On the mechanisms of J c increment and degradation in high-J c Ba122 tapes made by different processing methods

Abstract

We compared the grain and grain boundary (GB) nanostructures in two Ba122 tapes with similarly high J c. The Ag-sheathed tape made by hot pressing has larger, more plate-like grains with better c-axis alignment but has more GBs blocked by FeAs and Ba–O. In contrast, the tape made by cold pressing with an Ag-Sn/stainless steel sheath possesses fewer plate-like grains and weaker grain alignment but has more continuous current paths with clean physically well-connected GBs. Our nanostructural comparison emphasizes the strong need to achieve both good grain alignment and clean GBs for further J c improvement of Ba122 tapes.