The topological line defects, dislocations, in contrast to metals, had been avoided at all cost in ceramics for fear of implementing charge centers because they are often considered as a culprit for the degradation of ceramics.[1,2] However, recent work published in Science from our group and collaborators has demonstrated that dislocations ensured the ferroelectric BaTiO3 crystal to have a domain structure that enhanced the piezoelectric coefficient by 19 times.[3] When dislocations are interacting with topological domain walls (planar defects), they offer many new opportunities for altering functionalities by dislocation-based defect engineering.

Dislocation-based functionalities in ferroelectrics

The present project aims to investigate the influence of dislocations on dielectric and piezoelectric properties in ferroelectric BaTiO3 single crystals. These properties at both macroscopic and microscopic levels will be explored. One major aim is to understand the dynamics of the defect interactions between dislocations and domain walls and their role in determining functionalities.

The effective work will involve bulk deformation, structure and property characterizations. Dislocations will be introduced using high-temperature plastic deformation.[4] Advanced transmission electron microscope (TEM) will be employed to image the dislocation structures and their orientations. The obtained samples with dislocation networks will be characterized by investigating first and third harmonic dielectric and piezoelectric properties. Especially, local dislocation-domain wall interactions will be studied using piezoresponse force microscope (PFM).

As an MSc student, you will be trained to use the existing state of the art setups including Zwick and Instron, different microscopes as well as basic and dedicated characterization techniques, e.g., structural and ferroelectric measurements. Such an MSc experience puts you as a student in a strong position when applying for a Ph.D. globally, having been exposed to the state-of-the-art facilities TU Darmstadt has to offer.

If you are interested in this topic, please contact:

Fangping Zhuo,


[1] Hull, D. and Bacon, D. J. Introduction to dislocations. Butterworth-Heinemann, (2001).

[2] Höfling, M., Porz, L., and Rödel, J. Der innovative Fehler im Kristall: Design keramischer Piezo‐und Ferroelektrika durch Versetzungen. Physik in unserer Zeit, 53(4), 175-181 (2022).

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

[4] Höfling, M., Porz, L., Scherer, M., Gao, S., Zhuo, F., Isaia, D., and Rödel, J. High-temperature plastic deformation of <110>-oriented BaTiO3 single crystals. Journal of Materials Research, 37(3), 737-746 (2022).