Twin Boundary Mediated Flexoelectricity in LaAlO$_3$

TL;DR

This study investigates how twin boundaries in LaAlO$_3$ crystals significantly influence flexoelectricity, revealing that microstructural features can enhance and modulate electromechanical responses at different temperatures.

Contribution

It provides the first quantitative analysis of twin boundary effects on flexoelectricity in LaAlO$_3$, highlighting microstructure's role in electromechanical behavior.

Findings

Twin boundary contributions are comparable to intrinsic flexoelectricity at room temperature.

Flexoelectric response is enhanced by approximately 4 times at higher temperatures.

Time-dependent and non-linear flexoelectric behaviors are linked to twin boundary polarization dynamics.

Abstract

Flexoelectricity has garnered much attention owing to its ability to bring electromechanical functionality to non-piezoelectric materials and its nanoscale significance. In order to move towards a more complete understanding of this phenomenon and improve the efficacy of flexoelectric-based devices, it is necessary to quantify microstructural contributions to flexoelectricity. Here we characterize the flexoelectric response of bulk centrosymmetric LaAlO$_3$ crystals with different twin boundary microstructures. We show that twin boundary flexoelectric contributions are comparable to intrinsic contributions at room temperature and enhance the flexoelectric response by ~4x at elevated temperatures. Additionally, we observe time-dependent and non-linear flexoelectric responses associated with strain-gradient-induced twin boundary polarization. These results are explained by considering the interplay between twin boundary orientation, beam-bending strain fields, and pinning site interactions.