The investigation of the orthorhombic superconductor $\mathrm{Y}{\mathrm{Ba}}_2{\mathrm{Cu}}_3{\mathrm{O}}_{7\pm \epsilon }$ by high-resolution electron microscopy (HREM) shows the existence of two sorts of domains: twinned domains and oriented domains forming slices perpendicular to the $c$ axis. The interpretation of these domains and of their boundaries is given, based on the simulated HREM images previously made. It is shown that the orientation of the ${\left(\mathrm{Cu}{\mathrm{O}}_2\right)}_{\infty }$ planes formed by the Cu${\mathrm{O}}_4$ square planar groups plays an important role. A phenomenon of misorientation of those domains is also observed and interpreted.

• Received 21 May 1987

DOI:https://doi.org/10.1103/PhysRevB.36.3920