Dielectric Relaxation in Ferroelectric MASD, CH_3NH_3Al(SO_4)_2・12H_2O

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The complex dielectric constant of methylammonium aluminum sulfate dodecahydrate, CH_3NH_3Al(SO_4)_2・12H_2O, was measured at various frequencies in a frequency range between 1×10^6 and 1×10^9Hz in its para- and ferroelectric temperature regions. The experimental result was analyzed for the paraelectric phase. The crystal exhibits critical slowing-down process of polarization. The observed temperature and frequency dependences of the complex dielectric constant can be described to good approximation in terms of a single relaxation time τ(T) of Debye type. Above the Curie point (T_c), the static dielectric constant follows the Curie-Weiss law ((ε_0-ε_∞)∼(T-T_0)^<-1>:), while τ(T) is described well by the relation τ(T)=α・(T-T_0)^<-1>・exp(ΔU/k_BT) with the potential barrier height ΔU=(2.18±0.06) kcal・mol^<-1> and α=(0.92±0.14)(h/k_P).
社団法人日本物理学会の論文
1971-09-05