Dilatomelric and Pyroelectric Study of Phase Transition in (CH3\text{}_{3})2\text{}_{2}NH2\text{}_{2}Al(SO4\text{}_{4})2\text{}_{2} · 6H2\text{}_{2}O Ferroelectric Crystal

The results of linear thermal expansion and pyroelectric coefficient are given for crystal of dimethylammoniumaluminium sulphate hexahydrate. Large anomalies of these quantities has been observed around the phase transition temperature at 151 K

Dilatometric Study of the Phase Transition in (CH3\text{}_{3}NH3\text{}_{3})5\text{}_{5}Bi2\text{}_{2}Cl11\text{}_{11}

The paper reports a dilatometric study on (CH$\text{}_{3}$NH$\text{}_{3}$)$\text{}_{5}$Bi$\text{}_{2}$Cl$\text{}_{11}$ single crystals. It is shown that elongation of the crystal is continuous but linear thermal expansion coefficients are discontinuous at phase transition temperature

Dielectric Properties of the (CH3\text{}_{3}NH3\text{}_{3})5\text{}_{5}Bi2(1−x)\text{}_{2(1- x)}Sb2x\text{}_{2x}Cl11\text{}_{11} Mixed Crystals

The (CH$\text{}_{3}$NH$\text{}_{3}$)$\text{}_{5}$Bi$\text{}_{2(1-x)}$Sb$\text{}_{2x}$Cl$\text{}_{11}$ crystals were examined from the point of view of their applicability in pyroelectric detectors. It was shown that they can be useful so far as the construction of infrared detectors is concerned due to high values of both their pyroelectric coefficient and figure of merit p/sqrtε which are both comparable with those of triglycine sulphate crystals

The Internal Bias Field of Ferroelectric (CH3\text{}_{3}NH3\text{}_{3})5\text{}_{5}Bi2\text{}_{2}Br11\text{}_{11}

Spontaneous polarization of (CH$\text{}_{3}$NH$\text{}_{3}$)$\text{}_{5}$Bi$\text{}_{2}$Br$\text{}_{11}$ crystals has been measured and the ferroelectric hysteresis loop has been studied. The observed time changes in the polarization have been ascribed to the change in the internal bias field of the crystal. Measurement results have also been discussed for the lower phase transition (T$\text{}_{II}$ = 77 K)

Dielectric Properties of the (CH 3

The (CH$\text{}_{3}$NH$\text{}_{3}$)$\text{}_{5}$Bi$\text{}_{2(1-x)}$Sb$\text{}_{2x}$Cl$\text{}_{11}$ crystals were examined from the point of view of their applicability in pyroelectric detectors. It was shown that they can be useful so far as the construction of infrared detectors is concerned due to high values of both their pyroelectric coefficient and figure of merit p/sqrtε which are both comparable with those of triglycine sulphate crystals

Phase Transitions in (CH3\text{}_{3}NH3\text{}_{3})5\text{}_{5}Bi2\text{}_{2}X11\text{}_{11} (X=Cl, Br) Crystals

Electric properties of (CH$\text{}_{3}$NH$\text{}_{3}$)$\text{}_{5}$Bi$\text{}_{2}$Cl$\text{}_{11}$ and (CH$\text{}_{3}$NH$\text{}_{3}$)$\text{}_{5}$Bi$\text{}_{2}$Br$\text{}_{11}$ single crystals in the direction of the crystallographic b-axis were studied. The samples tested were natural crystal seeds in the form of thin plates, whose crystallographic b-axis coincides with the normal to the plate. Measurements of the pyroelectric coefficient were performed near the high temperature phase transition and spontaneous polarization from the paraelectric phase down to helium temperature. The attempt of explanation of the anomalous electric properties of these crystals has been presented

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