Influence of Defects on Dielectric Properties of (CH3\text{}_{3}NH3\text{}_{3})5\text{}_{5}Bi2\text{}_{2}X11\text{}_{11} (x=Cl, Br) Crystals

Influence of defects on ferroelectric properties of the (CH$\text{}_{3}$ΝΗ$\text{}_{3}$)$\text{}_{5}$Bi$\text{}_{2}$Χ$\text{}_{11}$ (Χ = Cl, Br) crystals in the vicinity of ferro-paraelectric phase transition was investigated. γ-irradiation of both crystals insignificantly shifts Tc towards higher temperature. The substitution of chlorine atoms by iodine ones in the (CH$\text{}_{3}$ΝΗ$\text{}_{3}$)$\text{}_{5}$Bi$\text{}_{2}$Cl$\text{}_{11}$ crystal drastically reduces the magnitude of the dielectric permittivity but does not influence on the temperature behaviour of the spontaneous polarization