Recycling process for 123-type bulk superconductors

Bulk (RE)-Ba-Cu-O (RE is a rare earth element or yttrium) high temperature superconductors have contained a lot of precious substances such as Ag and Pt, which led to a significant increase in production cost. However, the bulk superconductors have been thrown away once they were fractured during characterization or failed to grow in the form of single grain. The material recycling of these samples is, therefore, a great important and leads to a cost-effective production. Hence we have attempted a recycling process for Ag-doped Gd-Ba-Cu-O (GdBCO/Ag) bulk samples. The single grain GdBCO/Ag bulk sample, however, could not be grown by the cold-seeded melt-process albeit the recycled precursor powder is chemically identical to a mixture of commercial powder (reference powder). On the other hand, the hot-seeding technique enables us to fabricate readily the single grain GdBCO/Ag bulk samples even with employing the recycled precursor powder. The recycle-processed GdBCO/Ag bulk sample showed a 10% decrease in the trapped magnetic field compared with the reference bulk sample. However, most importantly this study demonstrates clearly, and for the first time, that the recycling of GdBCO/Ag bulk samples is possible, nevertheless a small degradation of superconducting properties is recognized.