Design of microstructure in melt-textured bulk superconductors with the employment of granules containing ultra-fine Y₂BaCuO₅ particles

In melt-textured RE-Ba-Cu-O bulk superconductors, an excessive size reduction of RE211 inclusions results in inhomogeneous distribution of RE211 particles. To reduce such inhomogeneity, we attempted to combine granules containing fine RE211 into the melt-textured RE123 materials. First, we prepared Y-Ba-Cu-O granules containing Y123 and ultra-fine Y211 (0.1 μm in size) powders with organic binder. The size of the granules was about 1.0 mm. Next, Dy-Ba-Cu-O powders containing Dy123 and Dy211 (2 μm in size) were prepared. The Y-Ba-Cu-O granules and Dy-Ba-Cu-O powder were compacted together and melt-processed in air. We found that fine RE211 inclusions were uniformly distributed in this sample, which led to improved spatial homogeneity in critical currents.