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Sample records for yba2cu3o7 coated conductor

  1. Raman Spectroscopic Studies of YBa2Cu3O7 Coated Conductors

    International Nuclear Information System (INIS)

    Choi, Mi Kyeung; Mnh, Nguyen Van; Bae, J. S.; Jo, William; Yang, In Sang; Ko, Rock Kil; Ha, Hong Soo; Park, Chan

    2005-01-01

    We present results of Raman spectroscopic studies of superconducting YBa 2 Cu 3 O 7 (YBCO) coated conductors. Raman scattering is used to characterize optical phonon modes, oxygen content, c-axis misalignment, and second phases of the YBCO coated conductors at a micro scale. A two-dimensional mapping of Raman spectra with transport properties has been performed to elucidate the effect of local propertied on current path and superconducting phase. The information taken from the local measurement will be useful for optimizing the process condition.

  2. Importance of low-angle grain boundaries in YBa2Cu3O7coated conductors

    International Nuclear Information System (INIS)

    Durrell, J H; Rutter, N A

    2009-01-01

    Over the past ten years the perception of grain boundaries in YBa 2 Cu 3 O 7conductors has changed greatly. They are now not a problem to be eliminated, but an inevitable and potentially favourable part of the material. This change has arisen as a consequence of new manufacturing techniques which result in excellent grain alignment, reducing the spread of grain boundary misorientation angles. At the same time there is considerable recent evidence which indicates that the variation of properties of grain boundaries with mismatch angle is more complex than a simple exponential decrease in critical current. This is due to the fact that low-angle grain boundaries represent a qualitatively different system to high-angle boundaries. The time is therefore right for a targeted review of research into low-angle YBa 2 Cu 3 O 7-δ grain boundaries. This article does not purport to be a comprehensive review of the physics of grain boundaries as found in YBa 2 Cu 3 O 7-δ in general; for a broader overview we would recommend that the reader consult the comprehensive review of Hilgenkamp and Mannhart (2002 Rev. Mod. Phys. 74 485). The purpose of this article is to review the origin and properties of the low-angle grain boundaries found in YBa 2 Cu 3 O 7coated conductors both individually and as a collective system. (topical review)

  3. Tuning Vortex Creep in Irradiated YBa2Cu3O7Coated Conductors

    Science.gov (United States)

    Eley, Serena; Kihlstrom, Karen; Holleis, Sigrid; Leroux, Maxime; Rupich, Martin; Miller, Dean; Kayani, Asghar; Welp, Ulrich; Kwok, Wai-Kwong; Civale, Leonardo

    YBa2Cu3O7coated conductors (CCs) show non-monotonic changes in the temperature-dependent creep rate, S (T) , due to mixed pinning landscapes comprised of twin boundaries, planar defects, point defects, and nanoparticle precipitates. Notably, in low fields, there is a conspicuous dip in S as T increases from ~20K to ~65K. The source of this dip is poorly understood. Moreover, pinning landscapes that are favorable for high critical currents, Jc, are not necessarily optimal for low S. We have found that, though oxygen irradiation introduces few-nm-sized defects that result in significant increases in Jc, it is detrimental to creep, increasing S (reducing the dip depth) for T > 20K. Understanding the source of this dip is crucial to engineering pinning landscapes that concurrently promote high Jc and low S. To this end, we study changes in S (T) as we tune the ratio of smaller (point to few-nm-sized) defects to larger nanoparticles in an oxygen-irradiated CC by annealing in O2 at 250°C to 600°C. We observe a steady decrease in S (T > 20K) with increasing annealing temperature. This suggests that pre-existing nanoparticle precipitates are likely responsible for the dip in S (T) , and underlines the fact that the effects of defects are not additive, but rather can be competitive.

  4. All-chemical YBa2Cu3O7 coated conductors on IBAD-YSZ stainless steel substrates

    International Nuclear Information System (INIS)

    Pomar, A; Cavallaro, A; Coll, M; Gazquez, J; Palau, A; Sandiumenge, F; Puig, T; Obradors, X; Freyhardt, H C

    2006-01-01

    We report on the fabrication of all-chemical YBa 2 Cu 3 O 7 coated conductors on IBAD-YSZ (IBAD stands for ion beam assisted deposition; YSZ is yttrium stabilized zirconia) stainless steel substrates. YBCO films were grown by the trifluoroacetates route on top of CeO 2 buffer layers made by metal-organic decomposition. The achievement of atomically flat CeO 2 surfaces is found to be a key factor for obtaining clean interfaces with YBCO and high performance. Coated conductors with percolative critical currents of J c GB (65 K) = 1.8 MA cm -2 were achieved. The determination of the intra-grain critical current J c G from inductive measurements suggests that the limiting factor for J c GB is the YBCO in-plane texture, which is already of higher quality than that of the IBAD-YSZ cap layer. (rapid communication)

  5. Strategic Research on Performance Optimization of YBa2Cu3O7 Coated Conductors

    International Nuclear Information System (INIS)

    Aytug, Tolga; Christen, David K.; Kim, Kyunghoon; Lupini, Andrew R.; Paranthaman, Mariappan Parans; Polat, Ozgur; Thompson, James R.; Xiong, X.; Selvamanickam, V.; Meyer, Harry M. III; Qiu, Xiaofeng

    2008-01-01

    Practical applications of second generation (2G) high temperature superconductor (HTS) wires require high critical current density, Jc, at high temperatures and magnetic fields. It has been well established that Jc can be increased via nanostructural engineering of artificial pinning centers within the HTS matrix. In the present work, composite LaMnO3:MgO (LMO:MgO) cap buffer layers with varying MgO contents 5 vol% up to 75 vol% have been grown on homo-epi MgO/IBAD(MgO) substrates to enhance the performance of YBa2Cu3O7-x (YBCO) films. Results showed formation of phase separated MgO nanocolumns within the LMO matrix. The impact of these nanocolumns on the superconducting properties of YBCO films deposited on the nanostructured layer was investigated by electrical transport measurements. Such YBCO films showed better in-field performance compared to that of YBCO films on standard LMO cap films. In particular, measurements of the field-angle dependence revealed c-axis correlated pinning for YBCO films on these composite cap layers. The present results demonstrate a practical approach to obtain high performance superconducting wires.

  6. Critical current degradation of short YBa2Cu3O7coated conductor due to an unprotected quench

    International Nuclear Information System (INIS)

    Wang, X; Trociewitz, U P; Schwartz, J

    2011-01-01

    The critical current of a short YBa 2 Cu 3 O 7-δ (YBCO) coated conductor sample degrades in an unprotected quench performed in a nearly adiabatic environment at 30 K. The conductor has Cu stabilizers on both surfaces. The quench is initiated by a heater attached to the sample surface. The amplitude of the transport current is fixed as 91% of the sample's initial critical current. The duration of the current is increased to simulate an unprotected quench and to reach increasing and controlled voltage and temperature levels. A peak temperature of 490 ± 50 K and a heating rate of 1800 K s -1 are measured when the critical current degrades by ∼ 5%. The applied thermal strain on the YBCO layer from 30 to 490 K is estimated to be 0.31% and is applied at a strain rate of ∼ 1% s -1 . The rate of temperature change and the time to reach a certain peak temperature, determined by the current density in the Cu stabilizer, are estimated assuming adiabatic conditions based on the short sample case. For a Cu stabilizer current density ranging from 1000 to 2000 A mm -2 , achieved in commercial conductors currently available, the quench detection and protection requires a response time -2 may challenge the existing detection and protection techniques for the same 200 K limit. Integrating the substrate as part of the stabilizer may help reduce the stabilizer current density to gain more time for quench detection and protection while maintaining the engineering current density.

  7. Investigation and optimization of YBa2Cu3O7-δ grain boundaries and coated conductors

    International Nuclear Information System (INIS)

    Held, Rainer Robert Martin

    2010-01-01

    With increasing misorientation angle grain boundaries strongly reduce the critical current density of high temperature superconductors. For this reason costly techniques are used in production of modern Coated Conductors to induce sharp textures in the polycrystalline superconductor layers. In this dissertation measurements of the critical current density of different grain boundary types are presented showing that out-of-plane grain boundaries exhibit, also in applied magnetic fields, much higher critical current densities than expected. In further analysis of the grain boundaries indications for a microstructural reason of the high critical current densities were found. The high critical current densities of the out-of-plane grain boundaries should in fabrication of Coated Conductors allow for a relaxation of the out-of-plane grain alignment requirements and a concomitant cost reduction. In this work also results of a industrial cooperation with Nexans are presented demonstrating that the critical current density of metal-organic deposited grain boundaries and Coated Conductor layers can be increased by selective Calcium-doping. In the experiments selective Calcium-doping most effectively increased the critical current density of weak spots. (orig.)

  8. Two level undercut-profile substrate for filamentary YBa2Cu3O7 coated conductors

    DEFF Research Database (Denmark)

    Wulff, Anders Christian; Solovyov, M.; Gömöry, Fedor

    2015-01-01

    A novel substrate design is presented for scalable industrial production of filamentary coated conductors (CCs). The new substrate, called ‘two level undercut-profile substrate (2LUPS)’, has two levels of plateaus connected by walls with an undercut profile. The undercuts are made to produce...... a shading effect during subsequent deposition of layers, thereby creating gaps in the superconducting layer deposited on the curved walls between the two levels. It is demonstrated that such 2LUPS-based CCs can be produced in a large-scale production system using standard deposition processes...

  9. Fabrication of High Current YBa2Cu3O7-y Coated Conductors Using Rolling-Assisted Biaxially Textured Substrates

    International Nuclear Information System (INIS)

    Christen, D.K.; Feenstra, R.; Kroeger, D.M.; Lee, D.F.; List, F.A.; Martin, P.M.; Norton, D.P.; Paranthaman, M.; Park, C.; Royal, A.; Specht, E.D.; Verebelyi, D.T.

    1999-01-01

    High critical current YBa 2 Cu 3 O 7-y (referred to as YBCO) coated conductors were fabricated with a layer sequence of YBCO/YSZ/CeO 2 /Ni. The cube (100) texture in the starting Ni substrates was obtained by cold rolling followed by recrystallization. A thin CeO 2 (Cerium Oxide) layer with a thickness of 100-200 was grown epitaxially on the biaxially textured-Ni substrates using an e-beam evaporation technique. This was followed by the growth of a thick ( 2 film had a dense microstructure. The microstructure of the e-beam YSZ film was porous whereas the sputtered YSZ film was dense. The YBCO films were grown by pulsed laser deposition on both e-beam and sputtered YSZ layers. A transport critical current density of 1 x l0 6 A/cm 2 at 77 K was obtained for 0.8 m thick YBCO Rims on both YSZ surfaces in zero field. To demonstrate the quality and compatibility of the e-beam CeO 2 layers; YBCO films were also grown on CeO 2 -buffered YSZ (100) single crystal substrates using e-beam co-evaporated Y-BaF 2 -Cu precursors followed by a post-annealing process. A transport critical current density of over 1 x lO 6 A/cm 2 at 77 K was obtained on a 0.3 m thick YBCO film in zero field

  10. Epitaxial solution deposition of YBa2Cu3O7-6 coated conductors.

    Energy Technology Data Exchange (ETDEWEB)

    Overmyer, Donald L.; Clem, Paul Gilbert; Siegal, Michael P.; Holesinger, Terry A. (Los Alamos National Laboratory, Los Alamos, NM); Voigt, James A.; Richardson, Jacob J.; Dawley, Jeffrey Todd

    2004-11-01

    A variety of solution deposition routes have been reported for processing complex perovskite-based materials such as ferroelectric oxides and conductive electrode oxides, due to ease of incorporating multiple elements, control of chemical stoichiometry, and feasibility for large area deposition. Here, we report an extension of these methods toward long length, epitaxial film solution deposition routes to enable biaxially oriented YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO)-coated conductors for superconducting transmission wires. Recent results are presented detailing an all-solution deposition approach to YBCO-coated conductors with critical current densities J{sub c} (77 K) > 1 MA/cm{sup 2} on rolling-assisted, biaxially textured, (200)-oriented Ni-W alloy tapes. Solution-deposition methods such as this approach and those of other research groups appear to have promise to compete with vapor phase methods for superconductor electrical properties, with potential advantages for large area deposition and low cost/kA {center_dot} m of wire.

  11. Growth of simplified buffer template on flexible metallic substrates for YBa2Cu3O7coated conductors

    International Nuclear Information System (INIS)

    Xue, Yan; Zhang, Ya-Hui; Zhang, Fei; Zhao, Rui-Peng; Wang, Hui; Xiong, Jie; Tao, Bo-Wan

    2016-01-01

    A much simplified buffer structure, including a three-layer stack of LaMnO 3 /MgO/composite Y 2 O 3 –Al 2 O 3 , was proposed for high performance YBa 2 Cu 3 O 7-δ (YBCO) coated conductors. In this structure, biaxially textured MgO films were prepared on solution deposition planarized amorphous substrate through ion-beam-assisted deposition (IBAD) technology. By the use of in situ reflection high-energy electron diffraction monitor, X-ray diffraction and atomic force microscope, the influence of deposition parameters, such as film deposition rate, ion penetrate energy and ion beam flux, on crystalline orientation, texture, lattice parameter and surface morphology was systematically investigated. Moreover, stopping and range of ion in mater simulation was performed to study the effects of ion bombardment on MgO films. By optimizing IBAD process parameters, the best biaxial texture showed ω-scan of (002) MgO and Φ-scan of (220) MgO yield full width at half maximum values of 2.4° and 3.7°, indicating excellent biaxial texture. Subsequently, LaMnO 3 films were directly deposited on the IBAD-MgO template to improve the lattice mismatch between MgO and YBCO. Finally, YBCO films grown on this simplified buffer template exhibited a critical current density of 2.4 MA/cm 2 at 77 K and self-field, demonstrating the feasibility of this buffer structure. - Highlights: • Simplified buffer structure for YBCO coated conductors. • Growth of biaxially textured MgO films on flexible amorphous substrates. • Studying the influence of film deposition rate, ion energy and ion beam flux on the development of biaxial texture. • Demonstrating highly oriented YBCO films with a critical current density of 2.4 MA/cm 2 at self-field and 77 K.

  12. Phase Evolution of YBa2Cu3O7-x films by all-chemical solution deposition route for coated conductors

    DEFF Research Database (Denmark)

    Yue, Zhao; Tang, Xiao; Wu, Wei

    2014-01-01

    In order to understand the all-chemical-solution-deposition (CSD) processes for manufacturing coated conductors, we investigated the phase evolution of YBa2Cu3O7 (YBCO) films deposited by a low-fluorine metal-organic solution deposition (LF-MOD) method on CSD derived Ce0.9La0.1O2/Gd2Zr2O7/Ni......W. It is shown that the phase transition from the pyrolyzed film to fully converted YBCO film in the LF-MOD process is similar to that in typical trifluoroacetates-metal organic deposition (TFA-MOD) processes even though the amount of TFA in the solution is reduced by almost one half compared with typical TFA...

  13. Experimental investigations on the vortex instability and time effects of YBa2Cu3O7−x coated conductors

    International Nuclear Information System (INIS)

    Zhang, Xingyi; Zhou, Jun; Yue, Donghua; Liu, Wei; Zhou, Youhe

    2014-01-01

    Highlights: •Influences of the current sweep rate on the I–V and V–t curves are investigated. •Significant voltages jumps including increase and drop are observed. •With an increase of magnetic field, the maximum voltage increases. -- Abstract: We have investigated the effect of the current sweep rate (CSR) on the vortex dynamic in the YBa 2 Cu 3 O 7–x coated conductors (YBCO CCs). It is found that the CSR has several effects on vortex motion in that it gives rise to enhancement of dissipation as the CSR decreases, significant time effects and instabilities are observed in current–voltage (I–V) and voltage–time (V–t) curves. Thus, the CSR on practical applications of the YBCO CCs can be optimized, and relevant CSR which is designing superconducting devices made by the YBCO CCs should be considered in future

  14. Epitaxial YBa2Cu3O7-x nanocomposite films and coated conductors from BaMO3 (M = Zr, Hf) colloidal solutions

    Science.gov (United States)

    Obradors, X.; Puig, T.; Li, Z.; Pop, C.; Mundet, B.; Chamorro, N.; Vallés, F.; Coll, M.; Ricart, S.; Vallejo, B.; Pino, F.; Palau, A.; Gázquez, J.; Ros, J.; Usoskin, A.

    2018-04-01

    Superconducting nanocomposites are the best material choice to address the performance required in power applications and magnets working under high magnetic fields. However, it is still challenging to sort out how to achieve the highest superconducting performance using attractive and competitive manufacturing processes. Colloidal solutions have been recently developed as a novel and very promising low cost route to manufacture nanocomposite coated conductors. Well dispersed and stabilized preformance nanoparticle solutions are first prepared with high concentrations and then mixed with the YBa2Cu3O7 metalorganic precursor solutions to generate colloidal solutions to grow the nanocomposite films. Here we demonstrate, for the first time, that non-reactive BaZrO3 and BaHfO3 perovskite preformed nanoparticles are suitable for growing high quality thin and thick films, and coated conductors with a homogeneous distribution and controlled particle size using this fabrication method. Additionally, we extend the nanoparticle content of the nanocomposites up to 20%-25% mol without any degradation of the superconducting properties. Thick nanocomposite films, up to 0.8 μm, have been prepared with a single deposition of low-fluorine solutions using an ink jet printing dispenser and we demonstrate that the preformed nanoparticles display only a very limited coarsening during the growth process and so high critical current densities J c (B) under high magnetic fields. These films show the highest critical currents achieved so far based on the colloidal solution approach, I c = 220 A/cm-w at 77 K and self-field, and they still have a high potential for further increase in the film thickness. Finally, we also show that nanocomposite YBa2Cu3O7-BaZrO3 coated conductors based on an alternating beam assisted deposited YSZ buffer layer on stainless steel metallic substrates can be developed based on these novel colloidal solutions. Non-reactive preformed oxide perovskite

  15. Dynamic magneto-optical imaging of transport current redistribution and normal zone propagation in YBa2Cu3O7coated conductor

    International Nuclear Information System (INIS)

    Song Honghai; Schwartz, Justin; Davidson, Michael W

    2009-01-01

    YBa 2 Cu 3 O 7-δ (YBCO) coated conductors carry high critical current density with the potential for low cost and thus have a broad range of potential applications. An unresolved issue that could inhibit implementation, however, is a lack of understanding of the current redistribution and normal zone propagation behavior in the event of a thermal disturbance (quench). In this work, we for the first time present the real-time, dynamic observation of magnetic field redistribution during a thermal disturbance via magneto-optical imaging with a high speed, high resolution CCD (charge coupled device) camera. The optical images are converted to a two-dimensional, time-dependent data set that is then analyzed quantitatively. It is found that the normal zone propagates non-uniformly in two dimensions within the YBCO layer. Two stages of normal zone propagation are observed. During the first stage, the normal zone propagates along the conductor length as the current and magnetic field redistribute within the YBCO layer. During the second stage, current sharing with the Cu begins and the magneto-optical image becomes constant. The normal zone propagation velocity at 45 K, I = 50 A (∼50% I c ), is determined as 22.7 mm s -1 using the time-dependent optical light intensity data. (rapid communication)

  16. Depth profiling of transport properties of in-situ grown YBa_2Cu_3O_7-x films for coated conductor applications

    Science.gov (United States)

    Jo, William; Huh, J.-U.; Hammond, R. H.; Beasley, M. R.

    2003-03-01

    We report depth profiling of the local critical current density and resistivity of YBa_2Cu_3O_7-x (YBCO) films grown by in-situ electron beam evaporation. The method provides important information on the uniformity of the films, and therefore on the commonly observed property that the critical currents of coated conductor high temperature superconductor films do not scale linearly with thickness. Using a methodology of layer-by-layer etching, depth profiling of critical currents and resistivity of the films has been achieved. We use a Bromine methanol mixture to etch down YBCO films with an etch rate of 60 nm/min. At each step, we also observe surface morphology using high resolution scanning electron microscopy. In this talk, we report further study of the results found earlier that YBCO films deposited at high rates are composed of an upper layer of defected YBCO with a local Jc of 5 - 7 MA/cm^2 and a lower more perfect layer with no critical current capacity. The information derived may be useful in the characterization and optimization of superconducting thin films for electrical power and other applications.

  17. Three-dimensional vortex pinning by nano-precipitates in a Sm-doped YBa2Cu3O7-x coated conductor

    International Nuclear Information System (INIS)

    Chen, Z; Feldmann, D M; Song, X; Kim, S I; Gurevich, A; Reeves, J L; Xie, Y Y; Selvamanickam, V; Larbalestier, D C

    2007-01-01

    We report on the thickness and angular dependence of the critical current density J c (H,θ), the irreversibility field H irr , and the bulk pinning force F p (H) of a metal-organic chemical vapour deposition (MOCVD) grown YBa 2 Cu 3 O 7-x (YBCO) coated conductor, which contains ∼17 vol% of ∼10 nm sized (Y,Sm) 2 O 3 precipitates with an average spacing of ∼10-15 nm. Some surface porosity and amorphous second-phase particles on the scale of ∼0.5-1 μm appear to reduce the current-carrying cross-section, which controls the magnitude of J c but not the vortex pinning. We observed an enhanced H irr ∼9 T at 77 K along the c-axis which, like the shape of J c (H) and F p (H), was independent of thickness as the sample was milled down to ∼0.16 μm. Angular-dependent measurements of J c showed the usual excess vortex pinning along the c-axis and along the ab-plane, but with a background that could only be fitted with an unusually small anisotropy parameter of 3, which, like the high H irr and the thickness-independent shape of F p (H), we ascribe to strong vortex pinning centre interactions. Together, these measurements show very different behaviour from most pulsed-laser-deposited films, which exhibit strong thickness-dependent properties. We ascribe the present different results to the dense array of small, insulating precipitates, which act as strong pinning centres and produce strong three-dimensional (3D) vortex pinning, because their separation of 10-15 nm is always much smaller than the film thickness

  18. Uncovering a new quasi-2D CuO2 plane between the YBa2Cu3O7 and CeO2 buffer layer of coated conductors

    Science.gov (United States)

    Li, Zhi-Xin; Cao, Jin-Jin; Gou, Xiao-Fan; Wang, Tian-Ge; Xue, Feng

    2018-01-01

    We report a discovery of the quasi-two-dimensional (quasi-2D) CuO2 plane between the superconductor YBa2Cu3O7 (YBCO) and CeO2 buffer layer (mostly used in the fabrication) of coated conductors through the atomistic computer simulations with the molecular dynamics (MD) and first-principle calculations. For an YBCO coated conductor with multilayer structures, the buffer layers deposited onto a substrate are mainly considered to transfer a strong biaxial texture from the substrate to the YBCO layer. To deeply understand the tuning mechanism of the texture transfer, exploring the complete atomic-level picture of the structure between the YBa2Cu3O7/CeO2 interfaces is firstly required. However, the related observation data have not been available due to some big challenges of experimental techniques. With the MD simulations, having tested the accuracy of the potential functions for the YBa2Cu3O7/CeO2 interface, we constructed a total of 54 possible atom stacking models of the interface and identified its most appropriate and stable structure according to the criterion of the interface adhesion energy and the coherent characterization. To further verify the stability of the identified structure, we performed the first-principle calculations to obtain the adhesion energy and developed the general knowledge of the interface structure. Finally, a coherent interface formed with a new built quasi-2D CuO2 plane that is structurally similar to the CuO2 plane inside bulk YBCO was determined.

  19. Preparation of high critical temperature YBa2Cu3O7 superconducting coatings by thermal spray

    International Nuclear Information System (INIS)

    Lacombe, Jacques

    1991-01-01

    The objective of this research thesis is the elaboration of YBa 2 Cu 3 O 7 superconducting coatings by thermal spray. These coatings must have a high adherence, a high cohesion, and the best possible electrical characteristics. The author first briefly presents physical-chemical characteristics of this ceramic, and proposes a bibliographical synthesis on thick coatings prepared by thermal spray. In the next parts, he studies and describes conditions of elaboration of poly-granular coatings of YBa 2 Cu 3 O 7 , and their structural and electric characteristics [fr

  20. Development of biaxially textured buffer layers on rolled-Ni substrates for high current YBa2Cu3O7-y coated conductors

    International Nuclear Information System (INIS)

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

    1996-01-01

    This paper describes the development of 3 buffer layer architectures with good biaxial textures on rolled-Ni substrates using vacuum processing techniques. The techniques include pulsed laser ablation, e-beam evaporation, dc and rf magnetron sputtering. The first buffer layer architecture consists of an epitaxial laminate of Ag/Pd(Pt)/Ni. The second buffer layer consists of an epitaxial laminate of CeO 2 /Pd/Ni. The third alternative buffer layer architecture consists of an epitaxial laminate of YSZ/CeO 2 /Ni. The cube (100) texture in the Ni was produced by cold rolling followed by recrystallization. Crystallographic orientations of the Pd, Ag, CeO 2 , and YSZ films grown were all (100). We recently demonstrated a critical- current density of 0.73x10 6 A/cm 2 at 77 K and zero field on 1.4 μm thick YBa 2 Cu 3 O 7-y (YBCO) film. This film was deposited by pulsed laser ablation on a YBCO/YSZ/CeO 2 /Ni substrate

  1. Microstructural and superconducting properties of high current metal-organic chemical vapor deposition YBa2Cu3O7coated conductor wires

    International Nuclear Information System (INIS)

    Holesinger, T G; Maiorov, B; Ugurlu, O; Civale, L; Chen, Y; Xiong, X; Xie, Y; Selvamanickam, V

    2009-01-01

    Metal-organic chemical vapor deposition (MOCVD) on flexible, ion beam assisted deposition MgO templates has been used to produce high critical current density (J c ) (Y,Sm) 1 Ba 2 Cu 3 O y (REBCO) films suitable for use in producing practical high temperature superconducting (HTS) coated conductor wires. Thick films on tape were produced with sequential additions of 0.7 μm of REBCO via a reel-to-reel progression through a custom-designed MOCVD reactor. Multi-pass processing for thick film deposition is critically dependent upon minimizing surface secondary phase formation. Critical currents (I c s) of up to 600 A/cm width (t = 2.8 μm, J c = 2.6 MA cm -2 , 77 K, self-field) were obtained in short lengths of HTS wires. These high performance MOCVD films are characterized by closely spaced (Y,Sm) 2 O 3 nanoparticle layers that may be tilted relative to the film normal and REBCO orientation. Small shifts in the angular dependence of J c in low and intermediate applied magnetic fields can be associated with the tilted nanoparticle layers. Also present in these films were YCuO 2 nanoplates aligned with the YBCO matrix (short dimension perpendicular to the film normal), threading dislocations, and oriented composite defects (OCDs). The latter structures consist of single or multiple a-axis oriented grains coated on each side with insulating (Y,Sm) 2 O 3 or CuO. The OCDs formed a connected network of insulating phases by the end of the fourth pass. Subsequent attempts at adding additional layers did not increase I c . There is an inconsistency between the measured J c and the observed microstructural degradation that occurs with each additional layer, suggesting that previously deposited layers are improving with each repeated reactor pass. These dynamic changes suggest a role for post-processing to optimize superconducting properties of as-deposited films, addressing issues associated with reproducibility and manufacturing yield.

  2. The effect of YBa2Cu3O7-x powder characteristics on thick coatings prepared by atmospheric plasma spraying

    International Nuclear Information System (INIS)

    Georgiopoulos, E.; Tsetsekou, A.

    2000-01-01

    The development of superconducting YBa 2 Cu 3 O 7-x plasma sprayed coatings on metal substrates can be very useful for applications such as targets for thin-film deposition techniques (sputtering, laser ablation, ion assisted deposition) or magnetic shielding, due to the brittle nature of bulk superconductors. The plasma spraying technique is very flexible and can be used for manufacturing components with a large variety of geometries. This technique requires the use of powders with good rheological characteristics. In this study, YBa 2 Cu 3 O 7-x powders were produced by using the conventional solid-state reaction route and also by spray drying a solution of nitrate precursors. Both powders, as well as mixtures of them, were plasma sprayed to develop coatings on stainless-steel substrates, with the aim of studying the effect of the feedstock powder characteristics on the coating properties. It was found that by optimizing the plasma spraying conditions, good quality coatings could be obtained. However, the powder morphology and homogeneity significantly affect the coating quality. More homogeneous powders lead to better results, the spray-dried powder being the best because of its enhanced rheological properties and good morphology. (author)

  3. Annealing of electrophoretic YBa2Cu3O7 coatings on polycristaline substrates by zonal laser fusion

    Directory of Open Access Journals (Sweden)

    de la Fuente, G.

    2002-02-01

    Full Text Available Obtaining coatings on metallic substrates of irregular geometries is not easy by traditional methods. In those cases electrochemical methods show important advantages and have been used successfully. To date only silver has shown to be inert with respect to superconducting cuprates, although progress has been made in the development of intermediate buffer layers. However, in the particular case of YBa2Cu3O7 , annealing above the cuprate superconducting melting point to attempt densification or texturing is hard on silver because of the lower melting point of the metal. . Focalized heating of superconducting oxides over metallic substrates, using LASER techniques on controlled geometries, allows densification of coatings. The Laser processed sample may be amorphous but the crystallinity is easily recovered, as well as the optimal oxygen content for the oxide, but the preferential orientation induced by the electrophoretic deposition is lost upon the recrystallization process occurring over polycrystaline substrates.La realización de depósitos de óxidos superconductores sobre substratos metálicos de geometría compleja y en general policristalinos está prácticamente basada en métodos electroforéticos o electroquímicos que permiten la utilización de un campo eléctrico de geometría definida para inducir el movimiento de partículas de óxido o de precursores de éste, hacia el electrodo elegido. Dichos métodos son fundamentales cuando el substrato es metálico o puede hacerse metálico con facilidad. Hasta el presente tan sólo la plata ha mostrado ser lo suficientemente inerte para permitir recocidos posteriores, aunque se está progresando en el desarrollo de capas “buffer”. Sin embargo, cuando el óxido depositado es YBa2Cu3O7 , el proceso de recocido posterior no permite la obtención de textura sobre Ag mediante métodos térmicos dado el inferior punto de fusión de este metal. El presente trabajo presenta un estudio de fusi

  4. Three dimensional analyses of flux pinning centers in Dy-doped YBa2Cu3O7-x coated superconductors by STEM tomography

    International Nuclear Information System (INIS)

    Ortalan, V.; Herrera, M.; Rupich, M.W.; Browning, N.D.

    2009-01-01

    In order to enhance the superconductive properties of the high temperature superconductors, nanoparticles acting as pinning centers can be intentionally introduced into the structure by chemical doping. In this study, a Dy-doped YBa 2 Cu 3 O 7-x (YBCO) coated conductor, prepared by a metal organic decomposition process, was investigated to determine the size, composition and 3D distribution of the nanoparticles. It was found that the addition of Dy results in the formation of a high density of secondary phase nanoparticles of composition (Y s Dy 1-s ) 2 Cu 2 O 5 with s ∼ 0.6. A tomographic tilt series was acquired by using a scanning transmission electron microscope to analyze the interaction between the particles and the structural defects and to determine the 3D distribution of nanoparticles. For the investigated sample volume (0.06 μm 3 ), 71 particles were located with a particle size distribution ranging between 13 and 135 nm with an average size of ∼30 nm. The distribution uniformity, position and the size of the particles are observed to be dependent on the interaction of the particles with the twin boundaries. It is observed that the larger particles are generally located on more than one twin boundary, moreover, the particle size is smaller on the twin boundaries shared by several particles. This suggests that the growth of the particles is determined by fast twin boundary diffusion and the formation of the large particles might be prevented by altering the temperature-time parameters of the production processing to enhance the flux pinning characteristic of the superconductors by achieving a more uniform size of flux pinning centers.

  5. Chemically deposed layer sytems for the realization of YBa2Cu3O7-δ band conductors

    International Nuclear Information System (INIS)

    Engel, Sebastian

    2009-01-01

    The aim of this thesis was to produce new buffer-layer systems for biaxially texturated Ni5at%W substrates by means of chemical processes. As very promising materials for the buffer layers CaTiO 3 and SrTiO 3 were chosen. The production of the single layers pursued from the organometallic prestage by means of dip coating and subsequent head treatment. During the work first the single precursor solutions were to be developed. A main component of the theses forms the understanding of the texture development during the heat treatment of precursor layers on biaxially texturated metallic substrates. Based on this the growth of thick buffer layers is studied and by means of YBCO layers, which were deposed by beans of a pulsed laser, the functionality of the synthesized buffer layers proved. A further component of this thesis formes the influence of nanoscaling precipitations in thew YBCO on its superconducting properties. The YBCO deposition pursued via a variation of the TFA process, as substrate (001)-oriented SrTiO 3 monocrystals were applied

  6. Studies on Ba(2)YNbO(6) Buffer Layers for Subsequent YBa(2)Cu(3)O(7-x) Film Growth

    National Research Council Canada - National Science Library

    Sathiraju, Srinivas; Barnes, Paul N; Varanasi, Chakrapani; Wheeler, Robert

    2004-01-01

    In this paper, we are reporting a dielectric oxide buffer Ba(2)YNbO(6) (BYNO) and its performance on various substrates for a potential buffer layer for the growth of YBa(2)Cu(3)O(7-x) (YBCO) coated conductors. Ba(2)YNbO(6...

  7. Rapid processing method for solution deposited YBa2Cu3O7-δ thin films

    International Nuclear Information System (INIS)

    Dawley, J.T.; Clem, P.G.; Boyle, T.J.; Ottley, L.M.; Overmyer, D.L.; Siegal, M.P.

    2004-01-01

    YBa 2 Cu 3 O 7-δ (YBCO) films, deposited on buffered metal substrates, are the primary candidate for second-generation superconducting (SC) wires, with applications including expanded power grid transmission capability, compact motors, and enhanced sensitivity magnetic resonance imaging. Feasibility of manufacturing such superconducting wires is dependent on high processing speed, often a limitation of vapor and solution-based YBCO deposition processes. In this work, YBCO films were fabricated via a new diethanolamine-modified trifluoroacetic film solution deposition method. Modifying the copper chemistry of the YBCO precursor solution with diethanolamine enables a hundredfold decrease in the organic pyrolysis time required for MA/cm 2 current density (J c ) YBCO films, from multiple hours to ∼20 s in atmospheric pressure air. High quality, ∼0.2 μm thick YBCO films with J c (77 K) values ≥2 MA/cm 2 at 77 K are routinely crystallized from these rapidly pyrolyzed films deposited on LaAlO 3 . This process has also enabled J c (77 K)=1.1 MA/cm 2 YBCO films via 90 m/h dip-coating on Oak Ridge National Laboratory RABiTS textured metal tape substrates. This new YBCO solution deposition method suggests a route toward inexpensive and commercializable ∼$10/kA m solution deposited YBCO coated conductor wires

  8. Solution processing of YBa2Cu3O7-x thin films

    International Nuclear Information System (INIS)

    Singhal, A.; Paranthaman, M.; Specht, E.D.; Hunt, R.D.; Beach, D.B.; Martin, P.M.; Lee, D.F.

    1997-12-01

    The aim of this work was to develop a non-vacuum chemical deposition technique for YBa 2 Cu 3 O 7-x (YBCO) coated conductors on rolling-assisted biaxially textured substrates (RABiTS). The authors have chosen the metal-organic decomposition (MOD) and sol-gel precursor routes to grow textured YBCO films. In the MOD process, yttrium 2-ethylhexonate, barium neodecanoate, copper 2-ethylhexonate and toluene were used as the starting reagents. YBCO films processed by the MOD method on SrTiO 3 (100) single crystal substrates were consisted of c and a-axis oriented materials. These films also contained some amount of the random phase. The c and a-axis oriented materials were epitaxial on SrTiO 3 substrates. Films have a T c,onset of 89K and the best superconducting transition temperature of 63K. Films pyrolyzed at 525 C and subsequently annealed at 780 C in a p(O 2 ) of 3.5 x 10 -4 atm contained YBCO phase predominantly in a-axis orientation. In the sol-gel route, yttrium-isopropoxide, barium metal, copper methoxide and 2-methoxyethanol were used as the starting reagents. Sol-gel YBCO films on SrTiO 3 substrates were epitaxial and c-axis oriented

  9. Densification of YBa2Cu3O7-x

    International Nuclear Information System (INIS)

    Zhou, J.P.; Sorrell, C.C.; Dou, S.X.; Liu, H.K.; Bourdillon, A.J.

    1991-01-01

    YBa 2 Cu 3 O 7-x is normally densified by solid-state reaction at 935deg-980deg C for 2-4 h in air or at 940deg-1000deg C for 5-10 h in flowing oxygen. Typical densities achieved these ways are 70-80% of theoretical. Rahaman et al. obtained 95% density by rapidly inserting samples in a furnace at 800deg C. Densities of 94-100% can be achieved by sinter-forging, hot pressing, and hot isostatic pressing. The present work reports a rapid sintering technique whereby 100% density can be achieved without the use of specialised equipment

  10. Rheology of YBa2Cu3O7-x precursors

    International Nuclear Information System (INIS)

    Green, T.M.; Akinc, M.

    1992-01-01

    Nitrate and acetate precursors to YBa 2 Cu 3 O 7-x (123) are prepared using a molten salt technique. The viscosity and shear stress of the paste are controlled by evaporation of water from the paste. The pastes contain ∼ 20--80 vol % solids. Rheometry over strain rates of 0--200 sec -1 shows both systems are shear-thinning. Both systems are thixotropic. The nitrate system may be described by a two-stage Bingham Plastic model, the acetate by a Hershel-Bulkley model. The existence of more than one region of flow behavior suggests that there are at least two mechanisms which contribute to flow. In the low strain rate region, flow resistance is due to the existence of flocs in the colloidal assembly. At higher strain rates, flow is probably controlled by interlaminar drag interactions. Precursors produced by both methods have been used to form fibers of YBa 2 Cu 3 o 7-x , by ram extrusion

  11. Microcracking in polycrystalline YBa2Cu3O7

    International Nuclear Information System (INIS)

    Smith, D.S.; Suasmoro, S.; Huger, M.; Gault, C.

    1991-01-01

    The presence of microcracks can have a significant role for the electrical properties of polycrystalline YBa 2 Cu 3 O 7-δ due to the reduction of the effective current carrying cross section. This results in an increase of the normal state resistivity and a decrease of the critical current density, j c . Shaw et.al have reported an onset of microcracking for grain sizes greater than 1-2 μm. In this work we focus attention on the geometrical aspects of the microstructure by using ultrasonic measurements to characterize the mechanical properties of the ceramic for comparison to the electrical data. The studies have been extended with experiments as a function of temperature and atmosphere in order to investigate the origins of the microcracks. (orig./BHO)

  12. On the Fermi surface of YBa2Cu3O7

    International Nuclear Information System (INIS)

    Peter, M.; Manuel, A.A.; Hoffmann, L.; Sadowski, W.

    1992-01-01

    We show that the signature of a Fermi surface sheet of YBa 2 Cu 3 O 7-δ may be obtained unambiguously from twinned crystals. Comparison of electron-positron momentum density from YBa 2 Cu 3 O 7-δ measured both in insulating and (superconducting) twinned phases leads to a decisive further proof of the existence of the Fermi surface in the metallic YBa 2 Cu 3 O 7-δ . In addition, measurements on untwinned YBA 2 Cu 3 O 7-δ single crystals reveal also a ridge Fermi surface sheet attributed by band structure calculations to CuO chains. 14 refs., 3 figs

  13. Junction structures based on the high-Tc superconductor YBa2Cu3O7

    International Nuclear Information System (INIS)

    Gijs, M.A.M.

    1993-01-01

    An overview is given of the investigations of the Josephson effect in junction structures based on the high-T c superconductor YBa 2 Cu 3 O 7-δ , which were carried out at the Philips Research Laboratories in Eindhoven in the 1988-1990 period. The reported results are presented in their international scientific context, without attempting a complete review of the subject. However, the various junction types studied give a good idea of the scientific pursuits of high-T c junction researchers in this period. The following junctions are considered: in the category of 'weak link'-type junctions we have investigated YBa 2 Cu 3 O 7-δ -Ag-Nb point contact junctions, YBa 2 Cu 3 O 7-δ Dayem bridges and YBa 2 Cu 3 O 7-δ -Ag(-Al)-Pb proximity junctions. In these structures we combine a high-T c with a low-T c superconductor. We also fabricated planar 'all high-T c ' YBa 2 Cu 3 O 7-δ -Ag-YBa 2 Cu 3 O 7-δ junctions using a submicron structuring process. Next we have made tunnel junctions to study density of states effects of the high-T c superconductor : YBa 2 Cu 3 O 7-δ -Pb junctions using the degraded YBa 2 Cu 3 O 7-δ -Pb interface as a tunnel barrier, and YBa 2 Cu 3 O 7-δ -Ag-Al/Al 2 O 3 /Pb tunnel junctions based on the superconducting proximity effect. Our junction structures are electrically characterized and mostly studied in microwave and magnetic fields. Results are compared with current theoretical models. (orig.)

  14. Characterization and crystal defects of the new YBa2Cu3O7-x superconductor

    International Nuclear Information System (INIS)

    Boulesteix, C.; Ben Salem, M.; Mokrani, R.

    1987-01-01

    YBa 2 Cu 3 O 7-x superconductors from different origins have been studied by electron microscopy and X ray emission. This material has an easy clevage plane parallel to (001) making its observation easy. It has been shown that the preparation reaction was not complete for some superconducting materials. YBa 2 Cu 3 O 7-x crystals can be twinned (mechanical twins, ferroelastic material) but they are generally not, or have few twins. Another oxide has been encountered in epitaxial growth on YBa 2 Cu 3 O 7-x . A superlattice perpendicular to the common c axis has been observed probably due to a regular stacking of the both oxides [fr

  15. The effects of H+ implants on YBa2Cu3O7 superconducting materials

    International Nuclear Information System (INIS)

    Luo Chenglin; Pan Guoqiang; Han Ming; Wang Guanghou

    1993-09-01

    The variations of microstructure and electrical properties of Y-Ba-Cu O with and without H + implantation have been studied by scanning electron microscope, X-ray diffraction and IR spectrum techniques. The results have shown that these variations are directly relative to the intrinsic quality of YBa 2 Cu 3 O 7 . Microstructural change is responsible for the variations of electrical properties of YBa 2 Cu 3 O 7 superconductor. The Cu H bond formed by H + implanted into YBa 2 Cu 3 O 7 is not a key factor for these variations

  16. Current-limiting mechanisms in YBa2Cu3O7-δ thin layers and quasi-multilayers

    International Nuclear Information System (INIS)

    Haenisch, J.

    2004-01-01

    In this work, electrical transport properties and the maximum current carrying capability of YBa 2 Cu 3 O 7 -[δ] thin films and so called quasi-multilayers are investigated. These samples are prepared with pulsed laser deposition on single-crystalline substrates (SrTiO 3 ) as well as on biaxially textured Ni tapes. The critical current density of coated conductors is limited by small-angle grain boundaries in low magnetic fields, but by the intra-grain pinning properties in higher magnetic fields. Accordingly, these investigations are divided into two parts: In the first part, the limitation of the critical current density by grain-boundaries and grain boundary networks is investigated with the main focus on the influence of geometrical factors such as the conductor width or the grain aspect ratio. In the second part, a possible enhancement of the critical current density due to different doping types (atomar doping using Zn and precipitate doping using BaMO 3 where M is a transition metal) will be discussed. Here, not only the irreversibility field but also the pinning behaviour in very low magnetic fields is of interest to better understand the pinning mechanism of thin films. (Orig.)

  17. Electrical transport in (103) YBa2Cu3O7-x thin films

    International Nuclear Information System (INIS)

    Divin, Yu.Ya.; Poppe, U.; Faley, M.I.; Soltner, H.; Seo, J.W.; Kabius, B.; Urban, K.

    1993-01-01

    We have studied the electrical and structural properties of (103) YBa 2 Cu 3 O 7-x thin films to estimate the applicability of these films as base electrodes of planar-type Josephson junctions. (orig.)

  18. Resintering - a novel approach for preparing massive YBa2Cu3O7-δ-ceramics

    International Nuclear Information System (INIS)

    Vuong, N.V.; Raspopina, E.V.

    1996-01-01

    The resintering procedure of YBa 2 Cu 3 O 7-δ -ceramics in 3BaCuO 2 + 2CuO eutectic melt for preparing massive samples is presented. The resintered ceramics is of the single orthorhombic phase YBa 2 Cu 3 O 7-δ and has the volume fraction of the intergrain region reduced from 50 to 5%. The average grain size is twofold increased, the connection between grains is appreciably strengthened. (author). 12 refs., 10 figs., 1 tab

  19. Improving chemical solution deposited YBa 2Cu 3O 7- δ film properties via high heating rates

    Science.gov (United States)

    Siegal, M. P.; Dawley, J. T.; Clem, P. G.; Overmyer, D. L.

    2003-12-01

    The superconducting and structural properties of YBa 2Cu 3O 7- δ (YBCO) films grown from chemical solution deposited (CSD) metallofluoride-based precursors improve by using high heating rates to the desired growth temperature. This is due to avoiding the nucleation of undesirable a-axis grains at lower temperatures, from 650 to 800 °C in p(O 2)=0.1%. Minimizing time spent in this range during the temperature ramp of the ex situ growth process depresses a-axis grain growth in favor of the desired c-axis orientation. Using optimized conditions, this results in high-quality YBCO films on LaAlO 3(1 0 0) with Jc(77 K) ∼ 3 MA/cm 2 for films thicknesses ranging from 60 to 140 nm. In particular, there is a dramatic decrease in a-axis grains in coated-conductors grown on CSD Nb-doped SrTiO 3(1 0 0) buffered Ni(1 0 0) tapes.

  20. Raman scattering studies of YBa2Cu3O7-x thin films grown by chemical vapor deposition and metal-organic deposition

    International Nuclear Information System (INIS)

    Lee, E.; Yoon, S.; Um, Y.M.; Jo, W.; Seo, C.W.; Cheong, H.; Kim, B.J.; Lee, H.G.; Hong, G.W.

    2007-01-01

    We present results of Raman scattering studies of superconducting YBa 2 Cu 3 O 7-x (YBCO) films grown by chemical vapor deposition and metal-organic deposition methods. It is shown by X-ray diffraction that all the as-grown YBCO films have a highly c-axis oriented and in-plane aligned texture. Raman scattering measurements were used to investigate optical phonon modes, oxygen contents, structural properties, and second-phases of the YBCO coated conductors. Raman spectra of YBCO films with lower-transport qualities exhibit additional phonon modes at ∼300 cm -1 , ∼600 cm -1 , and ∼630 cm -1 , which are related to second-phases such as Ba 2 Cu 3 O 5.9 and BaCuO 2 . Our results strongly suggest that Raman scattering be useful for optimizing YBCO film growth conditions

  1. YBa2Cu3O7-δ/NdBa2(Cu1-xNix)3O7-δ double layers by liquid-phase epitaxial growth

    International Nuclear Information System (INIS)

    Yao, X.; Izumi, Toru; Hobara, Natsuro; Nakamura, Yuichi; Izumi, Teruo; Shiohara, Yuh

    2001-01-01

    Our present investigation has answered questions pertaining to the REBa 2 Cu 3 O 7-δ (RE123, RE=rare-earth elements)-coated conductor application when NdBa 2 (Cu 1-x Ni x ) 3 O 7-δ (Ni-NdBCO) solid solution is used as a buffer layer by the liquid-phase epitaxy(LPE) process. The NiO/Ni substrate has no substantial reaction in the Ni-saturated Nd-Ba-Cu-O liquid. There is no essential Ni interdiffusion between YBa 2 Cu 3 O 7-δ (YBCO) and Ni-NdBCO LPE thick films as evident from T c values of 90 K obtained from multilayer YBCO/Ni-NdBCO samples. (author)

  2. Electrical characterization of chemically modified YBa2Cu3O7-x surfaces

    International Nuclear Information System (INIS)

    Hunt, B.D.; Foote, M.C.; Vasquez, R.P.

    1990-01-01

    Results on electrical characterization of YBa 2 Cu 3 O 7-x thin-film surfaces treated with a Br/ethanol chemical etch are presented. Electrical measurements of YBa 2 Cu 3 O 7-x /Au/Nb device structures fabricated using polycrystalline, post-annealed YBa 2 Cu 3 O 7-x films with Br-etched surfaces, show improvements of approximately one or two orders of magnitude in current densities and resistivities (resistance-area products) relative to unetched devices. The existence of supercurrents in these structures has been confirmed by observation of the ac Josephson effect, and by magnetic field and temperature studies of the critical currents. The Br-etch process has produced 10x10 μm 2 devices with critical current densities greater than 400 A/cm 2 and resistivities as low as 4x10 -7 Ω cm 2

  3. Low resistivity contacts to YBa2Cu3O(7-x) superconductors

    Science.gov (United States)

    Hsi, Chi-Shiung; Haertling, Gene H.

    1991-01-01

    Silver, gold, platinum, and palladium metals were investigated as electroding materials for the YBa2Cu3O(7-x) superconductors. Painting, embedding, and melting techniques were used to apply the electrodes. Contact resistivities were determined by: (1) type of electrode; (2) firing conditions; and (3) application method. Electrodes fired for long times exhibited lower contact resistivities than those fired for short times. Low-resistivity contacts were found for silver and gold electrodes. Silver, which made good ohmic contact to the YBa2Cu3O(7-x) superconductor with low contact resistivities was found to be the best electroding material among the materials evaluated in this investigation.

  4. Thermal transport in layered structure of YBa2Cu3O7-δ superconductors

    Science.gov (United States)

    Sharma, Rakhi; Indu, B. D.

    2017-12-01

    The heat transfer study in YBa2Cu3O7-δ superconductors structures is focused on the influence of the effect of scattering events in cross-plane and in-plane references. Understanding the mechanism of controlling the thermal conductivity of layered superconductors is an area of interest for nano microelectronics and thermo-electronic technological applications. The model of the thermal conduction, and phonon transport perpendicular and parallel to the layers of YBa2Cu3O7-δ are developed. It has been justified via numerical estimation and found substantial diminution in thermal conductivities in both in-plane and cross-plane directions of layered cuprate superconductors.

  5. Detecting properties of thin film superconducting bridges made of YBa2Cu3O7-x

    International Nuclear Information System (INIS)

    Kulikov, V.A.; Matveets, L.V.; Serebryakov, A.Yu.; Laptev, V.N.; Makhov, V.I.; Emel'yanenkov, D.G.; Inkin, Yu.N.

    1989-01-01

    Results of study of detecting properties of thin film YBa 2 Cu 3 O 7-x bridges, subjected to the effect of 8 mm SHF-radiation are presented. The transition temperatures of bridges were equal to 80-85 K. Current-voltage characteristics and response dependences of bridges with 67, 150 and 425 Ω resistances were measured. It is shown that thin film bridges of YBa 2 Cu 3 O 7-x , representing the system of weak bonds, demonstrate nonstationary Josephson effect and synchronization of weak bonds in bridge volume

  6. Epitaxial YBa2Cu3O7-δ/Sr2RuO4 heterostructures

    International Nuclear Information System (INIS)

    Schlom, D.G.; Merritt, B.A.; Madhavan, S.

    1997-01-01

    The anisotropic oxide superconductors YBa 2 Cu 3 O 7-δ and Sr 2 RuO 4 have been epitaxially combined in various ways (c-axis on c-axis, c-axis on a-axis, and a-axis on a-axis) though the use of appropriate substrates. Phase-pure a-axis oriented or c-axis oriented epitaxial Sr 2 RuO 4 films were grown by pulsed laser deposition. YBa 2 Cu 3 O 7-δ films were then grown on both orientations of Sr 2 RuO 4 films and the resulting epitaxy was characterized

  7. YBa2Cu3O7 films prepared by aerosol MOCVD

    International Nuclear Information System (INIS)

    Weiss, F.; Froehlich, K.; Haase, R.; Labeau, M.; Selbmann, D.; Senateur, J.P.; Thomas, O.

    1993-01-01

    In the present study we report on properties of YBa 2 Cu 3 O 7 films prepared by aerosol MOCVD. We give a short description of the process and we focus on the superconducting and related properties of the films deposited on SrTiO 3 , LaAlO 3 and NdGaO 3 single crystalline substrates. (orig.)

  8. Anisotropic electrical properties of superconducting single crystals YBa2 Cu3 O7-x

    International Nuclear Information System (INIS)

    Konczykowski, M.; Rullier-Albenque, F.

    1988-01-01

    The effect of the hydrostatic pressure (up to 18 kbar) on the transport properties of YBa 2 Cu 3 O 7 single crystals was investigated. A decrease of the resistivity and of its anisotropy was observed under pressure whereas an increase of the critical temperature, of the upper critical field and of its slope vs temperature variation was found

  9. Peak effect in untwinned YBa 2Cu 3O 7-δ single crystals

    Science.gov (United States)

    D'Anna, G.; André, M.-O.; Indenbom, M. V.; Benoit, W.

    1994-12-01

    We report on the observation of a weak effect of the critical current density in untwinned YBa 2Cu 3O 7-δ single crystals of different purity, using a low frequency torsion pendulum. We construct the peak effect line and the irreversibility line.

  10. Critical current through grain boundary of metal oxide superconductors YBa2Cu3O7

    International Nuclear Information System (INIS)

    Ermolov, S.N.; Kislov, N.A.; Marchenko, V.A.

    1989-01-01

    Josephson junction with characteristics, corresponding to sandwich type structure is produced at 78 K at the link of large YBa 2 Cu 3 O 7-δ crystallite with fine-grain structure. J c (H) dependence on the thermomagnetic prehistory is explained with regard to scattering fields of magnetic flux captured by grains

  11. Polarized neutron determination of the magnetic excitations in YBa2Cu3O7

    DEFF Research Database (Denmark)

    Mook, H.A.; Yethiraj, M.; Aeppli, G.

    1993-01-01

    Polarization analysis has been used to identify the magnetic excitations in YBa2Cu3O7. The dominant feature in the spectra is a peak at the (pi,pi) reciprocal lattice position and centered at 41 meV. The behavior of the peak is shown to change dramatically at T(c), so that the magnetic excitations...

  12. Anomalous misfit strain relaxation in ultrathin YBa2Cu3O7-δ epitaxial films

    International Nuclear Information System (INIS)

    Kamigaki, K.; Terauchi, H.; Terashima, T.; Bando, Y.; Iijima, K.; Yamamoto, K.; Hirata, K.; Hayashi, K.; Nakagawa, I.; Tomii, Y.

    1991-01-01

    Ultrathin YBa 2 Cu 3 O 7-δ epitaxial films were successfully grown in situ on (001) SrTiO 3 and MgO substrates by means of ozone-incorporating activated reactive evaporation. The x-ray-diffraction study was carefully examined to determine the structural properties of the grown films. Excellent crystallinity with no interfacial disorders was revealed by the appearance of the Laue oscillations. It was found that in a well lattice-matched YBa 2 Cu 3 O 7-δ /SrTiO 3 system, the crystallinity was deteriorated due to defect introduction at the critical layer thickness h c ( ∼ 130 A). Interestingly, also in a poorly lattice-matched YBa 2 Cu 3 O 7-δ /MgO system, excellent crystallinity was revealed even at above h c ( 2 Cu 3 O 7-δ /MgO system. In such a system, no crystal imperfection of the MgO substrate caused by defect introduction was elucidated by the grazing incidence x-ray scattering, which indicated that the MgO substrate did not contribute to the anomalous misfit relaxation. The anomalous growth manner was also found in YBa 2 Cu 3 O 7-δ /MgO according to surface morphology investigations. Below 40 A( > h c ), island nucleation growth was found. Above 40 A, it was observed that an atomically smooth surface was obtained and the crystallinity was simultaneously improved. It is suggested that YBa 2 Cu 3 O 7-δ possesses an anomalous misfit relaxation mechanism, and that especially in the growth on MgO, it couples with the characteristic growth behavior at the initial stage

  13. Structural and pinning properties of Y2Ba4CuMOy (M = Nb,Zr)/YBa2Cu3O7-δ quasi-multilayers fabricated by off-axis pulsed laser deposition

    International Nuclear Information System (INIS)

    Reich, E; Thersleff, T; Huehne, R; Iida, K; Schultz, L; Holzapfel, B

    2009-01-01

    Power applications based on YBa 2 Cu 3 O 7coated conductors demand an enhancement of the critical current density J c in magnetic fields to be achieved using artificial pinning centres. A well-known approach to studying pinning by second phase nanoparticles is based on quasi-multilayer deposition of YBa 2 Cu 3 O 7-δ (Y123) and a dopant material. In this study we use the Y 2 Ba 4 CuMO y (M = Nb, Zr; M2411) phase as a dopant material, which proved to be very successful in increasing J c for bulk samples. Although stability of the M2411 phase in bulk Y123 has been reported, experimental evidence of its stability in thin films is still lacking. We found that during the quasi-multilayer deposition, yttrium doped Ba(M 1-x Y x )O 3 forms instead of the M2411 secondary phase, and this causes an increase of J c at high magnetic fields as well as an increase in the irreversibility field below 80 K as compared against pure Y123 thin films.

  14. Penetration depth of YBa2Cu3O7 measured by polarised neutron reflectometry

    International Nuclear Information System (INIS)

    Reynolds, J.M.; Nunez, V.; Boothroyd, A.T.; Bucknall, D.G.; Penfold, J.

    1998-01-01

    We have applied the technique of polarised neutron reflectometry (PNR) to investigate the magnetic field profile near the surface of YBa 2 Cu 3 O 7 films at 4.3 K. The samples comprised 700-1400 nm of c-axis oriented, single crystal YBa 2 Cu 3 O 7 deposited by laser ablation on SrTiO 3 substrates. The measurements were carried out on the CRISP reflectometer at the ISIS facility. The PNR technique measures the magnetic induction profile perpendicular to the surface, and so in our case the decay of flux in the c-direction was measured with a field applied parallel to the ab plane. We present preliminary data for the polarised and unpolarised reflectivity (orig.)

  15. Photolithographically patterened thin-film multilayer devices of YBa2Cu3O7-x

    International Nuclear Information System (INIS)

    Kingston, J.J.; Wellstood, F.C.; Quan, D.; Clarke, J.

    1990-09-01

    We have fabricated thin-film YBa 2 Cu 3 O 7-x -SrTiO 3 -YBa 2 Cu 3 O 7-x multilayer interconnect structures in which each in situ laser-deposited film is independently patterned by photolithography. In particular, we have constructed the two key components necessary for a superconducting multilayer interconnect technology, crossovers and window contacts. As a further demonstration of the technology, we have fabricated a thin-film flux transformer, suitable for use with a Superconducting QUantum Interference Device (SQUID), that includes a ten-turn input coil with 6μm linewidth. Transport measurements showed that the critical temperature was 87K and the critical current was 135 μA at 82K. 7 refs., 6 figs

  16. Spectroscopic study of the CuO chains in YBa2Cu3O7-x

    International Nuclear Information System (INIS)

    Edwards, H.; Derro, D.J.; Barr, A.L.; Markert, J.T.; de Lozanne, A.L.

    1996-01-01

    We interpret our previously published results obtained using a technique called current-imaging tunneling spectroscopy (CITS) to study the detailed electronic structure of the CuO chains in the high-temperature superconductor YBa 2 Cu 3 O 7-x near the Fermi level. Our CITS data comprise sequences of 32 simultaneously obtained images taken at bias voltages ranging from -78 to 72 mV. Cross sections of the CITS data, normalized-conductance analysis, and logarithmic-derivative analysis allow us to examine in detail the behavior of electronic modulations along the CuO chains and the energy gap in the CuO chains of YBa 2 Cu 3 O 7-x . This new analysis lends a strong foundation to our previous interpretation of the CITS data [H. L. Edwards et al., Phys. Rev. Lett. 75, 1387 (1995)]. copyright 1996 American Vacuum Society

  17. Role of thermal analysis in the study of superconductor YBa2Cu3O7

    International Nuclear Information System (INIS)

    Virkar, A.N.

    1993-01-01

    The interstitial oxygen atoms along the b-axis of the orthorhombic unit cell of superconducting phase of YBa 2 Cu 3 O 7 form a chain of Cu-O-Cu-O located in the perovskite basal plane and these chains are interpreted to be responsible for superconductivity. Superconductivity can be strongly suppressed by introducing oxygen defects into the chain sites. The characteristic chain structure disappears in the non-superconducting tetragonal phase. Thus orthorhombic to tetragonal transformation takes place by an order-disorder transition between filled and vacant oxygen sites in the basal plane which results in the loss of superconductivity in oxygen deficient YBa 2 Cu 3 O 7-δ phase. (author). 12 refs., 8 figs

  18. Specific heat of single crystalline YBa2Cu3O7 in 20 Tesla

    International Nuclear Information System (INIS)

    Junod, A.; Bonjour, E.; Calemczuk, R.; Henry, J.Y.; Muller, J.; Triscone, G.; Vallier, J.C.

    1994-01-01

    The specific heat of a single crystal of YBa 2 Cu 3 O 7 is measured from 40 to 150 K in magnetic fields up to 20 Tesla applied either parallel or normal to the c axis. Adiabatic calorimetry with a scatter well below 0.1% is used. The scaling of the superconducting transitions determines the bulk anisotropy ratio, 5.5±0.5. A Maki-like term is observed at intermediate temperatures. The unusual behaviour of YBa 2 Cu 3 O 7 in a field, featuring a considerable smearing of the transition and an apparently field-independent onset, may be qualitatively understood as a phenomenological consequence of the small and anisotropic value of the coherence length alone, using the relevant models of field-induced critical 1-D fluctuations on one hand, and London-like regime for the mean-field part of the transition on the other hand. (orig.)

  19. Physical and chemical properties of YBa2Cu3O7 thin films

    International Nuclear Information System (INIS)

    El-Samahi, M.I.

    1991-12-01

    Investigations were carried out to determine the influence of different annealing processes on the superconducting properties of the YBa 2 Cu 3 O 7 thin films. The samples were produced by means of coevaporation of Cu, Y and Ba on polycrystalline yttria stabilized (YSZ) ZrO 2 and single crystal SrTiO 3 (001) substrates. Subsequently, the as-deposited films were subjected to two different annealing methods to crystallize the superconducting phase YBa 2 Cu 3 O 7 : (i) heating up, annealing and cooling in an oxygen atmosphere and (ii) heating up in an innert gas atmosphere up to the maximum annealing temperature (T max ) and then annealing and cooling under oxygen. (orig.)

  20. High resolution electron microscopy and electron diffraction of YBa2Cu3O(7-x)

    International Nuclear Information System (INIS)

    Krakow, W.; Shaw, T.M.

    1988-01-01

    Experimental high resolution electron micrographs and computer simulation experiments have been used to evaluate the visibility of the atomic constituents of YBa 2 Cu 3 O(7-x). In practice, the detection of oxygen has not been possible in contradiction to that predicted by modelling of perfect crystalline material. Preliminary computer experiments of the electron diffraction patterns when oxygen vacancies are introduced on the Cu-O sheets separating Ba layers show the diffuse streaks characteristic of short range ordering. 7 references

  1. YBa2Cu3O(7-x) based superconducting thin films by multitarget sputtering

    International Nuclear Information System (INIS)

    Bouteloup, E.; Mercey, B.; Poullain, G.; Brousse, T.; Murray, H.; Raveau, B.

    1990-01-01

    This paper reports a new technique to prepare superconducting YBa 2 Cu 3 O (7-x) thin films. The multitarget sputtering apparatus described below allows the simultaneous and reproducible production of numerous films with a metallic composition close to Y 17% Ba 33% Cu 50% . Superconducting films (R = 0) at 80 K have been produced on polycrystalline zirconia substrates after a high temperature annealing [fr

  2. Subharmonic gap structure in the characteristics of YBa2Cu3O7-x microbridges

    International Nuclear Information System (INIS)

    Pogrebnyakov, A.V.; Levinsen, M.T.; Sheng, Y.Q.; Freltoft, T.

    1996-01-01

    The subharmonic gap structures corresponding to large, 2Δ 1 =48 meV, and small, 2Δ 2 =10.3 meV, components of the energy gap were observed in the first derivatives of the current-voltage characteristics of YBa 2 Cu 3 O 7-x epitaxial thin film microbridges. The appearance of the subharmonic gap structures is attributed to Andreev reflection. (orig.)

