The behavior of the 180° domain walls in disordered dielectrics like KTaO3 : Li and KTaO3 : Nb

We calculate the structure of 180° domain wall in disordered ferroelectrics with random site electric dipoles (i.e. those like K 1-x Li x TaO 3 , KTa 1-x Nb x O 3 , where Li + or Nb 5+ are off-center ions forming impurity dipoles). The calculation is performed on the base of the free energy functional of disordered dielectrics derived earlier [M. D. Glinchuk et al., Phase Transit., 2003 (to be published)] within the framework of a random 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 ferroelectrics the domain wall is usually broader than in their ordered counterparts. The thickness increase…