Papers by Keyword: Coated Conductor

Abstract: YBa₂Cu₃O_7-δ (YBCO) coated conductors have wide-ranging potential in large scale applications, such as, superconducting maglev trains and superconducting electric cables, but low current carrying capability restrains the practical application of YBCO coated conductors at high temperatures and high magnetic fields. It is crucial to develop YBCO coated conductors with high flux pinning capability. In this paper, epitaxial, dense, smooth and crack-free YDy_xBa₂Cu₃O_7-δ (x = 0~0.5) films were prepared on a LaAlO₃ (LAO) single crystal substrate via a fluorine-free polymer-assisted metal organic deposition (PA-MOD) method. The effects of Dy addition on the microstructure and superconducting character of YBCO films were investigated. The all films show a strong c-axis orientation and good texture in-plane and out of plane. The Dy addition to the YBCO film hardly affects the critical temperature of YBCO superconductor. The irreversibility fields of YBCO films can be improved with the Dy addition x = 0.5 compared to the pure YBCO film but decreased in the x = 0.3 sample.

Abstract: on beam assisted deposition (IBAD) is an important technique to fabricate the second generation high temperature superconducting (2G HTS) wires. Among the fabrication routes of 2G HTS long wires, IBAD route achieved the best performance in recent years. IBAD was adopted in this field in 1991 to obtain biaxially textured buffer layers, which helped to deposit high quality YBCO superconducting films on metallic substrates for the first time. Series of experimental and industrial researches on IBAD were carried out by many groups worldwide. And in the researches lasting for over two decades, the focused material for IBAD was changed from Yttria-Stabilized Zirconia (YSZ), Gd₂Zr₂O₇ (GZO) to MgO. In this paper, the research progresses and the main achievements were briefly reviewed.

Abstract: Electron backscattered diffraction (EBSD) technology was applied to study the effect of pre-recovery on the recrystallization texture in nickel substrates for coated conductors. Pure nickel (99.999%) was cold rolled by a 95% total reduction, and then samples were annealed at 200 °C for 1 hour and quenched for fully recovery, and finally annealed at 600 °C for 1 hour and quenched in water. The results show that pre-recovery had a strong influence on the formation of cube recrystallization texture. Compared with samples without pre-recovery treatment at 200 °C, samples through pre-recovery treatment can achieve stronger cube texture after recrystallization annealing, and develop more low-angle grain boundaries but less sigma 3 (Σ3) grain boundaries.

Abstract: The goal of present study was to manufacture and characterize the Ni-5 at.% W alloy substrates for coated conductor applications with a strong cube texture. Cube-textured Ni-5 at.% W alloy substrates were fabricated by heavy cold rolling (98%) and a high temperature annealing (1200°C). From the EBSD and XRD analysis of the fully recrystallized tapes, the cube texture component in the tape was found to reach a proportion as high as 99.5% within a tolerance angle of less than 9^o, while the FWHM (full width at half maximum) values of the out-of-plane and in-plane textures are about 5.8^o and 6.9^o, respectively. Moreover, the grain size distribution is homogeneous, and there is a large amount of low angle grain boundaries (95.6%). This process is very suitable for preparation of substrates for coated conductors.

Abstract: It is well know that Ni-5at.% W(Ni5W) and Ni-9.3at.% W(Ni9W) alloy substrates are two kinds of promising materials to be employed in coated conductors. The Ni5W substrate is very easy to produce cube texture, while the Ni9W alloy has a lower magnetic property and higher strength. However, the pure cube texture are not capable to be obtained in Ni9W alloy. In this work, the preparation and texture development in both Ni5W and Ni9W alloy substrates have been reported. Highly biaxial textured Ni5W substrate was fabricated by cold rolling, followed by three different annealing routes. The texture analysis indicated that a sharp cube texture was formed after annealing at a wide temperature range of 800-1100°C in as rolled Ni5W substrate. The high quality of cube orientation was obtained after a two step annealing (TSA) with farthing twin boundaries analyzed by EBSD. Furthermore, in order to obtain a pure cube texture in Ni9W alloy substrate, a typical rolling process was performed and the deformation texture was optimized in these substrates. The designed deformation texture components were obtained in Ni9W alloy when pre-heating the ingot at 250 °C before performing a cold rolling, which shows a possibility to form cube texture in Ni9W alloy substrate after annealing.

