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The results of the study of the temperature dependence of the dielectric permittivity of Cd2P2S6 crystals are presented. It is shown that in the temperature range 80–420 K there are three regions in which hysteresis phenomena are observed. At high temperatures (T > 320 K) there is an activation change of the dielectric losses associated with the increased conductivity of Cd2P2S6 crystals. The transition from heating to cooling leads to a decrease in losses, which is manifested as a hysteresis in the dielectric constant. A jump-like change in dielectric permittivity is found at 228 K in the cooling mode and 265 K in the heating mode, which is due to the first-order phase transition in these crystals. The third hysteresis region appears at low temperatures of 80–90 K. When the temperature is cycled in this interval, the classical hysteresis behavior is observed with a decrease in both amplitude and temperature range with each cycle. The cause of this behavior will be the subject of further investigation. [ABSTRACT FROM AUTHOR]

Layered Cu(CrxIn1 - x)P2S6 mixed crystals have been studied by measuring the complex dielectric permittivity along polar axis in the frequency range 100 Hz - 16 MHz. It has been found that for 0.8 ≤ x ≤ 1.0 the line of the phase transitions into the antiferroelectric phase on the phase diagram occurs. On other side of the phase diagram at 0.2 ≤ x ≤ 0.3 the long range ferroelectric order coexisting with relaxation glassy-like behavior is observed. In the intermediate concentration range for 0.4 ≤ x ≤ 0.6 the state can be identified dipole glassy-like state. The dipole glass also coexists with the ferroelectric state in CuInP2(SexS1 - x)6 mixed crystals when x → 0. With an increase in selenium content the dipole glass transforms into a ferroelectric state via relaxor ordering regime. [ABSTRACT FROM AUTHOR]