1,721,071 research outputs found
Ionic liquid gating of ultra-thin YBa2Cu3O7- x films
No full textIn this paper, we present a detailed investigation of the self-field transport properties of an ionic liquid gated ultra-thin YBa2Cu3O7- x (YBCO) film. From the high temperature dynamic of the resistivity (>220 K), different scenarios pertaining to the interaction between the liquid and the thin film are proposed. From the low temperature evolution of Jc and Tc, a comparison between the behavior of our system and the standard properties of YBCO is drawn. © 2016 Author(s)
Investigation of Soldered REBCO Tape-Copper Joints for Superconducting Applications
No full textIn the growing field of higherature superconductor (HTS) applications, soldered tape-copper joints are of significant importance. This is because the resistance of the joint often plays a decisive role in the design of a superconducting device, such as current leads or current terminations of cables. A common requirement to the joint is as-low-as-possible resistance and reliable reproducibility, which is crucial for achieving a homogeneous current distribution being independent within each HTS tape placed in a superconducting device. From previous studies, it is known that resistance of HTS tape-copper joint can vary for different tapes and solders. This resistance can be considered as a sum of several contributions: REBCO-layer-copper-laminating-layer interface resistance in HTS tape, copper-laminating-layer-solder and solder-copper interface resistances, and solder and copper resistances. Here, we present current status of investigations on tape-copper joints and trials to estimate different contributions in their resistance value. © 2002-2011 IEEE
The Vortex Path Model Analysis of the Field Angle Dependence of the Critical Current Density in Nanocomposite YBa2Cu3O7-x – BaZrO3 Films Obtained by Low Fluorine Chemical Solution Deposition
No full textIn the present paper, we analyze the role of in situ grown BaZrO3 (BZO) inclusions in YBa2Cu3O7-x (YBCO) thin films prepared by chemical solution deposition using a low fluorine coating solution, on the field angle dependence of the critical current density, Jc(), data using the vortex path model. In order to form a coherent picture on the BZO doping influence on the pinning properties of the YBCO matrix, detailed structural analyses performed by X-ray diffraction techniques and microstructural evaluation by transmission electron microscopy are also presented. The evaluation of different contributions to the overall, Jc, permitted us to prove the effectiveness of the BZO inclusions acting as isotropic pinning centers, reflected in a uniform component of high relative value with respect to other components. For the studied 10 mol % BZO doping concentration, a threefold increase in the critical current density, Jc, of the YBCO host is measured, in self-field at 77 K, corresponding to a value of Jc=2.9MA/cm2, whereas a factor 10 is measured at 1 T (Jc=0.35 MA/cm2)
Anisotropy and directional pinning in YBa2Cu3O 7-x with BaZrO3 nanorods
No full textMeasurements of anisotropic transport properties (dc and high-frequency regime) of driven vortex matter in YBa2Cu3O 7-x with elongated strong-pinning sites (c-axis aligned, self-assembled BaZrO3 nanorods) are used to demonstrate that the effective-mass angular scaling takes place only in intrinsic physical quantities (flux-flow resistivity), and not in pinning-related Labusch parameter and critical currents. Comparison of the dynamics at different time scales shows evidence for a transition of the vortex matter toward a Mott phase, driven by the presence of nanorods. The strong pinning in dc arises partially from a dynamic effect. © 2013 Author(s)
Directional pinning and anisotropy in YBa2Cu3O 7-x with BaZrO3 nanorods: Intrinsic and nanorods-induced anisotropy
No full textWe present a study of the anisotropic vortex parameters as obtained from measurements of the microwave complex resistivity in the vortex state with a tilted applied magnetic field in YBa2Cu3O7-x thin films with BaZrO3 nanorods. We present the angular dependence of the vortex viscosity η, the pinning constant kp and the upper limit for the creep factor χM. We show that the directional effect of the nanorods is absent in η, which is dictated by the mass anisotropy γ. By contrast, pinning-mediated properties are strongly affected by the nanorods. It is significant that the pinning and creep affected by the nanorods is detectable also at our very high operating frequency, which implies very short-range displacements of the vortices from their equilibrium position. © 2014 Elsevier B.V. All rights reserved
