Dislocations are line defects and major carriers of plastic deformation in crystalline materials. So far the understanding of dislocations in ceramics is less developed contrasting the advanced studies in metallic materials. In recent years, in light of the increasing interest in dislocation-tuned functional properties of oxides [1, 2], the dislocation-based mechanical behaviour, for instance, dislocation-mediated plasticity and dislocation toughening have also become highly relevant. Due to the brittle nature of oxides, it remains a great challenge to introduce dislocations with controlled structures without forming cracks, particularly at room temperature. In this talk, we present a simple but powerful method to introduce room-temperature dislocations into oxide SrTiO3 without crack formation by contact loading with a large Brinell spherical indenter [3]. This approach further allows us to study a variety of dislocation structure evolution including e.g., dislocation multiplication under cyclic loading and dislocation evolution at elevated temperatures due to accelerated diffusion of point defects such as oxygen vacancies. The dislocation structure evolution is further investigated to impact the mechanical properties such as hardness and fracture toughness as well as the functional properties such as thermal conductivity. The proof-of-concepts on SrTiO3 will be further validated on other oxides to showcase the general applicability of the findings.

References

[1] S. Hameed, D. Pelc, Z.W. Anderson, A. Klein, R.J. Spieker, L. Yue, B. Das, J. Ramberger, M. Lukas, Y. Liu, M.J. Krogstad, R. Osborn, Y. Li, C. Leighton, R.M. Fernandes, M. Greven, Enhanced superconductivity and ferroelectric quantum criticality in plastically deformed strontium titanate, Nature Materials, 21 (2022) 54-61.

[2] M. Höfling, X. Zhou, L.M. Riemer, E. Bruder, B. Liu, L. Zhou, P.B. Groszewicz, F. Zhuo, B.-X. Xu, K. Durst, X. Tan, D. Damjanovic, J. Koruza, J. Rödel, Control of polarization in bulk ferroelectrics by mechanical dislocation imprint, Science, 372 (2021) 961-964.

[3] C. Okafor, K. Ding, X. Zhou, K. Durst, J. Rödel, X. Fang, Mechanical tailoring of dislocation densities in SrTiO3 at room temperature, Journal of the American Ceramic Society, 105 (2022) 2399-2402.