RELAXOR FERROELECTRICS IN THE RANDOM-FIELD THEORY FRAMEWORK

A model for quantitative description of the relaxer ferroelectrics pro perties in the random field theory framework is proposed. An order par ameter, phase transition temperature, critical concentration of random field sources were calculated with the help of the fields distributio n function allowing for nonlinear and spatial correlation effects. Ess ential differences were obtained in comparison with linear approach, n amely the phase transition order change, appearance of maximum in tran sition temperature T-c concentrational dependence. The comparison betw een calculated and experimental data has been made for the model ferro electric relaxer PLZT x/65/35. Fairly good agreement between calculate d and measured T-c(x) and critical concentration of lanthanum have bee n obtained.