Influence of Defects on Dielectric Properties of (CH₃NH₃)₅Bi₂X₁₁(x=Cl, Br) Crystals

Abstract

Influence of defects on ferroelectric properties of the (CH3ΝΗ3)5Bi2Χ11 (Χ = Cl, Br) crystals in the vicinity of ferro-paraelectric phase transition was investigated. γ-irradiation of both crystals insignificantly shifts T c towards higher temperature. The substitution of chlorine atoms by iodine ones in the (CH3ΝΗ3)5Bi2Cl11 crystal drastically reduces the magnitude of the dielectric permittivity but does not influence on the temperature behaviour of the spontaneous polarization.

Crystal structure, phase transition and ferroelectric properties of the [(CH3)3NH]3[Sb2Cl9(1 x)Br9x] (TMACBA) mixed crystals

“…The substitution for the antimony atoms of the bismuth ones in TMACA remarkably affected the parameters of the paraelectric-ferroelectric phase transition. The increase of the Bi concentration in the mixed [(CH 3 ) 3 NH] 3 [Sb 2(1−x) Bi 2x Cl 9 ] (TMACAB) crystals shifted the phase transition towards lower temperatures and simultaneously decreased the maximum value of 0 at T C [20][21][22][23]. X-ray diffraction and dielectric studies on the mixed TMACAB crystals clearly showed that the existence of ferroelectric properties in the halogenoantimonates (III) of the R 3 M 2 X 9 composition was strictly related to the presence of polyanionic layer structure.…”