The dielectric parameters and electric conductivity of (NH2(CH3)2)2CoCl4 crystals are investigated. Existence of the ferroelectric phase was observed below Tc = 258 K. The occurrence of phase transitions at 244, 314, and 435 K is confirmed. The investigated crystals also manifest anomalously high conductivity commensurate with that in semiconductors. Its value as well as region of existence strongly depend on the preceding history of the sample. It is shown that the anomalous conductivity is connected with translocation of protons which participate in the formation of hydrogen bonds.

Dielectric dispersion in ferroelectric hydrogen bonded glicyne phosphite crystal was investigated in the frequency range 100 Hz -27 GHz. Dielectric relaxation of Debye type observed in the paraelectric phase shows a critical slowing down of the polarization fluctuations. The relaxation frequency decreases with temperature according to fs = 0.305(Τ -Τ0) GHz in the paraelectric phase. The activation energy for flipping dipole motion ΔU = 2.07kΤc confirms order-disorder character of the phase transition. In the ferroelectric phase pronounced low frequency (100 Hz -1 MHz) dispersion related to domain contribution to permittivity was found.

On the basis of dilatometric, optical, and dielectric investigations of (NH3C2H5)2CuC14 crystals the existence of phase transitions at T1 = 364 and T2 = 356 K was confirmed. Anomalous behaviour of the thermal expansion coefficient and optical birefringence around T3 = 330 K was related to earlier unknown phase transition. Besides, it was shown that these crystals are characterised by considerable protonic conductivity, the nature of which is fairly well explained in the framework of Grotthus mechanism of proton transport.

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Optical and spectral investigations confirmed the availability of phase transitions in [C 2 H 5 NH 3 ] 2 CuCl 4 at T 1 = 364 K, T h 2 = 356 K, T 3 = 232 K. It has been found that the empirical Urbach rule is fulfilled in all phases. It is shown, that in the high-temperature phases skeletal vibrations of the C±N±C group interact with phonons, whereas in the low-temperature phases internal vibrations of the metal±halogen complex occur. A ferroelastic domain structure was observed using the polarising microscope in the temperature region 232 to 364 K.