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AC Losses of Copper Stabilized Multifilament YBCO Coated Conductors  [PDF]
G. A. Levin,J. Murphy,T. J. Haugan,J. ?ouc,J. Ková?,P. Ková?
Physics , 2012,
Abstract: We report the data on magnetization losses and critical current of multifilament copper stabilized coated conductors. Eight centimeters long samples of copper stabilized YBa2Cu3O7-x (YBCO) coated conductors manufactured commercially were subdivided into superconducting filaments by near-IR laser micromachining. The width of the superconducting stripes was varied from 0.2 mm to 0.04 mm. Some of the samples were striated leaving superconducting bridges for current sharing between the filaments. The AC losses were measured at different sweep rates of the magnetic field up to 14 T/s. We will present the results for the hysteresis and coupling losses and discuss the means to reduce the coupling loss by changing the processing parameters of micromachining and by post-ablation treatment.
Conductive Buffer Layers and Overlayers for the Thermal Stability of Coated Conductors  [PDF]
Claudia Cantoni,Tolga Aytug,Darren T. Verebelyi,Mariappan Paranthaman,Eliot D. Specht,David P. Norton,David K. Christen
Physics , 2001,
Abstract: We analyze fundamental issues related to the thermal and electrical stability of a coated conductor during its operation. We address the role of conductive buffer layers in the stability of Ni-based coated conductors, and the effect of a metallic cap layer on the electrical properties of Ni alloy-based superconducting tapes. For the first case we report on the fabrication of a fully conductive RABiTS architecture formed of bilayers of conductive oxides SrRuO3 and LaNiO3 on textured Ni tapes. For the second case we discuss measurements of current-voltage relations on Ag/YBa2Cu3O7-d and Cu/Ag/ YBa2Cu3O7-d prototype multilayers on insulating substrates. Limitations on the overall tape structure and properties that are posed by the stability requirement are presented.
Use of 2G coated conductors for efficient shielding of DC magnetic fields  [PDF]
J. -F. Fagnard,M. Dirickx,G. A. Levin,P. N. Barnes,B. Vanderheyden,P. Vanderbemden
Physics , 2010, DOI: 10.1063/1.3459895
Abstract: This paper reports the results of an experimental investigation of the performance of two types of magnetic screens assembled from YBa2Cu3O7-d (YBCO) coated conductors. Since effective screening of the axial DC magnetic field requires the unimpeded flow of an azimuthal persistent current, we demonstrate a configuration of a screening shell made out of standard YBCO coated conductor capable to accomplish that. The screen allows the persistent current to flow in the predominantly azimuthal direction at a temperature of 77 K. The persistent screen, incorporating a single layer of superconducting film, can attenuate an external magnetic field of up to 5 mT by more than an order of magnitude. For comparison purposes, another type of screen which incorporates low critical temperature quasi-persistent joints was also built. The shielding technique we describe here appears to be especially promising for the realization of large scale high-Tc superconducting screens.
Fabrication and characterization of La2Zr2O7 films on different buffer architectures for YBa2Cu3O7-delta coated conductors by RF magnetron sputtering
Da Xu, Linfei Liu, Guina Xiao and Yijie Li
Nanoscale Research Letters , 2013, DOI: 10.1186/1556-276X-8-109
Abstract: La2Zr2O7 (LZO) films were grown on different buffer architectures by radio frequency magnetron sputtering for the large-scale application of YBa2Cu3O7-x (YBCO)-coated conductors. The three different buffer architectures were cerium oxide (CeO2), yttria-stabilized zirconia (YSZ)/CeO2, and CeO2/YSZ/CeO2. The microstructure and surface morphology of the LZO film were studied by X-ray diffraction, optical microscopy, field emission scanning electron microscopy, and atomic force microscopy. The LZO films prepared on the CeO2, YSZ/CeO2, and CeO2/YSZ/CeO2 buffer architectures were preferentially c-axis-oriented and highly textured. The in-plane texture of LZO film on CeO2 single-buffer architecture was [increment]phi = 5.5[degree sign] and the out-of-plane texture was [increment]omega = 3.4[degree sign]. All the LZO films had very smooth surfaces, but LZO films grown on YSZ/CeO2 and CeO2/YSZ/CeO2 buffer architectures had cracks. The highly textured LZO film grown on CeO2-seed buffered NiW tape was suitable for the epitaxial growth of YBCO film with high currents.
