Significantly enhanced critical current density in Ag-sheathed (Bi,Pb)2Sr2Ca2Cu3Ox composite conductors prepared by overpressure processing in final heat treatment

Overpressure (OP) processing otherwise fully treated, commercial Ag-sheathed multifilament (Bi,Pb)(2)Sr2Ca2Cu3Ox (2223) composite conductors increased the critical current density J(c) (0.1 T, 77 K) by 37% to 30.8 kA/cm(2) and the self-field J(c) (SF, 77 K) to 69.6 kA/cm(2). These improvements were obtained on full-size high current conductors such that critical current I-c (0.1 T, 77 K) reached 80.6 A and I-c (SF, 77 K) 181.7 A, even though there was a very strong self-field suppression of I-c. Estimated values for the non-self-field-limited I-c and J(c) (0 T, 77 K) reached 235 A and 90 kA/cm(2). Scanning electron microscopy and superconducting quantum inference device measurement revealed that OP processing effectively suppressed cracks, porosity, and the volume fraction of the Bi2Sr2Ca1Cu2Oy (2212) phase, which are all major current-limiting mechanisms in present 2223 conductors. (C) 2004 American Institute of Physics.