Direct observation of discommensurate walls in Bi-Ca-Sr-Cu-O superconductors

Abstract
The dislocations and twins in superconducting Bi-Ca-Sr-Cu-O samples are examined by scanning electron microscopy and transmission electron microscopy. The results indicate that these defects are inherent to the materials. The grains are large in size (1–10 μm), but they are frequently divided into subgrains by low-angle grain boundaries. Furthermore, evidence is found for discommensurate walls associated with incommensuration along the b axis.