  3. Integration of gas phase condensed nanoparticles in YBa_2Cu_3O_7_-_δ multilayers

    International Nuclear Information System (INIS)

    Sparing, Maria

    2012-01-01

    The control and targeted variation of nanoparticles properties is a central challenge in research on particle induced defects in YBa_2Cu_3O_7_-_δ. Using a combined Sputter-PLD system with inert gas condensation particle size and density integrated into the YBCO multilayers were varied independently. The cooling process influences the electrical properties of the multilayers. The effect of HfO2 and FePt nanoparticles on the structural and electrical properties was studied.

  4. Positron implantation studies of YBa2Cu3O7-x

    International Nuclear Information System (INIS)

    Anwand, W.; Brauer, G.; Coleman, P.G.; Knights, A.P.; Teske, K.; Schuster, G.; Rudolph, K.

    1995-01-01

    Slow positron implantation spectroscopy has been applied to the study of a set of samples of superconducting YBa 2 Cu 3 O 7-x . The depth-sensitive positron response to oxygen content and preparation history is presented. An outline is given of the experimental method - solid electrolyte coulometry in carrier-gas mode - used to measure oxygen exchange for the same set of samples. (orig.)

  5. Positron annihilation in thermally quenched YBa2Cu3O7-x

    International Nuclear Information System (INIS)

    Hong Zhang; Xiao-Gang Wang; Yao-Xian Fu

    1988-01-01

    Trapping effects related directly with the oxygen vacancy in YBa 2 Cu 3 O 7-x are studied by the aid of positron lifetime and positron annihilation Doppler energy spectra of a thermally quenched sample. Results indicate that the trapping center is linearly related with the oxygen vacancy. Vacancies are ordered in the orthorhombic phase and disordered in the tetragonal phase on the Cu-O plane

  6. Interpretation of photovoltaic pulses in normal YBa2Cu3O7

    International Nuclear Information System (INIS)

    Scott, J.F.

    1990-01-01

    200 mV photovoltaic voltage pulses reported [C. L. Chang, A. Kleinhammes, W. G. Moulton, and L. R. Testardi Phys. Rev. B (in press)] for YBa 2 Cu 3 O 7 illuminated with 2--30 mJ/cm 2 at 532 nm are interpreted in terms of the complete theory of photovoltaic responses, including off-diagonal terms not recognized in the original theory. The resulting predictions are in reasonable quantitative agreement with experiment

  7. Apical Oxygen Anharmonicity Induced Spontaneous Polarization in YBa2Cu3O7

    International Nuclear Information System (INIS)

    Galabaatar, T.; Plakida, N.M.; Drechsler, S.-L.

    1995-01-01

    A model suggesting an asymmetric double-well form for the effective vibrational potential for the apical oxygen atoms in YBa 2 Cu 3 O 7 is formulated in the pseudo-spin representation and its phase diagram is studied. A set of parameters is found for which a spontaneous polarization may occur at a temperature close to the superconducting Tc, implying the possibility of formation of a ferroelectric state in the temperature region 90degK-250degK. (author)

  8. Investigation of flux penetration in YBa 2Cu 3O 7-δ filaments

    Science.gov (United States)

    Devos, P.; Buekenhoudt, A.; D'Anna, G.; André, M.-O.; Indenbom, M. V.; Benoit, W.; De Batist, R.; Cornelis, J.

    1994-12-01

    ac Susceptibility measurements using a low frequency torsion pendulum and an ac susceptometer were conducted on YBa 2Cu 3O 7-δ filaments in low magnetic dc fields (≤1T). Different dissipation peaks are observed, dependent on the temperature and the applied amplitude. The peak at low temperatures, which is of intergranular nature is studied in detail. The penetration follows the Bean model and the intergranular creep is observed.

  9. Magnetic study of superconductivity in YBa2Cu3O7-x thin films

    International Nuclear Information System (INIS)

    McGuire, T.R.; Gupta, A.; Koren, G.; Laibowitz, R.B.; Dimos, D.

    1989-01-01

    Magnetic and transport measurements on 0.3 micron thick films of YBa 2 Cu 3 O 7 - x made by a laser ablation technique show critical current densities of up to 40X10 6 amps/cm 2 . At 77K the transport data gives J c ∼5x10 6 amps/cm 2 while magnetic data is 40 % lower. Comparison is made with evaporated films

  10. Substitution of yttrium for boron in the structure of YBa2Cu3O7

    International Nuclear Information System (INIS)

    Dwelk, H.; Herrmann, R.; Pruss, N.; Freude, D.; Pfeifer, H.

    1989-01-01

    The influence of boron on superconducting properties of Y 1-x B x Ba 2 Cu 3 O 7-δ with x = 0 to 0.4 is studied. The analysis of 11 B NMR spectra and measurements of electric conductivity as a function of temperature show that boron is not incorporated into the YBa 2 Cu 3 O 7-δ framework on yttrium positions. (author)

  11. Self-generated magnetic flux in YBa$_2$Cu$_3$O$_{7-x}$ grain boundaries

    OpenAIRE

    Mints, R. G.; Papiashvili, Ilya

    2000-01-01

    Grain boundaries in YBa$_2$Cu$_3$O$_{7-x}$ superconducting films are considered as Josephson junctions with a critical current density $j_c(x)$ alternating along the junction. A self-generated magnetic flux is treated both analytically and numerically for an almost periodic distribution of $j_c(x)$. We obtained a magnetic flux-pattern similar to the one which was recently observed experimentally.

  12. Fractional Josephson vortices at YBa$_2$Cu$_3$O$_{7-x}$ grain boundaries

    OpenAIRE

    Mints, R. G.; Papiashvili, Ilya

    2001-01-01

    We report numerical simulations of magnetic flux patterns in asymmetric 45$^{\\circ}$ [001]-tilt grain boundaries in YBa$_2$Cu$_3$O$_{7-x}$ superconducting films. The grain boundaries are treated as Josephson junctions with the critical current density $j_c(x)$ alternating along the junctions. We demonstrate the existence of Josephson vortices with fractional flux quanta for both periodic and random $j_c(x)$. A method is proposed to extract fractional vortices from experimental flux patterns.

  13. High-temperature deformation of YBa2Cu3O7-δ with Ag additions

    International Nuclear Information System (INIS)

    Routbort, J.L.; Goretta, K.C.; Singh, J.P.

    1990-01-01

    The steady-state flow stress of YBa 2 Cu 3 O 7-δ containing 15 to 30 vol.% Ag has been measured in air at nearly constant compressive strain rates between 5 x 10 -6 and 1 x 10 -4 s -1 from 830 to 900 degrees C. Addition of Ag dramatically decreases the flow stress compared to that of the pure superconductor, but the stress exponents and the activation energy for deformation remain unchanged

  14. On hole spectra at YBa2Cu3O7 surfaces

    International Nuclear Information System (INIS)

    Calandra, C.; Manghi, F.; Minerva, T.

    1989-01-01

    The author present a theoretical study of the modification of the one-hole spectra induced by the surface in YBa 2 Cu 3 O 7 . Basal plane surface terminated either with Ba or CuO planes are considered. Correlation effects are included by using a Hubbard model Hamiltonian and by calculating the self-energy in the low density approximation. The results indicate that both the main bands and the satellites are sensitive to the choice of the surface

  15. Electron scattering rate in epitaxial YBa2Cu3O7 superconducting films

    Science.gov (United States)

    Flik, M. I.; Zhang, Z. M.; Goodson, K. E.; Siegal, M. P.; Phillips, Julia M.

    1992-09-01

    This work determines the electron scattering rate in the a-b plane of epitaxial YBa2Cu3O7 films using two techniques. Infrared spectroscopy yields the scattering rate at temperatures of 10, 78, and 300 K by fitting reflectance data using thin-film optics and a model for the free-carrier conductivity. The scattering rate is also obtained using kinetic theory and an extrapolation of normal-state electrical resistivity data to superconducting temperatures based on the Bloch theory for the phonon-limited electrical resistivity of metals. The scattering rates determined using both techniques are in agreement and show that the electron mean free path in the a-b plane of YBa2Cu3O7 superconducting films is three to four times the coherence length. Hence YBa2Cu3O7 is pure but not in the extreme pure limit. An average defect interaction range of 4 nm is obtained using the defect density resulting from flux-pinning considerations.

  16. Proximity-effect and tunneling in YBa2Cu3O7/metal layered structures

    International Nuclear Information System (INIS)

    Greene, L.H.; Feldmann, W.L.; Barner, J.B.; Farrow, L.A.; Miceli, P.F.; Ramesh, R.; Wilkens, B.J.; Bagley, B.G.; Giroud, M.; Rowell, J.M.

    1990-01-01

    Superconducting thin films of YBa 2 Cu 3 O 7 are prepared in-situ by on-axis sputter deposition from a single, composite target. The planar magnetron target composition of YBa:Cu = 1.08:1.76:4.5 sputtered onto MgO at T ∼ 750 degrees C in a 600 mTorr Ar-O 2 atmosphere yields reproducible superconducting films having T c (R = 0) > 80 K and stoichiometry 1:2:3, that are shiny and of near epitaxial crystalline quality. In order to ensure clean interfaces, YBa 2 Cu 3 O 7 /normal metal bilayers (to form SNS' Josephson junctions) and YBa 2 Cu 3 O 7 /normal metal/insulating barrier trilayers (to form SNIS' proximity tunnel junctions) are grown completely in-situ. (The S' = Pb counter electrode is evaporated ex-situ.) A supercurrent and Shapiro steps are observed in microwave irradiated SNS' (N = Ag) small area (5 x 10 -5 cm 2 junctions. In SNIS' tunnel junctions, high-quality Pb tunnelling is observed

  17. Harmonic and static susceptibilities of YBa2Cu3O7

    International Nuclear Information System (INIS)

    Ishida, T.; Goldfarb, R.B.; Okayasu, S.; Kazumata, Y.; Franz, J.; Arndt, T.; Schauer, W.

    1993-01-01

    Intergranular properties of the sintered superconductor YBa 2 Cu 3 O 7 have been studied in terms of complex harmonic magnetic susceptibility χ n χ n ' - iχ n '' (n integer) as well as DC susceptibility χ dc . As functions of temperature T, χ 1 ' and χ 1 '' depend on both the AC magnetic-field amplitude H ac and the magnitude of a superimposed DC field H dc . Only odd-harmonic susceptibilities are observed below the critical temperature, T c , for zero H dc while both odd and even harmonics are observed for nonzero H dc . With T constant, odd-harmonic susceptibilities are even functions of H dc , whereas even-harmonic susceptibilities are odd functions of H dc . Experimental intergranular characteristics of χ n ' and χ n '' are in good agreement with theoretical predictions from a simplified Kim model of magnetization. In contrast, even-harmonic susceptibilities measured for a GdBa 2 Cu 3 O 7 thin film and an YBa 2 Cu 3 O 7 single crystal are not prominent due to missing weak links, whereas odd-harmonic susceptibilities are remarkable. A survey of several models for the harmonic response of superconductors is presented. The DC susceptibility curve for the zero-field-cooled YBa 2 Cu 3 O 7 sample, χ ZFC (T), has a two-step structure arising from intra- and inter-granular components, similar to χ 1 '. DC susceptibility measured upon warming, χ FCW (T), shows a negative peak near T c for the sample cooled rapidly in small DC fields. DC susceptibility measured upon cooling, χ FCC (T), does not show a peak. A negative peak is not seen in measurements on a powdered sample. The negative peak can be explained by intergranular flux depinning upon warming. (orig.)

  18. High temperature superconductivity of YBa2Cu3O7-σ compounds

    International Nuclear Information System (INIS)

    Takriti, Salaheddin; Harara, Wafik

    1991-04-01

    A new preparation of YBa 2 Cu 3 O 7 -σ gave the orthorombic structure with critical temperature Tc=85 k. The space group was found to be Pmmm with lattice parameters (A o) : a=3.823, b=3.887 and c=11.678. The effects of γ-ray irradiation were noticed in the powder x-ray diffraction spectrums and in the changes of Tc which decrease as a function of γ-ray dose rate. The Cu 3+ /Cu 2+ ratio was changed at differents γ-ray dose rates, and these changes reduces the Tc sample also. (author). 28 refs., 6 figs., 1 tab

  19. Thermoelectric power of YBa2Cu3O7-δ: Phonon drag and multiband conduction

    International Nuclear Information System (INIS)

    Cohn, J.L.; Wolf, S.A.; Selvamanickam, V.; Salama, K.

    1991-01-01

    We report measurements of the a-b-plane thermopower (S) on crystalline YBa 2 Cu 3 O 7-δ (δ≤0.16) for temperatures below 310 K. Much sharper features in the T dependence of S are observed than have been previously reported. Both the temperature and oxygen-doping dependences of S, which have caused confusion, are consistently accounted for by conventional metallic theory for the first time. Strong phonon drag and two carrier species are indicated, with holes on the planes and electrons on the chains. An anomalous, positive component to S, observed for T 2 planes and optical-mode phonons

  20. Positron annihilation in a high-temperature superconductor YBa2Cu3O7

    International Nuclear Information System (INIS)

    Vavryshchuk, Ya.; Levandovski, M.; Rybakov, V.N.; Yutlandov, I.A.

    1988-01-01

    Positron annihilation as a function of temperature in high-temperature superconductors YBa 2 Cu 3 O 7-δ has been investigated. It is shown that a change in the annihilation capacity at the transition into superconducting state is relatively small. The change of r 1 and r 2 positron lifetimes as well as of the intensity of the component with r 2 -J 2 and Doppler broadening S parameter allows one to assume that transition into superconducting state is accompanied with a certain decrease in electron density and with decreasing number of defects or increasing size of crystalline net

  1. Macro and micro Raman spectroscopy of YBa2Cu3O7 films and microbridges

    International Nuclear Information System (INIS)

    Bock, A.

    1993-01-01

    In the present work Raman spectroscopy is used as a method to characterize the properties of YBa 2 Cu 3 O 7 -films. This is done in the usual (macro-)Raman set-up as well as in the micro-Raman set-up where the spatial resolution is about one micron. To obtain comparable results the Raman spectra have to be corrected for the spectral response of the spectrometer. Therefore a calibration of the set-up was performed. The calibration can be used to determine spot temperatures by comparing Stokes and Anti-Stokes spectra. Two different methods are developed to correct for the straylight which is additionally observed in Raman-spectra of YBa 2 Cu 3 O 7 -films. Macro- as well as micro-Raman measurements are used to characterize the film properties, where care has been taken to avoid damages by the laser itself. The macro-Raman set-up is used to identify the properties of the film, such as orientation, oxygen-content and morphology. Outgrowths and other particles on the surface are on the other hand investigated by micro-Raman spectroscopy. The surface morphology is additionally characterized by scanning-electron-microscopy. This is compared to the Raman data. Raman spectra of epitaxial YBa 2 Cu 3 O 7 -films are taken as a function of the temperature and exciting wavelength. The influence on the phonons and on the electronic background is discussed separately. The obtained results are analyzed by comparison with single-crystal measurements. The investigation of YBa 2 Cu 3 O 7 -microbridges in the macro-Raman set-up allows a correlation between the local optical and electrical properties of the bridge. A method is presented which can account for the heating in the laser spot with high accuracy. This method allows to determine local critical current densities as well as local critical temperatures on the microbridge. It provides also the possibility to take Raman spectra at precise spot temperatures. (orig./WL)

  2. Epitaxial growth of textured YBa2Cu3O7-δ films on silver

    International Nuclear Information System (INIS)

    Liu Dan-Min; Liu Wei-Peng; Suo Hong-Li; Zhou Mei-Ling

    2005-01-01

    YBa 2 Cu 3 O 7-δ (YBCO) films were deposited on (100), (110) and (111) oriented silver single crystals and {100} left angle 100 right angle, {110} left angle 211 right angle, {110} left angle 100 right angle +{110} left angle 011 right angle {110} left angle 011 right angle and {012} left angle 100 right angle textured Ag substrates using pulsed laser deposition. The relationship between the epitaxial growth YBCO film and silver substrate has been determined. It is shown that among polycrystalline Ag substrates, {110} left angle 011 right angle textured tape is suitable for the deposition of YBCO thin films having strong texture. (orig.)

  3. Microstructure and composition of electromagnetically-characterized YBa2Cu3O7-δ grain boundaries

    International Nuclear Information System (INIS)

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

    1991-01-01

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

  4. Plastic deformation of YBa2Cu3O7-x superconductor compound

    International Nuclear Information System (INIS)

    Torres V, G.; Moreno, J.E.

    1988-01-01

    The high temperature superconductor YBa 2 Cu 3 O 7-x shown a brittle behavior when deformed under ambient conditions. If a hydrostatic state of stress is imposed with a metal matrix, it is possible to induce exttended plastic deformations as a great as 200% were achieved using this method without loosing the superconductivity in the ceramic. The observed deformations mechanisms are similar to those observed in the superplastic metals and the boundary ceramic metal matrix was found to be highly coherent. This method opens a new technique that can be apllied in the manufacture of superconductor wire. (author) [pt

  5. Collective creep of vortex bundles in YBa2Cu3O7 crystals

    International Nuclear Information System (INIS)

    Civale, L.; Krusin-Elbaum, L.; Thompson, J.R.; Holtzberg, F.

    1994-01-01

    We present evidence for the crossover between creep of individual vortices and collective creep of vortex bundles from measurements of the relaxation of the persistent currents in YBa 2 Cu 3 O 7 single crystals over long periods of time. In the single-vortex regime at low fields the relaxation is fast and is characterized by an exponent μ congruent 0.16, as predicted in the collective-creep scenario. With increasing field, collective bundling of vortices induces a slowdown of the relaxation, with a maximum μ congruent 1.4. At even higher fields, μ decreases again to about 1 as the size of the bundles grows

  6. Pinning-to-barrier crossover in YBa2Cu3O7-δ single crystals

    Science.gov (United States)

    Indenbom, M. V.; van der Beek, C. J.; Berseth, V.; Konczykowski, M.; Holtzberg, F.; Benoit, W.

    1996-03-01

    The behaviour of magnetic flux in high purity untwinned YBa2Cu3O7-δ (YBCO) single crystals is visualised by means of the magneto-optical technique. It is observed that after zero field-cooling at high temperatures near T c , flux penetrates directly to the sample center over a flux free edge area, in contrast to the usual Bean-like flux penetration from the edges. This fact clearly shows that volume pinning becomes negligible compared with the edge barrier. The role of the recently rediscovered geometrical barrier in the crystal magnetisation is discussed.

  7. Disorder and chain superconductivity in YBa2Cu3O7

    International Nuclear Information System (INIS)

    Atkinson, W.A.

    1999-01-01

    The effects of chain disorder on superconductivity in YBa 2 Cu 3 O 7-δ are discussed within the context of a proximity model. Chain disorder causes both pair breaking and localization. The hybridization of chain and plane wave functions reduces the importance of localization, so that the transport anisotropy remains large in the presence of a finite fraction δ of oxygen vacancies. Penetration depth and specific heat measurements probe the pair breaking effects of chain disorder, and are discussed in detail at the level of the self-consistent T-matrix approximation. Quantitative agreement with these experiments is found when chain disorder is present. copyright 1999 The American Physical Society

  8. Anisotropy in superconducting gap in YBa2Cu3O7

    Science.gov (United States)

    Verma, Sanjeev K.; Kumari, Anita; Gupta, Anushri; Indu, B. D.

    2018-04-01

    Taking into account the modified form of Born-Mayer-Huggins potential (MBMHP) and many body quantum dynamics based Green's function theory via a modified Hamiltonian which includes the effects of electrons, phonons, anharmonicities, defects and electron-phonon interactions; the quasiparticle renormalized frequency has been obtained and numerically analyzed for high temperature superconductor (HTS) cuprate YBa2Cu3O7-δ. This evaluation enables one to calculate superconducting gap (SG) in [100] and [010] direction through the dispersion of renormalized mode. A higher SG found in [010] than [100] direction at different doping level establishing its anisotropic nature.

  9. Defect cascades produced by neutron irradiation in YBa2Cu3O7-δ superconductors

    International Nuclear Information System (INIS)

    Frischherz, M.C.; Kirk, M.A.; Farmer, J.

    1994-02-01

    The defect cascades produced by fast neutron irradiation of YBa 2 Cu 3 O 7-δ single crystals were studied by transmission electron microscopy. The visible defects were found to have sizes between 1 and 5 rim. Defect densities were obtained as a function of neutron fluence between 2 and 8x 10 21 m -2 (E>0.1 MeV). The measured defect density scales linearly with fluence and amounts to 1x10 22 m -3 at a neutron fluence of 2x10 2l m -2 . The defect stability was studied at room temperature and through annealing to 400 degrees C

  10. Doping and defects in YBa2Cu3O7: Results from hybrid density functional theory

    KAUST Repository

    Schwingenschlögl, Udo

    2012-06-21

    Modified orbital occupation and inhomogeneous charge distribution in high-Tc oxide compounds due to doping and/or defects play a huge role for the material properties. To establish insight into the charge redistribution, we address metallic YBa2Cu3O7 in two prototypical configurations: Ca doped (hole doping) and O deficient (electron doping). By means of first principles calculations for fully relaxed structures, we evaluate the orbital occupations. We find that the change of the charge density, in particular in the CuO2 planes, shows a complex spatial pattern instead of the expected uniform (de-)population of the valence states.

  11. Linewidth of Josephson oscillations in YBa2Cu3O7-x grain-boundary junctions

    DEFF Research Database (Denmark)

    Divin, Yu. Ya.; Mygind, Jesper; Pedersen, Niels Falsig

    1993-01-01

    The AC Josephson effect in YBa2Cu3O7-x grain-boundary junctions (GBJs) was studied in the temperature range from 4 K to 90 K. The temperature dependence of the linewidth of millimeter-wave Josephson oscillations was measured, and it is shown that the derived effective noise temperature of GBJ mig...... Josephson oscillations observed at 77 K was equal to 380 MHz, which demonstrates the applicability of GBJ, particularly in the field of radiation spectroscopy, even at liquid nitrogen temperatures...

  12. Microwave-detected optical response of YBa2Cu3O7-x thin films

    International Nuclear Information System (INIS)

    Kaplan, R.; Carlos, W.E.; Cukauskas, E.J.; Ryu, J.

    1990-01-01

    Microwave-detected optical response (MDOR) of YBa 2 Cu 3 O 7-x and other oxide superconductor thin films is shown to yield information complementary to that provided by trasnport photoconductivity measurements. The MDOR technique yields a superposition of response from all illuminated portions of a sample, irrespective of the existence of a resistive macroscopic percolative current path. The response is found to be bolometric at temperatures for which resistance appears in transport measurements. At low temperatures MDOR results imply a nonbolometric response which in some respects is consistent with nonequilibrium quasiparticle concentration due to radiative pair breaking

  13. Direct observation of Fermi surface in YBa2Cu3O7

    International Nuclear Information System (INIS)

    Haghighi, H.; Kaiser, J.H.; Rayner, S.; West, R.N.; Liu, J.Z.; Shelton, R.; Howell, R.H.; Solal, F.; Fluss, M.J.

    1991-01-01

    We have performed a high-precision measurement (5x10 8 coincidence counts) of the basal-plane electron-positron momentum density in well oxygenated, twin-free, single crystals of YBa 2 Cu 3 O 7-δ . The raw, processed, and K-space reduced spectra unambiguously show a clear image of a major Fermi surface sheet. The form and profile of that image are in substantial quantitative agreement with theoretical predictions of a Γ-X electron ridge section associated with states in the CuO chains

  14. LaNiO3 buffer layers for high critical current density YBa2Cu3O7-δ and Tl2Ba2CaCu2O8-δ films

    International Nuclear Information System (INIS)

    Carlson, C.M.; Parilla, P.A.; Siegal, M.P.; Ginley, D.S.; Wang, Y.; Blaugher, R.D.; Price, J.C.; Overmyer, D.L.; Venturini, E.L.

    1999-01-01

    We demonstrate high critical current density superconducting films of YBa 2 Cu 3 O 7-δ (YBCO) and Tl 2 Ba 2 CaCu 2 O 8-δ (Tl-2212) using LaNiO 3 (LNO) buffer layers. YBCO films grown on an LNO buffer layer have only a slightly lower J c (5 K, H=0) than films grown directly on a bare LaAlO 3 substrate. YBCO films grown on LNO buffer layers exhibit minor microstructural disorder and enhanced flux pinning. LNO-buffered Tl-2212 samples show large reductions in J c at all temperatures and fields compared to those grown on bare LaAlO 3 , correlating to both a-axis grain and nonsuperconducting phase formation. LNO could be a promising buffer layer for both YBCO and Tl-based superconducting films in coated conductor applications. copyright 1999 American Institute of Physics

  15. LaNiO3 Buffer Layers for High Critical Current Density YBa2Cu3O7δ and Tl2Ba2CaCu2O8δ Films

    International Nuclear Information System (INIS)

    Carlson, C.M.; Parilla, P.A.; Siegal, M.P.; Ginley, D.S.; Wang, Y.-T.; Blaugher, R.D.; Price, J.C.; Overmyer, D.L.; Venturini, E.L.

    1999-01-01

    We demonstrate high critical current density superconducting films of YBa 2 Cu 3 O 7-δ (YBCO) and Tl 2 Ba 2 CaCu 2 O 8-δ (Tl-2212) using LaNiO 3 (LNO) buffer layers. YBCO films grown on an LNO buffer layer have only a slightly lower J c (5K, H=0) than films grown directly on a bare LaAlO 3 substrate. It is noteworthy that YBCO films grown on LNO buffer layers exhibit minor microstructural disorder and enhanced flux pinning. LNO-buffered Tl-2212 samples show large reductions in J c at all temperatures and fields compared to those grown on bare LaAlO 3 , correlating to both a-axis grain and nonsuperconducting phase formation. With additional optimization, LNO could be a promising buffer layer for both YBCO and Tl-based superconducting films, perhaps ideally suited for coated conductor applications

  16. Wet chemical passivation of YBa2Cu3O(7-x)

    Science.gov (United States)

    Vasquez, R. P.; Hunt, B. D.; Foote, M. C.

    1990-01-01

    Wet chemical techniques are described for treatment of YBa2Cu3O(7-x) surfaces, which result in the formation of native compounds known to have little or no reactivity to water. Suitable native compounds include CuI, BaSO4, CuS, Cu2S, YF3, and the oxalates. Formation of surface layers in which these nonreactive native compounds are major constituents is verified with X-ray photoelectron spectroscopy (XPS) measurements on YBa2Cu3O(7-x) films treated with dilute solutions of HI, H2SO4, Na2S, HF, or H2C2O4. No significant changes are observed in the XPS spectra when the sulfide, sulfate, or oxalate films are dipped in water, while the iodide and fluoride films show evidence of reaction with water. X-ray diffraction measurements show that the superconducting phase is absent in the sulfide film, but is unaffected by the oxalate and sulfate treatments.

  17. Infrared refractive index of thin YBa2Cu3O7 superconducting films

    International Nuclear Information System (INIS)

    Zhang, Z.M.; Choi, B.I.; Le, T.A.; Flik, M.I.; Siegal, M.P.; Phillips, J.M.

    1992-01-01

    This work investigates whether thin-film optics with a constant refractive index can be applied to high-T c superconducting thin films. The reflectance and transmittance of YBa 2 Cu 3 O 7 films on LaAlO 3 substrates are measured using a Fourier-transform infrared spectrometer at wavelengths from 1 to 100 μm at room temperature. The reflectance of these superconducting films at 10K in the wavelength region from 2.5 to 25 μm is measured using a cryogenic reflectance accessory. The film thickness varies from 10 to 200 nm. By modeling the frequency-dependent complex conductivity in the normal and superconducting states and applying electromagnetic-wave theory, the complex refractive index of YBa 2 Cu 3 O 7 films is obtained with a fitting technique. It is found that a thickness-independent refractive index can be applied even to a 25nm film, and average values of the spectral refractive index for film thicknesses between 25 and 200 nm are recommended for engineering applications

  18. Critical Josephson current in a model Pb/YBa2Cu3O7-δ junction

    International Nuclear Information System (INIS)

    Atkinson, W.A.; Carbotte, J.P.

    1995-01-01

    We consider a simple model for a c-axis Pb/YBa 2 Cu 3 O 7-δ Josephson junction. The observation of a nonzero current in such a junction by Sun et al. [Phys. Rev. Lett. 72, 2267 (1994)] has been taken as evidence against d-wave superconductivity in YBa 2 Cu 3 O 7-δ . We suggest, however, that the pairing interaction in the CuO 2 planes may well be d wave but that the CuO chains destroy the tetragonal symmetry of the system. We examine two ways in which this happens. In a simple model of an incoherent junction, the chains distort the superconducting condensate away from d x 2 -y 2 symmetry. In a specular junction the chains destroy the tetragonal symmetry of the tunneling matrix element. In either case, the loss of tetragonal symmetry results in a finite Josephson current. Our calculated values of the critical current for specular junctions are in good agreement with the results of Sun and co-workers

  19. Galvanomagnetic properties of atomically disordered compounds YBa2Cu3O7

    International Nuclear Information System (INIS)

    Kar'kin, A.E.; Goshchitskij, B.N.

    2001-01-01

    To clarify the peculiarities of the metal-dielectric transition (MDT) in the HTSC type compounds one investigated into the galvanomagnetic properties of YBa 2 Cu 3 O 7 polycrystalline specimens irradiated by fast neutrons under 80 K temperature with F = 2x10 19 cm -2 fluence and subsequent to their exposure to the isochronal annealings within 150-390 K temperature range. It was determined that temperature dependences of R H Hall coefficient and of MR magnetic resistances of YBa 2 Cu 3 O 7 polycrystalline compounds disordered by fast neutrons retained the anomalous properties peculiar to the HTSC type disordered compounds in spite of the fact that conductivity was not a metallic one. This behavior is explained by the fact that in the disordered compounds there are two co-existing electron phases with conductivity as to the localized and the metallic states. Concentration of metallic phase is lower than threshold of passing, that is why, conductivity of this system is of dielectric type while R H and MR have temperature dependences similar to metallic phase that are renormalized by magnitude [ru

  20. c-Axis projected electron-positron momentum density in YBa2Cu3O7

    International Nuclear Information System (INIS)

    Bansil, A.; Smedskjaer, L.C.

    1990-11-01

    The authors present the theoretical c-axis projected electron-positron momentum density N 2γ (P x ,p y ) in YBa 2 Cu 3 O 7 based on the local density approximation (LDA) framework along various lines in momentum space. The calculations use the Korringa-Kohn-Rostoker (KKR) band structure formalism. The anisotropic distribution defined by taking cuts through the calculated spectra along different lines in the (p x ,p y ) plane possesses complex structures which arise from both Fermi surface effects and the anisotropy of the smoothly varying underlying background from filled bands; the maximum size of the anisotropy is about 10% of N 2γ (0,0). The theoretically predicted N 2γ (p x , y ) distribution is compared with the measured 2D-ACAR spectrum. The considerations suggest that in interpreting the 2D-ACAR data on YBa 2 Cu 3 O 7 in terms of a band theory LDA picture, a substantial, largely isotropic, background should be subtracted from both the 2D-ACAR's and the associated LCW-folded spectra

  1. YBa_2Cu_3O_{7-δ} : in pursuit of the ideal microstructure

    Science.gov (United States)

    Smith, D. S.; Suasmoro, S.; Lejeune, M.; Rabier, J.; Denanot, M. F.; Heintz, J. M.; Magro, C.; Bonnet, J. P.

    1992-02-01

    This paper examines the role of different factors in the microstructure of ceramic YBa2Cu3O{7-δ} with emphasis on its electrical response. In particular we discuss : 1. the effect of microstructural variations on j_c and ρ_{300}, 2. measurement of j_c, 3. the presence of minor phases and carbonates, 4. oxygen uptake and microcracks, 5. plastic deformation and related structural defects. Dans cet article, nous examinons d'une part la réponse électrique de céramiques supraconductrices massives de type YBa2Cu3O{7-δ} et d'autre part sa relation avec la microstructure. Nous présenterons successivement : 1. L'incidence de modifications microstructurales sur les valeurs de j_c et ρ_{300}, 2. les mesures expérimentales de j_c, 3. la présence de phases minoritaires et de carbonates, 4. la reprise d'oxygène et la microfissuration, 5. la déformation plastique et les défauts structuraux associés.

  2. Interactions in YBa2Cu3O7-x aqueous suspensions

    International Nuclear Information System (INIS)

    Dusoulier, Laurent; Cloots, Rudi; Vertruyen, Benedicte; Garcia-Fierro, Jose L.; Moreno, Rodrigo; Ferrari, Begona

    2009-01-01

    Surface charging mechanism of YBa 2 Cu 3 O 7-x (YBCO) particles in water has been investigated in order to understand their colloidal behaviour and stabilise concentrated suspensions. A broad study relating the suspension parameters (pH and zeta potential) vs. the conditions of the suspension performance (atmosphere and time) has been shown and discussed. The zeta potential values remain positive in all the pH range for the highest powder concentration studied (10 g l -1 ), evidencing a large influence of the solid content in the particle charge. The chemistry of YBa 2 Cu 3 O 7-x in water has been studied through the chemical analysis of the supernatant by inductively coupled plasma (ICP), and the surface analysis of the particles by X-ray diffraction analysis (XRD) and X-ray photoelectron spectroscopy (XPS). The presence of BaCO 3 , CuO, and the hydrolysed Ba species, such as Ba(OH) 2 and Ba(OH) + , at the particles surface has been evaluated as a function of the powder concentration. Based on these analyses, the dependence of the colloidal behaviour of YBCO on the presence of Ba soluble species has been determined. A stabilisation mechanism for YBCO particles in aqueous suspension focus on the powders deleterious minimization was proposed.

  3. Josephson spectroscopy of terahertz losses in [100]-tilt YBa2Cu3O7-x bicrystal junctions

    International Nuclear Information System (INIS)

    Divin, Y; Lyatti, M

    2008-01-01

    Terahertz losses in the [100]-tilt YBa 2 Cu 3 O 7-x grain-boundary junctions were studied using admittance Josephson spectroscopy. The I-Vcurves of the [100]-tilt YBa 2 Cu 3 O 7-x junctions, when annealed in atomic oxygen, were described by the resistively shunted junction model (RSJ) with an accuracy of better than 0.5% at the temperature range, where the characteristic voltage I c R n n -1 . At low temperatures, where I c R n >> kT/2e, the absorption of Josephson radiation by optical phonon modes in YBa 2 Cu 3 O 7-x was found to be reflected in the I-V curve of the [100]-tilt junctions. The most prominent structure is situated at the voltages V ∼ 9.5 mV, which gives the corresponding Josephson frequency of 4.6 THz in good agreement with the frequency of the strongest IR active optical phonon mode in YBa 2 Cu 3 O 7-x . Assignment of additional lines in the derived losses is discussed according to available data on lattice dynamic calculations and experimental data for a dynamic conduction Reσ 1 (f) of YBa 2 Cu 3 O 7-x . Josephson spectroscopy might be useful for study of low-energy excitations in high-T c materials

  4. An evaluation of absorption spectroscopy to monitor YBa2Cu3O7-x precursors for metal organics chemical vapor deposition processing

    International Nuclear Information System (INIS)

    Matthew Edward Thomas

    1999-01-01

    Absorption spectroscopy was evaluated as a technique to monitor the metal organics chemical vapor deposition (MOCVD) process for forming YBa 2 Cu 3 O 7-x superconducting coated conductors. Specifically, this study analyzed the feasibility of using absorption spectroscopy to monitor the MOCVD supply vapor concentrations of the organic ligand 2,2,6,6-tetramethyl-3,5-heptanedionate (TMHD) metal chelates of barium, copper, and yttrium. Ba(TMHD) 2 , Cu(TMHD) 2 , and Y(TMHD) 3 compounds have successfully been vaporized in the MOCVD processing technique to form high temperature superconducting ''coated conductors,'' a promising technology for wire fabrication. The absorption study of the barium, copper, and yttrium (TMHD) precursors was conducted in the ultraviolet wavelength region from 200nm to 400nm. To simulate the MOCVD precursor flows the Ba(TMHD) 2 , Cu(TMHD) 2 , and Y(TMHD) 3 complexes were vaporized at vacuum pressures of (0.03--10)Torr. Spectral absorption scans of each precursor were conducted to examine potential measurement wavelengths for determining vapor concentrations of each precursor via Beer's law. The experimental results show that under vacuum conditions the barium, copper, and yttrium (TMHD) precursors begin to vaporize between 90 C and 135 C, which are considerably lower vaporization temperatures than atmospheric thermal gravimetric analyses indicate. Additionally, complete vaporization of the copper and yttrium (TMHD) precursors occurred during rapid heating at temperatures between 145 C and 195 C and after heating at constant temperatures between 90 C and 125 C for approximately one hour, whereas the Ba(TMHD) 2 precursor did not completely vaporize. At constant temperatures, near constant vaporization levels for each precursor were observed for extended periods of time. Detailed spectroscopic scans at stable vaporization conditions were conducted

  5. Defect cascades produced by neutron irradiation in YBa2Cu3O7

    International Nuclear Information System (INIS)

    Frischherz, M.C.; Kirk, M.A.; Farmer, J.; Greenwood, L.R.; Weber, H.W.

    1992-12-01

    The defect cascades produced by fast neutron irradiation of YBa 2 Cu 3 O 7-δ single crystals were studied by transmission electron microscopy. The visible defects were found to have sizes between 1 and 5 nm. Defect densities were obtained as a function of neutron fluence between 2 and 8 x 10 21 m -2 (E>0.1 MeV) and compared to damage calculations. The measured defect density was found to scale linearly with fluence and to be 1 x 10 22 m -3 at 2 x 10 21 m -2 . The defect stability was studied at room temperature and through annealing to 400 degrees C. The high fluence regime (∼10 22 m -2 ) was investigated as well

  6. Melt-spin processing of YBa2Cu3O7-x

    International Nuclear Information System (INIS)

    Folkerts, T.J.; Kramer, M.J.; McCallum, R.W.; Iowa State Univ. of Science and Technology, Ames, IA

    1991-01-01

    We introduce a novel containerless melt-spin processing technique for YBa 2 Cu 3 O 7-x using prereacted oxide powders which are rapidly melted and subsequentially quenched in a controlled atmosphere. This results in flakes with typical dimensions of 3000x150x15 μm 3 . Powder XRD indicates that all samples contain Y 2 O 3 , but that the Ba--Cu--O phases present depend on the processing parameters. SEM and TEM studies show these phases are finely dispersed: the typical grain size for Y 2 O 3 is 1--2 μm, and for the Ba--Cu--O phases it is <0.5 μm

  7. Superconducting YBa2Cu3O7-x fibers from the thermoplastic gel method

    International Nuclear Information System (INIS)

    Uchikawa, F.; Mackenzie, J.D.

    1989-01-01

    The successful fabrication of ceramic superconducting YBa 2 Cu 3 O 7-x fibers has been investigated. A new method was proposed for synthesis of the fibers through a solution route. The thermoplastic gels were synthesized using Y, Ba, Cu, ethoxides, and diethylenetriamine. The fibers were drawn from the reheated gels. The fibers were characterized by x-ray diffraction, SEM, and shrinkage ratio measurements. The fired and then annealed fiber is shown to have a superconducting transition temperature of 91 K (onset) and zero resistance temperature of 84 K. With regard to the fired fibers, it is found that the surface area increased and superconducting transition temperature decreased with increasing organic content in the initial gel. The usefulness of this method is shown and the structure of the synthesized gel is discussed

  8. Microstructure within domains of melt-processed YBa2Cu3O7-x superconductors

    International Nuclear Information System (INIS)

    Alexander, K.B.; Goyal, A.; Kroeger, D.M.; Selvamanickam, V.; Salama, K.

    1992-01-01

    The microstructure within single domains of melt-processed YBa 2 Cu 3 O 7-x (1:2:3) material has been examined. Rather than composing a ''brick-wall'' structure, the stacked, parallel platelets within the domains are actually portions of a single crystal. A growth mechanism is proposed that is consistent with the observed microstructural features. The anisotropic nature of the growth of 1:2:3 results in gaps separating the platelets. The gaps, however, terminate within domains, resulting in interconnected single-crystalline material. The absence of weak-link behavior for current flow along the c axis and the high critical-current densities observed within domains of melt-processed 1:2:3 material are readily explained by the fact that current flow is solely through single-crystalline material

  9. Lattice thermal conductivity of YBa2Cu3O7

    International Nuclear Information System (INIS)

    Cohn, J.L.; Wolf, S.A.; Vanderah, T.A.; Selvamanickam, V.; Salama, K.

    1992-01-01

    We report a systematic study of the ab-plane thermal conductivity (K) on single crystal and liquid-phase processed (LPP) specimens of YBa 2 Cu 3 O 7-δ (δ≤0.16) in the temperature range 10 K ≤ T ≤ 300 K. From measurements of electrical conductivity on the same specimens and application of the Wiedemann-Franz law we estimate the relative contributions to the heat conduction from the carriers and the lattice. The normal-state phonon scattering mechanisms are quantified by calculations which employ the conventional theory of lattice heat conduction by longitudinal acoustic phonons. Differences in the magnitude and temperature dependence of K for the LPP and crystal specimens are accounted for by differences in the relative weight of phonon-defect, phonon-carrier, and phonon-phonon scattering. For all specimens phonon-defect scattering predominates throughout most of the temperature range. (orig.)

  10. Laser writing and rewriting on YBa2Cu3O7 films

    International Nuclear Information System (INIS)

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

    1991-01-01

    High-resolution patterning (4 μm) has been achieved on epitaxial thin films of the high-temperature superconductor YBa 2 Cu 3 O 7-δ using laser writing. A focused laser beam is applied to write semiconducting patterns on superconducting films in a vacuum or in a nitrogen atmosphere. The semiconducting patterns are shown to be formed by a reduction of the oxygen content due to local heating caused by the laser beam. The process does not cause any structural damage and does not change the surface morphology. When reapplying the same laser beam and rewriting the film in an oxygen atmosphere, it is possible to restore the superconductive properties. The application of this method for production of superconducting microelectronic circuits is discussed

  11. AC Josephson effect in YBa2Cu3O7-δ bicrystal grain boundary junctions

    International Nuclear Information System (INIS)

    Fischer, G.M.; Andreev, A.V.; Divin, Y.Ya.; Freltoft, T.; Mygind, J.; Pedersen, N.F.; Shen Yueqiang; Vase, P.

    1994-01-01

    The ac Josephson effect in YBa 2 Cu 3 O 7-δ bicrystal grain boundary junctions was studied in the temperature range from 4K to 90K. Junctions with widths from 0.2 to 50 μm were made on SrTiO 3 bicrystal substrates by laser ablation and e-beam lithography. The linewidth of the Josephson oscillations is derived from the shape of the dc voltage response to low-intensity, f = 70 GHz radiation at voltages V ≅ (h/2e) f, assuming the RSJ model. The effect of the size on the Josephson behavior of this type of high-T c junctions was studied. Close to T c the linewidth of the Josephson oscillations was shown to be determined by thermal fluctuations. (orig.)

  12. YBa2Cu3O7 nanobridges fabricated by direct-write electron beam lithography

    International Nuclear Information System (INIS)

    Wendt, J.R.; Martens, J.S.; Ashby, C.I.H.; Plut, T.A.; Hietala, V.M.; Tigges, C.P.; Ginley, D.S.; Siegal, M.P.; Phillips, J.M.; Hohenwarter, G.K.G.

    1992-01-01

    A direct method for nondamaging, nanometer-scale patterning of high T c superconductor thin films is presented. We have fabricated superconducting nanobridges in high-quality, epitaxial thin-film YBa 2 Cu 3 O 7 (YBCO) by combining direct-write electron beam lithography and an improved aqueous etchant. Weak links with both length and width dimensions less than 20 nm have exhibited critical currents at 77 K of 4--20 μA and I cRn products of 10--100 μV which compare favorably with results for other YBCO junction technologies. We have used this technique in the fabrication of a shock-wave pulse former as an initial demonstration of its applicability to monolithic superconductive electronics

  13. Transport measurements on superconducting YBa2Cu3O7-δ thin film lines

    International Nuclear Information System (INIS)

    Moeckly, B.H.; Lathrop, D.K.; Redinbo, G.F.; Russek, S.E.; Buhrman, R.A.

    1990-01-01

    Critical current densities, magnetic field response, and microwave response have been measured for laser ablated YBa 2 Cu 3 O 7-δ thin film lines on MgO and SrTiO 3 substrates. Films on SrTiO 3 have critical current densities > 1 x 10 6 A/cm 2 at 77 K and show uniform transport properties in lines of all sizes. Films on MgO have critical current densities which range between 10 2 and 10 6 A/cm 2 at 77 K and show considerable variation from device to device on the same chip. Narrow lines on MgO with low critical current densities show Josephson weak link structure which includes RSJ-like IV curves, microwave induced constant voltage steps, and a high sensitivity to magnetic field. The presence of the Josephson weak links if correlated with small amounts of misaligned grains in film on MgO

  14. Monte Carlo simulation of ion-beam channeling in YBa2Cu3O7

    International Nuclear Information System (INIS)

    Khodyrev, V.A.; Chumanov, V.Ya.; Bourdelle, K.K.; Pokhil, G.P.

    1994-01-01

    A Monte Carlo program (UPIC) for the simulation of ion channeling in crystals with complex structure is described. The program is applied to simulate the channeling of 1.5 MeV He + and 1 MeV D + near the [001] axis of YBa 2 Cu 3 O 7 assuming strongly correlated atomic displacements along the [001] Cu-O rows in the superconducting state. The values for the abrupt change in the half-width of the channeling dip observed in experiments [R.P. Sharma et al., Phys. Rev. B 38 (1988) 9287] at the temperature of the superconducting transition, T c , are reproduced in the simulations with correlation coefficients of 0.8-0.9. The increase in the minimum channeling yield at T c found in measurements [T. Haga et al., Phys. Rev. B 41 (1990) 826] can be qualitatively explained by the increase in dechanneling rate due to correlations. ((orig.))

  15. Patterned YBa2Cu3O7-x thin films from photopolymerizable precursors

    International Nuclear Information System (INIS)

    Hung, Y.; Agostinelli, J.A.

    1990-01-01

    A technique which combines the fabrication and patterning of thin films of the high T c superconductor YBa 2 Cu 3 O 7-x has been developed. The technique possesses the essential features of the metalorganic decomposition method with the additional attribute that the metalorganic precursor is photopolymerizable. Patterns are generated directly in the precursor film using optical exposure through a mask followed by development in a solvent. A subsequent thermal treatment transforms the patterned precursor film to the oriented superconducting phase with c axis perpendicular to the substrate surface. Resistivity measurements for such a patterned film on a single crystal (100)MgO substrate show an onset to the superconducting state occurring at 85 K with zero resistivity below 67 K

  16. Ab-initio calculations of superconducting properties of YBa2Cu3O7

    International Nuclear Information System (INIS)

    Zhao, G.L.; Bagayoko, D.

    1999-01-01

    The authors present ab-initio calculations for the electronic structure and superconducting properties of YBa 2 Cu 3 O 7 (YBCO). The electronic structure was calculated using a self-consistent ab-initio LCAO method. They solved the anisotropic Eliashberg gap equation numerically. The strong coupling of the high energy optical phonons around 60--73 meV, with the electrons at the Fermi surface, leads to a high Tc in YBCO. The calculated Tc is about 89 K for μ* = 0.1. The good agreement of the calculated results with experimental measurements and the ab-initio nature of the calculations support the scenario of an anisotropic s-wave superconductor for YBCO

  17. Mechanical response of the flux lines in ceramic YBa2Cu3O7

    Science.gov (United States)

    Luzuriaga, J.; André, M.-O.; Benoit, W.

    1992-06-01

    We have studied the mechanical response of the flux-line lattice (FLL) in ceramic samples of YBa2Cu3O7 by means of a low-frequency forced pendulum. The internal friction and elastic modulus variation of the FLL have been measured as a function of temperature for different values of the applied stress. A somewhat different behavior was observed whether a zero-field-cooling or field-cooling procedure was followed. Measurements of the internal friction and elastic modulus as a function of the applied stress at constant temperature show amplitude-dependent dissipation, with a maximum dissipation at intermediate values of the stress. This dependence is well fitted by a rheological model of extended dry friction, if we restrict ourselves to the dissipation and modulus at fixed temperature. The agreement is not so good when attempting to extend the model to fit the temperature dependence.

  18. Neutron measurements of the vortex lattice in YBa2Cu3O7

    International Nuclear Information System (INIS)

    Mook, H.A.; Yethiraj, M.; Wignall, G.D.; Forgan, E.M.; Lee, S.L.; Cubitt, R.; McK. Paul, D.; Armstrong, T.

    1992-01-01

    Neutron diffraction has been used to measure the vortex lattice scattering for YBa 2 Cu 3 O 7 . A square pattern is found when the field is applied along the c axis, while a triangular pattern is found when the field is applied well away from the c axis. High-resolution measurements for the square pattern show that the vortex lattice has long-range orientational order but only short-range positional order. The temperature dependence of the penetration depth is not that expected for a superconductor with a conventional s-wave BCS type gap. Preliminary measurements for temperatures near the irreversibility line are consistent with the occurrence of melting of the vortex lattice or glass phase

  19. Femosecond dynamics of quasi-particles in YBa2Cu3O7-δ superconductor films

    International Nuclear Information System (INIS)

    Han, S.G.; Vardeny, Z.V.; Symko, O.G.; Koren, G.

    1991-01-01

    This paper reports on the transient electronic response of YBa 2 Cu 3 O 7-δ epitaxially grown HT c superconductor thin films in the femtosecond time domain, using transient photoinduced reflectivity (ΔR) with 60 fsec time resolution. For temperatures T > T c only a bolometric signal was observed with ΔR > O. For T c ΔR < O with a temperature dependent rise time of order 300 fsec followed by a relaxation (of order 3 psec) into a state with Δ are explained in terms of quasi-particle (QP) electronic response giving ΔR < O. Thus the femtosecond rise time is interpreted as avalanche multiplication of QP across the gap 2Δ and the subsequent picosecond relaxation as QP recombination. The QP optical response is explained within the two fluid model

  20. Superconducting gap anisotropy and d-wave pairing in YBa2Cu3O7

    Science.gov (United States)

    Verma, Sanjeev K.; Gupta, Anushri; Kumari, Anita; Indu, B. D.

    2018-02-01

    Considering Born-Mayer-Huggins potential as a most suitable potential to study the dynamical properties of high-temperature superconductors (HTS), the many-body quantum dynamics to obtain phonon Green’s functions has been developed via a Hamiltonian that incorporates the contributions of harmonic electron and phonon fields, phonon field anharmonicities, defects and electron-phonon interactions without considering BCS structure. This enables one to develop the quasiparticle renormalized frequency dispersion in the representative high-temperature cuprate superconductor YBa2Cu3O7-δ. The superconducting gap shows substantial changes with increased doping. The in-plane gap study revealed a v-shape gap with a nodal point along kx = ±ky direction for optimum doping (δ = 0.16) and the nodal point vanished in underdoped and overdoped regimes. The dx2-y2 pairing symmetry is observed at optimum doping with the presence of s or dxy components ( < 3%) in underdoped and overdoped regimes.

  1. Feature of the energy gap in YBa2 Cu3 O7 from break junction measurements

    International Nuclear Information System (INIS)

    Ekino, T.; Minami, T.; Fujii, H.

    1995-01-01

    Superconducting energy gap in YBa 2 Cu 3 O 7 have been investigated using break junctions. The tunneling conductance, dI/dV, at T=4.2 K shows no leakage around zero bias, while the gap edge peaks are broadened compared to the simple BCS density of states. These features suggest the spatial distribution of the energy gap or the anisotropic s-wave pairing. The observed largest gap value, determined by the peak-to-peak (p-p) separation in dI/dV, is 140 meV, which corresponds to the 4 δ p-p of an SIS junction. The observed tunneling density of states is fairly well expressed by the probability distribution of the energy gap using the BCS density of states

  2. Non-isovalent alkali metal ''substitution'' in YBa2Cu3O7-y granular ceramics

    International Nuclear Information System (INIS)

    Cloots, R.; Liege Univ.; Rulmont, A.; Pekala, M.; Liege Univ.; Laval, J.Y.; Bougrine, H.; Liege Univ.; Ausloos, M.

    1995-01-01

    The aim of this paper is to study the influence of non-isovalent ''doping'' in YBa 2 Cu 3 O 7-y in particular on its synthesis conditions and on the resistive properties both with and without a magnetic field. We concentrate on the study of possible alkali ions (Na, K, Cs) ''substitution'' at the barium sites. A low temperature sintering process is used in order to induce a reactive liquid phase. The final chemical composition is discussed as a function of the amount of the liquid phase. No alkali ion is substituted. Carbonate layers are present. However, this (lack of) ''substitution'' leads to induced vacancies and improved electrical transport properties which are as good as in highly pure materials. For conciseness the case of Na ''substitution'' only is illustrated. The use of such data in order to probe the microstructure is emphasized. (orig.)

  3. Investigation of Chemical Bond Properties and Mssbauer Spectroscopy in YBa2Cu3O7

    Institute of Scientific and Technical Information of China (English)

    高发明; 李东春; 张思远

    2003-01-01

    Chemical bond properties of YBa2Cu3O7 were studied by using the average band-gap model. The calculated results show that the covalency of Cu(1)-O bond is 0.406, and one of Cu(2)-O is 0.276. Mssbauer isomer shifts of 57Fe in Y-123 were calculated by the chemical surrounding factor hv defined by covalency and electronic polarizability. The charge-state and site of Fe were determined. The relation between the coupling constant of electron-phonon interaction and covalency is employed to explain that the Cu(2)-O plane is more important than the Cu(1)-O chain on the superconductivity in the Y-123 compounds.

  4. Shear at Twin Domain Boundaries in YBa2Cu3O7-x

    Science.gov (United States)

    Caldwell, W. A.; Tamura, N.; Celestre, R. S.; MacDowell, A. A.; Padmore, H. A.; Geballe, T. H.; Koster, G.; Batterman, B. W.; Patel, J. R.

    2004-05-01

    The microstructure and strain state of twin domains in YBa2Cu3O7-x are discussed based upon synchrotron white-beam x-ray microdiffraction measurements. Intensity variations of the fourfold twin splitting of Laue diffraction peaks are used to determine the twin domain structure. Strain analysis shows that interfaces between neighboring twin domains are strained in shear, whereas the interior of these domains are regions of low strain. These measurements are consistent with the orientation relationships of twin boundaries within and across domains and show that basal plane shear stresses can exceed 100MPa where twin domains meet. Our results support stress field pinning of magnetic flux vortices by twin domain boundaries.

  5. New transition in the vortex liquid state of YBa2Cu3O7

    International Nuclear Information System (INIS)

    Kwok, Wai-Kwong; Karapetrov, Goran; Welp, Ulrich; Rydh, Andreas; Crabtree, George W.; Paulius, Lisa; Figueras, Jordi; Puig, Teresa; Obradors, X.

    2006-01-01

    We have carried out angular dependent magneto-transport measurements on optimally doped, untwinned YBa 2 Cu 3 O 7-δ crystals irradiated with high energy heavy ions to determine the onset of vortex line tension in the vortex liquid state. The dose matching field was controlled and kept at a low level to partially preserve the first order vortex lattice melting transition. A Bose glass transition is observed below the lower critical point which then transforms into a first order phase transition near 4 T. We find that the locus of points which indicates the onset of vortex line tension overlaps with the Bose glass transition line at low fields and then deviates at higher fields, indicating a new transition line in the vortex liquid state. This new line in the vortex liquid phase is dose independent and extends beyond the upper critical point

  6. Surface studies of YBa2Cu3O7-x -matching oxide substrates and interfaces

    International Nuclear Information System (INIS)

    Enevold Thaulov Andersen, J.

    1990-11-01

    Crystallographic changes as a result of heat-treatment at 700-900 deg. C are found for SrTiO 3 (100), MgO(100) and LaAlO 3 (100). The p(2x2) reconstruction of the SrTiO 3 (100) and the superstructures on MgO(100) and on LaAlO 3 (100) thus observed are suggested to be induced by segregation of impurities to the surface. The surface charge-effects which disturb electron- and photon-impact experiments with these insulators are removed by heat-treatments. Deposition of copper results in formation of copper islands on SrTiO 3 (100) and on LaAlO 3 (100). Yttrium forms islands on LaAlO 3 (100) and grows in a layer-by-layer mode on SrTiO 3 (100) and on MgO(100). An yttrium 1x1 epitaxy is observed on the MgO(100) surface, which is suggested to be an YO superstructure. Oxidation of the 1x1 Y/MgO(100) systems diminishes the charge-effects and improves all diffraction and spectroscopic measurements. This may be due to the formation of metallic states around the Fermi level when the film is oxidized. An in situ synthesized YBa 2 Cu 3 O 7 thin film on SrTiO 3 (100) compared to a thick epitaxial YBa 2 Cu 3 O 7-x (001) film on MgO(100) reveals differences in surface electronic structures but not in surface stoichiometries. (au) 18 refs

  7. Preparation of YBa2Cu3O7-δ epitaxial thin films by pulsed ion-beam evaporation

    International Nuclear Information System (INIS)

    Sorasit, S.; Yoshida, G.; Suzuki, T.; Suematsu, H.; Jiang, W.; Yatsui, K.

    2001-01-01

    Thin films of YBa 2 Cu 3 O 7-δ (Y-123) grown epitaxially have been successfully deposited by ion-beam evaporation (IBE). The c-axis oriented YBa 2 Cu 3 O 7-δ thin films were successfully deposited on MgO and SrTiO 3 substrates. The Y-123 thin films which were prepared on the SrTiO 3 substrates were confirmed to be epitaxially grown, by X-ray diffraction analysis. The instantaneous deposition rate of the Y-123 thin films was estimated as high as 4 mm/s. (author)

  8. Transport properties of YBa2Cu3O7/PrBa2Cu3O7 superlattices

    International Nuclear Information System (INIS)

    Jakob, G.; Hahn, T.; Stoelzel, C.; Tome-Rosa, C.; Adrian, H.

    1992-01-01

    We investigated the transport properties of high-quality YBa 2 Cu 3 O 7 /PrBa 2 Cu 3 O 7 superlattices. The exceptional structural order of the superlattices resulted in satellite peaks up to the ninth order in X-ray diffraction diagrams and high Tc values. We find high superconducting critical transport current densities j c even for ultrafine modulated superlattices which proves the existence of nearly continuous YBa 2 Cu 3 O 7 layers. The activation energy U is found to be constant or to have a linear temperatures dependence over a wide temperature range. (orig.)

  9. The ab-anisotropy of twinfree YBa2Cu3O7-delta above and below Tc

    NARCIS (Netherlands)

    Dam, B.; Rector, J.; Surdeanu, R.; Wijngaarden, R.J.; Koster, Gertjan; Peerdeman, F.; van Berkum, J.; de Groot, D.G.; Griessen, R.

    1998-01-01

    High quality twin-free c-axis oriented YBa2Cu3O7 films were grown by pulsed laser deposition on NdGaO3. We find resistive anisotropies between 1 < a/b < 1.6. The resistive anisotropy above Tc appears to be correlated to the anisotropy in the critical current below Tc. The normal state properties of

  10. Observation of distinct, temperature dependent flux noise near bicrystal grain boundaries in YBa2Cu3O7-x films

    DEFF Research Database (Denmark)

    Bukh, K. R.; Jacobsen, Claus Schelde; Hansen, Jørn Bindslev

    2000-01-01

    The characteristics of the magnetic flux noise in high temperature superconducting thin-films of yttrium-barium-copper-oxide (YBa2Cu3O7) in the vicinity of artificial grain boundaries have been studied by means of a low critical temperature superconducting quantum interference device (SQUID...

  11. On a possibility of cold fusion in deuterium-saturated YBa2Cu3O7-x ceramics in superconducting state

    International Nuclear Information System (INIS)

    Lipson, A.G.; Sakov, D.M.; Toporov, Yu.P.; Gromov, V.V.; Deryagin, B.V.

    1991-01-01

    A possibility to generate neutrons by deuterated YBa 2 Cu 3 O 7-x ceramics in superconducting (T c ) and normal (T>T c ) states is studied. The presented data points to a relationship between the processes of cold nuclear fusion and high-temperature superconductivity in YBa 2 Cu 3 O 7-x pellets deuterated at T c (77< T<90 K)

  12. Containerless processing of YBa2Cu3O7-δ superconductors

    International Nuclear Information System (INIS)

    Olive, J.R.; Hofmeister, W.H.; Bayuzick, R.J.; Carro, G.; McHugh, J.P.; Hopkins, R.H.; Vlasse, M.

    1993-01-01

    Containerless processing of YBa 2 Cu 3 O 7-δ was performed using drop tube and aero-acoustic levitation techniques. In drop tube experiments, two solidification microstructures developed which corresponded to the degree of melting. In aero-acoustic levitation experiments, three solidification microstructures developed. One microstructure was the result of incomplete homogenization of the melt. The second was due to slight undercooling into the Y 2 O 3 + liquid region of the phase diagram upon which primary Y 2 O 3 dendrites formed. The third was due to much deeper undercooling. In this case, the primary solidification structure consisted of dendrites of tetragonal 1:2:3 and some other interdendritic phase. Subsequent to solidification processing, these samples were annealed to single phase 1:2:3 with orthorhombic symmetry. SQUID magnetometer measurements indicated a sharp superconducting transition at approximately 85 K. Magnetic J c values, calculated using the Bean critical state model, indicated that the deeply undercooled and annealed samples had critical current densities on the order of 10 4 Acm -2

  13. Vortex bending in a tilted YBa2Cu3O7-δ crystal

    Science.gov (United States)

    Obaidat, I. M.; Park, S. J.; Safar, H.; Kouvel, J. S.

    1997-09-01

    Magnetization-vector measurements were made on a YBa2Cu3O7-δ crystal, initially cooled to 4.2 K in an external field He parallel to the c axis. With He fixed, the crystal was then tilted, such that the angle θ between the c axis and He was gradually raised to 90° and lowered back to zero. Our results reveal that all the vortex flux remains parallel to the c axis until the tilt angle θ reaches a threshold value (close to 15° for Hevalue, the vortex flux in the ab plane rises rapidly from zero, and it appears to derive solely from a bending of the vortices initially directed along c. This whole process is fairly consistent with theoretical predictions, and it is found to be essentially reversible with the cycling of θ at low He. The hysteresis that develops at higher He rises and approaches the conventional hysteresis measured along ab after zero-field cooling. Comparison is also made with a cross-flux experiment, which is seen to be only superficially equivalent to the crystal-tilt experiment.

  14. Study of growth kinetics in melt-textured YBa2Cu3O7-x

    International Nuclear Information System (INIS)

    Athur, S.P.; Selvamanickam, V.; Balachandran, U.; Salama, K.

    1996-01-01

    Directional solidification has been shown to be a successful way of achieving high current densities in bulk YBCO. The lack of understanding of the growth kinetics, however, makes it difficult to fabricate longer samples and reduce the processing times. To study the growth kinetics, quenching experiments of undoped YBa 2 Cu 3 O 7-x (Y-123) and Y-123 doped with Pt and Nd from above the peritectic temperature with different holding times, t, were conducted. The results of these experiments indicate that the average 211 particle size varies as t 1/3 . Growth rate experiments were also conducted on these samples to determine the maximum growth rate for plane front solidification, R max . This quantity was measured for undoped and doped Y-123 and its was found that the addition of Pt did not increase R max while the addition of Nd doubled the growth rate. Using the coarsening results together with the growth rate experiments, the diffusivity of Y in liquid and the 211-liquid interfacial energy for undoped and doped Y-123 were calculated. copyright 1996 Materials Research Society

  15. Effect of cobalt doping on thermal conductivity of YBa2Cu3O7-δ superconductor

    International Nuclear Information System (INIS)

    Suleiman, B.M.; Boerjesson, L.; Berastegui, P.

