Properties of grain boundaries

We investigate the structure and energy landscape at perovskite oxide grain boundary (GB) and the changes due to cation diffusion. The goal is to understand charge carrier transport at extended defect and near space charge layers.

High resolution (scanning) transmission electron microscopy is a powerful tool to study the structure as well as the electric potential of grain boundaries, e.g., in high-temperature superconductors like Ca-doped YBaCuO. The reconstructed phase images of a grain boundary dislocation reveal a doping-dependent negative GB potential, indicating an insulating phase in the dislocation core.

We study K+ diffusion in SrTiO3 in collaboration with the Phillips-Universität-Marburg (within DFG research unit ELSIC). Simulation of potassium concentration profiles indicates enhanced diffusion in grain boundaries like the 36° twin boundary.