Interpreting HRTEM Images

Here is a HTEM picture of grain boundaries in BaTiO3, one of the most important electroceramic materials. Its lattice is of the Perovskite type and looks like this:
Perovskite lattice
The Ti atom is in the center and the O atoms on the face centers positions. The lattice is not exactly cubic but slightly elongated. A HRTEM image from Prof. Urbans group (Res. Center Jülich) shows many grain boundaries:
The link provides a large-size copy. Can you figure out the structure of the boundaries? Are there any dislocations present? This is not so much an exercise but a demonstration that even images with atomic resolution do not solve all problems.

With frame With frame as PDF

go to Ionic Crystals

go to 8.3.1 Steps in Interfaces

go to Grain Boundaries in BaTiO3 - Large Size

© H. Föll (Defects - Script)