Fang, Xufei ; Bishara, Hanna ; Ding, Kuan ; Tsybenko, Hanna ; Porz, Lukas ; Höfling, Marion ; Bruder, Enrico ; Li, Yingwei ; Dehm, Gerhard ; Durst, Karsten (2021)
Nanoindentation pop-in in oxides at room temperature: Dislocation activation or crack formation?
In: Journal of the American Ceramic Society, 104 (9)
doi: 10.1111/jace.17806
Artikel, Bibliographie

Kurzbeschreibung (Abstract)

Most oxide ceramics are known to be brittle macroscopically at room temperature with little or no dislocation-based plasticity prior to crack propagation. Here, we demonstrate the size-dependent brittle to ductile transition in SrTiO3 at room temperature using nanoindentation pop-in events visible as a sudden increase in displacement at nominally constant load. We identify that the indentation pop-in event in SrTiO3 at room temperature, below a critical indenter tip radius, is dominated by dislocation-mediated plasticity. When the tip radius increases to a critical size, concurrent dislocation activation and crack formation, with the latter being the dominating process, occur during the pop-in event. Beyond the experimental examination and theoretical justification presented on SrTiO3 as a model system, further validation on α-Al2O3, BaTiO3, and TiO2 are briefly presented and discussed. A new indentation size effect, mainly for brittle ceramics, is suggested by the competition between the dislocation-based plasticity and crack formation at small scale. Our finding complements the deformation mechanism in the nano-/microscale deformation regime involving plasticity and cracking in ceramics at room temperature to pave the road for dislocation-based mechanics and functionalities study in these materials.

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