Current-voltage characteristics of BSCCO-2212 wires and BSCCO-2223 tapes

BSCCO-2212 wires and BSCCO-2223 tapes have been prepared using the conventional powder in tube method but with an alternative rolling prozess instead of drawing. As a standard characterization J(c) was measured at 77 K. Critical current densities of 25 000 A/cm(2) for the BSCCO-2223 tapes and 5 000 A/cm(2) for the BSCCO-2212 wires were obtained at 77 K. In order to examine the pinning properties current-voltage characteristics have been measured at temperatures between 4.2 K and 100 K in magnetic fields up to 8 T. At temperatures below 40 K respectively 20 K for the 2212-phase the magnetic field dependence of the critical current density is weak after an initial drop. At higher temperatures the critical current density decreases exponentially at magnetic fields above 1 T. In this region the I-V-characteristics show power law behavior as ecpected for the thermally activated flux flow (TAFF) mechanism. The anisotropy of J(c) for different orientations of the magnetic field is high for the tape material and nearly zero for the wires as expected from the 2-d structure of the material and the geometry of the samples.