Atomic scale symmetry and polar nanoclusters in the paraelectric phase of ferroelectric materials.

ABSTRACT: The nature of the "forbidden" local- and long-range polar order in nominally non-polar paraelectric phases of ferroelectric materials has been an open question since the discovery of ferroelectricity in oxide perovskites, ABO₃. A currently considered model suggests locally correlated displacements of B-site atoms along a subset of <111> cubic directions. Such off-site displacements have been confirmed experimentally; however, being essentially dynamic in nature they cannot account for the static nature of the symmetry-forbidden polarization implied by the macroscopic experiments. Here, in an atomically resolved study by aberration-corrected scanning transmission electron microscopy complemented by Raman spectroscopy, we reveal, directly visualize and quantitatively describe static, 2-4 nm large polar nanoclusters in the nominally non-polar cubic phases of (Ba,Sr)TiO₃ and BaTiO₃. These results have implications on understanding of the atomic-scale structure of disordered materials, the origin of precursor states in ferroelectrics, and may help answering ambiguities on the dynamic-versus-static nature of nano-sized clusters.

SUBMITTER: Bencan A 

PROVIDER: S-EPMC8175364 | biostudies-literature | 2021 Jun

REPOSITORIES: biostudies-literature