Dislocation configurations in twin-free melt-textured YBa_2Cu_3G_7 processed at high pressure and temperature

摘要

Melt-textured YBa_2Cu_3O_7 samples were deformed under high pressure-high temperature (HP-HT) conditions (P = 2GPa, T=900 and 800 deg C, t=15 min). During the HP-HT treatment, samples were in contact with annealed zirconia, preventing oxygen loss, in such a way that the orthorhombic superconductor phase was preserved at the end of the experiment. The deformed microstructure, investigated by transmitted electron microscopy, exhibited original features characterized by a very low twin density, a memory effect on the dislocations shape and a non-classical faulted loops distribution in the matrix. A mechanism, based on the interaction between twin and gliding dislocations, is proposed to explain the nucleation of these aligned loops.