TEM Study of hot deformation effects on (Bi,Pb)(2)Sr2Ca2Cu3Ox silver-sheathed tapes

The microstructural effects of deformation at high temperatures on silver-sheathed (Bi,Pb)(2)Sr2Ca2Cu3Ox tapes have been studied by means of transmission electron microscopy. Hot deformation is found to cause bending of the grains by introducing dislocations apparently without generating cracks. Short-time deformation raises the dislocation density by one order of magnitude and yields higher dislocation densities compared to long-time deformation. The observed dislocations mainly have 1/2[110] Burgers vectors and form irregular networks, both before and after the hot deformation. The significantly increased critical current density of hot deformed tapes can be explained by the introduction of the observed defect structures, which are potential flux pinning sites.