Room-temperature ferroelectricity in NaNbO₃ membrane.

Area of Science:

• Materials Science
• Solid State Physics
• Nanotechnology

Background:

• Sodium niobate (NaNbO₃) is known as an antiferroelectric material with potential in energy storage and electromechanical applications.
• Controlling ferroic orders, especially the antiferroelectric-to-ferroelectric phase transition, is crucial for harnessing NaNbO₃'s capabilities.

Purpose of the Study:

• To develop a fabrication strategy for pure ferroelectric NaNbO₃ membranes with controlled phase and thickness.
• To investigate the ferroelectric mechanism, piezoelectric properties, and resistance switching behavior of the synthesized membranes.

Main Methods:

• A topochemical conversion strategy using a molten salt environment was employed for synthesis.
• Scanning transmission electron microscopy (STEM) was used to analyze octahedral tilts.
• Polarization analyses were conducted to understand the origin of ferroelectricity.

Main Results:

• Pure ferroelectric NaNbO₃ membranes with a P2₁ma orthorhombic phase were successfully fabricated, independent of membrane thickness.
• Two distinct regions with varying octahedral tilts were identified, with ferroelectricity attributed to out-of-plane Nb⁵⁺ displacement.
• Thickness-dependent piezoelectric enhancement was observed, reaching a d₃₃ of 93.7 pm/V at 30 nm, alongside significant resistance switching.

Conclusions:

• The study presents an innovative molten salt synthesis for high-quality pure ferroelectric NaNbO₃ membranes.
• The findings advance the integration of NaNbO₃ into next-generation functional devices due to its enhanced properties.