional degree of freedom.

  16. Anisotropic Artificial Impedance Surfaces

    NASA Astrophysics Data System (ADS)

    Quarfoth, Ryan Gordon

    Anisotropic artificial impedance surfaces are a group of planar materials that can be modeled by the tensor impedance boundary condition. This boundary condition relates the electric and magnetic field components on a surface using a 2x2 tensor. The advantage of using the tensor impedance boundary condition, and by extension anisotropic artificial impedance surfaces, is that the method allows large and complex structures to be modeled quickly and accurately using a planar boundary condition. This thesis presents the theory of anisotropic impedance surfaces and multiple applications. Anisotropic impedance surfaces are a generalization of scalar impedance surfaces. Unlike the scalar version, anisotropic impedance surfaces have material properties that are dependent on the polarization and wave vector of electromagnetic radiation that interacts with the surface. This allows anisotropic impedance surfaces to be used for applications that scalar surfaces cannot achieve. Three of these applications are presented in this thesis. The first is an anisotropic surface wave waveguide which allows propagation in one direction, but passes radiation in the orthogonal direction without reflection. The second application is a surface wave beam shifter which splits a surface wave beam in two directions and reduces the scattering from an object placed on the surface. The third application is a patterned surface which can alter the scattered radiation pattern of a rectangular shape. For each application, anisotropic impedance surfaces are constructed using periodic unit cells. These unit cells are designed to give the desired surface impedance characteristics by modifying a patterned metallic patch on a grounded dielectric substrate. Multiple unit cell geometries are analyzed in order to find the setup with the best performance in terms of impedance characteristics and frequency bandwidth.

  17. Anisotropic Nanoparticles and Anisotropic Surface Chemistry.

    PubMed

    Burrows, Nathan D; Vartanian, Ariane M; Abadeer, Nardine S; Grzincic, Elissa M; Jacob, Lisa M; Lin, Wayne; Li, Ji; Dennison, Jordan M; Hinman, Joshua G; Murphy, Catherine J

    2016-02-18

    Anisotropic nanoparticles are powerful building blocks for materials engineering. Unusual properties emerge with added anisotropy-often to an extraordinary degree-enabling countless new applications. For bottom-up assembly, anisotropy is crucial for programmability; isotropic particles lack directional interactions and can self-assemble only by basic packing rules. Anisotropic particles have long fascinated scientists, and their properties and assembly behavior have been the subjects of many theoretical studies over the years. However, only recently has experiment caught up with theory. We have begun to witness tremendous diversity in the synthesis of nanoparticles with controlled anisotropy. In this Perspective, we highlight the synthetic achievements that have galvanized the field, presenting a comprehensive discussion of the mechanisms and products of both seed-mediated and alternative growth methods. We also address recent breakthroughs and challenges in regiospecific functionalization, which is the next frontier in exploiting nanoparticle anisotropy.

  18. Color superconductivity

    SciTech Connect

    Wilczek, F.

    1997-09-22

    The asymptotic freedom of QCD suggests that at high density - where one forms a Fermi surface at very high momenta - weak coupling methods apply. These methods suggest that chiral symmetry is restored and that an instability toward color triplet condensation (color superconductivity) sets in. Here I attempt, using variational methods, to estimate these effects more precisely. Highlights include demonstration of a negative pressure in the uniform density chiral broken phase for any non-zero condensation, which we take as evidence for the philosophy of the MIT bag model; and demonstration that the color gap is substantial - several tens of MeV - even at modest densities. Since the superconductivity is in a pseudoscalar channel, parity is spontaneously broken.

  19. SUPERCONDUCTING PHOTOINJECTOR

    SciTech Connect

    BEN-ZVI,I.; BURRILL, A.; CALAGA, R.; CHANG, X.; GROVER, R.; GUPTA, R.; HAHN, H.; HAMMONS, L.; KAYRAN, D.; KEWISCH, J.; LAMBIASE, R.; LITVINENKO, V.; MCINTYRE, G.; NAIK, D.; PATE, D.; PHILLIPS, D.; POZDEYEV, E.; RAO, T.; SMEDLEY, J.; THAN, R.; TODD, R.; WEISS, D.; WU, Q.; ZALTSMAN, A.; ET AL.

    2007-08-26

    One of the frontiers in FEL science is that of high power. In order to reach power in the megawatt range, one requires a current of the order of one ampere with a reasonably good emittance. The superconducting laser-photocathode RF gun with a high quantum efficiency photocathode is the most natural candidate to provide this performance. The development of a 1/2 cell superconducting photoinjector designed to operate at up to a current of 0.5 amperes and beam energy of 2 MeV and its photocathode system are the subjects covered in this paper. The main issues are the photocathode and its insertion mechanism, the power coupling and High Order Mode damping. This technology is being developed at BNL for DOE nuclear physics applications such as electron cooling at high energy and electron ion colliders..

  20. High T(sub c) Superconducting Bolometer on Chemically Etched 7 Micrometer Thick Sapphire

    NASA Technical Reports Server (NTRS)

    Lakew, B.; Brasunas, J. C.; Pique, A.; Fettig, R.; Mott, B.; Babu, S.; Cushman, G. M.

    1997-01-01

    A transition-edge IR detector, using a YBa2Cu3O(7-x) (YBCO) thin film deposited on a chemically etched, 7 micrometer thick sapphire substrate has been built. To our knowledge it is the first such high T(sub c) superconducting (HTS) bolometer on chemically thinned sapphire. The peak optical detectivity obtained is l.2 x 10(exp 10) cmHz(sup 1/2)/W near 4Hz. Result shows that it is possible to obtain high detectivity with thin films on etched sapphire with no processing after the deposition of the YBCO film. We discuss the etching process and its potential for micro-machining sapphire and fabricating 2-dimensional detector arrays with suspended sapphire membranes. A 30 micrometer thick layer of gold black provided IR absorption. Comparison is made with the current state of the art on silicon substrates.

  1. Analysis of pulse propagation on high-T sub c superconducting transmission lines

    SciTech Connect

    Morisue, M.; Furusawa, S.; Asahina, J.; Kanasugi, A. )

    1991-03-01

    This paper reports on the propagation characteristics of high Tc superconducting microstrip transmission lines calculated from a view point of interconnection technology. a detail analysis is made to examine the attenuation and phase velocity of a pulse on a YBCO transmission line; taking into consideration of dielectric loss of the MgO substrate. The results of analysis are compared with the measured propagation constants of YBCO strip line fabricated on a MgO substrate. It is shown from the analysis that the effect of dielectric loss of a substrate to attenuation of microstrip line is dominant and can not be neglected as long as the authors use a MgO substrate.

  2. Effective method to control the levitation force and levitation height in a superconducting maglev system

    NASA Astrophysics Data System (ADS)

    Yang, Peng-Tao; Yang, Wan-Min; Wang, Miao; Li, Jia-Wei; Guo, Yu-Xia

    2015-11-01

    The influence of the width of the middle magnet in the permanent magnet guideways (PMGs) on the levitation force and the levitation height of single-domain yttrium barium copper oxide (YBCO) bulks has been investigated at 77 K under the zero field cooled (ZFC) state. It is found that the largest levitation force can be obtained in the system with the width of the middle magnet of the PMG equal to the size of the YBCO bulk when the gap between the YBCO bulk and PMG is small. Both larger levitation force and higher levitation height can be obtained in the system with the width of the middle magnet of the PMG larger than the size of the YBCO bulk. The stiffness of the levitation force between the PMG and the YBCO bulk is higher in the system with a smaller width of the middle magnet in the PMG. These results provide an effective way to control the levitation force and the levitation height for the superconducting maglev design and applications. Project supported by the National Natural Science Foundation of China (Grant Nos. 51342001 and 50872079), the Key-grant Project of Chinese Ministry of Education (Grant No. 311033), the Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20120202110003), the Innovation Team in Shaanxi Province, China (Grant No. 2014KTC-18), and the Fundamental Research Funds for the Central Universities, China (Grant Nos. GK201101001 and GK201305014), and the Outstanding Doctoral Thesis Foundation Project of Shaanxi Normal University, China (Grant Nos. X2011YB08 and X2012YB05).

  3. Anisotropic ray trace

    NASA Astrophysics Data System (ADS)

    Lam, Wai Sze Tiffany

    Optical components made of anisotropic materials, such as crystal polarizers and crystal waveplates, are widely used in many complex optical system, such as display systems, microlithography, biomedical imaging and many other optical systems, and induce more complex aberrations than optical components made of isotropic materials. The goal of this dissertation is to accurately simulate the performance of optical systems with anisotropic materials using polarization ray trace. This work extends the polarization ray tracing calculus to incorporate ray tracing through anisotropic materials, including uniaxial, biaxial and optically active materials. The 3D polarization ray tracing calculus is an invaluable tool for analyzing polarization properties of an optical system. The 3x3 polarization ray tracing P matrix developed for anisotropic ray trace assists tracking the 3D polarization transformations along a ray path with series of surfaces in an optical system. To better represent the anisotropic light-matter interactions, the definition of the P matrix is generalized to incorporate not only the polarization change at a refraction/reflection interface, but also the induced optical phase accumulation as light propagates through the anisotropic medium. This enables realistic modeling of crystalline polarization elements, such as crystal waveplates and crystal polarizers. The wavefront and polarization aberrations of these anisotropic components are more complex than those of isotropic optical components and can be evaluated from the resultant P matrix for each eigen-wavefront as well as for the overall image. One incident ray refracting or reflecting into an anisotropic medium produces two eigenpolarizations or eigenmodes propagating in different directions. The associated ray parameters of these modes necessary for the anisotropic ray trace are described in Chapter 2. The algorithms to calculate the P matrix from these ray parameters are described in Chapter 3 for

  4. Superconducting magnet

    NASA Technical Reports Server (NTRS)

    1985-01-01

    Extensive computer based engineering design effort resulted in optimization of a superconducting magnet design with an average bulk current density of approximately 12KA/cm(2). Twisted, stranded 0.0045 inch diameter NbTi superconductor in a copper matrix was selected. Winding the coil from this bundle facilitated uniform winding of the small diameter wire. Test coils were wound using a first lot of the wire. The actual packing density was measured from these. Interwinding voltage break down tests on the test coils indicated the need for adjustment of the wire insulation on the lot of wire subsequently ordered for construction of the delivered superconducting magnet. Using the actual packing densities from the test coils, a final magnet design, with the required enhancement and field profile, was generated. All mechanical and thermal design parameters were then also fixed. The superconducting magnet was then fabricated and tested. The first test was made with the magnet immersed in liquid helium at 4.2K. The second test was conducted at 2K in vacuum. In the latter test, the magnet was conduction cooled from the mounting flange end.

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  6. High performance YBCO films. Report for 25 February-25 May 1994

    SciTech Connect

    Denlinger, E.J.

    1994-05-25

    A Bi2O3-based glass composition was found suitable for use under typical YBCO deposition conditions, which is in a vacuum under partial oxygen pressure at about 750 deg C. It was experimently determined that a Ag capping layer thickness of about 5 microns is needed for use with this glass. This Ag thickness will prevent any degradation in the silver layer's conducting properties due to Ag/glass interaction during the glass firing operation at 640 deg C. Lanthanum aluminate samples with YBCO topped with a thin layer of strontium titanate (STO) were prepared by Neocera and had excellent YBCO surface resistance properties as measured with a dielectric resonator test system. These samples will be used to test the compatibility of the YBCO with the silver capping layer deposited over the STO.

  7. Real time optical observation of precursor phases during YBCO thin film growth

    NASA Astrophysics Data System (ADS)

    Koster, Gertjan; Huh, Jeong-Uk

    2005-03-01

    We report on our findings using real-time Fourier Transform Infrared (FTIR) radiance and reflectance measurements during high rate electron beam deposited [100 angstroms/sec] YBa2Cu3O7 (YBCO) films [ [i

  8. Correlation of AC Loss Data from Magnetic Susceptibility Measurements with YBCO Film Quality (Postprint)

    DTIC Science & Technology

    2012-02-01

    excimer laser operating at the KrF, 248 nm , wavelength. Substrates included LaAlO3 ( 100 ) and SrTiO3 ( 100 ) single crystal substrates as well as buffered...AFRL-RZ-WP-TP-2012-0100 CORRELATION OF AC LOSS DATA FROM MAGNETIC SUSCEPTIBILITY MEASUREMENTS WITH YBCO FILM QUALITY (POSTPRINT) Paul N...CORRELATION OF AC LOSS DATA FROM MAGNETIC SUSCEPTIBILITY MEASUREMENTS WITH YBCO FILM QUALITY (POSTPRINT) 5a. CONTRACT NUMBER In-house 5b. GRANT

  9. Superconducting Electronic Film Structures

    DTIC Science & Technology

    1991-02-14

    superconductors, yttrium , barium, copper, oxides, high, critical, temperature, thin films, tunneling, barriers, thallium, sputtering. 19. ABSTRACT (Continue on...50*C lower than that required for YBCO. In common with YBCO, the best films grew epitaxially with a c-axis orientation on SrTiO3 , LaAIO 3, and NdGaO 3...for c-axis growth were (001) faces of LaAIO 3, NdGaO 3 , SrTiO3 , MgO. yttria-stabilized ZrO2 (YSZ), 11 and (1102) sapphire. Low substrate

  10. Relationship between intrinsic surface resistance and critical current density of YBCO thin films with various thickness

    NASA Astrophysics Data System (ADS)

    Nakagawa, K.; Nakayama, S.; Saito, A.; Ono, S.; Kai, H.; Mukaida, M.; Honma, T.; Ohshima, S.

    2010-11-01

    We investigated the relationship between the intrinsic surface resistance (Rsint) and critical current density (Jc) of YBa2Cu3Oy (YBCO) film thinner than the penetration depth (λL). The measured YBCO films were deposited on CeO2-buffered r-cut Al2O3 substrates by the pulsed laser deposition method. The thicknesses of these films were 300, 200, and 100 nm, respectively. The Rsint means the surface resistance of YBCO film removing the loss by the impedance of the substrates. The effective surface resistance (Rseff) including the impedance of the substrate and the Jc of each YBCO film were measured using the dielectric resonator method at 21.8 GHz and the inductive method. We calculated Rsint by using phenomenological expressions and the Rseff value. The Rsint values of each YBCO film were almost the same in the measured temperature region. As a result, we found that Rsint was in inverse proportion to the Jc of YBCO film thinner than λL.

  11. On the superconducting gap structure of high-temperature superconductors by STM/STS

    NASA Astrophysics Data System (ADS)

    Kitazawa, K.; Sugawara, H.; Hasegawa, T.

    1996-05-01

    The tunneling spectra observed by STM on the HTSC's have been converging in terms of the superconducting gap energy values: 2 Δ/ kBTc=6 to 9. There are, however, still disagreements between the details of various results. Both d- and s-wave-like features have been claimed for the superconducting gap structure. Furthermore, both flat and V-shaped structures have been observed in the background conductance curve outside the superconducting gap. The major differences among various reports seem to be attributable to the difference in the top layer and in the carrier density of the sample. It is noted that those who observe on the BiO topmost plane in a Bi2212 crystal or on the CuO-chain plane of YBCO seem to be claiming the d-wave, and those who observe on different top planes the s-wave symmetry.

  12. Magnetic forces in high-Tc superconducting bearings

    NASA Technical Reports Server (NTRS)

    Moon, F. C.

    1991-01-01

    In September 1987, researchers at Cornell levitated a small rotor on superconducting bearings at 10,000 rpm. In April 1989, a speed of 120,000 rpm was achieved in a passive bearing with no active control. The bearing material used was YBa2Cu307. There is no evidence that the rotation speed has any significant effect on the lift force. Magnetic force measurements between a permanent rare-earth magnet and high T(sub c) superconducting material versus vertical and lateral displacements were made. A large hysteresis loop results for large displacements, while minor loops result for small displacements. These minor loops seem to give a slope proportional to the magnetic stiffness, and are probably indicative of flux pinning forces. Experiments of rotary speed versus time show a linear decay in a vacuum. Measurements of magnetic dipole over a high-T(sub c) superconducting disc of YBCO show that the lateral vibrations of levitated rotors were measured which indicates that transverse flux motion in the superconductor will create dissipation. As a result of these force measurements, an optimum shape for the superconductor bearing pads which gives good lateral and axial stability was designed. Recent force measurements on melt-quench processed superconductors indicate a substantial increase in levitation force and magnetic stiffness over free sintered materials. As a result, application of high-T(sub c) superconducting bearings are beginning to show great promise at this time.

  13. Effects of deposition rate and thickness on the properties of YBCO films deposited by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Shi, D. Q.; Ko, R. K.; Song, K. J.; Chung, J. K.; Choi, S. J.; Park, Y. M.; Shin, K. C.; Yoo, S. I.; Park, C.

    2004-02-01

    YBCO films with various thicknesses from 100 nm to 1.6 µm were deposited on single crystal SrTiO3 substrates by pulsed laser deposition (PLD). The effects of thickness and deposition rate—by means of controlling the pulsed laser frequency—on the critical current density (Jc) were studied. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to examine the orientation, crystallization and surface quality. The amount of a-axis YBCO component evaluated from the ratio of XRD chi-scan intensities of the a-axis and c-axis for the YBCO (102) plane increased as the YBCO film became thicker. SEM was used to analyse the surface of YBCO film, and it was shown that the surface of YBCO film became rougher with increasing thickness. There were many large singular outgrowths and networks of outgrowths on the surface of the YBCO films with thickness greater than 0.4 µm. The increased amount of a-axis YBCO component and the coarse microstructure of the thick YBCO film caused degradation of Jc with increasing thickness.

  14. Anisotropic contrast optical microscope

    NASA Astrophysics Data System (ADS)

    Peev, D.; Hofmann, T.; Kananizadeh, N.; Beeram, S.; Rodriguez, E.; Wimer, S.; Rodenhausen, K. B.; Herzinger, C. M.; Kasputis, T.; Pfaunmiller, E.; Nguyen, A.; Korlacki, R.; Pannier, A.; Li, Y.; Schubert, E.; Hage, D.; Schubert, M.

