DIFFERENT TYPES OF DISLOCATIONS IN YBA2CU3O7-DELTA

In the present study, dense pellets of polycrystalline YBa2Cu3O7-delta were made by dynamic powder compaction. The shock wave, which passes through the initially loose powder, generates multiple defects. Its hy drostatic component suppresses the brittle nature of YBa2Cu3O7-delta, and so plastic deformation such as dislocation generation and glide is expected. This paper reports on the characterization of structure def ects observed in shock loaded samples, compacted at E/M ratios ranging from 0.8 to 2.3. The microstructure of shock compacted samples is com pared to that of the initial, noncompacted powders. Apart from the wel l-established [100](001) glide system, two additional glide systems ha ve been identified: [110](110BAR) and [010](100). They are characteriz ed both by diffraction contrast and high-resolution transmission-elect ron-microscopy techniques. The interaction between the different types of dislocations and other structure defects, as well as their role in cleavage and stacking fault generation is investigated. Finally, the possible role in flux pinning of the dislocation types is briefly disc ussed.