Ferroelectric transition in a random field: Possible relation to relaxor ferroelectrics

Abstract

Ferroelectric phase transition developing in a random field of static defects is studied by the computer simulation method. The chosen free energy provides the stability of the ferroelectric phase in the absence of defects. The simulation model takes into account the transformation-induced strain and the dipole—dipole interaction. It is shown that the ferroelectric transition in a random field produces the two-phase thermoelastic metastable equilibrium rather than the single-phase ferroelectric state. The metastable state is a dispersion of ferroelectric clusters in the paraelectric matrix. The clusters formation mechanism is discussed in terms of the percolation theory. Increase in the transformation driving force transforms the cluster dispersion to the ferroelectric macrodomain state. The theoretical prediction of comparatively stable polar clusters in the paraelectric matrix in relaxor ferroelectrics provides an additional footing for the superparaelectric origin of unusual properties of the relaxor ferroelectrics.