Mechanisms of weak thickness dependence of the critical current density in strong pinning ex situ metal-organic-deposition route YBa2Cu3O7-x coated conductors  [PDF]
S. I. Kim,A. Gurevich,X. Song,X. Li,W. Zhang,T. Kodenkandath,M. W. Rupich,T. G. Holesinger,D. C. Larbalestier
Physics , 2006, DOI: 10.1088/0953-2048/19/9/013
Abstract: We report on the thickness dependence of the superconducting characteristics including critical current Ic, critical current density Jc, transition temperature Tc, irreversibility field Hirr, bulk pinning force plot Fp(H), and the normal state resistivity curve measured after successive ion milling of ~ 1 um thick high Ic YBa2Cu3O7-x films made by an ex situ metal-organic deposition process on Ni-W rolling-assisted biaxially textured substrates (RABiTS). Contrary to many recent data, mostly on in situ pulsed laser deposition (PLD) films, which show strong depression of Jc with increasing film thickness t, our films exhibit only a weak dependence of Jc on t. The two better textured samples had full cross-section average Jc,avg(77K,0T) ~ 4 MA/cm2 near the buffer layer interface and ~3 MA/cm2 at full thickness, despite significant current blocking due to ~30% porosity in the film. Taking account of the thickness dependence of the porosity, we estimate that the local, vortex-pinning current density is essentially independent of thickness, while accounting for the additional current-blocking effects of grain boundaries leads to local, vortex-pinning Jc values well above 5 MA/cm2. Such high local Jc values are produced by strong three-dimensional vortex pinning which subdivides vortex lines into weakly coupled segments much shorter than the film thickness.
High-Efficient Preparation of SmBiO3 Buffer Layer for Superconducting Coated Conductors

朱晓垒, 蒲明华, 张红, 赵勇
ZHU Xiaolei
, PU Minghua, ZHANG Hong, ZHAO Yong

- , 2017, DOI: 10.3969/j.issn.0258-2724.2017.03.027
Abstract: 为了缩短高温超导涂层导体缓冲层薄膜制备周期,采用自开发的前驱溶液,以乳酸为溶剂,硝酸钐和硝酸铋为溶质,在应由表面氧化外延法所得的衬底(NiO(l00)/NiW)上,用化学溶液沉积快速制备了SmBiO3缓冲层薄膜,研究成相温度对SmBiO3薄膜的影响;在SmBiO3薄膜上沉积YBa2Cu3O7-δ超导层,检验其效用. 研究结果表明:在798.5 ℃下制备的SmBiO3缓冲层薄膜平整致密,并且高度织构,缓冲层薄膜制备周期缩短到2 h以内;在SmBiO3上所沉积的超导层薄膜超导转变温度为89 K,超导临界电流密度为1.46 MA/cm2(77 K、0 T),达到了某些电力应用要求;该SmBiO3薄膜制备方法可用于高温超导涂层导体的快速制备.