    2016-11-01

    An optical microscope is described that reveals contrast in the Mueller matrix images of a thin, transparent, or semi-transparent specimen located within an anisotropic object plane (anisotropic filter). The specimen changes the anisotropy of the filter and thereby produces contrast within the Mueller matrix images. Here we use an anisotropic filter composed of a semi-transparent, nanostructured thin film with sub-wavelength thickness placed within the object plane. The sample is illuminated as in common optical microscopy but the light is modulated in its polarization using combinations of linear polarizers and phase plate (compensator) to control and analyze the state of polarization. Direct generalized ellipsometry data analysis approaches permit extraction of fundamental Mueller matrix object plane images dispensing with the need of Fourier expansion methods. Generalized ellipsometry model approaches are used for quantitative image analyses. These images are obtained from sets of multiple images obtained under various polarizer, analyzer, and compensator settings. Up to 16 independent Mueller matrix images can be obtained, while our current setup is limited to 11 images normalized by the unpolarized intensity. We demonstrate the anisotropic contrast optical microscope by measuring lithographically defined micro-patterned anisotropic filters, and we quantify the adsorption of an organic self-assembled monolayer film onto the anisotropic filter. Comparison with an isotropic glass slide demonstrates the image enhancement obtained by our method over microscopy without the use of an anisotropic filter. In our current instrument, we estimate the limit of detection for organic volumetric mass within the object plane of ≈49 fg within ≈7 × 7 μm2 object surface area. Compared to a quartz crystal microbalance with dissipation instrumentation, where contemporary limits require a total load of ≈500 pg for detection, the instrumentation demonstrated here improves

  15. Molecular anisotropic magnetoresistance

    NASA Astrophysics Data System (ADS)

    Otte, Fabian; Heinze, Stefan; Mokrousov, Yuriy

    2015-12-01

    Using density functional theory calculations, we demonstrate that the effect of anisotropic magnetoresistance (AMR) can be enhanced by orders of magnitude with respect to conventional bulk ferromagnets in junctions containing molecules sandwiched between ferromagnetic leads. We study ballistic transport in metal-benzene complexes contacted by 3 d transition-metal wires. We show that a gigantic AMR can arise from spin-orbit coupling effects in the leads, drastically enhanced by orbital-symmetry filtering properties of the molecules. We further discuss how this molecular anisotropic magnetoresistance (MAMR) can be tuned by the proper choice of materials and their electronic properties.

  16. Anisotropic contrast optical microscope.

    PubMed

    Peev, D; Hofmann, T; Kananizadeh, N; Beeram, S; Rodriguez, E; Wimer, S; Rodenhausen, K B; Herzinger, C M; Kasputis, T; Pfaunmiller, E; Nguyen, A; Korlacki, R; Pannier, A; Li, Y; Schubert, E; Hage, D; Schubert, M

    2016-11-01

    An optical microscope is described that reveals contrast in the Mueller matrix images of a thin, transparent, or semi-transparent specimen located within an anisotropic object plane (anisotropic filter). The specimen changes the anisotropy of the filter and thereby produces contrast within the Mueller matrix images. Here we use an anisotropic filter composed of a semi-transparent, nanostructured thin film with sub-wavelength thickness placed within the object plane. The sample is illuminated as in common optical microscopy but the light is modulated in its polarization using combinations of linear polarizers and phase plate (compensator) to control and analyze the state of polarization. Direct generalized ellipsometry data analysis approaches permit extraction of fundamental Mueller matrix object plane images dispensing with the need of Fourier expansion methods. Generalized ellipsometry model approaches are used for quantitative image analyses. These images are obtained from sets of multiple images obtained under various polarizer, analyzer, and compensator settings. Up to 16 independent Mueller matrix images can be obtained, while our current setup is limited to 11 images normalized by the unpolarized intensity. We demonstrate the anisotropic contrast optical microscope by measuring lithographically defined micro-patterned anisotropic filters, and we quantify the adsorption of an organic self-assembled monolayer film onto the anisotropic filter. Comparison with an isotropic glass slide demonstrates the image enhancement obtained by our method over microscopy without the use of an anisotropic filter. In our current instrument, we estimate the limit of detection for organic volumetric mass within the object plane of ≈49 fg within ≈7 × 7 μm(2) object surface area. Compared to a quartz crystal microbalance with dissipation instrumentation, where contemporary limits require a total load of ≈500 pg for detection, the instrumentation demonstrated here improves

  17. Space applications of superconductivity

    NASA Technical Reports Server (NTRS)

    Sullivan, D. B.; Vorreiter, J. W.

    1979-01-01

    Some potential applications of superconductivity in space are summarized, e.g., the use of high field magnets for cosmic ray analysis or energy storage and generation, space applications of digital superconducting devices, such as the Josephson switch and, in the future, a superconducting computer. Other superconducting instrumentation which could be used in space includes: low frequency superconducting sensors, microwave and infrared detectors, instruments for gravitational studies, and high-Q cavities for use as stabilizing elements in clocks and oscillators.

  18. Anisotropic eddy viscosity models

    NASA Technical Reports Server (NTRS)

    Carati, D.; Cabot, W.

    1996-01-01

    A general discussion on the structure of the eddy viscosity tensor in anisotropic flows is presented. The systematic use of tensor symmetries and flow symmetries is shown to reduce drastically the number of independent parameters needed to describe the rank 4 eddy viscosity tensor. The possibility of using Onsager symmetries for simplifying further the eddy viscosity is discussed explicitly for the axisymmetric geometry.

  19. Superconducting-gap symmetry study using a/c boundary Josephson junctions in YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} films

    SciTech Connect

    Ishimaru, Y.; Wen, J.; Koshizuka, N.; Enomoto, Y.

    1997-05-01

    We have investigated gap symmetry of high-T{sub c} superconductors using Josephson junctions formed along a boundary of an a-axis-oriented YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} (YBCO) grain surrounded by c-axis-oriented YBCO grains (a/c boundary). There are two types of a/c boundary junctions; one is the boundary between (001) of a-axis-oriented grains and (100) of c-axis-oriented grains, and the other is the boundary between (001) of a-axis-oriented grains and (110) of c-axis-oriented grains. TEM observation shows clean, sharp, and nearly single-facet interface along the grain boundaries in both types. In the case of the (100)-(001) type a/c boundary junction, typical resistively shunted junction (RSJ)-type I-V curves, Shapiro steps under microwave irradiation, and Fraunhofer-like diffraction pattern of I{sub c} under magnetic field are observed, indicating that the boundary works as a Josephson junction. In the case of the (110)-(001)-type a/c boundary junction, typical RSJ type I-V curves and Shapiro steps under microwave irradiation are also observed. However, the diffraction pattern of I{sub c} under magnetic field has the minimum value at zero magnetic field. This property is analogous to one observed for a corner junction which is formed between Pb and YBCO. These results show that the (110) of YBCO has a phase difference of {pi} and d{sub x{sup 2}{minus}y{sup 2}} superconducting-gap symmetry is in CuO{sub 2} planes of YBCO. But, the (001) of YBCO has no phase difference of {pi} in spite of the existence of d-wave symmetry in YBCO. {copyright} {ital 1997} {ital The American Physical Society}

  20. Performance and modeling of superconducting ring resonators at millimeter-wave frequencies

    NASA Technical Reports Server (NTRS)

    Bhasin, K. B.; Chorey, C. M.; Warner, J. D.; Romanofsky, R. R.; Heinen, V. O.; Kong, K. S.; Lee, H. Y.; Itoh, T.

    1990-01-01

    Microstrip ring resonators operating at 35 GHz were fabricated from laser ablated YBCO thin films deposited on lanthanum aluminate substrates. They were measured over a range of temperatures and their performance compared to identical resonators made of evaporated gold. Below 60 Kelvin the superconducting strip performed better than the gold, reaching an unloaded Q approximately 1.5 times that of gold at 25 K. A shift in the resonant frequency follows the form predicted by the London equations. The Phenomenological Loss Equivalence Method is applied to the ring resonator and the theoretically calculated Q values are compared to the experimental results.

  1. Inverse polarity of the resistive switching effect and strong inhomogeneity in nanoscale YBCO-metal contacts

    NASA Astrophysics Data System (ADS)

    Truchly, M.; Plecenik, T.; Zhitlukhina, E.; Belogolovskii, M.; Dvoranova, M.; Kus, P.; Plecenik, A.

    2016-11-01

    We have studied a bipolar resistive switching phenomenon in c-axis oriented normal-state YBa2Cu3O7-c (YBCO) thin films at room temperature by scanning spreading resistance microscopy (SSRM) and scanning tunneling microscopy (STM) techniques. The most striking experimental finding has been the opposite (in contrast to the previous room and low-temperature data for planar metal counter-electrode-YBCO bilayers) voltage-bias polarity of the switching effect in all SSRM and a number of STM measurements. We have assumed that the hysteretic phenomena in current-voltage characteristics of YBCO-based contacts can be explained by migration of oxygen-vacancy defects and, as a result, by the formation or dissolution of more or less conductive regions near the metal-YBCO interface. To support our interpretation of the macroscopic resistive switching phenomenon, a minimalist model that describes radical modifications of the oxygen-vacancy effective charge in terms of a charge-wind effect was proposed. It was shown theoretically that due to the momentum exchange between current carriers (holes in the YBCO compound) and activated oxygen ions, the direction in which oxygen vacancies are moving is defined by the balance between the direct electrostatic force on them and that caused by the current-carrier flow.

  2. Unique nanostructural features in Fe, Mn-doped YBCO thin films

    NASA Astrophysics Data System (ADS)

    Meledin, A.; Turner, S.; Cayado, P.; Mundet, B.; Solano, E.; Ricart, S.; Ros, J.; Puig, T.; Obradors, X.; Van Tendeloo, G.

    2016-12-01

    An attempt to grow a thin epitaxial composite film of YBa2Cu3O7-δ (YBCO) with spinel MnFe2O4 (MFO) nanoparticles on a LAO substrate using the CSD approach resulted in a decomposition of the spinel and various doping modes of YBCO with the Fe and Mn cations. These nanostructural effects lead to a lowering of T c and a slight J c increase in field. Using a combination of advanced transmission electron microscopy (TEM) techniques such as atomic resolution high-angle annular dark field scanning TEM, energy dispersive x-ray spectroscopy and electron energy-loss spectroscopy we have been able to decipher and characterize the effects of the Fe and Mn doping on the film architecture. The YBaCuFeO5 anion-deficient double perovskite phase was detected in the form of 3D inclusions as well as epitaxially grown lamellas within the YBCO matrix. These nano-inclusions play a positive role as pinning centers responsible for the J c/J sf (H) dependency smoothening at high magnetic fields in the YBCO-MFO films with respect to the pristine YBCO films.

  3. High field superconducting magnets

    NASA Technical Reports Server (NTRS)

    Hait, Thomas P. (Inventor); Shirron, Peter J. (Inventor)

    2011-01-01

    A superconducting magnet includes an insulating layer disposed about the surface of a mandrel; a superconducting wire wound in adjacent turns about the mandrel to form the superconducting magnet, wherein the superconducting wire is in thermal communication with the mandrel, and the superconducting magnet has a field-to-current ratio equal to or greater than 1.1 Tesla per Ampere; a thermally conductive potting material configured to fill interstices between the adjacent turns, wherein the thermally conductive potting material and the superconducting wire provide a path for dissipation of heat; and a voltage limiting device disposed across each end of the superconducting wire, wherein the voltage limiting device is configured to prevent a voltage excursion across the superconducting wire during quench of the superconducting magnet.

  4. AC Loss Measurements on a 2G YBCO Coil

    SciTech Connect

    Rey, Christopher M; Duckworth, Robert C; Schwenterly, S W

    2011-01-01

    The Oak Ridge National Laboratory (ORNL) is collaborating with Waukesha Electric Systems (WES) to continue development of HTS power transformers. For compatibility with the existing power grid, a commercially viable HTS transformer will have to operate at high voltages in the range of 138 kV and above, and will have to withstand 550-kV impulse voltages as well. Second-generation (2G) YBCO coated conductors will be required for an economically-competitive design. In order to adequately size the refrigeration system for these transformers, the ac loss of these HTS coils must be characterized. Electrical AC loss measurements were conducted on a prototype high voltage (HV) coil with co-wound stainless steel at 60 Hz in a liquid nitrogen bath using a lock-in amplifier technique. The prototype HV coil consisted of 26 continuous (without splice) single pancake coils concentrically centered on a stainless steel former. For ac loss measurement purposes, voltage tap pairs were soldered across each set of two single pancake coils so that a total of 13 separate voltage measurements could be made across the entire length of the coil. AC loss measurements were taken as a function of ac excitation current. Results show that the loss is primarily concentrated at the ends of the coil where the operating fraction of critical current is the highest and show a distinct difference in current scaling of the losses between low current and high current regimes.

  5. Phase dynamics of low critical current density YBCO Josephson junctions

    NASA Astrophysics Data System (ADS)

    Massarotti, D.; Stornaiuolo, D.; Rotoli, G.; Carillo, F.; Galletti, L.; Longobardi, L.; Beltram, F.; Tafuri, F.

    2014-08-01

    High critical temperature superconductors (HTS) based devices can have impact in the study of the phase dynamics of Josephson junctions (JJs) thanks to the wide range of junction parameters they offer and to their unconventional properties. Measurements of current-voltage characteristics and of switching current distributions constitute a direct way to classify different regimes of the phase dynamics and of the transport, also in nontrivial case of the moderately damped regime (MDR). MDR is going to be more and more common in JJs with advances in nanopatterning superconductors and synthesizing novel hybrid systems. Distinctive signatures of macroscopic quantum tunneling and of thermal activation in presence of different tunable levels of dissipation have been detected in YBCO grain boundary JJs. Experimental data are supported by Monte Carlo simulations of the phase dynamics, in a wide range of temperatures and dissipation levels. This allows us to quantify dissipation in the MDR and partially reconstruct a phase diagram as guideline for a wide range of moderately damped systems.

  6. Far-infrared Hall Effect in YBCO films

    NASA Astrophysics Data System (ADS)

    Grayson, M.; Rigal, L.; Cerne, J.; Schmadel, D. C.; Drew, H. D.; Kung, P.-J.

    2001-03-01

    In order to gain insight into the so-called "anomalous Hall effect" in Hi Tc superconductors(T.R. Chien, D.A. Brawner, Z.Z. Wang, and N.P. Ong, PRB 43, 6242(1991).) we explore Hall measurements at far-infrared (FIR) frequencies and study the temperature dependence. We separately measure the real and imaginary parts of the magneto-optical response of YBCO thin films to polarized FIR light (15-250 cm-1). The induced rotation of linearly polarized light tells us the real part of the Faraday angle, Re[θ_F(ω)], and the induced dichroism of circularly polarized light tells us Im[θ_F(ω)]. We can then deduce the complex Hall angle without resorting to Kramers-Kronig (K-K) analysis. Since both the Hall angle and the Faraday angle obey sum rules, we can compare to higher frequencies(Cerne, et al., invited talk) and determine additional information about the spectral response at intermediate frequencies. The consistency of these results is verified with K-K analysis.

  7. Degradation of the performance of a YBCO-coated conductor double pancake coil due to epoxy impregnation

    NASA Astrophysics Data System (ADS)

    Takematsu, T.; Hu, R.; Takao, T.; Yanagisawa, Y.; Nakagome, H.; Uglietti, D.; Kiyoshi, T.; Takahashi, M.; Maeda, H.

    2010-09-01

    Now that YBCO-coated conductors have been commercialized, a number of YBCO coils have been developed. However, their basic performances have not been systematically investigated so far. Here, we demonstrate that of a YBCO double pancake coil. The critical current of an epoxy impregnated YBCO double pancake coil was substantially degraded, i.e. the normal voltage appears above 8 A, only 18% of that for the dry coil. It was inferred that degradation occurs if the cumulative radial stress developed during cool down exceeds the critical transverse stress for the YBCO-coated conductor (typically 10 MPa). Under these conditions, the conductor was debonded at the interface between the buffer layer and YBCO layers, or fractured in the YBCO layer itself, causing cracks on the YBCO layer, resulting in a significant decline of the critical current. These negative effects are suppressed if the coils are dry wound or impregnated with paraffin, as the bonding strengths between turns are negligible and therefore turns are separated if the cumulative radial stress tends to be tensile. For non-circular coils in which epoxy impregnation is inevitable, degradation due to cumulative tensile transverse stress is still the major problem.

  8. Angular dependence of direct current decay in a closed YBCO double-pancake coil under external AC magnetic field and reduction by magnetic shielding

    NASA Astrophysics Data System (ADS)

    Geng, J.; Zhang, H.; Li, C.; Zhang, X.; Shen, B.; Coombs, T. A.

    2017-03-01

    High T c superconducting (HTS) coils are ideal candidates in the use of high field magnets. HTS coils carrying a direct current, however, suffer a non-negligible loss when they are exposed to an external AC magnetic field. Although this phenomenon is well known, no study concerning AC magnetic field angular dependence of direct current decay has ever been shown. In this work, we experimentally investigate the direct current decay characteristics in a closed double pancake coil made of a YBCO coated conductor under external AC field. AC field of different angles with respect to the coil plane is applied. Results show that the current decay rate presents a strong angular dependence. The fastest decay occurs when the field is parallel to the coil plane, in which case the surface of the tape in the outermost layer experiences most flux variation. To reduce the decay rate, we propose wrapping superconducting tapes around the outermost layer of the coil to shield external AC field. This method significantly reduces direct current decay rate under parallel field, without affecting the perpendicular self-field of the coil.

