Abstract
Multi-seeded bulk superconductors have been studied in order to improve a problem in the conventional multi-seeding method: the existence of excluded non-supercondcting phases (liquid phases and segregated RE211 phases) at the grain boundaries in the bulk superconductor. First, a crystal growth experiment using a precursor with holes was carried out instead of the experiment with two seed crystals. Exclusion and the disappearance of non-superconducting phases were observed around the holes. We believed that this phenomenon was caused when crystal growth changes to the same direction from opposite directions. Through the extension of this theory, a new multi-seeding method, the MUSLE (MUlti-Seeded seamLEss bulk) technique was derived. The basic concept of this technique is that the precursor is composed of two or more RE-Ba-Cu-O layers with different peritectic temperatures, thereby allowing contorol of the directionthe directions of the crystal growth from the seed crystals. RE-Ba-Cu-O superconductors were fabricated using the MUSLE technique with 4 or 9 seeds. The trapped field distribution obtained at 77K showed a single peak, indicating that the MUSLE technique is effective in eliminating the excluded phases formed at the grain boundaries in multi-seeded bulk superconductors.
