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

This paper presents results on statistical investigations of dielectric relaxation data of the mixed crystal [N(CH/sub 3/)/sub 3/H]/sub 3/Sb/sub 2(1-x)/Bi/sub 2x/Cl/sub 9/ (x=0, 0.07, 0.33) (TMACAB) in the frequency range 10/sup 7/ to 10/sup 9/ Hz. The most characteristic 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 phase into another originates. The observed behavior commonly is assumed to reflect the relaxation response of randomly-sized order clusters, considered as precursors of the ferroelectric domains. Using the idea of order clusters we reveal the relaxation mechanism underlying the investigated dielectric response of TMACAB crystals. We also discuss the influence of temperature and stoichiometry on the dielectric response.