Development of scribing process of coated conductors for reduction of AC losses

Coated conductors (CCs) are prospective for electric power applications intended for not only better cost performance but also high critical current density (J(c)) under magnetic fields comparing with Bi2Sr2Ca2Cu3Oy (BSCCO) tapes. Furthermore, they also have a possibility to reduce AC losses by various methods of post-treatments since the CCs are of a laminated structure with the insulating buffer layers. Multifilamentation by narrowing the tape width is quite effective to reduce the AC losses and therefore this approach is valid for the standard process to fabricate practical CCs with an appropriate architecture. In this study, we developed a tape scribing technique applying a technique of YAG laser with/without chemical etching to control the filament width in YBa2Cu3Oy (YBCO) CCs for the multifilament The AC. loss was reducible to one-twentieth by 20-multifilament structure in a short sample test, and to one-third by 3-multifilament structure in the coil using 28 m long tapes in total. The authors measured the resistance between the filaments at 60-300 K after post-treatment to investigate the effective bridged materials, which is essential for decoupling of the filaments. We improved the resistance value between the filaments at liquid nitrogen temperature up to the order of 10 Omega/cm using the YAG laser with high-temperature oxygen anneals. Furthermore, the resistance over 10(6) Omega/cm was evident by the combination of laser scribing and chemical etching, which is much higher than the requirements of all the applications. (c) 2008 Elsevier B.V. All rights reserved.