An overview of the coated conductor progress at IGC-SuperPower

The application and commercialization of high T-C superconductors require consistent high J(C) (critical current density) over the length of the conductor. High J(C) is not difficult to achieve using a Y-Ba-Cu-O (YBCO) superconductor on well-polished ceramic single crystal substrates. However, the application of the coated superconductor to longer lengths needs to have smooth and uniform metal substrates. Smooth and uniform metal substrates are critical for the uniformity of texture for the buffer layers and the subsequent epitaxial growth of the YBCO conductor. In comparison with ceramics, a highly polished metal substrate is hard to achieve without scratching and deformation since it is ductile. It is even more challenging to attain these properties over long lengths of metal substrates. Aimed at solving this problem and making it possible to produce coated superconductors, we have developed a reel-to-reel polishing process which can produce long length, highly polished metal substrates. The typical average surface roughness (Ra) of these long lengths of tape is about 3 nm in a scan area of 160 x 120 mum(2) using optical profilometer. A uniform buffer layer with good texture has been deposited on this metal substrate in continuous mode. YBCO deposited on to the buffered metal tape in a moving mode shows excellent epitaxial growth and superconducting properties. The critical current density (J(C)) over several centimeters of tape exceeds 10(6) A/cm(2) at 77 K. (C) 2002 Elsevier Science B.V. All rights reserved.