Surrogate modelling to minimize contact resistance of HTS ReBCO terminations
No full textRecent advances in HTS ReBCO tapes processing and performances have opened attractive perspectives for applications. For the development of HTS-based technology there are several technological challenges to be addressed such as cable terminations. In this contribution, the effect of load, temperature and joint process time on solder joint process of SuperPower SCS4050 tapes with the Pb-Sn solder paste, was investigated using a surrogate model. The prediction of contact resistance RSj = Rj × S (S is the joint contact area) as a function of manufacturing parameters is a complex and time-consuming multi-physical problem involving a coupling of mechanical, thermal and electrical equations. Therefore, a surrogate model was implemented to the aim of predicting the effects of parameters on the joint resistance, without developing a computationally intensive multi-physical model. Taking full advantage of the reduced number of tests performed, the surrogate model demonstrated to be useful to supply significant information for tests, allowing to focus directly on the most promising sets of parameters, avoiding an expensive trial-and-error experimental campaign. © 2014 IEEE
Measurement of Vortex Pinning in YBCO and YBCO/BZO Coated Conductors Using a Microwave Technique
No full textIn order to study the effect of pinning in coated conductors, we have used pulsed laser ablation to grow YBa2Cu3O7-x (YBCO) and YBa2Cu3O7-x/BaZrO3 (YBCO/BZO) films on metallic templates. Despite the complexity of the structure, after the optimization of the deposition procedure, the YBCO/BZO showed only a moderate reduction of Tc with respect to the pure YBCO sample. We use a very high frequency (∼47.7 GHz) dielectric resonator technique in order to induce very short distance vortex shaking, thus probing the steepness of the potential well. We report on measurements of the microwave response of the superconducting structures in terms of the quality factor Q and the frequency resonance ν0 as a function of a moderate dc magnetic field H, at different temperatures T. To keep as much contact as possible to the raw data (Q and ν0), in agreement with a generalized model for vortex dynamics, we determine the pinning parameter r and the upper limit for the creep factor χM. Based on the field dependence of the pinning parameters, the vortex pinning regimes were discussed. We find that the improvement of pinning by BZO is much reduced with respect to the effect observed in films grown on single crystals. In particular, the reduction of the critical temperature must be taken into account in order to appreciate the results. © 2016 IEEE
Development and characterization of biaxially-textured lanthanum zirconate film grown on cold-rolled Ni-W substrate by chemical solution deposition
No full textHigh temperature superconducting tapes based on cuprate compounds are nowadays available on long lengths by several companies. Because high superconducting properties are strongly influenced by the crystallographic orientation of the superconducting film, and because the appropriate crystallographic orientation is obtained through epitaxial film growth, the development of an oriented template is of crucial technological importance. In the rolling assisted biaxially textured substrate (RABiTS) technique, a strong cube texture is obtained by cold rolling fcc metal tape and high temperature annealing, followed by the deposition of one or more buffer layer by either physical vapor deposition (PVD) or chemical solution deposition (CSD). Using the latter approach, it has been recently shown that it is possible to combine substrate recrystallization and buffer layer growth in a single step if the onset of recrystallization occurs at a temperature lower than buffer layer nucleation. In the present contribution, a detailed investigation of biaxially-oriented La2Zr2O7 (LZO) buffer layer grown on cold-rolled Ni-W substrate by combined EBSD, AFM and TEM analyses is reported. It is shown that it is possible to obtain highly {001}〈110〉-textured LZO film directly on cold-rolled Ni-W substrate. Although some small polycrystalline regions appear, this approach leads to a strong suppression of grain boundary grooving typically occurring in RABiT-type substrates. Further, it is shown that, notwithstanding the microstructure of the metal substrate continues to evolve during the conversion heat treatment, the obtained LZO film is well adherent, without cracks or delamination. © 201
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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