    1996-01-01

    The thermal conductivity of YBa 2 Cu 3 O 7-δ and YBa 2 Cu 3-x Co x O 7-δ (x=0.1) sintered compounds has been measured to investigate the effect of Co doping on the thermal conduction processes. The measurements were performed using the transient-plane-source technique. The thermal conductivity of the doped sample qualitatively resembles that of the corresponding undoped sample, but with values a factor of 2 lower. This decrease in thermal conductivity is attributed to scattering mechanisms due to enhancement of the microstructural imperfections and the decoupling between the conducting Cu-O planes as a result of Co-doping in the chain sites. An attempt was made to interpret the peak of the thermal conductivity below T c in terms of a theoretical model based on weakly damped collective electron excitations of the Bose type, with an acoustic dispersion relation (acoustic plasmons), inside the superconducting gap 2Δ(T). copyright 1996 The American Physical Society

  16. Imaging of magnetic flux states in YBa2Cu3O7-δ grain boundary junctions

    International Nuclear Information System (INIS)

    Mayer, B.; Shen, Y.; Vase, P.

    1993-01-01

    The weak link behavior of grain boundaries in the high temperature superconductors has been studied intensively during the last years. On the one hand the weak link nature of the grain boundaries is responsible for the disappointingly low critical current densities in polycrystalline materials. However, on the other hand it offers the possibility to fabricate Josephson elements required for microelectronic applications of the cuprate superconductors. Although various types of artificially generated, so-called engineered grain boundary Josephson junctions (GBJs) have been fabricated and characterized with respect to their structural and electrical properties there are still open questions concerning the weak link nature of high-T c GBJs. As a consequence of the weak link nature the supercurrent density of the GBJs should be spatially modulated, if magnetic flux is coupled into the grain boundary by a magnetic field applied parallel to the grain boundary plane. We report on direct measurements of the spatially modulated supercurrent density in YBa 2 Cu 3 O 7-δ bicrystal GBJs using Low Temperature Scanning Electron Microscopy (LTSEM). The LTSEM images directly show the spatial oscillation of the supercurrent density J s along the grain boundary with a resolution of about 1 μm. Varying the applied magnetic field different magnetic flux states containing up to 10 Josephson vortices could be observed. (orig.)

  17. Angular dependence of the irreversible magnetization of YBa2Cu3O7 superconducting thin films

    International Nuclear Information System (INIS)

    Thrane, B.P.; Schlenker, C.; Dumas, J.; Buder, R.

    1996-01-01

    YBa 2 Cu 3 O 7 superconducting thin films have been studied by magnetization measurements in oblique fields up to 0.8 T both at low temperature and at temperatures close to T c . Both components of magnetization parallel and perpendicular to the applied field could be measured with two pairs of crossed detection coils. In all cases the magnetization is found to be perpendicular to the film plane. This is due to the self-field effects related to the thin-film geometry which force the critical currents to circulate along the film plane. At low temperature the properties are found to depend only on the component of the applied magnetic field perpendicular to this plane, as expected in the situation where demagnetizing field effects are dominant. However, at temperatures close to T c the critical currents and therefore the pinning are found to increase when the applied field approaches the film plane. This is attributed to the effect of intrinsic pinning which may be related to the kink structure of the vortices in oblique fields. copyright 1996 The American Physical Society

  18. Calorimetric measurements of YBa2Cu3O7-δ at low temperatures

    International Nuclear Information System (INIS)

    Schreiner, T.

    1992-01-01

    The first part of this thesis (Chap. II and III) describes the construction and functioning of an apparatus for measuring the specific heat, designed for small samples and for use in a top-loading dilution refrigerator. Automatic measurements are possible in the temperature range between 30 mK and 3 K with magnetic fields up to 12 Tesla. The accuracy of the calorimeter was verified by test measurements with copper. The second part (Chap. IV and V) presents measurements performed on an YBa 2 Cu 3 O 7-δ single crystal in the temperature range from 38 mK to 3 K and with magnetic fields up to 11.2 Tesla. Among others the nuclear contribution, the contribution of the lattice, as well as a possible linear term in the specific heat are discussed. At low temperatures and in high magnetic fields a non-exponential relaxation behavior was found, which is presumably due to a weak coupling of the nuclear moments to the lattice. (orig.)

  19. Flux motion and anisotropy in melt-processed YBa2Cu3O7

    International Nuclear Information System (INIS)

    Koblischka, M.R.; Schuster, Th.; Kuhn, H.; Gluecker, M.; Dalen, A.J.J. van; Griessen, R.; Kronmueller, H.

    1993-01-01

    The melt-processing of YBa 2 Cu 3 O 7-δ - and Bi 2 Sr 2 CaCu 2 O 8+δ -samples offers a promising way to achieve high critical current densities also in bulk materials. This is of main interest for strong current applications of high-T c superconductors. Interesting basic features can also be studied using melt-processed samples, from which good quality crystals can be cut out. For example, such samples make it possible to do measurements in various angular positions without drastically changing the demagnetizing factors along the main crystallographic axes. Usually, most measurements studying the influence of intrinsic pinning have been carried out on thin films (1). To observe flux distributions in superconductors, we use the High Resolution Faraday (HRF) technique. This enables one to local observations of flux distributions, combining a high spatial resolution (∼0.8 μm) with the unique possibility to observe dynamic processes in the flux distribution such as flux motion due to flux creep (2,3). Additionally, torque measurements up to 7 T in the temperature range 10 - 77 K have been carried out on the identical sample for a comparison of the local HRF data with integral critcal current torque data. (orig.)

  20. Atomistic simulation of ionic and electronic defects in YBa2Cu3O7

    International Nuclear Information System (INIS)

    Baetzold, R.C.

    1988-01-01

    An empirical two-body potential model has been developed in order to describe the electronic and ionic defect properties of orthorhombic YBa 2 Cu 3 O 7 . The potential model was derived starting from known potentials and calculated potentials and fits the crystal structure to better than 0.03 A for the major bonds. Oxygen vacancy formation and hole trapping as a localized polaron are most favorable at the chain oxygen ion site 1. Hole trapping on Cu + ions is most favorable for ions in the copper-oxygen plane. Divalent impurity ions such as Ni/sup 2+/, Zn/sup 2+/, and Cd/sup 2+/ can dissolve in the crystal preferentially at the Cu/sup 2+/ plane site 2. On the other hand, trivalent impurities such as Al/sup 3+/, Fe/sup 3+/, and Ga/sup 3+/ dissolve in the crystal at the chain Cu/sup 2+/ site 1 along with the incorporation of oxygen ions. Anions such as S/sup 2-/, Cl - or F - would preferentially substitute for O/sup 2-/ at sites near the Cu/sup 2+/ chain position

  1. Electronic structure of twin boundaries in YBa2Cu3O7

    International Nuclear Information System (INIS)

    Agassi, D.; Kasowski, R.V.

    1991-01-01

    The electronic structure of a twin boundary (TB) in YBa 2 Cu 3 O 7 is evaluated from ab initio band-structure calculations. Two models are considered: The first assumes the ideal TB atomic configuration. The oxygen-disordered TB model, on the other hand, assumes that in proximity to the TB the oxygen atoms relocate randomly to vacant lattice sites such that the Cu-O bond length is preserved. The calculations have been carried out using 52-atom and 78-atom supercells. For the ideal TB model, the TB presence gives rise to a quasicontinuum of localized states near E F . These states do not contribute to the conductivity. For the oxygen-disordered TB model, two representative oxygen dislocations are considered: One in which a chain oxygen [O(1)] is displaced in the basal plane, and the other in which a Cu-plane oxygen [O(2), O(3)] is up-displaced into the yttrium plane. For both configurations we find conductive pathways with energy near E F . These pathways are comprised of zigzag Cu-O chains, oriented in all directions parallel to the TB plane. This model implies, in particular, percolative conduction in the c-axis direction parallel to the TB planes

  2. Electron beam induced oxygen in YBa2Cu3O7-x superconductors

    International Nuclear Information System (INIS)

    Basu, S.N.; Roy, T.; Mitchell, T.E.; Nastasi, M.

    1989-01-01

    Thin foils of bulk YBa 2 Cu 3 O 7-x (YBCO) superconductors were subjected to electron irradiation in a Transmission Electron Microscope (TEM). The resulting disordering of the oxygen atoms and vacancies in the Cu-O planes was monitored by measuring the splitting of the (110) diffraction spots in the [001] diffraction pattern. Samples were irradiated at 83K with 100, 150, 200 and 300kV electrons. The 100kV electrons did not cause any disordering, even after prolonged irradiation. The results of the higher energy irradiations showed an excellent fit to a disordering model, indicating a lack of radiation assisted ordering at 83K. This was further confirmed by the insensitivity of the disordering to the dose rate of 300kV electrons at 83K. However, at 300K, an increase in the dose rate of 300kV electrons increased the disordering rate, indicating that radiation assisted reordering was occurring at that temperature. 7 refs., 4 figs

  3. Structure and flux pinning properties of irradiation defects in YBa2Cu3O7-x

    International Nuclear Information System (INIS)

    Kirk, M.A.

    1992-06-01

    We review our investigations of defects produced in YBa 2 Cu 3 O 7-x by various forms of irradiation. The defect microstructure has been studied by transmission electron microscopy (TEM). Irradiation enhancements of flux pinning have been studied by SQUID magnetometry on single crystals. In many cases the same single crystals were used in both TEM and SQUID investigations. The primary atom recoil spectra for all the irradiations studied have been carefully calculated and used to correlate the TEM and magnetization results for the different types of irradiation. Correlation of annealing experiments, employing both TEM and SQUID measurements, among several types of irradiation has also yielded information on the different defect structures present. Defect densities, sizes and strain field anisotropies have been determined by TEM. Defect flux pinning anisotropies have been determined for two field orientations in twinned single crystals. The temperature dependences of the flux pinning have been measured. The maximum field of irreversibility at 70 K is shown to change markedly upon both neutron and proton irradiations in some crystals and not others. The defect structure, chemistry and location in the unit cell has been determined in some cases. Some interaction with existing defect structure has been observed in proton and electron irradiations. The damage character and directionality has been determined in GeV ion irradiated crystals

  4. Paramagnetic moments in YBa2Cu3O7−δ nanocomposite films

    International Nuclear Information System (INIS)

    Dias, F.T.; Vieira, V.N.; Silva, D.L.; Albino Aguiar, J.; Valadão, D.R.B.; Obradors, X.; Puig, T.; Wolff-Fabris, F.; Kampert, E.

    2014-01-01

    Highlights: • The paramagnetic Meissner effect was observed in a nanocomposite YBaCuO thin film. • The paramagnetic moments in FC experiments were observed up to 10 T. • The paramagnetic Meissner effect increases when the magnetic field is increased. • Results may be explained based on the flux compression scenario and vortex pinning. • An apparent saturation tendency of the paramagnetic moments could be observed. - Abstract: We report on magnetization studies in YBa 2 Cu 3 O 7−δ thin films with dispersed Ba 2 YTaO 6 nanoparticles. The magnetization measurements were made using a superconducting quantum interference device (SQUID) and a vibrating sample magnetometer (VSM). Magnetic moments were measured as functions temperature using zero-field cooling (ZFC) and field-cooled (FC) prescriptions for magnetic fields up to 10 T applied parallel and perpendicular to the ab planes. A paramagnetic response related to the superconducting state was observed during the FC experiments. This effect, known as paramagnetic Meissner effect (PME), apparently increases when the magnetic field is increased. We discuss our PME results in terms of the strong pinning scenario modulated by Ba 2 YTaO 6 nanoparticles dispersed into the superconducting matrix

  5. Electron beam induced oxygen disordering in YBa2Cu3O7-x superconductors

    International Nuclear Information System (INIS)

    Basu, S.N.; Roy, T.; Mitchell, T.E.; Nastasi, M.

    1990-01-01

    Thin foils of bulk YBa 2 Cu 3 O 7-x (YBCO) superconductors were subjected to electron irradiation in a transmission electron microscope (TEM). The resulting disordering of the oxygen atoms and vacancies in the Cu-O planes was monitored by measuring the splitting of the (110) diffraction spots in the [001] diffraction pattern. Samples were irradiated at 83 K with 100, 150, 200 and 300 kV electrons. The 100 kV electrons did not cause any disordering, even after prolonged irradiation. The results of the higher energy irradiations showed an excellent fit to a disordering model, indicating a lack of radiation assisted reordering at 83 K. This was further confirmed by the insensitivity of the disordering to the dose rate of 300 kV electrons at 83 K. However, at 300 K, an increase in the dose rate of 300 kV electrons increased the disordering rate, indicating that radiation assisted reordering was occurring at that temperature

  6. Flux creep and penetration in Fe-doped YBa2Cu3O7

    International Nuclear Information System (INIS)

    Mohamed, M.A.; Jung, J.; Franck, J.P.

    1990-01-01

    Measurements of the magnetic-field distribution, flux penetration, and decay of trapped flux were performed for a disc-shaped sample of YBa 2 Cu 2.95 Fe 0.05 O 7-δ at 77 K. Time-dependent magnetic-flux penetration, i.e., a decay of diamagnetic shielding and the Meissner field, was observed for zero-field-cooled (ZFC) and field-cooled (FC) samples. The decays were found to be logarithmic in time. The logarithmic decay rate of diamagnetic shielding depends on an applied magnetic field and reaches its maximum at an applied field of about 30 G. The dependence of a trapped field versus an applied field shows a maximum at an applied field of 100 G for the FC case and 200 G for the ZFC case. The maximum amount of the trapped field is about two times less than that for a pure, undoped YBa 2 Cu 3 O 7-δ sample of similar dimensions. The logarithmic decay rate of the trapped field versus the initial trapped field is described by a linear function with the change of its slope at the trapped field corresponding to an applied field of about 30 G for both the FC and ZFC cases. These results are related to the sample microstructure, i.e., grain size and porosity. Trapped field decays can be explained in terms of the interaction between intergranular vortices and persistent current circulating around normal regions or voids, in the framework of the conventional flux-creep model recently proposed by Hagen, Griessen, and Salomons [Physica 157C, 199 (1989)

  7. Noise measurements of YBa2Cu3O7 thin film high-temperature superconductors

    International Nuclear Information System (INIS)

    Hall, J.J.

    1992-01-01

    The characteristics of thin-film YBa2Cu3O7 superconductors were studied from the superconducting region through the transition region and into the normal region. The properties studied included the resistance-temperature, current-voltage, and electrical noise with concentration of measurements in the transition region. The resistance vs. temperature measurements show a zero resistance followed by a small rise in magnitude at the onset of resistance followed by a sharp increase until the resistance tapers off in the fully normal region. The a-axis films had a larger normal resistivity, a lower critical temperature, and a broader transition than the similar c-axis films. The current(I) - voltage(V) measurements were concentrated in the transition region. A power relation between I and V was found to be V varies as I a(T) where a(T) is temperature dependent starting high the onset of vortex formation, approaches 3 at the vortex unbinding temperature, and goes to 1 when fully normal. This behavior was predicted by the Kosterlitz-Thouless theory and was found experimentally in all four films measured. The current-induced electrical noise characteristics were measured for four samples varying in thickness and axis orientation. Each film exhibited a widely varying magnitude of the noise voltage spectral density (S V ) in the transition region with a leveling off when fully normal. The normalized noise (S V /V squared) showed a sharp decrease in magnitude from the onset of measurable noise continually decreasing until flattening out when fully normal. The a-axis films exhibited S V /V squared over 3 order of magnitude larger than the c-axis films in the transition and normal regions. The normalized temperature coefficient of resistance (beta) was plotted against S V /V squared on a log-log scale to see if the noise generated was due to temperature fluctuations (slope = 2)

  8. Study Of Hysteresis Curve Characteristic On The YBa2Cu3O7-x Superconductor

    International Nuclear Information System (INIS)

    Adi, Wisnu; S W, Didin; Purwanto S; Yamaguchi, Yasuo

    2003-01-01

    The measurements of magnetic moment (m) on the superconductor YBa 2 Cu 3 O 7-x as function of temperature (T) and applied magnetic field (H) have been performed by using superconducting quantum interference device magnetometer (SQUID). The samples measured consist of pellet from sintering and melting products. The m-T curve is used to measure critical temperature (Tc), and the m-H curve is used to measure critical field, critical current density, and pinning force. Analysis results of both curves found that Tc is about 90.16 K and 90,15 K for samples of sintering and melting products, respectively. Hc 2 and Hc 2 of both samples are 1 k Oe and 20 k Oe, respectively. J c (H = 0) are 1.88 x 10 2 A.cm -2 ; 2.80 x 10 4 A.m -2 ; 2.02 x 10 3 A.m -2 ; and 5.70 x 10 5 A.cm -2 for Y S-2 (T = 77 K), Y S-2 (T = 5 K), Y M-2 (T = 77 K), and Y M-2 (T = 5 K) products, respectively. The F p maximum are 5.8 x 10 5 Nm -3 (H = 17 k Oe); 2.1 x 10 8 Nm -3 (H = 17 k Oe); 5.1 x 10 6 Nm -3 (H = 14 k Oe); and 8.3 x 10 9 Nm -3 (H = 14 k Oe) for Y S-2 (T = 77 K), Y S-2 (T= 5 K), Y M-2 (T= 77 K), and Y M-2 (T= 5 K), respectively

  9. Deposition, characterization, and electronic applications of YBa2Cu3O7 thin films

    International Nuclear Information System (INIS)

    Kromann, R.

    1992-09-01

    YBa 2 Cu 3 O 7 thin films were deposited by rf sputtering and laser ablation. In the case of rf sputtering the presence of negative oxygen ions was found to give rise to severe resputtering effects. In contrast, laser ablation is found to be a much simpler and more reliable depostion method. Structural characterization in the form of an X-ray diffraction study of the structure of laser ablated YBCO thin films is reported. Two films on MgO differing by 75% in the critical current density were examined. The difference was ascribed to the fact that about 5% of the grains in the low J c film grow 45 deg. misoriented with respect to the dominant orientation in the a-b plane. Two other films on SrTiO 3 differing by 70% in J c were examined. Various ways of achieving a 45 deg. grain boundary by a biepitaxial process on MgO substrates are described. The grain boundary junctions are used to fabricate DC SQUIDs. It is demonstrated that the SQUIDs exhibit critical current modulation in a magnetic field at temperatures up to 80 K. It is shown that the 1/f noise can be reduced by a factor of 3 by the double modulation technique, indicating that the dominant contribution to the 1/f noise comes from critical current fluctuations. The high level of 1/f noise from critical current fluctuations is ascribed to the nature of the 45 deg. grain boundary and it is argued that it is necessary to develop a bi-epitaxial process for grain boundaries with angles less than 45 deg.. Finally, it is demonstrated that a SQUID and a flux transformer can be fabricated on the same substrate to form an integrated magnetometer. (au) (8 tabs., 58 ills., 97 refs.)

  10. YBa2Cu3O7-x thin films prepared by chemical solution deposition

    International Nuclear Information System (INIS)

    Apetrii, Claudia

    2009-01-01

    The discovery of superconductivity in ceramic materials by Bednorz and Mueller in early 1987, immediately followed by Wu et al., who showed that YBa 2 Cu 3 O 7-x (YBCO) becomes superconducting (92 K) well above the boiling point of nitrogen (77 K) created a great excitement in superconductivity research. Potential applications of high T c -superconductors require large critical currents and high-applied magnetic fields. Effective ways to increase the critical current density at high magnetic fields in YBCO are the introduction of nanoparticles and chemical substitution of yttrium by other rare earth elements. Since low costs and environmental compatibility are essential conditions for the preparation of long length YBCO films, the cost effective chemical solution deposition (CSD) procedure was selected, given that no vacuum technology is required. To reveal the flexibility and the good optimization possibilities of the CSD approach two main processes were chosen for comparison: a fluorine-free method, namely the polymer-metal precursor technique, and a fluorine-based method, the metalorganic deposition (MOD) using the trifluoroacetates (TFA) technique. Sharp transition temperature widths ΔT c of 1.1 K for the polymer metal method, 0.8 K for TFA method and critical current densities J c of ∼3.5 MA/cm 2 shows that high quality YBCO thin films can be produced using both techniques. Especially interesting is the magnetic field dependence of the critical current density J c (B) of the Y(Dy)BCO (80 %) films showing that for the lower magnetic fields the critical current density J c (B) is higher for a standard YBCO film, but at fields higher than 4.5 T the critical current density J c (B) of Y(Dy)BCO is larger than that for the YBCO. Above 8 T, J c (B) of the Y(Dy)BCO film is more than one order of magnitude higher than in pure YBCO film. (orig.)

  11. PROCESAMIENTO EN DESCARGA LUMINISCENTE DE LA PEROVSKITA YBa2Cu3O7-d

    Directory of Open Access Journals (Sweden)

    UBEIMAR FUENTES GUERRERO

    2011-01-01

    Full Text Available La aplicación de la descarga luminiscente anormal al proceso de sinterización es una técnica reciente que representa disminución en el tiempo requerido para el proceso de sinterización de muestras, tanto metálicas como cerámicas, y un menor consumo de energía, debido a que el calentamiento se realiza en forma directa por el bombardeo de los iones y átomos neutros sobre la superficie del cátodo donde generalmente se localiza la muestra. En este trabajo se estudia la aplicación de la descarga luminiscente anormal de baja presión como método alternativo para realizar la etapa de sinterización del material cerámico YBa2Cu3O7-, se comparan la estructura y la microestructura de muestras sinterizadas en la descarga luminiscente con las de muestras sinterizadas en horno resistivo, el cual es comúnmente utilizado para la producción de este tipo de materiales. Para ello se realiza el análisis estructural y morfológico por DRX y SEM, respectivamente, de las muestras obtenidas por los dos procedimientos. Los resultados experimentales permitieron establecer una estructura similar para ambos casos y una menor porosidad superficial en las muestras sinterizadas por plasma. Además, en el proceso de sinterización por plasma se observa una ligera contaminación de la superficie de las muestras debida a la pulverización catódica, la cual es fácilmente eliminada por métodos mecánicos.

  12. Josephson edge junctions on YBa2Cu3O7 thin films prepared with Br-ethanol etching

    International Nuclear Information System (INIS)

    Faley, M.I.; Poppe, U.; Daehne, U.; Goncharov, Yu.G.; Klein, N.; Urban, K.; Soltner, H.

    1993-01-01

    To produce damage-free edges is one of the main problems in the preparation of the Josephson edge-type junctions and interconnects in multilayer structures including high temperature superconductors. The commonly used ion beam etching has the disadvantages of the risk of contamination by redeposited material and structural damage to the surface of the edge. Vasquez et al and Gurvitch et al introduced a nonaqueous Br-ethanol etching for the preparation of clean surfaces of YBa 2 Cu 3 O 7 single crystals and thin films. We have developed a procedure of deep-UV-photolithography combined with nonaqueous Br-ethanol etching for the preparation of the Josephson edge-type junctions. Here we present the improvement of this method and report further results on the study of the electron transport properties of Josephson junctions with the edges of YBa 2 Cu 3 O 7 thin films produced by this technique. (orig.)

  13. Microwave properties of YBa2Cu3O7-δ/PrBa2Cu3O7-δ superlattices

    International Nuclear Information System (INIS)

    Carlos, W.E.; Kaplan, R.; Lowndes, D.H.; Norton, D.P.

    1992-01-01

    We have used non-resonant microwave absorption to study c-axis YBa 2 Cu 3 O 7-δ /PrBa 2 Cu 3 O 7-δ superlattices and compare the response to a film of similarly grown YBa 2 Cu 3 O 7-δ (YBCO). Near the respective transition temperatures, the response of the superlattice samples and the YBCO film have similar amplitudes and orientation dependences. This is consistent with the microwave loss being related to magnetic flux penetration at (110) slip planes. At lower temperatures, the response of the superlattices is much stronger than that of the YBCO film and, while both responses are hysteretic at low temperatures, the widths of the hysteresis have opposite orientation dependences, which we attribute to the role of the PrBa 2 Cu 3 O 7-δ layers. (orig.)

  14. Determination of oxygen content and carbonate impurity in YBa2Cu3O7-x by diffuse reflectance infrared spectroscopy

    International Nuclear Information System (INIS)

    Merzbacher, C.I.; Bonner, B.P.

    1991-01-01

    Samples of YBa 2 Cu 3 O 7-x with x ranging from ∼0 to 0.65 have been analyzed by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) in the midinfrared region (400--6000 cm -1 ). Spectral line shapes vary gradually as a function of oxygen stoichiometry, and the reflectance at 400 and 1000 cm -1 decreases linearly with decreasing oxygen content. Spectra of samples that were incompletely synthesized or exposed to a 4% CO 2 atmosphere at 650 degree C clearly indicated the presence of carbonate. DRIFTS is therefore a quick, nondestructive method for determining oxygen content in YBa 2 Cu 3 O 7-x powders, and for detecting carbonate species due to synthesis error or reaction with CO 2 -bearing atmosphere

  15. Epitaxial YBa2Cu3O7 films on rolled-textured metals for high temperature superconducting applications

    International Nuclear Information System (INIS)

    Norton, D.P.; Park, C.; Prouteau, C.

    1998-04-01

    The epitaxial growth of high temperature superconducting (HTS) films on rolled-textured metal represents a viable approach for long-length superconducting tapes. Epitaxial, 0.5 microm thick YBa 2 Cu 3 O 7 (YBCO) films with critical current densities, J c , greater than 1 MA/cm 2 have been realized on rolled-textured (001) Ni tapes with yttria-stabilized zirconia (YSZ)/CeO 2 oxide buffer layers. This paper describes the synthesis using pulsed-laser deposition (PLD) of epitaxial oxide buffer layers on biaxially-textured metal that comprise the so-called rolling-assisted biaxially-textured substrates (RABiTs trademark). The properties of the buffer and YBa 2 Cu 3 O 7 films on rolled-textured Ni are discussed, with emphasis given to the crystallographic and microstructural properties that determine the superconducting properties of these multilayer structures

  16. Fluctuation-induced conductivity in melt-textured Pr-doped YBa2Cu3O7-δ composite superconductor

    DEFF Research Database (Denmark)

    Opata, Yuri Aparecido; Monteiro, João Frederico Haas Leandro; Siqueira, Ezequiel Costa

    2018-01-01

    In this study, the effects of thermal fluctuations on the electrical conductivity in melt-textured YBa2Cu3O7-δ, Y0.95Pr0.05Ba2Cu3O7-δ and (YBa2Cu3O7-δ)0.95–(PrBa2Cu3O7-δ)0.05 composite superconductor were considered. The composite superconductor samples were prepared through the top seeding method...... using melt-textured NdBa2Cu3O7-d seeds. The resistivity measurements were performed with a low-frequency, low-current AC technique in order to extract the temperature derivative and analyze the influence of the praseodymium ion on the normal superconductor transition and consequently on the fluctuation...

  17. Anisotropic strain in YBa2Cu3O7-δ films analysed by deconvolution of two-dimensional intensity data

    International Nuclear Information System (INIS)

    Broetz, J.; Fuess, H.

    2001-01-01

    The influence of the instrumental resolution on two-dimensional reflection profiles of epitaxic YBa 2 Cu 3 O 7-δ films on SrTiO 3 (001) has been studied in order to investigate the strain in the superconducting films. The X-ray diffraction intensity data were obtained by two-dimensional scans in reciprocal space (q-scan). Since the reflection broadening caused by the apparatus differs for each position in reciprocal space, a highly crystalline substrate was used as a standard. Thus it was possible to measure a standard very close to the YBa 2 Cu 3 O 7-δ reflections in reciprocal space. The two-dimensional deconvolution of reflections by a new computer program revealed an anisotropic strain of the two twinning systems of the film. (orig.)

  18. Electrical and percolative behavior of Sr2YSbO6-YBa2Cu3O7-δ composites

    International Nuclear Information System (INIS)

    Ortiz-Diaz, O.; Landinez Tellez, D.A.; Perez, F.; Tovar, H.; Roa-Rojas, J.

    2007-01-01

    We found that a mixture of materials Sr 2 YSbO 6 insulator with YBa 2 Cu 3 O 7-δ superconductor is a system where the particles of superconductor and insulator materials are found coexisting in a composite with two well-defined separate phases. Electrical transport properties and percolation behavior have been studied by electrical resistivity measurements at room temperature on several samples of composites with different vol.% of YBa 2 Cu 3 O 7-δ . Resistivity measurements agree with the equation which describes the conductivity in percolation theory. However, critical exponent t=6.65 is greater than universal value t∼2. Furthermore, there is a non-negligible conductivity below percolation threshold while it is expected to be zero in ideal percolative systems. Nevertheless, percolative behavior in this region was found and, critical exponent value s was determined to be s=0.75 in agreement with universal value

  19. Preparation of YBa2Cu3O7-x precursors from a fused eutectic of sodium and potassium hydroxides

    International Nuclear Information System (INIS)

    Coppa, N.; Nichols, D.H.; Schwegler, J.W.; Crow, J.E.; Myer, G.H.; Salamon, R.E.

    1989-01-01

    A method for preparing YBa 2 Cu 3 O 7-x from the simultaneous thermal decomposition of the nitrates of yttrium, barium, and copper in an anhydrous fused eutectic of sodium and potassium hydroxide is described. This method eliminates the need for any mechanical grinding or the introduction of carbon containing anions. Products formed are fine powders (∼1 μm) having mole ratios 1.00 Y:2.00 Ba:3.06 Cu. X-ray diffraction analysis reveal that the initial products are Y(OH) 3 , BaO 2 , and CuO, which when air calcinated/ oxygen annealed at 900--950 degree C form the superconducting YBa 2 Cu 3 O 7-x . A mechanism is postulated for product formation as a function of reaction conditions

  20. Anisotropic electrical properties of epitaxial Yba2Cu3O7-gd films on (110) SrTiO3

    International Nuclear Information System (INIS)

    Gupta, A.; Koren, G.; Baseman, R.J.; Segmuller, A.; Holber, W.

    1989-01-01

    Epitaxial thin films of YBa 2 Cu 3 O 7 - δ were deposited on (110) SrTiO 3 at 600 degrees C in the presence of atomic oxygen using the laser ablation technique. X-ray diffraction patterns in the standard Bragg and grazing incidence modes show epitaxial growth of the films with their c-axis and axis parallel to the and directions in the plane of the substrate, respectively. Superconductivity with T c (R = ) = 82 K was found along the direction in the basal plane, whereas finite resistivity down to 5 k was observed along the c-axis direction. The authors maintain that these preliminary results suggest that YBa 2 Cu 3 O 7 - δ behaves like a true two-dimensional superconductor

  1. Properties of all YBa2Cu3O7 Josephson edge junctions prepared by in situ laser ablation deposition

    International Nuclear Information System (INIS)

    Koren, G.; Aharoni, E.; Polturak, E.; Cohen, D.

    1991-01-01

    Thin-film YBa 2 Cu 3 O 7 -YBa 2 Cu 3 O 7 edge junctions of 0.4x10 μm 2 cross section were prepared in situ by a multistep laser ablation deposition process. The fabrication time was about 3 h and the yield of good devices was 50%. Typical junctions reached zero resistance at 72 K and had a critical current density J c of 300 A/cm 2 at 70 K. Their J c as a function of temperature increased slowly with decreasing temperature down to 65 K and much faster below it. In the region of low J c we observed suppression of the critical current by a magnetic field. Under microwave radiation clear Shapiro steps were observed whose magnitude versus the microwave field agreed qualitatively with the resistively shunted junction model of a current biased junction

  2. High-speed photography of laser ablation plasmas from the high temperature superconductor YBa2Cu3O7

    International Nuclear Information System (INIS)

    Scott, K.; Huntley, J.M.; Phillips, W.A.

    1993-01-01

    The luminous plume formed by laser ablation of the high-temperature superconductor YBa 2 Cu 3 O 7-δ has been investigated using high-speed framing photography. Variation of the background oxygen pressure was found to significantly influence the velocity distribution of the ablated species, leading in particular to shock wave formation and instabilities on the shock front at higher pressures. Spectral characteristics of the plume were studied using optical interference filters, and two distinct regions of emission were identified. (orig.)

  3. Scanning tunneling microscope investigation of (100) and (001) faces of YBa2Cu3O7/sub -//sub δ/

    International Nuclear Information System (INIS)

    Niedermann, P.; Scheel, H.J.; Sadowski, W.

    1989-01-01

    Thin as-grown side faces, and edge and corner regions of crystals of the tetragonal precursor phase of the high-temperature superconductor YBa 2 Cu 3 O 7 /sub -//sub δ/ were studied by scanning tunneling microscopy under scanning electron microscope control of tip positioning. From observed changes in slope of the (100) surface, in particular near the (100)/(001) edges, it was concluded that the (100) and (001) faces have different growth mechanisms

  4. Influence of vanadium substitution on structure and critical currents of YBa2Cu3O7

    International Nuclear Information System (INIS)

    Jadhav, K.M.; Raibagkar, R.L.

    1995-01-01

    V-doped YBa 2 Cu 3 O 7-δ samples prepared under identical conditions have been investigated by magnetization measurements as a function of temperature and field. The critical current density, J c has been deduced from the hysteresis data, using the appropriate field window within which a linear relationship between ΔM(H) and J c is valid. (author). 7 refs., 4 figs., 1 tab

  5. Effect of sintering time on the orthorhombic structure and positron lifetime in YBa2Cu3O7

    International Nuclear Information System (INIS)

    Chen Zhenping; Zhang Jincang; Li Xigui

    2002-01-01

    The effects of sintering time on the orthorhombic structure and positron lifetime parameter in YBa 2 Cu 3 O 7-δ have been studied by XRD, SEM and the positron experiments. It is found that on the condition of 950 degree C/12-72 h, the positron experiment has good stability and reliability. This experiment indicates that the longer sintering time is needed to prepare Y-123 samples

  6. Annihilation of positrons with localized electrons in oxides and YBa2Cu3O7-x ceramics

    International Nuclear Information System (INIS)

    Nishchenko, M.M.; Likhtorovich, S.P.

    1997-01-01

    The angular correlation of annihilation photons (ACAP) has been studied in CuO, Cu 2 O,BaO,Y 2 O 3 and YBa 2 Cu 3 O 7-x oxides. Localization radius of the electron wave function is found to be about 0,8 A. It is also shown that with the more localization of the electron its probability of annihilation with positrons is less

  7. Influence of inductance induced noise in an YBa2Cu3O7 dc-SQUID at high operation temperatures

    DEFF Research Database (Denmark)

    Nilsson, P. Å.; Claeson, T.; Hansen, J. B.

    1994-01-01

    The voltage modulation depth of a high T(c) dc-SQUID was measured at temperatures close to T(c) and compared to a model by Enpuku et al. where the flux noise from the SQUID inductance is taken into account. The device was an YBa2Cu3O7 dc-SQUID made on a bicrystal substrate of SrTiO3. The design w...

  8. Influence of planar macrodefects on the anisotropy of magnetic-flux penetration in YBa 2Cu 3O 7

    Science.gov (United States)

    Cuche, E.; Indenbom, M. V.; André, M.-O.; Richard, P.; Benoit, W.; Wolf, Th.

    1996-02-01

    The magnetic flux penetration in a high-quality YBa 2Cu 3O 7-δ single crystal with an external field applied perpendicular to the crystalline c axis is directly visualized by means of the magneto-optical technique. The observations show that the field penetrates preferentially along the ab planes. Scanning acoustic microscopy reveals macrodefects along ab planes which strongly affect this anisotropy of the field penetration.

  9. Surface electric resistance of YBa2Cu3O7-δ ceramics and its dependence on magnetic field

    International Nuclear Information System (INIS)

    Gorochev, O.A.; Graboj, I.Eh.; Kaul', A.R.; Mitrofanov, V.P.

    1989-01-01

    Method of dielectric resonator in the 4.2-300 K temperature range is used to measure surface electric resistance of YBa 2 Cu 3 O 7-δ ceramics samples produced by different technologies. The temperature dependence of surface resistance near transition temperature is calculated. At 77.3 K dependence of electric resistance on external magnetic field at H≤200Oe is determined. Calculated dependence is verified in experiment

  10. Femtosecond optical detection of quasiparticle dynamics in high-Tc YBa2Cu3O7-δ superconducting thin films

    International Nuclear Information System (INIS)

    Han, S.G.; Vardeny, Z.V.; Wong, K.S.; Symko, O.G.; Koren, G.

    1990-01-01

    Femtosecond dynamics of photogenerated quasiparticles in YBa 2 Cu 3 O 7-δ superconducting thin films shows, at T≤T c , two main electronic processes: (i) quasiparticle avalanche production during hot-carrier thermalization, which takes about 300 fsec; (ii) recombination of quasiparticles to form Cooper pairs, which is completed within 5 psec. In contrastr, nonsuperconducting epitaxial films such as PrBa 2 Cu 2 O 7 and YBa 2 Cu 3 O 6 show regular picosecond electronic response

  11. Ultrasonic determination of the elastic moduli and their pressure dependences in very dense YBa2Cu3O7-x

    International Nuclear Information System (INIS)

    Cankurtaran, M.; Saunders, G.A.; Goretta, K.C.; Poeppel, R.B.

    1991-12-01

    The effects of hydrostatic pressure and temperature have been measured on the velocities of longitudinal and shear ultrasonic waves propagated in a very dense (96% of theoretical density) ceramic specimen of YBa 2 Cu 3 O 7-x . In YBa 2 Cu 3 O 7-x ceramics with such a high density the effects of porosity on the elastic properties should be much reduced. Nevertheless the bulk modulus of this dense material has the same small magnitude (∼ 55GPa) as that measured ultrasonically in much less dense YBa 2 Cu 3 O 7-x ceramics. The temperature dependences of the velocities of longitudinal and shear ultrasonic waves, which have been measured between 10 K and 300 K, show the step-like increase at 200 K on cooling and a similar decrease at 225 K during warming with hysteresis in the range 190 K to 235 K that has previously been observed in less dense ceramics and tentatively attributed to a phase transformation. The pressure dependences of both mode velocities for dense YBa 2 Cu 3 O 7-x ceramic show a pronounced change of slope at a pressure P c . For pressures below and above P c the pressure dependence of ultrasonic velocity is essentially linear. Above the knee, the enormous pressure dependences of the longitudinal mode velocity and hence of the bulk modulus persist. The temperature dependences of pressure derivatives of elastic stiffnesses and bulk modulus have been measured between 250 K and 295 K. The pressure P c at which the kink occurs decreases almost linearly with decreasing temperature and extrapolates to atmospheric pressure at about 220 K

  12. Magnetic determination of the specific heat jump at Tc in YBa2Cu3O7

    International Nuclear Information System (INIS)

    Triscone, G.; Junod, A.; Muller, J.

    1989-01-01

    Magnetization measurements M(H,T) were performed on a polycrystalline YBa 2 Cu 3 O 7 - δ sample in the reversible region near T c . Thermodynamic relations are used to address the question: is the specific heat jump an intrinsic characteristic property of the electron system at the superconducting transition? It is shown that the measured data up to 8T (rather than extrapolated to H c2 ) already yield 45% of the calorimetric jump

  13. Enhancement of critical current density of YBa2Cu3O7-δ thin films by nanoscale CeO2 pretreatment of substrate surfaces

    International Nuclear Information System (INIS)

    Cui, X.M.; Liu, G.Q.; Wang, J.; Huang, Z.C.; Zhao, Y.T.; Tao, B.W.; Li, Y.R.

    2007-01-01

    YBa 2 Cu 3 O 7-δ (YBCO) films were prepared on single-crystal SrTiO 3 substrates with metal-organic deposition using trifluoroacetates (TFA-MOD). Positive results have been acquired in controlled study to investigate the effects of substrate surface modification on the growth-induced flux-pinning nanostructures in YBCO films. Nanoscale CeO 2 particles were applied to single-crystal SrTiO 3 substrate surfaces using pulsed laser deposition before YBCO precursors coating. Superconducting properties of the YBCO films grown on the controlled CeO 2 -modified substrates have shown substantial improvement in the critical current densities (J c ) at 77 K over those grown on untreated substrates in almost all the field (78% increment at 1 T, 77 K). We think the reason is that the CeO 2 nanoparticles act as pinning centers

  14. A rapid process of Yba2Cu3O7-δ thin film fabrication using trifluoroacetate metal-organic deposition with polyethylene glycol additive

    DEFF Research Database (Denmark)

    Wu, Wei; Feng, Feng; Shi, Kai

    2013-01-01

    Trifluoroacetate metal-organic deposition (TFA-MOD) is a promising technique to fabricate YBa2Cu3O7-δ (YBCO) superconducting films. However, its slow pyrolysis process, which usually takes more than 10 h, constitutes a barrier for industrial production. In this study, polyethylene glycol (PEG......) was utilized to reduce the stress generation inside the coated films when the strong pyrolysis reactions happen. With the addition of 30 wt% PEG2000 to the precursor solution, a smooth film surface could be obtained through a rapid pyrolysis process of 15 min. After the optimizations of the crystallization...... and oxygenation processes, mass percentage and molecular weight of PEG additive, YBCO thin films with Jc of about 4.5 MA cm-2 (77 K, self-field) could be routinely fabricated using (20-30) wt% PEG(1000-2000) additive with a total treatment time of about 2 h including the 15 min pyrolysis process time. The effects...

  15. On possibility of BaCeO3 production when depositing YBa2Cu3O7-χ films on a cerium oxide surface

    International Nuclear Information System (INIS)

    Mashtakov, A.D.; Kotelyanskij, I.M.; Luzanov, V.A.; Mozhaev, P.B.; Ovsyannikov, G.A.; Bdikin, I.D.

    1997-01-01

    Consideration is given to experimental results of investigation into crystallographic parameters of hetero-structural (1102)Al 2 O 3 /(001)CeO 2 (001)YBa 2 Cu 3 O 7-χ films, prepared by the method of cathode sputtering at substrate temperature, equal to 600-800 deg C. It is shown that main limitation for precipitation temperature of YBa 2 Cu 3 O 7-χ film on CeO 2 surface is caused by chemical interaction of YBa 2 Cu 3 O 7-χ with CeO 2 with formation of polycrystalline BaCeO 3 layer

  16. Superconducting thin films of YBa2Cu3O7-x

    International Nuclear Information System (INIS)

    Hudner, J.

    1993-01-01

    Thin films of the high temperature superconductor YBa 2 Cu 3 O 7-x (YBCO) are of significance in fundamental studies of oxide superconductors and for prospected electronic applications based on superconductors operating at liquid nitrogen temperatures (T= 77 K). Synthesis of YBCO thin films is complex and a large part of this thesis has been devoted to the elaboration of various techniques in forming YBCO thin films. A general observation was that synthesis of YBCO films exhibiting high zero-resistivity temperatures temperatures (T c ) ≥ 88 K and elevated critical current densities (J c ) ≥ 10 6 A/cm 2 at 77 K was possible under widely different conditions of film growth. For the BaF 2 -based method, various substrate materials were investigated. Among perovskite related substrates with low losses in the high frequency regime, LaA10 3 was found to yield YBCO films exhibiting the highest quality electrical properties. A study of YBCO film interaction with sapphire substrates was performed. It was suggested that the YBCO film on sapphire consists of weakly coupled superconducting grains. Compositional effects of Y, BA and Cu for MOCVD-YBCO films were examined with respect to morphology, structure, resistivity, as susceptibility and J c (T). High T c :s and J c :s were observed for an anomalous large compositional range of Cu in off-compositional YBCO films. This was shown to be related to the formation of Cu-rich precipitates embedded within a c-Axis oriented stoichiometric YBCO film matrix. Thermal critical current behavior at zero field in thin films of YBCO fabricated by various methods has been studied by three techniques: transport measurements on patterned microbridges, dc magnetization hysteresis loops using the Bean model and non-linear ac susceptibility analysis. Absolute critical current values obtained form the two former techniques when measured on the same YBCO film were observed to differ about a factor of two. The feasibility of non-linear ac

  17. Superconducting properties of modified YBa2Cu3O7-δ ceramics

    International Nuclear Information System (INIS)

    Kaleva, G.M.; Politova, E.D.; Kudinova, M.V.; Prutchenko, S.G.; Venevtsev, Yu.N.

    1993-01-01

    In connection with the promising practical applications of high temperature superconductors (HTSC) particular attention has been paid to studying the influence of dopant elements on the properties of HTSC ceramics. According to earlier work, replacement of the yttrium in the compound YBa 2 Cu 3 O 7-8 (1-2-3) by rare earth elements, excluding Ce, Pr, Tb, and Pm, has almost no influence on the superconducting transition temperature (T c ∼ 90 K). Of the alkaline metals, only Sr will displace Ba over a wide range of concentrations (up to 50 at %), but in this case T c is reduced to 86 K. The strongest influence on the superconducting properties results from replacement of copper by 3d transition metals. Introduction of 10 at.% Zn, Co, Fe, Ni, Ti, Mn, or Cr in place of the copper leads to a drastic lowering of T c . At the same time it has been reported that microadditions of individual elements (replacement of Cu by Pd, Ti, and Fe, at a level of 0.1-0.5 at.%,) may elevate conducting phase and improve the contacts between grains, so that, in particular, there is an increase in the critical current density. In view of the possible positive influence which introduction of small quantities of individual elements may have 1-2-3 compounds, in the present work, the authors have studied the action of dopant additions, including complex ones, on this phase, with the goal of improving its superconducting properties. Structural and superconducting properties were studied for samples of YBa 2 (Cu 1- x M x ) 3 O 7-δ , with M = Sb (I), Mn (II), and Sb 1/2 Mn 1/2 (III), and (1-x)Y 1/3 Ba 2/3 CuO 3-δ ·xSr(Sb 1/2 Mn 1/2 )O 3 (IV), using x-ray diffraction, electron microscopy, Mossbauer spectroscopy, as well as changes in the temperature dependence of the resistivity ρ(T)

  18. The growth and characterisation of YBa2Cu3O7-δ superconducting thin films

    International Nuclear Information System (INIS)

    McCurry, M.P.

    1999-02-01

    The normal state properties of YBa 2 Cu 3 O 7-δ (YBCO) are not completely understood. It is known that the oxygen doping play a large part in determining these properties. The optical conductivity of a series of c-axis YBCO thin films was investigated in this thesis. The films were grown on (100) MgO substrates using a pulsed laser deposition (PLD) system and characterised using X-ray diffraction, atomic force microscopy and resistance-temperature measurements. The optimum parameters for c-axis YBCO thin film growth were determined by systematically varying the main deposition parameters. The best quality films had a transition temperature T c ∼ 88K, with a transition width ∼ 1-2K. Critical current densities of J c ∼ 10 7 Acm -2 were obtained. Substrate and target morphology affected the quality of the films. a-axis YBCO films were grown using a PrBa 2 Cu 3 O 7 (PBCO) film as a template for growth. The choice of target and substrate were again important, with a smooth substrate essential for the multi-layering. T c ∼ 83K and J c ∼ 10 6 Acm -2 were the best values obtained. These values compare with data published on the 'best' YBCO films deposited by PLD. A series of c-axis films was controllably under-doped using an ex-situ annealing process. The as-grown films were assumed to be optimally doped with δ ∼ 0.05. Doping levels in the 'metallic' region, 0.05 -2 mbar. Another tetragonal film was obtained by cooling it after deposition in a nitrogen atmosphere. Neither had a superconducting transition; the c-axes of both films were elongated. The films could be successfully re-doped with oxygen, with a subsequent return to optimal values of T c and c-axis lattice parameter. The dielectric function of optimally doped and under-doped c-axis YBCO films was determined using the attenuated total reflection (ATR) technique. This data was obtained at a fixed frequency of 2984 cm -1 , (0.366eV), at temperatures ranging from 300K to 80K. The data was analysed in

  19. Heteroepitaxial growth of strained multilayer superconducting thin films of Nd1.83Ce0.17CuOx/YBa2Cu3O7

    International Nuclear Information System (INIS)

    Gupta, A.; Gross, R.; Olsson, E.; Segmueller, A.; Koren, G.; Tsuei, C.C.

    1990-01-01

    Heteroepitaxial growth of strained multilayer thin films of YBa 2 Cu 3 O 7-δ /Nd 1.83 Ce 0.17 CuO x by pulsed-laser deposition is reported. The coherency strain results in biaxial compression of the tetragonal Nd 1.83 Ce 0.17 CuO x layers, whereas the biaxial tension in the YBa 2 Cu 3 O 7-δ layers removes the orthorhombic distortion and makes the unit cell isotropic in the basal plane (a=b). Depending on their oxygen content, either the YBa 2 Cu 3 O 7-δ or the Nd 1.83 Ce 0.17 CuO x layers are superconducting in these multilayers. The strain-induced structural modification has a significant influence on the superconducting transition temperature of the YBa 2 Cu 3 O 7-δ layers

  20. Growth and transport properties of multilayer superconducting films of Nd1.83Co0.17CuOx/YBa2Cu3O7

    International Nuclear Information System (INIS)

    Gupta, A.; Gross, R.; Olsson, E.; Segmuller, A.; Koren, G.

    1990-01-01

    This paper reports on strained multilayer thin films of YBa 2 Cu 3 O 7-δ /Nd 1.83 Ce 0.17 CuO x that have been prepared by laser ablation deposition. For individual layers below a critical layer thickness of about 250 Angstrom, coherency strain compresses the Nd 1.83 Ce 0.17 CuO x lattice and expands the YBa 2 Cu 3 O 7-δ lattice. The orthorhombic distortion in the YBa 2 Cu 3 O 7-δ layers is also removed. Depending on their oxygen content, either the YBa 2 Cu 3 O 7-δ , or the Nd 1.83 Ce 0.17 CuO x layers are superconducting in these multilayers. The strain-induced structural modification has a significant influence on the superconducting transition temperature and critical current density of the YBa 2 Cu 3 O 7-δ layers. Zero field critical current densities as high as 1.1 x 10 7 A/cm 2 at 77K have been measured for the YBa 2 Cu 3 O 7-δ layers

  1. Microscopic measurement of penetration depth in YBa2Cu3O7-δ thin films by scanning Hall probe microscopy

    International Nuclear Information System (INIS)

    Oral, A.; Bending, S.J.; Humphreys, R.G.; Henini, M.

    1997-01-01

    We have used a low noise scanning Hall probe microscope to measure the penetration depth microscopically in a YBa 2 Cu 3 O 7-δ thin film as a function of temperature. The instrument has high magnetic field (approx. 2.9x10 -8 T Hz -1/2 at 77 K) and spatial resolution (approx. 0.85 μm). Magnetic field profiles of single vortices in the superconducting film have been successfully measured and the microscopic penetration depth of the superconductor has been extracted. We find surprisingly large variations in values of λ for different vortices within the scanning field. (author)

  2. Transport critical current density and microstructure in extruded YBa2Cu3O7-x wires processed by zone melting

    International Nuclear Information System (INIS)

    Shi, D.; Krishnan, H.; Hong, J.M.; Miller, D.; McGinn, P.J.; Chen, W.H.; Xu, M.; Chen, J.G.; Fang, M.M.; Welp, U.; Lanagan, M.T.; Goretta, K.C.; Dusek, J.T.; Picciolo, J.J.; Balachandran, U.

    1990-01-01

    YBa 2 Cu 3 O 7-x compounds were extruded into long wires with the diameter of 1 mm after sintering. The sintered wires were subsequently zone melted to develop a highly textured microstructure. Magnetization experiments at 77 K indicated a J c value of 1x10 5 A/cm 2 at 1 T. Transport measurements at 77 K showed a greatly enhanced field dependence of the critical current density. Transmission electron microscopy revealed an important grain-boundary feature which eliminated the weak-link behavior. Large amounts of dislocations have also been found in the zone-melted sample which may contribute to flux pinning in the system

  3. Effects of process variables on the properties of YBa2Cu3O(7-x) ceramics formed by investment casting

    Science.gov (United States)

    Hooker, M. W.; Taylor, T. D.; Leigh, H. D.; Wise, S. A.; Buckley, J. D.; Vasquez, P.; Buck, G. M.; Hicks, L. P.

    1993-01-01

    An investment casting process has been developed to produce net-shape, superconducting ceramics. In this work, a factorial experiment was performed to determine the critical process parameters for producing cast YBa2Cu3O7 ceramics with optimum properties. An analysis of variance procedure indicated that the key variables in casting superconductive ceramics are the particle size distribution and sintering temperature. Additionally, the interactions between the sintering temperature and the other process parameters (e.g., particle size distribution and the use of silver dopants) were also found to influence the density, porosity, and critical current density of the fired ceramics.

  4. A study on oxygen-deficient YBa2Cu3O7-δ superconductors by positron lifetime spectroscopy

    International Nuclear Information System (INIS)

    Zhang Jincang; Liu Fengqi; Liu Junzheng; Cao Shixun; Cheng Guosheng

    1995-01-01

    Positron lifetime spectroscopy has been used for studying various oxygen-deficient YBa 2 Cu 3 O 7 - δ (δ = 0.06-0.68) at normal state (300 K) and Superconducting state (77 K). Using the two-state trapping model, the experimental results were analysed and there exists a typical positron annihilation characteristics in this systems. The local electron density n e and vacancy concentration C v are calculated as a function of oxygen-deficiency δ. The mechanism of positron annihilation and the correlation with superconductivity are also discussed

  5. The growth of large-area superconducting YBa2Cu3O7-x thin films by pulsed laser ablation

    International Nuclear Information System (INIS)

    Lai, H.C.; Chang, C.M.; Lin, R.J.; Liu, R.S.

    1996-01-01

    In-situ growth of 2-in. diameter superconducting YBa 2 Cu 3 O 7-x (YBCO) thin films using an excimer KrF pulsed laser has been studied. Films with critical transition temperature (T c,0 ) of 89±1 K and critical current density (J c,77K ) in excess of 1 x 10 6 A cm -2 have been prepared routinely. Uniformity in film thickness of below ±15% and film composition of ±5% have been measured. The effects of gas nozzle geometry and target evolution during ablation on the superconducting properties and surface morphology of YBCO thin films have also been investigated. (orig.)

  6. Silver distribution in crystals and intercrystalline space of YBa2Cu3O7-σ-Ag composite materials

    International Nuclear Information System (INIS)

    Kozakov, A.T.; Klevtsov, A.N.; Shevtsova, S.I.; Razumovskaya, O.N.

    1991-01-01

    Chemical and phase composition is investigated of the YBa 2 Cu 3 O 7-σ -Ag composite obtained by means of Ag diffusion in high-temperature superconductor and by sintering yttrium, barium and copper with Ag or Ag 2 O. In composite samples, obtained by sintering at 900 deg C during 24 h in air and oxygen, is found silver not only in intercrystalline gaps in the form of single formations with dimensions of 1-20 μm at small content of copper, but in the crystallite composition. In samples, obtained by Ag diffusion into high-density ceramics, are found conglomerates of silver, uniformly distributed in the all volume

  7. Complex microwave conductivity of YBa2Cu3O7 in magnetic fields up to 500 T

    International Nuclear Information System (INIS)

    Bykov, A.I.; Dolotenko, M.I.; Fowler, C.M.; Freeman, B.L.; Goettee, J.D.; King, J.C.; Kolokolchikov, N.P.; Kudasov, Yu.B.; Lewis, W.; Marshall, B.R.; Papatheofanis, B.J.; Platonov, V.V.; Rodriguez, P.J.; Tatsenko, O.M.; Veeser, L.R.; Zerwekh, W.D.

    1995-01-01

    The complex microwave conductivity of thin, oriented YBa 2 Cu 3 O 7 films was measured at 94 GHz in pulsed, ultrahigh-magnetic fields up to 500 T. The c-axis of the film was perpendicular to the magnetic field. We estimate the upper critical field of the film at absolute zero as B c2 (0)=340±40 T. Dynamics of the transition into a normal state and connection with previous measurements of the reversibility line are discussed. (orig.)

  8. Origin of the irreversibility line in thin YBa2Cu3O7-δ films with and without columnar defects

    International Nuclear Information System (INIS)

    Prozorov, R.; Konczykowski, M.; Schmidt, B.; Yeshurun, Y.; Shaulov, A.; Villard, C.; Koren, G.

    1996-01-01

    We report on measurements of the angular dependence of the irreversibility temperature T irr (θ) in YBa 2 Cu 3 O 7-δ thin films, defined by the onset of a third-harmonic signal and measured by a miniature Hall probe. From the functional form of T irr (θ) we conclude that the origin of the irreversibility line in unirradiated films is a dynamic crossover from an unpinned to a pinned vortex liquid. In irradiated films the irreversibility temperature is determined by the trapping angle. copyright 1996 The American Physical Society

  9. Effect of particle-induced displacements on the critical temperature of YBa2Cu3O7

    International Nuclear Information System (INIS)

    Summers, G.P.; Burke, E.A.; Chrisey, D.B.; Nastasi, M.; Tesmer, J.R.

    1989-01-01

    The particle-induced depression of the superconducting critical temperature T c of YBa 2 Cu 3 O 7-δ is shown to be directly proportional, over seven orders of magnitude, to the nonionizing energy deposited in the lattice by primary knock-on atoms displaced by incident electrons, protons, and heavy ions. It is concluded that ΔT c is proportional only to the average number of defects produced and can therefore be predicted for any particle, energy, and fluence from a calculation of the nonionizing energy loss

  10. Low field anisotropic properties of a single crystals of superconducting YBa2Cu3O7

    International Nuclear Information System (INIS)

    Hammann, J.; Ocio, M.; Vincent, E.; Bertinotti, A.; Luzet, D.

    1987-09-01

    Low field (0.4G≤H≤3G) magnetization measurements have been performed on small single crystals of superconducting YBa 2 Cu 3 O 7.δ using a SQUID magnetometer. They revealed anisotropic properties in the temperature dependences of the shielding and the Meissner effects. A sharp unique transition at 95 K is observed with the field parallel to c. In the perpendicular direction a second transition line seems to be crossed at T* = 84 K. This temperature T* remains constant in the range of fields investigated

  11. Orthorhombicity mixing of s- and d-gap components in YBa2Cu3O7 without involving the chains

    International Nuclear Information System (INIS)

    Varelogiannis, G.

    1998-01-01

    Momentum decoupling develops when forward scattering dominates the pairing interaction. In this regime it is possible to obtain anisotropic s- or d-wave superconductivity even with isotropic pairing scattering. We show that in the momentum decoupling regime, the orthorhombic distortion of the CuO 2 planes is enough to explain the experimental reports for s- mixing in the dominantly d-wave gap of YBa 2 Cu 3 O 7 . In the case of spin fluctuations mediated pairing instead, a large part of the condensate must be located in the chains in order to understand the experiments. copyright 1998 The American Physical Society

  12. Study on the effects of fluorine and oxygen deficiency on YBa2Cu3O7 by ab initio method

    Institute of Scientific and Technical Information of China (English)

    刘洪霖; 曹晓卫; 瞿丽曼; 陈念贻

    1997-01-01

    The calculations of clusters modeling the fluorine-doping and oxygen deficiency of YBa2Cu3O2,have been performed by the method of all-electron ab initio Hartree-Fock with self-consistent crystal field Results show that in CuO planes electric charge significantly increases,the chemical valence of Cu decreases and the covalent bonding of Cu-O greatly weakens owing to oxygen deficiency,while the effect of F restores the local electronic structure of YBa2Cu3O7 The reported opinion that F occupied the oxygen vacancy in Cu-O chains seems disputable according to the calculated bonding characteristics.

  13. Josephson oscillations and noise temperatures in YBa2Cu3O7-x grain-boundary junctions

    DEFF Research Database (Denmark)

    Yu, Ya. Divin; Mygind, Jesper; Pedersen, Niels Falsig

    1992-01-01

    The ac Josephson effect was studied in YBa2Cu3O7−x grain-boundary junctions (GBJ) in the temperature range from 4 to 90 K. The temperature dependence of the linewidth of millimeter-wave Josephson oscillations was measured and it is shown that the derived effective noise temperatures may be as low...... as the physical temperature in the temperature range investigated. In the millimeter-wave range, linewidths as low as 380 MHz were found at liquid-nitrogen temperatures. Applied Physics Letters is copyrighted by The American Institute of Physics....

  14. Surface resistance of YBa2Cu3O7 films deposited on LaGaO3 substrates

    International Nuclear Information System (INIS)

    Cooke, D.W.; Gray, E.R.; Houlton, R.J.; Javadi, H.H.S.; Maez, M.A.; Bennett, B.L.; Rusnak, B.; Meyer, E.A.; Arendt, P.N.; Beery, J.G.; Brown, D.R.; Garzon, F.H.; Raistriek, I.D.; Bolmaro, B.; Elliott, N.E.; Rollett, A.D.; Klein, N.; Muller, G.; Orbach, S.; Piel, H.; Josefowicz, J.Y.; Rensch, O.B.; Drabeck, L.; Gruner, G.

    1989-01-01

    Superconducting films of YBa 2 Cu 3 O 7 deposited onto LaGaO 3 substrates were prepared by e-beam and magnetron sputtering techniques. Surface resistance measurements made at 22 GHz, 86 GHz, and 148 GHz show that these films are superior to those deposited by similar techniques onto SrTiO 3 . Typical surface resistance values measured at 22 GHz and 12 K are ∼2 m(cgom) with the lowest value being 0.2 m(cgom), which is only 2 to 4 times higher than Nb. The surface resistance is proportional to the square of the measuring frequency

  15. Determination of the inter- and intra-granular critical currents in superconducting YBa2Cu3O7 welds

    International Nuclear Information System (INIS)

    Bozzo, B; Iliescu, S; Bartolome, E; Palau, A; Granados, X; Puig, T; Obradors, X; Amoros, J; Carrera, M

    2005-01-01

    A method for determining simultaneously the inter- and intra-grain critical currents has been developed in welded YBa 2 Cu 3 O 7 (YBCO) ceramics by solving the Inverse Problem for local maps of the magnetic field in the remanent state. From that current distribution, the current density flowing through the superconducting weld as well as the current density circulating inside the grains can be deduced. The method is discussed and it is applied to several examples of YBCO/Ag/YBCO welds. The results obtained show that it is possible to obtain superconducting joints with a quality at the same level as that of the starting material

  16. Thermal capacity of ternary oxide YBa2Cu3O7-y in 300-1100 K interval

    International Nuclear Information System (INIS)

    Sharpataya, G.A.; Ozerova, Z.P.; Kolnovalova, I.A.; Lazarev, V.B.; Shaplygin, I.S.

    1991-01-01

    Thermal capacity of YBa 2 Cu 3 O 7-y samples with different thermal prehistory is measured using a differential scanning calorimeter within 300-1100 K interval. It is shown that the combination of thermal capacity temperature dependence curves in these samples demonstrates reversibility and temperature limits of oxygen absorption and release processes with the corresponding changes of the formular index by oxygen from 6.85-6.90 to 6.35 and vice versa. Thermal capacity anomaly, corresponding to the reversible structural transition from orthorhombic to tetragonal phase with the simultaneous oxygen loss is observed within 630-1000 K interval

  17. Complex microwave conductivity of YBa2Cu3O7 in magnetic fields up to 500T

    International Nuclear Information System (INIS)

    Goettee, J.D.; Zerwekh, W.D.; Kudasov, Y.B.

    1994-01-01

    We have measured the complex conductivity of thin films of YBa 2 cu 3 O 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 ± 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

  18. Current transport and electronic states in a,b-axis-oriented YBa2Cu3O7/PrBa2Cu3O7/YBa2Cu3O7 sandwich-type junctions

    International Nuclear Information System (INIS)

    Yoshida, J.; Nagano, T.; Hashimoto, T.

    1996-01-01

    Precise measurement of the temperature and voltage dependence of junction conductance has been carried out for a,b-axis-oriented YBa 2 Cu 3 O 7 /PrBa 2 Cu 3 O 7 /YBa 2 Cu 3 O 7 sandwich-type junctions to investigate the possible origin of Josephson coupling in these junctions. Regardless of the presence or absence of the Josephson effect, most of the junctions exhibited a dip in conductance around zero voltage in their dI/dV profiles at low temperatures. This dI/dV anomaly was attributed to the existence of a minimum in the density of states due to electron-electron interaction in disordered metals in the vicinity of a tunneling barrier within the junctions. The complex temperature dependence of junction conductance was reproduced well by a theoretical model in which both tunneling conduction paths and variable range hopping paths were assumed to exist within the PrBa 2 Cu 3 O 7 barrier layer. No definite evidence of current transport through a small number of localized levels or a metallic conduction path in PrBa 2 Cu 3 O 7 has been confirmed, even for junctions with a 20-nm-thick barrier layer. copyright 1996 The American Physical Society

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

    Science.gov (United States)

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

    1997-02-01

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

  20. Transport properties of ultra-thin granular YBa2Cu3O7−δ nanobridges

    International Nuclear Information System (INIS)

    Bar, E.; Levi, D.; Koren, G.; Shaulov, A.; Yeshurun, Y.

