Revised approach to dielectric relaxation of TMACAB crystals near the ferroelectric phase transition

This paper presents results on statistical investigations of dielectric rel axation data of the mixed crystal [N(CH3)(3)H](3)Sb2(1-x)Bi2xCl9 (x=0, 0.07 , 0.33) (TMACAB) in the frequency range 10(7) to 10(9) Hz. The most charact eristic property observed at temperatures close to the ferroelectric phase transition is the non-Debye dielectric contribution of ferroelectric active dipoles exhibiting the two power law 'universal' relaxation response. This contribution does not appear in the paraelectric phase and its appearance is observed in the region in which the random process of formation of one p hase into another originates. The observed behavior commonly is assumed to reflect the relaxation response of randomly-sized order clusters, considere d as precursors of the ferroelectric domains. Using the idea of order clust ers we reveal the relaxation mechanism underlying the investigated dielectr ic response of TMACAB crystals. We also discuss the influence of temperatur e and stoichiometry on the dielectric response.