: In order to shorten the preparation period of buffer layer for high-performance coated conductors, SmBiO3 (SBO) buffer films were efficiently deposited on surface-oxidation epitaxy processed NiO(100)/NiW substrates by chemical solution deposition (CSD) method, using a precursor solution prepared by dissolving samarium nitrate and bismuth nitrate precursors in lactic acid. The effect of sintering temperature on the SBO film was systematically studied. Then, the YBa2Cu3O7-δ (YBCO) superconductive film was deposited on the SBO buffer layer to test its utility. Results show that a highly textured, smooth and dense SBO thin film was obtained at 798.5 ℃, and the SBO thin film could be prepared within a period of less than 2 h. The YBCO superconductive layer was successfully deposited on the SBO layer with a superconducting transition temperature of 89 K and a critical current density of 1.46 MA/cm2 (77 K, 0 T), which could be used in some electric power applications. Therefore, the proposed method for preparing SBO buffer layer can be used for rapid preparation of coated conductors
Through-thickness superconducting and normal-state transport properties revealed by thinning of thick film ex situ YBa2Cu3O7-x coated conductors  [PDF]
D. M. Feldmann,D. C. Larbalestier,R. Feenstra,A. A. Gapud,J. D. Budai,T. G. Holesinger,P. N. Arendt
Physics , 2003, DOI: 10.1063/1.1625103
Abstract: A rapid decrease in the critical current density (Jc) of YBa2Cu3O7-x (YBCO) films with increasing film thickness has been observed for multiple YBCO growth processes. While such behavior is predicted from 2D collective pinning models under certain assumptions, empirical observations of the thickness dependence of Jc are believed to be largely processing dependent at present. To investigate this behavior in ex situ YBCO films, 2.0 and 2.9 um thick YBCO films on ion beam assisted deposition (IBAD) - yttria stabilized zirconia (YSZ) substrates were thinned and repeatedly measured for rho(T) and Jc(H). The 2.9 um film exhibited a constant Jc(77K,SF) through thickness of ~1 MA/cm2 while the 2.0 um film exhibited an increase in Jc(77K,SF) as it was thinned. Neither film offered evidence of significant dead layers, suggesting that further increases in critical current can be obtained by growing thicker YBCO layers.
The Integration of YBCO Coated Conductors into Magnets and Rotating Machinery  [PDF]
G. A. Levin,P. N. Barnes
Physics , 2005, DOI: 10.1063/1.2192379
Abstract: The implementation of the 2nd generation high-Tc superconductors in power applications, such as electrical transformers, motors and generators requires superconducting wires that are superior to copper Litz wires at cryogenic temperatures in terms of losses in time-varying magnetic field, as well as in engineering current density. Another problem is to find a way to make practical coils and armatures out of flat tape-like conductors with low bending strain tolerance. We discuss several novel approaches to the construction of coils and armatures based specifically on the properties of coated conductors manufactured today.
Neutron irradiation of coated conductors  [PDF]
M. Eisterer,R. Fuger,M. Chudy,F. Hengstberger,H. W. Weber
Physics , 2009, DOI: 10.1088/0953-2048/23/1/014009
Abstract: Various commercial coated conductors were irradiated with fast neutrons in order to introduce randomly distributed, uncorrelated defects which increase the critical current density, Jc, in a wide temperature and field range. The Jc-anisotropy is significantly reduced and the angular dependence of Jc does not obey the anisotropic scaling approach. These defects enhance the irreversibility line in not fully optimized tapes, but they do not in state-of-the-art conductors. Neutron irradiation provides a clear distinction between the low field region, where Jc is limited by the grain boundaries, and the high field region, where depinning leads to dissipation.
Stability and normal zone propagation speed in YBCO coated conductors with increased interfacial resistance  [PDF]
George A. Levin,Paul N. Barnes,Jose P. Rodriguez,Jake A. Connors,John S. Bulmer
Physics , 2008, DOI: 10.1109/TASC.2009.2019604
Abstract: We will discuss how stability and speed of normal zone propagation in YBCO-coated conductors is affected by interfacial resistance between the superconducting film and the stabilizer. Our numerical simulation has shown that the increased interfacial resistance substantially increases speed of normal zone propagation and decreases the stability margins. Optimization of the value of the resistance may lead to a better compromise between stability and quench protection requirements than what is found in currently manufactured coated conductors.
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