    2014-01-01

    Highlights: • Nano bridges were patterned on laser ablated ultra-thin YBa 2 Cu 3 O 7 films. • Magneto-transport measurements reveal phenomena that are usually absent in the bulk. • Magnetoresistance (MR) oscillation point to effect of granularity. • Negative MR at low fields and negative MR slope at high fields were observed. • V-I curves exhibit voltage jumps at temperatures well below T c . - Abstract: Magneto-transport measurements in YBa 2 Cu 3 O 7 nanobridges, patterned on laser ablated ultra-thin films, reveal phenomena that are usually absent in the bulk of the material. These include broadening of the resistive transition, magnetoresistance oscillation, negative magnetoresistance at low fields, negative magnetoresistance slope at high fields, and V–I curves that exhibit voltage jumps at temperatures well below T c . These phenomena, attributed to the granular nature of the bridges, should be taken into account in any future attempts to utilize such bridges in technological applications

  1. Faceting of (001) CeO2 Films: The Road to High Quality TFA-YBa2Cu3O7 Multilayers

    International Nuclear Information System (INIS)

    Coll, M; Gazquez, J; Sandiumenge, F; Pomar, A; Puig, T; Obradors, X; Espinos, J P; Gonzalez-Elipe, A R

    2006-01-01

    CeO 2 films are technologically important as a buffer layer for the integration of superconducting YBa 2 Cu 3 O 7 films on biaxially textured Ni substrates. The growth of YBa 2 Cu 3 O 7 layers on the CeO 2 cap layers by the trifluoroacetate (TFA) route remains a critical issue. To improve the accommodation of YBa 2 Cu 3 O 7 on CeO 2 , surface conditioning or CeO 2 is required. In this work we have applied ex-situ post-processes at different atmospheres to the CeO 2 layers deposited on YSZ single crystals using rf sputtering. XPS analysis showed that post-annealing CeO 2 layer in Ar/H 2 /H 2 O catalyses in an unexpected way the growth of (001)- terraces. We also report on the growth conditions of YBa 2 Cu 3 O 7 -TFA on CeO 2 buffered YSZ single crystal grown by chemical solution deposition and we compare them with those leading to optimized YBa 2 Cu 3 O 7 -TFA films on LaAlO 3 single crystals. Critical currents up to 1.6 MA/cm 2 at 77 K have been demonstrated in 300 nm thick YBa 2 Cu 3 O 7 layers on CeO 2 /YSZ system. The optimized processing conditions have then been applied to grow YBa 2 Cu 3 O 7 -TFA films on Ni substrates having vacuum deposited cap layers of CeO 2

  2. Critical current density in (YBa2Cu3O7-δ)1-x-(PrBa2Cu3O7-δ)x melt-textured composites

    Science.gov (United States)

    Opata, Yuri Aparecido; Monteiro, João Frederico Haas Leandro; Jurelo, Alcione Roberto; Siqueira, Ezequiel Costa

    2018-06-01

    Melt textured (YBa2Cu3O7-δ)1-x-(PrBa2Cu3O7-δ)x composites (x = 0.00 and x = 0.05) were grown using the top seeding method. The effect of the PrBa2Cu3O7-δ phase on the growth process and the modification of the microstructure as well as on the physical properties was analyzed. X-ray analyses indicated that both pure and Pr-doped samples present an orthorhombic superconducting phase. From resistivity measurements for YBa2Cu3O7-δ and (YBa2Cu3O7-δ)0.95-(PrBa2Cu3O7-δ)0.05 samples, the Tcab did not change and was around 90.5 K. However, from magnetic measurements, the superconductivity was observed in critical temperatures TC = 92.9 K and 92.4 K for YBa2Cu3O7-δ and (YBa2Cu3O7-δ)0.95-(PrBa2Cu3O7-δ)0.05 samples, respectively. The YBa2Cu3O7-δ sample showed higher critical current densities than those shown by the (YBa2Cu3O7-δ)0.95-(PrBa2Cu3O7-δ)0.05 sample, with values of JC = 5.85 × 105 A/cm2 and 4.72 × 105 A/cm2, respectively. This paper also discusses the importance of Pr substitution on nano- and micro-meter scales to enhance JC(H).

  3. Chemical solution deposition: a path towards low cost coated conductors

    International Nuclear Information System (INIS)

    Obradors, X; Puig, T; Pomar, A; Sandiumenge, F; Pinol, S; Mestres, N; Castano, O; Coll, M; Cavallaro, A; Palau, A; Gazquez, J; Gonzalez, J C; Gutierrez, J; Roma, N; Ricart, S; Moreto, J M; Rossell, M D; Tendeloo, G van

    2004-01-01

    The achievement of low cost deposition techniques for high critical current YBa 2 Cu 3 O 7 coated conductors is one of the major objectives to achieve a widespread use of superconductivity in power applications. Chemical solution deposition techniques are appearing as a very promising methodology to achieve epitaxial oxide thin films at a low cost, so an intense effort is being carried out to develop routes for all chemical coated conductor tapes. In this work recent achievements will be presented towards the goal of combining the deposition of different type of buffer layers on metallic substrates based on metal-organic decomposition with the growth of YBa 2 Cu 3 O 7 layers using the trifluoroacetate route. The influence of processing parameters on the microstructure and superconducting properties will be stressed. High critical currents are demonstrated in 'all chemical' multilayers

  4. Structure/Property Relationships for Sol-gel Derived YBa2Cu3O7-d and SrTiO3 Films

    Science.gov (United States)

    Dawley, Jeff; Clem, Paul; Siegal, Michael; Overmyer, Don

    2001-03-01

    Solution deposition of c-axis oriented YBa2Cu3O7-d (YBCO) films on buffered RABiT substrates is a potential method for rapid, low cost production of superconducting tapes for power transmission and other applications. For this work, 100-250 nm thick YBCO and SrTiO3 (STO) films have been prepared by spin-coating and dip-coating sol-gel solutions onto LaAlO3 (100) and RABiT Ni (200) substrates. Biaxially textured STO coatings have been deposited on LaAlO3 and RABiT Ni by using a "templating" technique and controlling growth temperature and pO2. YBCO films grown on STO coated LaAlO3 possess comparable superconducting properties to YBCO films grown directly on LaAlO3 ( 1 MA/cm2 at 77K), indicating that a high quality STO layer does not degrade the crystalline quality of the YBCO. The effects of processing parameters on the STO buffer layer and novel processing techniques for decreasing the processing time and simplifying the integration of sol-gel YBCO with Ni substrates will be discussed. Sandia is a multiprogram laboratory operated by Sandia Corp., a Lockheed Martin Company, for the US Dept. Of Energy under contract DE-AC04-94A185000.

  5. Critical current density of strained multilayer thin films of Nd1.83Ce0.17CuOx/YBa2Cu3O7

    International Nuclear Information System (INIS)

    Gross, R.; Gupta, A.; Olsson, E.; Segmueller, A.; Koren, G.

    1990-01-01

    The superconducting transport properties of strained multilayer thin films of YBa 2 Cu 3 O 7-δ / Nd 1.83 Ce 0.17 CuO x , grown heteroepitaxially by laser ablation deposition, are reported. For individual layer thicknesses below a critical layer thickness of about 250 A, coherency strain removes the orthorhombic distortion in the YBa 2 Cu 3 O 7-δ layers and makes them twin-free. Zero-field critical current densities as high as 1.1x10 7 A/cm 2 at 77 K have been measured for the YBa 2 Cu 3 O 7-δ layers. Flux pinning energies at zero temperature and zero magnetic field in the range of 80--140 meV have been found

  6. Penetration depth λ(T) of YBa2Cu3O7-δ films determined from the kinetic inductance

    International Nuclear Information System (INIS)

    Lee, J.; Lemberger, T.R.

    1993-01-01

    We examine the temperature dependence of the magnetic penetration depth λ(T) of YBa 2 Cu 3 O 7-δ , determined from the kinetic inductance of a film patterned into a long meander line. This technique has sufficient sensitivity to study λ(T) to lower temperatures than have been examined previously. A numerical model which includes both the magnetic and kinetic inductances of the samples extracts λ(T) from the measured voltage. In reasonable agreement with other measurements, λ(0)∼2100 A is deduced from fitting λ(0) 2 /λ(T) 2 to the function 1-(T/T c ) 2 for T/T c ≥0.4. We find λ(T)/λ(0)-1 is proportional to (T/T c ) 2 for 0.06 ≤T/T c ≤0.4

  7. Residual losses in epitaxial thin films of YBa2Cu3O7 from microwave to submillimeter wave frequencies

    International Nuclear Information System (INIS)

    Miller, D.; Richards, P.L.; Etemad, S.; Inam, A.; Venkatesan, T.; Dutta, B.; Wu, X.D.; Eom, C.B.; Geballe, T.H.; Newman, N.; Cole, B.F.

    1991-01-01

    We have measured the residual loss in five epitaxial a-b plane films of the high-T c superconductor YBa 2 Cu 3 O 7 . Microwave measurements near 10 GHz were made by resonance techniques at 4 K. Submillimeter measurements from ∼1.5 to 21 THz were made at 2 K by a direct absorption technique. We use a model of weakly coupled superconducting grains and a homogeneous two-fluid model to fit the data for each film below the well-known absorption edge at 13.5 THz. When the penetration depth determined from muon spin rotation measurements is used to constrain each model, the weakly coupled grain model is able to fit the measured absorptivities for all films, but the two-fluid model is less successful

  8. Synthesis of in-plane aligned a-axis YBa2Cu3O7-δ thin films

    International Nuclear Information System (INIS)

    Young, K.H.; Sun, J.Z.

    1991-01-01

    We report the successful synthesis of superconducting YBa 2 Cu 3 O 7-δ (YBCO) (100) thin films with alignment of the in-plane c axis. These films were grown on single crystal NdGaO 3 (110) substrates. The twofold symmetry of the substrate surface is believed to lead to anisotropic alignment of the in-plane c axis of the epitaxial YBCO (100) film. X-ray diffraction studies indicate that over 80% of the film grew epitaxially with the YBCO [100] perpendicular to the substrate surface, and YBCO [001] aligned along one pseudo-cubic axis of the NdGaO 3 . The superconductivity onset of the film was measured to be 89 K by ac susceptibility

  9. Influence of oxygen disordering on static magnetic susceptibility of YBa2Cu3O7-x ceramics

    International Nuclear Information System (INIS)

    Sokolov, B.Yu.; Vil'danov, R.R.

    2008-01-01

    Influence of disordering of the populated oxygen positions in YBa 2 Cu 3 O 7-x ceramic's structure on its static magnetic susceptibility in the range of temperatures T>Tc is investigated. For occurrence of disordering the initial ceramics YBa 2 Cu 3 O 6,9 was annealed at T=520 C with the subsequent quenching in liquid nitrogen. Evolutions of a magnetic susceptibility and resistance of annealed ceramics during its air storage at a room temperature were studied. It is revealed that, unlike the initial optimum doped ceramics, annealed samples have appreciable temperature dependence of a magnetic susceptibility. Interpretation of results is executed on the basis of model of electronic phase separation and occurrence of a pseudo gap in a energy spectrum of free carriers of a superconductor. (authors)

  10. Critical current density and microstructure of YBa2Cu3O7-x films as a function of film thickness

    International Nuclear Information System (INIS)

    Mogro-Campero, A.; Turner, L.G.; Hall, E.L.; Lewis, N.

    1990-01-01

    Thin films of nominal composition YBa 2 Cu 3 O 7-x (YBCO) were produced on (100) SrTiO 3 substrates by coevaporation and furnace annealing. Film thicknesses in the range of 0.2 to 2.4 μm were analyzed. Microstructural investigations by cross sectional transmission electron microscopy (TEM) reveal a continuous layer of about 0.4 μm thickness adjacent to the substrate with c-axis normal to the substrate plane. In thicker films the remaining top portion has the c-axis in the film plane. The critical current density (J c ) at 77 K decreases with increasing thickness in the thickness range exceeding 0.4 μm, qualitatively consistent with the microstructural observation, but quantitatively inconsistent with a simple model based on the microstructural data

  11. Mapping the magnetic field generated by a supercurrent in a ring of YBa2Cu3O7

    Science.gov (United States)

    Sulca, P. D.; Gómez, R. W.

    2017-11-01

    We design and construct a device to map the magnetic field generated by a supercurrent in a rectangular cross section ring of YBa2Cu3O7-δ . For the measurements of the magnetic field, we develop a Gaussmeter based on a commercial Hall effect sensor coupled to an Arduino microprocessor. Our results show an asymmetric distribution of the magnetic field intensity measured at a certain distance along a plane parallel to the ring surface. The behavior of the magnetic field intensity with distance along the ring axis is closely related to what is expected for a toroid. Using the Biot-Savart law and the measured magnetic field values, the induced supercurrent is determined.

  12. Precipitates in YBa2Cu3O7-δ thin films annealed at low oxygen partial pressure

    International Nuclear Information System (INIS)

    Hou, S.Y.; Phillips, J.M.; Werder, D.J.; Tiefel, T.H.; Fleming, R.M.; Marshall, J.H.; Siegal, M.P.

    1993-01-01

    We have studied the precipitates in YBa 2 Cu 3 O 7-δ (YBCO) thin films grown by the BaF 2 process in p O 2 =4 Torr and 700 degree C. While stoichiometric films result in BaCuO 2 surface precipitates, we have found Y 2 Cu 2 O 5 precipitates embedded in the matrix of the same film. Off stoichiometric films with Ba/Y 2 Cu 2 O 5 in the film matrix. The estimated densities of the two precipitates favor a stoichiometric YBCO film matrix. This behavior is not explainable in terms of phase equilibria and is attributed to kinetic effects. The electrical properties of the films degrade as the Ba/Y ratio deviates from 2.00

  13. Microstructure of epitaxial YBa2Cu3O7-x thin films grown on LaAlO3 (001)

    International Nuclear Information System (INIS)

    Hsieh, Y.; Siegal, M.P.; Hull, R.; Phillips, J.M.

    1990-01-01

    We report a microstructural investigation of the epitaxial growth of YBa 2 Cu 3 O 7-x (YBCO) thin films on LaAlO 3 (001) substrates using transmission electron microscopy (TEM). Epitaxial films grow with two distinct modes: c epitaxy (YBCO) single crystal with the c (axis normal to the surface and a epitaxy (YBCO) single crystal with the c axis in the interfacial plane), where c epitaxy is the dominant mode grown in all samples 35--200 nm thick. In 35 nm YBCO films annealed at 850 degree C, 97±1% of the surface area is covered by c epitaxy with embedded anisotropic a-epitaxial grains. Quantitative analysis reveals the effect of film thickness and annealing temperature on the density, grain sizes, areal coverages, and anisotropic growth of a epitaxy

  14. Systematic trends of YBa2Cu3O7-δ thin films post annealed in low oxygen partial pressures

    International Nuclear Information System (INIS)

    Hou, S.Y.; Phillips, J.M.; Werder, D.J.; Tiefel, T.H.; Marshall, J.H.; Siegal, M.P.

    1994-01-01

    Systematic studies have been performed on 1000 A YBa 2 Cu 3 O 7-δ films produced by the BaF 2 process and annealed in an oxygen partial pressure (p O 2 ) range from 740 Torr to 10 mTorr as well as a temperature range from 600 to 1050 degree C. The results show that while high quality films can be annealed in a wide range of oxygen partial pressure, they have different characteristics. In general, crystalline quality and T c are optimized at high p O 2 and high annealing temperature, while strong flux pinning and low normal state resistivity are achieved at lower values of both variables. Under optimized low p O 2 conditions, an ion channeling χ min of 6% is obtained on films as thick as 5000 A. This study will serve as a useful guide to tailoring film properties to the application at hand

  15. Enhanced vortex pinning and critical current density in proton-irradiated YBa2Cu3O7-δ thin films

    International Nuclear Information System (INIS)

    Venturini, E.L.; Siegal, M.P.; White, A.E.; Hou, S.Y.; Phillips, J.M.

    1993-01-01

    The appropriate fluence of 2.0 MeV H + ions has been shown previously to enhance the critical current density J c by a factor of two at a magnetic field of 0.9 tesla in 1,000 angstrom thick epitaxial films of YBa 2 Cu 3 O 7-δ grown by the ex situ BaF 2 process. The as-grown films exhibit single crystal-like behavior in both atomic ordering and J c versus temperature and magnetic field. TRIM simulations suggest that H + irradiation generates mainly point defects throughout the crystal structure. The authors show here that such defects result in an even greater enhancement of J c for fields above 1 tesla plus a significant increase in the apparent vortex pinning potential deduced from magnetization relaxation data

  16. Enhanced vortex pinning and critical current density in proton-irradiated YBa2Cu3O7-δ thin films

    International Nuclear Information System (INIS)

    Venturini, E.L.; Siegal, M.P.; White, A.E.; Hou, S.Y.; Phillips, J.M.

    1992-01-01

    The appropriate fluence of 2.0 MeV H + ions has been shown previously to enhance the critical current density J c by a factor of two at a magnetic field of 0.9 tesla in 1000 Angstrom thick epitaxial films of YBa 2 Cu 3 O 7-δ grown by the ex situ BaF 2 process. The as-grown films exhibit single crystal-like behavior in both atomic ordering and J c versus temperature and magnetic field. TRIM simulations suggest that H + irradiation generates mainly point defects throughout the crystal structure. We show here that such defects produce both a large enhancement of J c for fields above 1 tesla and a significant increase in the apparent vortex pinning potential deduced from magnetization relaxation data

  17. Enhanced vortex pinning and critical current density in proton-irradiated YBa2Cu3O(7-delta) thin films

    Science.gov (United States)

    Venturini, E. L.; Siegal, M. P.; White, A. E.; Hou, S. Y.; Phillips, J. M.

    1992-11-01

    The appropriate fluence of 2.0 MeV H(sup +) ions has been shown previously to enhance the critical current density J(sub c) by a factor of two at a magnetic field of 0.9 tesla in 1000 (Angstrom) thick epitaxial films of YBa(2)Cu(3)O(7-delta) grown by the ex situ BaF2 process. The as-grown films exhibit single crystal-like behavior in both atomic ordering and J(sub c) versus temperature and magnetic field. TRIM simulations suggest that H(sup +) irradiation generates mainly point defects throughout the crystal structure. We show here that such defects produce both a large enhancement of J(sub c) for fields above 1 tesla and a significant increase in the apparent vortex pinning potential deduced from magnetization relaxation data.

  18. Upper-critical fields of YBa2Cu3O7-δ epitaxial thin films with variable oxygen deficiency δ

    International Nuclear Information System (INIS)

    Jones, E.C.; Christen, D.K.; Thompson, J.R.; Ossandon, J.G.; Feenstra, R.; Phillips, J.M.; Siegal, M.P.

    1994-01-01

    Fluctuation analysis in the limit of high magnetic fields was performed on three epitaxial thin films of YBa 2 Cu 3 O 7-δ for various oxygen deficiencies δ c2 (T) slope of -1.7 T/K for H parallel c, consistent with previous observations of transport and magnetic properties. Moreover, the 3D scaling showed better convergence than the 2D scaling, which gave relatively low values of H c2 . In contrast, the transitions were not adequately described by either scaling for T c off the 90-K plateau; it is speculated that this is due to an extrinsic broadening of the transitions, possibly due to the lack of a complete percolation path of the ortho-I phase (δ=0)

  19. Superconducting phase of YBa2Cu3O7-δ films in high magnetic fields: Vortex glass or Bose glass

    International Nuclear Information System (INIS)

    Woeltgens, P.J.M.; Dekker, C.; Swueste, J.; de Wijn, H.W.

    1993-01-01

    Nonlinear current-voltage (I-V) curves are measured in laser-ablated YBa 2 Cu 3 O 7-δ films deposited onto SrTiO 3 . The measurements are performed near the glass phase transition in a magnetic field of 5 T at various angles from the c axis. From a critical scaling analysis, the angular dependencies of the glass transition temperature and the critical glass exponents are extracted. At small angles, these results distinguish between a vortex glass, caused by random pointlike disorder, and a Bose glass, caused by linelike disorder. The results can be understood in terms of the vortex-glass model only. No evidence is found for the existence of a Bose-glass phase

  20. Fabrication of nanometer flat areas onto YBa2Cu3O7-x thin film surfaces by scanning tunneling microscope

    International Nuclear Information System (INIS)

    Virtanen, J.A.; Suketu, P.; Huth, G.C.; Cho, Z.H.

    1991-01-01

    A scanning tunneling microscope was used to mechanically ''mill'' nanometer flat areas of up to 1600 μm 2 on high temperature superconducting (HTS) films of YBa 2 Cu 3 O 7-x which were originally formed by laser ablation. Flatness to a standard deviation of 2 nm in height was found to be characteristic of milled areas. It was subsequently possible to mill trenches and ditches onto these flat areas. Scanning tunneling measurements of the exposed layered structure of the milled HTS surface are also reported. Surface modifications are also possible by the application of voltage pulse to the tunneling tip. The combination of electrical pulses and milling offer a possibility of mixed electromechanical patterning of the film

  1. Anisotropy of vortex creep in YBa2Cu3O7-x single crystals with unidirectional twin boundaries

    International Nuclear Information System (INIS)

    Bondarenko, A.V.; Revyakina, M.G.; Prodan, A.A.; Obolenskij, M.A.; Vovk, R.V.; Arouri, T.R.

    2001-01-01

    The creep of Abrikosov vortices in a YBa 2 Cu 3 O 7-x single crystal containing unidirectional twin boundaries (TB's) was investigated in a special experimental geometry: J parallel ab, J parallel TB, H perpendicular J, and α ident to angle H, ab was a variable parameter. It is shown that the TB's affect the configuration structure of vortex lines for disorientation angles θ between magnetic field vector and TB's planes up to 70: at angles θ current J cE , observed in low magnetic fields for H parallel ab, is replaced by a minimum in high magnetic fields. This behavior is explained by the change-over from the single vortex creep to a collective one with increasing magnetic field

  2. The effect of ageing on YBa2Cu3O7-x obtained by the photoacoustic method

    Directory of Open Access Journals (Sweden)

    Nikolić Pantelija M.

    2003-01-01

    Full Text Available Thermal diffusivity and electric transport properties of fourteen years old superconducting YBa2Cu3O7-x pellets were obtained using the photoacoustic transmission technique and then compared with freshly made superconducting samples. The theoretical model for photoacoustic (PA detection configuration is given. The measured amplitude and phase PA signals, as a function of the modulation frequency, were numerically analyzed. The thermal diffusivity, the coefficient of the carrier diffusion, optical absorption coefficient and the excess carrier lifetime were calculated. The thermal diffusivity of freshly produced samples decreased, after ageing, from about 1.3·10-6 to about 6.1·10-7 m2/s.

  3. Dominant pinning mechanisms in YBa2Cu3O7-x films on single and polycrystalline yttria stabilized zirconia substrates

    Science.gov (United States)

    Harshavardhan, K. S.; Rajeswari, M.; Hwang, D. M.; Chen, C. Y.; Sands, T.; Venkatesan, T.; Tkaczyk, J. E.; Lay, K. W.; Safari, A.

    1992-04-01

    Critical-current densities have been measured in YBa2Cu3O7-x films deposited on (100) yttria stabilized zirconia (YSZ) and polycrystalline YSZ substrates as a function of temperature (4.5-88 K), magnetic field (0-1 T) and orientation relative to the applied field. The results indicate that in films on polycrystalline substrates, surface and interface pinning play a dominant role at high temperatures. In films on (100) YSZ, pinning is mainly due to intrinsic layer pinning as well as extrinsic pinning associated with the interaction of the fluxoids with point defects and low energy planar (2D) boundaries. The differences are attributed to the intrinsic rigidity of single fluxoids which is reduced in films on polycrystalline substrates thereby weakening the intrinsic layer pinning.

  4. Interfacial effects revealed by ultrafast relaxation dynamics in BiFeO 3 / YBa 2 Cu 3 O 7 bilayers

    KAUST Repository

    Springer, D.

    2016-02-12

    The temperature dependence of the relaxation dynamics in the bilayer thin film heterostructure composed of multiferroic BiFeO3 (BFO) and superconducting YBa2Cu3O7 (YBCO) grown on a (001) SrTiO3 substrate is studied by a time-resolved pump-probe technique, and compared with that of pure YBCO thin film grown under the same growth conditions. The superconductivity of YBCO is found to be retained in the heterostructure. We observe a speeding up of the YBCO recombination dynamics in the superconducting state of the heterostructure, and attribute it to the presence of weak ferromagnetism at the BFO/YBCO interface as observed in magnetization data. An extension of the Rothwarf-Taylor model is used to fit the ultrafast dynamics of BFO/YBCO, that models an increased quasiparticle occupation of the ferromagnetic interfacial layer in the superconducting state of YBCO.

  5. On the substitution of Sr ions at Y sites in YBa2Cu3O7-d

    International Nuclear Information System (INIS)

    Siddiqi, S.A.; Sreedhar, K.; Drobac, D.; Infante, C.; Matacotta, F.C.; Ganguly, P.

    1989-10-01

    The effect of Sr substitution at the Ba sites in YBa 2 Cu 3 O 7-d has been studied, attempts to substitute Sr exclusively at Y sites have not been successful. We have been able to substitute Sr at Y sites only when the Ba ions are simultaneously substituted by Sr to give solid solutions of the type Y 1-x Sr x Ba 2-2x Sr 2x Cu 3 O 7- x /2-d . These examples show superconducting transitions higher than 78K without significant deterioration in the magnitude of the ac susceptibility. The substitutions are best understood in terms of site constraints on the ions occupying the Y and Ba sites. 4 refs, 2 figs, 2 tabs

  6. Smooth YBa2Cu3O7-x thin films prepared by pulsed laser deposition in O2/Ar atmosphere

    DEFF Research Database (Denmark)

    Kyhle, Anders; Skov, Johannes; Hjorth, Søren

    1994-01-01

    We report on pulsed laser deposition of YBa2Cu3O7-x in a diluted O2/Ar gas resulting in thin epitaxial films which are almost outgrowth-free. Films were deposited on SrTiO3 or MgO substrates around 800-degrees-C at a total chamber pressure of 1.0 mbar, varying the argon partial pressure from 0 to 0.......6 mbar. The density of boulders and outgrowths usual for laser deposited films varies strongly with Ar pressure: the outgrowth density is reduced from 1.4 x 10(7) to 4.5 x 10(5) cm-2 with increasing Ar partial pressure, maintaining a critical temperature T(c,zero) almost-equal-to 90 K and a transport...... critical current density J(c)(77 K) greater-than-or-equal-to 10(6) A/cm2 by extended oxygenation time during cool down....

  7. Surface structure of YBa2Cu3O7-x probed by reversed-bias scanning tunneling microscopy

    International Nuclear Information System (INIS)

    Edwards, H.L.; Markert, J.T.; Lozanne, A.L.d.

    1994-01-01

    We report the results of scanning tunneling microscopy studies on high-quality single crystals of YBa 2 Cu 3 O 7-x (YBCO) which were cleaved along a basal plane in situ at 20 K prior to measurement. The initial results of a systematic study of the YBCO surface are presented. Reversed-bias images of the CuO chain layer reveal modulations 3.3±0.3|b|=1.3±0.1 nm in wavelength which change phase by 180 degree under bias polarity reversal along solid chains, and are invariant under bias polarity reversal at a point defect. Regions of sharp unit-cell-sized square corrugations with disordered islands are also observed. We interpret these new results in terms of our previous model [H. L. Edwards, J. T. Markert, and A. L. de Lozanne, Phys. Rev. Lett. 69, 2967 (1992)] of the cleaved YBCO surface

  8. Observation of a vortex-glass phase in polycrystalline YBa2Cu3O7-x in a magnetic field

    International Nuclear Information System (INIS)

    Worthington, T.K.; Olsson, E.; Nichols, C.S.; Shaw, T.M.; Clarke, D.R.

    1991-01-01

    We report the results of temperature- and field-dependent transport measurements on sintered, polycrystalline samples of YBa 2 Cu 3 O 7-x . A study of the E-J curves indicates a second-order phase transition, at low current density in the coupling of the grains, that exhibits the scaling behavior predicted for a vortex glass. The ohmic resistance at low current is observed to vanish at a nonzero temperature, and the E-J curves exhibit power-law behavior at that temperature. Below this temperature the E-J curves are consistent with a true critical current with zero linear resistance. The qualitative features of the data and the values of the critical exponents are consistent with the predictions of the vortex-glass theory. Our findings cannot be explained by the predictions of conventional flux-creep models

  9. A comparison of the modulated microwave absorption spectra of ceramic and powdered YBa2Cu3O7-δ samples

    International Nuclear Information System (INIS)

    Rubins, R.S.; Hutton, S.L.; Drumheller, J.E.; Jeong, D.Y.; Black, T.D.

    1990-01-01

    Flux trapping in the 9.3 GHz modulated microwave absorption spectra observed near 4 K from ceramic and powdered ceramic specimens of two separately prepared YBa 2 Cu 3 O 7-δ samples has been used to separate the intergranular and intragranular contributions to the spectra. In the denser, glassy sample, a broad absorption with a peak near 400 Oe for forward sweeps was observed with appreciable intensity after the maximum flux was trapped. This spectrum is attributed to intergranular junctions, since its relative intensity was reduced on powdering and suspending in wax. In the less dense, more uniform sample, the latter spectrum was appreciably weaker in both ceramic and powder. Both types of junction appear to contribute to the narrow low-field absorption which was observed after zero field cooling in all the samples

  10. Epitaxial growth of YBa2Cu3O7-δ thin films on LiNbO3 substrates

    International Nuclear Information System (INIS)

    Lee, S.G.; Koren, G.; Gupta, A.; Segmuller, A.; Chi, C.C.

    1989-01-01

    In situ epitaxial growth of YBa 2 Cu 3 O 7-δ thin films on Y-cut LiNbO 3 substrates using a standard laser ablation technique is reported. Resistance of the films shows a normal metallic behavior and a very sharp ( c (R=0) of 92 K. High critical current density of J c (77 K)=2x10 5 A/cm 2 is observed, which is in accordance with epitaxial growth. Film orientation observed from x-ray diffraction spectra indicates that the c axis is normal to the substrate plane and the a axis is at 45 degree to the [11.0] direction of the hexagonal lattice of the substrate with two domains in mirror image to the (110) plane

  11. Laser wavelength dependent properties of YBa2Cu3O7-δ thin films deposited by laser ablation

    International Nuclear Information System (INIS)

    Koren, G.; Gupta, A.; Baseman, R.J.; Lutwyche, M.I.; Laibowitz, R.B.

    1989-01-01

    YBa 2 Cu 3 O 7-δ thin films were deposited onto (100) SrTiO 3 substrates using 1064, 532, 355, 248, and 193 nm laser ablation. Transport measurements show lower normal-state resistivities and higher critical currents in films deposited by the shorter wavelength lasers. The surface morphology of the films was rough with large particulates when the 1064 nm laser was used whereas much smoother surfaces with fewer and smaller particulates were obtained with the UV lasers. It is suggested that the better film quality obtained when the UV lasers are used is due to a small absorption depth of the UV photons in the ceramic target and to higher absorption by the ablated fragments. This leads to smaller ablated species and further fragmentation in the hotter plume and, therefore, to smoother and denser films

  12. Response of YBa2Cu3O7-δ grain-boundary junctions to short light pulses

    International Nuclear Information System (INIS)

    Kaplan, S.B.; Chi, C.C.; Chaudhari, P.; Dimos, D.; Gross, R.; Gupta, A.; Koren, G.

    1991-01-01

    The electrical response of a single YBa 2 Cu 3 O 7-δ grain-boundary junction to visible light pulses was measured. Using an autocorrelation technique with picosecond laser pulses, no fast voltage transients were observed with the junction biased just above its critical current. Apparently, there are no relaxation times in the range of 7 ps to 14 ns. Using direct time-domain measurement with nanosecond pulses, three types of junction response were recorded: a nonexponential decay of 11 μs (90 to 10 % time) at temperatures near T c ; an inverse-time dependence of the order of 0.3 μs (100 to 50 % time) in the temperature range of 4.2 to 15 K; and an exponential decay time of 0.15 μs with the sample immersed in superfluid helium

  13. ab-Plane Anisotropy of Transport Properties in Unidirectionally Twinned YBa2Cu3O7-δ Films

    International Nuclear Information System (INIS)

    Villard, C.; Chateignier, D.; Thrane, B.; Koren, G.; Cohen, D.; Polturak, E.

    1996-01-01

    A unidirectionally twinned, c oriented YBa 2 Cu 3 O 7-δ film was prepared on a (001) NdGaO 3 substrate. In the normal state between 100 and 300K, the unidirectional twin plane lattice induces a strong anisotropy of ρ ab , leading to a temperature independent ratio of 6 between the resisitivities across and along the twin boundaries. At 77K, the self-field critical current parallel to twin planes is 1.2x10 6 A/cm 2 , a value which is 25 times higher than along the perpendicular direction. This shows that, at this temperature, twin boundaries control the critical current values in YBCO films by either channeling or pinning effects. copyright 1996 The American Physical Society

  14. Intrinsic Channeling of Vortices along the ab Plane in Vicinal YBa2Cu3O7-δ Films

    International Nuclear Information System (INIS)

    Berghuis, P.; Di Bartolomeo, E.; Wagner, G.A.; Evetts, J.E.

    1997-01-01

    We have measured the critical current density j c as a function of the orientation of a magnetic field in vicinal YBa 2 Cu 3 O 7-δ films. When both field and Lorentz force lie within the ab plane, we observe a minimum in j c . At high temperatures, as the c -axis coherence length approaches the ab -plane distance, the minimum in j c could not be observed, indicating that this effect is related to the breakdown of the rectilinear vortex state for fields at a small angle to the ab planes. Our results are the first demonstration of intrinsic channeling of vortex strings along the ab planes. copyright 1997 The American Physical Society

  15. Dégradation à l'air et restauration des poudres de YBa2Cu3O7

    OpenAIRE

    Cazy , E.; Bahloul , D.; Smith , D.; Bonnet , J.

    1994-01-01

    La dégradation de poudres de YBa2Cu3O7-δ au contact d'air humide est un phénomène très rapide qui conduit, pour une poudre à gros grains (0,3 m2/g), à un gain initial de masse de 0,4% par heure. Afin de restaurer une poudre dégradée, il est nécessaire de décomposer les hydroxydes et carbonates qui se sont formés. La décomposition des hydroxydes se produit à $T < 750~^\\circ$C ; celle des carbonates est difficile et sensible à pO2. Les meilleures conditions correspondent à un traitement prolong...

  16. Fabrication And Characterization of YBa2Cu3O7-x Ring For The Laboratory Scale Fault Current Limiter

    International Nuclear Information System (INIS)

    Adi, Wisnu Ari; Sukirman, Engkir; Winatapura, Didin S.; Handayani, Ari

    2004-01-01

    Two rings of YBa 2 Cu 3 O 7-x superconductor have been made by using the pressing method, that has been modified. The inner diameter, outer diameter, and thickness of ring 1 are 23.46 mm, 40.66 mm, and 6.84 mm, while for ring 2 are 23.65 mm, 40.73 mm, and 8.28 mm, respectively. The XRD data show that both samples have the same 123-phase. The critical temperature, Tc of both samples is 91 K. The estimate values of induction magnetic field at the center of ring 1 and ring 2 are 1.27 x 10 -4 T (I c = 3.48 A) and 1.65 x 10 -4 T (I c = 3.52 A), respectively

  17. Off-axis sputter deposition of YBa2Cu3O7 thin films for microwave applications

    International Nuclear Information System (INIS)

    Greene, L.H.; Bagley, B.G.; Feldmann, W.L.; Barner, J.B.; Shokoohi, F.; Miceli, P.; Wilkens, B.J.; Fathy, A.; Kalokitis, D.; Pendrick, V.

    1991-01-01

    Thin films of superconducting YBa 2 Cu 3 O 7 were grown in situ by off-axis sputter deposition for microwave device fabrication. These ∼1 cm 2 films, which are reproducible, exhibit midpoint T c 's of 89--90.5 K as measured by ac susceptibility, ion channeling yields of 4.7%--6%, and c-axis rocking-curve half-widths of 0.5 degree, even with a rich microstructure as seen by scanning electron microscopy. Two films were photodefined into miniature X-band microwave bandpass filters. These narrow-band filters (0.5% bandwidth) exhibited 4.4-and 4.5-dB insertion losses at 77 K and 9.25 GHz, with little temperature dependence below 80 K

  18. Field dependence and anisotropy of the Meissner effect in sintered and dilute powders of YBa2Cu3O7

    International Nuclear Information System (INIS)

    Regnier, P.; Bontemps, N.; Monod, P.

    1990-01-01

    We report low temperature field-cooled susceptibility measurements on sintered and dilute YBa 2 Cu 3 O 7 powders in a 3-40 Oe field range. We find that the so-called Meissner fraction is field dependent, increasing as the field increases in ceramics and decreasing in powders. We also find a strong anisotropy, in both sets of samples: the Meissner fraction is larger when the field is applied parallel to the c axis. All these features are shown to emerge naturally if one assumes that the low temperature Meissner fraction: i) reflects the field dependence and the anisotropic properties of the equilibrium Meissner fraction which has been trapped at higher temperature. ii) is further reduced and its anisotropy is enhanced in sintered compounds with respect to powders, due to flux pinning at the grain boundaries

  19. All-electron ab initio calculations of YBa2Cu3O7 with self-consistence crystal field

    Institute of Scientific and Technical Information of China (English)

    刘洪霖; 陈念贻

    1995-01-01

    The quantum chemical calculations of cluster YBa2Cu3O7 considering all electrons have been per-formed by using the ab initio HF method with self-consistence crystal field.A Hartree-Fork surface potentialis proposed to make an asymmetric duster model possess a relatively symmetric potential field and to obtaina relatively symmetric electronic structure,electronic distributions,frontier orbitals,and bond order,etc.Thesuggestions that there exists a covalent bonding complex,[CuO2-O-CuO-O-Cu2]6,8-,in the cell unit ofthe crystal,and the cell units are connected with each other by ionic bonds along the c direction of the crys-tal lattice are offered based on the chemical bonding characteristics from the calculated results.The importantcontribution of the apical oxygen to superconductivities is emphasized as well.

  20. The nature of twin boundaries in the high-temperature superconductor YBa2Cu3O7

    International Nuclear Information System (INIS)

    Zhu, Y.; Welch, D.O.

    1999-01-01

    Twin boundaries are the most commonly observed lattice defect in the high-temperature superconductor YBa 2 Cu 3 O 7-δ . Furthermore, the region around a twin boundary for which the structure and composition are seriously affected is of a scale comparable to the coherence length for the superconducting order parameter. Thus, twin boundaries can be important in the behavior of magnetic vortices and the critical current density in this material. In this paper the authors review the results of a wide range of investigations of twin boundary structure and composition by advanced transmission electron microscopy methods, both imaging and analytical in nature. A simple Landau model of twin boundary energy and width is proposed

  1. Processing tetramethylammonium-carbonate-coprecipitated slurries to obtain small-particle-size YBa2Cu3O7

    International Nuclear Information System (INIS)

    Spencer, N.D.; Peders, T.S.; Baer, M.B.

    1991-01-01

    The effect of different drying and calcination methods on the ultimate particle size of YBa 2 Cu 3 O 7 (Y-123) has been investigated. The starting material was a tetramethylammonium (TMA) carbonate-precipitated slurry. Spray-drying the slurry after filtering and reslurrying (to remove residual TMA), was most effective in the ultimate formation of finely divided Y-123. The morphology of the spray-dried powder could be preserved by calcining in very low total pressures of flowing oxygen. When a slurry with 0.16% solids content was spray dried, and this powder calcined at 750 degree C in 2 Torr of flowing oxygen, a Y-123 powder of mean particle size 0.74 μm (66% submicron) was obtained

  2. Magnetic penetration depth of YBa2Cu3O(7-delta) thin films determined by the power transmission method

    Science.gov (United States)

    Heinen, Vernon O.; Miranda, Felix A.; Bhasin, Kul B.

    1992-01-01

    A power transmission measurement technique was used to determine the magnetic penetration depth (lambda) of YBa2Cu3O(7-delta) superconducting thin films on LaAlO3 within the 26.5 to 40.0 GHz frequency range, and at temperatures from 20 to 300 K. Values of lambda ranging from 1100 to 2500 A were obtained at low temperatures. The anisotropy of lambda was determined from measurements of c-axis and a-axis oriented films. An estimate of the intrinsic value of lambda of 90 +/- 30 nm was obtained from the dependence of lambda on film thickness. The advantage of this technique is that it allows lambda to be determined nondestructively.

  3. Evidence of a Normal-State Pseudogap in Bulk Superconducting Tunneling Junctions of YBa2Cu3O7

    Directory of Open Access Journals (Sweden)

    Leandro Guerra

    1999-12-01

    Full Text Available Planar contact tunneling experiments have been performed on bulk superconducting tunneling junctions of YBa2Cu3O7-δ in the temperature range 77 -295K. A clear depression in the conductance curves measured, attributed to the pseudogap, has been observed in temperatures above Tc (approx. 90K determined from dc resistivity measurements before disappearing at T*=275K. The width of the pseudogap has been quantitatively measured as Dps, ave = 25.6meV from the differential conductance plots. These results agree with the current understanding of the phenomenology and nature of this pseudogap, namely: (I the pseudogap value is relatively temperature-independent; (2 the superconducting gap and the pseudogap have the same d-wave nature; and (3 the superconducting gap evolves from the pseudogap.

  4. Growth of Highly Epitaxial YBa2Cu3O7-δ Films from a Simple Propionate-Based Solution

    DEFF Research Database (Denmark)

    Yue, Zhao; Torres, Pol; Tang, Xiao

    2015-01-01

    Intensive investigations have been conducted to develop epitaxial oxide thin films with superior electromagnetic performance by low-cost chemical solution deposition routes. In this paper, a novel propionate-based precursor solution without involving any other additive was proposed and employed...... to grow superconducting YBa2Cu3O7-δ (YBCO) films on LaAlO3 (LAO) single crystals. The precursor solutions are stable with a long shelf life of up to several months. Since the primary compositions are propionates after evaporating the solvent, the toxic reagents and evolved gases during solution synthesis...... and heat treatment can be eliminated completely. In this process, rapid pyrolysis and high conversation rate can also be achieved during growth of YBCO films in comparison with the conventional trifluoroacetate metal organic deposition routes. Remarkably, a 210 nm YBCO film exhibits high superconducting...

  5. Flux flow and pinning by twin boundaries in single crystal YBa2Cu3O7

    International Nuclear Information System (INIS)

    Kwok, W.K.; Fleshler, S.; Welp, U.; Vinokur, V.M.; Downey, J.; Crabtree, G.W.

    1993-01-01

    We present AC magnetoresistance measurements in fully oxygenated and oxygen deficient single crystals of YBa 2 Cu 3 O 7-δ . From the resistive broadening in magnetic field for H parallel ab parallel I and H parallel ab perpendicular to I, we demonstrate the existence of Lorentz force induced flux flow dissipation near T c . Using a novel crossed magnetic field technique where high angular resolution of Δθ 2 Cu 3 O 7-δ single crystals. The twin boundary pinning onset is characterized by a critical angle model and we extract a phase diagram for the onset of twin boundary pinning. We report on a strong magnetic field dependence of the critical angle for twin boundary pinning for H parallel c which is absent for H parallel ab. In addition, we find the critical angle θ * for H parallel c is greater than that observed for H parallel ab for nearly stoichiometric samples. (orig.)

  6. A study of the movement of the flux lines in YBa2Cu3O7-δ epitaxial film

    International Nuclear Information System (INIS)

    Sha Jian; He Zhenghui; Su Zhengpeng; Zhao Zhanchun; Wang Nanlin

    1991-01-01

    The movements of the flux lines in the YBa 2 Cu 3 O 7-δ epitaxial film have been studied by Hall effect and the broadening of the resistance-temperature curves(R-T curves) in the magnetic field. From the broadened R T curves the exponent relation is obtained between the value of the activation energy of the flux creep and the value of the field. From the measurements of the Hall coefficient R H the unusual variation of the Hall coefficient corresponding to the broadening of the R-T curves is found. All of the variations in the R-T curves as well as the R H -H curves have been also discussed by the vortex glass model, exploring the laws of the flux creep in different ways

  7. Interfacial effects revealed by ultrafast relaxation dynamics in BiFeO 3 / YBa 2 Cu 3 O 7 bilayers

    KAUST Repository

    Springer, D.; Nair, Saritha K.; He, Mi; Lu, C. L.; Cheong, S. A.; Wu, Tao; Panagopoulos, C.; Chia, Elbert E. M.; Zhu, Jian-Xin

    2016-01-01

    The temperature dependence of the relaxation dynamics in the bilayer thin film heterostructure composed of multiferroic BiFeO3 (BFO) and superconducting YBa2Cu3O7 (YBCO) grown on a (001) SrTiO3 substrate is studied by a time-resolved pump-probe technique, and compared with that of pure YBCO thin film grown under the same growth conditions. The superconductivity of YBCO is found to be retained in the heterostructure. We observe a speeding up of the YBCO recombination dynamics in the superconducting state of the heterostructure, and attribute it to the presence of weak ferromagnetism at the BFO/YBCO interface as observed in magnetization data. An extension of the Rothwarf-Taylor model is used to fit the ultrafast dynamics of BFO/YBCO, that models an increased quasiparticle occupation of the ferromagnetic interfacial layer in the superconducting state of YBCO.

  8. Surface and grain boundary modifications of YBa2Cu3O7-δ ceramics by plasma-enhanced fluorination

    International Nuclear Information System (INIS)

    Magro, C.; Heintz, J.M.; Etourneau, J.; Tressaud, A.; Cardinaud, C.; Turban, G.; Hudakova, N.

    1994-01-01

    The radiofrequency plasma technique involving mixtures of CF 4 + O 2 gases has been applied to the treatment of high T c superconducting oxides (YBa 2 Cu 3 O 7-δ ). The investigation of the various experimental parameters of the process has shown that the improvement of the critical current density J c mainly depends on the inlet precursor composition CF 4 + τ % O 2 , on the total pressure, and on the reaction time. The presence of fluorine in the bulk of the ceramics has been observed from electron microprobe analysis, together with an increase of the open-quotes Cu 3+ close quotes content. The plasma enhanced fluorination (PEF) treatment improves the superconducting properties of the materials: both values of the resistivity in the normal state and of the superconducting transition width are reduced and the critical transition temperature is improved of about 1 K. Mechanisms of interaction between the reactive species of the plasma and YBa 2 Cu 3 O 7-δ ceramics have been proposed through detailed angle resolved X-ray photoelectron spectroscopic analyses. At the surface of the outer grains, the plasma treatment removes (OH) - and (CO 3 ) 2- species contained in the degradation layer and gives rise to a fluoride-rich layer. In the bulk of the material the occurrence of metal-fluorine bonds in the superconducting phase has to be assumed. Moreover, interactions between atomic fluorine and grain boundaries result in an improvement of intergranular magnetic behavior, according to a.c. susceptibility measurements. An increase of the oxidation state of copper has also been detected, confirming the oxidizing effect of the plasma treatment

  9. Dégradation à l'air et restauration des poudres de YBa2Cu3O{7-δ}

    Science.gov (United States)

    Cazy, E.; Bahloul, D.; Smith, D.; Bonnet, J. P.

    1994-11-01

    The degradation YBa2Cu3O{7-δ} powder, on contact with moist air, is very rapid. Even for a coarse powder (0.3 m^2/g) the initial increase in weight is 0.4% per hour. In order to restore the powder to its non degraded state, it is necessary to decompose the hydroxides and carbonates which have formed. The decomposition of the hydroxides can be achieved with a thermal treatment below 750 ^circC but the decomposition of carbonates is more difficult and depends on the oxygen partial pressure. The best conditions correspond to a prolonged treatment just below the temperature of formation of the first liquid in the Y2BaCuO5-BaCuO2-CuOx ternary system. La dégradation de poudres de YBa2Cu3O{7-δ} au contact d'air humide est un phénomène très rapide qui conduit, pour une poudre à gros grains (0,3 m^2/g), à un gain initial de masse de 0,4% par heure. Afin de restaurer une poudre dégradée, il est nécessaire de décomposer les hydroxydes et carbonates qui se sont formés. La décomposition des hydroxydes se produit à T < 750 ^circC ; celle des carbonates est difficile et sensible à p_{O_2}. Les meilleures conditions correspondent à un traitement prolongé à une température immédiatement inférieure à celle d'apparition du premier liquide dans le système Y2BaCuO5-BaCuO2-CuOx.

  10. Effect of cooling rate on the structure and properties of thick films of YBa2Cu3O7-x

    International Nuclear Information System (INIS)

    Li, S.R.; Oleinikov, N.N.; Gas'kov, A.M.

    1993-01-01

    A problem associated with the production of quality films is chemical interaction of the HTSC material with the substrate. This leads to a considerable worsening or complete loss of the superconducting properties of a functional material. A second problem is selection of a substrate whose thermal expansion coefficient (TCE) is as close as possible to the TCE of the superconducting material. Omission of this condition leads to production of a HTSC material which is subject to perturbing mechanical stresses (compressive or tensile stress), and this is a potential cause of the reduction of the functional parameters of the material. The authors note that other substrate requirements should be considered only during production of thin films. Unfortunately, the production of quality thick films is apparently not worked out with resolution of the latter two problems. It is very important in production of HTSC materials to consider the rate of cooling at the moment of formation of the orthorhombic phase (in the following, the tetragonal-orthorhombic transition). Undesirable relaxation can be avoided if the cooling rate is lowered below some critical value. According to the computations, this problem is solved most successfully in HTSC materials of the composition YBa 2 Cu 3 O 7-x if their ceramic structure consists of crystallites whose size does not exceed 1-2 μm. The goal of this work is to elucidate the effect of the cooling rate of thick films of composition YBa 2 Cu 3 O 7-x in the temperature range corresponding to transition of the tetragonal to the orthorhombic phase on their structure and properties

  11. High sensitivity of positrons to oxygen vacancies and to copper-oxygen chain disorder in YBa2Cu3O7√/sub x/

    International Nuclear Information System (INIS)

    von Stetten, E.C.; Berko, S.; Li, X.S.; Lee, R.R.; Brynestad, J.; Singh, D.; Krakauer, H.; Pickett, W.E.; Cohen, R.E.

    1988-01-01

    Temperature-dependent positron-electron momentum densities have been studied by two-dimensional angular correlation of annihilation radiation from 10 to 320 K in YBa 2 Cu 3 O 7 √/sub x/ samples. The positron ground-state charge density, computed by the linearized augmented plane-wave method, indicates that in YBa 2 Cu 3 O 7 delocalized positrons sample preferentially the linear copper-oxygen chains. Positron localization due to disorder in these chains is invoked to explain the striking differences observed between superconducting (x≅0.02) and nonsuperconducting (x≅0.70) samples

  12. Experimental evidence for fast cluster formation of chain oxygen vacancies in YBa2Cu3O7-d being at the origin of the fishtail anomaly

    OpenAIRE

    Erb, Andreas; Manuel, Alfred A.; Dhalle, Marc; Marti, Frank; Genoud, Jean-Yves; Revaz, Bernard; Junod, Alain; Vasumathi, Dharmavaram; Ishibashi, Shoji; Shukla, Abhay; Walker, Eric; Fischer, Oystein; Fluekiger, Rene; Pozzi, Riccardo; Mali, Mihael

    1998-01-01

    We report on three different and complementary measurements, namely magnetisation measurements, positron annihilation spectroscopy and NMR measurements, which give evidence that the formation of oxygen vacancy clusters is on the origin of the fishtail anomaly in YBa2Cu3O7-d. While in the case of YBa2Cu3O7.0 the anomaly is intrinsically absent, it can be suppressed in the optimally doped state where vacancies are present. We therefore conclude that the single vacancies or point defects can not...

  13. Growth orientation and superconducting properties of YBa2Cu3O7-δ films prepared by the low-fluorine sol-gel process

    International Nuclear Information System (INIS)

    Lei Li; Zhao Gaoyang; Xu Hui; Zhao Juanjuan

    2010-01-01

    YBa 2 Cu 3 O 7-δ (YBCO) films were deposited on (100)-oriented LaAlO 3 (LAO) single crystal substrates by the dip-coating process using low-fluorine solution. Their microstructures were characterized with the aid of X-ray diffractometry, scanning electron microscopy and high-resolution transmission electron microscopy. Their superconducting properties were measured by the standard four-probe method. The experiment results show that the film obtained under high enough humidity conditions exhibits better c-axis texture and superconducting properties than the film under a relatively low humidity conditions. Based on the classical nucleation and chemical reaction thermodynamics theory, the underlying crystalline and growth mechanisms of YBCO films under certain humidity conditions are explained in combination with our experimental results. It is suggested that the unreacted intermediate phases such as BaF 2 and CuO aggregated in the YBCO grain boundary will cause lattice distortion in the YBCO matrix and further induce the formation of a-axis oriented YBCO grains as crystallization proceeds. Therefore, it is believed that the relative content of water vapor within the heat-treatment atmosphere plays quite an important role in the preparation of c-axis oriented YBCO film with good superconducting properties. (semiconductor materials)

  14. Preparation of epitaxial YBa2Cu3O7-y films on CeO2-buffered yttria-stabilized zirconia substrates by fluorine-free metalorganic deposition

    International Nuclear Information System (INIS)

    Tsukada, Kenichi; Yamaguchi, Iwao; Sohma, Mitsugu; Kondo, Wakichi; Kamiya, Kunio; Kumagai, Toshiya; Manabe, Takaaki

    2007-01-01

    Epitaxial YBa 2 Cu 3 O 7-y (YBCO) films of 120-550 nm thickness have been prepared by fluorine-free metalorganic deposition using a metal acetylacetonate-based coating solution on yttria-stabilized zirconia (YSZ) substrates with an evaporated CeO 2 buffer layer. The YBCO films were highly (0 0 1)-oriented by X-ray diffraction θ-2θ scanning and φ scanning. The YBCO films 120-400 nm in thickness demonstrated high critical current densities (J c ) with an average in excess of 3 MA/cm 2 at 77 K using an inductive method. In particular, a 210-nm-thick film showed a J c of 4.5 MA/cm 2 . These excellent properties are attributed to the high crystallinity, small in-plane fluctuation due to high epitaxy and to the microstructure free from grain boundaries in the YBCO films. Further increase of film thickness increased the fraction of irregularities, i.e., precipitates and micropores, in the film surfaces, resulting in lower J c values

  15. Disappearance of the force-free current configuration at the first order vortex lattice phase transition in YBa 2Cu 3O 7-δ single crystals

    Science.gov (United States)

    van der Beek, C. J.; Indenbom, M. V.; Berseth, V.; Benoit, W.; Erb, A.; Flükiger, R.

    1997-08-01

    The anisotropy in the transverse AC susceptibility of YBa2Cu3O7-δ single crystals, induced by the periodic appearance of a force-free current configuration upon rotation of a superimposed DC field in the crystal plane, disappears at the vortex phase transition, indicating the loss of the vortex lines' stability against mutual cutting.

  16. Analysis of low-field isotropic vortex glass containing vortex groups in YBa2Cu3O7-x thin films visualized by scanning SQUID microscopy

    NARCIS (Netherlands)

    Wells, Frederick S.; Pan, Alexey V.; Wang, X.; Fedoseev, Sergey A.; Hilgenkamp, Hans

    2015-01-01

    The glass-like vortex distribution in pulsed laser deposited YBa2Cu3O7-x thin films is observed by scanning superconducting quantum interference device microscopy and analysed for ordering after cooling in magnetic fields significantly smaller than the Earth's field. Autocorrelation calculations on

  17. Characterization of Microstructure and Performance of YBa2Cu3O7−x Films Synthesized Through Sol–Gel Aqueous Precursors with DEA/TEA Addition

    DEFF Research Database (Denmark)

    Tang, Xiao; He, Dong; Zhao, Yichun

    2013-01-01

    YBa2Cu3O7−x (YBCO) superconducting thin films are synthesized through non-fluorine sol–gel aqueous processes. Diethanolamine (DEA) and triethonalamine (TEA), which have similar molecular structures but different complexation abilities and molecular weights, are separately used as chelating agents...

  18. Study of the movement of oxygen vacancies in the orthorhombic phase of YBa2Cu3O7-x by positron Doppler broadening spectroscopy

    International Nuclear Information System (INIS)

    Hong Zhang; Xiao-Gan Wang; Yao-Xian Fu

    1988-01-01

    The positron annihilation Doppler spectroscopy is used to monitor the movement of oxygen vacancy of YBa 2 Cu 3 O 7-x and an activation energy of (0.80 ± 0.10) eV for migration of oxygen vacancy in orthorhombic phase is obtained. (author)

  19. Theoretical investigation of the Fermi surface of La2-xSrxCuO4 and YBa2Cu3O7

    International Nuclear Information System (INIS)

    Antonov, V.N.; Antonov, V.N.; Bar'yakhtar, V.G.

    1989-01-01

    The theoretical investigation of both the Fermi surface (FS) form and isoenergetic surfaces near the Fermi energy of La 2-x Sr x CuO 4 and YBa 2 Cu 3 O 7 is carried out by selfconsistent LMTO/method in an atomic sphere approximation. The FS of these compounds is established to have an essential two-dimensional character. The FS La 2 CuO 4 is a corrugated rounded box centered in Γ point. The FS YBa 2 Cu 3 O 7 consists of four plates: an electron ''cushion'' in Γ point and three embeded hole surfaces centered in S point. In this case the ''cushion'' and one of the hole surfaces are vigorously corrugated along the z-direction. A comparison between both the FS calculated theoretically of La 2 CuO 4 and YBa 2 Cu 3 O 7 and experimental data on electron-positron annihilation is carried out. The electron-rate maps and numerical results of various characteristics, i.e., plate areas, mean rates, mean squares of the rates, partial densities of states for each plate of the FS YBa 2 Cu 3 O 7 are given

  20. Epitaxial growth of SrTiO3/YBa2Cu3O7 - x heterostructures by plasma-enhanced metalorganic chemical vapor deposition

    Science.gov (United States)

    Liang, S.; Chern, C. S.; Shi, Z. Q.; Lu, P.; Safari, A.; Lu, Y.; Kear, B. H.; Hou, S. Y.

    1994-06-01

    We report heteroepitaxial growth of SrTiO3 on YBa2Cu3O7-x/LaAlO3 substrates by plasma-enhanced metalorganic chemical vapor deposition. X-ray diffraction results indicated that SrTiO3 films were epitaxially grown on a (001) YBa2Cu3O7-x surface with [100] orientation perpendicular to the surface. The film composition, with Sr/Ti molar ratio in the range of 0.9 to 1.1, was determined by Rutherford backscattering spectrometry and energy dispersive spectroscopy. The thickness of the SrTiO3 films is 0.1-0.2 μm. The epitaxial growth was further evidenced by high-resolution transmission electron microscopy and selected area diffraction. Atomically abrupt SrTiO3/YBa2Cu3O7-x interface and epitaxial growth with [100]SrTiO3∥[001]YBa2Cu3O7-x were observed in this study. The superconducting transition temperature of the bottom YBa2Cu3O7-x layer, as measured by ac susceptometer, did not significantly degrade after the growth of overlayer SrTiO3. The capacitance-voltage measurements showed that the dielectric constant of the SrTiO3 films was as high as 315 at a signal frequency of 100 KHz. The leakage current density through the SrTiO3 films is about 1×10-6 A/cm2 at 2-V operation. Data analysis on the current-voltage characteristic indicated that the conduction process is related to bulk-limited Poole-Frenkel emission.

  1. Anisotropic pressure dependence of Tc in single-crystal YBa2Cu3O7 via thermal expansion

    International Nuclear Information System (INIS)

    Meingast, C.; Blank, B.; Buerkle, H.; Obst, B.; Wolf, T.; Wuehl, H.; Selvamanickam, V.; Salama, K.

    1990-01-01

    High-resolution anisotropic-thermal-expansion measurements of single-crystalline and oriented-grained YBa 2 Cu 3 O 7 at the superconducting transition are presented for the first time. Discontinuities in the thermal-expansion coefficient α ab [Δα ab =(15--23)x10 -8 K -1 ], measured with a capacitance dilatometer, are found to occur in both samples. No discontinuity in α c (|Δα c | -8 K -1 ) is observed in either sample, although α c (T) shows a distinct change of slope at T c . The specific-heat discontinuity ΔC p of both samples was also measured and is used, along with the Δα's, to calculate the dependence of T c on uniaxial pressure and uniaxial strain to first order. T c is predicted to increase with pressure applied perpendicular to the c axis (dT c /dp ab =0.04--0.09 K/kbar) and to be insensitive to pressure parallel to the c axis. Uniaxial strain, on the other hand, is found to increase T c about equally in both directions

  2. Preparation of YBa2Cu3O7 films by low pressure MOCVD using liquid solution sources

    International Nuclear Information System (INIS)

    Weiss, F.; Froehlich, K.; Haase, R.; Labeau, M.; Selbmann, D.; Senateur, J.P.; Thomas, O.

    1993-01-01

    A hybrid low pressure MOCVD process is described for reproducible preparation of superconducting thin films of YBa 2 Cu 3 O 7 . The process uses a single solution source of Y, Ba, and Cu β-diketonates dissolved in suitable organic solvents. This liquid precursor is atomized using an ultrasonic aerosol generator and transported as small droplets (∼1μm) into a CVD reactor where solvent and precursor are first evaporated before deposition takes place at low pressure on heated substrates in a cold wall geometry. This process allows, with stable evaporation rates for all three precursors, to grow in-situ superconducting films with constant composition from film to film. Thin and thick films with high critical temperatures and critical currents have been obtained (Tc>80K, Jc>10 4 A/cm 2 at 77K in self field) which are highly c-axis oriented. Experimental details of this new process are described and the effects of different process parameters are studied in order to improve the quality of the deposited layers. (orig.)

  3. The effect of silver nanoparticle size on Jc of YBa2Cu3O7-x superconductor

    International Nuclear Information System (INIS)

    Farbod, M.; Batvandi, M.; Shoushtari, M. Z.

    2007-01-01

    Full text: Critical current density Jc is one of the most important superconducting parameters which is crucial in superconductor's applications. Introducing silver into the superconductors as intergrain filler has been a routine way to increase the Jc. In this work, YBa 2 Cu 3 O 7-x (YBCO), was doped by silver nanoparticles and their effect was studied on Jc as the flux pinning centers. Silver nanoparticles with sizes ranging from 30 to 1000 nm have been prepared using the reduction of silver in ethanol. The stoichiometric amounts of initial material of YBCO superconductor were added to the solution. After evaporation of ethanol, the obtained powder was used to fabricate YBCO samples. The total weight ratio of silver nanoparticles to superconductor was 1:100. The samples were characterized using SEM, EDX and XRD measurements. Jc was measured by a standard four probe technique. The results show by increasing silver nanoparticle size up to 700 nm, Jc increases then decreases by further increase in silver particle size. (authors)

  4. Finite-size effects on the vortex-glass transition in thin YBa2Cu3O7-δ films

    International Nuclear Information System (INIS)

    Woeltgens, P.J.M.; Dekker, C.; Koch, R.H.; Hussey, B.W.; Gupta, A.

