Current–voltage curves and critical current densities of monocore Ag-clad (Bi, Pb)2Sr2Ca2Cu3O10+x tapes for currents applied perpendicular and parallel to the tape plane

Abstract

We analysed I–V curves of a monocore, Ag-clad (Bi, Pb)2Sr2Ca2Cu3O10+x tape measured with current flowing perpendicular to its broad face. The measurements showed that the boundary superconductor/Ag has a resistive character. We have also found that in this experimental configuration the edges of the core connecting its upper and lower surface layer influence I–V curves in a decisive way. For the sample prepared from the original tape with an intact core and Ag edges, the shape of the I–V curves measured with perpendicular current was similar to those measured with current flowing parallel to the tape axis. The shape of the I–V curves for perpendicular current drastically changed if we interrupted the connections between the surface core layers by cutting off the core edges. The observed I–V curves exhibited two bends indicating the presence of two layers with two different critical current densities in the direction perpendicular to the broad face of the core. The higher Jc was 270 A cm−2 and the lower one was 150 A cm−2 (in zero external magnetic field at 77 K). Both Jc values were considerably lower than the value of Jc = 1 × 104 A cm−2 measured with current flowing parallel to the tape axis.