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 2.3: Vortrag

Montag, 27. März 2023, 15:20–15:40, POT 51

Tuning dislocations in ferroelectric oxides by cyclic Indentation: dislocation toughening, domain fragmentation and phase stabilisation — •Oliver Preuß, Fangping Zhuo, Enrico Bruder, Christian Minnert, Jürgen Rödel, and Xufei Fang — Department of Materials and Earth Sciences, Alarich-Weiss-Str. 2, 64287 Darmstadt, Technical University of Darmstadt

In light of the growing research interest in dislocation-tuned functionality in ceramics, promising proofs-of-concept have been most recently demonstrated enhanced ferroelectric properties, electrical conductivity, and superconductivity. Yet introducing dislocations into brittle ceramics remains a grand challenge, especially at room temperature. Here, we demonstrate a simple method using a large Brinell indenter to cyclically indent the sample surface to tune the dislocation densities over 4 orders of magnitude (from 10¹⁰ m^-2 up to 10¹⁴ m^-2) in single-crystal KNbO3. A large, crack-free plastic zone ( 200 µm in diameter) is achieved on the sample surface at room temperature. More interestingly, both damage tolerance and fracture toughness have been improved. The interactions between dislocations and other microstructure features are examined in detail by optical microscopy, electron channelling contrast imaging, piezoresponse force microscopy methods and µ-Raman spectroscopy to shed light on the impact of dislocations on the mechanical properties as well as microstructural evolution. Our findings open new questions that may raise interest for further studies in ductile ceramics such as dislocation-domain wall interaction, domain wall fragmentation and strain-induced phase stabilisation.