    1995-01-01

    Nonlinear current-voltage characteristics have been measured at high magnetic fields in YBa 2 Cu 3 O 7-δ films of a thickness t ranging from 3000 down to 16 A. Critical-scaling analyses of the data for the thinner films (t≤400 A) reveal deviations from the vortex-glass critical scaling appropriate for three-dimensional (3D) systems. This is argued to be a finite-size effect. At large current densities J, the vortices are probed at length scales smaller than the film thickness, i.e., 3D vortex-glass behavior is observed. At low J by contrast, the vortex excitations involve typical length scales exceeding the film thickness, resulting in 2D behavior. Further evidence for this picture is found directly from the 3D vortex-glass correlation length, which, upon approach of the glass transition temperature, appears to level off at the film thickness. The results indicate that a vortex-glass phase transition does occur at finite temperature in 3D systems, but not in 2D systems. In the latter an onset of 2D correlations occurs towards zero temperature. This is demonstrated in our thinnest film (16 A), which, in a magnetic field, displays a 2D vortex-glass correlation length which critically diverges at zero temperature

  5. Probing the phase diagram of cuprates with YBa2Cu3O7 -δ thin films and nanowires

    Science.gov (United States)

    Arpaia, Riccardo; Andersson, Eric; Trabaldo, Edoardo; Bauch, Thilo; Lombardi, Floriana

    2018-02-01

    We have grown and characterized 30-nm-thick YBa2Cu3O7 -δ (YBCO) films, deposited by pulsed laser deposition on both MgO (110) and SrTiO3 (001) substrates, which induce opposite strain to the superconducting layer. By carefully tuning the in situ post-annealing oxygen pressure, we achieved, in a reproducible way, films at different oxygen doping, spanning from the slightly overdoped down to the strongly underdoped region of the phase diagram. The transport properties of the films, investigated through resistance versus temperature measurements, are in perfect qualitative agreement with single crystals. Starting from these films, we have also successfully fabricated nanowires with widths down to 65 nm, at different oxygen doping. The nanostructures exhibit characteristic temperatures (as the critical temperature Tc and the pseudogap temperature T*) similar to those of the as-grown films and carry critical current densities Jc close to the critical depairing value, limited by vortex entry. This implies that the superconducting and the normal state properties of underdoped YBCO are preserved in our films, and they can be studied as a function of the dimensionality of the system, down to the nanoscale.

  6. Improvement in the properties of Ag-doped YBa2Cu3O7-x grain boundary Josephson junctions

    International Nuclear Information System (INIS)

    Bolanos, G.; Baca, E.; Osorio, J.; Prieto, P.

    2000-01-01

    Ag-doped YBa 2 Cu 3 O 7-x (YBCO) thin films using 5 to 20 wt% Ag-doped YBCO targets have been grown by a DC sputtering technique on SrTiO 3 bicrystals. Critical currents of 4 to 5 x 10 6 A/cm 2 at 77 K were measured in YBCO films doped with 5 wt% Ag which has been found to be higher than the value of 1 x 10 6 A/cm 2 measured in undoped samples. The normal resistivity decreases by a doping of 5 wt% Ag and increases for higher Ag concentrations. The critical temperature, T c , of the Ag-YBCO films remained unchanged at 92 K as in the undoped YBCO samples. An I c R n product of 170 μV at 77 K was found in grain boundary Josephson junctions (GBJJs) with 5 wt% Ag, compared with the value of 100 μV measured in undoped samples at the same temperature. Current-voltage characteristics were measured in GBJJs, showing Shapiro steps under microwave radiation and Fraunhofer patterns with an external magnetic field. The improvement in the normal and superconducting properties of Ag-doped YBCO films has been interpreted using the De Genes model to establish that YBCO containing metallic Ag addition shows a superconductor-normal metal-superconductor (S-N-S) behavior, thereby the Ag-doping enhances the weak link behavior and is, therefore, appropriate for electronic applications. (orig.)

  7. Investigation of transverse Peltier effect on top-seeded melt textureYBa2Cu3O7

    International Nuclear Information System (INIS)

    He, Z.H.; Ma, Z.G.; Li, Q.Y.; Luo, Y.Y.; Zhang, J.X.; Meng, R.L.; Chu, C.W.

    1996-01-01

    The transverse Peltier effect is investigated on the top-seeded melt texture superconductor YBa 2 Cu 3 O 7-δ (YBCO). By restricting the heat absorbing or evolving on one of the sample close-quote s surfaces, the Peltier heat flow is converted into a temperature difference for measurement. The temperature difference is found proportional to the current applied, which is in accordance with the prediction of transverse Peltier effect. Based on a simplified model, the difference of the Seebeck coefficients between the ab plane and the c axis, |S ab -S c |, is about 35 μV/K. It is in good agreement with that of large single crystal [I. Terasaki, Y. Sato, S. Tajima, S. Miyamoto, and S. Tanaka, Physica C 235-240, 1413 (1994)]. The transverse Peltier effect is verified. This supports the idea that the off-diagonal thermoelectric effect is responsible for the anomalously high laser-induced transient transverse voltage on the oriented YBCO superconducting thin films. copyright 1996 American Institute of Physics

  8. Magnetoresistance anomalies in ultra-thin granular YBa2Cu3O7−δ bridges

    International Nuclear Information System (INIS)

    Levi, D.; Shaulov, A.; Koren, G.; Yeshurun, Y.

    2013-01-01

    Highlights: •Negative magnetoresistance slope in the Tesla regime is observed at low temperatures. •Phase slips explains the observed magnetoresistance at high temperatures. •Quasiparticles tunneling explains the negative slope. -- Abstract: We report on magnetoresistance measurements in 10 nm thick and submicron-wide granular YBa 2 Cu 3 O 7−δ bridges. The results show a strong dependence of the resistance on the magnetic field at low fields crossing over to a relatively weak field dependence at high fields. The field derivative of the resistance at high fields decreases as the temperature is lowered and eventually changes sign, exhibiting a negative slope in a wide field range in the Tesla regime. This negative slope is sensitive to the bias current, turning to be positive as the bias current increases. This complex magnetoresistance behavior is attributed to both phase slips in a distribution of strongly and weakly linked superconducting grains, and tunneling of quasiparticles between grains. The latter dominates at low temperatures and high fields, giving rise to the negative magnetoresistance slope

  9. Effects of graphene oxide doping on the structural and superconducting properties of YBa2Cu3O7

    Science.gov (United States)

    Dadras, S.; Falahati, S.; Dehghani, S.

    2018-05-01

    In this research we reported the effects of graphene oxide (GO) doping on the structural and superconducting properties of YBa2Cu3O7-δ (YBCO) high temperature superconductors. We synthesized YBCO powder by sol-gel method. After calcination, the powder mixed with different weight percent (0, 0.1, 0.3, 0.7, 1 wt.%) of GO. Refinement of X-ray diffraction (XRD) was carried out by material analysis using diffraction (MAUD) program to obtain the structural parameters such as lattice parameters, site occupancy of different atoms and orthorhombicity value for the all samples. Results show that GO doping does not change the structure of YBCO compound, Cu (1), Cu (2) and oxygen sites occupancy. It seems that GO remains between the grains and can play the role of weak links. We found that GO addition to YBCO compound increases transition temperature (TC). The oxygen contents of the all GO-doped samples are increased with respect to the pure one. The strain (ɛ) of the samples obtained from Williamson-Hall method, varies with increasing of GO doping. The scanning electron microscopy (SEM) images of the samples show better YBCO grain connections by GO doping.

  10. RBS and ion channeling studies of Ag-doped YBa2Cu3O7-δ targets and films

    International Nuclear Information System (INIS)

    Li Yupu; Liu, J.R.; Cui, X.T.; Chu, W.K.

    1998-01-01

    The location of Ag in Ag-doped YBa 2 Cu 3 O 7-δ (YBCO) films and other high-T c materials (such as Ag-doped BiSrCaCuO films and Ag-sheathed textured BiSrCaCuO wires) is a very important issue for improving high-T c materials. In this work, laser ablated and DC magnetron sputtered YBCO films on (100) LaAlO 3 and (100) SrTiO 3 were prepared from sintered Ag-YBCO composite targets (nominally containing 5 wt% Ag) and studied by Rutherford backscattering spectrometry (RBS) and ion channeling techniques using 2.0 MeV 4 He + and 7 Li + beams. We have found that the Ag-YBCO targets contain about 3 wt% Ag and most of the retained Ag atoms form some small size Ag precipitates with a typical size smaller than a few microns. We have demonstrated that in very good single crystalline YBCO films, the percentage of retained Ag in substitutional sites can be estimated by ion channeling technique. For example, we have found that about 1.2 wt% Ag atoms remain in the laser ablated Ag-doped films prepared from the Ag-YBCO target and about two-thirds of the retained Ag atoms occupy substitutional sites. The sputtered films contain less retained Ag atoms since the deposition temperature is higher and deposition time is longer than those for laser ablated films. (orig.)

  11. Melting of the flux line lattice observed by specific heat experiments in YBa2Cu3O7

    International Nuclear Information System (INIS)

    Roulin, M.; Junod, A.; Erb, A.; Walker, E.

    1996-01-01

    High resolution adiabatic specific heat experiments on YBa 2 Cu 3 O 7-δ (0≤δ≤0.05) are performed in magnetic fields from 0 to 14 T (B parallel c and B perpendicular c). In a 0.3 gram, twinned crystal with strong pinning, a step is consistently observed at the melting temperature T m of the vortex solid up to a critical point that depends on δ. The field B m and step temperature T m obey the relation B m =B m0 (δ)(1-T m /T c ) ∼4/3 . The anisotropy of B m and that of the upper critical field B c2 are found to be equal. Alternatively, in a 18 mg, twinned crystal of high purity with low pinning, first-order-like specific heat peaks are observed on the melting line from 8 to 14 T. The entropy under these peaks is ∼0.5 k B /vortex/bilayer. These characteristic features are attributed to the melting of a vortex glass in the former case and that of a vortex lattice in the latter case

  12. High Tc screen-printed YBa2Cu3O(7-x) films - Effect of the substrate material

    Science.gov (United States)

    Bansal, Narottam P.; Simons, Rainee N.; Farrell, D. E.

    1988-08-01

    Thick films of YBa2Cu3O(7-x) have been deposited on highly polished alumina, magnesia spinel, nickel aluminum titanate (Ni-Al-Ti), and barium tetratitanate (Ba-Ti) substrates by the screen printing technique. Properties of the films were found to be highly sensitive to the choice of the substrate material. The film on Ba-Ti turned green after firing, due to a reaction with the substrate and were insulating. A film on Ni-Al-Ti had a Tc (onset) of about 95 K and lost 90 percent of its resistance by about 75 K. However, even at 4 K it was not fully superconducting, possibly due to a reaction between the film and the substrate and interdiffusion of the reaction products. The film on alumina had Tc (onset) of about 96 K, Tc (zero) of about 66 K, and Delta Tc of about 10 K. The best film was obtained on spinel and had Tc (onset) of about 94 K, zero resistance at 81 K, and a transition width of about 7 K.

  13. Tunneling spectroscopy study of YBa2Cu3O7 thin films using a cryogenic scanning tunneling microscope

    International Nuclear Information System (INIS)

    Wilkins, R.; Amman, M.; Soltis, R.E.; Ben-Jacob, E.; Jaklevic, R.C.

    1990-01-01

    We have measured reproducible tunneling spectra on YBa 2 Cu 3 O 7 (T c ∼85 K) thin films (thickness ∼2 μm) with a cryogenic scanning tunneling microscope. We find that the I-V curves are generally of three types. The most common type, featured in a large majority of the data, shows a region of high conductance at zero bias. The amplitude of this region is inversely proportional to the tunneling resistance between the tip and sample. It is possible that this can be explained in terms of Josephson effects within the films, although an alternative is given based on electronic self-energy corrections. Data showing capacitive charging steps are analyzed in terms of two ultrasmall tunnel junctions in series.. Theoretical fits to the data give specific values of the junction parameters that are consistent with the assumed geometry of the tip probing an individual grain of the film. The third type of I-V curves exhibits negative differential resistance. We conclude that this phenomenon is probably due to tunneling to localized states in the surface oxide. We also present and discuss data with energy-gap-like behavior; the best example gives Δ to be about 27 mV

  14. Characterization of defect modes in YBa2Cu3O7-δ thin films probed by Raman scattering

    International Nuclear Information System (INIS)

    Hong, Seongsik; Jo, Hyunchul; Cheong, Hyeonsik; Park, Gwangseo

    2005-01-01

    A Raman analysis is performed on a series of fully oxygenated YBa 2 Cu 3 O 7-δ thin films, on MgO(1 0 0) substrates, deposited by the pulsed laser technique at temperatures between 680 deg C and 820 deg C. θ - 2θ scans of the films by the X-ray diffraction show that the YBCO films are oriented in the c-axis. There are no extra peaks appearing in the X-ray diffraction data. Besides the well-known active modes, however, Raman spectra reveal a number of defect modes. The defect mode at 594 cm -1 redshifts and merges toward the O(4)-A g mode at 502 cm -1 with decreasing deposition temperatures. This mode is significantly asymmetrical and broad, whereas the mode at 243 cm -1 is symmetrical, with a small full width at half maximum remaining unchanged at a value around its own frequency. The intensity of the mode at 243 cm -1 seems to depend on the intensity of the mode at 594 cm -1 . Quantitative calculations concerning the relative intensities show that the two modes are related to each other

  15. Irradiation defect structures in YBa2Cu3O7-x and their correlation with superconducting properties

    International Nuclear Information System (INIS)

    Kirk, M.A.

    1990-11-01

    We review our work on irradiation effects in single crystal YBa 2 CU 3 O 7-x . Transmission electron microscopy has been employed to study the defect microstructures produced by irradiations with fast neutrons, MeV ions (Kr, Ne and p), and electrons. The atomic structure within defect cascades was investigated using 50 keV Kr and Xe ion irradiations to low doses. Evidence is shown for an amorphous structure with some incoherent recrystallization within individual cascades. Correlation with enhancements in critical current density produced by neutron irradiations suggest that this cascade structure effectively pins magnetic flux lines. At sufficiently high fluences of fast neutrons or MeV Kr and Ne ions, a cellular microstructure is found. This structure consists of cells or microcrystallites of good cystalline and superconducting material (in the case of neutron irradiation), with cell walls of amorphous material. Full amorphization proceeds with the growth of cell wall volume. The formation of this microstructure coincides with a decrease in critical transport current, but is not observed by magnetization measurements. Increases in critical current density under proton irradiation, comparable to those produced by neutron irradiation, have been reported. The defect structure produced by proton irradiations is examined here and found to differ from that of neutron irradiations. Our most recent measurements of changes in critical temperature and current density, and defect microstructure following electron irradiations will be described. 20 refs., 6 figs

  16. Study of α-particle injection effect on superconductors YBa2Cu3O7-δ type

    International Nuclear Information System (INIS)

    Santos, G.R.

    1998-01-01

    Various techniques exist to qualify and quantify this radiation damage effect. The methods are based on destructive methods such as TEM, SEM, CREEP and others. This work is intended to be a starting point to the application of nondestructive techniques to study radiation damage in superconductors in nuclear application, and a creation of a nuclear data bank for different type of materials. The first scheduled nondestructive technique to be applied is positron annihilation, more specifically positron lifetime measurements. This work is based on the implementation of a technique, widely used to simulate neutron radiation effects on materials. This simulation is obtained by the injection of charged particles (ions), from an accelerator, and a beam line equipped with some special experimental arrangement to get a homogeneous distribution of injected particles in the sample. After the ion injection, or neutron damage simulation, the nuclear data are collected by different experimental setups: conventional gamma spectrometer for activation analysis, X-ray diffraction for phase change analysis, and zero detector for magnetic permeability measurements. The behavior of the magnetic permeability with temperature of YBa 2 Cu 3 O 7-δ superconducting ceramics was studied as a function of the amount of He -2 implanted into the sample. With fluence varying from 1.2 to 6.0 x 10 6 He -2 cm -2 , the results show that the superconducting temperature T c (onset) stays nearly constant up to 2.5 x 10 6 He -2 cm -2 , decreasing afterwards for higher fluencies. An almost linear decrease is observed for T(offset). The magnetic permeability curves show structures whose shapes and relative positions to T c (onset) change with the fluence. Although this might indicate a mixture of phases coexisting inside the sample, X-ray diffraction shows no clear evidence for such a pattern. A large percentage of the damage recovers after annealing the He-implanted sample at 673 K

  17. A buffer bridge process for growing multiple YBa2Cu3O7-y grains from one top seed

    International Nuclear Information System (INIS)

    Lee, J-H; Park, S-D; Jun, B-H; Lee, J S; Kim, C-J; Han, S C; Han, Y H

    2011-01-01

    This study presents a buffer bridge process that allows growing multiple YBa 2 Cu 3 O 7-y (Y123) grains from one top seed. This process uses a buffer bridge pellet (Y 2 BaCuO 5 or Y123) to deliver the Y123 growth from one seed to several Y123 compacts. The top seeded melt growth (TSMG) process combined with the buffer bridge process facilitated the fabrication of several single-grained Y123 superconductors using one seed. In addition to achieving the growth of multiple Y123 grains, this process ensured a uniform distribution of superconducting properties of the top surface because the seed/compact interface area (the number of seeds), which is the route for the impurities from the seeds, was minimized. Additionally, the impurity contamination from a seed was considerably suppressed using a buffer pellet. One (110) diagonal facet line, as a result of the corner-to-corner growth, developed on the top surfaces of the prepared Y123 compacts, which is comparable to the x-like facet line of the conventional TSMG processed samples. The trapped magnetic field (H) profiles at 77 K of the prepared Y123 compacts, which were estimated using an Nd-B-Fe permanent magnet, showed the H contour map of a single-grain mode. The force-distance curves for the field cooled and zero-field cooled Y123 compacts at 77 K showed high and reliable levitation forces with a small deviation among compacts. The buffer bridge process can be applied to a batch process for the mass production of single-grain REBa 2 Cu 3 O 7-y (RE: rare-earth elements) superconductors with uniform top surface properties.

  18. Epataxial growth of the high-temperature superconductors YBa2Cu3O7-x on silicon single crystals with buffer layers

    International Nuclear Information System (INIS)

    Lubig, A.

    1991-09-01

    In this work the growth of thin films of the high-temperature superconductor YBa 2 Cu 3 O 7-x on Si(001) substrates has been investigated by Rutherford backscattering, channeling, X-ray diffraction, high resolution transmission electron microscopy, and electrical measurements. Epitaxial buffer layers of electrically insulating, pure and yttria-stabilized ZrO 2 ([Y 2 O 3 ] 0.06 [ZrO 2 ] 0.94 = YSZ) as well as of metallic CoSi 2 were employed to largely prevent the interdiffusion and chemical reaction between the superconductor film and the substrate in spite of the high deposition temperatures of the YBa 2 Cu 3 O 7-x in the range of 600 to 800deg C. (orig.)

  19. Relaxation of the electronic states at a thin-layer YBa2Cu 3O7/PrBa2Cu3O7 interface

    KAUST Repository

    Gó mez, Javier Alexandra M; Larkin, Ivan A.; Schwingenschlö gl, Udo

    2010-01-01

    We discuss in detail spin-polarized electronic structure calculations for the 1 × 1 YBa2Cu3O7/PrBa 2Cu3O7 superlattice. Our results are based on the full-potential linear augmented plane wave method and the generalized gradient approximation for the exchange-correlation functional. The on-site Coulomb interaction affecting the correlated Cu 3d and Pr 4f electrons is taken into consideration. At first glance the YBa2Cu3O 7/PrBa2Cu3O7 interface appears to be inert, i.e., the electronic states do not show a clear sign of interaction between the two component materials. Nonetheless, a total energy analysis points to a significant modification of the magnetic coupling in the vicinity of the interface due to the relaxation of the electronic structure. © 2010 Elsevier B.V. All rights reserved.

  20. Experimental Observation of Non-'S-Wave' Superconducting Behavior in Bulk Superconducting Tunneling Junctions of Yba2Cu3O7

    Directory of Open Access Journals (Sweden)

    Leandro Jose Guerra

    1998-06-01

    Full Text Available Evidence of non-s-wave superconductivity from normal tunneling experiments in bulk tunneling junctions of YBa2Cu3O7-δ is presented. The I-V and dI/dV characteristics of bulk superconducting tunneling junctions of YBa2Cu3O7-δ have been measured at 77.0K and clear deviation from s-wave superconducting behavior has been observed. The result agrees with d-wave symmetry, and interpreting the data in this way, the magnitude of the superconducting energy gap, 2Δ, is found to be (0.038 ± 0.002 eV. Comparing this energy gap with Tc (2Δ/kB Tc = 5.735, indicates that these high-Tc superconductors are strongly correlated materials, which in contrast with BCS-superconductors are believed to be weakly correlated.

  1. The influence of growth temperature on the structural characteristics of YBa2Cu3O7-δ films: a Raman scattering study

    International Nuclear Information System (INIS)

    Belousov, M.V.; Davydov, V.Yu.; Sherman, A.B.

    1993-01-01

    Orientation of YBa 2 Cu 3 O 7-δ films at the surface and at the film-(100) MgO substrate interface for various growth temperatures T s have been studied using Raman scattering. On the film-substrate interface the films were c-oriented for T s >670 degrees C and a-oriented for lower growth temperatures. Films grown at T s approximately=670 degrees C to a thickness >0.2 mu m contained a transition from the c- to the a-orientation near the surface. A possible mechanism for the influence of growth temperature on the YBa 2 Cu 3 O 7-δ film orientation is discussed. (author)

  2. Relaxation of the electronic states at a thin-layer YBa2Cu 3O7/PrBa2Cu3O7 interface

    KAUST Repository

    Gómez, Javier Alexandra M

    2010-11-01

    We discuss in detail spin-polarized electronic structure calculations for the 1 × 1 YBa2Cu3O7/PrBa 2Cu3O7 superlattice. Our results are based on the full-potential linear augmented plane wave method and the generalized gradient approximation for the exchange-correlation functional. The on-site Coulomb interaction affecting the correlated Cu 3d and Pr 4f electrons is taken into consideration. At first glance the YBa2Cu3O 7/PrBa2Cu3O7 interface appears to be inert, i.e., the electronic states do not show a clear sign of interaction between the two component materials. Nonetheless, a total energy analysis points to a significant modification of the magnetic coupling in the vicinity of the interface due to the relaxation of the electronic structure. © 2010 Elsevier B.V. All rights reserved.

  3. Análisis de la textura fuera-del-plano en capas superconductoras de YBa2Cu3O7-X

    OpenAIRE

    Sanchez, H.; Bustamante, A.; Osorio, A.; De los Santos, L.; González, J.C.; Barnes, C.H.W.

    2015-01-01

    En el presente trabajo estudiamos la textura de capas superconductoras de YBa2Cu3O7-da través de la difracción de rayos-X. Las capas fueron crecidas sobre el sustrato monocristalino SrTiO3 (100) mediante la deposición de solución química. Posteriormente se sometió la muestra a tratamientos térmicos en una atmósfera oxidante. Una caracterización mediante difracción de rayos-X revela la presencia de reflexiones (00l) para la fase de YBa2Cu3O7-d con una fracción de granos superconductores orient...

  4. Self-injection length in La0.7Ca0.3MnO3–YBa2Cu3 O7−δ ...

    Indian Academy of Sciences (India)

    Critical current, Ic, was measured at 77 K on both the control side as well as the LCMO side for different YBCO film thickness. It was observed that while the control ... devices which are essentially a heterostructure consisting of a layer of YBa2Cu3O7−δ (YBCO), grown over La0.7Ca0.3MnO3 (LCMO). The critical current of.

  5. Particulates reduction in laser-ablated YBa2Cu3O7-δ thin films by laser-induced plume heating

    International Nuclear Information System (INIS)

    Koren, G.; Baseman, R.J.; Gupta, A.; Lutwyche, M.I.; Laibowitz, R.B.

    1990-01-01

    Experimental demonstration of reduction in the number and size of particulates formed in the laser ablation deposition of YBa 2 Cu 3 O 7-δ thin films is obtained by the use of a second laser which further heats and fragments the blowoff material in the plume formed by the first laser. This results in a smoother film with higher critical current density as compared to that obtained without the second laser irradiation of the plume

  6. Heteroepitaxial growth of Ba1 - xSrxTiO3/YBa2Cu3O7 - x by plasma-enhanced metalorganic chemical vapor deposition

    Science.gov (United States)

    Chern, C. S.; Liang, S.; Shi, Z. Q.; Yoon, S.; Safari, A.; Lu, P.; Kear, B. H.; Goodreau, B. H.; Marks, T. J.; Hou, S. Y.

    1994-06-01

    Epitaxial Ba1-xSrxTiO3(BST)/YBa2Cu3O7-x heterostructures with superior electrical and dielectric properties have been fabricated by plasma-enhanced metalorganic chemical vapor deposition (PE-MOCVD). Data of x-ray diffraction and high resolution transmission electron microscopy showed that oriented Ba1-xSrxTiO3 layers were epitaxially deposited on epitaxial (001) YBa2Cu3O7-x layers. The leakage current density through the Ba1-xSrxTiO3 films was about 10-7 A/cm2 at 2 V (about 2×105 V/cm) operation. Moreover, the results of capacitance-temperature measurements showed that the PE-MOCVD Ba1-xSrxTiO3 films had Curie temperatures of about 30 °C and a peak dielectric constant of 600 at zero bias voltage. The Rutherford backscattering spectrometry and x-ray diffraction results showed that the BST film composition was controlled between Ba0.75Sr0.25TiO3 and Ba0.8Sr0.2TiO3. The structural and electrical properties of the Ba1-xSrxTiO3/YBa2Cu3O7-x heterostructure indicated that conductive oxide materials with close lattice to Ba1-xSrxTiO3 can be good candidates for the bottom electrode.

  7. Theoretical investigation of the Fermi surfaces of La2-xSrxCuO4 and YBa2Cu3O7

    International Nuclear Information System (INIS)

    Antonov, V.N.; Antonov, Vl.N.; Bar'yakhtar, V.G.; Baglyuk, A.I.; Maksimov, E.G.; Nemoshkalenko, V.V.; Perlov, A.Ya.; Savrasov, S.Yu.; Uspenskii, Yu.A.

    1989-01-01

    A theoretical investigation is made of the shape of the Fermi surface and of the constant-energy surfaces near the Fermi energy of the La 2-x Sr x CuO 4 and YBa 2 Cu 3 O 7 oxides by a self-consistent linear muffin-tin orbital method in the atomic sphere approximation (OMTO-ASA). It is shown that the Fermi surfaces of these compounds are strongly two-dimensional. The Fermi surface of La 2-x Sr x CuO 4 is a corrugated rounded box centered at the point Λ. The Fermi surface of YBa 2 Cu 3 O 7 consists of four sheets: an electron cushion at the point Λ and three nested hole surfaces centered at the point S. The electron cushion and one of the hole surfaces are strongly corrugated along the z direction. The theoretically calculated Fermi surfaces of La 2 CuO 4 and YBa 2 Cu 3 O 7 are compared with the experimental data on electron-positron annihilation

  8. Ca doping of TSMTG-YBa2Cu3O7-δ/Y2BaCuO5 composites

    International Nuclear Information System (INIS)

    Delorme, F.; Harnois, C.; Monot-Laffez, I.; Marinel, S.

    2002-01-01

    Calcium doped YBa 2 Cu 3 O 7-δ /Y 2 BaCuO 5 bulk samples have been synthesised by the top-seeding-melt-texture growth (TSMTG) process up to 1 wt.% of CaCO 3 . Calcium additions up to 0.25 wt.% of CaCO 3 do not change the decomposition temperature whereas additions of 1 wt.% of CaCO 3 lead to an increase of the decomposition temperature of about 10 deg. C. This difference is not important enough to change the thermal cycle used to process YBa 2 Cu 3 O 7-δ undoped bulk samples. Microstructure studies show that no precursor or secondary phases containing calcium are present in the samples. Energy dispersive spectroscopy analyses have shown that Ca is present both in the YBa 2 Cu 3 O 7-δ matrix and the Y 2 BaCuO 5 particles. The position of the calcium atoms in the superconducting matrix is discussed. The calcium doped samples present slightly depressed critical temperatures but drastically depressed critical current densities

  9. Interface structure and electronic properties of SrTiO3 and YBa2Cu3O7-δ crystals and thin films

    International Nuclear Information System (INIS)

    Thiess, S.

    2007-01-01

    Two new extensions of the X-ray standing wave (XSW) technique, made possible by the intense highly collimated X-ray beams from undulators at the ESRF, are described in this thesis. First, the XSW method was applied in a structural study to solve the nucleation mechanism of the high temperature superconductor YBa 2 Cu 3 O 7-δ on the (001) surface of SrTiO 3 . Second, the valence electronic structures of SrTiO 3 and YBa 2 Cu 3 O 7-δ were investigated. Finally, recent developments in the field of photoelectron spectroscopy in the hard X-ray region are described. The X-ray standing wave method is used in combination with fluorescence, Auger or photoelectron spectroscopy and lends very high spatial resolution power to these analytical techniques. Previously, the XSW method has been used for structure determination of surfaces and interfaces. The currently available X-ray intensities permit extensions to the XSW technique. Two recently established applications, described in this thesis, are XSW real space imaging and XSW valence electronic structure analysis. XSW real space imaging was employed to analyse the atomic structure of 0.5 and 1.0 layers of YBa 2 Cu 3 O 7-δ deposited on SrTiO 3 (001). Three-dimensional images of the atomic distributions were reconstructed for each of the elements from experimentally determined Fourier components of the atomic distribution functions. The images confirmed the formation of a perovskite precursor phase prior to the formation of the YBa 2 Cu 3 O 7-δ phase during the growth of the first monolayer of the film. XSW valence electronic structure analysis applied to SrTiO 3 identified the valence band contributions arising from the strontium, titanium, and oxygen sites of the crystal lattice. Relations between the site-specific valence electronic structure and the lattice structure were established. The experimental results agree very well with predictions by state-of-the-art ab initio calculations. X-ray absorption cross sections for

  10. The high temperature superconductor YBa2Cu3O7-δ: symmetry of the order parameter, and gradiometers for biomagnetic applications

    International Nuclear Information System (INIS)

    Kouznetsov, Konstantin A.

    1999-01-01

    The cuprate YBa 2 Cu 3 O 7-δ is the material that drives the majority of the technological applications of high transition temperature (Tc) superconductors, particularly in the area of superconducting electronics. Despite the widespread use of high-Tc superconducting materials in a variety of applications, the nature of the superconducting state in these materials remains unknown since their discovery more than a decade ago. Many properties of the high-Tc superconductors are determined by their order parameter, which is a wavefunction describing the superconducting condensate. The symmetry of the order parameter in cuprates has been the subject of intensive investigation, leading to conflicting sets of results. Some experiments supported conventional, s-wave symmetry of the order parameter, while others indicated an unconventional, d-wave symmetry. The first part of this thesis is an experimental study of the symmetry of the order parameter in YBa 2 Cu 3 O 7-δ . A new class of phase sensitive experiments is described that involve Josephson tunneling along the c-axis of twinned crystals of YBa 2 Cu 3 O 7-δ . These experiments showed that an s-wave component must reverse sign across the twin boundary, providing direct evidence for a mixed, s+d symmetry of the order parameter in YBa 2 Cu 3 O 7-δ , and thereby reconciling two conflicting sets of previous findings and establishing the dominant d-wave pairing symmetry. The second part of the thesis focuses on practical applications of YBa 2 Cu 3 O 7-δ in superconducting electronics. The authors introduce a novel Superconducting Quantum Interference Device (SQUID) gradiometer. The principle of operation of these long baseline high-T c SQUID gradiometers is based on the inductive coupling of the input coil of a planar flux transformer to the pickup up loop of a directly coupled magnetometer. The long baseline of the gradiometer, 48 mm, and the intrinsic. Balance of better than 1 part in 100 make it an ideal candidate

  11. Imaging, manipulation and flux noise of single Abrikosov vortices in YBa2Cu3O7-δ dc SQUIDs

    International Nuclear Information System (INIS)

    Bailer, Matthias

    2013-01-01

    The thesis deals with the imaging and investigation of single Abrikosov vortices in grain boundary dc SQUIDs1 from the high-temperature superconductor YBa 2 Cu 3 O 7-δ . The low temperature scanning electron microscopy (LTSEM) was used for the measurements, which makes a local, spatially resolved investigation of the electrical properties of materials at low temperatures possible. The advantage over other flux quantum imaging methods is the facility to determine the low-frequency flux noise in the SQUID in the process. Special SQUID designs were created, which allow a reproducible cooling of single flux quanta. Electrical transport and noise measurements were carried out to precharacterise the SQUIDs. Within the scope of the thesis it was the first time that antivortices were imaged with the LTSEM. The possibilities of a manipulation of flux quanta (with the electron beam) were investigated and illustrated. By the averaged measurement of the waveform of a single vortex, linescans with unprecedented resolution could be obtained. This allowed the outstanding comparison of the measured, virtual vortex displacement with various theoretically determined waveforms. The experiments to flux noise provided new insights into the noise behaviour of single flux quanta, which exhibit the typical single fluctuators random telegraph signal, and enabled the analysis of the associated hopping processes. Thus concrete values of the spectral noise power density S r ∼ 196 nm 2 /root(Hz) - 0,28 μm 2 /root(Hz) radially to the SQUID hole could be determined by different, pinned vortices. An influence of the hopping behaviour and therefore of the flux noise succeeded by varying an applied magnetic field. Through tilting the potential course of a vortex, the course of the pinning potential by different hopping processes could be reconstructed using stochastic analysis of the time trace data. With the thesis could be shown convincingly that the vortex imaging method of the LTSEM in

  12. Transport properties of YBa2Cu3O7/PrBa2Cu3O7-superlattices

    International Nuclear Information System (INIS)

    El Tahan, Ayman Mohamed Moussa

    2010-01-01

    The understanding of the coupling between superconducting YBa 2 Cu 3 O 7 (YBCO) layers decoupled by non superconducting PrBa 2 Cu 3 O 7 (PBCO) layers in c-axis oriented superlattices was the aim of this thesis. For this purpose two conceptually different kind of transport experiments have been performed. In the first type of transport experiments the current is flowing parallel to the layers. Here the coupling is probed indirectly using magnetic vortex lines, which are penetrating the superlattice. Movement of the vortex segments in neighbouring YBCO layers is more or less coherent depending on the thickness of both the superconducting and non superconducting layers. This in-plane transport was measured either by sending an external current through bridges patterned in the superlattice or by an induced internal current. The vortex-creep activation energy U was determined by analysis of the in-plane resistive transition in an external magnetic field B oriented along the c-axis. The activation energies for two series of superlattices were investigated. In one series the thickness of the YBCO layers was constant (n Y =4 unit cells) and the number of the PBCO unit cells was varied, while in the other the number of PBCO layers was constant (n P =4) and n Y varied. The correlation length of the vortex system was determined to be 80 nm along the c-axis direction. It was found that even a single PBCO unit cell in a superlattice effectively cuts the flux lines into shorter weakly coupled segments, and the coupling of the vortex systems in neighbouring layers is negligible already for a thickness of four unit cells of the PBCO layers. A characteristic variation of the activation energy for the two series of superlattices was found, where U 0 is proportional to the YBCO thickness. A change in the variation of U 0 with the current I in the specimen was observed. The analysis of standard dc magnetization relaxation data obtained for a series superlattices revealed the

  13. Transformational dynamics of BZO and BHO nanorods imposed by Y2O3 nanoparticles for improved isotropic pinning in YBa2Cu3O7 -δ thin films

    Science.gov (United States)

    Gautam, Bibek; Sebastian, Mary Ann; Chen, Shihong; Shi, Jack; Haugan, Timothy; Xing, Zhongwen; Zhang, Wenrui; Huang, Jijie; Wang, Haiyan; Osofsky, Mike; Prestigiacomo, Joseph; Wu, Judy Z.

    2017-07-01

    An elastic strain model was applied to evaluate the rigidity of the c-axis aligned one-dimensional artificial pinning centers (1D-APCs) in YBa2Cu3O7-δ matrix films. Higher rigidity was predicted for BaZrO3 1D-APCs than that of the BaHfO3 1D-APCs. This suggests a secondary APC doping of Y2O3 in the 1D-APC/YBa2Cu3O7-δ nanocomposite films would generate a stronger perturbation to the c-axis alignment of the BaHfO3 1D-APCs and therefore a more isotropic magnetic vortex pinning landscape. In order to experimentally confirm this, we have made a comparative study of the critical current density Jc (H, θ, T) of 2 vol.% BaZrO3 + 3 vol.%Y2O3 and 2 vol.%BaHfO3 + 3 vol.%Y2O3 double-doped (DD) YBa2Cu3O7-δ films deposited at their optimal growth conditions. A much enhanced isotropic pinning was observed in the BaHfO3 DD samples. For example, at 65 K and 9.0 T, the variation of the Jc across the entire θ range from θ=0 (H//c) to θ=90 degree (H//ab) is less than 18% for BaHfO3 DD films, in contrast to about 100% for the BaZrO3 DD counterpart. In addition, lower α values from the Jc(H) ˜ H-α fitting were observed in the BaHfO3 DD films in a large θ range away from the H//c-axis. Since the two samples have comparable Jc values at H//c-axis, the improved isotropic pinning in BaHfO3 DD films confirms the theoretically predicted higher tunability of the BaHfO3 1D-APCs in APC/YBa2Cu3O7-δ nanocomposite films.

  14. Artificial in-plane ordering of textured YBa2Cu3O(7-x) films deposited on polycrystalline yttria-stabilized zirconia substrates

    Science.gov (United States)

    Harshavardhan, K. S.; Rajeswari, M.; Hwang, D. M.; Chen, C. Y.; Sands, T. D.; Venkatesan, T.; Tkaczyk, J. E.; Lay, K. W.; Safari, A.; Johnson, L.

    1992-12-01

    Anisotropic surface texturing of the polycrystalline yttria-stabilized zirconia substrates, prior to YBa2Cu3O(7-x) film deposition, is shown to promote in-plane (basal plane) ordering of the film growth in addition to the c-axis texturing. The Jc's of the films in the weak-link-dominated low-field regime are enhanced considerably, and this result is attributed to the reduction of weak links resulting from a reduction in the number of in-plane large-angle grain boundaries.

  15. Hole filling and interlayer coupling in YBa2Cu3O7/PrBa2Cu3O7 superlattices

    International Nuclear Information System (INIS)

    Biagini, M.; Calandra, C.; Ossicini, S.

    1995-01-01

    Charge transfer effects in YBa 2 Cu 3 O 7 /PrBa 2 Cu 3 O 7 superlattices have been proposed by many authors as the origin of the experimentally observed strong depression of the critical temperature. We performed self-consistent LMTO-ASA calculations and found that no remarkable change in the electronic structure of the superconducting CuO 2 planes occurs in the studied structures, when the PBCO layer thickness is varied. The observed depression of the critical temperature does not seem to be originated intrinsically by a severe modification of the electronic structure or by the hole-filling mechanism. (orig.)

  16. The Role of the Apex Oxygen for the Electronic Properties of YBa2Cu3O7 and its Relation to Raman Scattering

    International Nuclear Information System (INIS)

    Ambrosch-Draxl, C.; Abt, R.; Knoll, P.

    1995-01-01

    We investigate the changes of the total energy, the electronic bands, and the dielectric function with the displacement of the apical oxygen position in YBa 2 Cu 3 O 7 by LAPW-calculations. From these data we calculate the corresponding vibronic Raman-spectrum. Anharmonic terms of the vibrational potential and higher order derivatives of the dielectric function are taken into account. We find excellent agreement with experimental data for the phonon frequency as well as for the intensities of fundamental and overtone spectra within a wide temperature range

  17. Frequency and amplitude response of the flux-line lattice to mechanical perturbation in ceramic YBa 2Cu 3O 7

    Science.gov (United States)

    Luzuriaga, J.; André, M.-O.; Benoit, W.

    1992-10-01

    The mechanical response of the flux-line lattice has been measured with a low-frequency forced pendulum in ceramic YBa 2Cu 3O 7. A dissipation peak observed in temperature sweeps is frequency-independent between 1 mHz and 5 Hz. Dissipation depends strongly on applied torque, and for fixed temperatures this dependence is well fitted by a rheological model of extended dry friction. If the model is extended to take account of thermal activation, however, it does not agree with the measured frequency independence, which is hard to explain within simple models of thermal activation.

  18. Correlation of tunneling spectra with surface nano-morphology and doping in thin YBa2Cu3O7-delta films

    OpenAIRE

    Sharoni, A.; Koren, G.; Millo, O.

    2001-01-01

    Tunneling spectra measured on thin epitaxial YBa2Cu3O7-delta films are found to exhibit strong spatial variations, showing U and V-shaped gaps as well as zero bias conductance peaks typical of a d-wave superconductor. A full correspondence is found between the tunneling spectra and the surface morphology down to a level of a unit-cell step. Splitting of the zero bias conductance peak is seen in optimally-doped and overdoped films, but not in the underdoped ones, suggesting that there is no tr...

  19. On low frequency dynamics of CuO finite chains in YBa2Cu3O7-δ type high-tc superconductors

    International Nuclear Information System (INIS)

    Stasyuk, I.V.; Kotsur, S.S.; Ivankiv, A.L.; Dublenich, Yu.I.

    1992-01-01

    A problem of vibration spectrum of a crystal, featuring availability of sublattices with sufficient anharmonicity of single-ion potential is considered. Dynamics of Cu (1) O (1) finite chains in YBa 2 Cu 3 O 7-δ type crystals is studies on the basis of pseudo-spin model. Dependences of chains vibration spectra with small number of fragments on theory parameters are obtained. It is shown that in low-energy spectrum part there is a transition (from the main state), which energy decreases with increase of chain fragments number. Intensities of vibration transitions between the levels are calculated

  20. Improvement of the superconducting transition and demagnetization factor in YBa2Cu3O7-δ single crystals by laser cutting

    International Nuclear Information System (INIS)

    Bhattacharya, A.; Grupp, D.E.; Goldman, A.M.; Welp, U.

    1996-01-01

    Single crystals of YBa 2 Cu 3 O 7-δ have been cut into disc shapes using an excimer laser. The bulk superconducting transition was found to be sharpened in all cases measured. This is associated with the removal of material at the edges which may be depleted of oxygen or otherwise damaged. The magneto-optical images for one crystal have been correlated with the optical image. The angular dependence of the demagnetizing factor for field applied in the plane was drastically reduced in disc-shaped crystals relative to rectangular ones. The field of first flux entry was also increased. copyright 1996 American Institute of Physics

  1. Insulating nanoparticles on YBa2Cu3O7-δ thin films revealed by comparison of atomic force and scanning tunneling microscopy

    International Nuclear Information System (INIS)

    Thomson, R.E.; Moreland, J.; Missert, N.; Rudman, D.A.; Sanders, S.C.; Cole, B.F.

    1993-01-01

    The surface topography of YBa 2 Cu 3 O 7-δ thin films has been studied with both atomic force microscopy (AFM) and scanning tunneling microscopy (STM). The AFM images reveal a high density of small distinct nanoparticles, 10--50 nm across and 5--20 nm high, which do not appear in STM images of the same samples. In addition, we have shown that scanning the STM tip across the surface breaks off these particles and moves them to the edge of the scanned area, where they can later be imaged with the AFM

  2. Magnetoresistance in La0.7Ca0.3MnO3-YBa2Cu3O7 F/S/F trilayers

    International Nuclear Information System (INIS)

    Pena, V.; Visani, C.; Bruno, F.; Garcia-Barriocanal, J.; Arias, D.; Rivera, A.; Sefrioui, Z.; Leon, C.; Te Velthuis, S.G.E.; Hoffmann, A.; Nemes, N.; Garcia-Hernandez, M.; Martinez, J.L.; Santamaria, J.

    2007-01-01

    We report large magnetoresistance in ferromagnet/superconductor/ferromagnet structures made of La 0.7 Ca 0.3 MnO 3 and YBa 2 Cu 3 O 7 at temperatures along the resistive transition. We find that the magnetoresistance phenomenon is independent on the orientation of electric current versus field. Furthermore, the effect is also independent on the sweep rate of the magnetic field. This excludes interpretations in terms of spontaneous vortices or anisotropic magnetoresistance of the ferromagnetic layers and supports the view that the magnetoresistance phenomenon originates at the spin-dependent transport of quasiparticles transmitted from the ferromagnetic electrodes into the superconductor

  3. Formation of high-Tc YBa2Cu3O(7-delta) films on Y2BaCuO5 substrate

    Science.gov (United States)

    Wang, W. N.; Lu, H. B.; Lin, W. J.; Yao, P. C.; Hsu, H. E.

    1988-07-01

    High-Tc superconducting YBa2Cu3O(7-delta) films have been successfully prepared on green Y2BaCuO5 (2115) ceramic substrate. The films have been formed by RF sputtering and screen printing with post annealing at 925 C. Regarding superconducting features, the sharp resistivity drop with Tc onset around 95 K (midpoint 84 K) and 99 K (midpoint 89 K) has been observed for RF sputtered and printed films respectively. Both films show the excellent adhesion towards the 2115 substrate. Powder X-ray diffraction profiles indicate a majority of 1237 phase with preferred orientation for RF sputtered thin film.

  4. Effects of Ca doping and O deficiency on the charge distribution in the vicinity of a 45° [001] grain boundary in YBa2Cu3O7

    KAUST Repository

    Schwingenschlögl, Udo

    2012-02-01

    The charge redistribution at grain boundaries is critical for the applicability of high-T c superconductors in electronic devices, because it determines the transport across the material. We investigate the charge transfer and the alterations of the electronic states due to local doping of a normal-state 45°-tilted [001] grain boundary in YBa 2Cu 3O 7 by means of first-principles calculations. Considering Ca doping and O deficiency as prototypical modifications we demonstrate that the redistribution of the charge carriers in the CuO 2 planes displays a very complex spatial pattern, which deviates even qualitatively from the naive expectation. Copyright © EPLA, 2012.

  5. Correlations between the Hall coefficient and the superconducting transport properties of oxygen-deficient YBa2Cu3O7-δ epitaxial thin films

    International Nuclear Information System (INIS)

    Jones, E.C.; Christen, D.K.; Thompson, J.R.; Feenstra, R.; Zhu, S.; Lowndes, D.H.; Phillips, J.M.; Siegal, M.P.; Budai, J.D.

    1993-01-01

    Strong correlations between the Hall coefficient R H , the transition temperature T c , and the critical current density J c were established in a series of epitaxial YBa 2 Cu 3 O 7-δ thin films as a function of oxygen deficiency δ. Steady increases in R H with δ suggest that deoxygenation reduces the density of states which, according to BCS theory, should lead to corresponding decreases in T c . In contrast, two well-known plateaus occurring at 90 K and 60 K were observed in T c vs δ. Others have ascribed these plateaus to either electronic phenomena or phase separations. We find that in the 90-K plateau, the critical current density J c (δ,H=0) decreases with δ and extrapolates toward zero at the edge of the plateau, while the relative-field dependence of J c (δ,H) and the flux-creep pinning energies are independent of δ. These observations suggest that the phase-separation scenario occurs on the 90-K plateau. However, electronic origins cannot be ruled out at present due to difficulties in determining the equilibrium superconducting properties of oxygen-deficient YBa 2 Cu 3 O 7-δ films

  6. Geometric and compositional factors on critical current density in YBa2Cu3O7‑δ films containing nanorods

    Science.gov (United States)

    Horide, Tomoya; Nagao, Sho; Izutsu, Ryosuke; Ishimaru, Manabu; Kita, Ryusuke; Matsumoto, Kaname

    2018-06-01

    Critical current density (J c) was investigated in YBa2Cu3O7‑δ films containing nanorods prepared with various nanorod materials, with variation of nanorod content, substrate temperature, and oxidization condition. Three types of compositional situation were realized: films containing strain induced oxygen vacancies; fully oxidized films containing cation compositional deviation; and oxygen deficient films. Normalized J c‑B behavior was determined via the matching field, which is a geometric factor, regardless of the compositional details. A J c‑critical temperature (T c) relation depending on distribution and fraction of compositional deviation (cation compositional deviation and strain induced oxygen vacancies) was found: the J c values decreased with decreasing T c due to the effect of T c on nanorod pinning strength in the fully oxidized films; J c decreased with decreasing oxygen pressure in the film cooling process after film deposition in spite of T c remaining almost the same, due to reduction of the effective area for current flow in the oxygen deficient films. Thus, a J c landscape based on geometric and compositional factors was obtained. The study highlights the importance of the J c‑T c analysis in the understanding of J c in YBa2Cu3O7‑δ films containing nanorods.

  7. MOCVD with gas phase composition control for the growth of high quality YBa2Cu3O7-x thin films for microwave applications

    International Nuclear Information System (INIS)

    Musolf, J.

    1997-01-01

    The MOCVD growth technique has demonstrated YBa 2 Cu 3 O 7-x thin films with adequate transport properties (T c >90 K, J c > x 10 6 A cm -2 , R s p /C v ) and the species concentrations. After determining the correlation between gas phase and solid phase composition this technique enables the reproducible growth of YBa 2 Cu 3 O 7-x thin films by MOCVD with composition very close to 123. Further refinement of growth temperature, total pressure, oxygen partial pressure and total flow rates has produced films with excellent properties. Smooth surface morphology with a low density of outgrowths ( 4 cm -2 ), narrow XRD rocking curve peaks FWHM c =92 K), low surface resistance (device R s <350 μΩ at 77 K, 10 GHz) have been demonstrated using this growth concept. Special focus was placed on optimization of the performance of a microwave test device which serves as a process control monitor of the suitability of these films for passive microwave applications. (orig.)

  8. Pair Distribution Function Analysis of ZrO2 Nanocrystals and Insights in the Formation of ZrO2-YBa2Cu3O7 Nanocomposites

    Directory of Open Access Journals (Sweden)

    Hannes Rijckaert

    2018-06-01

    Full Text Available The formation of superconducting nanocomposites from preformed nanocrystals is still not well understood. Here, we examine the case of ZrO2 nanocrystals in a YBa2Cu3O7−x matrix. First we analyzed the preformed ZrO2 nanocrystals via atomic pair distribution function analysis and found that the nanocrystals have a distorted tetragonal crystal structure. Second, we investigated the influence of various surface ligands attached to the ZrO2 nanocrystals on the distribution of metal ions in the pyrolyzed matrix via secondary ion mass spectroscopy technique. The choice of stabilizing ligand is crucial in order to obtain good superconducting nanocomposite films with vortex pinning. Short, carboxylate based ligands lead to poor superconducting properties due to the inhomogeneity of metal content in the pyrolyzed matrix. Counter-intuitively, a phosphonate ligand with long chains does not disturb the growth of YBa2Cu3O7−x. Even more surprisingly, bisphosphonate polymeric ligands provide good colloidal stability in solution but do not prevent coagulation in the final film, resulting in poor pinning. These results thus shed light on the various stages of the superconducting nanocomposite formation.

  9. Investigation of Optically Modified YBa2Cu3O7–x Films by Means of X-ray Microanalysis Technique

    Directory of Open Access Journals (Sweden)

    Artūras JUKNA

    2014-06-01

    Full Text Available This work reports on investigation of remnant oxygen content in optically-modified regions of 0.3-mm-thick YBa2Cu3O7–x films, patterned by a laser-writing technique in an inert ambient gas atmosphere at room temperature. A laser-treated region of weak superconductivity with dimensions depending on the size of a laser spot, laser power, and initial content of oxygen is characterized by a lower oxygen content, weaker critical magnetic field, and suppressed both the superconducting critical temperature and the critical current density, as compared to the laser untreated regions. Optically induced (cw-laser, 532-nm-wavelength heating strongly affects a non-uniform distribution of remnant oxygen content in the film, depending both on the optical power and beam’s scanning velocity. A level of oxygen depletion and the size of the oxygen-deficient region have been directly estimated from scanning-electron-microscope spectra with the X-ray microanalysis technique. The results of our measurements were compared with results extracted from electric measurements, assuming a correlation between the remnant oxygen content and the electric transport properties of oxygen-deficient YBa2Cu3O7–x films. DOI: http://dx.doi.org/10.5755/j01.ms.20.2.6323

  10. Structural and superconducting characteristics of YBa2Cu3O7 films grown by fluorine-free metal-organic deposition route

    DEFF Research Database (Denmark)

    Zhao, Yue; Chu, Jingyuan; Qureishy, Thomas

    2018-01-01

    Microstructure and superconducting performance of YBa2Cu3O7 (YBCO) films deposited on LaAlO3 single crystal (LAO) substrates by a fluorine-free metal-organic deposition (FF-MOD) technique, have been studied by means of X-ray reciprocal space mapping (RSM), cross-sectional transmission electron mi...... external magnetic field at 77 K. This work offers an in-depth insight into the correlation between the microstructure and superconductivity in the MOD YBCO films.......Microstructure and superconducting performance of YBa2Cu3O7 (YBCO) films deposited on LaAlO3 single crystal (LAO) substrates by a fluorine-free metal-organic deposition (FF-MOD) technique, have been studied by means of X-ray reciprocal space mapping (RSM), cross-sectional transmission electron....... It is suggested that associated partial dislocations formed at the boundary between the stacking faults and YBCO matrix act as strong linear (or dot) pinning centers. These structural characteristics are well in line with the better superconducting performance of the low fluorine-MOD film, in particular under...

  11. Pushing and trapping phenomena in YBa2Cu3O7 melt-textured composites with BaZrO3 and Ag additions

    International Nuclear Information System (INIS)

    Carrillo, A E; Puig, T; Obradors, X

    2005-01-01

    A new Ag trapped particle morphology has been discovered in melt-textured YBa 2 Cu 3 O 7 /Ag composites where the interface energy between particle inclusions and a solid matrix has been enhanced with BaZrO 3 additives. The enhanced pushing effect generates square-like macrosegregation bands where the secondary additives Y 2 BaCuO 5 , BaZrO 3 , and Ag are accumulated. It is shown that elongated Ag particles with a long axis ∼ 60-120 μm and aspect ratios as high as a ∼ 12 can be trapped in the YBa 2 Cu 3 O 7 matrix free of any other additive with a very anisotropic orientation. It is demonstrated that the elongated Ag particles lie with the long axis parallel to the growth direction in all the growth sectors generated by the top seeding growth. The pushing-trapping theory is used to explain qualitatively the unusual phenomenon of a growth-induced morphological shaping of inclusion particles

  12. Critical current density in (YBa2Cu3O7−δ)1−x–(PrBa2Cu3O7−δ)x melt-textured composites  

    DEFF Research Database (Denmark)

    Opata, Yuri Aparecido; Monteiro, João Frederico Haas Leandro; Jurelo, Alcione Roberto

    2018-01-01

    Melt textured (YBa2Cu3O7−δ)1−x–(PrBa2Cu3O7−δ)x composites (x = 0.00 and x = 0.05) were grown using the top seeding method. The effect of the PrBa2Cu3O7−δ phase on the growth process and the modification of the microstructure as well as on the physical properties was analyzed. X-ray analyses...... indicated that both pure and Pr-doped samples present an orthorhombic superconducting phase. From resistivity measurements for YBa2Cu3O7−δ and (YBa2Cu3O7−δ)0.95–(PrBa2Cu3O7−δ)0.05 samples, the Tcab did not change and was around 90.5 K. However, from magnetic measurements, the superconductivity was observed...... in critical temperatures TC = 92.9 K and 92.4 K for YBa2Cu3O7−δ and (YBa2Cu3O7−δ)0.95–(PrBa2Cu3O7−δ)0.05 samples, respectively. The YBa2Cu3O7−δ sample showed higher critical current densities than those shown by the (YBa2Cu3O7−δ)0.95–(PrBa2Cu3O7−δ)0.05 sample, with values of JC = 5.85 × 105 A/cm2 and 4...

  13. Momentum Dependence of Charge Excitations in YBa2Cu3O7-δ and Nd2-xCexCuO4

    Science.gov (United States)

    Ishii, Kenji

    2006-03-01

    Resonant inelastic x-ray scattering (RIXS) studies at Cu K-edge on high-Tc superconducting cuprates, YBa2Cu3O7-δ and Nd2-xCexCuO4 are presented. The superconductivity occurs in the vicinity of the Mott insulating state and it is important to clarify the nature of the Mott gap and its doping dependence. Because RIXS has an advantage that we can measure charge excitation in a wide energy-momentum space, it gives a unique opportunity to study the electronic structure of materials. We apply this technique to high-Tc superconducting cuprates. In particular the electronic structure of strongly correlated metals is in the focus of our RIXS study. The experiments were performed at BL11XU of SPring-8, Japan, where a specially designed spectrometer for inelastic x-ray scattering is installed. In optimally doped YBa2Cu3O7-δ, anisotropic spectra are observed in the ab plane of a twin-free crystal. The Mott gap excitation from the one-dimensional CuO chain is enhanced at 2 eV near the zone boundary of the chain direction, while the excitation from the CuO2 plane is broad at 1.5-4 eV and almost independent of momentum. Theoretical calculation based on the one-dimensional and two-dimensional Hubbard model reproduces the observed features in the RIXS spectra when smaller values of the on-site Coulomb energy of the chain than that of the plane are assumed. This means that the charge transfer gap of the chain is smaller than that of the plane. On the other hand, both interband excitation across the Mott gap and intraband excitation in the upper Hubbard band are observed in the electron-doped Nd2-xCexCuO4. The intensity of the interband excitation is concentrated at ˜ 2 eV near the zone boundary while a dispersion relation with a momentum-dependent width emerges in the intraband excitation. The author would like to acknowledge to his collaborators, K. Tsutsui, Y. Endoh, T. Tohyama, K. Kuzushita, T. Inami, K. Ohwada, M. Hoesch, M. Tsubota, Y. Murakami, J. Mizuki, S. Maekawa, T

  14. Self-assembled, rare earth tantalate pyrochlore nanoparticles for superior flux pinning in YBa2Cu3O7-δ films

    International Nuclear Information System (INIS)

    Harrington, S A; Durrell, J H; Wimbush, S C; Kursumovic, A; MacManus-Driscoll, J L; Maiorov, B; Wang, H; Lee, J H

    2009-01-01

    Addition of pyrochlore rare earth tantalate phases, RE 3 TaO 7 (RTO, where RE = rare earth, Er, Gd and Yb) to YBa 2 Cu 3 O 7-δ (YBCO) is shown to vastly improve pinning, without being detrimental to the superconducting transition temperature. The closely lattice matched to RTO phase provides a lower interfacial energy with YBCO than BaZrO 3 (BZO) and produces very fine (∼5 nm) particles with high linearity in their self-assembly along c. Critical current densities of 0.86, 0.38 MA cm -2 at 1 and 3 T (for fields) parallel to the c axis were recorded at 77 K in 0.5-1.0 μm thick films and a transition temperature of 92 K was observed even in the highest level doped sample (8 mol%). (rapid communication)

  15. Fabrication of 2-3 YBa2Cu3O7-x/polymer composite with Tc above liquid nitrogen temperature

    International Nuclear Information System (INIS)

    Wilson, C.M.; Safari, A.

    1990-01-01

    This paper reports on high T c superconducting oxide woven networks fabricated and used to form YBa 2 Cu 3 O 7-x /polymer composites showing a superconducting resistive transition above liquid nitrogen temperature. The ceramic network was produced by soaking biaxially woven carbon fabric in a solution containing the stoichiometric proportions of Y, Ba, and Cu. Decomposition of the infiltrated carbon fabric and reaction of the remaining oxides resulted in a ceramic replica of the original fabric. The fired networks had a strand diameter ∼100 μm and were embedded in a polymer matrix to produce 2--3 superconducting/polymer composites with a superconducting transition of ∼89 K. Linear shrinkage of the networks was constrained during firing, although the radial shrinkage of the superconducting strands occurred freely. XRD of the networks indicated the presence of BaCO 3 , CuO, and BaCuO 2 as impurity phases

  16. Epitaxial YBa2Cu3O7 on biaxially textured (001) Ni: An approach to high critical current density superconducting tapes

    International Nuclear Information System (INIS)

    Norton, D.P.; Goyal, A.; Budai, J.D.

    1997-01-01

    In-plane aligned, c-axis oriented YBa 2 Cu 3 O 7 (YBCO) films with superconducting critical current densities, J c , as high as 700,000 amperes per square centimeter at 77 kelvin have been grown on thermo-mechanically, rolled-textured (001) Ni tapes using pulsed-laser deposition. Epitaxial growth of oxide buffer layers directly on biaxially textured Ni, formed by recrystallization of cold-rolled pure Ni, enables the growth of 1.5 micrometer-thick YBCO films with superconducting properties that are comparable to those observed for epitaxial films on single crystal oxide substrates. This result represents a viable approach for producing long-length superconducting tapes for high current, high field applications at 77 kelvin

  17. High-temperature equilibrium study of the oxygen-site occupancy in YBa2Cu3O7-δ by positron annihilation

    International Nuclear Information System (INIS)

    Hermes, H.; Forster, M.; Schaefer, H.

    1991-01-01

    Measurements of the positron lifetime and the Doppler broadening of the annihilation γ line were performed on sintered YBa 2 Cu 3 O 7-δ specimens between ambient temperature and 1140 K at oxygen partial pressures, p O2 , between 10 2 and 10 5 Pa in order to study the atomic processes of changes of the oxygen content in thermal equilibrium. Above 680 K the positron lifetime increases with increasing temperature and decreasing oxygen partial pressure. It is found that the normalized positron annihilation rate λ 1 * depends exclusively on the oxygen deficiency δ and decreases linearly with increasing δ. Our results demonstrate that the positrons are annihilated predominantly on the sites of the Cu(1)-O(1) chains where the oxygen atoms are removed (oxygen-deficient sites), as suggested by theoretical studies. A simple atomistic model of oxygen exchange is confirmed by the experimentally observed variation of the positron annihilation rate with (p O2 ) -0.27

  18. Oxygen desorption from YBa2Cu3O(7-x) and Bi2CaSr2Cu2O(8 + delta) superconductors

    Science.gov (United States)

    Mesarwi, A.; Levenson, L. L.; Ignatiev, A.

    1991-01-01

    Oxygen desorption experiments from YBa2Cu3O(7-x) (YBCO) and Bi2CaSr2Cu2O(8 + delta) (BSCCO) superconductors were carried out using a quadrupole mass spectrometer for monitoring the desorbing species and X-ray photoemission spectroscopy for surface characterization. Molecular oxygen was found to desorb from both superconductors following photoirradiation with ultraviolet/optical radiation and subsequent heating at over 150 C. Both YBCO and BSCCO were found to have similar oxygen desorption rates and similar activation energies. The desorption data as well as the X-ray photoemission data indicate that the oxygen desorption is not intrinsic to the superconductors but rather due to molecular oxygen entrapped in the material.

  19. Inducing self-assembly of Y2BaCuO5 nanoparticles via Ca-doping for improved pinning in YBa2Cu3O7-x

    International Nuclear Information System (INIS)

    Barnes, P.N.; Haugan, T.J.; Baca, F.J.; Varanasi, C.V.; Wheeler, R.; Meisenkothen, F.; Sathiraju, S.

    2009-01-01

    Different mechanisms may exists as a means to provide additional or specialized enhancement of existing nanoparticulate pinning in YBa 2 Cu 3 O 7-x (YBCO) thin films. In the particular case of Y 2 BaCuO 5 (Y211) nanoparticles, Ca-doping of these nanoparticles via addition to the Y211 target material provides an additional increase to the J c (H). YBCO + Y211 samples were created by pulsed laser deposition with alternating targets of YBCO with Y211 and Y211 doped with Ca. Initial indications suggest that this improvement in pinning results from some scattered short-ranged self-assembly of the nanoparticles into short nanocolumns.

  20. 2D-3D crossover effects on the vortex-glass phase transition in thin YBa2Cu3O7-δ films

    International Nuclear Information System (INIS)

    Woeltgens, P.J.M.; Dekker, C.; Koch, R.H.; Hussey, B.W.; Gupta, A.

    1994-01-01

    Nonlinear current-voltage characteristics have been measured for ultrathin (16-400 A) YBa 2 Cu 3 O 7-δ films in high magnetic fields. A scaling analysis of these data reveals deviations from the universal vortex-glass critical scaling behavior observed for thick films. This is argued to be a dimensionality effect: At large currents, one probes length scales smaller than the film thickness, i.e., the three-dimensional (3d) vortex-glass behavior, whereas at low currents the vortex excitations involve typical length scales which exceed the film thickness, hence the 2d behavior is exhibited. Further evidence for this picture is found from the 3d vortex-glass correlation length, which appears to be cut off by the film thickness. (orig.)

  1. Mapping the magnetic field generated by a supercurrent in a ring of YBa2Cu3O7−δ

    International Nuclear Information System (INIS)

    Sulca, P D; Gómez, R W

    2017-01-01

    We design and construct a device to map the magnetic field generated by a supercurrent in a rectangular cross section ring of YBa 2 Cu 3 O 7−δ . For the measurements of the magnetic field, we develop a Gaussmeter based on a commercial Hall effect sensor coupled to an Arduino microprocessor. Our results show an asymmetric distribution of the magnetic field intensity measured at a certain distance along a plane parallel to the ring surface. The behavior of the magnetic field intensity with distance along the ring axis is closely related to what is expected for a toroid. Using the Biot–Savart law and the measured magnetic field values, the induced supercurrent is determined. (paper)

  2. Scanning/friction force microscopy study of YBa2Cu3O7-δ single crystals grown in BaZrO3 crucibles

    International Nuclear Information System (INIS)

    Lang, H.P.; Jess, P.; Hubler, U.

