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High-temperature superconductor bulk magnets that can trap magnetic fields of over 17 tesla at 29 K

Nature volume 421, pages 517–520 (2003)Cite this article

Abstract

Large-grain high-temperature superconductors of the form RE-Ba-Cu-O (where RE is a rare-earth element) can trap magnetic fields of several tesla at low temperatures, and so can be used for permanent magnet applications1,2. The magnitude of the trapped field is proportional to the critical current density and the volume of the superconductor3,4. Various potential engineering applications for such magnets have emerged5,6,7,8,9,10,11,12,13, and some have already been commercialized7,8,9,10. However, the range of applications is limited by poor mechanical stability and low thermal conductivity of the bulk superconductors14,15,16,17; RE-Ba-Cu-O magnets have been found to fracture during high-field activation, owing to magnetic pressure14,15,16. Here we present a post-fabrication treatment that improves the mechanical properties as well as thermal conductivity of a bulk Y-Ba-Cu-O magnet, thereby increasing its field-trapping capacity. First, resin impregnation and wrapping the materials in carbon fibre improves the mechanical properties. Second, a small hole drilled into the centre of the magnet allows impregnation of Bi-Pb-Sn-Cd alloy into the superconductor and inclusion of an aluminium wire support, which results in a significant enhancement of thermal stability and internal mechanical strength. As a result, 17.24 T could be trapped, without fracturing, in a bulk Y-Ba-Cu-O sample of 2.65 cm diameter at 29 K.

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Figure 1: Resin-impregnated Y-Ba-Cu-O with carbon fibre wrapping.
Figure 2: Trapped-field data for two YBCO disks with carbon fibre wrapping and resin impregnation.
Figure 3: Cross-sectional view of a YBCO disk in which a hole of 1 mm diameter was drilled, followed by Bi-Pb-Sn-Cd alloy impregnation.
Figure 4: Trapped-field data for two fibre-wrapped, resin-impregnated YBCO disks with embedded Al wire.
Figure 5: The effect of temperature on trapped-field distribution.

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Acknowledgements

We thank K. Itoh and H. Wada for use of an 18-T superconducting magnet. This work was partially supported by NEDO as Collaborative Research and Development of Fundamental Technologies for Superconductivity Applications.

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Authors and Affiliations

  1. Superconductivity Research Laboratory, Shibaura 1-16-25, Minato-ku, 105-0023, Tokyo, Japan

    Masaru Tomita & Masato Murakami

  2. Railway Technical Research Institute, 2-8-38 Hikari-cho, Kokubunji-shi, 185-8540, Tokyo, Japan

    Masaru Tomita

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  1. Masaru Tomita
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Correspondence to Masaru Tomita.

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Tomita, M., Murakami, M. High-temperature superconductor bulk magnets that can trap magnetic fields of over 17 tesla at 29 K. Nature 421, 517–520 (2003). https://doi.org/10.1038/nature01350

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