Microstructure and superconducting properties of Bi-2212/Ag tapes

In order to understand the effects of processing parameters on the formatio n of Bi-2212 phase and to improve superconducting properties, B2212 (nomina l composition Bi2Sr2Ca1Cu2Ox), sheathed with silver was fabricated and ther momechanically treated for this study. Scanning electron microscopy was emp loyed to investigate the phases and microstructure at different stages of t he Bi-2212 formation and in the final materials. A SQUID magnetometer was u sed to characterize the T-c of the conductors. Voltage-current (V-I) charac teristics were measured with a standard four-probe method at 77K in differe nt magnetic fields in order to improve the correlation of magnetic properti es to microstructural properties. The critical current density is similar t o 15,000 A/cm(2) at 77K self field. The critical current distribution in th e conductors was studied by computing the second differential of the VI cur ves and the correlation between the microstructure and the second different ial was analyzed. The current transfer to the metal sheath and the effect o f the sheath on the shape of the VI curve are discussed.