  9. Anisotropic superconductivity in graphite intercalation compound YbC 6

    NASA Astrophysics Data System (ADS)

    Kawai, N. F.; Fukuyama, Hiroshi

    2008-12-01

    We report anisotropy of the upper critical field (Bc2) of an intercalated graphite superconductor YbC6 (Tc = 6.5 K) determined from angular dependent magnetoresistance measurements. Though the perpendicular coherence length is much longer than interlayer spacing, measured angular dependences of Bc2 are well fitted by the Lawrence-Doniach model or the Tinkham model, which are known to be applicable to quasi two-dimensional materials or thin films, rather than the effective mass model. This observation is similar to the measurements for the other intercalated graphite superconductor, CaC6, by Jobiliong et al. [E. Jobiliong, H.D. Zhou, J.A. Janik, Y.-J. Jo, L. Balicas, J.S. Brooks, C.R. Wiebe, Phys. Rev. B 76 (2007) 052511]. A possible explanation for the unexpected applicability of these models is that our YbC6 samples are synthesized as thin flakes in the host graphite.

  10. Conceptual design of 275 kV class high-Tc superconducting cable

    NASA Astrophysics Data System (ADS)

    Mukoyama, S.; Yagi, M.; Fujiwara, N.; Ichikawa, H.

    2010-11-01

    High-temperature superconducting (HTS) cables are expected to be next generation transmission line because of the compact, lightweight, large capacity, and low loss features. Especially, since the YBa2Cu3Ox (YBCO) tape has a high critical current, high magnetic-field property, low AC loss, and low cost, using YBCO tapes for a HTS cable seems to be one of the most promising ways to make the HTS cable attractive. Therefore, YBCO HTS cables have been studied extensively in Japan, the United States, Korea, and many other countries. We now believe that 275 kV class HTS cables will be used for future large capacity lines based on the needs of Japanese transmission networks for bulk transmission power in overhead transmission lines or gas insulated transmission lines (GIL). We started to develop the 275 kV class HTS cable for the new energy and industrial technology development organization (NEDO) project at 2008, and we have studied the applicability and the environmental and economic advantages of the 275 kV cable. This paper will introduce advantages and a conceptual design of the 275 kV HTS cable.

  11. Fractures in anisotropic media

    NASA Astrophysics Data System (ADS)

    Shao, Siyi

    Rocks may be composed of layers and contain fracture sets that cause the hydraulic, mechanical and seismic properties of a rock to be anisotropic. Coexisting fractures and layers in rock give rise to competing mechanisms of anisotropy. For example: (1) at low fracture stiffness, apparent shear-wave anisotropy induced by matrix layering can be masked or enhanced by the presence of a fracture, depending on the fracture orientation with respect to layering, and (2) compressional-wave guided modes generated by parallel fractures can also mask the presence of matrix layerings for particular fracture orientations and fracture specific stiffness. This report focuses on two anisotropic sources that are widely encountered in rock engineering: fractures (mechanical discontinuity) and matrix layering (impedance discontinuity), by investigating: (1) matrix property characterization, i.e., to determine elastic constants in anisotropic solids, (2) interface wave behavior in single-fractured anisotropic media, (3) compressional wave guided modes in parallel-fractured anisotropic media (single fracture orientation) and (4) the elastic response of orthogonal fracture networks. Elastic constants of a medium are required to understand and quantify wave propagation in anisotropic media but are affected by fractures and matrix properties. Experimental observations and analytical analysis demonstrate that behaviors of both fracture interface waves and compressional-wave guided modes for fractures in anisotropic media, are affected by fracture specific stiffness (controlled by external stresses), signal frequency and relative orientation between layerings in the matrix and fractures. A fractured layered medium exhibits: (1) fracture-dominated anisotropy when the fractures are weakly coupled; (2) isotropic behavior when fractures delay waves that are usually fast in a layered medium; and (3) matrix-dominated anisotropy when the fractures are closed and no longer delay the signal. The

  12. Parallel Anisotropic Tetrahedral Adaptation

    NASA Technical Reports Server (NTRS)

    Park, Michael A.; Darmofal, David L.

    2008-01-01

    An adaptive method that robustly produces high aspect ratio tetrahedra to a general 3D metric specification without introducing hybrid semi-structured regions is presented. The elemental operators and higher-level logic is described with their respective domain-decomposed parallelizations. An anisotropic tetrahedral grid adaptation scheme is demonstrated for 1000-1 stretching for a simple cube geometry. This form of adaptation is applicable to more complex domain boundaries via a cut-cell approach as demonstrated by a parallel 3D supersonic simulation of a complex fighter aircraft. To avoid the assumptions and approximations required to form a metric to specify adaptation, an approach is introduced that directly evaluates interpolation error. The grid is adapted to reduce and equidistribute this interpolation error calculation without the use of an intervening anisotropic metric. Direct interpolation error adaptation is illustrated for 1D and 3D domains.

  13. Evolution of superconducting gap and metallic ground state in cuprates from transport

    NASA Astrophysics Data System (ADS)

    Taillefer, Louis

    2006-03-01

    We report on fundamental characteristics of the ground state of cuprates in the limit of T=0, for both normal and superconducting states, obtained from transport measurements on high-quality single crystals of YBCO and Tl-2201, as a function of hole concentration. The superconducting gap is extracted from thermal conductivity; it is found to scale with the superconducting transition temperature throughout the overdoped regime, with a gap-to-Tc ratio of 5 [1]. The normal state is accessed by suppressing superconductivity with magnetic fields up to 60 T and is characterized by the limiting behavior of its electrical resistivity; while carrier localization is observed in YBCO at low temperature for carrier concentrations p below 0.1 hole/planar Cu, at p=0.1 and above the material remains highly metallic down to T=0 [2]. This shows that the non-superconducting state of underdoped cuprates, deep in the pseudogap phase, is remarkably similar to that of strongly overdoped cuprates, e.g. at p=0.3. We compare these results with similar measurements on other cuprates and discuss their implication for our understanding of the cuprate phase diagram. [1] In collaboration with: D.G. Hawthorn, S.Y. Li, M. Sutherland, E. Boaknin, R.W. Hill, C. Proust, F. Ronning, M. Tanatar, J. Paglione, D. Peets, R. Liang, D.A. Bonn, W.N. Hardy, and N.N. Kolesnikov. [2] In collaboration with: C. Proust, M. Sutherland, N. Doiron- Leyraud, S.Y. Li, R. Liang, D.A. Bonn, W.N. Hardy, N.E. Hussey, S. Adachi, S. Tajima, J. Levallois, and M. Narbone.

  14. Anisotropic Total Variation Filtering

    SciTech Connect

    Grasmair, Markus; Lenzen, Frank

    2010-12-15

    Total variation regularization and anisotropic filtering have been established as standard methods for image denoising because of their ability to detect and keep prominent edges in the data. Both methods, however, introduce artifacts: In the case of anisotropic filtering, the preservation of edges comes at the cost of the creation of additional structures out of noise; total variation regularization, on the other hand, suffers from the stair-casing effect, which leads to gradual contrast changes in homogeneous objects, especially near curved edges and corners. In order to circumvent these drawbacks, we propose to combine the two regularization techniques. To that end we replace the isotropic TV semi-norm by an anisotropic term that mirrors the directional structure of either the noisy original data or the smoothed image. We provide a detailed existence theory for our regularization method by using the concept of relaxation. The numerical examples concluding the paper show that the proposed introduction of an anisotropy to TV regularization indeed leads to improved denoising: the stair-casing effect is reduced while at the same time the creation of artifacts is suppressed.

  15. Structural and electrical properties of epitaxial YBCO films on Si (Abstract Only).

    NASA Astrophysics Data System (ADS)

    Fork, David K.; Barrera, A.; Phillips, Julia M.; Newman, N.; Fenner, David B.; Geballe, Theodore H.; Connell, G. A. N.; Boyce, James B.

    1991-03-01

    Efforts to grow high quality films of YBCO on Si have been complicated by factors discussed in Ref. 1, chief among them being the reaction between YBCO and Si, which is damaging even at 550 C. This is well below the customary temperatures for YBCO film growth. To avoid the reaction problem, epitaxial YBCO films were grown on Si (100) using an intermediate buffer layer of yttria-stabilized zirconia (YSZ).2 Both layers are grown via an entirely in situ process by pulsed laser deposition (PLD). Although the buffer layer prevents reaction, another problem arises; the large difference in thermal expansion coefficients between silicon and YBCO causes strain at room temperature. Thin (<500 A) YBCO films are unrelaxed and under tensile strain with a distorted unit cell. Thicker films are cracked and have poorer electrical properties. The thermal strain may be reduced by growing on silicon-on-sapphire (SOS) rather than silicon.3 This allows the growth of films of arbitrary thickness. Ion channeling reveals a high degree of crystalline perfection with a channeling minimum yield for Ba as low as 12% on either silicon or SOS. The normal state resistivity is 250-300 i-cm at 300 K; the critical temperature, Tc (R=0), is 86-88 K with a transition width (ATc) of I K. Critical current densities (J)°f 2x107 A/cm2 at 4.2 K and >2x106 A/cm2 at 77 K have been achieved. In addition, the surface resistance of a YBCO film on SOS was measured against Nb at 4.2 K. At 10 GHz, a value of 45 was obtained. This compares favorably to values reported for LaAlO3. Application of this technology to produce reaction patterned microstrip lines has been tested.4 This was done by ion milling away portions of the YSZ buffer layer prior to the YBCO deposition. YBCO landing on regions of exposed Si reacts to form an insulator. This technique was used to make 3 micron lines 1.5 mm long. The resulting structure had a Jc of l.6xl06 A/cm2 at 77 K. Isolation of separate structures exceeded 20 M. Several

  16. Role of twin boundaries on vortex pinning of CSD YBCO nanocomposites

    NASA Astrophysics Data System (ADS)

    Rouco, V.; Palau, A.; Guzman, R.; Gazquez, J.; Coll, M.; Obradors, X.; Puig, T.

    2014-12-01

    We study the effect of twin boundaries (TBs) on the critical current density of YBa2Cu3O7-x (YBCO) films and nanocomposites grown on different substrates. Varying both the direction of the current and magnetic field, we show that the TB orientation is a crucial parameter to consider in the optimization of Jc for particular applications. A quantitative and detailed analysis of the role of TBs on vortex dynamics has allowed us to infer that extended TB planes in pristine YBCO films can reduce Jc by 60% at low temperatures due to vortex channeling effects or increase it by a 98% at high temperatures due to directional vortex pinning. Moreover, we demonstrate that TB length and distribution can be strongly modified in YBCO nanocomposites. We observe that TB planes with no vertical coherence are still effective for vortex pinning while are not to create channels for easy vortex flow.

  17. Optimized configurations of autostable superconducting magnetic bearings for practical applications

    SciTech Connect

    Schoechlin, A.; Ritter, T.; Bornemann, H.J.

    1995-11-01

    In order to establish an optimized bearing design for a flywheel for energy storage, the authors have studied model bearing configurations involving bulk YBCO pellets and double-dipole magnet configurations. They were interested to see what is the correlation between the maximum attainable levitation force, measured for a typical bearing gap of 3 mm, and the separation between the magnetic poles. Equal polarity (north-north) and alternate polarity (north-south) configurations were investigated. The maximum levitation force was obtained with the alternate polarity arrangement for a separation between the magnetic poles of 6 mm. It represents an increase of 19% compared to a non-optimized configuration. The experiments demonstrate that configurations of superconducting magnetic bearings can be optimized to obtain better levitation properties.

  18. Magnetic Imaging of Superconducting Tapes to Determine Current Flow

    NASA Astrophysics Data System (ADS)

    Mueller, Fred M.; Brown, David J.; Hawley, Marilyn E.; Brown, Geoffrey W.; Yates Coulter, J.

    2000-03-01

    We have developed a magnetic imaging system which yields quantitative information about the magnetic field near the surface of a superconducting tape while it is carrying current at liquid nitrogen temperatures. The imaging system is based on a mechanical scanner with motion coupled into a dewar and uses standard magnetoresistive read heads from computer hard disk drives as the sensor elements. We have numerically inverted the external magnetic field data from silver-coated YBCO tapes to derive the internal tape current densities. Preliminary results are consistent with the expected patterns in the tapes, obey sum rules, and exhibit time reversal symmetry. Preliminary current flow paths suggest that the current density can be non-uniform.

  19. 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

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

    NASA Astrophysics Data System (ADS)

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

    1992-05-01

    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

  1. Practical adaptation in bulk superconducting magnetic bearing applications

    NASA Astrophysics Data System (ADS)

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

    1992-04-01

    Lifting capacities greater than 41 N/sq cm (60 psi) at 77 K have been achieved using a combination of permanent magnets and high quality melt-textured YBa2Cu3O(7-delta) (YBCO). The key concept of this hybrid superconducting magnetic bearing (HSMB) is the use of strong magnetic repulsion and attraction from permanent magnets to support high loads in conjunction with flux pinning in a type II superconductor to counteract 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 and journal bearing configurations on a bearing prototype.

  2. Superconducting magnet

    DOEpatents

    Satti, John A.

    1980-01-01

    A superconducting magnet designed to produce magnetic flux densities of the order of 4 to 5 Webers per square meter is constructed by first forming a cable of a plurality of matrixed superconductor wires with each wire of the plurality insulated from each other one. The cable is shaped into a rectangular cross-section and is wound with tape in an open spiral to create cooling channels. Coils are wound in a calculated pattern in saddle shapes to produce desired fields, such as dipoles, quadrupoles, and the like. Wedges are inserted between adjacent cables as needed to maintain substantially radial placement of the long dimensions of cross sections of the cables. After winding, individual strands in each of the cables are brought out to terminals and are interconnected to place all of the strands in series and to maximize the propagation of a quench by alternating conduction from an inner layer to an outer layer and from top half to bottom half as often as possible. Individual layers are separated from others by spiraled aluminum spacers to facilitate cooling. The wound coil is wrapped with an epoxy tape that is cured by heat and then machined to an interference fit with an outer aluminum pipe which is then affixed securely to the assembled coil by heating it to make a shrink fit. In an alternate embodiment, one wire of the cable is made of copper or the like to be heated externally to propagate a quench.

  3. Cube-textured substrates for YBCO-coated conductors: microstructure evolution and stability

    NASA Astrophysics Data System (ADS)

    Vannozzi, A.; Rufoloni, A.; Celentano, G.; Augieri, A.; Ciontea, L.; Fabbri, F.; Galluzzi, V.; Gambardella, U.; Mancini, A.; Petrisor, T.

    2006-12-01

    The realization of YBCO-based coated conductors with high critical current density involves the deposition of highly biaxially textured YBCO films. The use of epitaxial growth shifts this requirement to the template used for YBCO deposition. In the rolling-assisted biaxially textured substrate (RABiTS) approach, an appropriately oriented template is provided by a cube-textured substrate. The development of a cube texture is the result of recrystallization occurring in a heavily deformed tape, which is activated by high-temperature annealing. In the case of Ni-based alloys, thermal treatment at temperatures ranging from 900 to 1150 °C for at least 30 min is commonly used. The determination of the minimum conditions for thermal treatments in terms of temperature-time involved in the recrystallization process is therefore of practical interest. In this work, Ni-5 at.% W alloy has been studied as a substrate for YBCO-coated conductors. 100 µm thick tapes have been obtained through heavy cold rolling, followed by annealing in high vacuum. Different thermal treatments with rates of 20 °C min-1 have been performed in order to study the formation and the evolution of the cube texture. Moreover, the annealing time has been varied in order to inspect the thermal stability of the substrate microstructure at the relatively high deposition temperature of YBCO films. It is found that the substrate begins recrystallizing at 700 °C and that the cube texture is fully developed at temperatures higher than 800 °C, while annealing at 900 °C for 1 h produces a stable microstructure at the typical YBCO deposition conditions.

  4. Interlayer structure in YBCO-coated conductors prepared by chemical solution deposition

    NASA Astrophysics Data System (ADS)

    Molina-Luna, Leopoldo; Egoavil, Ricardo; Turner, Stuart; Thersleff, Thomas; Verbeeck, Jo; Holzapfel, Bernhard; Eibl, Oliver; Van Tendeloo, Gustaaf

    2013-07-01

    The functionality of YBa2Cu3O7-δ (YBCO)-coated conductor technology depends on the reliability and microstructural properties of a given tape or wire architecture. Particularly, the interface to the metal tape is of interest since it determines the adhesion, mechanical stability of the film and thermal contact of the film to the substrate. A trifluoroacetate (TFA)—metal organic deposition (MOD) prepared YBCO film deposited on a chemical solution-derived buffer layer architecture based on CeO2/La2Zr2O7 and grown on a flexible Ni5 at.%W substrate with a {100}<001> biaxial texture was investigated. The YBCO film had a thickness was 440 nm and a jc of 1.02 MA cm-2 was determined at 77 K and zero external field. We present a sub-nanoscale analysis of a fully processed solution-derived YBCO-coated conductor by aberration-corrected scanning transmission electron microscopy (STEM) combined with electron energy-loss spectroscopy (EELS). For the first time, structural and chemical analysis of the valence has been carried out on the sub-nm scale. Intermixing of Ni, La, Ce, O and Ba takes place at these interfaces and gives rise to nanometer-sized interlayers which are a by-product of the sequential annealing process. Two distinct interfacial regions were analyzed in detail: (i) the YBCO/CeO2/La2Zr2O7 region (10 nm interlayer) and (ii) the La2Zr2O7/Ni-5 at.%W substrate interface region (20 nm NiO). This is of particular significance for the functionality of these YBCO-coated conductor architectures grown by chemical solution deposition.

  5. Surface superconductivity in lead

    SciTech Connect

    Khlyustikov, I. N.

    2016-02-15

    A transition to the surface superconducting state is detected in lead single crystals at a temperature approximately 0.25 mK higher than the bulk superconducting transition temperature. The (H, T) phase diagram of this state is analyzed.

  6. YBCO thin film evaporation on as-deposited silver film on MgO

    NASA Astrophysics Data System (ADS)

    Azoulay, J.

    1999-11-01

    YBa 2Cu 3O 7- δ (YBCO) thin film was evaporated on as-deposited Ag buffer layer on MgO substrate. A simple, inexpensive vacuum system equipped with one resistively heated source was used. The subsequent heat treatment was carried out under low oxygen partial pressure at a relatively low temperature and short dwelling time. The films thus obtained were characterized for electrical properties using DC four-probe electrical measurements and inspected for structural properties and chemical composition by scanning electron microscopy (SEM). It is shown that YBCO thin film can grow on as-deposited thin silver layer on MgO substrate.

