Electrostatic Considerations in BaTiO3 Domain Formation during Polarization Reversal

Merz's picture of spike-shaped domains of reversed polarization emerging from an electrode is analyzed with particular attention to its electrostatic aspects, taking into account the inhomogeneous piezoelectric distortions which accompany domain formation. The depolarization energy of a domain is evaluated. The interaction energy of the applied field and the depolarization field is shown to be negligible. The charge flowing into the electrodes as a domain expands is shown to be related primarily to the reversal of spontaneous polarization, rather than to the changes of the depolarization field. Our final results are similar in form to the expression originally given by Merz. Although a detailed domain wall theory is not yet available, we have combined an existing domain wall estimate with our electrostatic expressions, and this results in an implausibly large critical nucleus. Some effects of nonlinearities in the dielectric behavior and of internal charge distributions are discussed.