SKM 2023 – scientific programme

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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 4: Focus: Domains and Domainwalls in (Multi)Ferroic II

KFM 4.3: Talk

Tuesday, March 28, 2023, 09:50–10:10, POT 51

3D mapping of grain boundary chemistry in ferroelectrics — •Kasper Hunnestad, Jan Schultheiss, Anders Mathisen, Constantinos Hatzoglou, Antonius Helvoort, and Dennis Meier — Norwegian University of Science and Technology (NTNU), 7491 Trondheim, Norway

In this work, we study the impact of polar order on the local chemistry of charged grain boundaries, which naturally form in polycrystalline pyro- and ferroelectric materials during processing. Analogous to ferroelectric domain walls, these interfaces can develop new physical properties, representing intriguing functional 2D systems. Understanding the origin of the emergent interfacial phenomena, however, is a challenging task, requiring high-resolution imaging of the atomic-scale structure.

Here, we apply atom probe tomography (APT) to study the local chemistry at grain boundaries in ferroelectrics. APT combines high chemical sensitivity and accuracy with three-dimensional spatial resolution, allowing to map and quantify otherwise inaccessible changes in chemical composition. In our polycrystalline model system, ErMnO3, we consistently find an enrichment of erbium and a depletion of oxygen at the grain boundaries. This trend occurs independently of the local charge state of each grain boundary and is unexpected as it implies a local violation of charge neutrality. Our results provide new insight into the defect chemistry at the grain boundaries in polar materials, suggesting pathways for local property engineering in ferroelectric oxides via grain-boundary-selective doping.