Top surface morphologies of melt growth processed Y_(1.5)Ba_2Cu_3O_(7-y) bulk superconductors with corner or edge seeding

摘要

A corner or edge seeding was attempted to control top surface morphologies (facet lines) of top-seeded melt growth (TSMG) processed Y_(1.5)Ba_2Cu_3O_(7-y) (Y1.5) bulk superconductors. The orientation and numbers of facet lines were successfully modified using the corner/edge seeding with adjusted seed orientations. Most of the facet lines developed on the top surfaces were nearly straight, whereas some of them often had curvatures when the facet lines met the edges with high angles. The size of the growth area of Y123 on the top surfaces was dependent not only on the seeding method but also on the seed orientation. The unreacted regions were often observed on the local parts of the top surfaces, which are attributed to the difference in a growth rate among growth planes. The top surface with the corner seeding where the 〈1 1 0〉 growth direction is parallel to the diagonal of the Y123 compact showed the highest magnetic flux density and magnetic levitation forces owing to the largest growth area of Y123.