  7. Morphology and etching studies on YBCO and CuO single crystals

    NASA Astrophysics Data System (ADS)

    Prabhakaran, D.; Subramanian, C.; Balakumar, S.; Ramasamy, P.

    1999-06-01

    Single crystals of YBCO (Y123) and CuO have been grown from a BaO-CuO (28:72) flux using a low axial gradient furnace (∼1°C/cm). Growth morphology of the grown crystals was studied using an optical microscope, scanning electron microscopy and atomic force microscopy. Cell parameter values and chemical composition of the grown crystals were determined from the X-ray diffraction data and inductively coupled plasma analysis, respectively. Etching studies were done for both the crystals using different etchants. Oxygen stoichiometry of the YBCO crystal was determined by iodometry titration analysis.

  8. Thermal expansion of several materials for superconducting magnets

    SciTech Connect

    Clark, A.F.; Fujii, G.; Ranney, M.A.

    1981-09-01

    The thermal expansion of several materials used in the consruction of high field superconducting magnets has been measured from 4 K to room temperature. The materials were a NbTi and two A15 multifilamentary conductors and several nonmetallic composites made from linen/phenolic, fiberglass/epoxy and superconducitng wire/epoxy. The conductor expansions are typical of metals and the composite expansions are highy anisotropic. Both graphic and tabular values are provided by a computer fitting of the experimental data. The importnce of thermal expansion differences in critical current measurement apparatus and superconducting magnet design are discussed. 12 refs.

  9. Phase competition in trisected superconducting dome.

    PubMed

    Vishik, I M; Hashimoto, M; He, Rui-Hua; Lee, Wei-Sheng; Schmitt, Felix; Lu, Donghui; Moore, R G; Zhang, C; Meevasana, W; Sasagawa, T; Uchida, S; Fujita, Kazuhiro; Ishida, S; Ishikado, M; Yoshida, Yoshiyuki; Eisaki, Hiroshi; Hussain, Zahid; Devereaux, Thomas P; Shen, Zhi-Xun

    2012-11-06

    A detailed phenomenology of low energy excitations is a crucial starting point for microscopic understanding of complex materials, such as the cuprate high-temperature superconductors. Because of its unique momentum-space discrimination, angle-resolved photoemission spectroscopy (ARPES) is ideally suited for this task in the cuprates, where emergent phases, particularly superconductivity and the pseudogap, have anisotropic gap structure in momentum space. We present a comprehensive doping- and temperature-dependence ARPES study of spectral gaps in Bi(2)Sr(2)CaCu(2)O(8+δ), covering much of the superconducting portion of the phase diagram. In the ground state, abrupt changes in near-nodal gap phenomenology give spectroscopic evidence for two potential quantum critical points, p = 0.19 for the pseudogap phase and p = 0.076 for another competing phase. Temperature dependence reveals that the pseudogap is not static below T(c) and exists p > 0.19 at higher temperatures. Our data imply a revised phase diagram that reconciles conflicting reports about the endpoint of the pseudogap in the literature, incorporates phase competition between the superconducting gap and pseudogap, and highlights distinct physics at the edge of the superconducting dome.

  10. Phase competition in trisected superconducting dome

    PubMed Central

    Vishik, I. M.; Hashimoto, M.; He, Rui-Hua; Lee, Wei-Sheng; Schmitt, Felix; Lu, Donghui; Moore, R. G.; Zhang, C.; Meevasana, W.; Sasagawa, T.; Uchida, S.; Fujita, Kazuhiro; Ishida, S.; Ishikado, M.; Yoshida, Yoshiyuki; Eisaki, Hiroshi; Hussain, Zahid; Devereaux, Thomas P.; Shen, Zhi-Xun

    2012-01-01

    A detailed phenomenology of low energy excitations is a crucial starting point for microscopic understanding of complex materials, such as the cuprate high-temperature superconductors. Because of its unique momentum-space discrimination, angle-resolved photoemission spectroscopy (ARPES) is ideally suited for this task in the cuprates, where emergent phases, particularly superconductivity and the pseudogap, have anisotropic gap structure in momentum space. We present a comprehensive doping- and temperature-dependence ARPES study of spectral gaps in Bi2Sr2CaCu2O8+δ, covering much of the superconducting portion of the phase diagram. In the ground state, abrupt changes in near-nodal gap phenomenology give spectroscopic evidence for two potential quantum critical points, p = 0.19 for the pseudogap phase and p = 0.076 for another competing phase. Temperature dependence reveals that the pseudogap is not static below Tc and exists p > 0.19 at higher temperatures. Our data imply a revised phase diagram that reconciles conflicting reports about the endpoint of the pseudogap in the literature, incorporates phase competition between the superconducting gap and pseudogap, and highlights distinct physics at the edge of the superconducting dome. PMID:23093670

  11. Superconducting vortex pinning with artificial magnetic nanostructures.

    SciTech Connect

    Velez, M.; Martin, J. I.; Villegas, J. E.; Hoffmann, A.; Gonzalez, E. M.; Vicent, J. L.; Schuller, I. K.; Univ. de Oviedo-CINN; Unite Mixte de Physique CNRS Univ. Paris-Sud; Univ.Complutense de Madrid; Univ. California at San Diego

    2008-11-01

    This review is dedicated to summarizing the recent research on vortex dynamics and pinning effects in superconducting films with artificial magnetic structures. The fabrication of hybrid superconducting/magnetic systems is presented together with the wide variety of properties that arise from the interaction between the superconducting vortex lattice and the artificial magnetic nanostructures. Specifically, we review the role that the most important parameters in the vortex dynamics of films with regular array of dots play. In particular, we discuss the phenomena that appear when the symmetry of a regular dot array is distorted from regularity towards complete disorder including rectangular, asymmetric, and aperiodic arrays. The interesting phenomena that appear include vortex-lattice reconfigurations, anisotropic dynamics, channeling, and guided motion as well as ratchet effects. The different regimes are summarized in a phase diagram indicating the transitions that take place as the characteristic distances of the array are modified respect to the superconducting coherence length. Future directions are sketched out indicating the vast open area of research in this field.

  12. Design and fabrication of layer-wound YBCO solenoids

    NASA Astrophysics Data System (ADS)

    Uglietti, D.; Choi, S.; Kiyoshi, T.

    2010-11-01

    Rare Earth based coated conductors are very promising conductors for the construction of high field solenoids. Development of coil winding technique was started at the Tsukuba Magnet Laboratory: coils of various sizes (from 18 mm to 220 mm of an inner diameter) have been fabricated by layer-winding without impregnation in order to test the mechanical and superconducting properties. In the thin 220 mm diameter coil the Hoop stress reached over 500 MPa at 130 A in 14 T background field, without degradation of the superconducting properties. In the small diameter coils (18 mm of inner diameter) the tape was insulated using enamel to minimize the cross section and to enhance the coil current density. The highest field generated was 2.1 T in a background field of 18 T (total field was 20.1 T) at 4.2 K and the coil current density was 240 A/mm2.

  13. Evidence for a minigap in YBCO grain boundary Josephson junctions.

    PubMed

    Lucignano, P; Stornaiuolo, D; Tafuri, F; Altshuler, B L; Tagliacozzo, A

    2010-10-01

    Self-assembled YBaCuO diffusive grain boundary submicron Josephson junctions offer a realization of a special regime of the proximity effect, where normal state coherence prevails on the superconducting coherence in the barrier region. Resistance oscillations from the current-voltage characteristic encode mesoscopic information on the junction and more specifically on the minigap induced in the barrier. Their persistence at large voltages is evidence of the long lifetime of the antinodal (high energy) quasiparticles.

  14. Design and comparative analysis of 10 MW class superconducting wind power generators according to different types of superconducting wires

    NASA Astrophysics Data System (ADS)

    Sung, Hae-Jin; Kim, Gyeong-Hun; Kim, Kwangmin; Park, Minwon; Yu, In-Keun; Kim, Jong-Yul

    2013-11-01

    Wind turbine concepts can be classified into the geared type and the gearless type. The gearless type wind turbine is more attractive due to advantages of simplified drive train and increased energy yield, and higher reliability because the gearbox is omitted. In addition, this type resolves the weight issue of the wind turbine with the light weight of gearbox. However, because of the low speed operation, this type has disadvantage such as the large diameter and heavy weight of generator. Super-Conducting (SC) wind power generator can reduce the weight and volume of a wind power system. Properties of superconducting wire are very different from each company. This paper considers the design and comparative analysis of 10 MW class SC wind power generators according to different types of SC wires. Super-Conducting Synchronous Generators (SCSGs) using YBCO and Bi-2223 wires are optimized by an optimal method. The magnetic characteristics of the SCSGs are investigated using the finite elements method program. The optimized specifications of the SCSGs are discussed in detail, and the optimization processes can be used effectively to develop large scale wind power generation systems.

  15. Gamma radiation effects on some properties of YBCO

    NASA Astrophysics Data System (ADS)

    Luo, L.; Zhang, Y. H.; Hu, S. H.; Liu, W. H.; Zhang, G. L.; Hu, W. X.

    1991-07-01

    Radiation effects of polycrystalline YBCO bulk sample irradiated by 60Co γ-rays, dose of 1×10 6 up to 7.5×10 8 rad, at room temperature on critical temperature and critical current were investigated. IR spectrum was also used to study the mechanism of the irradiation. A considerably strong dependence of these parameters upon the irradiation dose was observed. No significant effects on the critical temperature were found, but the critical current in zero magnetic field changed greatly. It shows a tendency to decrease with the increase of the irradiation dose except for a slight increase with the dose less than about 2×10 7 rad and no simple relations between critical currents and irradiation doses was found. A typical case is that the critical current is reduced to about 60% when the dose reaches 5×10 9 rad, but the dependence of critical currents on the magnetic field shows that the critical currents are higher than those of the unirradiated one in the range of magnetic field higher than 100 G and decrease more slowly in a magnetic field compared with the unirradiated one. The results indicate that the defects produced by γ-ray irradiation are beneficial to flux pinning in higher fields. IR spectra analysis reveals that the intensity of the peak responsible for the Cu(1)- O(1) chain vibration is decreased, indicating that the bond of the Cu(1)-O(1) may be partly broken through collision process of the Compton electron produced by the γ-ray. This effect probably gives rise to a decrease of the critical currents.

  16. Superconductivity and physical properties of CaPd2Ge2 single crystals.

    PubMed

    Anand, V K; Kim, H; Tanatar, M A; Prozorov, R; Johnston, D C

    2014-10-08

    We present the superconducting and normal state properties of CaPd(2)Ge(2) single crystals investigated by magnetic susceptibility χ, isothermal magnetization M, heat capacity Cp, in-plane electrical resistivity ρ and London penetration depth λ versus temperature T and magnetic field H measurements. Bulk superconductivity is inferred from the ρ(T) and Cp(T) data. The ρ(T) data exhibit metallic behavior and a superconducting transition with T(c onset) = 1.98 K and zero resistivity at T(c 0) = 1.67 K. The χ(T) reveals the onset of superconductivity at 2.0 K. For T > 2.0 K, the χ(T) and M(H) are weakly anisotropic paramagnetic with χ(ab) > χ(c). The Cp(T) data confirm the bulk superconductivity below T(c) = 1.69(3) K. The superconducting state electronic heat capacity is analyzed within the framework of a single-band α-model of BCS superconductivity and various normal and superconducting state parameters are estimated. Within the α-model, the Cp(T) data and the ab plane λ(T) data consistently indicate a moderately anisotropic s-wave gap with Δ(0)/k(B)T(c) ≈ 1.6, somewhat smaller than the BCS value of 1.764. The relationship of the heat capacity jump at Tc and the penetration depth measurement to the anisotropy in the s-wave gap is discussed.

  17. Superconductivity and physical properties of CaPd2Ge2 single crystals

    NASA Astrophysics Data System (ADS)

    Anand, V. K.; Kim, H.; Tanatar, M. A.; Prozorov, R.; Johnston, D. C.

    2014-10-01

    We present the superconducting and normal state properties of CaPd2Ge2 single crystals investigated by magnetic susceptibility χ, isothermal magnetization M, heat capacity Cp, in-plane electrical resistivity ρ and London penetration depth λ versus temperature T and magnetic field H measurements. Bulk superconductivity is inferred from the ρ(T) and Cp(T) data. The ρ(T) data exhibit metallic behavior and a superconducting transition with Tc onset = 1.98 K and zero resistivity at Tc 0 = 1.67 K. The χ(T) reveals the onset of superconductivity at 2.0 K. For T > 2.0 K, the χ(T) and M(H) are weakly anisotropic paramagnetic with χab > χc. The Cp(T) data confirm the bulk superconductivity below Tc = 1.69(3) K. The superconducting state electronic heat capacity is analyzed within the framework of a single-band α-model of BCS superconductivity and various normal and superconducting state parameters are estimated. Within the α-model, the Cp(T) data and the ab plane λ(T) data consistently indicate a moderately anisotropic s-wave gap with Δ(0)/kBTc ≈ 1.6, somewhat smaller than the BCS value of 1.764. The relationship of the heat capacity jump at Tc and the penetration depth measurement to the anisotropy in the s-wave gap is discussed.

  18. Superconductivity applications for infrared and microwave devices II; Proceedings of the Meeting, Orlando, FL, Apr. 4, 5, 1991

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

    Topics discussed include thin-film technology, microwave transmission lines and resonators, microwave devices and circuits, infrared detectors and bolometers, and superconducting junctions. Papers are presented on possible enhancement in bolometric response using free-standing film of YBa2Cu3O(x), aging and surface instability in high-Tc superconductors, epitaxial Tl2Ba2CaCu2O8 thin films on LaAlO3 and their microwave device properties, the performance of stripline resonators using sputtered YBCO films, and a coplanar waveguide microwave filter of YBa2Cu3O7. Attention is also given to the performance characteristics of Y-Ba-Cu-O microwave superconducting detectors, high-Tc bolometer developments for planetary missions, infrared detectors from YBaCuO thin films, high-temperature superconductor junction technology, and submillimeter receiver components using superconducting tunnel junctions.

  19. Strong anisotropic thermal conductivity of monolayer WTe2

    NASA Astrophysics Data System (ADS)

    Ma, Jinlong; Chen, Yani; Han, Zheng; Li, Wu

    2016-12-01

    Tungsten ditelluride (WTe2) has attracted increasing attention due to its large magnetoresistance and pressure-induced superconductivity. In this work, we investigate the thermal conductivity (κ) of monolayer WTe2 by performing first-principles calculations, and find strong anisotropic κ with predicted room-temperature values of 9 and 20 W m-1 K-1 along two principal lattice directions, respectively. Such strong anisotropy suggests the importance of orientation when engineering thermal-related applications based on WTe2. The anisotropy of κ is attributed to the in-plane linear acoustic phonon branches, while the out-of-plane quadratic acoustic phonon branch is almost isotropic. The size dependence of κ shows that the size effect can persists up to 10 μm, and the anisotropy decreases with decreasing sample size due to the suppression of low-frequency anisotropic phonons by boundary scattering.

  20. Anisotropic Andreev reflection and Josephson effect in ballistic phosphorene

    NASA Astrophysics Data System (ADS)

    Linder, Jacob; Yokoyama, Takehito

    2017-04-01

    We study Andreev reflection and the Josephson effect in a ballistic monolayer of black phosphorous, known as phosphorene. Due to the anisotropic band structure of this system, the supercurrent changes with an order of magnitude when comparing tunneling along two perpendicular directions in the monolayer. We show that the main reason for this effect is a large difference in the number of transverse modes in Andreev bound states. The oscillatory behavior of the supercurrent as a function of the length and chemical potential of the junction also differs substantially depending on the orientation of the superconducting electrodes deposited on the phosphorene sheet. For Andreev reflection, we show that gate voltaging controls the probability of this process and that the anisotropic behavior found in the supercurrent case is also present for conductance spectra.

  1. Simple Superconducting "Permanent" Electromagnet

    NASA Technical Reports Server (NTRS)

    Israelson, Ulf E.; Strayer, Donald M.

    1992-01-01

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

  2. Simple Superconducting "Permanent" Electromagnet

    NASA Technical Reports Server (NTRS)

    Israelson, Ulf E.; Strayer, Donald M.

    1992-01-01

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

  3. Anisotropic Weyl symmetry and cosmology

    SciTech Connect

    Moon, Taeyoon; Oh, Phillial; Sohn, Jongsu E-mail: ploh@skku.edu

    2010-11-01

    We construct an anisotropic Weyl invariant theory in the ADM formalism and discuss its cosmological consequences. It extends the original anisotropic Weyl invariance of Hořava-Lifshitz gravity using an extra scalar field. The action is invariant under the anisotropic transformations of the space and time metric components with an arbitrary value of the critical exponent z. One of the interesting features is that the cosmological constant term maintains the anisotropic symmetry for z = −3. We also include the cosmological fluid and show that it can preserve the anisotropic Weyl invariance if the equation of state satisfies P = zρ/3. Then, we study cosmology of the Einstein-Hilbert-anisotropic Weyl (EHaW) action including the cosmological fluid, both with or without anisotropic Weyl invariance. The correlation of the critical exponent z and the equation of state parameter ω-bar provides a new perspective of the cosmology. It is also shown that the EHaW action admits a late time accelerating universe for an arbitrary value of z when the anisotropic conformal invariance is broken, and the anisotropic conformal scalar field is interpreted as a possible source of dark energy.

  4. On the relativistic anisotropic configurations

    NASA Astrophysics Data System (ADS)

    Shojai, F.; Kohandel, M.; Stepanian, A.

    2016-06-01

    In this paper we study anisotropic spherical polytropes within the framework of general relativity. Using the anisotropic Tolman-Oppenheimer-Volkov equations, we explore the relativistic anisotropic Lane-Emden equations. We find how the anisotropic pressure affects the boundary conditions of these equations. Also we argue that the behavior of physical quantities near the center of star changes in the presence of anisotropy. For constant density, a class of exact solution is derived with the aid of a new ansatz and its physical properties are discussed.

