COMPARATIVE-STUDIES ON SINGLE-CRYSTALS AND SUPERCONDUCTING BI-(PB)-SR-CA-CU-O TAPES

Comparative studies on Bi-2212 single crystal Bi-2212 tape and 2223 ta pe have been carried out using at susceptibility, magnetisation and ma gnetoresistivity measurements. Bi-2212 crystals have been obtained thr ough a spiral growth mechanism using KCl as flux. Magnetisation measur ements show an enhanced flux pinning in the spiral grown crystals comp ared with crystals grown through a layer-by-layer mechanism. The fish tail effect in M-H loop is attributable to the spirals and strew dislo cations in spiral grown Bi-2212 crystals. The irreversibility line for the 2223 tape is positioned at higher temperatures than that for the 2212 tape which is in turn positioned at higher temperatures than that for the 2212 crystals. The pinning potential, U-o, for 2212 tape, det ermined by using resistance measurements in magnetic fields, is smalle r than that of Ag/Bi-2223 tapes but larger than that for 2212 single c rystal. These results indicate that the defects induced by mechanical deformation or spiral growth act as pinning centers in Bi-based materi als, responsible for the improvement in flux pinning.