Figure 5

(a) A STEM image of the Sr_0.6K_0.4Fe₂As₂ grain boundary.(b) The EDS line scan (as denoted in (a)) indicates that the grain boundary is filled with Sn rich material. Typical SEM images for Sr_0.6K_0.4Fe₂As₂tapes annealed at high temperature (c) and low temperature (d).