Translational Antiphase Boundaries in NaNbO₃ Antiferroelectrics

Area of Science:

• Materials Science
• Solid-State Physics
• Crystallography

Background:

• Planar defects significantly influence material properties.
• Translational antiphase boundaries (APBs) are well-studied in perovskite oxides but underexplored in lead-free antiferroelectrics.
• Lead-free antiferroelectric oxides are crucial for next-generation energy storage.

Purpose of the Study:

• To investigate translational APBs in the lead-free antiferroelectric material NaNbO3.
• To characterize the nature, density, and stability of these APBs.
• To understand the atomistic origins of APB stability and coexistence.

Main Methods:

• Aberration-corrected scanning transmission electron microscopy (STEM) at multiple length scales.
• Ex situ and in situ transmission electron microscopy (TEM) experiments.
• Density functional theory (DFT) calculations.

Main Results:

• Translational APBs in NaNbO3 exhibit a 2-fold-modulated, antipolar structure with high density.
• These APBs demonstrate remarkable stability against electric fields and elevated temperatures.
• DFT calculations confirm the low free energy of APBs, explaining their nanoscale coexistence.

Conclusions:

• Antiphase boundaries in NaNbO3 possess a distinct antipolar character and high stability.
• The findings provide a fundamental understanding of defect behavior in NaNbO3.
• This work lays the groundwork for defect engineering of antiferroelectrics for enhanced energy storage applications.