Engineering of atomic-scale flexoelectricity at grain boundaries

Area of Science:

• Materials Science
• Solid-State Physics
• Nanotechnology

Background:

• Flexoelectricity describes the electrical polarization response to mechanical strain gradients, a phenomenon not limited by material symmetry.
• Achieving large elastic deformations and controlling minuscule strain gradients in solids is typically challenging.
• Grain boundaries in materials offer unique structural inhomogeneity.

Purpose of the Study:

• To investigate the potential of grain boundary structural inhomogeneity for generating large strain gradients.
• To achieve and quantify atomic-scale flexoelectric polarization.
• To explore the tunability of flexoelectricity through grain boundary engineering.

Main Methods:

• Exploiting the structural inhomogeneity of grain boundaries to create huge strain gradients (~1.2 nm⁻¹).
• Utilizing atomic-scale analysis to measure flexoelectric polarization (~38 μC cm⁻²).
• Investigating the impact of grain boundary misorientation angles on strain gradients.

Main Results:

• Achieved a huge strain gradient within 3-4 unit cells at a 24° LaAlO₃ grain boundary.
• Obtained atomic-scale flexoelectric polarization up to ~38 μC cm⁻².
• Demonstrated that altering grain boundary misorientation angles allows for tunable strain gradients.

Conclusions:

• Flexoelectric effects at grain boundaries are crucial for understanding the electrical activities of oxide ceramics.
• Engineering grain boundaries provides a general and feasible pathway for achieving tunable atomic-scale flexoelectricity.
• This approach opens new avenues for designing materials with tailored electromechanical properties.