Sm–Ba–Cu–O bulk superconductors melt processed in air, using Nd123/MgO thin film cold seeding

It is well known that melt processed REBaCuO (RE: rare-earth) superconductors have a high J c at 77 K and high magnetic field, and that light rare-earth BaCuO has a larger J c than Y123 in high magnetic field. High field applications such as a superconducting permanent magnet with the liquid nitrogen refrigeration and flywheels are expected. In this study, for improving superconducting properties and producing a larger bulk, we discuss Sm123 bulks melt processed in air and their characteristic superconducting properties. Isothermal undercooling growth in air with oxygen annealing and Nd123/MgO thin film cold seeding technique were applied in SmBaCuO/Ag system to seek the high efficiency of process, homogeneity of composition, and feasibility of batch production. We investigated process conditions such as heat treatment temperatures, compositions, seeding methods, and atmosphere. Single domain growth of superconducting phases of a square larger than 10 mm on a side and 10 mm in thickness was achieved using this technique. The result implies that melt processed in air applying isothermal method and thin film seeding in Sm system is feasible for producing larger bulks in large scale applications.