  5. Fabrication and characterization of ultrafast superconducting optoelectronic devices

    NASA Astrophysics Data System (ADS)

    Adam, Roman

    This thesis describes the complete design, simulation, fabrication, and measurement of high-temperature superconducting optoelectronic devices, intended for conversion of subpicosecond optical pulses into a train of subterahertz bandwidth single flux quantum (SFQ) voltage pulses. Our experimental test structures were patterned in 100- nm-thick YBa 2Cu3O7-x (YBCO) films grown by pulsed laser ablation on (100) MgO bicrystal substrates. Each sample consisted of a coplanar strip transmission line, a microbridge acting as the electrical pulse generator, and up to four Josephson junctions, acting as the pulse shaping circuit. Simulations of our device performance were carried out using numerical analysis based on the resistively and capacitively shunted Josephson junction equivalent circuit. The simulations showed strong dependence of the device response on the input pulse parameters, junction dc bias, loop inductance, and the inductance associated with the junction electrodes (leads). To generate the device input, a train of 100-fs-wide optical pulses from a Ti:sapphire laser photo-excited the superconducting YBCO microbridge and generated 2-ps-wide electrical pulses. The pulses were then used to switch the junction. In addition to the input pulse, junctions were dc-biased at +0.7 Ic, -0.7 Ic, +1.5 Ic, -1.5 Ic and zero- Ic. The time-resolved dynamics of the junction response was measured with the help of our cryogenic electro-optic sampling system, featuring <200-fs time resolution and <150-μV voltage sensitivity. In structures containing a single Josephson junction we obtained 0.65-ps-wide SFQ pulses, generated due to the junction switching process. The response of the multiple- junction devices was dominated by ~0.5-THz oscillatory transient, which corresponded to the resonant frequency of the circuit formed by the double-junction loop and the transmission line capacitance. Junction turn-on delay time observed experimentally was significantly longer than that

  6. Artificial ice using superconducting vortices (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Trastoy Quintela, Juan; Malnou, Maxime; Ulysse, Christian; Bernard, Rozenn; Bergeal, Nicolas; Faini, Giancarlo; Lesueur, Jerome; Briatico, Javier; Villegas, Javier E.

    2016-10-01

    We use magnetic flux quanta (superconducting vortices) on artificial energy landscapes (pinning arrays) to create a new type of artificial ice. This vortex ice shows unusual temperature effects that offer new possibilities in the study of ice systems. We have investigated the matching of the flux lattice to pinning arrays that present geometrical frustration. The pinning arrays are fabricated on YBCO films using masked O+ ion irradiation. The details of the magneto-resistance imply that the flux lattice organizes into a vortex ice. The absence of history-dependent effects suggests that the vortex ice is highly ordered. Due to the technique used for the artificial energy landscape fabrication, we have the ability to change the pinning array geometry using temperature as a control knob. In particular we can switch the geometrical frustration on and off, which opens the door to performing a new type of annealing absent in other artificial ice systems. * Work supported by the French ANR "MASTHER", and the Fundación Barrié (Galicia, Spain)

  7. Anisotropic multiple bounce models

    NASA Astrophysics Data System (ADS)

    Bacalhau, Anna Paula; Peter, Patrick; Vitenti, Sandro D. P.

    2017-07-01

    We analyze the Galileon ghost condensate implementation of a bouncing cosmological model in the presence of a non-negligible anisotropic stress. We exhibit its structure, which we find to be far richer than previously thought. In particular, even restricting attention to a single set of underlying microscopic parameters, we obtain, numerically, many qualitatively different regimes: depending on the initial conditions on the scalar field leading the dynamics of the Universe, the contraction phase can evolve directly towards a singularity, avoid it by bouncing once, or even bounce many times before settling into an ever-expanding phase. We clarify the behavior of the anisotropies in these various situations.

  8. High anisotropic pitch

    SciTech Connect

    Dickakian, G. B.

    1985-11-05

    An improved process for preparing an optically anisotropic pitch which comprises heating a pitch feed material at a temperature within the range of about 350/sup 0/ C. to 450/sup 0/ C. while passing an inert gas therethrough at a rate of at least 2.5 SCFH/lb of pitch feed material and agitating said pitch feed material at a stirrer rate of from about 500 to 600 rpm to obtain an essentially 100% mesophase pitch product suitable for carbon production.

  9. Anisotropic spinfoam cosmology

    NASA Astrophysics Data System (ADS)

    Rennert, Julian; Sloan, David

    2014-01-01

    The dynamics of a homogeneous, anisotropic universe are investigated within the context of spinfoam cosmology. Transition amplitudes are calculated for a graph consisting of a single node and three links—the ‘Daisy graph’—probing the behaviour a classical Bianchi I spacetime. It is shown further how the use of such single node graphs gives rise to a simplification of states such that all orders in the spin expansion can be calculated, indicating that it is the vertex expansion that contains information about quantum dynamics.

  10. Ultralow Friction in a Superconducting Magnetic Bearing

    NASA Technical Reports Server (NTRS)

    Bornemann, Hans J.; Siegel, Michael; Zaitsev, Oleg; Bareiss, Martin; Laschuetza, Helmut

    1996-01-01

    Passive levitation by superconducting magnetic bearings can be utilized in flywheels for energy storage. Basic design criteria of such a bearing are high levitation force, sufficient vertical and horizontal stability and low friction. A test facility was built for the measurement and evaluation of friction in a superconducting magnetic bearing as a function of operating temperature and pressure in the vacuum vessel. The bearing consists of a commercial disk shaped magnet levitated above single grain, melt-textured YBCO high-temperature superconductor material. The superconductor was conduction cooled by an integrated AEG tactical cryocooler. The temperature could be varied from 50 K to 80 K. The pressure in the vacuum chamber was varied from 1 bar to 10(exp -5) mbar. At the lowest pressure setting, the drag torque shows a linear frequency dependence over the entire range investigated (0 less than f less than 40 Hz). Magnetic friction, the frequency independent contribution, is very low. The frequency dependent drag torque is generated by molecular friction from molecule-surface collisions and by eddy currents. Given the specific geometry of the set-up and gas pressure, the molecular drag torque can be estimated. At a speed of 40 Hz, the coefficient of friction (drag-to-lift ratio) was measured to be mu = 1.6 x 10(exp -7) at 10(exp -5) mbar and T = 60 K. This is equivalent to a drag torque of 7.6 x 10(exp -10) Nm. Magnetic friction causes approx. 1% of the total losses. Molecular friction accounts for about 13% of the frequency dependent drag torque, the remaining 87% being due to eddy currents and losses from rotor unbalance. The specific energy loss is only 0.3% per hour.

  11. Enhanced superconductivity of fullerenes

    DOEpatents

    Washington, II, Aaron L.; Teprovich, Joseph A.; Zidan, Ragaiy

    2017-06-20

    Methods for enhancing characteristics of superconductive fullerenes and devices incorporating the fullerenes are disclosed. Enhancements can include increase in the critical transition temperature at a constant magnetic field; the existence of a superconducting hysteresis over a changing magnetic field; a decrease in the stabilizing magnetic field required for the onset of superconductivity; and/or an increase in the stability of superconductivity over a large magnetic field. The enhancements can be brought about by transmitting electromagnetic radiation to the superconductive fullerene such that the electromagnetic radiation impinges on the fullerene with an energy that is greater than the band gap of the fullerene.

  12. Superconductivity fact vs. fancy

    SciTech Connect

    Fitzgerald, K.

    1988-05-01

    The author says great advances have been made in superconductivity. However, the rush to secure recognition combined with public confusion over superconductivity has tainted the field with misconceptions. Some people are saying little progress towards practical use of the ceramics has been made over the last year and many researchers have left what they were doing to study superconductivity. All the hype surrounding the new found ceramic superconductors could give way to a period of disillusionment and frustration. This article discusses recent work in the field of superconductivity. IEEE Spectrum has adopted an attitude of ''just the facts'' in reporting superconductivity news.

  13. Superconductivity in Medicine

    NASA Astrophysics Data System (ADS)

    Alonso, Jose R.; Antaya, Timothy A.

    2012-01-01

    Superconductivity is playing an increasingly important role in advanced medical technologies. Compact superconducting cyclotrons are emerging as powerful tools for external beam therapy with protons and carbon ions, and offer advantages of cost and size reduction in isotope production as well. Superconducting magnets in isocentric gantries reduce their size and weight to practical proportions. In diagnostic imaging, superconducting magnets have been crucial for the successful clinical implementation of magnetic resonance imaging. This article introduces each of those areas and describes the role which superconductivity is playing in them.

  14. Protective link for superconducting coil

    DOEpatents

    Umans, Stephen D.

    2009-12-08

    A superconducting coil system includes a superconducting coil and a protective link of superconducting material coupled to the superconducting coil. A rotating machine includes first and second coils and a protective link of superconducting material. The second coil is operable to rotate with respect to the first coil. One of the first and second coils is a superconducting coil. The protective link is coupled to the superconducting coil.

  15. Low-noise nano superconducting quantum interference device operating in Tesla magnetic fields.

    PubMed

    Schwarz, Tobias; Nagel, Joachim; Wölbing, Roman; Kemmler, Matthias; Kleiner, Reinhold; Koelle, Dieter

    2013-01-22

    Superconductivity in the cuprate YBa(2)Cu(3)O(7) (YBCO) persists up to huge magnetic fields (B) up to several tens of Teslas, and sensitive direct current (dc) superconducting quantum interference devices (SQUIDs) can be realized in epitaxially grown YBCO films by using grain boundary Josephson junctions (GBJs). Here we present the realization of high-quality YBCO nanoSQUIDs, patterned by focused ion beam milling. We demonstrate low-noise performance of such a SQUID up to B = 1 T applied parallel to the plane of the SQUID loop at the temperature T = 4.2 K. The GBJs are shunted by a thin Au layer to provide nonhysteretic current voltage characteristics, and the SQUID incorporates a 90 nm wide constriction which is used for on-chip modulation of the magnetic flux through the SQUID loop. The white flux noise of the device increases only slightly from 1.3 μΦ(0)/(Hz)(1/2) at B = 0 to 2.3 μΦ(0)/(Hz))(1/2) at 1 T. Assuming that a point-like magnetic particle with magnetization in the plane of the SQUID loop is placed directly on top of the constriction and taking into account the geometry of the SQUID, we calculate a spin sensitivity S(μ)(1/2) = 62 μ(B)/(Hz))(1/2) at B = 0 and 110 μ(B)/(Hz))(1/2) at 1 T. The demonstration of low noise of such a SQUID in Tesla fields is a decisive step toward utilizing the full potential of ultrasensitive nanoSQUIDs for direct measurements of magnetic hysteresis curves of magnetic nanoparticles and molecular magnets.

  16. Superconductivity in transition metals.

    PubMed

    Slocombe, Daniel R; Kuznetsov, Vladimir L; Grochala, Wojciech; Williams, Robert J P; Edwards, Peter P

    2015-03-13

    A qualitative account of the occurrence and magnitude of superconductivity in the transition metals is presented, with a primary emphasis on elements of the first row. Correlations of the important parameters of the Bardeen-Cooper-Schrieffer theory of superconductivity are highlighted with respect to the number of d-shell electrons per atom of the transition elements. The relation between the systematics of superconductivity in the transition metals and the periodic table high-lights the importance of short-range or chemical bonding on the remarkable natural phenomenon of superconductivity in the chemical elements. A relationship between superconductivity and lattice instability appears naturally as a balance and competition between localized covalent bonding and so-called broken covalency, which favours d-electron delocalization and superconductivity. In this manner, the systematics of superconductivity and various other physical properties of the transition elements are related and unified. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

  17. Long length oxide template for YBCO coated conductor prepared by surface-oxidation epitaxy method

    NASA Astrophysics Data System (ADS)

    Watanabe, Tomonori; Matsumoto, Kaname; Maeda, Toshihiko; Tanigawa, Toru; Hirabayashi, Izumi

    2001-08-01

    A 50 m long, biaxially textured NiO buffer layer for epitaxial growth ofYBa 2Cu 3O 7- δ (YBCO) film has been fabricated on the long cube textured nickel tape using surface-oxidation epitaxy (SOE) method. The SOE-NiO layers were highly {1 0 0} <0 0 1> textured. The full width at half maximum of 10-14.5° from X-ray φ-scan ( Δφ) was in the range of 10-14.5° through the whole length. The critical current density ( Jc) values exceeding 0.3 MA/cm 2 (77 K, 0 T) have been obtained in short samples of YBCO films on NiO/Ni tapes, by using thin MgO cap layer. Thirty meters long Ni-clad Ni-20wt.%Cr (Ni/NiCr) and Ni-clad austenitic stainless steel (Ni/SS) tapes were also prepared for YBCO coated conductors with higher strength and lower magnetism than those of pure nickel tape. Highly {1 0 0} <0 0 1> textured NiO layers were formed on those textured composite tapes by SOE method as same as on cube textured pure nickel tapes. YBCO films with Jc of 0.1 MA/cm 2 (77 K, 0 T) have been obtained on MgO/SOE-NiO layer of short Ni/NiCr composite tape.

  18. 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.

  19. Experimental studies of helical solenoid model based on YBCO tape-bridge joints

    SciTech Connect

    Yu, M.; Lombardo, V.; Turrioni, D.; Zlobin, A.V.; Flangan, G.; Lopes, M.L.; Johnson, R.P.; /Fermilab

    2011-06-01

    Helical solenoids that provide solenoid, helical dipole and helical gradient field components are designed for a helical cooling channel (HCC) proposed for cooling of muon beams in a muon collider. The high temperature superconductor (HTS), 12 mm wide and 0.1 mm thick YBCO tape, is used as the conductor for the highest-field section of HCC due to certain advantages, such as its electrical and mechanical properties. To study and address the design, and technological and performance issues related to magnets based on YBCO tapes, a short helical solenoid model based on double-pancake coils was designed, fabricated and tested at Fermilab. Splicing joints were made with Sn-Pb solder as the power leads and the connection between coils, which is the most critical element in the magnet that can limit the performance significantly. This paper summarizes the test results of YBCO tape and double-pancake coils in liquid nitrogen and liquid helium, and then focuses on the study of YBCO splices, including the soldering temperatures and pressures, and splice bending test.

  20. A newly designed ultrasonic spray pyrolysis device to fabricate YBCO tapes

    NASA Astrophysics Data System (ADS)

    Liu, M.; Zhou, M. L.; Zhai, L. H.; Liu, D. M.; Gao, X.; Liu, W.

    2003-04-01

    A newly designed ultrasonic spray pyrolysis device has been manufactured to fabricate YBCO tapes. The apparatus is primarily composed of four zones: the ultrasonic generator, the atomization chamber, the pyrolysis chamber and the rotating equipment. Every part of them is designed and fabricated by us. The whole system costs far less than the ready-made equipment facility in which there is always a vacuum apparatus. This apparatus with processing parameters accurately controlled can fabricate short and long YBCO tapes. In this paper, we mainly focused on how to design and manufacture four parts of the ultrasonic spray pyrolysis. We have deposited c-axis aligned short YBCO tapes on biaxially textured Ag {1 1 0}<1 1 0> substrates with Jc=10 3 A/cm 2 using this method with our device. The method is very promising in terms of its precise control of metal compositions, high deposition rate and low cost non-vacuum approach. Improvements of this technique are being carried out to fabricate long YBCO tapes.

  1. Conductivity and interferometry experiments on YBCO/lead ramp-edge Josephson junctions

    NASA Astrophysics Data System (ADS)

    Hilliard, Joseph Edward, Jr.

    In this thesis, we study the details of the order parameter symmetry in arbitrary directions of the high-temperature cuprate superconductor YBa 2Cu3O7-y (YBCO) using YBCO/Pb ramp-edge Josephson junctions with lithographically defined corner and straight-edge geometries. Measurements of the critical current versus applied field, I c(H), and the an dynamic conductance, dI/dV, are presented. For junctions with corner geometries, as well as for most of the straight-edge junctions, the known dx2-y2 order parameter symmetry of YBCO is confirmed. For some of the straight-edge junctions oriented near 45° with respect to the YBCO a and b axes, an anomalous temperature dependence of the Ic(H) pattern is found in the range from 5 down to 1.4 K. We consider the onset of a secondary order parameter and the onset of second-order Josephson coupling as possible interpretations of this anomalous temperature dependence and we find the second-order Josephson coupling interpretation more likely.

  2. Dynamical effects of an unconventional current-phase relation in YBCO dc SQUIDs.

    PubMed

    Lindström, T; Charlebois, S A; Tzalenchuk, A Ya; Ivanov, Z; Amin, M H S; Zagoskin, A M

    2003-03-21

    The predominant d-wave pairing symmetry in high-temperature superconductors allows for a variety of current-phase relations in Josephson junctions, which is to a certain degree fabrication controlled. In this Letter, we report on direct experimental observations of the effects of a nonsinusoidal current-phase dependence in YBCO dc SQUIDs, which agree with the theoretical description of the system.

  3. New method for introducing nanometer flux pinning centers into single domain YBCO bulk superconductors

    NASA Astrophysics Data System (ADS)

    Yang, W. M.; Wang, Miao

    2013-10-01

    Single domain YBCO superconductors with different additions of Bi2O3 have been fabricated by top seeded infiltration and growth process (TSIG). The effect of Bi2O3 additions on the growth morphology, microstructure and levitation force of the YBCO bulk superconductor has been investigated. The results indicate that single domain YBCO superconductors can be fabricated with the additions of Bi2O3 less than 2 wt%; Bi2O3 can be reacted with Y2BaCuO5 and liquid phase and finally form Y2Ba4CuBiOx(YBi2411) nanoscale particles; the size of the YBi2411 particles is about 100 nm, which can act as effective flux pinning centers. It is also found that the levitation force of single domain YBCO bulks is increasing from 13 N to 34 N and decreasing to 11 N with the increasing of Bi2O3 addition from 0.1 wt% to 0.7 wt% and 2 wt%. This result is helpful for us to improve the physical properties of REBCO bulk superconductors.