    1996-01-01

    Very pure YBa 2 Cu 3 O 7-δ (YBCO) single crystals grown in BaZrO 3 crucibles are studied in the as-grown and the oxidized state by scanning force (SFM), friction force (FFM) and scanning tunneling microscopies (STM). The images show clean terraces with step-heights of one unit cell along YBCO(001), i.e. 1.2 nm. Only close to step edges is material contrast observed by FFM indicating traces of flux. Some crystal surfaces exhibit over-layer features, such as star-like, ribbon-like and checkerboard-like structures, which exhibit friction contrast implying the presence of different materials on the surface. Tunneling spectroscopy at 4-7 K in high vacuum reveals a superconducting energy gap of 2Δ ∼ 26 meV

  3. Is LaAlO3 a viable substrate for the deposition of high quality thin films of YBa2Cu3O7-δ?

    International Nuclear Information System (INIS)

    Koren, Gad; Polturak, Emil

    2002-01-01

    A systematic study of the surface morphology of epitaxial thin films of YBa 2 Cu 3 O 7-δ on (100) LaAlO 3 wafers is reported. The films were prepared by high pressure dc sputtering or laser ablation deposition, on wafers of 0.5-2.8 mm thickness and 2 or 3 inch diameter. Optical and atomic force microscopy (AFM) were used to characterize the surfaces, while transport was used to verify the high quality of the films. For films prepared under the same conditions, we found a systematic increase in size and number of extended defects in the films with wafer thickness. In some cases, a clear correlation was observed between the defect structure and the twin boundaries of the LaAlO 3 substrate. We specify the conditions for minimizing these defects. (author)

  4. Influence of vortex-vortex interaction on critical currents across low-angle grain boundaries in YBa2Cu3O7-δ thin films

    Science.gov (United States)

    Albrecht, J.; Leonhardt, S.; Kronmüller, H.

    2001-01-01

    Low-angle grain boundaries with misorientation angles θ<5° in optimally doped thin films of YBa2Cu3O7-δ are investigated by magneto-optical imaging. By using a numerical inversion scheme of Biot-Savart's law, the critical current density across the grain boundary can be determined with a spatial resolution of about 5μm. Detailed investigation of the spatially resolved flux density and current density data shows that the current density across the boundary varies with varying local flux density. Combining the corresponding flux and current pattern, it is found that there exists a universal dependency of the grain boundary current on the local flux density. Considering the magnetic vortex-vortex interaction in and in the vicinity of the grain boundary, a model is developed that is able to describe the experimental data.

  5. Novel method for fabrication of integrated resistors on bilayer Ag/YBa2Cu3O7 films using Ni implantation

    International Nuclear Information System (INIS)

    LaGraff, J.R.; Chan, H.; Murduck, J.M.; Hong, S.H.; Ma, Q.Y.

    1997-01-01

    A novel ion implantation method is described for fabricating low inductance integrated resistors on Ag/YBa 2 Cu 3 O 7 (YBCO) bilayer thin films. Parallel high and low value resistors were simultaneously formed by patterning bilayer films into 10-μm-wide lines, then masking and implanting with Ni to selectively inhibit superconductivity in YBCO. Low value resistors (<1Ω/sq) were formed at 77 K as the supercurrent bypassed the Ni-doped nonsuperconducting YBCO and was shunted through the overlying low resistivity Ag metal. High value resistors (20 - 140 Ω/sq) were formed by removing Ag from above the implanted YBCO forcing the current through the implanted YBCO region. The sheet resistance of both types of resistors was found to increase systematically with increasing Ni implant energy. copyright 1997 American Institute of Physics

  6. Comparative study of electronic structure and charge transport in isostructural cuprates YBa2Cu3O7 and PrBa2Cu3O7

    International Nuclear Information System (INIS)

    Kormilets, V.I.

    1997-01-01

    The self-consistent calculations of electronic structure and charge distribution in YBa 2 Cu 3 O 7 and PrBa 2 Cu 3 O 7 crystals were performed by the method of linear muffin-tin orbitals with full potentials (FP-LMTO). It is revealed that the substitution of Pr for Y results in the charge transfer from a CuO chain to a CuO 2 plane. In its turn, this results in partial innihilation of holes responsible for superconductivity. The effect is analogous to that arisen from the removal of oxygen atoms from CuO chains. It is shown that the degree of covalence of 1-2-3 compounds being considered constitutes and essential value and decreases with pr substitution for Y

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

    DEFF Research Database (Denmark)

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

    1993-01-01

    Experimental results on some radio-frequency superconducting quantum interference device (rf-SQUID) signal properties are presented. The quantum interferometer was made of ceramic YBa2Cu3O7−x and was due to a low critical current operated in the inductance or nonhysteretic mode. With bias current...... as reference, amplitude variation, and phase shift of the voltage over the tank circuit coupled to the SQUID were measured simultaneously. It is shown that there is qualitative agreement between calculations based on the resistivity shunted junction model and the data. Moreover, using phase detection, signal...... instabilities predicted for the rf-SQUID inductance mode were observed. These signal instabilities may be exploited to enhance the transfer coefficient for measured flux-to-output signal. Journal of Applied Physics is copyrighted by The American Institute of Physics....

  8. Antiferromagnetism at the YBa2Cu3O7/La2/3Ca1/3MnO3 interface

    International Nuclear Information System (INIS)

    Haberkorn, N.; Guimpel, J.; Sirena, M.; Steren, L.B.; Saldarriaga, W.; Baca, E.; Gomez, M.E.

    2004-01-01

    The magnetic properties of a series of YBa 2 Cu 3 O 7-x /La 2/3 Ca 1/3 MnO 3 (YBCO/LC 1/3 MO) superlattices grown by dc sputtering at high oxygen pressures (3.5 mbar) show the expected ferromagnetic behavior. However, field-cooled hysteresis loops at a low temperatures show the unexpected existence of exchange bias effect associated with the existence of ferromagnetic/antiferromagnetic (AF) interfaces. The blocking temperature (T B ) is found to be thickness dependent and the exchange bias field (H EB ) is found to be inversely proportional to the ferromagnetic layer thickness, as expected. The presence of an AF material is probably associated with interface disorder and Mn valence shift toward Mn 4+

  9. The effect of CuO chains on the local density of states in the vortex phase of YBa2Cu3O7

    International Nuclear Information System (INIS)

    Atkinson, W A

    2009-01-01

    We examine the effects of the CuO chains on the density of states in the vortex phase in YBa 2 Cu 3 O 7 , via a calculation based on the tight-binding proximity model. In this model, chain superconductivity results from single-electron hopping between the intrinsically normal chains and intrinsically superconducting CuO 2 planes. The calculations are based on self-consistent solutions of the Bogolyubov-de Gennes equations for a bilayer consisting of a single CuO 2 layer and a single CuO chain layer. We find that, in addition to the dispersing resonances found in single-layer models, there are a second set of dispersing resonances, associated with the induced gap in the chain layer. These new resonances are highly anisotropic and distort the vortex core shape.

  10. Exponential H and T decay of the critical current density in YBa2Cu3O7√/sub δ/ single crystals

    International Nuclear Information System (INIS)

    Senoussi, S.; Oussena, M.; Collin, G.; Campbell, I.A.

    1988-01-01

    We report magnetic measurements on single crystals of YBa 2 Cu 3 O 7 √/sub δ/. The magnetic critical current density in the Cu-O basal planes (1.5 x 10 6 Acm 2 at 4.2 K) decreases exponentially with temperature as well as with field for Tapprox. >50 K. This is ascribed to current tunneling through micro- Josephson-junctions. The behavior is radically different from that associated with macrojunctions typical of ''granular'' samples. It is argued that the anisotropy and the T-H anomalous behavior of J/sub c/ are connected with the T dependence and the anisotropy of both the coherence length and the electron mean free path

  11. Crystal growth of YBa2Cu3O(7-x) and reaction of gold crucible with Ba-Cu-rich flux

    Science.gov (United States)

    Tao, Y. K.; Chen, H. C.; Martini, L.; Bechtold, J.; Huang, Z. J.; Hor, P. H.

    1991-01-01

    YBa2Cu3O(7-x) crystals are grown in a gold crucible by a self-flux method. The flux moves along the gold surface due to surface wetting and leaves Y123 crystals behind. The obtained crystals are clean and have a size up to two millimeters and a Tc is greater than 90 K. In an effort to recycle the used crucibles, it is found that the used gold is contaminated by copper. A CuO thin film is easily formed on the surface of the crucible that is made of the used gold. This film provides good surface wetting and a buffer layer, which reduces the reaction between gold and the Y-Ba-Cu-oxide melt.

  12. Generic superconducting phase behavior in high-Tc cuprates: Tc variation with hole concentration in YBa2Cu3O7

    International Nuclear Information System (INIS)

    Tallon, J.L.; Bernhard, C.; Shaked, H.; Hitterman, R.L.; Jorgensen, J.D.

    1995-01-01

    A direct determination of the relationship between T c and hole concentration p for Y 1-x Ca x Ba 2 Cu 3 O 7-δ is obtained by investigating the properties of the fully oxygen-deficient (δ∼1.0) compound for which p=x/2. Measurements of T c , the thermoelectric power S, and bond-valence sums calculated from neutron-diffraction refinements for various values of x and δ allow the full determination of the relations p=p(δ), T c =T c (p), and S=S(T,p) confirming that YBa 2 Cu 3 O 7-δ satisfies the same universal relations in these quantities as the other high-T c superconducting cuprates

  13. Enhanced flux pinning properties in superconducting YBa2Cu3O7−z films by a novel chemical doping approach

    International Nuclear Information System (INIS)

    Wang, W.T.; Pu, M.H.; Lei, M.; Zhang, H.; Wang, Z.; Zhang, H.; Cheng, C.H.; Zhao, Y.

    2013-01-01

    Highlights: • Pure and Co-doped YBCO films were prepared by newly-developed chemical method. • The doped films have much denser and smoother surface microstructures. • Significantly enhanced fux-pinning properties have been obtained for dilute Co-doped flm. -- Abstract: Pure and cobalt-doped superconducting YBa 2 Cu 3 O 7−z (YBCO) films were prepared on (0 0 l) LaAlO 3 substrate by a newly developed polymer-assisted metal organic deposition method. The cobalt-doped YBCO films display much denser and smoother surface microstructures and the superconducting transition temperature T c spans a small range of 1.7 K with the doping levels. Significantly enhanced flux-pinning properties have been obtained for dilute cobalt-doped film. This may be attributed to the good grain connections and the effective flux pinning centers introduced by cobalt doping

  14. Élaboration et performances de matériaux supraconducteurs {YBa_2Cu_3O_7} massifs texturés de taille croissante

    Science.gov (United States)

    Chaud, X.; Gautier-Picard, P.; Beaugnon, E.; Porcar, L.; Bourgault, D.; Tournier, R.; Erraud, A.; Tixador, P.

    1998-03-01

    Industrial applications of the bulk superconducting YBa_2Cu_3O_7 material imply to control the growth of large oriented monodomains in samples of big size (several centimeters). The laboratory EPM-Matformag is committed to produce such materials according to three different methods (zone melting, solidification controlled by a magnetic field, crystal growth from a seed). The results obtained show that it is possible by such methods to elaborate a material with high performances at the centimeter scale and to produce it in series. The availability of such materials allows the measure of physical properties on a large scale and the testing of prototypes for cryo-electrotechnical applications (magnetic bearing, flywheel, coupling device, current lead...). Les applications industrielles des matériaux supraconducteurs massifs YBa_2Cu_3O_7 impliquent de contrôler la croissance de larges monodomaines orientés dans des échantillons de grande taille (plusieurs centimètres). Le laboratoire EPM-Matformag s'est appliqué à produire de tels matériaux selon trois techniques différentes (fusion de zone, solidification contrôlée sous champ magnétique, croissance cristalline à partir d'un germe). Les résultats obtenus montrent qu'il est possible par de telles techniques d'obtenir un matériau performant à l'échelle des centimètres et de le produire en série. La disponibilité de tels matériaux permet de mesurer des propriétés physiques à grande échelle et de tester des prototypes d'applications cryo-électrotechniques (palier magnétique, volant d'inertie, coupleur, amenée de courant, limiteur de courant...).

  15. Estudio preliminar de la creación de una “zona caliente” en YBa2Cu3O7-δ utilizando una corriente continua

    Directory of Open Access Journals (Sweden)

    Evetts, J. E.

    1999-12-01

    Full Text Available This work presents a study of the processes that give rise to the Direct Current Zoning effect. This effect consists in the formation of a hot zone in a superconducting rod when a potential difference is applied to it. The superconducting material used in this case was YBa2Cu3O7-δ. The formation and movement of the zone in the bar can be explained studying the balance between the ionic fluxes created due to the potential difference and to the temperature distribution along the bar. This paper presents the theoretical results obtained using a computer model developed that takes into account the processes of electromigration and ionic diffusion that give rise to the Direct Current Zoning effect.Este trabajo presenta un estudio de los procesos que dan lugar al fenómeno en el que un “punto” o zona caliente se forma al aplicar una diferencia de potencial a los extremos de una barra de óxido superconductor. El material superconductor utilizado en este caso es YBa2Cu3O7-δ. El equilibrio entre los flujos iónicos debidos a la diferencia de potencial y a la distribución de temperatura se han utilizado para explicar la formación y el movimiento de la zona a lo largo de la muestra. Este artículo presenta los resultados teóricos obtenidos utilizando un modelo que tiene en cuenta los procesos de electromigración y difusión iónica que dan lugar a este fenómeno.

  16. Melt-textured growth of polycrystalline YBa2Cu3O7√/sub δ/ with high transport J/sub c/ at 77 K

    International Nuclear Information System (INIS)

    Jin, S.; Tiefel, T.H.; Sherwood, R.C.; van Dover, R.B.; Davis, M.E.; Kammlott, G.W.; Fastnacht, R.A.

    1988-01-01

    The progress toward major applications of YBa 2 Cu 3 O 7 √/sub δ/-type high-T/sub c/ superconductors has been hindered by low critical current densities (J/sub c/) and their significant deterioration in weak magnetic fields. The present work demonstrates that these problems can successfully be overcome through proper microstructural control using molten oxide processing. Melt-textured growth of YBa 2 Cu 3 O 7 √/sub δ/ from a supercooled melt created an essentially 100% dense structure consisting of locally aligned, long, needle-shaped grains (typically 40--600 μm in length). The needles appear to have their long axes parallel to the conduction plane (basal plane) of the orthorhombic structure, with a low-angle orientation change between adjacent grains. This new microstructure, which completely replaces the previous granular and random structure of the sintered precursor, exhibits a dramatically higher transport J/sub c/ (7400 Acm 2 at 77 K) than the typical sintered materials (J/sub c/ = 150--600 Acm 2 ). Even more significant is the much reduced field dependence of J/sub c/(≅1000 Acm 2 at H = 1 T as compared to ≅1 Acm 2 in the sintered structure), indicating that the coupling between grains is much stronger in the new structure. The mechanism responsible for the suppressed weak-link behavior in the melt-textured material is inferred to be the combined effects of the densification, alignment of crystals, and formation of cleaner grain boundaries

  17. Flux pinning enhancements in YBa2Cu3O7-8 superconductors through phase separated, self-assembled LaMnO3-MgO nanocomposite films.

    Energy Technology Data Exchange (ETDEWEB)

    Polat, Ozgur [ORNL; Aytug, Tolga [ORNL; Paranthaman, Mariappan Parans [ORNL; Leonard, Keith J [ORNL; Pennycook, Stephen J [ORNL; Kim, Kyunghoon [ORNL; Cook, Sylvester W [ORNL; Thompson, James R [ORNL; Christen, David K [ORNL; Goyal, Amit [ORNL; Selvamanickam, V. [SuperPower Incorporated, Schenectady, New York; Lupini, Andrew R [ORNL; Meyer, Hendrik [ORNL; Qiu, Xiaofeng [ORNL; Xiong, X. [SuperPower Incorporated, Schenectady, New York

    2011-01-01

    Technological applications of high temperature superconductors (HTS) require high critical current density, Jc, under operation at high magnetic field strengths. This requires effective flux pinning by introducing artificial defects through creative processing. In this work, we generated correlated disorder for strong vortex pinning in the YBa2Cu3O7- (YBCO) films by replacing the standard LaMnO3 (LMO) cap buffer layers in ion beam assisted deposited MgO templates with LMO:MgO composite films. Such films revealed formation of two phase-separated, but at the same time vertically aligned, self-assembled composite nanostructures that extend throughout the entire thickness of the film. Measurements of magnetic-field orientation-dependent Jc of YBCO coatings deposited on these nanostructured cap layers showed correlated c-axis pinning and improved in-field Jc performance compared to those of YBCO films deposited on standard LMO buffers. The present results demonstrate feasibility of novel and potentially practical approaches in the pursuit of more efficient, economical, and high performance superconducting devices.

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

    Energy Technology Data Exchange (ETDEWEB)

    Foltyn, Stephen R [Los Alamos National Laboratory; Wang, Haiyan [Los Alamos National Laboratory; Civale, Leonardo [Los Alamos National Laboratory; Maiorov, Boris A [Los Alamos National Laboratory; Jia, Quanxi [Los Alamos National Laboratory

    2009-01-01

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

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

    DEFF Research Database (Denmark)

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

    1991-01-01

    Interdiffusion studies on high-T(c) superconducting YBa2Cu3O7-delta thin films with thickness in the range of 2000-3000 angstrom, on a Si(111) substrate with a buffer layer have been performed. The buffer layer consists of a 400 angstrom thick epitaxial NiSi2 layer covered with 1200 angstrom...... of polycrystalline ZrO2. YBa2Cu3O7-delta films were prepared using laser ablation. The YBa2Cu3O7-delta films on the Si/NiSi2/ZrO2 substrates are of good quality; their critical temperatures T(c,zero) and T(c,onset) have typical values of 85 and 89 K, respectively. The critical current density j(c) at 77 K equaled 4...... x 10(4) A/cm2. With X-ray analysis (XRD), only c-axis orientation has been observed. The interdiffusion studies, using Rutherford backscattering spectrometry (RBS) and scanning Auger microscopy (SAM) show that the ZrO2 buffer layer prevents severe Si diffusion to the YBa2Cu3O7-delta layer, the Si...

  20. Granularity effect on microwave surface resistance in high-Tc YBa2Cu3O7-x bulk and thin film superconductor

    International Nuclear Information System (INIS)

    Swarup, Ram; Gupta, A.K.

    2001-01-01

    We report the effect of variation of Josephson coupling strength in YBa 2 Cu 3 O 7-x (YBCO) superconductor due to grain enlargement, grain orientation and magnetic field on microwave surface resistance (R s ). The coupling strength in the bulk samples has been increased by increasing the sample density from 4.4 to 5.3 g/cm 3 , whereas in thin films, the same could be increased by increasing the c-axis orientation of the grains. The value of R s (10 GHz, 65 K) in bulk samples has been found to decrease from 52 to 4 mΩ with the increase of the coupling strength from 0.06 to 0.43 and in thin films from 930 to 600 μΩ with increase of the coupling strength from 0.92 to 2.43. The effect of grain decoupling on microwave surface resistance was studied under dc and microwave magnetic fields. The surface resistance increases gradually with the application of dc and microwave magnetic fields due to grain decoupling and finally gets saturated beyond a certain critical field. (author)

  1. In-situ laser processing and microstructural characteristics of YBa2Cu3O7-δ thin films on Si with TiN buffer layer

    International Nuclear Information System (INIS)

    Tiwari, P.; Zheleva, T.; Narayan, J.

    1993-01-01

    The authors have prepared high-quality superconducting YBa 2 Cu 3 O 7 -δ (YBCO) thin films on Si(100) with TiN as a buffer layer using in-situ multitarget deposition system. Both TiN and YBCO thin films were deposited sequentially by KrF excimer laser ( | = 248 nm ) at substrate temperature of 650 C . Thin films were characterized using X-ray diffraction (XRD), four-point-probe ac resistivity, scanning electron microscopy (S E M), transmission electron microscopy (TEM), and Rutherford backscattering (RBS). The TiN buffer layer was epitaxial and the epitaxial relationship was found to be cube on cube with TiN parallel Si. YBCO thin films on Si with TiN buffer layer showed the transition temperature of 90-92K with T co (zero resistance temperature) of 84K. The authors have found that the quality of the buffer layer is very important in determining the superconducting transition temperature of the thin film. The effects of processing parameters and the correlation of microstructural features with superconducting properties are discussed in detail

  2. UHV-cluster-tool for fabrication of thin film structures and transport- and noise properties of YBa2Cu3O7-δ grain boundary-SQUIDs

    International Nuclear Information System (INIS)

    Back, Christoph

    2007-01-01

    A UHV-thin-film-deposition system for the fabrication of thin film structures of metals and oxides was designed and optimized. For oxide materials, Pulsed Laser Deposition (PLD) was implemented. Epitaxial thin film growth can be analyzed during the PLD process by high-pressure RHEED (Reflection High-Energy Electron Diffraction). Furthermore layer-by-layer growth can be triggered by Pulsed Laser Intervall Deposition (PLiD). Heteroepitaxial multilayers can be fabricated automatically. Metal thin films can be grown by planar magnetron sputtering and by electron beam evaporation. Furthermore the system contains an rf-plasma source for surface cleaning and Ion Beam Etching (IBE). The three different deposition techniques are located in separate vacuum chambers which are connected by a central handling chamber allowing to combine all these processes in-situ. Furthermore superconducting quantum interference devices (SQUIDs) were fabricated out of epitaxially grown high-temperature superconducting YBa 2 Cu 3 O 7 -films on bicrystals. The SQUIDs were structured using a combined process of ion milling and chemical wet etching. By this combined etching process, edge signals that appear during imaging of flux quanta by low temperature scanning microscopy can be avoided. The transport- and noise properties of the SQUIDs were investigated. (orig.)

  3. Microstructural and compositional analysis of YBa2Cu3O7-δ films grown by MOCVD before and after GCIB smoothing

    International Nuclear Information System (INIS)

    Hatzistergos, M.S.; Efstathiadis, H.; Reeves, J.L.; Selvamanickam, V.; Allen, L.P.; Lifshin, E.; Haldar, P.

    2004-01-01

    The microstructural and compositional evolution of thick (>1 μm) high temperature superconducting YBa 2 Cu 3 O 7-x (YBCO) films grown on single crystal SrTiO 3 substrates by the metal organic chemical vapor deposition (MOCVD) process was investigated by focused ion beam microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, and atomic force microscopy. This study showed that as the MOCVD YBCO film thickness increased above 0.5 μm, defects such as second phase particles, pores, and misaligned grains preferentially nucleated and grew at the YBCO surface. A portion of this defective top layer was eliminated from all the samples using a gas cluster ion beam (GCIB) process that first removed material with a focused argon cluster beam. Next, an oxygen cluster beam was used to smooth the surface and re-oxygenate the YBCO. Comparing the critical current (I c ) measured before and after GCIB processing showed that the I c remained the same, and even improved, when part of the defective top layer was removed. This microstructural and electromagnetic 'dead layer' is believed to be responsible for the overall I c decrease of MOCVD YBCO films thicker than 0.5 μm

  4. High-transport current density up to 30 T in bulk YBa2Cu3O7 and the critical angle effect

    International Nuclear Information System (INIS)

    Ekin, J.W.; Salama, K.; Selvamanickam, V.

    1991-01-01

    Measurements of the dc transport critical current of oriented-grained YBa 2 Cu 3 O 7 have been made using high quality Ag contacts and a high-current sample mount. The critical- current density J c at 77 K for mutually perpendicular current and magnetic field B in the a,b plane is 8 kA/cm 2 at 8 T, decreasing gradually to 3.7 kA/cm 2 at 20 T, and remaining over 1 kA/cm 2 out to 30 T. High magnetic field measurements of J c as a function of the angle θ of B with respect to the c axis are also reported. In contrast to earlier results at lower fields ( c vs θ curve with a head-and-shoulders shape, consisting of a sharp peak (''head'') 2 planes, and a wide (30 degree at 9 T, for example) shoulder region on either side of B perpendicular c, where the transport J c remains high and constant. Beyond the shoulder region, however, the transport J c decreases sharply, giving rise to the concept of a critical field angle for application design, defined by the minima in d 2 J c /dθ 2 at the edge of the shoulders

  5. Superconducting properties of YBa2Cu3O7−δ films deposited on commercial tape substrates, decorated with Pd or Ta nano-islands

    International Nuclear Information System (INIS)

    Polat, Ö; Thompson, J R; Leonard, K J; Wee, S H; Christen, D K; Ertuğrul, M; Sinclair, J W; Zuev, Y L; Paranthaman, M P; Aytuğ, T; Xiong, X; Selvamanickam, V

    2012-01-01

    To obtain an engineered surface for deposition of high-T c superconductors, nanoscale modulations of the surface of the underlying LaMnO 3 (LMO) cap layer is a potential source for generating microstructural defects in YBa 2 Cu 3 O 7−δ (YBCO) films. These defects may improve the flux pinning and consequently increase the critical current density, J c . To provide such nanoscale modulation via a practical and scalable process, palladium (Pd) or tantalum (Ta) nano-islands were deposited using dc-magnetron sputtering on the surface of the cap layer of commercial metal tape templates for second-generation wires. The size and density of these nano-islands can be controlled by changing sputtering conditions such as the power and deposition time. Compared to the reference sample grown on an untreated LMO cap layer, the YBCO films grown on the LMO cap layers with Pd or Ta nano-islands exhibited improved in-field J c performance. Atomic force microscopy and transmission electron microscopy were used to assess the evolving size and density of the nano-islands. (paper)

  6. Microstructure and transport current characterization of YBa2Cu3O7-x thick films prepared by modified solid-liquid melt growth and powder melt process routes

    International Nuclear Information System (INIS)

    Langhorn, J.; McGinn, P.J.

    1999-01-01

    From the characterization of superconducting YBa 2 Cu 3 O 7-x (YBCO) thick films processed by melt texturing on yttria-stabilized zirconia substrates from YBCO precursors it is clear that the properties are highly dependent on the precursor powder. Increased YBCO grain sizes have been induced in thick films processed from by modified solid-liquid melt growth (SLMG) and powder melt (PMP) processes with respect to those processed from pre-reacted YBCO materials. The SLMG and PMP routes utilize precursors consisting of BaCuO 2 -CuO flux material mixed with Y 2 O 3 and Y 2 BaCuO 5 respectively. Cross-sectional analysis of films textured by these routes shows a decreased Y 2 BaCuO 5 size and an increased homogeneity within the matrix with respect to films processed from YBCO powder. Such microstructural improvements lead to an improvement of both the flux pinning and current-carrying characteristics of the processed YBCO films. (author)

  7. High-temperature change of the creep rate in YBa2Cu3O7-δ films with different pinning landscapes

    Science.gov (United States)

    Haberkorn, N.; Miura, M.; Baca, J.; Maiorov, B.; Usov, I.; Dowden, P.; Foltyn, S. R.; Holesinger, T. G.; Willis, J. O.; Marken, K. R.; Izumi, T.; Shiohara, Y.; Civale, L.

    2012-05-01

    Magnetic relaxation measurements in YBa2Cu3O7-δ (YBCO) films at intermediate and high temperatures show that the collective vortex creep based on the elastic motion of the vortex lattice has a crossover to fast creep that significantly reduces the superconducting critical current density (Jc). This crossover occurs at temperatures much lower than the irreversibility field line. We study the influence of different kinds of crystalline defects, such as nanorods, twin boundaries, and nanoparticles, on the high-temperature vortex phase diagram of YBCO films. We found that the magnetization relaxation data is a fundamental tool to understand the pinning at high temperatures. The results indicate that high Jc values are directly associated with small creep rates. Based on the analysis of the depinning temperature in films with columnar defects, our results indicate that the size of the defects is the relevant parameter that determines thermal depinning at high temperatures. Also, the extension of the collective creep regime depends on the density of the pinning centers.

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

    Science.gov (United States)

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

    2015-12-01

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

  9. Optimization in the preparation of the YBa2Cu3O7-δ compound using BaCO3 and BaO2 reagents

    International Nuclear Information System (INIS)

    Bustamante D, A.; Flores S, J.

    2004-01-01

    The traditional superconductor YBa 2 Cu 3 O 7-δ (Y123) has an orthorhombic crystalline structure with spatial group Pmmm and its critical temperature is 90K. The literature reports the use of reagent BaCO 3 for the preparation by the solid state reaction which requires one calcination and two thermal treatments in oxygen flow at 950 o C. In this work we report the comparison in the preparation of Y123 using the BaO 2 reagent as another possibility for preparation; in this case we have used only two thermal treatments in oxygen flow at 950 o C; therefore reducing the costs in preparation. The powder XRD pattern of samples prepared with BaO 2 confirm a well crystallized phase an the diffraction lines of the main phase can be indexed with an orthorhombic unit cell. The ac susceptibility measurement in the range 5-100 K using a Quantum Design (SQUID) magnetometer for two samples confirms the superconductor behavior with critical temperature Tc ≅ 91 K. The critical temperatures for these systems were found taken account the derivatives of the susceptibility curves. Scanning Electron Microscopy (SEM) confirms the good behavior of the grains corresponding to both methods. (orig.)

  10. pairing symmetry and electrodynamics of superconducting YBa2Cu3O7-δ, Nd1.85Ce0.15CuO4, and Nb

    International Nuclear Information System (INIS)

    Wu, Dong-Ho; Mao, Jian; Anlage, S.M.

    1995-01-01

    We experimentally investigate the pairing symmetry and electrodynamics of YBa 2 Cu 3 O 7-δ (YBCO), Nd 1.85 Ce 0.15 CuO 4 (NCCO), and Nb by examining the temperature dependence of the penetration depth λ (T) and surface resistance R s (T) in a comparative manner. Using the measured λ(T) and R s (T), we extract the complex conductivity σ=σ 1 -iσ 2 for each sample, and the quasiparticle scattering time τ(T) for the ab-plane and c-axis in YBCO. While NCCO and Nb show a strong resemblance in their electrodynamic properties, the electrodynamic properties of YBCO are very distinctive from the others. The results suggest that NCOO may have a BCS s-wave-like pairing state, while YBCO possibly has an unconventional pairing state. We compare the results on YBCO with the d-wave pairing scenario, as well as with other possible theoretical models

  11. Oxygen potentials and phase equilibria of the quaternary Y-Ba-Cu-O system in the region involving the YBa2Cu3O7-x phase

    International Nuclear Information System (INIS)

    Fitzner, K.; Musbah, O.; Hsieh Kerchang; Zhang Minxian; Chang, Y.A.

    1993-01-01

    The equilibrium oxygen potentials of four-phase equilibria (counting only the condensed phases) in the CuO-Cu 2 O-BaCuO 2 -Y 2 BaCuO 5 (211)-YBa 2 Cu 3 O 7-x (123) phase region were determined using the following solid-oxide electrolyte e.m.f. cell: Pt10Rh, air (psub(O 2 )=0.21 atm) vertical stroke ZrO 2 +Y 2 O 3 vertical stroke mixtures of oxides, Pt. The oxide mixtures whose oxygen potentials were measured were CuO-Cu 2 O-211-123, CuO-Cu 2 O-BaCuO 2 -123, Cu 2 O-BaCuO 2 -211-123 and CuO-BaCuO 2 -211-123. The phase in some of the mixtures were identified by X-ray diffraction. These data were analyzed and are presented using stability diagrams, i.e., oxygen potential as a function of the reciprocal of the temperature. Extrapolation of these data for the four four-phase equilibra to high temperatures yields a metastable five-phase equilibrium, i.e., 123=CuO+Cu 2 O+BaCuO 2 +211, at ∼1243 K (970 ) and log psub(O 2 ) ∼ -1.21 (psub(O 2 )∼0.062 atm). (orig.)

  12. Characterization and in situ fluorescence diagnostic of the deposition of YBa2Cu3O7-x thin films by pseudo-spark electron beam ablation

    International Nuclear Information System (INIS)

    Jiang, Q.D.; Matacotta, F.C.; Masciarelli, G.; Fuso, F.; Arimondo, E.; Sandrin, G.

    1992-12-01

    The pseudo-spark electron beam ablation (PSA) technique is a comparatively simple and inexpensive method to deposit thin films of oxide materials. The effect of the electron beam power density on the efficiency of the PSA is studied. Results concerning the optimization of the deposition process of high quality superconducting YBa 2 Cu 3 O 7-x thin films on single crystal SrTiO 3 substrates are reported. Correlation between processing parameters and superconducting properties of the thin films are presented: in particular, the effects of the break-down voltage of the pseudo-spark and geometrical arrangement of the target-substrate-beam system on the T c of the resulting films. In situ spectral analysis of the radiative emission from the plasma plume has been performed at different distances from the surface of the target and at different break-down voltages of the pseudo-spark. The role of the oxygen pressure in the PSA process, which could be one order of magnitude less than that for a typical laser ablation system, is discussed. (author). 17 refs, 7 figs, 1 tab

  13. Unusual magneto-transport of YBa2Cu3O7−δ films due to the interplay of anisotropy, random disorder and nanoscale periodic pinning

    International Nuclear Information System (INIS)

    Trastoy, J; Rouco, V; Bernard, R; Briatico, J; Villegas, J E; Ulysse, C; Faini, G; Palau, A; Puig, T; Lesueur, J

    2013-01-01

    We study the general problem of a manifold of interacting elastic lines whose spatial correlations are strongly affected by the competition between random and ordered pinning. This is done through magneto-transport experiments with YBa 2 Cu 3 O 7−δ thin films that contain a periodic vortex pinning array created via masked ion irradiation, in addition to the native random pinning. The strong field-matching effects we observe suggest the prevalence of periodic pinning, and indicate that at the matching field each vortex line is bound to an artificial pinning site. However, the vortex-glass transition dimensionality—quasi-two dimensional instead of the usual three dimensional—evidences reduced vortex-glass correlations along the vortex line. This is also supported by an unusual angular dependence of the magneto-resistance, which greatly differs from that of Bose-glass systems. A quantitative analysis of the angular magneto-resistance allows us to link this behaviour to the enhancement of the system anisotropy, a collateral effect of the ion irradiation. (paper)

  14. A temperature dependent study of the Raman-active phonon modes in Ca and Zn doped YBa2Cu3O7-x

    International Nuclear Information System (INIS)

    Quilty, J. W.; Trodahl, H. J.; Simpson, A.; Flower, N.; Staines, M.; Downes, J.

    1996-01-01

    Full text: The temperature dependent behaviour of the phonon modes in YBa 2 Cu 3 O 7-x (Y-123) are of interest because the strong electron-phonon coupling within these materials yields information about the magnitude of the superconducting gap. The opening of a gap provides a new decay route for phonons, hence phonons near the gap energy show changes in their frequencies and widths as the temperature drops below T c . The magnitude of the superconducting gap may be estimated from these changes. We report our temperature-dependent measurements of the Raman-active phonon modes in ceramic and preferentially oriented polycrystalline samples of Y-123, under a variety of doping regimes. The samples were made underdoped, optimally doped and overdoped by manipulation of the hole concentration on the Cu-O planes, achieved by changing the oxygen stoichiometry, substitution of Zn for Cu, and substitution of Ca for Y. As observed by others, the 340cm -1 phonon, involving vibrations of the oxygen ions on the Cu-O planes, showed the greatest magnitude of change when the samples were cooled below T c , indicating that the superconducting gap energy is close to that of the 340cm -1 phonon

  15. Evidence for Crossed Andreev Reflections in (100)YBa2Cu3O7+δ-SrRuO3 superconductor-ferromagnet bilayers

    International Nuclear Information System (INIS)

    Asulin, I.; Yuli, O.; Millo, O.; Koren, G.

    2005-01-01

    Full Text:Since the ferromagnetic side of a superconductor-ferromagnet junction is spin polarized, Andreev reflections are suppressed. Consequently, the proximity induced superconductor order parameter in the ferromagnet is expected to decay rapidly, on the order of a nm, the typical coherence length in a ferromagnet. Our scanning tunneling spectroscopy measurements on thin epitaxial (100)YBa 2 Cu 3 O 7+ δ-SrRuO 3 (YBaCuO-SrO) bilayers, where SrO is a ferromagnet, indeed show that on most of the junction area the superconductor order parameter vanishes in the SrO layers thicker than 8 nm. However, we find localized regions, arranged along narrow (< 10 nm) stripes, where the order parameter (superconductor-like gap structure) penetrates the ferromagnet over more than 20 nm. This is attributed to 'Crossed Andreev Reflections,' taking place at domain boundaries, where an electron from one magnetic domain is retro reflected as a hole with opposite spin in an adjacent domain. Our observation may account for the (not abundant) cases where a long-range proximity effect was found in superconductor-ferromagnet proximity systems

  16. Microstructural comparison of Yba2Cu3O7-x thin films laser deposited in O2 and O2/Ar ambient

    DEFF Research Database (Denmark)

    Verbist, K.; Kyhle, Anders; Vasiliev, A.L.

    1996-01-01

    The use of a diluted O-2/Ar atmosphere-for laser deposition of YBa2Cu3O7-x thin films results in a strong decrease of the surface outgrowth density as compared to deposition in pure O-2. The smoother films need a longer oxygenation period and show slightly lower critical current densities; though...... still in excess of 10(6) A cm(-2) at 77 K. Electron microscopy revealed that the outgrowths mainly consist of a large copper-oxide grain connected to Y2O3 grains. Y2O3 nano-scale inclusions are present irrespective of the deposition atmosphere, however at remarkably low densities compared to other...... literature data. We find that the twin plane density is lower and the twin structure more homogeneous in the case of films deposited in a mixture of O-2/Ar. This we ascribe to the absence of surface outgrowths which seem to block regular twin structure formation. Possibly the differences in necessary post...

  17. Mechanism of the transition from orthorhombic to tetragonal YBa 2Cu 3O 7- x. Investigation of a reversible topotactic reaction in the electron microscope

    Science.gov (United States)

    Müller, J.-H.; Gruehn, R.

    The phase transition from orthorhombic to tetragonal could be observed (in situ) with High-Resolution Transmission Electron Microscopy (HRTEM). In superconducting samples of YBa 2Cu 3O 7- x ( x=0.09) twinned areas were found which changed from orthorhombic to tetragonal symmetry upon electron irradiation parallel to the long c axis. In opposition to annealing experiments the length of the c-axis remained unchanged. The transition was reversible in the high vacuum of the electron microscope. Therefore we surmise that this reaction has no reductive character (no perceptible loss of oxygen). Within the tetragonal structure one can assume a statistical sharing (“disorder”) of oxygen by the metal atoms. The transition could also be explained by a migration of oxygen to the surface. After finishing the irradiation experiment and waiting for several minutes, the oxygen seems to occupy partially ordered positions resulting again in an orthorhombic symmetry. In some cases we could observed transition states of the structural transformation. A schematic model of the mechanism is depicted.

  18. Ba2NdZrO5.5 as a potential substrate material for YBa2Cu3O7-δ superconducting films

    International Nuclear Information System (INIS)

    Tovar, H.; Ortiz Diaz, O.; Landinez Tellez, D.A.; Roa-Rojas, J.

    2007-01-01

    The new oxide Ba 2 NdZrO 5.5 (BNZO) has been produced by the standard solid state reaction method. X-ray diffraction analysis (XRD) revealed that this synthesized material has an ordered complex cubic perovskite structure characteristic of A 2 BB'O 6 crystalline structure with a lattice parameter of a = 8.40 Aa. It was established through EDX analysis that there is no trace of impurities. Chemical stability of BNZO with YBa 2 Cu 3 O 7-δ (YBCO) has been studied by means of Rietveld analysis of experimental XRD data on several samples of BNZO-YBCO composites. Quantitative analysis of phases on XRD patterns show that all peaks have been indexed for both BNZO and YBCO, and no extra peak is detectable. YBCO and BNZO remain as two different separate phases in the composites with no chemical reaction. Electrical measurements also revealed that superconducting transition temperature of pure YBCO and BNZO-YBCO composites is 90 K. These favorable characteristics of BNZO show that it can be used as a potential substrate material for deposition of YBCO superconducting films. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  19. Motion stability of the magnetic levitation and suspension with YBa2Cu3O7-x high-Tc superconducting bulks and NdFeB magnets

    Science.gov (United States)

    Li, Jipeng; Zheng, Jun; Huang, Huan; Li, Yanxing; Li, Haitao; Deng, Zigang

    2017-10-01

    The flux pinning effect of YBa2Cu3O7-x high temperature superconducting (HTS) bulk can achieve self-stable levitation over a permanent magnet or magnet array. Devices based on this phenomenon have been widely developed. However, the self-stable flux pinning effect is not unconditional, under disturbances, for example. To disclose the roots of this amazing self-stable levitation phenomenon in theory, mathematical and mechanical calculations using Lyapunov's stability theorem and the Hurwitz criterion were performed under the conditions of magnetic levitation and suspension of HTS bulk near permanent magnets in Halbach array. It is found that the whole dynamical system, in the case of levitation, has only one equilibrium solution, and the singular point is a stable focus. In the general case of suspension, the system has two singular points: one is a stable focus, and the other is an unstable saddle. With the variation of suspension force, the two first-order singular points mentioned earlier will get closer and closer, and finally degenerate to a high-order singular point, which means the stable region gets smaller and smaller, and finally vanishes. According to the center manifold theorem, the high-order singular point is unstable. With the interaction force varying, the HTS suspension dynamical system undergoes a saddle-node bifurcation. Moreover, a deficient damping can also decrease the stable region. These findings, together with existing experiments, could enlighten the improvement of HTS devices with strong anti-interference ability.

  20. Calorimetric evidence for the occurrence of a first-order transition in the mixed state of untwinned YBa2Cu3O7

    International Nuclear Information System (INIS)

    Schilling, A.; Fisher, R.A.; Phillips, N.E.; Welp, U.; Kwok, W.K.; Crabtree, G.W.

    1997-01-01

    Using high-resolution differential thermal analysis (DTA) the authors have demonstrated directly, for the first time in a thermal experiment, that the vortex lattice of untwinned YBa 2 Cu 3 O 7-δ in the mixed state (for magnetic fields H parallel and perpendicular to the c axis of the crystal) undergoes a first-order phase transition. The phase-transition line H m (T) in the magnetic phase diagram coincides with the vortex-lattice melting line that had been deduced previously from resistivity and magnetization measurements. The value obtained for the latent heat, L ∼ 0.5 k B T per vortex per superconducting layer for H parallel c, is consistent with that inferred from magnetization data using the Clapeyron equation, thus proving thermodynamic consistency. The specific heat of the vortex fluid is larger than that of the vortex solid. This specific-heat difference, ΔC/T, and the latent heat L, are independent of both the speed and the direction (up or down in T or H) of the traversal of the phase boundary H m (T), proving that the transition does not have the characteristics of a glass-like melting transition

  1. Effect of microwave-enhanced superconductivity in YBa2Cu3O7 bi-crystalline grain boundary weak-links

    International Nuclear Information System (INIS)

    Fu, C.M.; Chen, C.M.; Lin, H.C.

    1994-01-01

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

  2. Anharmonic Oxygen Displacements in La2-x (Sr, Ba)xCuO4 Planes and in YBa2Cu3O7 Chains

    International Nuclear Information System (INIS)

    Pickett, W. E.

    1995-01-01

    An earlier calculation of the energy surface for X-point tilts if the CuO6 octahedra in La 2-x (Sr, Ba) x CuO 4 revealed an eight well potential surface. This surface indicated an extremely anharmonic situation and seemed to provide an explanation of a number of observed phenomena in this system, especially the coincidence of a drop in Tc with the occurrence of the low temperature tetragonal phase. We review experimental developments since that time, which indicate new complications. We also reconsider the zone boundary chain-buckling mode of the chain oxygen atoms in YBa 2 Cu 3 O 7 , for which our earlier calculation indicated a very flat (slightly double well) energy surface that would provide very little restoring force to this motion. We have studied the coupling of the chain buckling motion to the carriers by evaluating the shifts of bands near the Fermi energy. These deformation potentials themselves are not large (∼ 0.1-0.2 eV/A) and non-linear coupling is minor out to displacements of 0.25 A. (author)

  3. Structural characterization of epitaxial YBa2Cu3O7 thin films on step-edge substrates by means of high-resolution electron microscopy

    International Nuclear Information System (INIS)

    Jia, C.L.; Kabius, B.; Urban, K.

    1993-01-01

    The microstructure of YBa 2 Cu 3 O 7 films epitaxially grown on step-edge (0 0 1) SrTiO 3 and LaAlO 3 substrates has been characterized by means of high-resolution electron microscopy. The results indicate a relationship between the microstructure of the film across a step and the angle the step makes with the substrate plane. On a steep, high-angle step, the film grows with its c-axis perpendicular to that of the film on substrate surface so that two grain boundaries are formed. In the upper grain boundary, on the average, a (0 1 3) habit plane alternates with a (1 0 3) habit plane. This alternating structure is caused by twinning in the orthorhombic structure. The lower boundaries consist of a chain of (0 1 3)(0 1 3) and (0 1 0)(0 0 1) type segments exhibiting a tendency to tilt the whole habit plane toward the a-b plane of the flank film. Dislocations, stacking faults and misfit strains were also observed in or close to the boundaries. (orig.)

  4. Magnetic pinning-effect in Nd0.7Ca0.3MnO3/YBa2Cu3O7 bilayer

    International Nuclear Information System (INIS)

    Hsu, Daniel; Lin, J.G.; Wu, W.F.

    2007-01-01

    The vortex lines of superconductor can be driven by electrical currents, which are often coupled with a reliable control of flux quanta movement by defects or magnetic domains. In this work, the magnetic pinning-effect in Nd 0.7 Ca 0.3 MnO 3 /YBa 2 Cu 3 O 7 (NCMO/YBCO) bilayers is investigated. It is found that by increasing the field from 0 to 5 Tesla, the critical current I c of pure YBCO film at 50 K is suppressed by three orders of magnitude. However, in the NCMO/YBCO bilayer I c is less sensitive to the field and maintains at the level of 100 mA at high field. This result indicates that the magnetic pinning effect of NCMO is much more efficient than the conventional routes, which maybe related to the fine domain structure of NCMO film. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  5. Unconventional critical state in YBa2Cu3O7-δ thin films with a vortex-pin lattice fabricated by masked He+ ion beam irradiation

    Science.gov (United States)

    Zechner, G.; Mletschnig, K. L.; Lang, W.; Dosmailov, M.; Bodea, M. A.; Pedarnig, J. D.

    2018-04-01

    Thin superconducting YBa2Cu3O7-δ films are patterned with a vortex-pin lattice consisting of columnar defect regions (CDs) with 180 nm diameter and 300 nm spacing. They are fabricated by irradiation with 75 keV He+ ions through a stencil mask. Peaks of the critical current reveal the commensurate trapping of vortices in domains near the edges of the sample. Upon ramping an external magnetic field, the positions of the critical current peaks are shifted from their equilibrium values to lower magnetic fields in virgin and to higher fields in field-saturated down-sweep curves, respectively. Based on previous theoretical predictions, this irreversibility is interpreted as a nonuniform, terrace-like critical state, in which individual domains are occupied by a constant number of vortices per pinning site. The magnetoresistance, probed at low current densities, is hysteretic and angle dependent and exhibits minima that correspond to the peaks of the critical current. The minima’s positions scale with the component of the magnetic field parallel to the axes of the CDs, as long as the tilted vortices can be accommodated within the CDs. This behavior, different from unirradiated films, confirms that the CDs dominate the pinning.

  6. Effect of Annealing to the Formation of The 123 Phase YBa2Cu3O7-x Superconductor Produced by High Energy Milling

    International Nuclear Information System (INIS)

    Didin S Winatapura; Yustinus P, Wisnu A.A; Sukirman, E.

    2008-01-01

    Effect of annealing to the formation of 123 phase YBa 2 Cu 3 O 7-x superconductor produced by high energy milling (HEM) has been investigated. The milling process by using HEM method was performed for 30 hours, and followed by annealing at 500 o C, 600 o C, and 700 o C for 10 hours. The phase quality and quantity inside the specimen was measured by X-rays diffraction technique (XRD), and analyzed using Rietveld method. The microstructure of the specimen was observed with Scanning Electron Microscope (SEM), and electric property of the specimen was measured with four point probe. The result showed that the milling for 30 hours caused the deformation and partial decomposition of 123 phase resulting in another phase. The anneal effect caused the recrystallization process of decomposed 123 phase in such away that reformed 123 phase having finer crystallite size. According to the calculation using the Hall-Williamson's equation, the diameter of the crystallite size, D was obtained of about 496 Armstrong for milled specimen, and D ∼ 1,714 Armstrong for sintered specimen. By decreasing the 123 phase grain size, the intergrain contact surface became larger. It means that the intergrain link of 123 phase became stronger. The critical current (density) of milled specimen was obtained as J c ∼23.74 A.cm -2 , and J c ∼ 3.18 A.cm -2 for sintered specimen. Thus, the transport current that flowed intergrain inside 123 phase increased.(author)

  7. High-field paramagnetic Meissner effect up to 14 T in melt-textured YBa_2Cu_3O_7_–_δ

    International Nuclear Information System (INIS)

    Dias, F.T.; Vieira, V.N.; Wolff-Fabris, F.; Kampert, E.; Gouvêa, C.P.; Campos, A.P.C.; Archanjo, B.S.; Schaf, J.; Obradors, X.; Puig, T.; Roa, J.J.; Sahoo, B.K.

    2016-01-01

    Highlights: • A persistent paramagnetic Meissner effect up to 14 T. • The PME with a slight tendency to saturate in high magnetic fields. • Strong time effects causing a paramagnetic relaxation dependent on the cooling rate. - Abstract: We have performed magnetization experiments in a melt-textured YBa_2Cu_3O_7_-_δ (Y123) sample with Y_2BaCuO_5 (Y211) inclusions, under magnetic fields up to 14 T applied parallel or perpendicular to the ab plane. Magnetic anisotropy and paramagnetic moments were observed in both FC (field-cooling) and FCW (field-cooled warming) procedures and these features correspond to the so-called High-Field Paramagnetic Meissner Effect (HFPME). The HFPME effect increases monotonically as the magnetic field rises and a strong paramagnetic relaxation, toward increasing paramagnetic moment was additionally observed as a function of time. Microscopy analysis revealed a complex and correlated microstructure of the Y211 particles. These correlated defects are well known to cause strong flux pinning. Our results suggest a scenario of strong flux compression within weak or non-superconducting regions of the samples, developed as a consequence of the Meissner effect and assisted by strong flux pinning by the Y211 particles. This scenario is observed up to 14 T and clearly persists beyond.

  8. Atomic and electronic structures of BaHfO3-doped TFA-MOD-derived YBa2Cu3O7−δ thin films

    International Nuclear Information System (INIS)

    Molina-Luna, Leopoldo; Duerrschnabel, Michael; Turner, Stuart; Martinez, Gerardo T; Van Aert, Sandra; Van Tendeloo, Gustaaf; Erbe, Manuela; Holzapfel, Bernhard

    2015-01-01

    Tailoring the properties of oxide-based nanocomposites is of great importance for a wide range of materials relevant for energy technology. YBa 2 Cu 3 O 7−δ (YBCO) superconducting thin films containing nanosized BaHfO 3 (BHO) particles yield a significant improvement of the magnetic flux pinning properties and a reduced anisotropy of the critical current density. These films were prepared by chemical solution deposition (CSD) on (100) SrTiO 3 (STO) substrates yielding critical current densities up to 3.6 MA cm −2 at 77 K and self-field. Transport in-field J c measurements demonstrated a high pinning force maximum of around 6 GN/m 3 for a sample annealed at T = 760 °C that has a doping of 12 mol% of BHO. This sample was investigated by scanning transmission electron microscopy (STEM) in combination with electron energy-loss spectroscopy (EELS) yielding strain and spectral maps. Spherical BHO nanoparticles of 15 nm in size were found in the matrix, whereas the particles at the interface were flat. A 2 nm diffusion layer containing Ti was found at the YBCO (BHO)/STO interface. Local lattice deformation mapping at the atomic scale revealed crystal defects induced by the presence of both sorts of BHO nanoparticles, which can act as pinning centers for magnetic flux lines. Two types of local lattice defects were identified and imaged: (i) misfit edge dislocations and (ii) Ba-Cu-Cu-Ba stacking faults (Y-248 intergrowths). The local electronic structure and charge transfer were probed by high energy resolution monochromated electron energy-loss spectroscopy. This technique made it possible to distinguish superconducting from non-superconducting areas in nanocomposite samples with atomic resolution in real space, allowing the identification of local pinning sites on the order of the coherence length of YBCO (∼1.5 nm) and the determination of 0.25 nm dislocation cores. (paper)

  9. Superconducting properties and microstructure of YBa2Cu3O7-δ/PrBa2Cu3O7-δ superlattices

    International Nuclear Information System (INIS)

    Lowndes, D.H.; Norton, D.P.; Zheng, X.Y.; Zhu, Shen

    1991-10-01

    Epitaxial YBa 2 Cu 3 O 7-δ /PrBa 2 Cu 3 O 7-δ (YBCO/PBCO) superlattices are tools for systematic, fundamental studies of high-temperature superconductivity. The variation of T c in YBCO/PBCO superlattices can be understood as arising from changes in the interlayer phase coupling between YBCO layers that are highly two-dimensional when they are very thin (∼1--2 c-axis unit cells) and completely isolated from each other. Single-cell-thick YBCO layers, containing isolated pairs of CuO 2 planes, are found to be superconducting at T c ∼ 20 K, in a PBCO matrix. The resistance in the superconducting transition region scales with temperature as expected for the (flux flow) resistance produced by thermally generated 2D vortices, or for a 2D array of superconducting weak links. Relative to both thin-film and single-crystal HTSc specimens, the thin superconducting layers in YBCO/PBCO superlattices exhibit a greatly expanded temperature range over which characteristic 2D dissipation can be observed, as a consequence of the enhanced anisotropy and reduced dimensionality of the YBCO layers. Scanning tunneling microscope studies reveal that YBCO films and YBCO/PBCO superlattices grow unit cell-by-unit cell by a terraced-island growth mechanism. On miscut, near-(001) substrates the terraces are epitaxially aligned with the substrate crystal lattice and spiral growth structures (screw dislocation-mediated growth) are not seen. These observations explain the steps or ''kinks'' that are seen in cross-section Z-contrast TEM images of YBCO/PBCO superlattices. The kinks may correspond physically to regions where the supercurrent must tunnel along the c- axis, and thus may be weak-link barriers. 31 refs., 7 figs

  10. Study of the local induction in the superconductor YBa2Cu3O7-δ by Moessbauer spectroscopy using the probe 170Yb3+: methodology and results

    International Nuclear Information System (INIS)

    Vaast-Paci, Ch.

    1997-01-01

    This thesis is concerned with the measurement of the local induction in the anisotropic type II superconductor YBa 2 Cu 3 O 7-δ in presence of an applied field. In this compound, the field penetrates in the form of vortices whose characteristics are governed by both intrinsic (critical fields, anisotropy, penetration lengths,...) and extrinsic parameters (such as pinning centers). We have developed a new microscopic technique to measure the local fields using Moessbauer probes 170 Yb 3+ dilutes for Y 3+ . The measurements are based on the field dependence (size and direction) of the Moessbauer transitions between the electronuclear levels of the probe. These probes are distributed randomly over the sample so the measurements provide both the size and the direction of the internal field distribution over the whole sample. The possible measurement range extends from below 50 Oe to about 4000 Oe, for temperatures up to 60 deg.K. Measurements were made at T4.2 deg. K, for sintered pellets with different oxygen amount and for optimally doped ci-axis oriented single crystals. The penetration length measurements showed that the density of the superconducting condensate increases progressively with carrier doping. Field penetration measurements furnished the microscopic lower penetration field H cl , and enabled us to propose a model describing the profile of the flux distribution which is controlled by the pinning centers. The measurements also evidenced an anomalous penetration in small sized single crystals. In additions, we obtained the average direction of the vortices when the applied field is titled from the c axis and we showed that the vortex direction depends on the way the field is applied (ZFC or FC configuration) and that there exists a competition between the pinning forces and the intrinsic anisotropy. (author)

  11. Infrared studies of the superconducting energy gap and normal-state dynamics of the high-Tc superconductor YBa2Cu3O7

    International Nuclear Information System (INIS)

    Schlesinger, Z.; Collins, R.T.; Holtzberg, F.; Feild, C.; Koren, G.; Gupta, A.

    1990-01-01

    A detailed study of infrared properties (reflectivity, conductivity, and dielectric response), emphasizing reproducible results from fully oxygenated YBa 2 Cu 3 O 7 crystals (T c congruent 93 K) and films, is presented. The extrapolated values of σ 1 (ω) at low frequency are roughly consistent with the measured temperature-dependent dc resistivity. Although not well understood, this infrared conductivity can be interpreted in terms of a frequency-dependent scattering rate of ∼kT+ℎω, with a low-frequency mass enhancement of roughly 2 to 4 associated with a carrier-spin related interaction. Infrared measurements polarized along the c axis suggest a conductivity anisotropy of roughly 40:1 near T c in the normal state. In the superconducting state an energy scale of 2Δ c congruent 3kT c is suggested by c-axis polarized measurements, while a much larger characteristic energy of 2Δ a-b congruent 8kT c is evident in the (a-b)-plane conductivity. From the area missing from the conductivity up to this very large gap, a reasonable estimate (congruent 1700 A) for the (a-b)-plane penetration depth is obtained. Evidence for non-BCS temperature dependence, strong pair breaking scattering, and possible fluctuation effects is discussed. A comparison to infrared data from Bi 2 Sr 2 CaCu 2 O 8-y shows a similarly large energy scale, 2Δ a-b congruent 8kT c ; for the cubic Ba 0.6 K 0.4 BiO 3 superconductor a more conventional energy scale, 2Δ congruent 4kT c is observed

  12. Effect of Y2O3 Nanoparticles on Critical Current Density of YBa2Cu3O7-x Thin Films

    International Nuclear Information System (INIS)

    Tran, H. D.; Reddy, Sreekantha; Wie, C. H.; Kang, B.; Oh, Sang Jun; Lee, Sung Ik

    2009-01-01

    Introduction of proper impurity into YBa 2 Cu 3 O 7-x (YBCO) thin films is an effective way to enhance its flux-pinning properties. We investigate effect of Y 2 O 3 nanoparticles on the critical current density J c of the YBCO thin films. The Y 2 O 3 nanoparticles were created perpendicular to the film surface (parallel with the c-axis) either between YBCO and substrate or on top of YBCO, YBCO/Y 2 O 3 /LAO or Y 2 O 3 /YBCO/STO, by pulsed laser deposition. The deposition temperature of the YBCO films were varied (780 degree C and 800 degree C) to modify surface morphology of the YBCO films. Surface morphology characterization revealed that the lower deposition temperature of 780 degree C created nano-sized holes on the YBCO film surface which may behave as intrinsic pinning centers, while the higher deposition temperature produced much denser and smoother surface. J-c values of the YBCO films with Y 2 O 3 particles were either remained nearly the same or decreased for the samples in which YBCO is grown at 780 degree C. On the other hand, J-c values were enhanced for the samples in which YBCO is grown at higher temperature of 800 degree C. The difference in the effect of Y 2 O 3 can be explained by the fact that the higher deposition temperature of 800 degree C reduces intrinsic pinning centers and J c is enhanced by introduction of artificial pinning centers in the form of Y 2 O 3 nanoparticles.

  13. Flux pinning properties of YBa2Cu3O7-δ thin films containing a high density of nanoprecipitates: A comparative study to reveal size effects

    Science.gov (United States)

    Yamasaki, Hirofumi; Yamada, Hiroshi

    2017-11-01

    Temperature dependence of critical current density Jc(H, T) was measured in moderate magnetic fields (H ⊥ film) in two thermally co-evaporated YBa2Cu3O7-δ (YBCO) thin films (A, B) and two YBCO films (C, D) deposited using a pulsed-laser deposition method. All sample films were grown epitaxially with the c-axis perpendicular to the surface of a single-crystalline substrate. Transmission electron microscopy observation revealed that these four films contained a high density of nanoprecipitates with typical sizes of 3.6 - 5.0 nm (A), 5.0 - 7.1 nm (B), 7.0 - 10.1 nm (C) and 8.7 - 14.3 nm (D). Films A and B contained very fine nanoprecipitates, whose typical diameters Dtyp are smaller than double the estimated Ginzburg-Landau coherence length 2ξab at T = 77 K, and exhibited a steep increase of Jc with decreasing temperature. Whereas, film D, which contained relatively large nanoprecipitates (Dtyp > 2ξab at T ≤ 70 K), exhibited a gradual increase in Jc. This led to a remarkable crossing of the Jc(T) curves. The temperature dependence of Jc(H//c) under a fixed magnetic field is approximated by Jc ∼ (1 - T/Tc)m(1 + T/Tc)2 where the index m is larger for films containing finer precipitates; that is, m(A) > m(B) > m(C) > m(D). This means that finer nanoprecipitates generally cause steeper Jc increase at low temperatures, which is the origin of the observed crossing phenomenon. The experimental results are reasonably explained by several theoretical models based on the direct summation of elementary pinning forces fp calculated by core pinning interactions.

  14. Functional behavior of the anomalous magnetic relaxation observed in melt-textured YBa_2Cu_3O_7_-_δ samples showing the paramagnetic Meissner effect

    International Nuclear Information System (INIS)

    Dias, F.T.; Vieira, V.N.; Garcia, E.L.; Wolff-Fabris, F.; Kampert, E.; Gouvêa, C.P.; Schaf, J.; Obradors, X.; Puig, T.; Roa, J.J.

    2016-01-01

    Highlights: • Paramagnetic Meissner effect observed up to 5T in FCC and FCW measurements. • Time effects evidenced by irreversibilities between FCC and FCW measurements. • Strong time effects causing an anomalous paramagnetic relaxation. • Paramagnetic relaxation governed by different flux dynamics in different intervals. • An interpretative analysis to identify the flux dynamics in the relaxation process. - Abstract: We have studied the functional behavior of the field-cooled (FC) magnetic relaxation observed in melt-textured YBa_2Cu_3O_7_-_δ (Y123) samples with 30 wt% of Y_2Ba_1Cu_1O_5 (Y211) phase, in order to investigate anomalous paramagnetic moments observed during the experiments. FC magnetic relaxation experiments were performed under controlled conditions, such as cooling rate and temperature. Magnetic fields up to 5T were applied parallel to the ab plane and along the c-axis. Our results are associated with the paramagnetic Meissner effect (PME), characterized by positive moments during FC experiments, and related to the magnetic flux compression into the samples. After different attempts our experimental data could be adequately fitted by an exponential decay function with different relaxation times. We discuss our results suggesting the existence of different and preferential flux dynamics governing the anomalous FC paramagnetic relaxation in different time intervals. This work is one of the first attempts to interpret this controversial effect in a simple analysis of the pinning mechanisms and flux dynamics acting during the time evolution of the magnetic moment. However, the results may be useful to develop models to explain this interesting and still misunderstood feature of the paramagnetic Meissner effect.

  15. Evidence for a common high-temperature superconducting effect in La/sub 1.85/Sr/sub 0.15/CuO4 and YBa2Cu3O7

    International Nuclear Information System (INIS)

    Jean, Y.C.; Kyle, J.; Nakanishi, H.

