Influence of the oxygenation process in the critical currents of bulk melt textured YBa/sub 2/Cu/sub 3/O/sub 7/

Abstract

Bulk superconductingYBa2CugO7-Y2BaCu05 composites have been prepared through a directional solidiJcation process allowing to obtain quasi-single crystals up to 10-12 cm in length with critical currents well above lo5 A/cm2 at 77 K and zero field. Low temperature oxygenation processes have been required to reach the optimal superconducting performances of the samples. For short oxygenation times, oxygen deficient bands parallel to the a-b planes have been observed while, on the other hand, an aging process has also been detected at long oxygenation times. We show that the critical currents and irreversibility lines are strongly influenced by these efsects, as well as the microstructure of the samples, made evident through a careful transmission electron microscopy (TEM) investigation.

Tailoring of microstructure and critical currents in directionally solidified

“…We have shown that in melt-textured 123-211 composites dark bands, typically 50-100 µm wide, develop parallel to the ab planes and their width is controlled by the duration of the oxygenation process [115,116]. Low-field zero-field cooling (ZFC) measurements allow us to identify these dark bands with oxygen-deficient areas (see figure 8), since in the H ab geometry full shielding is reached only when supercurrents cross these poorly oxygenated zones.…”