Epitaxial Strain Control of Relaxor Ferroelectric Phase Evolution

Area of Science:

• Materials Science
• Condensed Matter Physics
• Solid-State Chemistry

Background:

• Relaxor ferroelectrics exhibit large electromechanical effects crucial for device applications.
• Controlling these effects necessitates understanding local polar order evolution under stimuli.
• Epitaxial films of 0.68PbMg1/3Nb2/3O3-0.32PbTiO3 serve as a model system.

Purpose of the Study:

• Investigate biaxial strain effects on polar structures and properties in relaxor ferroelectric films.
• Correlate structural evolution with changes in material properties under strain.
• Elucidate the mechanisms behind strain-induced modifications of local polar order.

Main Methods:

• X-ray diffuse-scattering experiments to probe polar structure evolution.
• Molecular-dynamics simulations to model strain effects and atomic-level behavior.
• Analysis of dipole alignment dynamics and correlation lengths.

Main Results:

• Biaxial compressive strain induced a transition from butterfly to disc diffuse-scattering patterns.
• Strain increased the polar correlation length from approximately 8 nm to 25 nm.
• Simulations showed strain-induced polarization rotation, merging of polar order, and gradual suppression of relaxor behavior.

Conclusions:

• Strain modifies polar order in relaxor ferroelectrics by promoting ferroelectric-like alignment in some regions while increasing disorder in others.
• This competition between ordered and disordered regions enhances overall susceptibilities.
• Tailoring local chemical configurations offers a pathway to enhance relaxor ferroelectric performance.