A STUDY ON THE MICROSTRUCTURAL DEFECTS ALONG THE A-B PLANE IN THE MELT-TEXTURED YBA2CU3OY SUPERCONDUCTOR

The microstructural defects of the melt-textured growth (MTG) YBa2Cu3O y superconductor were studied by transmission electron microscopy usin g a sample prepared such that the electron beam was parallel to the a- b plane of the material. A special planar defect with a highly disorde red atomic arrangement in it was observed. A large density of defects (10(9)-10(10) cm-2), in the forms of dislocations and stacking faults, was found in the material. [001]-type edge dislocations, and localise d crystal-plane distortion with a surrounding region of strain field w ere also observed. Many of the defects observed may act as flux-pinnin g centres and thus increase the critical current density of the superc onductor. In addition, stacking faults which were identified as the YB a2Cu4O8 (124) phase were found. Some amorphous layers were also noted on grain boundaries.