Structure and misorientation angle distributions of (001) twist grain boundaries in Bi_2Sr_2Ca_1Cu_2O_y,/Ag composite tapes processed in different oxygen partial pressures

摘要

We investigated the relationship between the structure and misorientation angle of (00l) twist grain boundaries in Bi2Sr2CalCu2Oy/Ag composite tapes processed in different oxygen partial pressures (Po2 = 0.0l, 0.21, and l atm). Large-angle misoriented twist boundaries (> l0 deg) essentially had no amorphous layers at the interface, and the misorientation angles of these boundaries mostly corresponded to low-energy misorientations. This large-angle misoriented boundary structure was independent of Po2, Small-angle misoriented twist boundaries (< l0 deg), on the other hand, corresponded to high-energy misorientations and sometimes had amorphous layers at the interface. The population of the small-angle boundary with an amorphous layer was very low in the tape processed in Po2 = l atm. This suggests that high Po, during the heat treatment is effective in the improvement of grain coupling, and hence, to increase critical current density.