186 Matching Results

Search Results

Advanced search parameters have been applied.

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

Description: 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.
Date: December 31, 1996
Creator: Goyal, A.; Norton, D.P. & Paranthaman, M.
Partner: UNT Libraries Government Documents Department


Description: Niobium coatings on copper cavities have been considered as a cost-efficient replacement of bulk niobium RF cavities, however, coatings made by magnetron sputtering have not quite lived up to high expectations due to Q-slope and other issues. High power impulse magnetron sputtering (HIPIMS) is a promising emerging coatings technology which combines magnetron sputtering with a pulsed power approach. The magnetron is turned into a metal plasma source by using very high peak power density of ~ 1 kW/cm{sup 2}. In this contribution, the cavity coatings concept with HIPIMS is explained. A system with two cylindrical, movable magnetrons was set up with custom magnetrons small enough to be inserted into 1.3 GHz cavities. Preliminary data on niobium HIPIMS plasma and the resulting coatings are presented. The HIPIMS approach has the potential to be extended to film systems beyond niobium, including other superconducting materials and/or multilayer systems.
Date: July 24, 2011
Creator: High Current Electronics Institute, Tomsk, Russia; Anders, Andre; Mendelsberg, Rueben J.; Lim, Sunnie; Mentink, Matthijs; Slack, Jonathan L. et al.
Partner: UNT Libraries Government Documents Department

Engineered microstructures and transport properties in YBCO coated conductors.

Description: Each process used to deposit or make the bi-axially textured template, buffer layer(s), and the superconductor in a coated conductor creates interfaces along which defects or interfacial reactions may result. These defects can be additive and propagate through the entire film structure to affect the growth and properties of the superconducting film. Defects within the films and their corresponding transport properties have been correlated with the differences in the thickness of the underlying buffer layer material. This knowledge can be used to control and engineer the structure of the coated conductor to maximize critical current densities.
Date: January 1, 2001
Creator: Holesinger, Terry G.; Gibbons, Brady J.; Coulter, James Y.; Foltyn, Stephen R. & Arendt, Paul N.
Partner: UNT Libraries Government Documents Department

Microstructural development and control in YBa[sub 2]Cu[sub 3]O[sub y]

Description: A study of some defect structures in Y{sub 1}Ba{sub 2}Cu{sub 3}O{sub 7} (Y-123)coated conductors based on ion-beam -assisted-deposition (IBAD) of yttria-stabilized zirconia (YSZ) on nickel alloy substrates is presented. Defect structures can originate anywhere in the coated conductor architecture. Defects can be additive and propagate through the entire film structure to affect the growth, orientation, arid properties of the superconducting film. Interfacial Ieactions between Y- 123 and the underlying buffer layer and the corresponding effects on the transport properticis of the films can be controlled with the thickness of the underlying buffer layer. With a 9Ow ceria buffer layer on an IBAD YSZ coated metal substrate, a J, value of 1.7 MA/cm{sup 2} (self-field, 75K) was obtained in a 1.5{micro}m thick Y-123 film.
Date: January 1, 2001
Creator: Holesinger, T. G. (Terry G.); Gibbons, B. J. (Brady J.); Foltyn, S. R. (Stephen R.); Arendt, P. N. (Paul N.); Groves, J. R. (James R.) & Coulter, J. Y. (James Y.)
Partner: UNT Libraries Government Documents Department

Relationships between processing temperature and microstructure in isothermal melt processed Bi-2212 thick films

Description: The microstructure and phase assemblage of isothermal melt processed (IMP) Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub y} (Bi-2212) thick films have been evaluated. Results from compositional analysis and phase identification indicate that the characteristics of the partial melt greatly influence the microstructural and chemical development of the thick films. The highest critical current densities were obtained in films processed below 800{degrees}C where the partial melt uniformly coats the substrate without excessive phase segregation.
Date: May 1, 1995
Creator: Holesinger, T.G.; Phillips, D.S.; Willis, J.O. & Peterson, D.E.
Partner: UNT Libraries Government Documents Department

