Growth of large bulk Y-Ba-Cu-O with multi-seeding

Large bulk Y-Ba-Cu-O superconductors, 62mm in diameter and 12mm in thickness, have been fabricated by a cold seeding method in which four seeds are placed on top of the precursor at room temperature prior to melt processing. The advantage of a cold seeding technique is that the desired seeding location can be arranged at room temperature. However, due to the reaction of the seed with the precursor at high temperatures, controlled single-grain growth has been difficult. In the present study, we carefully investigated the influence of the processing parameters such as the maximum heating temperature, the dwelling time at this temperature, the temperature to start slow cooling and the slow cooling rate on the grain growth behavior. Through the optimization of these processing parameters, we have succeeded in growing large bulk Y-Ba-Cu-O with four large grains. The sample with 1wt% CeO₂ addition showed almost the same field trapping ability as a single-domain sample.