期刊
NATURE MATERIALS
卷 13, 期 4, 页码 375-381出版社
NATURE PUBLISHING GROUP
DOI: 10.1038/NMAT3887
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- ARRA grant of the US Department of Energy, Office of High Energy Physics [DE-SC0010421]
- National Science Foundation [NSF/DMR-1157490]
- State of Florida
Magnets are the principal market for superconductors, but making attractive conductors out of the high-temperature cuprate superconductors (HTSs) has proved difficult because of the presence of high-angle grain boundaries that are generally believed to lower the critical current density, J(c). To minimize such grain boundary obstacles, HTS conductors such as REBa2Cu3O7-x and (Bi, Pb)(2)Sr2Ca2Cu3O10 x are both made as tapes with a high aspect ratio and a large superconducting anisotropy. Here we report that Bi2Sr2CaCu2O8-x (Bi-2212) can be made in the much more desirable isotropic, round-wire, multifilament form that can be wound or cabled into arbitrary geometries and will be especially valuable for high-field NMR magnets beyond the present 1 GHz proton resonance limit of Nb3Sn technology. An appealing attribute of this Bi-2212 conductor is that, being without macroscopic texture, it contains many high-angle grain boundaries but nevertheless attains a very high J(c) of 2,500 Amm(-2) at 20 T and 4.2 K. The large potential of the conductor has been demonstrated by building a small coil that generated almost 2.6 T in a 31 T background field. This demonstration that grain boundary limits to high J(c) can be practically overcome underlines the value of a renewed focus on grain boundary properties in non-ideal geometries.
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