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

Bulk superconducting YBa/sub 2/Cu/sub 3/O/sub 7/-Y/sub 2/BaCuO/sub 5/ composites have been prepared through a directional solidification process allowing to obtain quasi-single crystals up to 10-12 cm in length with critical currents well above 10/sup 5/ A/cm/sup 2/ 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 effects, as well as the microstructure of the samples, made evident through a careful transmission electron microscopy (TEM) investigation.<>