Addition of Nanoparticle Dispersions to Enhance Flux Pinning of the YBa2Cu3O7-x Superconductor

摘要

After the discovery of type-II HTS, focus is to develop these materials for power applications. One of the problems has been that magnetic flux is not completely expelled but rather contained within magnetic fluxons, whose motion stops larger supercurrents. It's known that the critical current of these materials can be enhanced by incorporating a high density of extended defects to act as pinning centres for the fluxons. YBa2Cu3O7 (YBCO or 123) is the most promising material for such applications at higher temperatures. Pinning is optimized when the size of the defects approaches the superconducting coherence length (approximately 2-4nm for YBCO at temperatures 77 K) and when the areal number density of defects is of the order of (H/2) x 1011 cm-2, where H is the applied magnetic field in tesla. Such a high density has been hard to get by material-processing methods that keep a nanosize defect, except through irradiation. Here we report a method for achieving a dispersion of 8-nm-sized nanoparticles in YBCO with a high number density, which increases critical current (approximately at 77 K) by a factor of two to three for high magnetic fields.