Enabling nanoscale flexoelectricity at extreme temperature by tuning cation diffusion.

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Flexoelectricity, the generation of electric polarization in response to a strain gradient, is a property of all dielectric materials.
• Understanding flexoelectric effects in nanomaterials is crucial for developing advanced electronic devices operating under extreme conditions.

Purpose of the Study:

• To investigate the occurrence and characteristics of flexoelectricity in core-shell nanoparticles at high temperatures.
• To explore the role of chemically induced strain gradients in enabling switchable polarization beyond conventional temperature limits.

Main Methods:

• Synthesis of 0.75 sodium bismuth titanate–0.25 strontium titanate (NBT-25ST) core-shell nanoparticles using a solid-state reaction within a transmission electron microscope (TEM).
• In situ TEM observations at temperatures up to 800°C to monitor domain-like nanoregions (DLNRs).
• Electrical biasing, temperature-dependent analysis, and phase field simulations to study strain gradients and local polarization.

Main Results:

• Observation of DLNRs in NBT-25ST nanoparticles up to 800°C, attributed to chemically induced lattice strain gradients.
• Demonstration that controlled strontium cation diffusion generates the strain gradient, leading to flexoelectricity.
• Confirmation of local symmetry breaking due to strain gradients as the mechanism for switchable polarization at high temperatures.

Conclusions:

• Flexoelectricity can induce switchable polarization in nanomaterials at extreme temperatures.
• Tuning cation diffusion in core-shell structures is a viable strategy to achieve flexoelectric effects at high temperatures.
• This research opens possibilities for novel polar nanomaterials operating under demanding thermal conditions.