Project Details
Projekt
Correlating structure and energy landscape of perovskite oxide grain boundaries
Applicant
Professor Dr. Christian Jooss
Subject Area
Experimental Condensed Matter Physics
Term
since 2021
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 428906592
The development of a fundamental understanding of the correlation between crystal structure, point defects and extended defects and their impact on the energy landscape for ion migration is of great importance for many applications of perovskite oxides. The focus of this project is to investigate the relationship between the atomic and chemical structure of grain boundaries, their space charge zones and the site energies resp. migration barriers of the ions. In the second phase of this subproject within the research group “Energy Landscapes and Structure in Ionic Solids” (ELSIC), this relationship will be investigated on further types of grain boundaries (GB) in the model system SrTiO3 and, in addition, on GB of the solid electrolyte La0.6Sr0.4Mn1-dO3. High-resolution analytical transmission electron microscopy (TEM) is the key method, in particular scanning transmission electron microscopy (STEM), momentum-resolved (MR)-STEM for measuring electric fields and spatially resolved spectroscopic techniques (EDX, EELS). The results obtained in the first funding period show a large influence of the point defect concentration on volume diffusion and a complex relationship between grain boundary type (symmetrical, asymmetrical) and chemical structure of the grain boundary, and thus on ion migration energies. These relationships, which are extremely important for applications, will therefore be investigated in more detail, including further symmetrical and asymmetrical SrTiO3 bicrystals, other tilt angles between 6° and 30°, and also grain boundaries and heterointerfaces in sputtered bicrystalline titanate and manganate films with high point defect concentration. The diffusion profiles parallel and perpendicular to the grain boundary as well as volume diffusion are measured in collaboration with the Weitzel group in P1 using secondary ion mass spectroscopy (SIMS). A detailed understanding of the relationship between structure and chemistry of the interfaces arises from correlative microscopy using TEM in our project and tomographic atom probe (APT) in the Volkert group in project P3. The collaboration with the Jacob group in P6, using ab initio methods, allows the theoretical calculation of the site and activation energies for the determination of the energy landscape, and thus the interpretation of the diffusion experiments. In the new collaboration with the Gottfried group (P8) charge states of diffusing ions and diffusion at heterointerfaces will be studied. Another new aspect is the inclusion of the impact of dislocations on the energy landscape. This project within the research network will therefore will make a central contribution to the understanding of the impact of defects on the energy landscape of pervoskite oxides using a combination of advanced TEM methods.
DFG Programme
Research Units
