Optics

Physics

Dielectric

Transmission electron microscopy

Physical chemistry

Chemical physics

Nanotechnology

Chemistry

Materials science

Scanning transmission electron microscopy

Polarization (electrochemistry)

Condensed matter physics

Nanoclusters

Polar

Raman spectroscopy

Molecular physics

Phase (matter)

Optoelectronics

Quantum mechanics

Atomic units

Ferroelectricity

Nature Communications

The nature of the "forbidden" local- and long-range polar order in nominally nonpolar 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 offsite 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 (STEM) complemented by Raman spectroscopy, we reveal, directly visualize and quantitatively describe static, 2-4 nm large polar nanoclusters in the nominally nonpolar 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.

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