SKM 2023 – wissenschaftliches Programm

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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 2: Focus: Dislocations in Ceramics: Mechanics, Structures and Functionality (joint session KFM/MA)

KFM 2.2: Vortrag

Montag, 27. März 2023, 15:00–15:20, POT 51

Dislocation engineering in oxides at room temperature: understanding the competition between plasticity and cracking — •Xufei Fang — Technical University of Darmstadt, Alarich-Weiss-Str. 2, 64287 Darmstadt, Germany

Dislocations in ceramic oxides are drawing increasing attention owing to their promising physical properties, such as dislocation-tuned electrical conductivity, thermal conductivity, and electro-mechanical properties. However, due to the brittleness of most oxides at room temperature, it remains a great challenge to engineer dislocations without forming cracks, which is a prerequisite for harnessing the functionalities. Here, we demonstrate dislocations can be effectively introduced into various ceramic oxides (SrTiO3, BaTiO3, KNbO3, TiO2) at room temperature by using nanoindentation pop-in stop tests. Interestingly, we find a size-dependent competition between purely dislocation-dominated plastic deformation under a critical tip radius and a concurrent appearance of cracks and dislocations when the tip radius is larger than a certain value. We further extend the deformation scale up to the millimeter regime and identify a reversal of the above size-dependent competition. We will address the underlying mechanisms by examining the dislocation nucleation, multiplication, and motion individually to shed new light on the dislocation mechanics in oxides, particularly at room temperature. Last but not least, the dislocation-tuned electrical and thermal conductivity will be briefly showcased using our developed methods for dislocation engineering.