Unipolar state of a ferroelectric plate with oriented polar defects

The energy density of the depolarization-field is calculated for the unipol ar state of a thin ferroelectric plate with periodic domain structure and a n arbitrary degree of unipolarity. It is assumed that the unipolar state is caused by the presence of an aligned system of polar defects in the specim en. The concentration dependence of the degree of unipolarity is establishe d, and the critical concentration of defects, giving rise to the formation of a single-domain state is determined.