Superconducting and mechanical properties of RE-Ba-Cu-O/Ag bulk superconductors

Melt-processed REBaCuO (RE: rare earth) superconductors have a high J_c at 77 K and a high magnetic field, which are expected to be used for high field applications such as superconducting permanent magnets with liquid nitrogen refrigeration, flywheels, current leads and so on. In this study, we discuss Ag-doped YBaCuO and SmBaCuO bulks melt-processed in air and their characteristic superconducting and mechanical properties. Isothermal undercooling growth in air with oxygen annealing and the Nd123/MgO thin film cold seeding technique were applied to seek a highly efficient process, homogeneity of composition, and feasibility of batch production. Single-domain growth of superconducting phases was achieved. The results of mechanical properties, e.g. flexural stress of REBaCuO bulk superconductors show the beneficial effect of Ag particles in the RE123 superconducting phase on strengthening and toughening the material. The results imply that the melt process is feasible for producing larger bulks in large-scale applications. Applications of superconducting technology to railways are also discussed.