MICROSTRUCTURES IN HIGH-J(C) TL-1223 AG TAPES

High-T-c Tl-1223/Ag tapes with a nominal composition of (Tl0.93Bi0.22) (Sr1.6Ba0.4)Ca2Cu3Ox were prepared using the powder-in-tube method com bined with the two step reaction method, Their microstructures were ex amined using scanning and transmission electron microscopy. Tape A (J( c) = 5500 A/cm(2) at 77 K under 0 T) prepared using rolling only has a lower J(c) than tape B (J(c) = 14000 A/cm(2)) prepared using pressing . In both tapes Tl-1223 forms plate-like grains. Although the size of the plates in tape A is larger than those in tape B, their mutual conn ection is poorer, Many subgrains are formed in each grain with small a ngle boundaries, which are composed of tilt-type as well as twist-type components in most cases. The boundaries might be considered as effec tive pinning sites for magnetic flux as far as the tilt component pred ominates, Additionally, small holes were found at the subgrain boundar ies.