THE FABRICATION OF BI-BASED SUPERCONDUCTOR TAPE BY ELECTROPHORETIC DEPOSITION AND MELT-TEXTURING TECHNIQUES

Journal article

A processing technique has been developed for the fabrication of high current Bi-2212 superconductor tapes. The technique comprises three steps: (1) treating the particulate ceramic superconductor with trichloroacetic acid in 2-butanol to generate a negative charge on the particle surface; (ii) electrophoretic deposition of the particulate ceramic onto an Ag-based substrate and (iii) melt texturing of the deposit to form a superconductor coating on the substrate. It has been found that the 2212 superconductor can only be melt textured on an Ag substrate in a narrow temperature window around 885°C. Slow cooling from the molten state not only allows the development of superconductor phase texture but also suffers from the growth of Ca-Cu-O oxides. These oxides can be transformed into 2212 phase by annealing at 850°C. However, the 2212 grains formed from the Ca-Cu-O precipitates are invariably oriented at right angles to the 2212 phase formed in the course of solidification. The presence of such large angle grain boundaries is detrimental to the superconductor properties. An optimal processing procedure has been proposed and some important processing parameters discussed. A pilot plant been set up and semi continuous tape of Bi-2212 superconductor on Ag has been produced. Critical currents as high as 155 A have been measured over a length of 1 m of multilayer coil at 4.2 K. The performance corresponds to a critical current density of about 70000 A cm-2 in the superconductor layer in a self field up to about 64 mT. The uniformity of Jc measured on adjacent 10 cm lengths in the multilayer coil is much better than that in a single layer coil, about 30% variation in the former compared with 80% in the latter. The results show that electrophoretic tapes have a promising future for integration into small magnet windings.

Authors: Yang, M; Goringe, M; Grovenor, C; Jenkins, R; Jones, H

• Publication status: Published
• Journal: SUPERCONDUCTOR SCIENCE and TECHNOLOGY
• Volume: 7
• Issue: 6
• Pages: 378-388
• Publication date: 1994-06-01
• DOI: 10.1088/0953-2048/7/6/009
• EISSN: 1361-6668
• ISSN: 0953-2048
• Language: English