Optimization of Bi-2223 Tape Fabrication Procedure With Help Of Magneto-Optical Imaging

Abstract

A set of Ag-sheathed Bi-2223 (Bi_1.72Pb_0.34Sr_1.85Ca_1.99Cu₃O_x) tapes was produced using the powder in tube technique and two heat treatments separated by a mechanical deformation. For the second heat treatment, a two step annealing process was used with the first step at 825°C and the second at different temperatures from 725 to 800 ° C, an additional tape was produced by a slow cooling ramp after annealing at 825 ° C. These tapes were studied by the way of magneto-optical imaging (MOI). This “local’ technique provides results which correlate and clarify the results obtained by other “global” techniques (XRD, magnetization, critical current J_c, critical temperature T_c). The MO results show better superconducting properties (higher J_c, good shielding properties) for the slow cooled sample and for the sample which was annealed at 750 ° C during the second step.