  4. Ordered YBCO sub-micron array structures induced by pulsed femtosecond laser irradiation.

    PubMed

    Luo, C W; Lee, C C; Li, C H; Shih, H C; Chen, Y-J; Hsieh, C C; Su, C H; Tzeng, W Y; Wu, K H; Juang, J Y; Uen, T M; Chen, S P; Lin, J-Y; Kobayashi, T

    2008-12-08

    We report on the formation of organized sub-micron YBa(2)Cu(3)O(7) (YBCO) dots induced by irradiating femtosecond laser pulses on YBCO films prepared by pulse laser deposition with fluence in the range of 0.21 approximately 0.53 J/cm(2). The morphology of the YBCO film surface depends strongly on the laser fluences irradiated. At lower laser fluence (approximately 0.21 J/cm(2)) the morphology was pattern of periodic ripples with sub-micrometer spacing. Slightly increasing the laser fluence to 0.26 J/cm(2) changes the pattern into organized sub-micron dots with diameters ranging from 100 nm to 800 nm and height of 150 nm. Further increase of the laser fluence to over 0.32 J/cm(2), however, appeared to result in massive melting and led to irregular morphology. The mechanism and the implications of the current findings will be discussed. Arrays of YBCO sub-micron dots with T(c) = 89.7 K were obtained.

  5. Inhomogeneous anisotropic cosmology

    NASA Astrophysics Data System (ADS)

    Kleban, Matthew; Senatore, Leonardo

    2016-10-01

    In homogeneous and isotropic Friedmann-Robertson-Walker cosmology, the topology of the universe determines its ultimate fate. If the Weak Energy Condition is satisfied, open and flat universes must expand forever, while closed cosmologies can recollapse to a Big Crunch. A similar statement holds for homogeneous but anisotropic (Bianchi) universes. Here, we prove that arbitrarily inhomogeneous and anisotropic cosmologies with ``flat'' (including toroidal) and ``open'' (including compact hyperbolic) spatial topology that are initially expanding must continue to expand forever at least in some region at a rate bounded from below by a positive number, despite the presence of arbitrarily large density fluctuations and/or the formation of black holes. Because the set of 3-manifold topologies is countable, a single integer determines the ultimate fate of the universe, and, in a specific sense, most 3-manifolds are ``flat'' or ``open''. Our result has important implications for inflation: if there is a positive cosmological constant (or suitable inflationary potential) and initial conditions for the inflaton, cosmologies with ``flat'' or ``open'' topology must expand forever in some region at least as fast as de Sitter space, and are therefore very likely to begin inflationary expansion eventually, regardless of the scale of the inflationary energy or the spectrum and amplitude of initial inhomogeneities and gravitational waves. Our result is also significant for numerical general relativity, which often makes use of periodic (toroidal) boundary conditions.

  6. Inhomogeneous anisotropic cosmology

    SciTech Connect

    Kleban, Matthew; Senatore, Leonardo

    2016-10-12

    In homogeneous and isotropic Friedmann-Robertson-Walker cosmology, the topology of the universe determines its ultimate fate. If the Weak Energy Condition is satisfied, open and flat universes must expand forever, while closed cosmologies can recollapse to a Big Crunch. A similar statement holds for homogeneous but anisotropic (Bianchi) universes. Here, we prove that arbitrarily inhomogeneous and anisotropic cosmologies with “flat” (including toroidal) and “open” (including compact hyperbolic) spatial topology that are initially expanding must continue to expand forever at least in some region at a rate bounded from below by a positive number, despite the presence of arbitrarily large density fluctuations and/or the formation of black holes. Because the set of 3-manifold topologies is countable, a single integer determines the ultimate fate of the universe, and, in a specific sense, most 3-manifolds are “flat” or “open”. Our result has important implications for inflation: if there is a positive cosmological constant (or suitable inflationary potential) and initial conditions for the inflaton, cosmologies with “flat” or “open” topology must expand forever in some region at least as fast as de Sitter space, and are therefore very likely to begin inflationary expansion eventually, regardless of the scale of the inflationary energy or the spectrum and amplitude of initial inhomogeneities and gravitational waves. Our result is also significant for numerical general relativity, which often makes use of periodic (toroidal) boundary conditions.

  7. Inhomogeneous anisotropic cosmology

    DOE PAGES

    Kleban, Matthew; Senatore, Leonardo

    2016-10-12

    In homogeneous and isotropic Friedmann-Robertson-Walker cosmology, the topology of the universe determines its ultimate fate. If the Weak Energy Condition is satisfied, open and flat universes must expand forever, while closed cosmologies can recollapse to a Big Crunch. A similar statement holds for homogeneous but anisotropic (Bianchi) universes. Here in this paper, we prove that arbitrarily inhomogeneous and anisotropic cosmologies with "flat'' (including toroidal) and "open'' (including compact hyperbolic) spatial topology that are initially expanding must continue to expand forever at least in some region at a rate bounded from below by a positive number, despite the presence of arbitrarilymore » large density fluctuations and/or the formation of black holes. Because the set of 3-manifold topologies is countable, a single integer determines the ultimate fate of the universe, and, in a specific sense, most 3-manifolds are "flat" or "open". Our result has important implications for inflation: if there is a positive cosmological constant (or suitable inflationary potential) and initial conditions for the inflaton, cosmologies with "flat'' or "open" topology must expand forever in some region at least as fast as de Sitter space, and are therefore very likely to begin inflationary expansion eventually, regardless of the scale of the inflationary energy or the spectrum and amplitude of initial inhomogeneities and gravitational waves. Our result is also significant for numerical general relativity, which often makes use of periodic (toroidal) boundary conditions.« less

  8. Inhomogeneous anisotropic cosmology

    SciTech Connect

    Kleban, Matthew; Senatore, Leonardo

    2016-10-12

    In homogeneous and isotropic Friedmann-Robertson-Walker cosmology, the topology of the universe determines its ultimate fate. If the Weak Energy Condition is satisfied, open and flat universes must expand forever, while closed cosmologies can recollapse to a Big Crunch. A similar statement holds for homogeneous but anisotropic (Bianchi) universes. Here in this paper, we prove that arbitrarily inhomogeneous and anisotropic cosmologies with "flat'' (including toroidal) and "open'' (including compact hyperbolic) spatial topology that are initially expanding must continue to expand forever at least in some region at a rate bounded from below by a positive number, despite the presence of arbitrarily large density fluctuations and/or the formation of black holes. Because the set of 3-manifold topologies is countable, a single integer determines the ultimate fate of the universe, and, in a specific sense, most 3-manifolds are "flat" or "open". Our result has important implications for inflation: if there is a positive cosmological constant (or suitable inflationary potential) and initial conditions for the inflaton, cosmologies with "flat'' or "open" topology must expand forever in some region at least as fast as de Sitter space, and are therefore very likely to begin inflationary expansion eventually, regardless of the scale of the inflationary energy or the spectrum and amplitude of initial inhomogeneities and gravitational waves. Our result is also significant for numerical general relativity, which often makes use of periodic (toroidal) boundary conditions.

  9. Anisotropic Particles in Turbulence

    NASA Astrophysics Data System (ADS)

    Voth, Greg A.; Soldati, Alfredo

    2017-01-01

    Anisotropic particles are common in many industrial and natural turbulent flows. When these particles are small and neutrally buoyant, they follow Lagrangian trajectories while exhibiting rich orientational dynamics from the coupling of their rotation to the velocity gradients of the turbulence field. This system has proven to be a fascinating application of the fundamental properties of velocity gradients in turbulence. When particles are not neutrally buoyant, they experience preferential concentration and very different preferential alignment than neutrally buoyant tracer particles. A vast proportion of the parameter range of anisotropic particles in turbulence is still unexplored, with most existing research focusing on the simple foundational cases of axisymmetric ellipsoids at low concentrations in homogeneous isotropic turbulence and in turbulent channel flow. Numerical simulations and experiments have recently developed a fairly comprehensive picture of alignment and rotation in these cases, and they provide an essential foundation for addressing more complex problems of practical importance. Macroscopic effects of nonspherical particle dynamics include preferential concentration in coherent structures and drag reduction by fiber suspensions. We review the models used to describe nonspherical particle motion, along with numerical and experimental methods for measuring particle dynamics.

  10. Trapped Field Characteristics of Stacked YBCO Thin Plates for Compact NMR Magnets: Spatial Field Distribution and Temporal Stability.

    PubMed

    Hahn, Seungyong; Kim, Seok Beom; Ahn, Min Cheol; Voccio, John; Bascuñán, Juan; Iwasa, Yukikazu

    2010-06-01

    This paper presents experimental and analytical results of trapped field characteristics of a stack of square YBCO thin film plates for compact NMR magnets. Each YBCO plate, 40 mm × 40 mm × 0.08 mm, has a 25-mm diameter hole at its center. A total of 500 stacked plates were used to build a 40-mm long magnet. Its trapped field, in a bath of liquid nitrogen, was measured for spatial field distribution and temporal stability. Comparison of measured and analytical results is presented: the effects on trapped field characteristics of the unsaturated nickel substrate and the non-uniform current distribution in the YBCO plate are discussed.

  11. Trapped Field Characteristics of Stacked YBCO Thin Plates for Compact NMR Magnets: Spatial Field Distribution and Temporal Stability

    PubMed Central

    Hahn, Seungyong; Kim, Seok Beom; Ahn, Min Cheol; Voccio, John; Bascuñán, Juan; Iwasa, Yukikazu

    2010-01-01

    This paper presents experimental and analytical results of trapped field characteristics of a stack of square YBCO thin film plates for compact NMR magnets. Each YBCO plate, 40 mm × 40 mm × 0.08 mm, has a 25-mm diameter hole at its center. A total of 500 stacked plates were used to build a 40-mm long magnet. Its trapped field, in a bath of liquid nitrogen, was measured for spatial field distribution and temporal stability. Comparison of measured and analytical results is presented: the effects on trapped field characteristics of the unsaturated nickel substrate and the non-uniform current distribution in the YBCO plate are discussed. PMID:20585463

  12. Enhancing the design of a superconducting coil for magnetic energy storage systems

    NASA Astrophysics Data System (ADS)

    Indira, Gomathinayagam; UmaMaheswaraRao, Theru; Chandramohan, Sankaralingam

    2015-01-01

    Study and analysis of a coil for Superconducting Magnetic Energy Storage (SMES) system is presented in this paper. Generally, high magnetic flux density is adapted in the design of superconducting coil of SMES to reduce the size of the coil and to increase its energy density. With high magnetic flux density, critical current density of the coil is degraded and so the coil is wound with High Temperature Superconductors (HTS) made of different materials. A comparative study is made to emphasize the relationship between the energy storage and length of the coil wound by Bi2223, SF12100, SCS12100 and YBCO tapes. Recently for the construction of HTS magnets, YBCO tapes have been used. Simulation models for various designs have been developed to analyze the magnetic field distribution for the optimum design of energy storage. The design which gives the maximum stored energy in the coil has been used with a certain length of second-generation HTS. The performance analysis and the results of comparative study are done.

  13. Superconducting antennas for telecommunication applications based on dual mode cross slotted patches

    NASA Astrophysics Data System (ADS)

    Cassinese, A.; Barra, M.; Fragalà, I.; Kusunoki, M.; Malandrino, G.; Nakagawa, T.; Perdicaro, L. M. S.; Sato, K.; Ohshima, S.; Vaglio, R.

    2002-08-01

    Dual mode devices based on high temperature superconducting films represent an interesting class for telecommunication applications since they combine a miniaturized size with a good power handling. Here we report on a novel compact antenna obtained by crossing a square patch with two or more slots. The proposed design has an antenna size reduction of about 40% as compared to the conventional square patch microstrip antennas. Single patch antenna both with linear (LP) and circular (CP) polarization operating in the X-band have been designed and tested at prototype level. They are realized by using double sided (YBa 2Cu 3O 7- x) YBCO and Tl 2Ba 2Ca 1Cu 2O 8 (Tl-2212) superconducting films grown on MgO substrates and tested with a portable cryocooler. They showed at T=77 K a return loss <25 dB and a power handling of 23 dBm. Exemplary 16 elements arrays LP antennas operating in the X band have been also realized by using YBCO film grown on 2 ″ diameter MgO substrate.

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

    PubMed

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

    2013-01-01

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

  15. Theoretical analysis of NMR experiments in normal and superconducting states of high- Tc superconductors

    NASA Astrophysics Data System (ADS)

    Mack, Frank; Kulić, Miodrag L.; Mehring, Michael

    1998-01-01

    The Knight shift and T1- and T2-rates of YBa 2Cu 3O 6+ x in the normal and superconducting state are modeled by calculating the magnetic susceptibility in the bi-layer Hubbard model within various approximations. An optimal set of parameters (OSP) is found in the RPA approximation which fits experiments on YBCO for optimal and nearly optimal doping. The analysis of the self-consistent FLEX approximation for the particle self-energy and susceptibility shows that the latter is renormalized quantitatively but not qualitatively. The differences in the oxygen and copper T1-rates are explained by using the OSP parameters and assuming the finite hyperfine coupling C‧ between 17O and next-nearest neighboring Cu spins. The numerical analysis of T1-1 and T2-1 and the ratio 63T1 ab-1/ 63T1 c-1 in the superconducting state supports strongly the idea of d-wave pairing in YBa 2Cu 3O 7 with much stronger intraplane rather than interplane pairing. It is also shown that the simple RPA or FLEX approximations are inadequate in explaining NMR data in underdoped YBCO systems, where antiferromagnetic fluctuations are very pronounced.

  16. Anisotropic power-law inflation

    SciTech Connect

    Kanno, Sugumi; Soda, Jiro; Watanabe, Masa-aki E-mail: jiro@tap.scphys.kyoto-u.ac.jp

    2010-12-01

    We study an inflationary scenario in supergravity model with a gauge kinetic function. We find exact anisotropic power-law inflationary solutions when both the potential function for an inflaton and the gauge kinetic function are exponential type. The dynamical system analysis tells us that the anisotropic power-law inflation is an attractor for a large parameter region.

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

    NASA Astrophysics Data System (ADS)

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

    2017-09-01

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

  18. Superconducting YBa{sub 2}Cu{sub 3}O{sub 7{minus}x} thin films on polycrystalline ferrite for magnetically tunable microwave components

    SciTech Connect

    Jia, Q.X.; Findikoglu, A.T.; Arendt, P.; Foltyn, S.R.; Roper, J.M.; Groves, J.R.; Coulter, J.Y.; Li, Y.Q.; Dionne, G.F.

    1998-04-01

    Superconducting YBa{sub 2}Cu{sub 3}O{sub 7{minus}x} (YBCO) thin films with a surface resistance of 0.86 m{Omega} at 10 GHz and 76 K have been grown on polycrystalline ferrite yttrium iron garnet (YIG) substrates. The chemical and structural mismatches between YBCO and YIG are solved by using a double buffer layer of biaxially oriented yttria-stabilized zirconia (YSZ) and CeO{sub 2}, where YSZ is deposited by an ion-beam-assisted-deposition technique. The YBCO films are {ital c} axis oriented with an in-plane mosaic spread [full width at half maximum of an x-ray {phi}-scan on (103) reflection] of less than 8{degree}. The films have a superconductive transition temperature above 88 K with a transition width less than 0.3 K, giving a critical current density above 10{sup 6}A/cm{sup 2} in self field at 75 K. At 75 K in an external magnetic field of 1 T perpendicular to the film surface, the films maintain a critical current density over 2{times}10{sup 5}A/cm{sup 2}. {copyright} {ital 1998 American Institute of Physics.}

  19. Pd layer on cube-textured substrates for MOD-TFA and PLD YBCO coated conductors

    NASA Astrophysics Data System (ADS)

    Mancini, A.; Celentano, G.; Galluzzi, V.; Rufoloni, A.; Vannozzi, A.; Augieri, A.; Ciontea, L.; Petrisor, T.; Gambardella, U.; Longo, G.; Cricenti, A.

    2008-01-01

    Pd films were deposited on rolling assisted biaxially textured substrate (RABiTS) Ni-5 at.% W in order to exploit the Pd effect of the texture sharpening with respect to that of the substrate, for the development of YBa2Cu3O7-x (YBCO) coated conductors. The Pd sharpening effect was relevant in the out-of-plane direction where the reduction for the ω-scans' full width at half maximum (FWHM) ranged from 55 to 65%, depending on the substrate roughness. The obtained minimum values of the FWHM in the transverse rolling direction of the (002) Pd ω-scan and in the (111) Pd phi-scan were of about 2.5° and 5°, respectively. The CeO2/YSZ/CeO2 (YSZ is Y2O3-stabilised ZrO2) heterostructure of the buffer layer was developed by pulsed laser deposition (PLD). In order to transfer the sharp orientation of the Pd film, both the seed CeO2 layer and the YSZ layer were deposited at low temperatures (450 °C), low enough to avoid Pd/Ni-W interdiffusion. The YBCO, films deposited by both PLD and metal-organic deposition (MOD) using metal trifluoroacetate acid (TFA), exhibited rolling direction (005) ω-scan and the (113) phi-scan FWHM values of about 2° and 5°, respectively. In spite of the complete interdiffusion between Ni and Pd during the YBCO film deposition, the coated conductors exhibit good adherence, as well as a smooth and crack-free surface. A zero-resistance critical temperature (TC0) of 90.8 K for the MOD-TFA YBCO films and critical current-density (JC) up to 2.2 MA cm-2 at 77 K and self-field for PLD YBCO films have been obtained.

  20. NMR evidence of anisotropic Kondo liquid behavior in CeIrIn5

    NASA Astrophysics Data System (ADS)

    Shockley, A. C.; Shirer, K. R.; Crocker, J.; Dioguardi, A. P.; Lin, C. H.; Nisson, D. M.; apRoberts-Warren, N.; Klavins, P.; Curro, N. J.

    2015-08-01

    We report detailed Knight-shift measurements of the two indium sites in the heavy-fermion compound CeIrIn5 as a function of temperature and field orientation. We find that the Knight-shift anomaly is orientation dependent, with a crossover temperature T* that varies by 50% as the field is rotated from (001) to (100). This result suggests that the hybridization between the Ce 4 f states and the itinerant conduction electrons is anisotropic, a result that reflects its collective origin, and may lead to anisotropic Kondo liquid behavior and unconventional superconductivity.