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

Description: We report the synthesis and properties of high-J{sub c}, biaxially aligned YBCO films deposited on thermo-mechanically textured Ni tapes. Sharply cube-textured Ni tapes, 125 {mu}m thick, were produced by mechanical rolling followed by recrystallization anneal. Short segments were coated with epitaxial oxide buffer layers, followed by fully aligned YBCO films to thicknesses of 1 to 3 {mu}m. In-plane textures of 7-10{degree} FWHM are achieved, with c-perpendicular alignment to 1{degree} FWHM. Typical zero-field J{sub c} values are in the range 5-9x10{sup 5} A/cm{sup 2} at 77 K, with strong behavior in magnetic fields comparable to that of epitaxial films on single crystal oxides. Assessment of properties necessary for a tape conductor technology are discussed.
Date: March 1, 1997
Creator: Christen, D.K.; Norton, D.P. & Goyal, A.
Partner: UNT Libraries Government Documents Department

Superconductive articles including cerium oxide layer

Description: A ceramic superconductor comprising a metal oxide substrate, a ceramic high temperature superconductive material, and a intermediate layer of a material having a cubic crystal structure, said layer situated between the substrate and the superconductive material is provided, and a structure for supporting a ceramic superconducting material is provided, said structure comprising a metal oxide substrate, and a layer situated over the surface of the substrate to substantially inhibit interdiffusion between the substrate and a ceramic superconducting material deposited upon said structure.
Date: December 1991
Creator: Wu, X. D. & Muenchausen, R. E.
Partner: UNT Libraries Government Documents Department

Superconductive articles

Description: An article of manufacture including a substrate, a patterned interlayer of magnesium oxide, barium-titanium oxide or barium-zirconium oxide, the patterned interlayer material overcoated with a secondary interlayer material of yttria-stabilized zirconia or magnesium-aluminum oxide, upon the surface of the substrate whereby an intermediate article with an exposed surface of both the overcoated patterned interlayer and the substrate is formed, a coating of a buffer layer selected from the group consisting of oxides of Ce, Y, Cm, Dy, Er, Eu, Fe, Gd, Ho, In, La, Mn, Lu, Nd, Pr, Pu, Sm, Tb, Tl, Tm, Y, and Yb over the entire exposed surface of the intermediate article, and, a ceramic superconductive material layer as an overcoat upon the buffer layer whereby the ceramic superconductive material situated directly above the substrate has a crystal structure substantially different than the ceramic superconductive material situated above the overcoated patterned interlayer.
Date: December 1991
Creator: Wu, X. D. & Muenchausen, R. E.
Partner: UNT Libraries Government Documents Department

Free-standing superconductive articles

Description: A substrate-free, free-standing epitaxially oriented superconductive film including a layer of a template material and a layer of a ceramic superconducting material is provided together with a method of making such a substrate-free ceramic superconductive film by coating an etchable material with a template layer, coating the template layer with a layer of a ceramic superconductive material, coating the layer of ceramic superconductive material with a protective material, removing the etchable material by an appropriate means so that the etchable material is separated from a composite structure including the template layer, the ceramic superconductive material layer and the protective material layer, removing the protective material layer from the composite structure whereby a substrate-free, free-standing ceramic superconductive film remains.
Date: December 31, 1991
Creator: Wu, X.D. & Muenchausen, R.E.
Partner: UNT Libraries Government Documents Department

Pulsed laser deposition of thick YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} films on flexible substrates

Description: As an alternative to bulk processing of high-{Tc} materials for conductor applications, we have been studying the applicability of physical vapor deposition to the problem of developing flexible superconducting elements with high I{sub c}. Specifically, we have used a two-step process consisting of ion-assisted sputtering of textured buffer layers on nickel-based substrates, followed by pulsed laser deposition of YBaCu{sub 3}O{sub 7-{delta}} (YBCO) films. The films have been analyzed by measuring the J{sub c} of microbridges, I{sub c} for 1 cm-wide strips, and field dependence up to 9 T. In addition tests have been conducted to determine minimum bending radius of the films.
Date: July 1995
Creator: Foltyn, S. R.; Arendt, P. N. & Wu, X. D.
Partner: UNT Libraries Government Documents Department

Tunneling density of states as a function of thickness in superconductor/ strong ferromagnet bilayers

Description: We have made an experimental study of the tunneling density of states (DOS) in strong ferromagnetic thin films (CoFe) in proximity with a thick superconducting film (Nb) as a function of d{sub F}, the ferromagnetic thickness. Remarkably, we find that as d{sub F} increases, the superconducting DOS exhibits a scaling behavior in which the deviations from the normal-state conductance have a universal shape that decreases exponentially in amplitude with characteristic length d* {approx} 0.4 nm. We do not see oscillations in the DOS as a function of d{sub F}, as expected from predictions based on the Usadel equations, although an oscillation in T{sub c}(d{sub F}) has been seen in the same materials.
Date: April 29, 2010
Creator: Reymond, S.
Partner: UNT Libraries Government Documents Department

