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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 9: KFM Poster Session

KFM 9.34: Poster

Montag, 18. März 2024, 18:00–20:00, Poster E

Antiferrodistortive rotations at grain boundaries in SrTiO₃ — •Pavlína Kružíková^1,3 and David R. Bowler^2,3 — ¹Bundesanstalt für Materialforschung und -prüfung (BAM), Berlin, Germany — ²London Centre for Nanotechnology, London, UK — ³Department of Physics and Astronomy, UCL, London, UK

A typical property of SrTiO₃ perovskite oxide, namely the antiferrodistortive (AFD) rotations, is not yet being taken advantage of in applications. This is because it is usually only present at temperatures lower than 105 K, i.e., below the phase transition temperature. This situation could change after an experiment detected AFD rotations at a Σ13 (510) grain boundary in SrTiO₃ at room temperature. Such temperature would allow for practical optical or electrical applications, together with the potential to use grain boundary defects for tuning the materials properties. The open source DFT code CONQUEST was used to perform cell and ionic relaxations as well as post processing, with the goal of obtaining the atomic and electronic structure of this SrTiO₃ grain boundary and further insights about the AFD mechanism. Several related systems were also studied to compare the findings, e.g., the Σ13 (210) grain boundary, SrTiO3 bulk with AFD rotations and SrTiO₃ bulk with O vacancies. The obtained atomic structure matches the AFD rotations detected in experiment. Additionally, an in-plane ferroelectric displacement was identified. In the electronic structure, localised states were found at the bottom of the conduction band in the grain boundary core. Out of all studied systems, these findings were specific to this grain boundary type.

Keywords: DFT; grain boundary; antiferrodistortion; perovskite oxide