MICROSTRUCTURE OF TEXTURED YBA2CU3O7-DELTA PREPARED BY THE MELTED ZONE IN MAGNETIC-FIELD - TEXTURATION MECHANISM

A zone melting set-up with a magnetic field perpendicular to the tempe rature gradient is used in older to optimize (a, b) plane alignment an d thus critical current densities. Large samples with high Jc values i n magnetic fields at 77K are obtained. These studies are carried out b y optical microscopy, analytical transmission electron microscopy and X ray diffraction pole figures. Our results indicate that crystallite misorientation within a single domain does not exceed 10 degrees. The application of a magnetic field of 5 T imposes the c-axis orientation during grain growth. Indeed, we observe an intergrain dispersion much smaller than 40 degrees with respect to the magnetic field direction. The 123 matrix contains large amounts of unoriented 211 inclusions whi ch are of different size.