Imaging 180° Polarization Reversal in Ferroelectric Oxides with Electron Backscatter Diffraction

A ferroelectric material’s permittivity is dependent on the extrinsic contribution of domain wall displacement during the application of an external field, which can involve the motion of both 90° and 180° domain walls. Directly quantifying non-180° domain structures through diffraction based techniques is generally straightforward; as the diffraction condition will be different from one side of a domain wall to the other, reflecting the rotation of the unit-cell and resulting in an easily quantifiable metric to determine location of domain wall [1]. Identifying 180° ferroelectric domains is more difficult, as Friedel’s law states that the intensity of a diffracting plane and its inverse will be equal. Fortunately, Friedel’s law is broken for dynamical scattering in a non-centrosymmetric crystal system, which is necessary for ferroelectricity. This has led to techniques such as convergent beam electron diffraction (CBED) being utilized for the characterization of 180° domain structures [1].