Flexoelectric Polarization Enhancement in Paraelectric BaHfO₃ via Strain Gradient Engineering

Area of Science:

• Materials Science
• Solid State Physics
• Dielectric Materials

Background:

• Flexoelectricity enables polar effects in centrosymmetric materials lacking piezoelectricity.
• BaHfO3 (BHO) is a centrosymmetric, paraelectric perovskite suitable for studying flexoelectricity.
• Epitaxial BHO films can exhibit significant intrinsic strain gradients.

Purpose of the Study:

• Investigate the flexoelectric effect in epitaxial BaHfO3 thin films.
• Quantify the enhancement in spontaneous polarization due to strain gradients.
• Isolate and understand flexoelectric coupling in BHO.

Main Methods:

• Epitaxial growth of BaHfO3 thin films.
• Characterization of strain gradients using high-resolution techniques.
• Measurement of spontaneous polarization under applied electric fields.
• Analysis to distinguish flexoelectric effects from ferroelectric and piezoelectric contributions.

Main Results:

• Coherently grown BHO films develop intrinsic strain gradients >10^5 m^-1.
• A 29-fold enhancement in spontaneous polarization was observed at 4 MV cm^-1 in strained BHO compared to relaxed BHO.
• Flexoelectric coupling was successfully isolated due to BHO's centrosymmetric nature and lack of phase transitions.

Conclusions:

• Engineered strain gradients significantly enhance polarizability in oxide thin films.
• BHO serves as a benchmark system for studying flexoelectricity.
• Findings support the use of flexoelectricity in dielectric devices and advance understanding of strain-coupled phenomena.