Formation of nanostructures in ferroelectrics and antiferroelectrics in   the process of phase transformation
  This paper contains results of investigations of inhomogeneous states caused by the coexistence of ferroelectric and antiferroelectric phases in lead-zirconate-titanate based solid solutions. The domains of ferroelectric and antiferroelectric phases with sizes of the order of 20 to 30 nm coexist in the bulk of the samples due to a small difference in the free energies of the phases. The coherent character of interphase boundaries leads to the concentration of elastic stresses along these boundaries. Elastic stresses cause the local decomposition of the solid solution due to the circumstance that equivalent positions of the crystal lattice are occupied by ions with different sizes. Larger ions are driven out into domains with larger crystal cell parameters and smaller ions are pushed into domains with smaller parameters of the crystal cell. The sizes of segregates formed in this way are of the order 8 to 15 nm. 
V.M. Ishchuk, N.A. Spiridonov, and V.L. Sobolev