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Enabling nanoscale flexoelectricity at extreme temperature

Enabling nanoscale flexoelectricity at extreme temperature Any dielectric material under a strain gradient presents flexoelectricity. In this work researchers from TU Darmstadt synthesized the core–shell nanoparticles of 0.75 sodium bismuth titanate −0.25 strontium titanate (NaBiTi-25SrTi) via a solid-state chemical reaction directly inside a transmission electron microscope (TEM).

Domain-like nanoregions found in the core-shell nanoparticles at room temperature were still observed up to an extreme temperature of 800 °C. This abnormal phenomenon was attributed to a chemically induced lattice strain gradient present in the core–shell nanoparticle, caused by diffusion of strontium cations.

By combining electrical biasing and temperature-dependent in situ TEM with phase field simulations, we analyzed the resulting strain gradient and local polarization distribution within a single nanoparticle. The analysis confirms that a local symmetry breaking, occurring due to a strain gradient (i.e. flexoelectricity), accounts for switchable polarization beyond the conventional temperature range of existing polar materials.
(Nature Communications 9, Article number: 4445 (2018)

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