Effect of heavy-ion irradiation on transport properties of YBa{sub 2}Cu{sub 3}O{sub x} films

Description: Parallel columnar defects to the c axis and crossed columnar defects were introduced into these films by heavy-ion irradiation with dose equivalent to 1 or 2 T vortex density. The electrical transport properties including resistivity, critical current density, Hall resistivity were measured vs temperature, applied magnetic field, and fluence. The irreversibility line defined as onset of dissipation progressively shifted to higher temperature with dosage and showed its dependence on inclination angle. Critical current also showed a clear enhancement compared to unirradiated samples. The Hall scaling behavior and the Hall conductivity were modified after heavy-ion irradiation.
Date: December 31, 1996
Creator: Kim, D.H.; Shim, S.Y. & Park, J.H.
Partner: UNT Libraries Government Documents Department

Effects of vortex-vortex interactions on ion-track pinning in high T{sub c} superconductors

Description: Many superconductor applications rely on the ability to pin vortex lattices. This ability depends on structural defects to pin individual vortices, but vortex-vortex interactions often play an important role in pinning the other vortices. Experimental progress on this complex problem can be made by introducing random arrays of well-defined pinning centers and studying the flux dynamics for a range of vortex densities (i.e., fields). Results of such studies in epitaxial Tl{sub 2}Ba{sub 2}CaCu{sub 2}O{sub y} films containing ion tracks show the importance of vortex-vortex interactions. As an example, the effective pinning field of the defects rises to many times the ion-dose field for temperatures well below {Tc}.
Date: December 31, 1996
Creator: Gray, K.E.; Steel, D.G. & Hettinger, J.D.
Partner: UNT Libraries Government Documents Department

Fast superconducting magnetic field switch

Description: The superconducting magnetic switch or fast kicker magnet is employed with an electron stream or a bunch of electrons to rapidly change the direction of flow of the electron stream or bunch of electrons. The apparatus employs a beam tube which is coated with a film of superconducting material. The tube is cooled to a temperature below the superconducting transition temperature and is subjected to a constant magnetic field which is produced by an external dc magnet. The magnetic field produced by the dc magnet is less than the critical field for the superconducting material, thus, creating a Meissner Effect condition. A controllable fast electromagnet is used to provide a magnetic field which supplements that of the dc magnet so that when the fast magnet is energized the combined magnetic field is now greater than the critical field and the superconducting material returns to its normal state allowing the magnetic field to penetrate the tube. This produces an internal field which effects the direction of motion and of the electron stream or electron bunch. The switch can also operate as a switching mechanism for charged particles. Magnetic switches and particularly fast kicker magnets are used in the accelerator industry to quickly deflect particle beams into and out of various transport lines, storage rings, dumps, and specifically to differentially route individual bunches of particles from a train of bunches which are injected or ejected from a given ring.
Date: December 31, 1995
Creator: Goren, Y. & Mahale, N.K.
Partner: UNT Libraries Government Documents Department

Low-energy response of superconducting tunnel junction x-ray spectrometers

Description: Thin film structures incorporating metallic superconducting layers and tunnel junctions can be configured as low-energy X-ray spectrometers. We present results obtained when low-energy X-rays are absorbed in niobium films coupled to aluminum layers that serve as quasiparticle traps in an Nb/Al/Al{sub 2}O{sub 3}/Al/Nb tunnel junction X-ray detector. The linearity of the pulse height as a function of energy is discussed along with the energy dependence of the observed resolution and its relation to the broadening mechanisms. A resolution of 14 eV at 1 keV has been measured with our detector cooled to 0.3 K.
Date: December 31, 1994
Creator: Labov, S. E.; Hiller, L. H.; Measrs, C. A.; Frank, M.; Netel, H.; Azgui, F. et al.
Partner: UNT Libraries Government Documents Department

Final report: High current capacity high temperature superconducting film based tape for high field magnets

Description: The primary goal of the program was to establish the process parameters for the continuous deposition of high quality, superconducting YBCO films on one meter lengths of buffered RABiTS tape using MOCVD and to characterize the potential utility of the resulting tapes in high field magnet applications.
Date: January 1, 2000
Creator: Xin, Dr. Ying
Partner: UNT Libraries Government Documents Department


