The Influence of Y‑211 Content on the Growth Rate and Y‑211 Distribution in Y–Ba–Cu–O Single Grains Fabricated by Top Seeded Melt Growth

The melt processing of Y–Ba–Cu−O (YBCO) single grains has been investigated using different isothermal temperature profiles for precursor powders containing varying amounts of Y-211. The crystal morphology of the as-grown YBCO single grains and the growth rate, which is influenced critically by the initial Y-211 content and the under-cooling temperature, have been analyzed. A simple method to determine an optimum temperature profile for the growth of bulk YBCO single grains has been proposed based on the results of this investigation. The influence of the initial Y-211 content on the macrosegregation of Y-211 inclusions for the different crystallographic orientations and different under-cooling temperatures has been analyzed. The correlation between the initial Y-211 content and the macrosegregation of Y-211 inclusions within the YBCO single grain along the different growth directions is interpreted from the growth rate data using Y-diffusion mechanism and pushing/trapping theory. Finally, an improved method for fabricating bulk YBCO superconductors containing a uniform distribution of pinning centers in the single grain, which has significant potential for improving the superconducting properties of bulk YBCO superconductors for practical applications, is proposed.