THEORY OF THE NONSTOICHIOMETRIC 1 1-SHORT-RANGE ORDERING IN PB(B'1/3B'')O-3-TYPE RELAXOR FERROELECTRICS/

It is known that the B-site compositional fluctuation caused by the fo rmation of the nonstoichiometrically 1:1 ordered nanodomains is mainly responsible for the diffuse phase transition (DPT) behavior in Pb(B-1 /3'B-2/3'')Oa-type perovskites. A new theory of the 1:1 short-range or dering was developed to explain the observed inability of the coarseni ng of the ordered domains beyond nanometer scale. It was shown that bo th the dispersion entropy associated with the formation of negatively charged ultrafine domains and the mode of the counter-ion distribution at the domain/matrix interface played a significant role in controlli ng the equilibrium ordered domain size.