Microstructure of the post hot pressed and room-temperature pressed Ag/Bi(2223) tapes

The microstructure of the post hot pressed Bi-2223 tapes with a J(c) of 56 000 A/cm(2) at 77 K and self-field and some tapes only pressed at room temp erature has been studied by using SEM and TEM. The tapes treated by post ho t pressing show very dense structure even in the areas in adjacent to the s econdary phases. The defects such as cracks, sub-grain boundaries,residual amorphous or intermediate phases, which limit or break the current going th rough, were reduced significantly in post hot pressed tapes. The dislocatio ns in hot pressed rape feature almost the same density and more uneven dist ribution or net structure in some region. It is found that grain boundary c an capture some dislocations in certain direction moving across it. The hot pressing promotes the transformation of the second phases into Bi2223 and improves the current-carrying capacity of the tapes. (C) 2000 Elsevier Scie nce B.V. All rights reserved.