DIMENSION AND SIZE EFFECTS IN FERROELECTRICS

The characteristic sizes of perovskite ferroelectrics have been examin ed by mean-field theory in a three dimensional base, leading to a deta iled evaluation of the ultimate limits of physical sizes in nanostruct ured ferroelectrics with the stable polar phase in situations where th e influence of depolarizing field can be neglected. Consequently, the dielectric susceptibility of nanostructured ferroelectrics is also der ived for a three dimensional case. The size dependencies on the phase transition temperatures of perovskite ferroelectris, such as BaTiO3, P bTiO3: and Pb(Zr0.5Ti0.5)O-3, are calculated by considering crystallog raphic anisotropy. In addition we have numerically evaluated the diele ctric coefficient of Pb(Mg, Nb)O-3 near the Curie temperature range ba sed on its microstructure.