INTRODUCTION OF THE ULTRAFINE MGO TO THE HIGH T-C MELT-TEXTURE YBA2CU3O7-DELTA

The MgO ultrafine powder was prepared by the common Sol-Gel process. D etermined by the line width at half-height of powder X-ray diffraction , the MgO powder was about 20nm in size on average. A supersonic vibra tion was introduced to destroy the accumulation of the ultrafine powde r and to mix the powder with the YBa2Cu3O7-delta precursor. The melt-p rocess was employed to grow textured samples. From the Scanning Electr on Microscope (SEM) graphs, some particles were found in the textured samples, which were about several nanometer in size. The composition o f these particles, however, leaves to be identified. The magnetic crit ical current density (J(cm)) at 77K dropped rapidly with the increase of Mg content.