Anisotropic dislocation-domain wall interactions in ferroelectrics

Fangping Zhuo ¹ Xiandong Zhou ¹ Shuang Gao ¹ Marion Höfling ² Felix Dietrich ³ Pedro B. Groszewicz ⁴ Lovro Fulanović ¹ Patrick Breckner ¹ Andreas Wohninsland ¹ Bai-Xiang Xu ¹ Hans-Joachim Kleebe ¹ Xiaoli Tan ⁵ Jurij Koruza ⁶ Dragan Damjanovic ⁷ Jürgen Rödel ¹

¹Department of Materials and Earth Sciences, Technical University of Darmstadt, Darmstadt, Germany
²Department of Physics, Technical University of Denmark, Kgs. Lyngby, Denmark
³Institute of Physical Chemistry, Technical University of Darmstadt, Darmstadt, Germany
⁴Department of Radiation Science and Technology, Delft University of Technology, Delft, Netherlands
⁵Department of Materials Science and Engineering, Iowa State University, Ames, USA
⁶Institute for Chemistry and Technology of Materials, Graz University of Technology, Graz, Austria
⁷Institute of Materials, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland

Defects are prevalent in modern technology, but the most common one-dimensional (1D) topological defects, dislocations, are often perceived as a culprit for degradation in functionality of ceramics [1]. Over decades, continuous efforts have been made to engineer 1D dislocations with multiscale defects in materials ranging from semiconductors to superconductors [2]. Perhaps less widely appreciated, when dislocations are interacting with two-dimensional (2D) topological domain walls (planar defects), they offer a large potential to engineer multiscale defects of functional materials. For example, we demonstrated that introducing dislocations to BaTiO₃ single crystals enhances the large-signal piezoelectric coefficient by 19-fold [3].

Here, by establishing the geometric line-plane relationships, we introduce a general framework for engineering 1D dislocation and 2D domain walls, and demonstrate its full potential on a prototypical ferroelectric BaTiO₃ single crystal. We explored a different method using controlled plastic deformation to mechanically embed directed mesoscopic 1D dislocation networks in anisotropically distributed 2D domain walls. Mathematically, for our case of directional imprint, this signifies an elevation of rank of piezoelectric tensor by combining it with the 2D strain field of the dislocations. Our 1D-2D defect approach therefore yields extraordinary and stable large-signal dielectric permittivity (≈ 23100) and converse piezoelectric coefficient (≈ 2470 pm V^–1) [4]. Even more, we are able to directly control anisotropic electromechanical properties by taking full use of dislocation-domain wall interactions based on domain-wall pinning force anisotropy. Our findings were supported by detailed transmission electron microscopy, time- and cycle-dependent nuclear magnetic resonance paired with X-ray diffraction, and detailed electrical characterization as well as extensive phase-field simulations. The concept of 1D-2D approach can be easily transferred to other materials and is opening a new door for dislocation-tuned functional materials.

Reference

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

[2] S. Hameed, et al. Enhanced superconductivity and ferroelectric quantum criticality in plastically deformed strontium titanate. Nature Materials 21, 54–61 (2022).

[3] M. Höfling, et al. Control of polarization in bulk ferroelectrics by mechanical dislocation imprint. Science 372, 961–964 (2021).

[4] F. Zhuo, et al. Anisotropic dislocation-domain wall interactions in ferroelectrics. Nature Communications, accepted (2022).