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Abstract
A Landau type mean field theory of diffuse phase transition in complex perovskite relaxor ferroelectrics considering a gradual condensation of local clusters of polarizations was proposed. Numerical calculations for Pb(Mg1/3Nb2/3)O3 (PMN) and highly B-site ordered Pb(Sc1/2Ta1/2)O3 (PST) were conducted with appropriate phenomenological parameters. It was shown that, no macroscopic phase transition occurs in PMN in a short observation time scale, whereas in the case of highly ordered PST, a macroscopic first order transition occurs with the existence of the local clusters of frozen polarizations. These results confirm a picture of diffuse phase transition in relaxor ferroelectrics, the existence of local clusters and a gradual condensation of local polarizations in these clusters.
