Double disordered YBCO coated conductors of industrial scale: high currents in high magnetic field

Abstract

A significant increase of critical current in high magnetic field, up to 31 T, was recorded in long tapes manufactured by employing a double-disorder route. In a double-disordered hightemperature superconductor (HTS), a superimposing of intrinsic and extrinsic disorder takes place in a way that (i) the intrinsic disorder is caused by local stoichiometry deviations that lead to defects of crystallinity that serve as pining centers in the YBa 2 Cu 3 O x−δ matrix and (ii) the extrinsic disorder is introduced via embedded atoms or particles of foreign material (e.g. barium zirconate), which create a set of lattice defects. We analyzed possible technological reasons for this current gain. The properties of these tapes over a wider field-temperature range as well as field anisotropy were also studied. Record values of critical current as high as 309 A at 31 T, 500 A at 18 Tm and 1200 A at 5 T were found in 4 mm wide tape at 4.2 K and B perpendicular to tape surface. HTS layers were processed in medium-scale equipment that allows a maximum batch length of 250 m while 22 m long batches were provided for investigation. Abnormally high ratios (up to 10) of critical current density measured at 4.2 K, 19 T to critical current density measured at 77 K, self-field were observed in tapes with the highest in-field critical current. Anisotropy of the critical current as well as angular dependences of n and α values were investigated. The temperature dependence of critical current is presented for temperatures between 4.2 and 40 K. Prospects for the suppression of the dog-bone effect by Cu plating and upscale of processing chain to >500 m piece length are discussed.

J e (4.2 K, 31.2 T) beyond 1 kA/mm2 of a ~3.2 μm thick, 20 mol% Zr-added MOCVD REBCO coated conductor

“…The value shown by our ~3.2 µm thick film is lower than that of our 15% Zr-added ~0.9 μm thick film and higher than the ~3.0 μm 15% Zr-added sample 35 . The sample exhibits I c above 1 kA at H up to 13 T, well above all other reported values 37 . Taking into account the ~50 μm thick substrate and ~40 μm thick surround copper stabilizer layer in commercial REBCO tapes, J e of this 20% Zr-added ~3.2 μm thick REBCO film reaches 1 kA/mm 2 at H up to 31.2 T, a real threshold for compelling, cost-effective applications.

Figure 4Field dependence of I c normalized to 4 mm wide tape, and J e at 4.2 K and magnetic fields up to 31.2 T. The ~3.2 μm thick film exhibits remarkable J e  > 1.0 kA/mm 2 at magnetic fields up to 31.2 T. J e was calculated based on the typical Hastelloy thickness of 50 μm and copper stabilizer thickness of 40 μm.

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Ultrafast transient liquid assisted growth of high current density superconducting films

“…We conclude that TLAG-CSD is an ultrafast non-equilibrium and versatile process to grow epitaxial YBCO films at c axis growth rates of ∼ 100 nm s −1 from different routes. This is~10-100 times faster than most of the thin film processes presently used 8,[29][30][31][32] to grow coated conductors and it confirms fast growth rates observed in other liquid-assisted techniques, such as in REBCO single crystal growth, REBCO bulk ceramic melt-textured growth 33 or REBCO films 14 . However here, the process is not restricted to the use of an equilibrium liquid phase and we demonstrate that the transient liquid formation is compatible with high-throughput CSD film manufacturing.…”

Advances in the Development of a 10-kA Class REBCO Cable for the EuCARD2 Demonstrator Magnet

“…Most recently, under a developing interest in high field applications, and thanks to the introduction of various pinning mechanisms (the most effective being BZO nanorods [19]), the performance at low temperature of industrially produced REBCO has progressed steadily. At 4.2 K and 20 T in perpendicular field, industrially produced REBCO has attained record values of J E in excess of 800 A/mm 2 [20], and the target performance of Table I was achieved by several production routes. In addition, the J E potential does not seem to be fully exploited [21].…”

“…The best results were achieved by introducing double-disorder in the YBCO layer. The extrinsic pinning obtained via precipitates of BZO in the form of nanorods, is complemented by intrinsic pinning created by intentional variation in the stoichiometry of the deposited layer [20]. It must be underlined that these tapes have a rather thick substrate, 100 µm of steel, and the reported values of J E correspond to a layer J C (4.2 K, 20 T) well exceeding 50 kA/mm 2 , which, to our knowledge, is the highest value reported to date for industrial tapes.…”