Switching and dielectric nonlinearity of ferroelectric ceramics

The switching of the polarization in tetragonal ferroelectric ceramics can be achieved by the generation of one new 90° domain wall at the boundary of every grain and a transit of it through the grain driven by the electric field. This transient domain wall is perpendicular to the regular 90° domain walls. In any domain of the grain then the polarization is rotated by 90° and the average polarization of the grain is rotated by 180° due to the specific domain configurations. The observed relationship E0 ∼ P3 0 between the spontaneous polarization P 0 and the coercive field E 0 is confirmed by the model. The dielectric nonlinearity of ferroelectric ceramics can also be explained by the new 90° domain walls which have a very high mobility. Possibly the high permittivity of fine grained Barium Titanate can be attributed to these domain walls too.