Description: Ex-situ post-deposition reaction processing is considered a promising alternative to in-situ physical vapor deposition techniques for coated Y{sub 1}Ba{sub 2}Cu{sub 3}O{sub 7} conductor development. It was reported recently, that attempts at ex-situ processing of long Y{sub 1}Ba{sub 2}Cu{sub 3}O{sub 7} precursor tapes resulted in an inhomogeneous growth rate over the tape length and rather poor properties for the whole sample. We performed a set of experiments in order to clarify the mechanisms for the ex-situ processing of large area films and estimate properties of long coated conductors manufactured by the ex-situ technique. It was found that rate limiting step of ex-situ growth of Y{sub 1}Ba{sub 2}Cu{sub 3}O{sub 7} is removal of the reaction product, hydrofluoric acid, by both gas diffusion and convection in the reaction atmosphere. We report on a quantitative model that well describes the observed growth rates for films with various areas.
Date: September 18, 2000
Partner: UNT Libraries Government Documents Department

Complex microwave conductivity of YBa{sub 2}Cu{sub 3}O{sub 7} in magnetic fields up to 500T

Description: We have measured the complex conductivity of thin films of YBa{sub 2}cu{sub 3}O{sub 7} (YBCO) superconductor down to temperatures of 4K and magnetic fields up to 500T. The highly oriented films were probed by 94 GHz radiation, with the external magnetic field applied perpendicular to the c-axis. These measurements allowed us to assign a value of 340 {plus_minus} 40 for the upper critical field at T=O. The measurements were recently carried out at the pulsed field facility of the National High Magnetic Field Laboratory at Los Alamos using both Russian and American magnetic flux compression generators.
Date: July 1, 1994
Creator: Goettee, J. D.; Zerwekh, W. D. & Kudasov, Y. B.
Partner: UNT Libraries Government Documents Department

Texture analysis of critical current density in Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub x} tapes

Description: Ag-clad Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub x} tapes were fabricated by a powder-in-tube process. Transport critical current density (J{sub c}) data were obtained at 4.2 K. X-ray diffraction data were used to quantify the texture of each superconductor core. J{sub c} and texture data were related by a geometric model based on J{sub c} anisotropy within individual grains. The model, which fit the data well, is applicable to strongly linked superconductors only.
Date: August 1, 1994
Creator: Biondo, A. C.; Kallend, J. S.; Wu, C. T.; Knapp, W. L.; Lanagan, M. T. & Goretta, K. C.
Partner: UNT Libraries Government Documents Department

Three-terminal devices of high-{Tc} superconductors: A status report and future challenges

Description: A study has been conducted on the recent progress of the three-terminal devices with transistor-like characteristics fabricated from the high-{Tc} superconducting materials. This study explored the operating principles and characteristics of these devices in relation to the relevant materials and techniques. A comparison of a variety of techniques for superconducting thin film deposition will be given. This study indirates that the feasibility of fabricating hybrid devices composed of semiconductors and superconductors appear to be the key issue to push forward the applications of high-{Tc} superconductors in microelectronics. The junction field-effect transistors with a semiconductor base controlled by the proximity effect are likely to be more manufacturable. The factors that influence the operating reliability of devices and the problems arising from integrating and packaging the devices will also be discussed.
Date: October 1, 1992
Creator: Kung, Pang-Jen
Partner: UNT Libraries Government Documents Department

Theory of quantum metal to superconductor transitions in highly conducting systems

Description: We derive the theory of the quantum (zero temperature) superconductor to metal transition in disordered materials when the resistance of the normal metal near criticality is small compared to the quantum of resistivity. This can occur most readily in situations in which 'Anderson's theorem' does not apply. We explicitly study the transition in superconductor-metal composites, in an swave superconducting film in the presence of a magnetic field, and in a low temperature disordered d-wave superconductor. Near the point of the transition, the distribution of the superconducting order parameter is highly inhomogeneous. To describe this situation we employ a procedure which is similar to that introduced by Mott for description of the temperature dependence of the variable range hopping conduction. As the system approaches the point of the transition from the metal to the superconductor, the conductivity of the system diverges, and the Wiedemann-Franz law is violated. In the case of d-wave (or other exotic) superconductors we predict the existence of (at least) two sequential transitions as a function of increasing disorder: a d-wave to s-wave, and then an s-wave to metal transition.
Date: April 6, 2010
Creator: Spivak, B.
Partner: UNT Libraries Government Documents Department