Abstract: CeO2 has been considered as one of the most lattice compatible and chemically stable materials for YBa2Cu3O7-x coated conductors. In this paper, we presented the epitaxial growth of CeO2 thin film on both YSZ single crystal and cube textured Ni5W substrates by MOD method. Homogenous, crack-free and dense CeO2 thin films on both substrates with sharp biaxially cube texture were fabricated by post-annealing the precursor films at 1000-1150°C. For the CeO2 film on the textured Ni5W substrate, the FWHM values of (111) Phi-scan and (002) rocking curve were around 6°and 7°, respectively, the surface roughness was less than 2 nm over an area of 1μm×1μm observed by AFM. It was found that the CeO2 thin film improved both the in-plane orientation and surface roughness of the Ni5W substrate, indicating that the as deposited CeO2 films were suitable for the further growth of YBCO superconductor layer.

Abstract: A new series of ReBiO3 (RBO, Re=Y, Sm or other lanthanide) layers have been prepared on single crystal LaAlO3 or SrTiO3 respectively by a low-cost chemical solution deposition (CSD) method, and their structures have been investigated. With deferent Re element, the ReBiO3 phase has a similar cubic lattice with the pseudo-cubic lattice parameter a’ of about 3.81~3.94Å, which is closely matched to that of the ReBa2Cu3Ox (RBCO). In addition, these ReBiO3 phase are stable when they are sintered on 750~1050°C. After annealed below 850°C in air, highly c-axis oriented ReBiO3 layers can be formed on the (100) plane of single crystal LaAlO3 or SrTiO3. Observed under SEM, these layers appear very dense, smooth, pinhole-free and crack-free morphology. With the matched lattice parameter, lower annealing temperature, good grain-orientation and smooth surface, ReBiO3 layers should be candidates for the buffer layers of RBCO coated conductor. As a proof, a superconducting layer of YBCO has been deposited also by a CSD approach on one of these layers and show good texture and expected superconductivity.

Abstract: This work reports some new studies related to critical aspects in the development of coated conductors (CC). New bi-axially textured tapes based on commercial copper alloys were fabricated and tested as substrates for LZO buffer layer deposited by chemical solution deposition (CSD). Such a layer form cube texture on NiW5 and Cu55Ni45 with an identical or even better texture than that of the substrate. It was shown that a S c(2x2) sub-layer formed at the metallic surface as a positive effect on the nucleation. The crystallisation of LZO on Cu55Ni45 still has to be improved, being inhibited by trapped C in the film. Recent progresses using our continuous MOCVD system are shown. A CC fabricated by an all MOCVD process has been obtained on SS/YSZIBAD substrate with high transport critical current (170 A/cm-width, at 77 K). It is also shown that LZOMOD can efficiently protect Ni5W RABITS from oxidation during deposition of CeO2 layer by MOCVD under 30-40% O2 partial pressure. This opens the possibility to fabricate a CC on RABITS by MOCVD. This shows that a mixed MOD/MOCVD approach could be efficient. Finally a 2m long CC SS/YSZIBAD has been tested for fault current limiter applications. Best limitation was observed at 86 K where an equivalent energy of 340 J has been dissipated in the CC during 12 ms without apparent damage of the CC. In a subsequent operation, the CC was however destroyed. The causes are discussed in the perspective to design better architectures for this application.

Abstract: After the emergence of AC NbTi strands, superconducting transformers were successfully built. But the very high cost of 4 K cryogenics made these transformers economically not attractive. The high Tc superconductors (HTS), operating at much higher temperatures, change these conclusions with low cost HTS conductors. The high cost of PIT tapes and the relatively large AC losses remain issues. The second generation HTS wires, the REBCO coated conductors, are under development and achieved substantial progress recently. They operate at higher temperatures and intrinsically show lower AC losses especially for transformers. MgB2 is the third option. The magnetic flux density conditions make possible the operation at 27 K and they show low costs. This paper provides a preliminary design for an on-board 40 MVA transformer using YBCO coated conductors and MgB2 wires. Both superconducting transformers show similar volume and weight. The power density per unit mass and volume is improved by a factor about two, cryogenic included, compared to resistive systems. This makes them very attractive for on-board mobile systems. The economical point of view will be discussed based on some targets price/performance for superconductors and cryocoolers. MgB2 is penalized by its operation at lower temperature (27 K / 77 K), which makes cryogenics very expensive. The advantage of the low cost of MgB2 compared to REBCO may be lost except with very low AC loss MgB2 tapes.

Abstract: In this present work, two buffer layers (La2Zr2O7 and CeO2) were deposited by a non-contact computer-controlled ink-jet coating technique with sol-gel precursors on highly textured Ni-5%W Rolling Assisted Biaxially Textured substrates (RABiTS). Lanthanum acetate and cerium acetylacetonate were used as precursors for the LZO and CeO2 sol respectively. After a high temperature heat treatment (heating at 900°C for LZO and at 1100°C for CeO2) under reducing atmosphere, epitaxial textured buffer layers were obtained. XRD and pole figures were used to analyse the texture of the films, the microstructure was analysed by SEM.