On the mechanisms of Jc increment and degradation in high Jc Ba122 tapes made by the different processing

We compared the grain and grain boundary (GB) nanostructures in two Ba122 tapes with similarly high Jc. The Ag-sheathed tape made by hot pressing has the 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 Ag-Sn/Stainless steel sheath possesses less plate-like grains and weak 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 GB for further Jc improvement of Ba122 tapes.