    1988-01-01

    We report the positron-annihilation lifetime and Doppler-broadening energy spectra in La/sub 1.85/Sr/sub 0.15/CuO 4 superconductors for 10 4 and YBa 2 Cu 3 O 7 are similar and suggest that this is a consequence of a common physics involving the delicate balance between localized and itinerant-electron behavior

  16. Sr2YSbO6 como potencial sustrato para la deposición de películas supercnductoras de YBa2Cu3O7

    Directory of Open Access Journals (Sweden)

    Omar Ortiz

    2003-01-01

    Full Text Available Se sinteitzó un nuevo material y por medio de la técnica de difracción de rayos X se encontró que su ordenamiento estructual corresponde al de una perovskita compleja de tipo A2BB'O6 con valor de parámetro de red 8,2561 A. Este estudio junto con un análisis EDX permitieron asignar a este compuesto la fórmula Sr2YSbO6. Se elaboraron mezclas homogéneas de este material con YBa2Cu3O7-δ, compactando luego las muestras en forma de pastilla para someterlas a un tratamiento térmico a 900 ºC durante diez horas. Los estudios de difracción de rayos X y magnetización para temperaturas entre 5 y 300 K sobre estas mezclas permitieron determinar que Sr2YSbO6 no reaccionó químicamente con el YBa2Cu3O7-δ y no altero el valor de la temperatura de transiión del superconductor a pesar del tratamiento térmico. Estos estudios permitieron determinar que el nuevo material Sr2YSbO6 podría ser utilizado como sustrato para el crecimiento epitaxial de películas superconductoras de YBa2Cu3O7-δ.

  17. Preparation of YBa2Cu3O7-δ powders by the thermal decomposition of a heteronuclear complex, CuY1/3Ba2/3(dhbaen)(NO3)1/3(H2O)3

    International Nuclear Information System (INIS)

    Hasegawa, E.; Aono, H.; Sadaoka, Y.; Traversa, E.

    1999-01-01

    YBa 2 Cu 3 O 7-δ powders were prepared by the thermal decomposition of a heteronuclear complex, CuY 1/3 Ba 2/3 (dhbaen)(NO 3 ) 1/3 (H 2 O) 3 . The products of the complex thermal decomposition were analyzed by TG-DTA, XRD, SEM-Auger and XPS. The decomposition of the CuY 1/3 Ba 2/3 -complex was obtained at about 500 C and the product was a mixture of oxides and carbonates. The formation of YBa 2 Cu 3 O 7-δ proceeded at 800 C, with a gradual decomposition of the carbonates. A homogeneous distribution of each element, Y, Ba, and Cu, was observed for the decomposed CuY 1/3 Ba 2/3 -complex by SEM-Auger analysis. The binding energy values of Ba3d 5/2 and O1s photolines from Ba and O in the superconductive lattice did not shift during the sputtering period. Furthermore, the formation of Ba rich regions on the surface was depressed by using the complex as a starting material for homogeneous 123-oxide, YBa 2 Cu 3 O 7-δ . (orig.)

  18. Barium contributions to the valence electronic structure of YBa2Cu3O7-δ, PrBa2Cu3O7-δ, and other barium-containing compounds

    International Nuclear Information System (INIS)

    Mueller, D.R.; Wallace, J.S.; Jia, J.J.; O'Brien, W.L.; Dong, Q.; Callcott, T.A.; Miyano, K.E.; Ederer, D.L.

    1995-01-01

    Monochromatic photon beams were used to excite barium N IV,V soft x-ray emission spectra from YBa 2 Cu 3 O 7-δ , PrBa 2 Cu 3 O 7-δ , BaF 2 , and BaTiO 3 . Near threshold excitation was used to demonstrate that small contributions to the barium N V and N IV emission spectra in the energy region above the 5p→4d core-core transitions do not arise as satellite emission from transitions in multiply excited atoms but rather occur as a result of transitions from the valence states. The emission spectrum of YBa 2 Cu 3 O 7-δ and PrBa 2 Cu 3 O 7-δ reveals a contribution to the electronic density of states at the barium site in the region near the Fermi level. The YBa 2 Cu 3 O 7-δ compound is a superconductor and PrBa 2 Cu 3 O 7-δ is an insulator. It has been proposed that the difference between them is due to mixing of praseodymium and barium among the sites occupied by yttrium and barium, with an accompanying change in electronic structure. However, our measurements indicate that the barium partial density of states for the two compounds are essentially identical

  19. Preparation of YBa2Cu3O7-x superconducting solutions and films from alkoxide-based precursors using sol-gel method and investigation of their chemical reaction mechanisms

    International Nuclear Information System (INIS)

    Mutlu, Ibrahim Halil; Acun, Hediye; Celik, Erdal; Turkmen, Hasan

    2007-01-01

    In the development of coated superconductors sol-gel technique has been widely used as an effective processing method, especially in making long-length wires and tapes. However, one drawback associated with the deposition of YBa 2 Cu 3 O 7-x and Gd 2 O 3 buffer layer on Ni tape is the adhesion characteristic at interfaces YBCO-Gd 2 O 3 and Gd 2 O 3 -NiO and NiO-Ni substrate. In this paper, two strategies for adhesion enhancement of multilayered ceramic oxide coatings on Ni substrate were proposed: (1) formation of chemical bonds through surface condensation reactions, and development of ceramic networks through diffusion of alkoxide precursors. The current research has focused on the fabrication and adhesion of YBCO coatings on buffered Ni substrate using nine solutions prepared from Y, Ba and Cu alkoxides, solvent and chelating agent. Only two of YBCO solutions were successfully obtained while the rest of them were unsuccessful. Among these solutions we scrutinized chemical reaction mechanisms of a successful and an unsuccessful solution for comparison. How the chemical bonds and solubility were affected by the acids, base and solvents used in the solutions was demonstrated. It was shown that pH of the solution, homogeneity of the solution and gelation, steric affect of the chemicals in sol-gel solutions are significant issues to obtain high quality superconducting YBCO thin films. In addition, X-ray diffraction (XRD) was used to analyze phase structure of YBCO and compare results of chemical reactions obtained by a chemdraw programme. Scanning electron microscope (SEM) studies was carried out to examine microstructures of YBCO films produced from alkoxide precursors, solvent, chelating agent and modifying liquid chemical materials such as triethanolamine or ammonium hydroxide. It was found to be YBCO, Gd 2 O 3 , NiO and Ni phases in YBCO/Gd 2 O 3 /Ni sample from XRD analysis. That the solution prepared by using triethanolamine provided the best film quality and

  20. Directly coupled direct current superconducting quantum interference device magnetometers based on ramp-edge Ag:YBa2Cu3O7-x/PrBa2Cu3O7-x/Ag:YBa2Cu3O7-x junctions

    International Nuclear Information System (INIS)

    Jia, Q.X.; Yan, F.; Mombourquette, C.; Reagor, D.

    1998-01-01

    Directly coupled dc superconducting quantum interference device (SQUID) magnetometers on LaAlO 3 substrates were fabricated using ramp-edge superconductor/normal-metal/superconductor junctions, where Ag-doped YBa 2 Cu 3 O 7-x was used for the electrode and PrBa 2 Cu 3 O 7-x for the normal-metal barrier. A flux noise of 8x10 -6 Φ 0 Hz -1/2 at 10 kHz measured with a dc bias current was achieved at 75 K, which corresponded to a field sensitivity of 400fTHz -1/2 for a magnetometer with a pick-up loop area of 8.5mmx7.5mm. Most significantly, the noise floor increased at lower frequencies with a frequency dependence slightly less than 1/f. The field noise of the SQUID magnetometers increased by only 25% after cycling the devices from zero field to 500 mG. In a static earth close-quote s magnetic field background, the field noise of the SQUID magnetometers increased by less than a factor of 2. copyright 1998 American Institute of Physics

  1. Progress of long coated conductors fabrication with fluorine-free CSD method at SWJTU

    International Nuclear Information System (INIS)

    Zhao, Y.; Wang, W.T.; Lei, M.; Pu, M.H.; Zhang, Y.; Cheng, C.H.

    2013-01-01

    Highlights: • Recent progress on the long coated conductors fabrication by F-free CSD method is presented. • Single buffer and partial-melting technology and slot-die coating methods have been developed. • Reel-to-reel facilities for continuous process have been achieved. -- Abstract: Recent progress on the fabrication of long high-T c superconducting coated conductors with a fluorine-free chemical solution deposition (CSD) method is presented. Developments including such novel methods as single buffer technology, partial-melting process on YBa 2 Cu 3 O 7 (YBCO), slot-die coating and drying; reel-to-reel facilities for continuous process have been achieved in the effort on high-T c superconducting coated conductors at SWJTU, which form a comprehensive technology to fabricate long coated tapes with high performances

  2. μSR investigations of the high temperature superconductors La1.85Sr0.15CuO4 and YBa2Cu3O7

    International Nuclear Information System (INIS)

    Birrer, P.; Gygax, F.N.; Hitti, B.

    1987-01-01

    μSR studies of La 1.85 Sr 0.15 CuO 4 and YBa 2 Cu 3 O 7-δ high temperature superconductors are carried out. The interval magnetic properties of these systems are studied on a microscopic level in the 4 kOe magnetic field and in the temperature range 10 K - 120 K. The magnetic penetration depth λ in this system did not show any significant differences from the two temperature scans (10 K and 120 K) and it destroys a field independence above 1 kOe. For T=OK the authers obtain λ(OK)≅2650 A

  3. Distribution of flux-pinning energies in YBa2Cu3O(7-delta) and Bi2Sr2CaCu2O(8+delta) from flux noise

    Science.gov (United States)

    Ferrari, M. J.; Johnson, Mark; Wellstood, Frederick C.; Clarke, John; Mitzi, D.

    1990-01-01

    The spectral density of the magnetic flux noise measured in high-temperature superconductors in low magnetic fields scales approximately as the inverse of the frequency and increases with temperature. The temperature and frequency dependence of the noise are used to determine the pinning energies of individual flux vortices in thermal equilibrium. The distribution of pinning energies below 0.1 eV in YBa(2)Cu(3)O(7-delta) and near 0.2 eV in Bi(2)Sr(2)CaCu(2)O(8+delta). The noise power is proportional to the ambient magnetic field, indicating that the vortex motion is uncorrelated.

  4. Distribution of flux-pinning energies in YBa2Cu3O7-δ and Bi2Sr2CaCu2O8+δ from flux noise

    International Nuclear Information System (INIS)

    Ferrari, M.J.; Johnson, M.; Wellstood, F.C.; Clarke, J.; Mitzi, D.; Rosenthal, P.A.; Eom, C.B.; Geballe, T.H.; Kapitulnik, A.; Beasley, M.R.

    1990-01-01

    The spectral density of the magnetic flux noise measured in high-temperature superconductors in low magnetic fields scales approximately as the inverse of the frequency and increases with temperature. We use the temperature and frequency dependence of the noise to determine the pinning energies of individual flux vortices in thermal equilibrium. The distribution of pinning energies peaks below 0.1 eV in YBa 2 Cu 3 O 7-δ and near 0.2 eV in Bi 2 Sr 2 CaCu 2 O 8+δ . The noise power is proportional to the ambient magnetic field, indicating that the vortex motion is uncorrelated

  5. Distribution of isotopes produced in superconductor YBa2Cu3O7-x and ferroelectric PbZr0.54Ti0.46O3 under irradiation by high-energy charged particles

    International Nuclear Information System (INIS)

    Didik, V.A.; Malkovich, R.Sh.; Skoryatina, E.A.; Kozlovskij, V.V.

    1998-01-01

    The concentration profiles of transmutation radioactive isotopes, formed in the YBa 2 Cu 3 O 7-x superconductor and PbZr 0.54 Ti 0.46 O 3 ferroelectric under high-energy proton radiation (with 10 and 15 MeV energy), deuterons (4 MeV), the 3 He and 4 He nuclei (20 MeV), are studied. Two types of the concentration profiles: monotonous ones and profiles with the maximum are identified. It is shown that the isotope profile is determined by the character of energy dependence of the nuclear reaction cross section, leading to formation of the given isotope

  6. Structural and electrical characterization of ultra-thin SrTiO3 tunnel barriers grown over YBa2Cu3O7 electrodes for the development of high Tc Josephson junctions.

    Science.gov (United States)

    Félix, L Avilés; Sirena, M; Guzmán, L A Agüero; Sutter, J González; Vargas, S Pons; Steren, L B; Bernard, R; Trastoy, J; Villegas, J E; Briático, J; Bergeal, N; Lesueur, J; Faini, G

    2012-12-14

    The transport properties of ultra-thin SrTiO(3) (STO) layers grown over YBa(2)Cu(3)O(7) electrodes were studied by conductive atomic force microscopy at the nano-scale. A very good control of the barrier thickness was achieved during the deposition process. A phenomenological approach was used to obtain critical parameters regarding the structural and electrical properties of the system. The STO layers present an energy barrier of 0.9 eV and an attenuation length of 0.23 nm, indicating very good insulating properties for the development of high-quality Josephson junctions.

  7. Structural and electrical characterization of ultra-thin SrTiO3 tunnel barriers grown over YBa2Cu3O7 electrodes for the development of high Tc Josephson junctions

    International Nuclear Information System (INIS)

    Avilés Félix, L; Sirena, M; Agüero Guzmán, L A; González Sutter, J; Pons Vargas, S; Steren, L B; Bernard, R; Trastoy, J; Villegas, J E; Briático, J; Bergeal, N; Lesueur, J; Faini, G

    2012-01-01

    The transport properties of ultra-thin SrTiO 3 (STO) layers grown over YBa 2 Cu 3 O 7 electrodes were studied by conductive atomic force microscopy at the nano-scale. A very good control of the barrier thickness was achieved during the deposition process. A phenomenological approach was used to obtain critical parameters regarding the structural and electrical properties of the system. The STO layers present an energy barrier of 0.9 eV and an attenuation length of 0.23 nm, indicating very good insulating properties for the development of high-quality Josephson junctions. (paper)

  8. Evolution of the specific-heat anomaly of the high-temperature superconductor YBa2Cu3O7 under influence of doping through application of pressure up to 10 GPa

    OpenAIRE

    Lortz, Rolf; Junod, Alain; Jaccard, Didier; Wang, Yuxing; Meingast, Christoph; Masui, Takahiko; Tajima, Setsuko

    2005-01-01

    The evolution of the specific-heat anomaly in the overdoped range of a single crystal of the high-temperature superconductor YBa2Cu3O7 has been studied under influence of pressure up to 10 GPa, using AC calorimetry in a Bridgman-type pressure cell. We show that the specific-heat jump as well as the bulk Tc are reduced with increasing pressure in accordance with a simple charge-transfer model. This new method enables us through pressure-induced charge transfer to study the doping dependence of...

  9. Comparative study of electrical transport and magnetic measurements of Y3Ba5Cu8O18±δ and YBa2Cu3O7-δ compounds: intragranular and intergranular superconducting properties

    Science.gov (United States)

    Slimani, Y.; Hannachi, E.; Ben Salem, M. K.; Ben Azzouz, F.; Ben Salem, M.

    2018-02-01

    We compare the superconducting properties and flux pinning characteristics between YBa2Cu3O7-δ (called Y-123) and Y3Ba5Cu8O18±δ (called Y-358) compounds. Both samples were synthesized through the solid-state reaction. The samples were examined by X-ray diffraction, and scanning electron microscope coupled with energy dispersive spectrometry. The critical current densities of the prepared samples were investigated using current-voltage, magnetization measurements and ac-susceptibility. It is demonstrated that the Y-358 exhibits better superconducting and pinning properties than the Y-123 one. This may be ascribed to the layered structure and the occurrence of a greater number of insulating layers between the CuO2 planes that act as effective pinning sites and consequently conduce to a better fundamental pinning capacity in Y-358.

  10. Studies of metallic species incorporation during growth of SrBi2Ta2O9 films on YBa2Cu3O7-x substrates using mass spectroscopy of recoiled ions

    International Nuclear Information System (INIS)

    Dhote, A. M.

    1999-01-01

    The incorporation of metallic species (Bi, Sr and Ta) during the growth of layered perovskite SrBi 2 Ta 2 O 9 (SBT) on a-axis oriented YBa 2 Cu 3 O 7-x (YBCO) conducting oxide substrates has been investigated using in situ low energy mass spectroscopy of recoiled ions (MSRI). This technique is capable of providing monolayer-specific surface information relevant to the growth of single and multi-component thin films and layered heterostructures. The data show a temperature dependence of metallic species incorporation during co-deposition of Sr, Bi and Ta on YBCO surfaces. At high temperatures (400 400 C. SBT films grown at temperatures ≤ 400 C and annealed in oxygen or air at 800 C exhibit a polycrystalline structure with partial a-axis orientation

  11. First-Principles Calculations of Electronic States and Self-Doping Effects at a 45° Grain Boundary in the High Temperature YBa2Cu3O7 Superconductor

    KAUST Repository

    Schwingenschlö gl, Udo; Schuster, Cosima

    2009-01-01

    The charge redistribution at grain boundaries determines the applicability of high-Tc superconductors in electronic devices because the transport across the grains can be hindered considerably. We investigate the local charge transfer and the modification of the electronic states in the vicinity of the grain-grain interface by ab initio calculations for a (normal-state) 45°-tilted [001] grain boundary in YBa2Cu3O7. Our results explain the suppressed interface transport and the influence of grain boundary doping in a quantitative manner, in accordance with the experimental situation. The charge redistribution is found to be strongly inhomogeneous, which has a substantial effect on transport properties since it gives rise to a self-doping of 0.10±0.02 holes per Cu atom.

  12. High Ic, YBa2Cu3O7-x films grown at very high rates by liquid assisted growth incorporating lightly Au-doped SrTiO3 buffers

    International Nuclear Information System (INIS)

    Kursumovic, A; Durrell, J H; Harrington, S; Wimbush, S; MacManus-Driscoll, J L; Maiorov, B; Zhou, H; Stan, L; Holesinger, T G; Wang, H

    2009-01-01

    YBa 2 Cu 3 O 7-x (YBCO) thick films were grown by hybrid liquid phase epitaxy (HLPE) on (001) SrTiO 3 (STO) substrates. In the presence of a 100 nm thick, 5 mol% Au-doped STO buffer, self-field critical current densities, J c sf , at 77 K of ∼2.4 MA cm -2 and critical currents, I c sf , up to 700 A (cm-width) -1 were achieved. The J c value is virtually independent of thickness and the growth rates are very high (∼1 μm min -1 ). From transmission electron microscopy (TEM), Y 2 O 3 nanocloud extended defects (∼100 nm in size) were identified as the pinning defects in the films. Enhanced random pinning was induced by the presence of Au in the buffer.

  13. Structure, resistivity, critical field, specific-heat jump at Tc, Meissner effect, a.c. and d.c. susceptibility of the high-Tc superconductor YBa2Cu3O7

    International Nuclear Information System (INIS)

    Junod, A.; Bezinge, A.; Graf, T.

    1987-01-01

    YBa 2 Cu 3 O 7 superconductors with inductive transitions as narrows as 0.45 K above 90 K were synthetized. Samples were characterized by thermogravimetry, differential thermal analysis, X-ray and neutron diffraction. The structure is characterized by a two-dimensional Cu-O network with square-pyramidal and square-planar coordinated Cu atoms. Results show a clear metallic behaviour of the resistivity. An orbital critical field as high as 300 T is extrapolated. Meissner flux expulsion up to 40% is observed. Small amounts of magnetic Cu 2+ ions are correlated with the presence of the impurity phase BaCuO 2 . The Pauli susceptibility and the specific-heat jump at T c are consistent with γ ≅ 2mJ/(K 2 gat) (9mJ/(K 2 mole-Cu)), neglecting all renormalizations

  14. Evolution of the specific-heat anomaly of the high-temperature superconductor YBa2Cu3O7 under the influence of doping through application of pressure up to 10 GPa

    International Nuclear Information System (INIS)

    Lortz, Rolf; Junod, Alain; Jaccard, Didier; Wang, Yuxing; Meingast, Christoph; Masui, Takahiko; Tajima, Setsuko

    2005-01-01

    The evolution of the specific-heat anomaly in the overdoped range of a single crystal of the high-temperature superconductor YBa 2 Cu 3 O 7 has been studied under the influence of pressure up to 10 GPa, using AC calorimetry in a Bridgman-type pressure cell. We show that the specific-heat jump as well as the bulk T c are reduced with increasing pressure in accordance with a simple charge-transfer model. This new method enables us through pressure-induced charge transfer to study the doping dependence of the superconducting transition, as well as the evolution of the superconducting condensation energy on a single stoichiometric sample without adding atomic disorder

  15. Sputtering yields of YBa2Cu3O7 and Bi2Sr2Ca2Cu3O10 by 100 keV Ar+ impact at normal incidence

    International Nuclear Information System (INIS)

    Matsunami, N.

    1998-01-01

    The thickness change of YBa 2 Cu 3 O 7-δ (YBCO) and Bi 2 Sr 2 Ca 2 Cu 3 O 10-δ (Bi-2223) films by 100 keV Ar + impact at normal incidence has been measured using 1.8 MeV He Rutherford backscattering method. The sputtering yields of YBCO and Bi-2223 films are determined as 2.5 and 1.7 atoms per ion, respectively. A considerable segregation of Y is observed for YBCO by ion impact. Comparing the experimental sputtering yields with those of a computer simulation, the effective surface binding energies for the films of non-superconducting phase are obtained as 3.0 and 4.5 eV for YBCO and Bi-2223, respectively. These surface binding energies are compared with those of thermodynamics. (orig.)

  16. First-Principles Calculations of Electronic States and Self-Doping Effects at a 45° Grain Boundary in the High Temperature YBa2Cu3O7 Superconductor

    KAUST Repository

    Schwingenschlögl, Udo

    2009-06-03

    The charge redistribution at grain boundaries determines the applicability of high-Tc superconductors in electronic devices because the transport across the grains can be hindered considerably. We investigate the local charge transfer and the modification of the electronic states in the vicinity of the grain-grain interface by ab initio calculations for a (normal-state) 45°-tilted [001] grain boundary in YBa2Cu3O7. Our results explain the suppressed interface transport and the influence of grain boundary doping in a quantitative manner, in accordance with the experimental situation. The charge redistribution is found to be strongly inhomogeneous, which has a substantial effect on transport properties since it gives rise to a self-doping of 0.10±0.02 holes per Cu atom.

  17. Nucléation et croissance de films YBa_{2Cu3O_{7 - δ}} déposés par ablation laser sur substrat de MgO(001)

    Science.gov (United States)

    Keller, D.; Gervais, A.; Chambonnet, D.; Belouet, C.; Audry, C.

    1995-02-01

    In the field of superconducting devices devoted to microwave applications, the crystalline texture of high quality thin films based on YBa{2}Cu{3}O{7 - δ} is of primary importance. This study presents the formation of this texture on MgO substrates with the nucleation and growth steps up to a film thickness of 300 nm as observed by means of AFM, HRTEM and XRD. The influence of deposition temperature on the growth mode is shown and a nucleation/growth model is discussed. The minimum roughness of c_{bot 0}{(^1)} textured films, 300 nm thick and 20 × 20 mm2 in size is as slow as 2 nm. Dans le cadre de la réalisation de composants supraconducteurs de haute qualité à base du composé YBa{2}Cu{3}O{7 - δ} destinés aux applications en hyperfréquences, le contrôle de la texture cristalline des films est de première importance. La formation de celle-ci sur substrat MgO est étudiée depuis la nucléation jusqu'à une épaisseur de 300 nm au moyen de la microscopie à force atomique, de la microscopie électronique en transmission à haute résolution et de la diffraction des rayons X. L'influence de la température de dépôt sur le mode de croissance est abordée et un modèle de nucléation/croissance est discuté. La rugosité minimale des films d'épaisseur 300 nm et de dimensions 20 × 20 mm2 de texture c_{bot 0}{(^1)} est voisine de 2 nm.

  18. Dependences of microstructure and critical current density on the thickness of YBa2Cu3O7-x film prepared by pulsed laser deposition on buffered Ni–W tape

    International Nuclear Information System (INIS)

    Xu, Da; Wang, Ying; Liu, Linfei; Li, Yijie

    2013-01-01

    YBa 2 Cu 3 O 7−x (YBCO) films with different thicknesses were fabricated on buffered Ni–W tapes by pulsed laser deposition. The thickness dependences of microstructure and critical current density (J c ) of YBCO film were systematically investigated. The microstructure and surface morphology of YBCO film were characterized by X-ray diffraction, optical microscopy, field emission scanning electron microscopy and atomic force microscopy. And the critical current (I c ) of YBCO film was measured by the conventional four-probe method. We found that the full width at half maximum values of both omega and phi scan rocking curves, the content of a-axis oriented grain, and surface roughness of YBCO film all increased with augmenting the thickness of YBCO film. It was also found that with increasing the thickness of YBCO film from 0.3 μm to 1.5 μm, the I c of YBCO film increased from 72 A/cm to 248 A/cm and yet J c of YBCO film decreased from 2.1 × 10 6 A/cm 2 to 1.6 × 10 6 A/cm 2 . Our results indicated that the microstructure and J c of YBCO film were largely dependent on the thickness of YBCO film under the optimized deposition condition of substrate temperature. - Highlights: ► YBa 2 Cu 3 O 7−x (YBCO) films with different thicknesses were grown on metallic tapes. ► The texture and critical current were dependent on the thickness of YBCO film. ► Thickness effect was weakened by fabricating YBCO film layer by layer

  19. First steps towards cube textured nickel profile wires for YBCO-coated conductors

    International Nuclear Information System (INIS)

    Eickemeyer, J.; Gueth, A.; Freudenberger, J.; Holzapfel, B.; Schultz, L.

    2011-01-01

    The cube texture as a typical sheet texture can also be formed by cold drawing and recrystallization in profile wires. Cube textured Ni profile wires containing up to 96.2% cube oriented grains in the central region were obtained. Forthcoming investigations are promising to get a textured substrate wire for YBCO-coated conductors. Cube textured nickel alloy tapes prepared by cold rolling and annealing (RABiTS method) represent a standard metallic substrate for superconductor coatings of the YBa 2 Cu 3 O 7-δ (YBCO) type. These tapes have a width to thickness ratio of about 30-100. However, a value of close to one is optimal concerning low energetic losses under alternating current applications. First experiments on micro-alloyed nickel prove that the cube texture as a typical sheet texture can also be formed in profile wires with a rectangular cross-section after cold drawing and recrystallization treatment.

  20. Angular dependence of Jc for YBCO coated conductors at low temperature and very high magnetic fields

    International Nuclear Information System (INIS)

    Xu, A; Jaroszynski, J J; Kametani, F; Chen, Z; Larbalestier, D C; Viouchkov, Y L; Chen, Y; Xie, Y; Selvamanickam, V

    2010-01-01

    We present very high field angle dependent critical current density (J c ) data for three recently obtained YBa 2 Cu 3 O 7-x (YBCO) coated conductors used in the construction of high field solenoids. We find that strongly correlated pins, such as BaZrO 3 (BZO) nanorods, while yielding strong c-axis peaks at 77 K, produce almost no measurable contribution at 4 K. Raising the field from c (θ) at low fields to a marked cusp-like behavior at high fields. Transmission electron micrographs show that all samples contain a high density of stacking faults which strengthen the plane correlated pinning parallel to the ab planes produced by the intrinsic ab-plane pinning of the Cu-O charge reservoir layers.

  1. Processing of La(1.8)Sr(0.2)CuO4 and YBa2Cu3O7 superconducting thin films by dual-ion-beam sputtering

    Science.gov (United States)

    Madakson, P.; Cuomo, J. J.; Yee, D. S.; Roy, R. A.; Scilla, G.

    1988-03-01

    High-quality La(1.8)Sr(0.2)CuO4 and YBa2Cu3O7 superconducting thin films, with zero resistance at 88 K, have been made by dual-ion-beam sputtering of metal and oxide targets at elevated temperatures. The films are about 1.0 micron thick and are single phase after annealing. The substrates investigated are Nd-YAP, MgO, SrF2, Si, CaF2, ZrO2-(9 pct)Y2O3, BaF2, Al2O3, and SrTiO3. Characterization of the films was carried out using Rutherford backscattering spectroscopy, resistivity measurements, TEM, X-ray diffraction, and SIMS. Substrate/film interaction was observed in every case. This generally involves diffusion of the substrate into the film, which is accompanied by, for example, the replacement of Ba by Sr in the YBa2Cu2O7 structure, in the case of SrTiO3 substrate. The best substrates were those that did not significantly diffuse into the film and which did not react chemically with the film.

  2. Processing of La/sub 1.8/Sr/sub 0.2/CuO4 and YBa2Cu3O7 superconducting thin films by dual-ion-beam sputtering

    International Nuclear Information System (INIS)

    Madakson, P.; Cuomo, J.J.; Yee, D.S.; Roy, R.A.; Scilla, G.

    1988-01-01

    High quality La/sub 1.8/Sr/sub 0.2/CuO 4 and YBa 2 Cu 3 O 7 superconducting thin films, with zero resistance at 88 K, have been made by dual-ion-beam sputtering of metal and oxide targets at elevated temperatures. The films are about 1.0 μm thick and are single phase after annealing. The substrates investigated are Nd-YAP, MgO, SrF 2 , Si, CaF 2 , ZrO 2 -9% Y 2 O 3 , BaF 2 , Al 2 O 3 , and SrTiO 3 . Characterization of the films was carried out using Rutherford backscattering spectroscopy, resistivity measurements, transmission electron microscopy, x-ray diffraction, and secondary ion mass spectroscopy. Substrate/film interaction was observed in every case. This generally involves diffusion of the substrate into the film, which is accompanied by, for example, the replacement of Ba by Sr in the YBa 2 Cu 2 O 7 structure, in the case of SrTiO 3 substrate. The best substrates were those that did not significantly diffuse into the film and which did not react chemically with the film. In general, the superconducting transition temperature is found to depend on substrate temperature and ion beam energy, film composition, annealing conditions, and the nature and the magnitude of the substrate/film interaction

  3. Effects of 3.1-MeV proton and 1-GeV Au-ion irradiation on the magnetic flux noise and critical current of YBa2Cu3O7

    International Nuclear Information System (INIS)

    Shaw, T.J.; Clarke, J.; van Dover, R.B.; Schneemeyer, L.F.; White, A.E.

    1996-01-01

    We have used a dc superconducting quantum interference device to measure the spectral density of magnetic flux noise, S Φ (f), generated by vortex motion in crystals of YBa 2 Cu 3 O 7-δ (YBCO) both before and after irradiation with 3.1-MeV protons and 1-GeV Au ions. In addition, we have studied the effects of irradiation on the critical current J c of the same samples. Both types of irradiation reduced S Φ (f) at most temperatures and magnetic fields and increased J c at all temperatures and magnetic fields. By measuring S Φ (f) versus temperature, we extract the distribution of vortex pinning energies, D(U 0 ). Both crystals have peaks in D(U 0 ) near 0.1 eV and 0.2 eV before irradiation, and a much reduced peak near 0.1 eV after irradiation. The noise level after either kind of irradiation was substantially higher than in an unirradiated YBCO film. copyright 1996 The American Physical Society

  4. Analysis of the fluctuation-induced excess dc conductivity of epitaxial YBa2Cu3O7 films: Influence of a short-wavelength cutoff in the fluctuation spectrum

    International Nuclear Information System (INIS)

    Hopfengaertner, R.; Hensel, B.; Saemann-Ischenko, G.

    1991-01-01

    Measurements of the temperature dependence of the in-plane dc conductivity on various high-quality epitaxial YBa 2 Cu 3 O 7 films are presented. The rounding of the resistivity in the transition region has been analyzed in terms of the anisotropic Aslamazov-Larkin (AL), Lawrence-Doniach (LD), and Maki-Thompson theories. In the framework of the time-dependent Ginzburg-Landau (GL) approach we have investigated the influence of a short-wavelength cutoff parameter in the fluctuation spectrum of the AL and LD term. In both theories this physically reasonable cutoff leads to a considerable reduction of the predicted excess dc conductivity at higher temperatures. Moreover, the three-dimensional anisotropic AL term, taking the cutoff into account, predicts nearly the same excess conductivity as the original LD term, although these two approaches describe different systems. A good agreement between experimental data and LD as well as the modified three-dimensional anisotropic AL term was found in the region 1.01T c ≤T≤1.1T c . The zero-temperature GL coherence length ξ c (0) has been estimated to be about 1.5 A

  5. Atomic oxygen effect on the in situ growth of stoichiometric YBa2Cu3O7 - delta epitaxial films by facing targets 90° off-axis radiofrequency magnetron sputtering

    Science.gov (United States)

    Oya, Gin-ichiro; Diao, Chien Chen; Imai, Syozo; Uzawa, Takaaki; Sawada, Yasuji; Sugai, Tokuko; Nakajima, Kensuke; Yamashita, Tsutomu

    1995-06-01

    (110)- and (103)-oriented almost stoichiometric YBa2Cu3O7-δ (YBCO) films have been grown epitaxially on hot SrTiO3 (110) substrates using a 90° off-axis rf magnetron sputtering technique, for fabrication of vertical sandwich-type YBCO/insulator/YBCO or YBCO/normal metal/YBCO Josephson junctions utilizing the high-quality YBCO films. The YBCO epitaxial films with high transition temperatures Tc of ˜90 K have been deposited in situ only under the conditions of substrate temperatures Ts of ˜650-˜700 °C and oxygen partial pressure PO2 of ˜5×10-3-˜10×10-3 Torr, which are in close proximity to the critical stability/decomposition line for YBa2Cu3O6 in the ordinary Y-Ba-Cu-O phase diagram. Using a quadrupole mass spectrometer, a high density of atomic oxygen has directly been observed to be efficiently produced in the sputter glow discharge under the above optimum conditions of PO2. This atomic oxygen has played a key role in promoting the formation of the perovskite structure and the epitaxial growth of the YBCO films. Furthermore, Shapiro steps have successfully been observed for a Nb-YBCO point-contact junction, which is made by pressing a Nb needle on a surface-etched YBCO epitaxial film, under 525.4 GHz submillimeter-wave irradiation.

  6. Enhanced Jc's of YBa2Cu3O7-x-Ag ex situ annealed coevaporated films on LaAlO3 (100) substrates

    DEFF Research Database (Denmark)

    Clausen, Thomas; Ejrnæs, Mikkel; Olesen, Michael Wiinberg

    1995-01-01

    A 5x increase of the critical current density (J(c)) at 77 K was obtained by coating a coevaporated 500 nm thick Y, BaF2, Cu film with 50 nm Ag prior to the ex situ annealing. J(c) increased from 0.2 for uncoated samples to 1 MA/cm(2) for the Ag-coated sample without severely affecting the zero...... resistance transition temperature (T-c0). Scanning electron microscopy showed that the surface morphology was improved and that the normally observed trellislike structure was greatly reduced. By combining electron microscopy and sputter assisted Auger analysis it was found that the Ag nucleated in droplets...

  7. Bulk and thick films of the superconducting phase YBa2Cu3O7/sub -//sub y/ made by controlled precipitation and sol-gel processes

    International Nuclear Information System (INIS)

    Barboux, P.; Tarascon, J.M.; Greene, L.H.; Hull, G.W.; Bagley, B.G.

    1988-01-01

    The synthesis of high-temperature superconducting oxides using solution chemistry has been investigated and physical properties are compared to ceramics obtained by conventional solid-state reactions. We report on controlled precipitation and sol-gel processes, both of which produce materials with particle sizes smaller than 5 μm. We find that the superconducting properties of the high T/sub c/ ceramics are affected by their manner of preparation, such that the transitions are slightly lower in temperature, but sharper, for samples made by solution rather than solid-state chemistry. The ability to prepare stable viscous gels provides an opportunity for obtaining large areas of superconducting coatings. For thick films on alumina or silicon substrates, contamination from the substrate is shown to be a problem. Finally, we observe that the sol-gel process lowers the synthesis temperature by 100 0 C.ing,

  8. Uniform performance of continuously processed MOD-YBCO-coated conductors using a textured Ni-W substrate

    International Nuclear Information System (INIS)

    Verebelyi, D T; Schoop, U; Thieme, C; Li, X; Zhang, W; Kodenkandath, T; Malozemoff, A P; Nguyen, N; Siegal, E; Buczek, D; Lynch, J; Scudiere, J; Rupich, M; Goyal, A; Specht, E D; Martin, P; Paranthaman, M

    2003-01-01

    Second-generation coated conductor composite HTS wires have been fabricated using a continuous reel-to-reel process with deformation-textured Ni-W substrates and a metal-organic deposition process for YBa 2 Cu 3 O 7-x . Earlier results on 1 m long and 1 cm wide wires with 77 K critical current performance greater than 100 A cm -1 width have now been extended to 7.5 m in length and even higher performance, with one wire at 132 and another at 127 A cm -1 width. Performance as a function of wire length is remarkably uniform, with only 2-4% standard deviation when measured on a 50 cm length scale. The length-scale dependence of the deviation is compared with a statistical calculation. (rapid communication)

  9. YBa2Cu3O7

    International Nuclear Information System (INIS)

    Junod, A.; Eckert, D.; Graf, T.; Triscone, G.; Muller, J.

    1989-01-01

    The authors report observations based on specific heat measurements in ∼20 YBCO samples. The dependence of the specific heat at T c and at low temperatures on various parameters is investigated. The strong correlation of the specific heat jump with the Meissner fraction suggests that even the best samples with ΔC/T c = 67 mJ/(K 2 mole) are not 100% superconducting

  10. Atom-replaced pins in a Y-based superconductor—single-crystalline perovskite structure including both PrBa2Cu3O7‑x and YBa2Cu3O7‑y

    Science.gov (United States)

    Hayashi, Mariko; Araki, Takeshi; Ishii, Hirotaka; Nishijima, Gen; Matsumoto, Akiyoshi

    2018-05-01

    Metal organic deposition using trifluoroacetates (TFA-MOD) provides many uniform superconductors on long metal tapes. The large numbers of long wires have been applied for power grids or superconducting fault current limiters. The related applications worked for a long time without fatal trouble. The quasi-liquid produced during the firing process assisted the perfectly uniform structure in TFA-MOD. On the other hand, when it was desired to introduce artificial pinning centers, the quasi-liquid also enlarged the diameter of the artificial pinning centers to several tens of nanometers. In other words, due to the nature of TFA-MOD, there is very little chance of using TFA-MOD to prepare several nm-sized artificial pinning centers. By proposing atom-replaced pins (ARPs), we aim to overcome the impasse. ARPs are realized by replacing yttrium (Y) with praseodymium (Pr) whose valence number changes from 3+ to approximately 4+. Analytical results suggested that Pr makes pinning centers on a PrBa2Cu3O7‑x (PrBCO) unit cell, and the weak-linked superconductivity derived from PrBCO extends to the adjacent unit cells in the a/b-plane. J c decrease by Pr is five times as large as the volume fraction of Pr in the Y-site of the perovskite structure. On the other hand, T c does not show large degradation in YBCO including 10% PrBCO. These results suggest that PrBCO unit cells are fully dispersed in YBa2Cu3O7‑y matrix. With regard to J c in the magnetic field, (Y0.98, Pr0.02)BCO has been slightly improved compared with pure YBCO only in the region of high temperature and low magnetic field of less than 1 T.

  11. Tunable flux pinning landscapes achieved by functional ferromagnetic Fe2O3:CeO2 vertically aligned nanocomposites in YBa2Cu3O7−δ thin films

    International Nuclear Information System (INIS)

    Tsai, Chen-Fong; Huang, Jijie; Lee, Joon-Hwan; Khatkhatay, Fauzia; Chen, Li; Chen, Aiping; Su, Qing; Wang, Haiyan

    2015-01-01

    Highlights: • Functional ferromagnetic (Fe 2 O 3 ) x :(CeO 2 ) 1−x vertically aligned nanocomposites (VAN). • An ordered arrangement of ferromagnetic Fe 2 O 3 nanoinclusions. • Significant in-field improvement of J c (H//c) in both VAN nanolayer capped and buffered samples. • T c above 90 K and the J c sf maximized at 3.07 MA/cm 2 (75 K) and 9.2 MA/cm 2 (65 K) for 30% Fe 2 O 3 sample. - Abstract: Functional ferromagnetic (Fe 2 O 3 ) x :(CeO 2 ) 1−x vertically aligned nanocomposite (VAN) layers were deposited as either buffer or cap layers for YBa 2 Cu 3 O 7−δ (YBCO) thin films. The composition of Fe 2 O 3 dopants in the VAN nanolayers is controlled at 10%, 30% and 50% in order to create different arrangements of Fe 2 O 3 and CeO 2 nanopillars and therefore to tune the flux pining landscapes. The composition variation provides tunable and ordered arrangements of magnetic nanodopants and interfacial defects as pinning centers in the YBCO thin films. The superconducting property measurements show that most doped samples obtain a T c above 90 K and the J c sf measured at 75 K and 65 K maximized at 3.07 MA/cm 2 and 9.2 MA/cm 2 for 30% Fe 2 O 3 VAN doped sample. As the temperature decreased to 5 K, the sample with 50% Fe 2 O 3 VAN doped sample show the best pinning effect due to pronounced magnetic pinning effects. This work demonstrates the tunable density of magnetic pinning centers can be achieved by VAN to meet the specific pinning requirement

  12. Characterization of three-dimensional grain boundary topography in a YBa2Cu3O7-d thin film bicrystal grown on a SrTiO3 substrate

    International Nuclear Information System (INIS)

    Ayache, J.; Thorel, A.; Lesueur, J.; Dahmen, U.

    1998-01-01

    The topography and crystallography of YBa 2 Cu 3 O 7-d (YBCO) bicrystal films grown epitaxially on oriented SrTiO 3 (STO) bicrystals have been characterized by scanning and transmission electron microscopies (SEM and TEM) and atomic force microscopy (AFM). The YBCO films were formed by laser ablation on melt-grown Σ13 STO bicrystals with a misorientation of 24 degree around the left-angle 001 right-angle tilt axis. In agreement with previous reports, TEM analysis revealed that the grain boundary in the film did not always follow the planar substrate grain boundary faithfully, but undulated about the average boundary plane. High resolution electron microscopy observations of the apparently complex undulating boundary structures could be explained as a result of an overlap between different orientation variants of the orthorhombic YBCO film. Cross correlation between SEM, AFM, and TEM imaging gave a clear evidence that an island growth mechanism is responsible for the observed grain boundary structure and morphology for which a schematic model is presented. It is seen that meandering of the YBCO grain boundary (GB) is necessarily coupled to a wide range of inclination of the GB plane in the z direction. The implications of this interfacial structure for the behavior of GB based Josephson junctions are discussed and compared to models proposed in the literature. It is also seen that inclination of the GB may be responsible for the poor correlation usually found in the literature between calculations and experimental curves of current density J c versus the GB angle since the most elaborate models proposed up to now take into account only pure tilt GB plane facets, that is to say facets in the zone of the tilt axis. Moreover, such a GB structure may affect the interpretation of recent phase sensitive experiments done on bicrystal or tricrystal high T c superconductors to determine the symmetry of the order parameter. copyright 1998 American Institute of Physics

  13. Development of long GdBCO coated conductor using the IBAD/MPMT-PLD method

    International Nuclear Information System (INIS)

    Ibi, A; Fukushima, H; Yamada, Y; Miyata, S; Kuriki, R; Takahashi, K; Shiohara, Y

    2006-01-01

    We have developed long GdBa 2 Cu 3 O 7-X (GdBCO) coated conductors by a multi-plume and multi-turn pulsed laser deposition (MPMT-PLD) method and have successfully fabricated 32 and 60.7 m long GdBCO coated conductors with a high critical current, I c , and high deposition rate. The I c of the 32 and 60.7 m long GdBCO coated conductors were 205 A (J c = 1.36 MA cm -2 ) and 183 A (J c = 1.45 MA cm -2 ), respectively, at 77 K and 0 T. In addition, they exhibited higher I c values in a magnetic field than a YBa 2 Cu 3 O 7-X (YBCO) coated conductor: typically 20 A at 77 K and 3 T while the value for a YBCO coated conductor is 8 A. These high I c values are due to the smaller number of a-axis oriented grains in GdBCO than in YBCO. Furthermore, the speed of production of the GdBCO layer was increased to 10 m h -1 while that of the former YBCO coated conductor was 3.75 m h -1 . The material yield of long GdBCO layers using the MPMT-PLD method was about 26-28%. The high I c of GdBCO in a magnetic field, the high production rate and the high material yield are promising for applications

  14. Pure and Y-substituted BaZrO3 ceramics. A possible support material for fabrication of YBa2Cu3O7-x high-Tc superconductors

    International Nuclear Information System (INIS)

    Wang Xiandong.

    1993-01-01

    This thesis concerns the preparation and characterization of cuprate based high-T c superconductors (Y-123 and Bi-2223) and especially development and testing of BaZrO 3 based materials. The formation of YBa 2 Cu 3 O y (Y-123) by a CO 2 -free route involving reaction sintering of stoichiometric mixtures of chemically prepared fine powders of Y 2 BaCuO 5 , BaCuO 2 and CuO have been studied by thermal and XRD analysis. The synthesis and sintering of BaZrO 3 powders prepared by the hydroxide-alkoxide-methanol sol-gel route have been studied. The phase relations in the system BaO-Y 2 O 3 -ZrO 2 have been studied to determine the solid solubility limits for the perovskite phase Ba X Y Y Zr Z O N (X+X+Z=3) at 1500 deg. C. In the binary system Y 2 O 3 -BaZrO 3 the solubility limit was found to be ≅19 mol% Y 2 O 3 , i.e. Ba 0.81 Y 0. 4 2 Zr 0.81 O 3 . along the joint BaYO 2.5 -Ba the boundary was determined to be at BaY 0.21 Zr 0 . 79 O 2.895 . evidence for a new solid solution series between Ba 3 Y 4 O 9 and ZrO 2 are given, and a partial 1500 deg. C phase diagram for the ternary system BaO-Y 2 O 3 -ZrO 2 is presented. The growth of BaZrO 3 single crystals have been attempted both by a laser zone floating technique and flux methods. The compatibility between YBa 2 Cu 3 O 7 -X and BaZrO 3 , Ba X Y Y Zr Z O 3-δ as well as BaHfO 3 have been studied at 950 deg. and 1050 deg. C. The results show the four most promising candidates as support materials for fabrication of YBa 2 Cu 3 O y to be BaHfO 3 , BaY 0.05 Zr 0.95 O 2.975 , , BaZrO 3 and BaY 0.1 Zr 0.9 O 2.95 . (EG)

  15. Critical current survival in the YBCO superconducting layer of a delaminated coated conductor

    Science.gov (United States)

    Feng, Feng; Fu, Qishu; Qu, Timing; Mu, Hui; Gu, Chen; Yue, Yubin; Wang, Linli; Yang, Zhirong; Han, Zhenghe; Feng, Pingfa

    2018-04-01

    A high-temperature superconducting coated conductor can be practically applied in electric equipment due to its favorable mechanical properties and critical current (I c) performance. However, the coated conductor can easily delaminate because of its poor stress tolerance along the thickness direction. It would be interesting to investigate whether the I c of the delaminated YBa2Cu3O7-δ (YBCO) layer can be preserved. In this study, coated conductor samples manufactured through the metal organic deposition route were delaminated by liquid nitrogen immersion. Delaminated samples, including the YBCO layer and silver stabilizer, were obtained. Delamination occurred inside the YBCO layer and near the YBCO-CeO2 interface, as suggested by the results of scanning electron microscopy (SEM) and x-ray diffraction. A scanning Hall probe system was employed to measure the I c distribution of the original sample and the delaminated sample. It was found that approximately 50% of the I c can be preserved after delamination, which was verified by I c measurements using the four-probe method. Dense and crack-free morphologies of the delaminated surfaces were observed by SEM, which accounts for the I c survival of the delaminated YBCO layer. The potential application of the delaminated sample in superconducting joints was discussed based on the oxygen diffusion estimation.

  16. Solderability study of RABiTS-based YBCO coated conductors

    International Nuclear Information System (INIS)

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

    2011-01-01

    Study examines the implication of solder and flux selection in YBCO splice joints. Focus is on commercially available RABiTS-based YBCO coated conductors. Solderability varied with solder and flux for three different stabilizations tested. Resistivity of stabilizer was dominant factor in splice joint resistance. Solder materials affected splice joint resistance when solderability was poor. The solderability of commercially available YBa 2 Cu 3 O 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.

  17. State-of-the-art flux pinning in YBa2Cu3O7-δ by the creation of highly linear, segmented nanorods of Ba2(Y /Gd)(Nb/Ta)O6 together with nanoparticles of (Y /Gd)2O3 and (Y /Gd)Ba2Cu4O8

    International Nuclear Information System (INIS)

    Ercolano, G; Bianchetti, M; Wimbush, S C; Harrington, S A; MacManus-Driscoll, J L; Wang, H; Lee, J H

    2011-01-01

    Self-assembled, segmented nanorods of c-axis-aligned Ba 2 (Y /Gd)(Nb/Ta)O 6 as well as randomly distributed nanoparticles of (Y /Gd) 2 O 3 and (Y /Gd)Ba 2 Cu 4 O 8 were grown into YBa 2 Cu 3 O 7-δ (YBCO) thin films by pulsed-laser deposition. The complex pinning landscape proves to be extremely effective, particularly at higher fields where the segmented vortices yield a plateau in critical current density (J c ) with field angle around 60 0 . In 0.3 μm thick films, the J c values are higher than 1 MA cm -2 at 2.5 T (H||c axis). Owing to the combined interactions of the vortices with the different pinning centres, interesting new features are observed at high fields in the angular dependence of J c .

  18. Investigation on orientation, epitaxial growth and microstructure of a-axis-, c-axis-, (103)/(110)- and (113)-oriented YBa2Cu3O7-δ films prepared on (001), (110) and (111) SrTiO3 single crystal substrates by spray atomizing and coprecipitating laser chemical vapor deposition

    Science.gov (United States)

    Zhao, Pei; Wang, Ying; Huang, Zhi liang; Mao, Yangwu; Xu, Yuan Lai

    2015-04-01

    a-axis-, c-axis-, (103)/(110)- and (113)-oriented YBa2Cu3O7-δ (YBCO) films were pareared by spray atomizing and coprecipitating laser chemical vapor deposition. The surface of the a-axis-oriented YBCO film consisted of rectangular needle-like grains whose in-plane epitaxial growth relationship was YBCO [100] // STO [001] (YBCO [001] // STO [100]), and that of the c-axis-oriented YBCO film consisted of dense flat surface with epitaxial growth relationship of YBCO [001] // STO [001] (YBCO [100] //STO [100]). For the (103)/(110)-oriented and (113)-oriented YBCO film, they showed wedge-shaped and triangle-shaped grains, with corresponding in-plane epitaxial growth relationship of YBCO [110] // STO [110] (YBCO [010] // STO [010]) and YBCO [100] // STO [100] (YBCO [113] // STO [111], respectively.

  19. Effect of the Temperature, External Magnetic Field, and Transport Current on Electrical Properties, Vortex Structure Evolution Processes, and Phase Transitions in Subsystems of Superconducting Grains and "Weak Links" of Granular Two-Level High-Temperature Superconductor YBa2Cu3O7

    Science.gov (United States)

    Derevyanko, V. V.; Sukhareva, T. V.; Finkel', V. A.

    2018-03-01

    The temperature dependences of the resistivity of granular high-temperature superconductor YBa2Cu3O7-δ ρ( T) are measured at various transverse external magnetic fields 0 ≤ H ext ≤ 100 Oe in the temperature range from the resistivity onset temperature T ρ = 0 to the superconducting transition critical temperature T c at the transport current density from 50 to 2000 mA/cm2. The effect of the external magnetic field and transport current density on the kinetics of phase transitions in both subsystems of granular two-level HTSC ( T = T c2J, T c1g, T c ) is determined. The feasibility of the topological phase transition, i.e., the Berezinsky-Kosterlitz-Thouless transition, in the Josephson medium at T c2J < T BKT < T c1g "in transport current" is established, and its feasibility conditions are studied.

  20. LaNiO(3) Buffer Layers for High Critical Current Density YBa(2)Cu(3)O(7-delta) and Tl(2)Ba(2)CaCu(2)O(8-delta) Films

    Energy Technology Data Exchange (ETDEWEB)

    Carlson, C.M.; Parilla, P.A.; Siegal, M.P.; Ginley, D.S.; Wang, Y.-T.; Blaugher, R.D.; Price, J.C.; Overmyer, D.L.; Venturini, E.L.

    1999-08-24

    We demonstrate high critical current density superconducting films of YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} (YBCO) and Tl{sub 2}Ba{sub 2}CaCu{sub 2}O{sub 8{minus}{delta}} (Tl-2212) using LaNiO{sub 3} (LNO) buffer layers. YBCO films grown on an LNO buffer layer have only a slightly lower J{sub c} (5K, H=0) than films grown directly on a bare LaAlO{sub 3} substrate. It is noteworthy that YBCO films grown on LNO buffer layers exhibit minor microstructural disorder and enhanced flux pinning. LNO-buffered Tl-2212 samples show large reductions in J{sub c} at all temperatures and fields compared to those grown on bare LaAlO{sub 3}, correlating to both a-axis grain and nonsuperconducting phase formation. With additional optimization, LNO could be a promising buffer layer for both YBCO and Tl-based superconducting films, perhaps ideally suited for coated conductor applications.

  1. Producción y caracterización de la perovskita NdBa2SbO6 como sustrato para una película superconductora de YBa2Cu3O(7

    Directory of Open Access Journals (Sweden)

    Queeny Madueño Pinto

    2002-07-01

    Full Text Available Las propiedades de las películas superconductores de alta temperatura crítica son dependientes de parámetros cristalográficos y de la estabilidad química entre sustrato y película. Por lo tanto, con el fin de producir una perovskita cúbica compleja policristalina de NdBa2SbO6, en forma de pastilla, por medio de la técnica de reacción de estado sólido. Este material no conductor fue mezclado con el policristal superconductor YBa2CuO(7-δ en proporciones volumétricas. Se encontró un buen acoplamiento de los parámetros de red a través de la técnica experimental de difracción de rayos X. La influencia de los porcentajes de volumen del NdBa2SbO6 sobre las propiedades superconductoras del YBa2CuO(7-δ fue estudiada a través de las medidas de magnetización dc. Los resultados obtenidos muestran que el material NdBa2SbO6 es un excelente candidato a sustrato para crecer películas superconductoras de YBa2CuO(7-δ.

  2. Mode I type delamination fracture toughness of YBCO coated conductor with additional Cu layer

    International Nuclear Information System (INIS)

    Miyazato, T.; Hojo, M.; Sugano, M.; Adachi, T.; Inoue, Y.; Shikimachi, K.; Hirano, N.; Nagaya, S.

    2011-01-01

    A fracture toughness test method was developed for a YBCO coated conductor with an additional Cu layer. Mode I type tests were carried out using double cantilever beam (DCB) specimens. Delamination propagated into the YBCO layer, and sometimes reached the Ag/YBCO interface. The fracture toughness for YBCO was about 10 J/m 2 . That for Ag/YBCO interface was about 100 J/m 2 . Although interlaminar fracture at a YBa 2 Cu 3 O 7-δ (YBCO)/CeO 2 interface was reported for YBCO coated conductors, this has not yet been investigated by a fracture mechanical approach. In the present study, we developed a mode I type fracture toughness test method for a YBCO coated conductor with an additional Cu layer using double cantilever beam (DCB) specimens. Fracture mechanism was investigated by microscopic observation by a scanning electron microscope (SEM), together with composition analysis by an energy dispersive X-ray spectroscope (EDS). A pre-crack introduced at the YBCO/CeO 2 interface deviated from the interface, and propagated into the YBCO layer, and sometimes reached the Ag/YBCO interface. The fracture toughness, G R , for YBCO and the Ag/YBCO interface was evaluated to be 7-10 J/m 2 and 80-120 J/m 2 , respectively. The complex stress intensity factor ratio, K 2 /K 1 , at YBCO/CeO 2 interface was evaluated to be -0.19, and this ratio controlled the formation of microcracks in the YBCO layer. The main crack propagated into the YBCO layer accompanied with the formation of microcracks.

  3. The Effect of Sintering Oxygen Partial Pressure on a SmBiO3 Buffer Layer for Coated Conductors via Chemical Solution Deposition

    Directory of Open Access Journals (Sweden)

    Xiaolei Zhu

    2016-10-01

    Full Text Available The application of high-temperature YBa2Cu3O7−δ (YBCO superconducting material is a considerable prospect for the growing energy shortages. Here, SmBiO3 (SBO films were deposited on (100-orientated yttrium-stabilized zirconia (YSZ simple crystal substrates via the chemical solution deposition (CSD approach for coated conductors, and the effects of sintering oxygen partial pressure on SBO films were studied. The crystalline structures and surface morphologies of SBO films were characterized by X-ray diffraction (XRD, scanning electron microscopy (SEM, and atomic force microscope (AFM. The optimized growth temperature, the intensity ratios of the SBO (200 peak to the SBO (111 peak, and the crystallinities of SBO films increased with the sintering oxygen partial pressure. The SEM and AFM images displayed a smooth and well-distributed surface in the argon atmosphere. The subsequent YBCO films with superconducting transition temperatures (Tc = 89.5 K, 90.2 K, and 86.2 K and critical current densities (Jc = 0.88 MA/cm2, 1.69 MA/cm2, and 0.09 MA/cm2; 77 K, self-field were deposited to further check the qualities of the SBO layer. These results indicated that sintering oxygen partial pressure had an effect on the epitaxial growth of the SBO buffer layer and YBCO superconducting properties. The experimental results may be a usable reference for the epitaxial growth of YBCO-coated conductors and other oxides.

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

    International Nuclear Information System (INIS)

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

    2006-01-01

    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

  5. Growth of thick La2Zr2O7 buffer layers for coated conductors by polymer-assisted chemical solution deposition

    International Nuclear Information System (INIS)

    Zhang, Xin; Zhao, Yong; Xia, Yudong; Guo, Chunsheng; Cheng, C.H.; Zhang, Yong; Zhang, Han

    2015-01-01

    Highlights: • We develops a low-cost and high-efficient technology of fabricating LZO buffer layers. • Sufficient thickness LZO buffer layers have been obtained on NiW (2 0 0) alloy substrate. • Highly biaxially textured YBCO thin film has been deposited on LZO/NiW. - Abstract: La 2 Zr 2 O 7 (LZO) epitaxial films have been deposited on LaAlO 3 (LAO) (1 0 0) single-crystal surface and bi-axially textured NiW (2 0 0) alloy substrate by polymer-assisted chemical solution deposition, and afterwards studied with XRD, SEM and AFM approaches. Highly in-plane and out-of-plane oriented, dense, smooth, crack free and with a sufficient thickness (>240 nm) LZO buffer layers have been obtained on LAO (1 0 0) single-crystal surface; The films deposited on NiW (2 0 0) alloy substrate are also found with high degree in-plane and out-of-plane texturing, good density with pin-hole-free, micro-crack-free nature and a thickness of 300 nm. Highly epitaxial 500 nm thick YBa 2 Cu 3 O 7−x (YBCO) thin film exhibits the self-field critical current density (Jc) reached 1.3 MA/cm 2 at 77 K .These results demonstrate the LZO epi-films obtained with current techniques have potential to be a buffer layer for REBCO coated conductors

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

    Energy Technology Data Exchange (ETDEWEB)

    Brown, G. W. (Geoffrey W.); Hawley, M. E. (Marilyn E.); Peterson, E. J. (Eric J.); Coulter, J. Y. (James Y.); Dowden, P. C. (Paul C.); Arendt, P. N. (Paul N.); Foltyn, S. R. (Stephen R.); Mueller, F. M. (Fred M.)

    2001-01-01

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

  7. Development of 1 m HTS conductor using YBCO on textured metal substrate

    International Nuclear Information System (INIS)

    Yagi, M.; Sakamoto, H.; Mukoyama, S.; Yamamoto, K.; Amemiya, N.; Nagaya, S.; Kashima, N.; Shiohara, Y.

    2009-01-01

    We fabricated 1 m high temperature superconducting conductor (HTS conductor) using YBa 2 Cu 3 O 7-x coated conductors (YBCO tapes) on textured metal substrates, which are expected to be lower in cost than YBCO tapes using ion-beam assisted deposition. Those substrate and intermediate layers were manufactured by Furukawa Electric, and YBCO and a protective layer were applied to the intermediate layer by Chubu Electric Power. Before fabricating the conductor, a 0.1 mm thick copper tape was soldered to the YBCO tape, and 10 mm wide YBCO tape was divided into three strips by a YAG laser. To have sufficient current capacity for 1 kA, a two-layer conductor was fabricated, and its critical current (I c ) was 1976 A, but the magnetic properties of the textured metal substrates affected the increase in AC loss. In a low current region, the AC loss in this conductor was much higher than the Norris strip model, but approached the Norris strip model in the high current region because the magnetization was almost saturated. Low AC loss of 0.144 W/m at 1 kA rms was achieved even though the conductor had a small outer diameter of 20 mm and was composed of YBCO tapes with magnetic substrates.

  8. Development of all chemical solution derived Ce0.9La0.1O2−y/Gd2Zr2O7 buffer layer stack for coated conductors: influence of the post-annealing process on surface crystallinity

    International Nuclear Information System (INIS)

    Zhao, Y; Li, X-F; He, D; Andersen, N H; Grivel, J-C; Khoryushin, A; Hansen, J B

    2012-01-01

    Preparation and characterization of a biaxially textured Gd 2 Zr 2 O 7 and Ce 0.9 La 0.1 O 2−y (CLO, cap)/Gd 2 Zr 2 O 7 (GZO, barrier) buffer layer stack by the metal–organic deposition route are reported. YBa 2 Cu 3 O 7−d (YBCO) superconductor films were deposited by the pulsed-laser deposition (PLD) technique to assess the efficiency of such a novel buffer layer stack. Biaxial texture quality and morphology of the buffer layers and the YBCO superconductor films were fully characterized. The surface crystallinity of the buffer layers is studied by the electron backscatter diffraction technique. It is revealed that post-annealing GZO films in 2% H 2 in Ar is an effective way to improve the surface crystallinity. As a result, a highly textured CLO film can grow directly on the GZO film at a lower crystallization temperature. The critical current density of a YBCO PLD film is higher than 1 MA cm −2 (77 K, in self-field), demonstrating that the novel CLO/GZO stack is very promising for further development of low cost buffer layer architectures for coated conductors.

  9. In-situ YBa2Cu3O7/SrTiO3/YBa2Cu3O7 a-b plane Josephson edge junctions

    International Nuclear Information System (INIS)

    Aharoni, E.; Koren, G.; Polturak, E.; Cohen, D.; Iskevitch, E.

    1992-01-01

    YBCO/SrTiO 3 /YBCO thin film edge junctions were prepared in-situ and characterized. The epitaxial growth of SrTiO 3 on YBCO led to a sharp and well defined junction edge with a very high yield. Typical junctions showed critical currents up to 83 K, with I c ∝ (1 - T/Tc) 2 temperature dependence. Sharp Shapiro steps were observed under microwave radiation at temperatures up to 82 K. A typical diffraction pattern was found in the voltage response of the junctions to transverse magnetic field. (orig.)

  10. Observation of out-of-phase bilayer plasmons in $YBa_{2}Cu_{3}O_{7-delta}$

    NARCIS (Netherlands)

    Grüninger, M.; Marel, D. van der; Tsvetkov, A. A.; Erb, A.

    1999-01-01

    Published in: Phys. Rev. Lett. 84 (2000) 1575 Citing articles (CrossRef) citations recorded in [Science Citation Index] Abstract: The temperature dependence of the c-axis optical conductivity sigma(ømega) of optimally and overdoped YBa_2Cu_3O_x (x=6.93 and 7) is reported in the far- (FIR) and

  11. Thermodynamic study of the mixed phase in YBa_2Cu_3O_7_-_δ

    International Nuclear Information System (INIS)

    Bouquet, Frederic

    1998-01-01

    The mixed phase of type II superconductors is characterised by the existence of vortices of supercurrent that each enclose a magnetic flux quantum. Whereas the vortices order themselves in a lattice for most fields and temperatures in the mixed phase of conventional superconductors, the phase diagram for the high critical temperature superconductors is much more complex. We present here a thermodynamic study of the system of vortices for YBa_2Cu_30_7_-_δ, mainly based on specific heat experiments, but also on magnetisation measurements. To carry out the experimental work a modulated temperature calorimeter was developed, allowing us to achieve a very good resolution over a wide range of magnetic field. Our results confirm the existence of a first order thermodynamic transition in the mixed phase. We also present an original way to test the presence of a possible hysteresis associated with this transition by exploiting the oscillatory principle of our technique. The question of the existence of a low temperature high field vortex phase is discussed. Above a characteristic field B_c_r, which can reach very high values depending on the sample (up to 26 T), we find the latent heat associated with the first order transition disappears and the transition becomes continuous. By performing both magnetisation and specific heat experiments we show that Ber is related to pinning of the vortices. The existence of a third thermodynamically stable vortex phase at high field, different from the two phases at low field separated by the first order transition, does not seem to be compatible with our data. (author) [fr

  12. Cation substitution studies in YBa2Cu3O7-d structure

    International Nuclear Information System (INIS)

    Matacotta, F.C.; Segre, C.U.; Infante, C.; Ramos Arhuis, J.; Ma, B.; Ganguly, P.

