Current distributions of grain boundaries in differently processed melt-textured YBa2Cu3O7

• Published in: Superconductor science & technology 2001-05, Vol.14 (5), p.260-275
• Main Authors: Jooss, Ch, Bringmann, B, Delamare, M P, Walter, H, Leenders, A, Freyhardt, H C
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Critical currents; Cuprates superconductors (high tc and insulating parent compounds); Exact sciences and technology; High-Tc compounds; Physics; Properties of type I and type II superconductors; Superconductivity; Vortex lattices ,flux pinning, flux creep; Y-based cuprates
• ISSN: 0953-2048; 1361-6668
• DOI: 10.1088/0953-2048/14/5/306

The local current density distribution of grain boundaries in differently processed melt-textured YBa2Cu3O7-d (YBCO) is investigated by a magneto-optical technique and inversion of Biot-Savart's law. By correlating the local current density with the microstructure revealed by SEM, authors are able to distinguish the depression of the Jc at clean grain boundaries (GBs) from that occurring at normal phases and cracks at and in the vicinity of GBs. The GBs are formed by different multi-seeding melt-growth processes using a nonstoichiometric precursor which is optimized with respect to the bulk critical current. To obtain GBs with extended regions free of normal phases and with large Jc's the amount of liquid phase and the density of Y2BaCuO5 particles has to be controlled. The properties of GBs can be tailored by both controlling the amount of liquid phase and the seed distance. The related changes in growth and microstructure are analyzed and authors show how to grow extended GBs almost free of normal phases with optimized Jc's in multiple-seeded melt-growth YBCO. 33 refs.