Melt-processed LRE-Ba-Cu-O superconductors and prospects for their applications

We have recently found that control of the oxygen partial pressure (PO₂) during melt processing, named the oxygen-controlled melt-growth (OCMG) process, is critical for obtaining a high superconducting transition temperature (T_c) in the light rare earth (LRE)-Ba-Cu-O (LREBCO) superconductors particularly for Nd, Sm and Eu. Further, compared to a good melt-processed Y-Ba-Cu-O (YBCO) bulk superconductor, LREBCO bulks exhibit larger critical current density (J_c) in high magnetic field and a much improved irreversibility field (H_irr) at 77 K, implying that more effective flux pinning can be realized in a commercially feasible way. In this paper, properties and characteristic flux pinning of OCMG-processed LREBCO (LRE: Nd,Sm,Eu) superconductors are described on the basis of our study during the last several years. We also present the prospects for bulk-type applications, such as the magnetic bearings, flywheels and magnetically levitated (MAGLEV) trains.