Phase development and characterization of silver-clad BSCCO superconductors

Advent of high-temperature (high-T{dollar}sb{lcub}rm c{rcub}{dollar}) superconductors has augmented considerable effort towards fabricating commercial products from these materials. Of the numerous techniques developed so far, the powder-in-tube (PIT) process along with the bismuth-strontium-calcium-copper-oxide (BSCCO) system seems to be the most promising and industrially viable method for fabricating long length conductors.; Mono- and multifilament silver-clad BSCCO tapes, fabricated by the PIT technique, were subjected to a series of thermomechanical treatment. Effort was made to optimize the various parameters involved in the process. In air, the optimum heat treatment temperature was found to be 840{dollar}spcirc{dollar}C. Highest current density (J{dollar}sb{lcub}rm c{rcub}{dollar}) of 14,000 A/cm{dollar}sp2{dollar} was achieved after 350 h of heat treatment and three round of pressing. Low current transport properties of the tapes heat treated at 830, 835, and 845{dollar}spcirc{dollar}C can be attributed to the presence of 2212 and secondary phases. Increasing the pressure during the deformation sequence seem to have only marginal influence on the current transport properties of the tapes. Growth of the 2223 phase in the tapes after each step was also studied. Phase assemblage of the precursor powder and its role in forming a transient liquid phase during sintering was determined. The mode of deformation was also found to have considerable influence on the J{dollar}sb{lcub}rm c{rcub}{dollar} of BSCCO tapes.; Strain tolerance of the tapes were determined by subjecting them to in situ tensile and bend test. Axial strain tolerance of the mono- and multifilament conductors were 0.15-0.2 and 0.2-0.6%, respectively. In the presence of a magnetic field multifilament tape exhibited a strain tolerance of 0.6-1.0%. The bend strain limit of the monofilament conductor increased with the decrease in the superconductor fill factor.; The processing parameters involved in the fabrication of high-T{dollar}sb{lcub}rm c{rcub}{dollar} superconductor were examined. Factors controlling the current transport and strain tolerance characteristics of the tapes were studied. The processing science developed in this study has been transferred to the industry for fabricating long length conductors.