  1. Probing the superconducting gap structure of (Li1 -xFex)OHFeSe

    NASA Astrophysics Data System (ADS)

    Smidman, M.; Pang, G. M.; Zhou, H. X.; Wang, N. Z.; Xie, W.; Weng, Z. F.; Chen, Y.; Dong, X. L.; Chen, X. H.; Zhao, Z. X.; Yuan, H. Q.

    2017-07-01

    We report measurements of the London penetration depth [Δ λ (T )] of the recently discovered iron-based superconductor (Li1 -xFex )OHFeSe, in order to characterize the nature of the superconducting gap structure. At low temperatures, Δ λ (T ) displays nearly temperature-independent behavior, indicating a fully open superconducting gap. We also analyze the superfluid density ρs(T ) , which cannot be well accounted for by a single-gap isotropic s -wave model but is consistent with either a two-gap model, a model for the orbital selective s ×τ3 state, or anisotropic s -wave superconductivity.

  2. Electron-phonon interaction and pairing mechanism in superconducting Ca-intercalated bilayer graphene

    NASA Astrophysics Data System (ADS)

    Margine, E. R.; Lambert, Henry; Giustino, Feliciano

    2016-02-01

    Using the ab initio anisotropic Eliashberg theory including Coulomb interactions, we investigate the electron-phonon interaction and the pairing mechanism in the recently-reported superconducting Ca-intercalated bilayer graphene. We find that C6CaC6 can support phonon-mediated superconductivity with a critical temperature Tc = 6.8-8.1 K, in good agreement with experimental data. Our calculations indicate that the low-energy Caxy vibrations are critical to the pairing, and that it should be possible to resolve two distinct superconducting gaps on the electron and hole Fermi surface pockets.

  3. Fabrication of textured YBCO bulks with artificial holes

    NASA Astrophysics Data System (ADS)

    Noudem, J. G.; Meslin, S.; Horvath, D.; Harnois, C.; Chateigner, D.; Eve, S.; Gomina, M.; Chaud, X.; Murakami, M.

    2007-10-01

    The recently reported hole-patterned YBa2Cu3Oy (Y123) bulks with improved superconducting properties are highly interesting from the aspects of the material qualities and application various points of view. It is well known that the core of plain bulk superconductors needs to be fully oxygenated and some defects like cracks, pores and voids must be suppressed in order that the material can trap high magnetic field or carry high current densities. To minimize the above defects, we have used the infiltration and top seed growth (ITSG) process to prepare regularly perforated YBa2Cu3Oy (Y123) bulk superconductors. This process involves less shrinkage during annealing and a uniform distribution of Y211 inclusions. The texture was evidenced by neutron pole figure measurements. Flux mapping was used to verify the superconducting homogeneity of the samples and to investigate the field trapping ability. Large increase of the trapped field in pulsed magnetization up to 60% in comparison to the hole-free parent sample with the same thermal history has been obtained. In addition, the textured drilled samples were reinforced using resin or metal impregnation and the influence of the different processing steps on the hardness of the materials is investigated.

  4. Anisotropic Kepler and anisotropic two fixed centres problems

    NASA Astrophysics Data System (ADS)

    Maciejewski, Andrzej J.; Przybylska, Maria; Szumiński, Wojciech

    2017-02-01

    In this paper we show that the anisotropic Kepler problem is dynamically equivalent to a system of two point masses which move in perpendicular lines (or planes) and interact according to Newton's law of universal gravitation. Moreover, we prove that generalised version of anisotropic Kepler problem as well as anisotropic two centres problem are non-integrable. This was achieved thanks to investigation of differential Galois groups of variational equations along certain particular solutions. Properties of these groups yield very strong necessary integrability conditions.

  5. Thermodynamics of anisotropic branes

    NASA Astrophysics Data System (ADS)

    Ávila, Daniel; Fernández, Daniel; Patiño, Leonardo; Trancanelli, Diego

    2016-11-01

    We study the thermodynamics of flavor D7-branes embedded in an anisotropic black brane solution of type IIB supergravity. The flavor branes undergo a phase transition between a `Minkowski embedding', in which they lie outside of the horizon, and a `black hole embedding', in which they fall into the horizon. This transition depends on the black hole temperature, its degree of anisotropy, and the mass of the flavor degrees of freedom. It happens either at a critical temperature or at a critical anisotropy. A general lesson we learn from this analysis is that the anisotropy, in this particular realization, induces similar effects as the temperature. In particular, increasing the anisotropy bends the branes more and more into the horizon. Moreover, we observe that the transition becomes smoother for higher anisotropies.

  6. Magnetic preferential orientation of metal oxide superconducting materials

    DOEpatents

    Capone, D.W.; Dunlap, B.D.; Veal, B.W.

    1990-07-17

    A superconductor comprised of a polycrystalline metal oxide such as YBa[sub 2]Cu[sub 3]O[sub 7[minus]X] (where 0 < X < 0.5) exhibits superconducting properties and is capable of conducting very large current densities. By aligning the two-dimensional Cu-O layers which carry the current in the superconducting state in the a- and b-directions, i.e., within the basal plane, a high degree of crystalline axes alignment is provided between adjacent grains permitting the conduction of high current densities. The highly anisotropic diamagnetic susceptibility of the polycrystalline metal oxide material permits the use of an applied magnetic field to orient the individual crystals when in the superconducting state to substantially increase current transport between adjacent grains. In another embodiment, the anisotropic paramagnetic susceptibility of rare-earth ions substituted into the oxide material is made use of as an applied magnetic field orients the particles in a preferential direction. This latter operation can be performed with the material in the normal (non-superconducting) state. 4 figs.

  7. Magnetic preferential orientation of metal oxide superconducting materials

    DOEpatents

    Capone, Donald W.; Dunlap, Bobby D.; Veal, Boyd W.

    1990-01-01

    A superconductor comprised of a polycrystalline metal oxide such as YBa.sub.2 Cu.sub.3 O.sub.7-X (where 0superconducting properties and is capable of conducting very large current densities. By aligning the two-dimensional Cu-O layers which carry the current in the superconducting state in the a- and b-directions, i.e., within the basal plane, a high degree of crystalline axes alignment is provided between adjacent grains permitting the conduction of high current densities. The highly anisotropic diamagnetic susceptibility of the polycrystalline metal oxide material permits the use of an applied magnetic field to orient the individual crystals when in the superconducting state to substantially increase current transport between adjacent grains. In another embodiment, the anisotropic paramagnetic susceptibility of rare-earth ions substituted into the oxide material is made use of as an applied magnetic field orients the particles in a preferential direction. This latter operation can be performed with the material in the normal (non-superconducting) state.

  8. Magnetic forces in high-T(sub c) superconducting bearings

    NASA Technical Reports Server (NTRS)

    Moon, F. C.

    1990-01-01

    In September 1987 research at Cornell levitated a small rotor on superconducting bearing at 10,000 rpm. In April 1989 a speed of 120,000 rpm was achieved in a passive bearing with no active control. The bearing material used was YBa2Cu3O7. There is no evidence that the rotation speed has any significant effect on the lift force. Magnetic force measurements between a permanent rare-earth magnet and high T(sub c) superconducting material versus vertical and lateral displacements were made. A large hysteresis loop results for large displacements, while minor loops result for small displacements. These minor loops seem to give a slope proportional to the magnetic stiffness, and are probably indicative of flux pinning forces. Experiments of rotary speed versus time show a linear decay in a vacuum. Measurements of magnetic drag forces of a magnetic dipole over a high-T(sub c) superconducting disc of YBCO show that the drag force reaches a constant value, independent of the speed. Dampling of lateral vibrations of levitated rotors were measured which indicates that transverse flux motion in the superconductor will create dissipation. As a result of these force measurements, an optimum shape for the superconductor bearing pads which gives good lateral and axial stability was designed. Recent force measurements on melt-quench processed superconductors indicate a substantial increase in levitation force and magnetic stiffness over free sintered materials. As a result, application of high-T(sub c) superconducting bearings are beginning to show great promise at this time.

  9. Superconductivity in intercalated group-IV honeycomb structures

    NASA Astrophysics Data System (ADS)

    Flores-Livas, José A.; Sanna, Antonio

    2015-02-01

    We present a theoretical investigation on the electron-phonon superconductivity of honeycomb M X2 layered structures where X is one element of group IV (C, Si, or Ge) and M is an alkali or an alkaline-earth metal. Among the studied compositions we predict a TC of 7 K in RbGe2, 9 K in RbSi2, and 11 K in SrC2. All these compounds feature a strongly anisotropic superconducting gap. Our results show that despite the different doping levels and structural properties, the three families of materials fall into a similar description of their superconducting behavior. This allows us to estimate an upper critical temperature of about 20 K for the class of intercalated group-IV structures, including intercalated graphite and doped graphene.

  10. Superconductivity in Heavy Alkaline-Earth Intercalated Graphites

    NASA Astrophysics Data System (ADS)

    Kim, J. S.; Boeri, L.; O'Brien, J. R.; Razavi, F. S.; Kremer, R. K.

    2007-07-01

    We report the discovery of superconductivity below 1.65(6) K in Sr-intercalated graphite SrC6, by susceptibility and specific heat (Cp) measurements. In comparison with CaC6, we found that the anisotropy of the upper critical fields for SrC6 is much reduced. The Cp anomaly at Tc is smaller than the BCS prediction, indicating an anisotropic superconducting gap for SrC6 similar to CaC6. The significantly lower Tc of SrC6 as compared to CaC6 can be understood in terms of “negative” pressure effects, which decreases the electron-phonon coupling for both in-plane intercalant and the out-of-plane C phonon modes. We observed no superconductivity for BaC6 down to 0.3 K.

  11. Spin Orbit Effects and Superconductivity in Oxide Materials

    SciTech Connect

    Chapline, G F

    2005-09-29

    In a variety of materials superconductivity is associated with the existence of a quantum critical point (QCP). In the case of the hole doped cuprates there is evidence which suggests that the important quantum degrees of freedom near the superconducting critical point are localized charge and spin density fluctuations. We argue that if these degrees of freedom are strongly coupled by spin-orbit interactions, a new type of quantum criticality arises with monopole-like quasi-particles as the important quantum degrees of freedom,. In layered material this type of quantum criticality can be modeled using a 2-dimensional non-linear Schrodinger equation with an SU(N) gauge field. We exhibit a pairing wave function for quasi-particles that has topological order and anisotropic properties. The superconducting transition would in some respects resemble a KT transition.

  12. Development of YBCO Superconductor for Electric Systems: Cooperative Research and Development Final Report, CRADA Number CRD-04-150

    SciTech Connect

    Bhattacharya, R.

    2013-03-01

    The proposed project will be collaborative in exploration of high temperature superconductor oxide films between SuperPower, Inc. and the National Renewable Energy Laboratory. This CRADA will attempt to develop YBCO based high temperature oxide technology.

  13. Superconductive radiofrequency window assembly

    DOEpatents

    Phillips, H.L.; Elliott, T.S.

    1998-05-19

    The present invention is a superconducting radiofrequency window assembly for use in an electron beam accelerator. The SRF window assembly has a superconducting metal-ceramic design. The SRF window assembly comprises a superconducting frame, a ceramic plate having a superconducting metallized area, and a superconducting eyelet for sealing plate into frame. The plate is brazed to eyelet which is then electron beam welded to frame. A method for providing a ceramic object mounted in a metal member to withstand cryogenic temperatures is also provided. The method involves a new metallization process for coating a selected area of a ceramic object with a thin film of a superconducting material. Finally, a method for assembling an electron beam accelerator cavity utilizing the SRF window assembly is provided. The procedure is carried out within an ultra clean room to minimize exposure to particulates which adversely affect the performance of the cavity within the electron beam accelerator. 11 figs.

  14. Superconducting radiofrequency window assembly

    DOEpatents

    Phillips, H.L.; Elliott, T.S.

    1997-03-11

    The present invention is a superconducting radiofrequency window assembly for use in an electron beam accelerator. The srf window assembly has a superconducting metal-ceramic design. The srf window assembly comprises a superconducting frame, a ceramic plate having a superconducting metallized area, and a superconducting eyelet for sealing plate into frame. The plate is brazed to eyelet which is then electron beam welded to frame. A method for providing a ceramic object mounted in a metal member to withstand cryogenic temperatures is also provided. The method involves a new metallization process for coating a selected area of a ceramic object with a thin film of a superconducting material. Finally, a method for assembling an electron beam accelerator cavity utilizing the srf window assembly is provided. The procedure is carried out within an ultra clean room to minimize exposure to particulates which adversely affect the performance of the cavity within the electron beam accelerator. 11 figs.

  15. Intrinsic left-handed electromagnetic properties in anisotropic superconductors

    NASA Astrophysics Data System (ADS)

    Lin, Shi-Zeng; Chen, Hou-Tong

    2017-04-01

    Left-handed materials usually are realized in artificial subwavelength structures. Here, we show that some anisotropic superconductors such as Bi 2 Sr 2 CaCu 2 O 8 + δ , YBa 2 Cu x O y , and La 2 - x Sr x CuO 4 , are intrinsic left-handed materials. The condition is that the plasma frequency in the c axis, ωc, and in the ab plane, ωab, and the operating angular frequency, ω, satisfy ω c < ω < ω a b . In addition, ω should be smaller than the superconducting energy gap to sustain superconductivity. We study the reflection and transmission of electromagnetic waves and reveal negative refraction and the backward wave with the phase velocity opposite to the direction of energy flux propagation. We also discuss possible approaches for improvement, making these properties feasible for experimental validation. Being intrinsic left-hand materials, the anisotropic superconductors are promising for applications in functional electromagnetic devices in the terahertz frequency band.

  16. High Temperature Superconducting Materials Database

    National Institute of Standards and Technology Data Gateway

    SRD 149 NIST High Temperature Superconducting Materials Database (Web, free access)   The NIST High Temperature Superconducting Materials Database (WebHTS) provides evaluated thermal, mechanical, and superconducting property data for oxides and other nonconventional superconductors.

  17. Optical trapping of anisotropic nanocylinder

    NASA Astrophysics Data System (ADS)

    Bareil, Paul B.; Sheng, Yunlong

    2013-09-01

    The T-matrix method with the Vector Spherical Wave Function (VSWF) expansions represents some difficulties for computing optical scattering of anisotropic particles. As the divergence of the electric field is nonzero in the anisotropic medium and the VSWFs do not satisfy the anisotropic wave equations one questioned whether the VSWFs are still a suitable basis in the anisotropic medium. We made a systematic and careful review on the vector basis functions and the VSWFs. We found that a field vector in Euclidean space can be decomposed to triplet vectors {L, M, N}, which as non-coplanar. Especially, the vector L is designed to represent non-zero divergence component of the vector solution, so that the VSWF basis is sufficiently general to represent the solutions of the anisotropic wave equation. The mathematical proof can be that when the anisotropic wave equations is solved in the Fourier space, the solution is expanded in the basis of the plan waves with angular spectrum amplitude distributions. The plane waves constitute an orthogonal and complete set for the anisotropic solutions. Furthermore, the plane waves are expanded into the VSWF basis. These two-step expansions are equivalent to the one-step direct expansion of the anisotropic solution to the VSWF basis. We used direct VSWF expansion, along with the point-matching method in the T-matrix, and applied the boundary condition to the normal components displacement field in order to compute the stress and the related forces and torques and to show the mechanism of the optical trap of the anisotropic nano-cylinders.

  18. Cryogenfree superconducting magnets

    NASA Astrophysics Data System (ADS)

    Watanabe, Kazuo; Awaji, Satoshi; Motokawa, Mitsuhiro

    2003-05-01

    Various kinds of cryogenfree superconducting magnets such as a wide bore 8 T, a split-pair 5 T, and a high magnetic field 15 T magnet have been developed successfully at Tohoku University. A cryogenfree 23 T hybrid magnet composed of a cryocooled outer superconducting magnet and a water-cooled inner resistive magnet is being tested for the first time. Further, new construction projects of a cryogenfree 30 T hybrid magnet and a cryogenfree 19 T superconducting magnet have just started.

  19. Superconducting energy recovery linacs

    DOE PAGES

    Ben-Zvi, Ilan

    2016-09-01

    High-average-power and high-brightness electron beams from a combination of laser photocathode electron guns and a superconducting energy recovery linac (ERL) is an emerging accelerator science with applications in ERL light sources, high repetition rate free electron lasers , electron cooling, electron ion colliders and more. This paper reviews the accelerator physics issues of superconducting ERLs, discusses major subsystems and provides a few examples of superconducting ERLs.

  20. Superconducting energy recovery linacs

    NASA Astrophysics Data System (ADS)

    Ben-Zvi, Ilan

    2016-10-01

    High-average-power and high-brightness electron beams from a combination of laser photocathode electron guns and a superconducting energy recovery linac (ERL) is an emerging accelerator science with applications in ERL light sources, high repetition rate free electron lasers , electron cooling, electron ion colliders and more. This paper reviews the accelerator physics issues of superconducting ERLs, discusses major subsystems and provides a few examples of superconducting ERLs.

  1. Temperature and Magnetic Field Dependence of Critical Current Density of YBCO with Varying Flux Pinning Additions (POSTPRINT)

    DTIC Science & Technology

    2010-03-01

    compared to YBCO. Index Terms—Critical current density, engineering current den- sity, flux pinning, high temperature superconductor , nanoparticle...I. INTRODUCTION T HE development of high temperature superconductor (YBCO or 123) thin films on polycrys- talline substrates (coated...conductors) with a critical current density offers great promise for incorpo- ration into power applications such as generators or motors , operating at 40–77

  2. Superconductive imaging surface magnetometer

    DOEpatents

    Overton, Jr., William C.; van Hulsteyn, David B.; Flynn, Edward R.

