ON THE ROLE OF DISLOCATIONS IN HEAVILY STRAINED YBA2CU3O7-DELTA

Dense pellets of polycrystalline YBa2Cu3O7-delta have been made by sho ck compaction. While YBa2Cu3O7-delta is brittle at ambient conditions, the high pressure generated during the shock deformation is known to enhance its plasticity. Plastic deformation as well as fracture occurs when the shock wave passes through the initially loose powder, and mu ltiple defects are expected to be generated. The paper reports on the interaction of dislocations with twin boundaries, and their role in th e cleavage behaviour. The observations are performed on shock-loaded s amples, compacted at E/M ratios ranging from 0.8 to 2.3. The microstru cture of shock-compacted samples is compared to that of the initial, n on-compacted powders. Apart from the well established [100]{100} glide system, the role of the novel [110](1 $($) over bar$$ 10) and [010](1 00) glide systems is studied. All glide systems are found to interact with the ferroelastic domains of the material, each in a different way .