Abstract
The influence of the static defects and charge carriers on the dielectric permeability temperature anomalies at the phase transitions (PT) from paraelectric phase to incommensurate (IC) phase and from IC phase to ferroelectric one has been determined for Sn2P2S(Se)6 crystals. For these crystals with controlled content of impurities the memory effect recording in IC phase was compared with the dielectric output of the domain walls in ferroelectric phase. The experimental data are analyzed in the mean-field approximation