    1990-04-01

    The suppression of superconductivity by the substitution of divalent cations such as Sr or Ca at Y and Ba sites in Y Ba 2 Cu 3 O 7-d and the substitution of Pr for La in LaCaBaCu 3 O 7-d has been examined by ac susceptibility and infra-red spectroscopy. The latter has been found to be particularly useful in obtaining information at the microscopic level regarding the influence of substitution at the planes and at the chains. The studies give support for the model of enhancement of superconductivity by charge fluctuations in the chains. the systematics of the changes in the electrical resistivity in La 1-x Pr x CaBaCu 3 O 7-d is examined in terms of the percolation models and the existence of a minimum sheet resistance for superconductivity. The role of the various substituents in stabilizing the structure and also in the mechanism for superconductivity is examined in terms of a model for the structure of the superconducting A m Cu n O y copper oxides on the basis of AX 3 close-packing and the uniaxial magnetic interaction model. (author). 12 refs, 6 figs

  13. Potassium substitution effects in YBa2Cu3O7- & delta superconductor

    Directory of Open Access Journals (Sweden)

    M Farbod

    2006-09-01

    Full Text Available   YBa2-xKxCu3O7-δ compound with x = 0, 0.1, 0.15, 0.2, 0.3, 0.5, 0.8, 1 was prepared. The samples were characterized by XRD, Tc, oxygen content and room temperature thermopower measurements. The results shows that by increasing the potassium, the samples go to the underdoped regime. This is due to the depletion of oxygen from the samples. By post annealing of the sample with x = 0.2 and Tc = 78 K in oxygen, the Tc increased up to 93 K which means it is possible to put back the oxygens into the structure.

  14. Dynamics of the superconducting mixed state in YBa2Cu3O7−δ ...

    Indian Academy of Sciences (India)

    The small angular width of the cusp also suggests clean interfaces between ... Dynamics of YBCO/PBCO superlattices. 6.0. 6.5. 7.0. 7.5. 8.0. 8.5. 9.0 β. 2θ ... In summary, we have synthesized high-quality superlattices of YBCO/PBCO system.

  15. Ion beam modification and analysis of thin YBa2Cu3O7 films

    International Nuclear Information System (INIS)

    Meyer, O.

    1989-04-01

    The application of ion beams for the analysis and modification of high Tc superconductors is reviewed. Ion backscattering and channeling spectroscopy is used to optimize the film composition and the epitaxial growth performance on various single crystalline substrates. The influence of radiation damage on the transport properties and on the structure of polycrystalline as well as of single crystalline thin films is presented. The irradiation induced metal to insulator phase transition is discussed in detail. Some applications including the use of ion implantation for structuring are summarized. (orig.) [de

  16. Doping and defects in YBa2Cu3O7: Results from hybrid density functional theory

    KAUST Repository

    Schwingenschlö gl, Udo; Schuster, Cosima

    2012-01-01

    7 in two prototypical configurations: Ca doped (hole doping) and O deficient (electron doping). By means of first principles calculations for fully relaxed structures, we evaluate the orbital occupations. We find that the change of the charge density

  17. Raman measurements of epitaxial YBa2Cu3O7-δ films

    International Nuclear Information System (INIS)

    Burns, G.; Dacol, F.H.; Gield, C.A.; Gupta, A.; Holtzberg, F.; Koren, G.; Laibowitz, R.; McGuire, T.R.; Segmuller, A.P.; Worthington, T.K.

    1990-01-01

    The authors report Raman measurements on good (high J c ) epitaxial YBa 2 Cu 3 O -δ (Y123) films (δ ∼ 0). The results are compared to those from oriented Y123 single crystals. The comparisons are made for superconducting δ ∼ 0 and semiconducting δ ∼ 1 materials

  18. Superconductor thin films: topotactic corrosion mechanism of YBa2Cu3O7 with water vapor

    International Nuclear Information System (INIS)

    Boerner, R.; Schoellhorn, R.; Kabius, B.; Schubert, J.

    1995-01-01

    Corrosion in high-T c superconductors (HTSC) caused by water vapor is examined. HTSC thin films prepared using the laser ablation technique are shown to lose their superconducting properties due to the topotactic formation of a new hydroxylated phase which is a result of the corrosion. The mechanism of the corrosion process, which could be important in future applications of HTSC, is discussed. (orig.)

  19. Neutron diffraction study of Fe-substituted YBa2Cu3O7

    International Nuclear Information System (INIS)

    Balagurov, A.M.; Mironova, G.M.; Pajaczkowska, A.; Piechota, J.; Shimchak, Kh.

    1989-01-01

    Neutron diffraction spectra of YBa 2 (Cu 1-x Fe x )O 7-δ (0 2 planes were determined. It is significant that the doped iron atoms occupy both of the copper site. The substitution of Fe for Cu in (2q) site is proportional to the concentration of iron in the sample. For small x there are a considerable amount of vacancies (10%) in the Cu1 site, which disappear quickly if x increases. Therefore, a joint effect of Cu substitution and the filling in vacancies by Fe occures for the Cu1 site. The amount of oxygen in samples increases with x up to 7.06 for x=0.12. Any visible effect of location of Fe at the Ba site is absent, but we can not exclude it completely. 20 refs.; 4 figs.; 1 tab

  20. Characteristics of YBa2Cu3O7 high-Tc superconductor with KCl

    Science.gov (United States)

    Yoon, Ki Hyun; Chang, Sung Sik

    1990-03-01

    The lattice parameters, microstructural change, transition temperature, and electrical properties of the YBa2-xKxCu3O7 high-Tc superconductor in the range from x=0 to x=0.25 have been investigated. The high-Tc orthorhombic phase increases with increasing KCl up to x=0.20, above which it decreases. The lattice parameters decrease with increasing KCl up to x=0.10, and then become nearly uniform. The grain size increases with increasing KCl up to x=0.20 due to its role as sintering agent. The specimens with x=0.2 have transition temperatures of 96 K and high magnetic susceptibility due to the contraction of lattice parameters a and b and the increase of orthorhombic distortion.

  1. Potassium substitution effects in YBa2Cu3O7- & delta superconductor

    OpenAIRE

    M Farbod; M Zargar Shoushtari

    2006-01-01

      YBa2-xKxCu3O7-δ compound with x = 0, 0.1, 0.15, 0.2, 0.3, 0.5, 0.8, 1 was prepared. The samples were characterized by XRD, Tc, oxygen content and room temperature thermopower measurements. The results shows that by increasing the potassium, the samples go to the underdoped regime. This is due to the depletion of oxygen from the samples. By post annealing of the sample with x = 0.2 and Tc = 78 K in oxygen, the Tc increased up to 93 K which means it is possible to put back the oxygens into th...

  2. HgO-added YBa2Cu3O7− δ superconductors

    Indian Academy of Sciences (India)

    The structural studies were carried out by neutron scattering and Rietveld analysis. The neutron scattering revealed that Hg is not incorporated in the Y-123 system and has shown optimum oxygen concentration. The significant role played by the HgO is to provide oxygen ambient through its decomposition, thus changing ...

  3. X-ray diffractometry of 10 nm thick YBa2Cu3O7-x films

    International Nuclear Information System (INIS)

    Drozdov, Yu.N.; Moldavskaya, L.D.; Parafin, A.E.

    1998-01-01

    We report on some specific features of the X-ray diffraction spectra for ultrathin c-axis-oriented YBCO films. The films were prepared by laser deposition on LaAlO 3 substrates. A DRON-4 powder diffractometer was used to analyze a structure and to measure thickness of the films. We find that this conventional technique can detect the YBCO films as thin as 5 nm. The X-ray interference fringes in the vicinity of the (005) YBCO reflections for the films from 10 to 20 nm thick were clearly visible. The oscillation period of the fringes depends on the thickness of the film and the intensity modulation yields some structural information. The I(-1)/I(+1) fringes intensity ratio was found to be sensitive to the type of atomic layer at the top and bottom of YBCO film [ru

  4. Interaction of Ag with YBa2Cu3O7-x

    International Nuclear Information System (INIS)

    Shamrai, V.F.; Efimov, Yu.V.; Frolova, T.M.; Myasnikova, E.A.; Postnikov, A.M.

    1992-01-01

    The aim of the work was to investigate the effect of Ag (0.3 to 20 mass%) on the structure, the composition and some superconducting and magnetic properties of Y-HTSC. The alloys were studied by scanning electron microscopy (in secondary and elastically backscattering electron mode) and X-ray diffraction analysis (DRON-2.0; CuKα-radiation). T c was measured by both resistive and inductive methods at T >> 77 K. The resistivity was determined by four-point technique (Ag solder) at 100 to 300 K and with 1 mA (operating current). Magnetic flux penetration was studied by a mechanical method in sound frequency interval. (orig./MM) [de

  5. Synthesis of YBa2Cu3O7-y from nitrate solutions with urea additions

    International Nuclear Information System (INIS)

    Pershin, V.I.; Naumov, V.S.; Mozhaev, A.P.; Lyashchenko, A.K.; Pobedina, A.B.; Khajlova, E.G.

    1994-01-01

    Solubility of bariun nitrate is studied in the Y(NO 3 ) 3 -Ba(NO 3 ) 2 -Cu(NO 3 )-CO(NH 2 ) 2 -H 2 O system at the ratio Y:B:Cu-1:2:3 and variable concentration of urea in the solution. Mentioned aqua-salt compositions are used in cryochemical synthesis of HTSC. Solutions of yttrium, barium and copper nitrates with urea additions were demonstrated to be recommended to improvements in the process during development of alternative synthesis from aqua-salt compositions. 15 refs., 3 figs., 2 tabs

  6. Infrared response of YBa2Cu3O7-δ films to pulsed, broadband synchrotron radiation

    International Nuclear Information System (INIS)

    Carr, G.L.; Quijada, M.; Tanner, D.B.; Etemad, S.; DeRosa, F.; Venkatesan, T.; Dutta, B.; Hemmick, D.; Xi, X.

    1990-01-01

    We report studies of a thin high T c film operating as a fast bolometric detector of infrared radiation. The film has a response of infrared radiation. The film has a response of several mV when exposed to a 1 W, 1 ns duration broadband infrared pulse. The decay after the pulse was about 4 ns. The temperature dependence of the response accurately tracked dR/dT. A thermal model, in which the film's temperature varies relative to the substrate, provides a good description of the response. We find no evidence for other (non-bolometric) response mechanisms for temperatures near or well below T c . 13 refs., 4 figs

  7. Specific heat of single crystalline YBa2Cu3O7 in 20 Tesla

    International Nuclear Information System (INIS)

    Bonjour, E.; Calemczuk, R.; Henry, J.Y.; Muller, J.; Triscone, G.; Vallier, J.C.

    1993-01-01

    The specific heat of a single crystal of YBa 2 Cu 3 0 7 is measured from 40 to 150 K in magnetic fields up to 20 Tesla applied either parallel or normal to the c axis. Adiabatic calorimetry with a scatter well below 0.1% is used. The scaling of the superconducting transitions determines the bulk anisotropy ratio 5.5±0.5. A Maki-like term is observed at intermediate temperatures. The unusual behaviour of YBa 2 Cu 3 0 7 in a field, featuring a considerable smearing of the transition and an apparently field-independent onset, may be qualitatively understood as a phenomenological consequence of the small and anisotropic value of the coherence length alone, using the relevant models of field-induced critical I-D fluctuations on one hand, and London-like regime for the mean-field part of the transition on the other hand

  8. Determination of the Electronic Density of States of YBa2Cu3O7-delta

    Science.gov (United States)

    1991-10-01

    Junod in Physical Properties of High Temperature Superconductors II, ed. by D. M. Ginsberg (World Scientific, Singapore, 1990), p. 43. 3. J. E. Gordon...1987). 12. A. Junod , et al., Physica C159, 215-225 (1989). 13. W. Reichardt, private communication. A tabulation of Fca.c(w)/Gcac( ) was provided to us...1990). 25. A. junod , et al., Physica C1621 64 , 1401 (1989). 26. V. Kresin and S. Wolf, solid State Comm. 63, 1141 (1987). 27. Steven M. Anlage, et

  9. Response of epitaxial YBa2Cu3O7 films on disorder after ion irradiation

    International Nuclear Information System (INIS)

    Saemann-Ischenko, G.; Hensel, B.; Roas, B.; Dengler, J.; Ritter, G.

    1990-01-01

    Measurements of superconducting properties, critical currents, magnetic relaxation, far infrared reflectivity (FIR) and conversion electron Mossbauer spectroscopy (CEMS) have been performed before and after ion irradiation with 25 MeV 16 O, 32 S and 173 MeV 129 Xe (in situ, ex situ or successive). The authors report essential results of this network of investigations performed for the first time on very high quality samples that were characterized to be nearly identical

  10. Disorder in YBa2Cu3O7 by entropy measurements and by rf dissipation

    International Nuclear Information System (INIS)

    Acrivos, J.V.; Inthnin, R.; Bustillo, C.; Lei, M.C.; Hellmoldt, D.

    1989-01-01

    Experiments, that characterize the disorder present in Type II superconducting ceramics, are reported Electrochemical measurements at 298>T>150 K>T c ∼ 92 K, in the cell: Cu|CuBr 2 .05 M in CH 3 OH|1:2:3|Pt and/orCu, obtain important thermochemical information, ΔH cell = 30 kJ/mole e - and ΔS cell = 212 J/K/mole e - ± 15%. This suggests that the 1:2:3 phase is disordered. The rf dissipation measurements of superconducting lamellae dispersed in a matrix give information on the effects of the static and rf fields on the mixed state

  11. Cyclotron He++ implantations effect in superconductors YBa2Cu3O7

    International Nuclear Information System (INIS)

    Santos, G.R. dos; Santos, J.C.R. dos; Morales, R.K.

    2001-01-01

    Full text: Introduction In our radiation damage research using cyclotron simulations, we are accomplishing a study of high T c superconductor under '' particles' implantation at lEN's CV-28 cyclotron. Using a special system for energy degrading, it was possible homogeneous He implantation with fluency of 7.2 to 6.0x10 16 ''.cm 2 . The preliminary results showed decreasing values for T c(onset) and T (offset) with increasing fluency. The magnetic permeability curves showed bump structures with relative position to T c(onset) varying with the fluency, suggesting phase transition as consequence of He implanted. The samples annealing in oxygen atmosphere showed evidence of restoring the superconductivity property. Some results available in the literature are conflicting to some high T c superconducting ceramics: Voronova, irradiated Nb 3 Sn with '' particles getting monotonically decreasing of T c(onset) with increasing fluency; Chrisey, irradiated films of YBaCuO with 65 MeV '' particles and fluency lower than 10 14 ''.cm - 2, and showed no changes on T c(onset) ; Maish, irradiated YBaCuO with 10 14 p.cm - 2 protons, and observed no evidence for phase transition, despite of contradicting Voronova's results. Some results of this study also differ from some authors above mentioned. However, some of them are in agreement with others authors such: Bourgault, which investigating samples of YBaCuO, using 3.5 GeV Xe ions, fluency of 10 12 ''.cm -2 , verified decreasing of the T c(onset) with fluency, and a more strong decreasing of T (offset) , also in agreement with present work. As a next step, is scheduled to perform positron lifetime measurements as function of temperature, to study the behavior of T c and its changes as consequence of Cyclotron He ++ implantation in this ceramic. Sample Preparation and Characterization - The samples were prepared from Y 2 O 3 , Ba(NO 3 ) 2 e CuO, following the conventional procedure. The mixture, in parts of 1:2:3 in Y, Ba, and Cu was dry heated in an alumina crucible, with oxygen flux of 5.6 ml.s -1 a 1223K during 20 h. After pressing, we got the samples in pellets with 350 μm thickness and density 5.8 gcm -3 . The sintering was done in the same condition of the preparing for 18 hours, when the temperature was reduced (7.7 K.min -1 ) to 673 K and brought to room temperature. In that stage we took it out pallets, with mass around 5.86 mg, and size compatible with the probe for magnetic permeability measurements (2x1x1 mm). Irradiation Procedure - The samples were fixed, with metallic indium, in a water-cooled target holders made of copper. The indium was used for proper heat dissipation and as temperature controller during irradiation. In earlier works, X-ray diffraction and magnetic permeability measurements showing no changes due to indium adsorption or absorption. The irradiations were done at lEN's CV-28 Cyclotron. The '' particle beam with 28 MeV maximum energy was periodically degraded with a rotating disk with aluminum foils of different thickness. This way, it was possible a homogeneous ion implantation into the sample thickness. The typical currents were 500 nA, corresponding to a flux of 1.64x10 12 ''.cm -2 s -1 . Results - The magnetic permeability measurements were performed using a conventional system for zero detection ('Lock-in amplifier' 124 PAR). The temperature range was from 66 to 94 K. After irradiations it was observed structure's bump like, in the permeability curve. This bumps also showed changes in relative position in the curve, followed by changes in T c(onset) . This behavior suggests that changes in T c(onset) could be attributed to a defined amount of implanted ions. This hypothesis is justified considering that each bump is the register of a starting phase transformation, as consequence of the helium concentration. Although Maish had also observed similar structure in resistivity measurements as function of temperature, in YBaCuO irradiated with 63 MeV protons' 10 14 pcm -2 , it was discarded phase transformation by X ray diffraction. Nevertheless, considering the different experimental situations, it should not be excluded the possibility of changes on the crystal structure due to presence of implanted He, giving rise to oxygen ion disorder followed by phase transformation. Conclusion - In spite of some divergences and diversity of experimental situations, all of them have in common the study of the behavior of the superconductors under radiation. Other questions are being considered, and the positron annihilation technique is being applied, trying to clarify the referred questions. Despite these questions, it is possible to make some conclusions. One of the most important is that the superconducting changed by ion implantation can be partially recovered by a proper annealing. It is expected that positron technique results could be able to clarify or better describe the behavior of T c(onset) , T (offset) , bumps structures and T c . (author)

  12. High Tc superconductivity in YBa2Cu3O7-x studied by PAC and PAS

    International Nuclear Information System (INIS)

    Zhu Shengyun; Li Anli; Zheng Shengnan; Huang Hanchen; Li Donghong; Din Honglin; Du Hongshan; Sun Hancheng

    1993-01-01

    High T c superconductivity has been investigated in YBaCuO by both perturbed angular correlation and positron annihilation spectroscopy techniques as a function of temperature from 77 to 300 K. An abrupt change has been observed in the positron lifetime and Doppler broadening and the electric field gradient and its asymmetry parameter across T c , indicating a transition of two- to one-dimensional Cu-O-Cu chain structure and a charge transfer from CuO layers to CuO chains. An anomaly of the normal state has been demonstrated around 125 K, which is attributed to the structural instability. (orig.)

  13. CDW instability near the superconducting transition in YBa2Cu3O7

    International Nuclear Information System (INIS)

    Hertel, P.; Appel, J.; Swihart, J.C.

    1989-01-01

    e-e scattering between charge carriers in the CuO 2 planes and a 1D electron system causes a temperature-dependent pair-breaking effect on the formation of a commensurate charge-density wave in the 1D system. In order to distinguish between the BCS and CDW states, the nuclear-spin relaxation rates due to magnetic and quadrupole coupling, R C /R N and Q C /Q N , and the infrared conductivity σ 1 (ω) due to singe-particle excitations are found in the presence of the T-dependent pair-breaking process

  14. Ion-beam bombardment induced texture in nickel substrates for coated high-Tc superconductors

    International Nuclear Information System (INIS)

    Wang, S S; Wu, K; Zhou, Y; Godfrey, A; Meng, J; Liu, M L; Liu, Q; Liu, W; Han, Z

    2003-01-01

    Biaxially textured metal substrates are often used for making YBa 2 Cu 3 O 7-x coated conductors with high critical current density. Generally, specific rolling and high-temperature annealing procedures are required to obtain the biaxial texture for metal substrates. Here, we report on a new method for developing strongly biaxially textured grain structure in rolled nickel tape by argon ion-beam bombardment. X-ray diffraction (XRD) θ-2θ scans have shown that a (200) diffraction peak intensity of the Ni foil processed by ion-beam structure modification (ISM) is two orders of magnitude greater than that of cold-rolled foil, while the (111) and (220) intensities are very weak. In the ISM processed Ni foils, from the rocking curve, the full width at half maximum (FWHM) value of the (200) peak has been found to be less than 5.9 deg., whilst the in-plane FWHM obtained from a pole figure analysis is just 8 deg. We discuss the possible mechanisms leading to the texture changes during ISM. (rapid communication)

  15. Study of the inhomogeneous characteristics of modified YBa_2Cu_3O_7_-_d thin films and (YBa_2Cu_3O_7_-_d /LaAlO_3)_n superlattices: growth and properties

    International Nuclear Information System (INIS)

    Thimont, Yohann

    2009-01-01

    This manuscript is devoted to the study of crystallographic and physical properties of superconductor YBCO thin films and superconductor/insulator (YBCO/LAO)_n superlattices. The first stage of this work was to optimize the YBCO thin film deposition. Elaboration of a new physical model allows us to determine a critical temperature distribution inside the films thickness. Nevertheless, no homogeneous critical temperature inside the films can be obtained. This work shows that the interface strains modify the crystallographic and physical properties. We developed a new simulation method concerning the XRD peak shape analysis which allows us to determine YBCO cell deformation profile along the c-bar axis. About superlattices, effects of thickness on the physical and structural properties have been noticed. Transmission Electron Microscopy exhibits existence of structural defects in the films. Ending, the physical model proposed in the present work provides important information regarding the magnetic interaction between two superconductor layers, which seems to limit application of these superlattices in the realization of complex electronic devices. (author) [fr

  16. Proximity effect in YBa2Cu3O7/Y0.6Pr0.4Ba2Cu3O7/YBa2Cu3O7 junctions

    International Nuclear Information System (INIS)

    Polturak, E.; Koren, G.; Cohen, D.; Aharoni, E.; Deutscher, G.

    1991-01-01

    We report critical-current measurements in all high-T c superconducting-normal-superconductor junctions using Y 0.6 Pr 0.4 Ba 2 Cu 3 O 7 (with T cN =40 K) as the normal metal. Above T cN , we find a clear exponential dependence of I c on the thickness of the barrier which is characteristic of the proximity effect. The order-parameter decay length is about 120 A for T>60 K, and it diverges as T cN is approached. We estimate that ξ 0 for this material is 80±25 A

  17. YBa2Cu3O7-δ thin films deposited by MOCVD vertical reactor with a flow guide

    International Nuclear Information System (INIS)

    Sujiono, E.H.; Negeri Makassar; Sani, R.A.; Saragi, T.; Arifin, P.; Barmawi, M.

    2001-01-01

    The effect of a flow guide in a vertical MOCVD reactor on the deposition uniformity and growth rate of thin YBCO films has been studied. Without the flow guide the growth rates are low, have a poor uniformity and the film composition is not stoichiometric. The growth rate of the films grown using a reactor with the flow guide was approximately twice that without the flow guide. Using this flow guide the growth rates were 0.4-0.7 μm/h for growth temperatures varying between 600 and 750 C, and the crystalline quality as well as the surface morphology of YBCO films on MgO substrates is improved. For films grown at temperatures above 650 C the composition of Y:Ba:Cu is 1:2:3, as confirmed by EDAX spectra. Films deposited without and with the flow guide at 700 C have critical temperatures around 85 and 88 K, respectively. The reduction in ΔT c (T c,zero -T c,onset ) also shows an improvement of the superconducting properties of YBCO thin films deposited with a flow guide. (orig.)

  18. Chemically etched edges of YBa2Cu3O7 films for interconnects, crossovers and Josephson junctions

    International Nuclear Information System (INIS)

    Poppe, U.; Faley, M.I.; Urban, K.; Soltner, H.

    1993-01-01

    To produce damage-free edges is one of the main problems during the preparation of Josephson edge-type junctions and interconnects in multilayer structures including high temperature superconductors. The inherently short and anisotropic coherence length in high temperature superconductors makes it also difficult to fabricate Josephson junctions from these materials. One promising technique which helps to overcome such problems using a nonaqueous chemical etching with a Br-ethanol solution was first presented in a recent publication. Here we report results obtained with the use of this method: test of insulation properties of PrBa 2 Cu 3 O 7 , PrBa 2 Cu 2.85 Ga 0.15 O 7 , and SrTiO 3 used for crossovers and Josephson junctions. Some features of interconnects and Josephson junctions, prepared on the basis of the chemical technique are also discussed. (orig.)

  19. Flux pinning by heavy-ion-irradiation induced linear defects in YBa2Cu3O7 epitaxial films

    International Nuclear Information System (INIS)

    Budhani, R.C.; Zhu, Y.; Suenaga, M.

    1992-01-01

    We report some transport measurements carried out to study flux pinning by heavy-ion-irradiation induced linear defects in Y 1 Ba 2 Cu 3 O 7 films. Our results show that in these in situ deposited films containing a large concentration of defects frozen-in at the time of film growth, a marginal enhancement in critical current density occurs when the density of linear defects 10 /cm 2 , and their diameter of the order of coherence length. This criterion is satisfied by Ag +21 ions. The damage due to Au +24 ions is much too severe to improve the J c

  20. High-resolution electron microscope image analysis approach for superconductor YBa2Cu3O7-x

    International Nuclear Information System (INIS)

    Xu, J.; Lu, F.; Jia, C.; Hua, Z.

    1991-01-01

    In this paper, an HREM (High-resolution electron microscope) image analysis approach has been developed. The image filtering, segmentation and particles extraction based on gray-scale mathematical morphological operations, are performed on the original HREM image. The final image is a pseudocolor image, with the background removed, relatively uniform brightness, filtered slanting elongation, regular shape for every kind of particle, and particle boundaries that no longer touch each other so that the superconducting material structure can be shown clearly

  1. Flux creep and fishtail in melt-textured and single-crystalline YBa2Cu3O7

    International Nuclear Information System (INIS)

    Kuepfer, H.; Wolf, T.; Kresse, R.; Meier-Hirmer, R.; Salama, K.; Lee, D.; Selvamanickam, V.

    1994-01-01

    Time-dependent decay of the magnetic moment and magnetization measurements were used to study pinning and flux creep in two samples with and without a j(B) maximum in nonzero field (fishtail effect). From both measurements the E(j) relation was reconstructed for B | c and the characteristic current exponent μ was obtained. At high j and low B μ values are between 1 and 4; with increasing B μ passes a maximum and approaches negative values. At low j μ is below 0.5 and not dependent on B or j. This behavior, which is qualitatively the same in both samples, is compared with proposed phase diagrams of the vortex lattice. Large μ values are correlated with the plateau of the normalized creep rate S ∼ 0.025; both observations indicate low relaxation and are found in that low B region for which j(B) has its minimum. This observation rejects a dominating influence of relaxation on the fishtail effect. 13 refs., 3 figs

  2. Superconducting epitaxial YBa2Cu3O7−δ on SrTiO3-buffered Si(001)

    Indian Academy of Sciences (India)

    2018-02-05

    Feb 5, 2018 ... K AHMADI-MAJLAN1, H ZHANG2, X SHEN3,4, M J MOGHADAM1, M CHRYSLER1, P CONLIN1,. R HENSLEY1, D SU3, J Y T WEI2 and J H NGAI1,∗. 1Department of Physics, University of Texas at Arlington, Arlington, TX 76019, USA. 2Department of Physics, University of Toronto, Toronto, ON M5S 1A7, ...

  3. Weak link behaviour in YBa2Cu3O7-δ system studied by a site percolation model

    International Nuclear Information System (INIS)

    Arulgnanam, A.; Balasubramanian, A.

    1992-01-01

    The superconductivity in the YBaCuO system can be explained in terms of the superconducting percolation of 90 K orthorhombic microdomain. Kubo et al. have studied the percolation behaviour of the 123 system and estimated the total critical oxygen occupancy P c to be 0.75 for the orthorhombic I structure using at 150x180 lattice model. In this paper, we report our work on the percolative behaviour of the 123 system, using a Monte Carlo method. We have studied the effect on P c of increasing the lattice dimension up to 500x500. For P c ≤0.60 no percolative behaviour was observed, suggesting the tetragonal phase. Few times percolation was observed for 0.60≤P≤0.65 indicating the phase transformation from tetragonal to orthorhombic. For 0.65≤P≤0.77 (or 0.230≤δ≤0.35) weak percolative behaviour was observed suggesting the formation of orthorhombic II structure, which is in good agreement with the value observed by Cava et al. For 0.77≤P≤1.0 strong percolation was exhibited indicating the formation of orthorhombic I phase. We have explained the weak link region observed for 0.60≤P≤0.77. We estimated the total critical oxygen occupancy P c =0.766 for an orthorhombic I structure for the lattice. (orig.)

  4. Sol-gel synthesis of YBa2Cu3O7-x superconductor by mixed organic-inorganic polymerization

    International Nuclear Information System (INIS)

    Valente, I.; Sanchez, C.; Henry, M.; Livage, J.

    1989-01-01

    Sol-gel processes are quite attractive methods to produce films or fibers of high Tc superconducting materials. The gel step allows a good chemical homogeneity and generally provides a rather low processing temperature. Blue sols or monolithic gels can be easily produced using mixed organic-inorganic polymerisation of molecular precursors. An aqueous solution of copper, barium acetates and yttrium nitrate is mixed with an acrylic acid solution where a radical organic polymerisation process has been initiated. After pH adjustments, the viscosity of the resulting solution can be adjusted by heating. After drying at 150 0 C and calcination above 700 0 C, the YBaCuO network is formed and superconducting properties appears above 850 0 C. Fine particles (0.1-1 μm) are obtained which can be sintered to produce a ceramic material with a particularly narrow resistive transition [fr

  5. Effect of ammonium hydroxide on preparation process of YBa2Cu3O7-x superconductor by sol gel method

    Directory of Open Access Journals (Sweden)

    H Arabi

    2006-09-01

    Full Text Available  In this paper the effect of ammonium hydroxide addition to the solution of metallic oxide on sol gel preparation process of YBCO is studied with differential thermal analysis, thermal graviometry and X-ray diffraction. Two samples with and without ammonium hydroxide. Ammonium hydroxide prevents both barium nitrate precipitate during the gel preparation and also unwanted reaction as well as increasing homogeneous product. After drying the gel, the samples heated up to 1050°C in DTA apparatus in order to find more accurate the type and the temperature of reaction during the preparation process. After the initial reactions in the samples, Y2Cu2O5 and 123 phases are created in the range of 780-840°C and then the 123 phase is strengthened at 900-950°C. As shown in X-ray data, 123 was the only phase after this range. In addition ammonium hydroxide support and increase the creation of 123 phase at lower temperature.

  6. Vortex pinning landscape in YBa2Cu3O7 films grown by hybrid liquid phase epitaxy

    International Nuclear Information System (INIS)

    Maiorov, B; Kursumovic, A; Stan, L; Zhou, H; Wang, H; Civale, L; Feenstra, R; MacManus-Driscoll, J L

    2007-01-01

    The influence of film thickness and growth rate on the vortex pinning in hybrid liquid phase epitaxy (HLPE) films was explored. Film growth rates as high as 12 nm s -1 (0.7 μm min -1 ) produced high J c films. Weak or no thickness dependence was found in films of thickness ranging from 0.4 to 3 μm. Field and angular measurements of the critical current density (J c ) and the power-law exponent (N) of the current-voltage curves were used to determine the nature of pinning. Films thinner than 0.6 μm showed a higher density of correlated defects parallel to the ab plane than thicker films. Using HLPE, it was possible to achieve very strong pinning in films ∼3 μm thick, yielding critical currents over 300 A cm -1 width at self-field, and as high as 35 A cm -1 width at μ 0 H = 3 T at T = 75.5 K. Decreasing the deposition rate allowed improving the high field performance, opening up the possibility to engineer the pinning landscape of the HLPE films

  7. Structure and properties of YBa2Cu3O7-δ superconductor doped with bulk cadmium oxide

    Directory of Open Access Journals (Sweden)

    A Echresh

    2010-09-01

    Full Text Available In this paper, the Y1-xCdxBa2Cu3O7-δ superconductor with x=0, 0.05, 0.1, 0.15, 0.2, 0.3, 0.4, 0.5 are prepared using the solid state method and the structure, electrical resistance, critical current density and critical temperature of it, have been studied. The results show that these doping do not affect so much on the structure and lattice parameters. The electrical resistance of samples increased with doping. A little amount of doping cadmium improve critical current density such that the sample x=0.1 has a maximum critical current density among the samples. The critical temperature with doping cadmium up to x=0.2 has little fluctuation and its variation can be ignored, but by increasing up to x=0.5 the critical temperature decreases gradually.

  8. Industrial metalorganic chemical vapor deposition technology for the growth of YBa2Cu3O7-∂

    International Nuclear Information System (INIS)

    Schulte, B.; Richards, B.C.; Cook, S.L.

    1997-01-01

    MOCVD is the established technology for the mass production of compound semiconductors for e.g. opto-electronic devices. To transfer the MOCVD technology for HTS films to the standard MOCVD technology used in semiconductor production two major challenges have to be solved: 1. the Ba-precursor instability and 2. the demonstration of uniform deposition of HTS films onto large area substrates. This paper presents an industrial MOCVD process solving these challenges using a new stable fluorinated Ba-precursor and a gas foil rotation trademark susceptor. On a 2 inch diameter substrate area state-of-the-art YBCO thin films were fabricated having a thickness uniformity of 1% and compositional uniformity of 2% and 5% for Y/Ba and Cu/Ba, respectively. The films show a surface morphology with low defect density ( 2 ) and excellent superconducting properties (T c (50%) > 90 K, j c (T=77 K, B=0T) > 5 x 10 6 A cm -2 ). The residual contamination by fluorine was determined by SIMS to be less than 250 ppm. This gives the strong evidence that this industrial process can be transferred to the multiwafer planetary reactors trademark for mass production. (orig.)

  9. Magnetization and flux creep in thin YBa2Cu3O7-δ films of various thickness

    International Nuclear Information System (INIS)

    Sheriff, E.; Prozorov, R.; Yeshurun, Y.; Shaulov, A.; Koren, G.; Chabaud-Villard, C.

    1997-01-01

    We report on the thickness dependence of the irreversible magnetization in superconducting Y 1 Ba 2 Cu 3 O 7-δ films of thickness 350 endash 3000 Angstrom. Our results reveal a nonmonotonous dependence of the persistent current density j on the film thickness, which is interpreted in terms of surface pinning and variations in the surface microstructure. Measurements of the time dependence of j show that under certain conditions relaxation curves of samples of different thickness cross each other, i.e., the sample with initially larger j exhibits after some time a lower j. The crossing point is shifted to shorter times as the temperature is increased. We propose a simple explanation to this effect and discuss its practical implications. Low dose heavy ion irradiation of the films has a modest effect on j and on the rate of its relaxation. copyright 1997 American Institute of Physics

  10. Study of the YBa2Cu3O-7-δ superconductor application as a low magnetic field sensor

    International Nuclear Information System (INIS)

    Oliveira, G.L; Shigue, C.Y.; Santos, C.A.M. dos; Machado, A.J.

    2000-01-01

    It has been proposed in the literature a new regime for high critical temperature superconductors labeled as thermally activated flux flow (TAFF). This regime presents a state in which vortex dynamic exhibit a ohmic behavior. The resistivity in this regime is proportional to the applied magnetic field for small current densities. Materials showing this behavior have high disordering and present semiconductor behavior in normal state with broad transition temperature. In this work is presented a systematic study of the magnetoresistance as a function of the applied magnetic field for polycrystalline samples with several thickness. Results of X ray diffraction, resistivity as a function of the temperature, I-V characteristic curves and magnetoresistance are showed. Finally is proposed a calibration curve of the magnetoresistance as a function of the magnetic field, that show the possibility of its use as magnetic field sensor. (author)

  11. A simple wet chemical method for the determination of cation stoichiometry of YBa2Cu3O7-d

    International Nuclear Information System (INIS)

    Sahasranaman, S.; Premila, M.; Sreedharan, O.M.

    1996-01-01

    A comprehensive wet chemical procedure for the rapid analysis of yttrium, barium and copper ions in dilute HNO 3 medium has been developed to facilitate a precise and accurate determination of cation non-stoichiometry in high temperature ceramic superconducting materials Y 1±x Ba 2±y Cu 3±z O 7-d . The ease of analysis for copper by electrogravimetry and of yttrium and barium by a complexometric titration of the same aliquot against complexone III using arsenazo I as the indicator under appropriate pH has been demonstrated with the help of individual standard solutions and with synthetic mixtures. (author)

  12. Millimeter-wave response and linewidth of Josephson oscillations in YBa2Cu3O7 step-edge junctions

    DEFF Research Database (Denmark)

    Divin, Yu. Ya.; Andreev, A. V.; Fischer, Gerd Michael

    1993-01-01

    by thermal fluctuations at liquid nitrogen temperatures. At lower temperatures the observed linewidth increases indicating that low-frequency fluctuations become dominant in the junction as the temperature is reduced. Due to an inhomogeneous spatial distribution of the current the step-edge junction might...

  13. Fabrication of YBa2Cu3O7-δ superconducting fibers by the sol-gel method

    International Nuclear Information System (INIS)

    Umeda, Tetsu; Kozuka, Hiromitsu; Sakka, Sumio

    1988-01-01

    High-T c superconducting oxide fibers were fabricated by the sol-gel method. An aqueous solution of metal acetates was concentrated to form a viscous sol, from which gel fibers were spun. The gel fibers, 5 to 1,000 μm in diameter, were converted to ceramic fibers by heating to 900 degree C. The fired fibers (T c (onset) of 94 K and T c (end) of 62.2 K) were rough and had porous microstructures

  14. High critical current YBa2Cu3O7 artificial joints using Ag foils as welding agent

    International Nuclear Information System (INIS)

    Iliescu, S; Granados, X; Bartolome, E; Sena, S; Carrilllo, A E; Puig, T; Obradors, X; Evetts, J E

    2004-01-01

    A new high quality joining technique of melt processed YBCO has been developed based on interfacial melting induced by a metallic silver foil inserted between two single domain YBCO tiles. This simple technique allows joining large monoliths to form the complex-shaped pieces required for many power applications. Hall probe magnetic flux profile analysis under magnetic field and high field magnetoresistance measurements demonstrate that the superconducting behaviour of the joint is indistinguishable from the bulk

  15. Anisotropy of creep for vortex motion along twin planes in YBa2Cu3O7-x single crystals

    International Nuclear Information System (INIS)

    Bondarenko, A.V.; Prodan, A.A.; Obolenskij, M.A.; Vovk, R.V.; Arouri, T.R.

    2001-01-01

    Anisotropy of magnetic flux creep was investigated for the flux motion along the twin boundaries. It is shown that in relatively low magnetic fields the velocity of vortex creep does not depend on magnetic field and angle α identical H, ab. It is found that the differential resistivity ρ identical dE/dJ at high transport currents tends to saturation and its value is close to the viscous friction resistivity in the Bardeen-Stephen model. In low magnetic fields for the field applied in the vicinity of the ab-plane of the crystal a lock-in transition of vortices between the superconducting CuO layers was observed

  16. Evolution of the vortex phase diagram in YBa2Cu3O7-δ with random point disorder

    International Nuclear Information System (INIS)

    Paulius, L. M.; Kwok, W.-K.; Olsson, R. J.; Petrean, A. M.; Tobos, V.; Fendrich, J. A.; Crabtree, G. W.; Burns, C. A.; Ferguson, S.

    2000-01-01

    We demonstrate the gradual evolution of the first-order vortex melting transition into a continuous transition with the systematic addition of point disorder induced by proton irradiation. The evolution occurs via the decrease of the upper critical point and the increase of the lower critical point. The collapse of the first-order melting transition occurs when the two critical points merge. We compare these results with the effects of electron irradiation on the first-order transition. (c) 2000 The American Physical Society

  17. Effects of the layered structure of YBa2Cu3O7-δ on the superconducting fluctuations

    International Nuclear Information System (INIS)

    Baraduc, C.

    1994-06-01

    The study mainly addresses Gaussian fluctuations, with the Lawrence-Doniach model used as a framework for describing the coupled superconducting planes. The fluctuations in zero magnetic field and especially the conductivity fluctuations are studied theoretically and experimentally. It is shown that the conductivity does not follow the same mechanism when current flows along the planes or perpendicularly to them. When fluctuations are confined in each plane, a two-dimensional mechanism is observed for the parallel conductivity whereas a zero-dimensional one controls the perpendicular conductivity, which can be understood as a hopping process. Fluctuations under magnetic field, applied in the perpendicular direction, are also examined. Different scaling laws are proposed and compared for experimental magnetization data. It is shown that the 2D-3D cross-over, characterizing a layered structure, still remains under field. The observation of a crossing point in the magnetic curves raises the problem of vortex fluctuations even in this moderately anisotropic compound. 48 figs., 86 refs

  18. High Critical Current Coated Conductors

    Energy Technology Data Exchange (ETDEWEB)

    Paranthaman, M. P.; Selvamanickam, V. (SuperPower, Inc.)

    2011-12-27

    One of the important critical needs that came out of the DOE’s coated conductor workshop was to develop a high throughput and economic deposition process for YBCO. Metal-organic chemical vapor deposition (MOCVD) technique, the most critical steps in high technical micro fabrications, has been widely employed in semiconductor industry for various thin film growth. SuperPower has demonstrated that (Y,Gd)BCO films can be deposited rapid with world record performance. In addition to high critical current density with increased film thickness, flux pinning properties of REBCO films needs to be improved to meet the DOE requirements for various electric-power equipments. We have shown that doping with Zr can result in BZO nanocolumns, but at substantially reduced deposition rate. The primary purpose of this subtask is to develop high current density MOCVD-REBCO coated conductors based on the ion-beam assisted (IBAD)-MgO deposition process. Another purpose of this subtask is to investigate HTS conductor design optimization (maximize Je) with emphasis on stability and protection issues, and ac loss for REBCO coated conductors.

  19. An evaluation of phase separated, self-assembled LaMnO3-MgO nanocomposite films directly on IBAD-MgO as buffer layers for flux pinning enhancements in YBa2YCu3O7-& coated conductors

    Energy Technology Data Exchange (ETDEWEB)

    Polat, Ozgur [ORNL; Aytug, Tolga [ORNL; Paranthaman, Mariappan Parans [ORNL; Leonard, Keith J [ORNL; Lupini, Andrew R [ORNL; Pennycook, Stephen J [ORNL; Meyer III, Harry M [ORNL; Kim, Kyunghoon [ORNL; Qiu, Xiaofeng [ORNL; Cook, Sylvester W [ORNL; Thompson, James R [ORNL; Christen, David K [ORNL; Goyal, Amit [ORNL; Selvamanickam, V. [SuperPower Incorporated, Schenectady, New York; Xiong, X. [SuperPower Incorporated, Schenectady, New York

    2010-01-01

    Technological applications of high temperature superconductors (HTS) require high critical current density, Jc, under operation at high magnetic field strengths. This requires effective flux pinning by introducing artificial defects through creative processing. In this work, we evaluated the feasibility of mixed-phase LaMnO3:MgO (LMO:MgO) films as a potential cap buffer layer for the epitaxial growth and enhanced performance of YBa2Cu3O7-d (YBCO) films. Such composite films were sputter deposited directly on IBAD-MgO templates (with no additional homo-epitaxial MgO layer) and revealed the formation of two phase-separated, but at the same time vertically aligned, self-assembled composite nanostructures that extend throughout the entire thickness of the film. The YBCO coatings deposited on these nanostructured cap layers showed correlated c-axis pinning and improved in-field Jc performance compared to those of YBCO films fabricated on standard LMO buffers. Microstructural characterization revealed additional extended disorder in the YBCO matrix. The present results demonstrate the feasibility of novel and potentially practical approaches in the pursuit of more efficient, economical, and high performance superconducting devices.

  20. Coated Conductors under Tensile Stress

    International Nuclear Information System (INIS)

    Antonevici, Anca; Villaume, Alain; Villard, Catherine; Sulpice, Andre; Maron, Pierre Brosse; Bourgault, Daniel; Porcar, Laureline

    2006-01-01

    Critical current dependence versus strain is obtained for in-situ axial stress experiments on ISD YBCO and DyBCO coated conductors. The drop of critical current due to the apparition of first cracks in the superconducting ceramics is related to the passage in the plastic region of the substrate for a strain of about 0.3% and a stress higher then 500MPa. The superconductivity is preserved between the cracks

  1. Processing of flexible high-Tc superconducting wires

    International Nuclear Information System (INIS)

    Lee, B.I.; Modi, V.

    1989-01-01

    Wires superconducting at temperatures above 77 K are produced by using YBa 2 Cu 3 O 7 materials. Flexibility was obtained by support from prefabricated fibers or a metallic coating on the extruded YBa 2 Cu 3 O 7 wires. The microstructure, the T c and the critical current densities of the wires were determined. Processing variables and steps are described

  2. Study on advanced Ce0.9La0.1O2/Gd2Zr2O7 buffer layers architecture towards all chemical solution processed coated conductors

    DEFF Research Database (Denmark)

    Yue, Zhao; Ma, L.; Wu, W.

    2015-01-01

    2Zr2O7 buffer layer stack and the 200 nm thick YBa2Cu3O7 (YBCO) superconducting layer were sequentially deposited on textured NiW substrates using metal-organic deposition routes. The surface texture of the Gd2Zr2O7 barrier layer deteriorates when the film thickness increases to 80 nm, although...

  3. Investigation of the influence of different preparation conditions on the effective activation energy in YBa2Cu3O7-x

    International Nuclear Information System (INIS)

    Reissner, M.; Ambrosch, R.; Steiner, W.; Stroh, R.; Schmid, W.; Wruss, W.

    1991-01-01

    The investigation of the relaxation behaviour in ceramics can give hints for preparation conditions to optimize pinning and therefore critical current density. The aim of the present paper is to contribute to the problems concerning this point. The influence of different preparation conditions on the activation energy was investigated on different YBCO samples with small grains by means of measurements of the relaxation of the magnetization. The determination of the critical current density (J c ) from magnetization measurements has the advantage that the contribution of the grains can be separated from the one of the weak links (which is not possible in direct measurements of J c ), but has the disadvantage to need simplifying models and to know the shape of the grains and can therefore lead to large uncertainties in J c . To test the significance of the magnetically determined critical current densities a comparison of the dependence of J c on the preparation conditions with the one of the effective activation energy will be given. (orig./BHO)

  4. Correlation of ''twins'' observed by optical microscopy and transmission electron microscopy in YBa2Cu3O7/sub -//sub x/ superconductors

    International Nuclear Information System (INIS)

    Hoff, H.A.; Singh, A.K.; Pande, C.S.

    1988-01-01

    By using transmission electron microscopy and optical microscopy on the same specimens, the patterns of light- and dark-contrast lines seen in reflected polarized light were shown to be an interference pattern due to the variable spacing of suboptical microtwins. These microtwins are mostly [110] reflection twins. The [110] twinning was observed to be cyclic and occasionally pseudotetragonal because of the progressive cycling of contact twin domains. Within a domain, and occasionally in a whole grain, the [110] reflection twins occurred as polysynthetic lamellae. The morphology of the domain structure can be explained from the theory of martensitic transformation

  5. Analyse de l'état mécanique et microstructural de films minces supraconducteurs YBa_2 Cu_3O_7 par diffraction des rayons X

    Science.gov (United States)

    Auzary, S.; Badawi, K. F.; Bimbault, L.; Rabier, J.; Gaboriaud, R. J.; Goudeau, Ph.

    1997-01-01

    Mechanical and microstructural analysis in a 100nm thin film is presented in this study. Using X-ray diffraction with a tensorial approach, we have determined stresses, strains, stress-free lattice parameters, microdistorsions and diffracting coherent domains size. Stress-free lattice parameters are higher than the bulk values. A high value of stresses is explained as a combination of coherent stresses, thermal stresses and intrinsic ones. Diffraction peaks line profiles analysis suggests grain boundaries presence as well as high lattice elastic microdistorsions. Cette étude présente une analyse de l'état mécanique et microstructurale dans un film mince de 100nm d'épaisseur d'YBCO déposé sur un substrat de MgO. En utilisant la diffraction des rayons X couplée à une approche tensorielle, nous avons déterminé les déformations, les contraintes, les paramètres libres de contraintes, les microdistorsions élastiques ainsi que la taille des domaines cohérents de diffraction. Les paramètres libres de contrainte sont supérieurs à ceux du massif. Une valeur élevée des contraintes est expliquée à partir des contraintes de cohérence, des contraintes thermiques et intrinsèques. L'analyse des profils des pics de diffraction suggère la présence de sous-joints et de distorsions élastiques élevées au niveau des mailles cristallographiques.

  6. Effect of temperature gradient in the solution on spiral growth of YBa2Cu3O7-x bulk single crystals

    International Nuclear Information System (INIS)

    Kanamori, Y.; Shiohara, Y.

    1996-01-01

    Bulk single crystals of Y123 are required to clarify the superconductivity phenomena and develop electronic devices using unique superconductive properties. Only the Solute Rich Liquid endash Crystal Pulling (SRL-CP) method has succeeded in continuous growth of the Y123 single crystal. In this paper, we investigated the growth of Y123 single crystals under different temperature gradients in the solution in order to understand the growth mechanism of Y123. It was revealed that Y123 single crystals grow with a spiral growth mode, which is in good agreement with the BCF theory. copyright 1996 Materials Research Society

  7. The effect of correlated and point defects on the vortex lattice melting transition in single-crystal YBa2Cu3O7

    International Nuclear Information System (INIS)

    Kwok, W.K.; Fendrich, J.; Fleshler, S.; Welp, U.; Downey, J.; Crabtree, G.W.; Giapintzakis, J.

    1994-01-01

    The vortex melting transition T m in several untwinned and twinned crystals is measured resistively in fields up to 8T. A Lindemann criterion for vortex lattice melting is obtained in addition to a sharp hysteresis in the magnetoresistance at B m supporting a first-order phase transition. The anisotropy of twin boundary pinning and its reduction of the 'kink' in ρ(T) associated with the first-order melting transition is discussed in samples with very dilute twin boundaries. We also report on the direct suppression of the the melting transition by intrinsic pinning for H parallel ab and by electron-irradiation-induced point defects. (orig.)

  8. Reproducible fabrication and characterization of YBa2Cu3O7 Josephson junctions and SQUIDs on SrTiO3 bi-crystal substrates

    International Nuclear Information System (INIS)

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

    1993-01-01

    The fabrication of Josephson junctions and SQUIDs using ceramic high T c superconductors continues to be a subject of great interest and activity. In the case of the YBCO family of superconductors, most of the research effort has been concentrated on the grain boundary junctions. This type of junction can be fabricated in a controlled way by a variety of approaches, such as the bi-crystal technique, the bi-epitaxial technique or the step-edge technique. From a fabrication point of view, the bi-crystal technique is by far the simplest of the three. The availability of (100) SrTiO 3 bi-crystals on a commercial basis has lead to the possibility of making Josephson junctions by a simple process involving only one deposition and one patterning step. Reproducibility of the junction parameters between junctions on the same chip is a key point for electronic applications of Josephson junctions requiring a large amount of Josephson junctions working at the same time, as for example in the voltage standard. Another key point is the uniformity of the barrier, i.e. the extent to which the junction behaves as an ideal SIS junction. In this work junction uniformity has been studied by Frauenhofer diffraction patterns. The Josephson junctions have also been used in the fabrication of dc SQUIDs. In this work we have tried to optimize the magnitude of the voltage modulation from the SQUID by varying the design parameters. The SQUIDs have been characterized in terms of I c , R n , voltage modulation and noise properties. (orig.)

  9. Vibrational spectra and lattice instabilities in the high-T/sub c/ superconductors YBa2Cu3O7 and GdBa2Cu3O7

    International Nuclear Information System (INIS)

    Bozovic, I.; Mitzi, D.; Beasley, M.

    1987-01-01

    The exceptionally high T/sub c/ of layered cuprates was proposed recently as originating from electronically driven structural instabilities. We have studied the infrared and Raman spectra of YBa 2 Cu 3 O/sub 7-//sub δ/ and GdBa 2 Cu 3 O/sub 7-//sub δ/ over a broad range of temperatures, from 10 to 300 K. We observed neither mode softening nor any other spectroscopic signature of lattice instabilities

  10. Growth-induced strong pinning sites in laser ablated YBa2Cu3O7-δ films with a non-random distribution

    International Nuclear Information System (INIS)

    Huijbregtse, J.M.; Klaassen, F.C.; Geest, R.C.F. van der; Dam, B.; Griessen, R.

    1999-01-01

    Recently, the authors showed that natural linear defects are the origin of the high critical currents in laser ablated YGBa 2 Cu 3 O 7-δ films. Combining wet-chemical etching and Atomic Force Microscopy, they find that these dislocations are created by island coalescence during growth. Consequently, the defect density can be reproducibly varied by manipulating the density of growth islands, which in turn depends on the substrate temperature. Interestingly, the radial defect distribution function approaches zero at small distances, indicating short range order. Therefore, they are now able to study vortex matter in films with a tailored non-random distribution of natural strong pinning sites

  11. Isotropic and anisotropic pinning in TFA-grown YBa2Cu3O7−x films with BaZrO3 nanoparticles

    International Nuclear Information System (INIS)

    Palau, A; Llordés, A; Puig, T; Obradors, X; Bartolomé, E

    2011-01-01

    YBCO films grown by the trifluoroacetate (TFA) method with increasing number of BaZrO 3 (BZO) nanoparticles have been measured by in-field angular transport measurements to investigate changes in the pinning landscape. The isotropic and anisotropic contributions to the critical current density, J c (H), with the magnetic field applied in H||c and H||ab orientation have been determined, allowing us to characterize the population of isotropic and correlated defects along the c axis and ab planes. First, the influence of the YBCO oxygenation process on the formation of different sorts of anisotropic defects in standard films is demonstrated. Next, we show that the addition of non-coherent BZO nanoparticles to the YBCO matrix produces an expansion of the single-vortex pinning regime toward higher fields, due to the presence of isotropic pinning centers. Moreover, by increasing the amount of isotropic defects in the BZO nanocomposites it is possible to extend the region dominated by strong isotropic pinning centers to large magnetic fields and thus enhance the irreversibility line.

  12. Strong field-matching effects in superconducting YBa2Cu3O7-δ films with vortex energy landscapes engineered via masked ion irradiation

    Science.gov (United States)

    Swiecicki, I.; Ulysse, C.; Wolf, T.; Bernard, R.; Bergeal, N.; Briatico, J.; Faini, G.; Lesueur, J.; Villegas, Javier E.

    2012-06-01

    We have developed a masked ion irradiation technique to engineer the energy landscape for vortices in oxide superconductors. This approach associates the possibility to design the landscape geometry at the nanoscale with the unique capability to adjust the depth of the energy wells for vortices. This enabled us to unveil the key role of vortex channeling in modulating the amplitude of the field matching effects with the artificial energy landscape, and to make the latter govern flux dynamics over an unusually wide range of temperatures and applied fields for high-temperature superconducting films.

  13. The effect of correlated and point defects on the vortex lattice melting transition in single crystal YBa2Cu3O7

    International Nuclear Information System (INIS)

    Kwok, W.K.; Fleshler, S.; Welp, U.; Downey, J.; Crabtree, G.W.; Fendrich, J. Giapintzakis, J.

    1993-08-01

    The vortex melting transition T m in several untwinned and twinned crystals measured resistively in fields up to 8 Tesla. A Lindemann criterion for vortex lattice melting is obtained in addition to a sharp hysteresis in the magnetoresistance at B m supporting a first order phase transition. The anisotropy of twin boundary pinning and its reduction of the ''kink'' in ρ(T) associated with the first order melting transition is discussed in samples with very dilute twin boundaries. We also report on direct suppression of melting transition by intrinsic pinning for H parallel ab and by electron-irradiation-induced point defects

  14. YBa2Cu3O7–La0.67Sr0.33MnO3 trilayers

    Indian Academy of Sciences (India)

    the near bulk value (~350 K) in films thicker than 200 Å, while thinner films show a slight drop in ... 1000 Oe field-cooled Ms(T) measurements (shown in figure 1) to the Bloch relation .... The solid lines in the inset are only guides to the eyes.

  15. Effects of Ca doping and O deficiency on the charge distribution in the vicinity of a 45° [001] grain boundary in YBa2Cu3O7

    KAUST Repository

    Schwingenschlö gl, Udo; Schuster, Cosima B.

    2012-01-01

    The charge redistribution at grain boundaries is critical for the applicability of high-T c superconductors in electronic devices, because it determines the transport across the material. We investigate the charge transfer and the alterations

  16. d+s wave superconductivity: analysis of the electronic Raman data of YBa2Cu3O7-δ and other cuprates

    International Nuclear Information System (INIS)

    Nemetschek, R.; Hackl, R.; Opel, M.; Philipp, R.; Beal-Monod, M.T.; Bieri, J.B.; Maki, K.; Erb, A.; Walker, E.

    1998-01-01

    After briefly recalling the d+s model valid for some anisotropic high T c superconductors, we present a theory of electronic Raman spectra in that model and then compare it with new experimental data obtained for an overdoped Y123 single crystal. The d+s model appears to describe satisfactorily the experimental results, indicating a possible doping dependence of the mixing ratio. We note that the Raman spectrum of the overdoped Bi2212 could also be accounted for by the d+s superconductivity model. The case of Hg1212 (or Hg1223) is reexamined. It appears that the spontaneous breakdown of d-wave symmetry may be rather universal in high T c cuprates. (orig.)

  17. Investigation of the properties of carbon-base nanostructures doped YBa_2Cu_3O_7_−_δ high temperature superconductor

    International Nuclear Information System (INIS)

    Dadras, Sedigheh; Ghavamipour, Mahshid

    2016-01-01

    In this research, we have investigated the effects of three samples of carbon-base nanostructures (carbon nanoparticles, carbon nanotubes and silicon carbide nanoparticles) doping on the properties of Y_1Ba_2Cu_3O_7_−_δ (YBCO) high temperature superconductor. The pure and doped YBCO samples were synthesized by sol–gel method and characterized by resistivity versus temperature (ρ–T), current versus voltage (I–V), through X-ray diffraction (XRD) and scanning electron microscope (SEM) analysis. The results confirmed that for all the samples, the orthorhombic phase of YBCO compound is formed. We found that the pinning energy and critical current density of samples increase by adding carbon nanostructures to YBCO compound. Also critical temperature is improved by adding carbon nanotubes to YBCO compound, while it does not change much for carbon and silicon carbide nanoparticles doped compounds. Furthermore, the samples were characterized by UV–vis spectroscopy in 300 K and the band gap of the samples was determined. We found that the carbon nanotubes doping decreases YBCO band gap in normal state from 1.90 eV to 1.68 eV, while carbon and SiC nanoparticles doping increases it to 2.20 and 3.37 eV respectively.

  18. Electronic structures of the YBa2Cu3O7-x surface and its modification by sputtering and adatoms of Ti and Cu

    Science.gov (United States)

    Meyer, H. M., III; Hill, D. M.; Wagener, T. J.; Gao, Y.; Weaver, J. H.; Capone, D. W., II; Goretta, K. C.

    1988-10-01

    We present x-ray and inverse photoemission results for fractured surfaces of YBa2Cu3O6.9 before and after surface modification by Ar ion bombardment and the deposition of adatoms of Ti and Cu. Representative results are compared for samples prepared in three different ways. Two of the sample types exhibit substantial emission from grain-boundary phases because of both intergranular and transgranular fracture; they produce results that are very similar to those presented thus far in the literature. A third type was nearly free of contamination and clearly showed spectral features characteristic of the superconductor. Comparison of these nearly contamination-free valence-band results to those for clean La1.85Sr0.15CuO4 shows remarkably similar x-ray photoemission spectroscopy densities of states, with subtle differences near the Fermi level and at 3 eV. Inverse photoemission results show the top of the Cu-O hybrid orbitals to be 2 eV above EF and the empty states of Y and Ba at higher energy. Comparison with one-electron densities of states shows reasonable agreement, but there are large differences within the set of calculated results, and it is unclear from the valence bands alone how to account for final-state Cu d-d Coulomb correlation effects (satellite features show these effects very clearly). Argon sputtering for both types of samples shows destruction of the superconductor, with differences that can be related to sample surface quality. The deposition of adatoms of Ti and Cu results in reaction associated with oxygen withdrawal from the near-surface region. Studies of the Cu 2p3/2 line shape show that the deposition of as little as ~1 monolayer equivalent of Ti or Cu reduces the formal Cu2+ emission within the probed volume (30-50 Å deep). Core-level analysis shows that this chemical reduction of Cu is accompanied by crystal-structure modifications as well. Studies of Cu adatom interactions reveal the progression from Cu2+ to Cu1+ and ultimately, to Cu metal as the overlayer thickens (Cu 2p2/3 binding energy 932.5 eV for Cu metal, 933.1 eV for Cu1+, and 932.8 eV for the superconductor). Valence-band results during interface formation show the disappearance of emission near the Fermi level, consistent with the loss of Cu2+-O covalent bonds of the superconductor.

  19. Conductivity peak, relaxation dynamics, and superconducting gap of YBa2Cu3O7 studied by terahertz and femtosecond optical spectroscopies

    International Nuclear Information System (INIS)

    Frenkel, A.; Gao, F.; Liu, Y.; Whitaker, J.F.; Uher, C.; Hou, S.Y.; Phillips, J.M.

    1996-01-01

    Recent measurements at microwave, terahertz (THz), and infrared frequencies have revealed a peak in σ 1 below T c . Based on our THz measurements, which were performed on high quality, single crystal films of YBCO (900 and 500 A), we have found that σ 1 features a peak which increases in amplitude and shifts to lower temperatures as frequency changes from 1.2 to 0.4 THz. Although the quasiparticle relaxation time extracted from these results using the two-fluid Drude model exhibits an enhancement below T c , the analysis may not be adequate to account for the strong frequency dependence of the conductivity peak by the competition between the drop in scattering rate and the decreasing normal fluid density with temperature. On the contrary, we were able to account for the frequency dependent σ 1 by fitting with Mattis-Bardeen theory (modified to include scattering) using a slower average rate of increase of the anisotropic gap than for the BCS case as temperature decreases below T c . This is consistent with the higher normal fluid density (higher than Gorter-Casimir values) from the two-fluid model interpretation of our THz results. Thus, we have found evidence of BCS coherence factors in a high-T c superconductor with a slower than BCS gap increase below T c . We have discussed the role of coherence factors to account for the presence of the conductivity peak and the absence of the peak in NMR relaxation rate. Furthermore, we have presented a model for the quasiparticle relaxation time measured by the femtosecond pump-probe spectroscopy. This model allowed us to find a fit to the temperature-dependent energy gap function which is also consistent with the slower gap increase below T c

  20. Raman spectroscopic investigation of superconducting YBa2Cu3O7/sub -//sub x/, semiconducting YBa2Cu3O6/sub +//sub x/, and possible impurity phases

    International Nuclear Information System (INIS)

    Mascarenhas, A.; Geller, S.; Xu, L.C.; Katayama-Yoshida, H.; Pankove, J.I.; Deb, S.K.

    1988-01-01

    A Raman spectroscopic investigation of specimens of superconducting YBa 2 Cu 3 O/sub 7-//sub x/ and of the possible impurity phases YBa 2 Cu 3 O/sub 6+//sub x/ (semiconductor), Y 2 BaCuO 5 , Y 2 Cu 2 O 5 , BaCuO 2 , CuO, Y 2 O 3 , and BaCO 3 indicates that in the range 100--700 cm -1 , there are six characteristic lines belonging to the superconductor. At 13 K, these lines are at 150, 338, 441, 507, 590, and 644 cm -1 . Comparison of the Raman spectra of the superconductor and the semiconductor indicates a mode stiffening of the pair at 338 and 441 cm -1 , but a mode softening of the pair at 507 and 590 cm -1 . A factor group analysis leads to a tentative assignment of the Raman and infrared allowed modes