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Self-fields in thin superconducting tapes: implications to the thickness effect in coated conductors  [PDF]
Alvaro Sanchez,Carles Navau,Nuria Del-Valle,Du-Xing Chen
Physics , 2009, DOI: 10.1063/1.3315893
Abstract: Most applications of superconductors, such as power transmission lines, motors, generators, and transformers, require long cables through which large currents circulate. Impressive progress has recently been achieved in the current-carrying capability in conductors based on high-temperature superconductors. Coated conductors are likely the best examples, consisting of very good quality thin layers of YBCO superconductor grown on top of a metallic tape with some intermediate layers. However, there is an important problem for achieving large currents: a large decrease in transport critical-current density Jc when increasing film thickness has been observed in coated conductors made by all available techniques. Here, we theoretically explain the nature and the ubiquitous presence of this so-called thickness effect by analyzing the self-field created by the transport currents in the superconductor, assuming a realistic field-dependent Jc. This knowledge can help finding new ways to improve transport current in thick superconducting films.
Simulation of Stacks of High Temperature Superconducting Coated Conductors Magnetized by Pulsed Field Magnetization Using Controlled Magnetic Density Distribution Coils  [PDF]
Shengnan Zou,Victor Manuel Rodriguez Zermeno,Francesco Grilli
Physics , 2015,
Abstract: High temperature superconducting (HTS) stacks of coated conductors (CCs) can work as strong trapped field magnets (TFMs) and show potential in electrical applications. Pulsed field magnetization (PFM) is a practical method to magnetize such TFMs, but due to heat generation during the dynamic process, it cannot achieve a trapped field as high as field cooling can. In this work, we construct a 2D electromagnetic-thermal coupled model to simulate stacks of HTS CCs with realistic laminated structures magnetized by PFM. The model considers temperature and anisotropic magnetic field dependent Jc of HTS and other temperature dependent thermal and electrical material properties. Based on the model, a configuration of controlled magnetic density distribution coils is suggested to improve the trapped field compared to that obtained by ordinary solenoids.
Strongly Enhanced Current Densities in Superconducting Coated Conductors of YBa2Cu3O7-x + BaZrO3  [PDF]
J. L. MacManus-Driscoll,S. R. Foltyn,Q. X. Jia,H. Wang,A. Serquis,L. Civale,B. Maiorov,M. E. Hawley,M. P. Maley,D. E. Peterson
Physics , 2004, DOI: 10.1038/nmat1156
Abstract: There are numerous potential applications for superconducting tapes, based on YBa2Cu3O7-x (YBCO) films coated onto metallic substrates. A long established goal of more than 15 years has been to understand the magnetic flux pinning mechanisms which allow films to maintain high current densities out to high magnetic fields. In fact, films carry 1-2 orders of magnitude higher current densities than any other form of the material. For this reason, the idea of further improving pinning has received little attention. Now that commercialisation of conductors is much closer, for both better performance and lower fabrication costs, an important goal is to achieve enhanced pinning in a practical way. In this work, we demonstrate a simple and industrially scaleable route which yields a 1.5 to 5-fold improvement in the in-field current densities of already-high-quality conductors.
Doubling the Critical Current Density of High Temperature Superconducting Coated Conductors through Proton Irradiation  [PDF]
Y. Jia,M. LeRoux,D. J. Miller,J. G. Wen,W. K. Kwok,U. Welp,M. W. Rupich,X. Li,S. Sathyamurthy,S. Fleshler,A. P. Malozemoff,A. Kayani,O. Ayala-Valenzuela,L. Civale
Physics , 2013, DOI: 10.1063/1.4821440
Abstract: The in-field critical current of commercial YBa2Cu3O7 coated conductors can be substantially enhanced by post-fabrication irradiation with 4 MeV protons. Irradiation to a fluence of 8x10^16 p/cm^2 induces a near doubling of the critical current in fields of 6 T || c at a temperature of 27 K, a field and temperature range of interest for applications such as rotating machinery. A mixed pinning landscape of preexisting precipitates and twin boundaries and small, finely dispersed irradiation induced defects may account for the improved vortex pinning in high magnetic fields. Our data indicate that there is significant head-room for further enhancements.
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
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.
On narrowing coated conductor film: emergence of granularity-induced field hysteresis of transport critical current  [PDF]
A. A. Gapud,D. K. Christen,R. Feenstra,F. A. List III,A. Khan
Physics , 2008, DOI: 10.1088/0953-2048/21/7/075016
Abstract: Critical current density Jc in polycrystalline or granular superconducting material is known to be hysteretic with applied field H due to the focusing of field within the boundary between adjacent grains. This is of concern in the so-called coated conductors wherein superconducting film is grown on a granular, but textured surface of a metal substrate. While previous work has mainly been on Jc determined using induced or magnetization currents, the present work utilizes transport current via an applied potential in strip geometry. It is observed that the effect is not as pronounced using transport current, probably due to a large difference in criterion voltage between the two types of measurements. However, when the films are narrowed by patterning into 200-, 100-, or 80-micron, the hysteresis is clearly seen, because of the forcing of percolation across higher-angle grain boundaries. This effect is compared for films grown on ion-beam-assisted-deposited (IBAD) YSZ substrate and those grown on rolling-assisted-biaxially-textures substrates (RABiTS) which have grains that are about ten times larger. The hysteresis is more pronounced for the latter, which is more likely to have a weak grain boundary spanning the width of the microbridge. This is also of concern to applications in which coated conductors will be striated in order to reduce of AC losses.
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.
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.
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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