    1991-01-01

    An improved pick-up coil system for use with Superconducting Quantum Interference Device gradiometers and magnetometers involving the use of superconducting plates near conventional pick-up coil arrangements to provide imaging of nearby dipole sources and to deflect environmental magnetic noise away from the pick-up coils. This allows the practice of gradiometry and magnetometry in magnetically unshielded environments. One embodiment uses a hemispherically shaped superconducting plate with interior pick-up coils, allowing brain wave measurements to be made on human patients. another embodiment using flat superconducting plates could be used in non-destructive evaluation of materials.

  3. Vortex cores and vortex motion in superconductors with anisotropic Fermi surfaces

    NASA Astrophysics Data System (ADS)

    Galvis, J. A.; Herrera, E.; Guillamón, I.; Vieira, S.; Suderow, H.

    2017-02-01

    Explaning static and dynamic properties of the vortex lattice in anisotropic superconductors requires a careful characterization of vortex cores. The vortex core contains Andreev bound states whose spatial extension depends on the anisotropy of the electronic band-structure and superconducting gap. This might have an impact on the anisotropy of the superconducting properties and on vortex dynamics. Here we briefly summarize basic concepts to understand anisotropic vortex cores and review vortex core imaging experiments. We further discuss moving vortex lattices and the influence of vortex core shape in vortex motion. We find vortex motion in highly tilted magnetic fields. We associate vortex motion to the vortex entry barrier and the screening currents at the surface. We find preferential vortex motion along the main axis of the vortex lattice. After travelling integers of the intervortex distance, we find that vortices move more slowly due to the washboard potential of the vortex lattice.

  4. Crystallinity of YBCO thin films on an MgO substrate using an amorphous buffer layer deposited at a low temperature

    NASA Astrophysics Data System (ADS)

    Nakamura, Y.; Kudo, S.; Mukaida, M.; Ohshima, S.

    2002-10-01

    We have investigated crystallinity of YBCO films on an MgO substrate using an amorphous buffer layer. The evaluated films are obtained as follows: an amorphous YBCO buffer layer is deposited on the MgO substrate at a low temperature (200 °C); and then, an amorphous buffer layer is crystallized by the thermal annealing at a high temperature from 910 to 1030 °C; finally, main YBCO film is grown on the crystalline YBCO buffer layer over the MgO substrate. A significant improvement in the crystalline quality of the YBCO films was achieved, when amorphous buffer layers of 100 nm in thickness were crystallized by annealing temperature 950 °C and then annealing is continued for 1 h in air atmosphere. We confirmed that YBCO films grown on a well-crystallized buffer layer had better crystallinity than ones on bare MgO substrate, which has substantially large lattice mismatch.

  5. Phase competition in trisected superconducting dome

    NASA Astrophysics Data System (ADS)

    Vishik, Inna

    2012-02-01

    The momentum-resolved nature of angle-resolved photoemission spectroscopy (ARPES) has made it a key probe of emergent phases in the cuprates, such as superconductivity and the pseudogap, which have anisotropic momentum-space structure. ARPES can be used to infer the origin of spectral gaps from their distinct phenomenology---temperature, doping, and momentum dependence, and this principle has been used to argue that the pseudogap is a distinct phase from superconductivity, rather than a precursor [1]. We have studied Bi2Sr2CaCu2O8+δ (Bi-2212) using laser-ARPES, and our data give evidence for three distinct quantum phases comprising the superconducting ground state, accompanied by abrupt changes at p˜0.076 and p˜0.19 in the doping-and-temperature dependence of the gaps near the bond-diagonal (nodal) direction [2]. The latter doping likely marks the quantum critical point of the pseudogap, while the former represents a distinct competing phase at the edge of the superconducting dome. Additionally, we find that the pseudogap advances closer towards the node when superconductivity is weak, just below Tc or at low doping, and retreats towards the antinode well below Tc and at higher doping. This phase competition picture together with the two critical doping are synthesized into our proposed phase diagram, which also reconciles conflicting phase diagrams commonly used in the field. Our results underscore the importance of quantum critical phenomena to cuprate superconductivity, provide a microscopic picture of phase competition in momentum space, and predict the existence of phase boundaries inside the superconducting dome which are different from simple extrapolations from outside the dome. [4pt] [1] I. M. Vishik, W. S. Lee, R.-H. He, M. Hashimoto, Z. Hussain, T. P. Devereaux, and Z.-X. Shen. New J. Phys. 12, 105008 (2010). [0pt] [2] I. M. Vishik, M. Hashimoto, R.-H. He, W. S. Lee, F. Schmitt, D. H. Lu, R.G. Moore, C. Zhang, W. Meevasana, T. Sasagawa, S. Uchida, K

  6. Effect of inductors to mitigate the hot-spot problem in parallel-connected superconducting thin-film fault current limiting elements

    NASA Astrophysics Data System (ADS)

    Yamasaki, H.; Furuse, M.; Kaiho, K.

    2015-06-01

    We have been developing superconducting thin-film fault current limiter (FCL) elements, in which high-resistivity Au-Ag alloy shunt layers are used to protect YBa2Cu3O7 (YBCO) thin films deposited on CeO2-buffered sapphire substrates. The high resistance of the thin films enables the element to withstand high electric fields of more than 40 Vpeak cm-1 during the current-limiting period after quenching, thus greatly reducing the amount of YBCO thin film needed and, consequently, the cost of an FCL. We have succeeded in fabricating and testing 500 V/200 A FCL modules using two 20 cm long YBCO films connected in parallel. In the present study, we performed extensive switching experiments on FCL elements, in which two YBCO films are connected in parallel to achieve higher rated currents, and confirmed the previously observed phenomenon that the hot-spot problem causing film damage just after quench initiation becomes more severe when the total critical current of the thin films is higher. We have investigated the origin of this phenomenon and found that a rapid current transfer from the first-quenched film with lower critical current to the other film causes higher current in the secondly-quenched film that sometimes leads to hot spots. It is demonstrated that the serious hot-spot problem can be mitigated by the use of inductors when the high-resistance FCL elements are connected in parallel. Based on these findings we propose an appropriate architecture of a high electric-field superconducting thin-film FCL that can be used in a real power grid.

  7. A novel induction motor starting method using superconduction

    NASA Astrophysics Data System (ADS)

    Silva, F. B. B.; Orlando, M. T. D.; Fardin, J. F.; Simonetti, D. S.; Baldan, C. A.

    2014-12-01

    In this paper, an alternative method for starting up induction motors is proposed, taking into account experimental measurements. The new starting current limitation method is based on using a high-temperature superconductor. A prototype of the superconducting starting current limiter was constructed with a commercially available second-generation high-temperature superconductor YBCO tape, and this was tested with a 55-kW industrial induction motor in a 440-V/60-Hz three-phase power grid. Performance evaluations of the superconducting limiter method (applied to startup of the induction motor) were performed and were compared with a direct-on-line starter and an electronic soft starter. In addition, a computational model was developed and used for electromagnetic torque analysis of the system. As significant characteristics, our method offers the ability to limit the starting current of the induction motor with greater electromagnetic torque, reduced current waveform distortion and therefore lower harmonic pollution during startup when compared to the soft starter method.

  8. Composite ceramic superconducting wires for electric motor applications

    NASA Astrophysics Data System (ADS)

    Halloran, John W.

    1990-07-01

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

  9. Vortex dynamics in anisotropic traps

    SciTech Connect

    McEndoo, S.; Busch, Th.

    2010-07-15

    We investigate the dynamics of linear vortex lattices in anisotropic traps in two dimensions and show that the interplay between the rotation and the anisotropy leads to a rich but highly regular dynamics.

  10. Cracking on anisotropic neutron stars

    NASA Astrophysics Data System (ADS)

    Setiawan, A. M.; Sulaksono, A.

    2017-07-01

    We study the effect of cracking of a local anisotropic neutron star (NS) due to small density fluctuations. It is assumed that the neutron star core consists of leptons, nucleons and hyperons. The relativistic mean field model is used to describe the core of equation of state (EOS). For the crust, we use the EOS introduced by Miyatsu et al. [1]. Furthermore, two models are used to describe pressure anisotropic in neutron star matter. One is proposed by Doneva-Yazadjiev (DY) [2] and the other is proposed by Herrera-Barreto (HB) [3]. The anisotropic parameter of DY and HB models are adjusted in order the predicted maximum mass compatible to the mass of PSR J1614-2230 [4] and PSR J0348+0432 [5]. We have found that cracking can potentially present in the region close to the neutron star surface. The instability due cracking is quite sensitive to the NS mass and anisotropic parameter used.

  11. Superconductivity in aromatic hydrocarbons

    NASA Astrophysics Data System (ADS)

    Kubozono, Yoshihiro; Goto, Hidenori; Jabuchi, Taihei; Yokoya, Takayoshi; Kambe, Takashi; Sakai, Yusuke; Izumi, Masanari; Zheng, Lu; Hamao, Shino; Nguyen, Huyen L. T.; Sakata, Masafumi; Kagayama, Tomoko; Shimizu, Katsuya

    2015-07-01

    'Aromatic hydrocarbon' implies an organic molecule that satisfies the (4n + 2) π-electron rule and consists of benzene rings. Doping solid aromatic hydrocarbons with metals provides the superconductivity. The first discovery of such superconductivity was made for K-doped picene (Kxpicene, five benzene rings). Its superconducting transition temperatures (Tc's) were 7 and 18 K. Recently, we found a new superconducting Kxpicene phase with a Tc as high as 14 K, so we now know that Kxpicene possesses multiple superconducting phases. Besides Kxpicene, we discovered new superconductors such as Rbxpicene and Caxpicene. A most serious problem is that the shielding fraction is ⩽15% for Kxpicene and Rbxpicene, and it is often ∼1% for other superconductors. Such low shielding fractions have made it difficult to determine the crystal structures of superconducting phases. Nevertheless, many research groups have expended a great deal of effort to make high quality hydrocarbon superconductors in the five years since the discovery of hydrocarbon superconductivity. At the present stage, superconductivity is observed in certain metal-doped aromatic hydrocarbons (picene, phenanthrene and dibenzopentacene), but the shielding fraction remains stubbornly low. The highest priority research area is to prepare aromatic superconductors with a high superconducting volume-fraction. Despite these difficulties, aromatic superconductivity is still a core research target and presents interesting and potentially breakthrough challenges, such as the positive pressure dependence of Tc that is clearly observed in some phases of aromatic hydrocarbon superconductors, suggesting behavior not explained by the standard BCS picture of superconductivity. In this article, we describe the present status of this research field, and discuss its future prospects.

  12. Actuation performances of anisotropic gels

    NASA Astrophysics Data System (ADS)

    Nardinocchi, P.; Teresi, L.

    2016-12-01

    We investigated the actuation performances of anisotropic gels driven by mechanical and chemical stimuli, in terms of both deformation processes and stroke-curves, and distinguished between the fast response of gels before diffusion starts and the asymptotic response attained at the steady state. We also showed as the range of forces that an anisotropic hydrogel can exert when constrained is especially wide; indeed, changing fiber orientation allows us to induce shear as well as transversely isotropic extensions.

  13. Aqueous Chemical Solution Deposition of Novel, Thick and Dense Lattice-Matched Single Buffer Layers Suitable for YBCO Coated Conductors: Preparation and Characterization

    PubMed Central

    Narayanan, Vyshnavi; Van Steenberge, Sigelinde; Lommens, Petra; Van Driessche, Isabel

    2012-01-01

    In this work we present the preparation and characterization of cerium doped lanthanum zirconate (LCZO) films and non-stoichiometric lanthanum zirconate (LZO) buffer layers on metallic Ni-5% W substrates using chemical solution deposition (CSD), starting from aqueous precursor solutions. La2Zr2O7 films doped with varying percentages of Ce at constant La concentration (La0.5CexZr1−xOy) were prepared as well as non-stoichiometric La0.5+xZr0.5−xOy buffer layers with different percentages of La and Zr ratios. The variation in the composition of these thin films enables the creation of novel buffer layers with tailored lattice parameters. This leads to different lattice mismatches with the YBa2Cu3O7−x (YBCO) superconducting layer on top and with the buffer layers or substrate underneath. This possibility of minimized lattice mismatch should allow the use of one single buffer layer instead of the current complicated buffer architectures such as Ni-(5% W)/LZO/LZO/CeO2. Here, single, crack-free LCZO and non-stoichiometric LZO layers with thicknesses of up to 140 nm could be obtained in one single CSD step. The crystallinity and microstructure of these layers were studied by XRD, and SEM and the effective buffer layer action was studied using XPS depth profiling.

  14. Anisotropic assembly and pattern formation

    NASA Astrophysics Data System (ADS)

    von Brecht, James H.; Uminsky, David T.

    2017-01-01

    We investigate the role of anisotropy in two classes of individual-based models for self-organization, collective behavior and self-assembly. We accomplish this via first-order dynamical systems of pairwise interacting particles that incorporate anisotropic interactions. At a continuum level, these models represent the natural anisotropic variants of the well-known aggregation equation. We leverage this framework to analyze the impact of anisotropic effects upon the self-assembly of co-dimension one equilibrium structures, such as micelles and vesicles. Our analytical results reveal the regularizing effect of anisotropy, and isolate the contexts in which anisotropic effects are necessary to achieve dynamical stability of co-dimension one structures. Our results therefore place theoretical limits on when anisotropic effects can be safely neglected. We also explore whether anisotropic effects suffice to induce pattern formation in such particle systems. We conclude with brief numerical studies that highlight various aspects of the models we introduce, elucidate their phase structure and partially validate the analysis we provide.

  15. Microstructure of YBCO thin films prepared by TFA-MOD method

    NASA Astrophysics Data System (ADS)

    Nagino, I.; Matsumoto, K.; Adachi, H.; Miyata, S.; Yoshizumi, M.; Izumi, T.; Shiohara, Y.

    2010-11-01

    The microstructure of the recently developed coated conductors was investigated by using electron back scatter diffraction pattern (EBSP). We prepared TFA (trifluoroacetates)-MOD (metal organic deposition) derived YBa2Cu3O7-x (YBCO) films on CeO2/LaMnO3/IBAD-MgO/Gd2Zr2O7/Hastelloy C276 substrates of 1 cm-width. The EBSP observation showed that there was a difference of surface microstructure between the midsection and the end of TFA-MOD YBCO film layer in the direction of width. This is attributed not to the local difference of the biaxial texture of CeO2 top layer but to the local difference of growth condition during TFA-MOD process.

  16. Theoretical analysis of a YBCO squirrel-cage type induction motor based on an equivalent circuit

    NASA Astrophysics Data System (ADS)

    Morita, G.; Nakamura, T.; Muta, I.

    2006-06-01

    A HTS induction motor, with a HTS squirrel-cage rotor, is analysed using an electrical equivalent circuit. The squirrel-cage winding in the rotor consists of rotor bars and end rings, and both are considered to be made of YBCO film conductors. A wide range of electric field versus current density in YBCO film is formulated based on the Weibull function, and analysed as a non-linear resistance in the equivalent circuit. It is shown that starting and accelerating torques of the HTS induction motor are improved drastically compared to those of a conventional induction motor. Furthermore, large synchronous torque can also be realized by trapping the magnetic flux in the rotor circuit because of the persistent current mode.

  17. The Effects of Grain Boundaries on the Current Transport Properties in YBCO-Coated Conductors.

    PubMed

    Yang, Chao; Xia, Yudong; Xue, Yan; Zhang, Fei; Tao, Bowan; Xiong, Jie

    2015-12-01

    We report a detailed study of the grain orientations and grain boundary (GB) networks in Y2O3 films grown on Ni-5 at.%W substrates. Electron back scatter diffraction (EBSD) exhibited different GB misorientation angle distributions, strongly decided by Y2O3 films with different textures. The subsequent yttria-stabilized zirconia (YSZ) barrier and CeO2 cap layer were deposited on Y2O3 layers by radio frequency sputtering, and YBa2Cu3O7-δ (YBCO) films were deposited by pulsed laser deposition. For explicating the effects of the grain boundaries on the current carry capacity of YBCO films, a percolation model was proposed to calculate the critical current density (J c) which depended on different GB misorientation angle distributions. The significantly higher J c for the sample with sharper texture is believed to be attributed to improved GB misorientation angle distributions.

  18. Feasibility of large-current capacity YBCO conductors with on-demand transposition

    NASA Astrophysics Data System (ADS)

    Yanagi, Nagato; Mito, Toshiyuki; Noguchi, Hiroki; Terazaki, Yoshiro; Tamura, Hitoshi; Iwakuma, Masataka; Aoki, Yuji; Izumi, Teruo; Shiohara, Yuh

    We propose a new idea for fabricating a large-current capacity YBCO conductor having a Roebel-type transposition formed by joining tapes. If the joule heating generated by joints is smaller than other heat sources, such as AC losses, this type of conductor may work as a quasi-superconductor. We note that the Roebel-type transposition can be included on demand in coil windings, not over the whole conductor length but rather locally, such as at terminals and coil edges to secure uniform current distribution among tapes. We fabricated a 1.2 m-long conductor sample based on this idea using 20 YBCO tapes. The Roebel-assembled tapes having joints with a 600-mm pitch length for meandering were imbedded in a copper jacket and soldered. The sample was tested in liquid nitrogen under the self magnetic field and the critical current was measured. The joint resistance was evaluated and compared with the expected value.

  19. Superconducting gyroscope research

    NASA Technical Reports Server (NTRS)

    Hendricks, J. B.; Karr, G. R.

    1985-01-01

    Four basic areas of research and development of superconducting gyroscopes are studied. Chapter 1 studies the analysis of a SQUID readout for a superconducting gyroscope. Chapter 2 studies the dependence of spin-up torque on channel and gas properties. Chapter 3 studies the theory of super fluid plug operation. And chapter 4 studies the gyro rotor and housing manufacture.

  20. Superconducting properties of protactinium.

    PubMed

    Smith, J L; Spirlet, J C; Müller, W

    1979-07-13

    The superconducting transition temperature and upper critical magnetic field of protactinium were measured by alternating-current susceptibility techniques. Since the superconducting behavior of protactinium is affected by its 5f electron character, it is clear now that protactinium is a true actinide element.