The domain wall structure in disordered ferroelectrics

We calculate the structure of 180degrees domain wall in disordered ferroelectrics with random site electric dipoles (i.e. those like K1-xLixTaO3, KTa1-xNbxO3). The calculation is performed on the basis of a free energy functional of disordered dielectrics derived by us earlier [2] within the framework of a random local field method. We obtain the domain wall thickness as a function of impurity dipole concentration n and temperature T. It is shown that in disordered ferroelectric the domain wall is usually broader that in their ordered counterparts; the thickness increases infinitely near phase transition temperature and critical concentration of dipoles.