Phase transitions in Sr _0.61 Ba _0.39 Nb ₂ O ₆ :Ce ³⁺: I. Susceptibility of clusters and domains

Abstract:

The complex dielectric susceptibility of Sr _0.61 Ba _0.39 Nb ₂ O ₆ :Ce ³⁺ (SBN61:Ce) has been measured at frequencies and temperatures before and after poling. The relaxor behaviour with large polydispersivity observed above the ferroelectric phase transition temperature, T _c = 360 and 340 K for x (Ce) = 0 and 0.0066, respectively, is perfectly modeled within the framework of Chamberlin's dynamically correlated domain approach. Below T _c the dynamic nanodomain state crosses over into a ferroelectric state with polydispersive domain wall dynamics at very low frequencies. Presumably SBN61:Ce belongs to the three-dimensional random field Ising rather than to the dipole glass universality class.