Enhancing the superconducting performance of YBa2Cu3O7−δ bulks with nano-sized and well distributed Y2BaCuO5 particles

Abstract

The refinement and uniformity of Y₂BaCuO₅ (Y211) are of vital importance in preparing large-sized YBa₂Cu₃O_7−δ (Y123) bulks with high field trapping ability by top-seeded melt-growth (TSMG). However, the inherent enlargement and segregation of Y211 particles during the TSMG process have long puzzled researchers. Here, a novel method called L-MPP is reported, in which, instead of conventional precursor powder (CPP, Y123 plus Y211), modified precursor powder (MPP, Y₂O₃ plus Ba₂Cu₃O_x) is used to combine with a layered and compositional graded structure. Moreover, sizable Y123 bulks with a diameter of 25 mm were successfully prepared, rather than those of 16 mm reported in previous MPP work. The optical micrographs and quantitative analyses confirm that the Y211 particles in the L-MPP sample are visibly refined and better distributed simultaneously. As a result, the trapped fields of Y123 bulks significantly increase from 0.496 T of CPP to 1.01 T of L-MPP, and their levitation forces are enhanced by nearly 50% from 46.2 N of CPP to 68.3 N of L-MPP. Most importantly, this method is widely applicable for preparing other REBCO (RE = rare earth) bulk superconductors.