Cai Chuanbing

Structural characteristics and anisotropic pinning centres of MTG YBCO

The microstructure and defects in melt-textured growth (MTG) YBa2Cu3O7-x (YBCO) bulk material have been studied systematically using high-resolution transmission electron microscopy (HREM), and the relationship between the anisotropic critical current density Jc and the microstructure have been explored. The results indicate that the well-textured dense plate-shaped grains oriented parallel to the ab plane and the numerous intergrowth-type layered defects inside the plates are the two main structural characteristics in MTG YBCO. The former reduce weak links of grain boundaries, and the latter provide effective anisotropic pinning centres. The intergrowth-type layered defects parallel to the ab plane together with the well known (110) twin boundaries are responsible for the anisotropic behaviour of Jc, depending upon the orientation of the external magnetic field.