Local JC and microstructures of multilayer Bi-2212 composite tape

We investigated the local J_C and microstructures of Bi-2212 multilayer tapes. Multilayer tapes were prepared by wrapping four dip-coated sheets with silver foil. These tapes were fabricated with a melt-solidification method with a Pre-Annealing and Intermediate Rolling (PAIR) process. The local J_C distribution along the transverse direction of the tapes was determined in a nondestructive manner in which a magnetic field with a steep gradient was applied at 77 K, and the I_C was measured. The microstructures of the superconducting oxide layers were observed by using an optical micrograph and an SEM micrograph. Bi-2212 superconducting oxide layers existed on silver substrates homogeneously, and the silver/oxide interfaces were almost smooth along the silver substrates. From the J_C-profile, J_C values at the middle region on the tape were low in comparison with the J_C values in the edge regions. The depression of the J_C values around the middle region was due to the overlapping of silver foil and, hence, the inferior microstructure.