TimeMan Seminar - Xufei FANG

Room-temperature Dislocations in Oxides: Understanding, Engineering, and Application

Dr. Xufei Fang

Department of Materials and Earth Sciences, Technical University of Darmstadt, 64287, Darmstadt, Germany

Abstract

In light of the increasing interest in dislocation-tuned functional properties of oxides [1, 2], the dislocation-based mechanical behaviour, for instance, dislocation plasticity and potentially the crack formation induced by dislocation pileup is also drawing increasing attention. Due to the brittle nature of oxides, it remains a great challenge to introduce dislocations with controlled structures into oxides without forming cracks. Understanding the dislocation-based mechanics in oxides plays a critical role in tackling such a challenge as well as assessing the mechanical and functional reliability of future dislocation-based devices. In this talk, I will focus on room-temperature dislocation mechanics in oxides and present a feasible roadmap to first understand the dislocation behaviour (dislocation nucleation, multiplication, and motion), then to actively tailor the dislocation-mediated plasticity in a model oxide (SrTiO₃) by combining nanoindentation [3], micro-pillar compression, bulk indentation, and scratching tests across the length scales. Several protocols and concepts for experimental design such as defect chemistry engineering [4, 5], cyclic indentation tests [6], surface dislocation engineering will be demonstrated to tailor the dislocation plasticity and, more strikingly, the damage tolerance as well as the fracture toughness of oxide crystals. The proof-of-concepts on SrTiO₃ will be further validated on other oxides to showcase the general applicability of our findings. In addition to mechanics, I will also showcase some examples of dislocation-enhanced functional properties based on the dislocation engineering approaches.

References

[1] M. Höfling, et al., Science 372 (2021) 961-964.

[2] S. Hameed, et al., Nature Materials 21 (2022) 54-61.

[3] X. Fang, et al., Scripta Materialia 188 (2020) 228-232.

[4] X. Fang, et al., Journal of the American Ceramic Society 104 (2021) 4728-4741.

[5] S. Stich, X. Fang, et al., Journal of the American Ceramic Society 105 (2022) 1318-1329.

[6] C. Okafor, X. Fang, et al., Journal of the American Ceramic Society 105 (2022) 2399-2402.