Time-dependent dielectric behaviour in incommensurate TlInS2 crystal

The results of measurements of temperature and time dependencies of the dielectric constant of TlInS, in the temperature interval of successive incommensurate and commensurate phase transitions have been presented. Considerable decrease of the dielectric constant in a temperature interval including successive phase transitions was observed after annealing the sample at a fixed temperature in the ferroelectric state. Additionally, it has been revealed that the time dependencies of the real part of dielectric susceptibility and dielectric losses angle tangent of TlInS2 crystal in the incommensurate phase exhibits an unusual behaviour, which is accompanied by exponential decreasing of the dielectric constant and increasing of dielectric losses angle tangent by time. The observed effects are qualitatively explained using defect-density-wave model and phenomenological theory of incommensurate systems containing discommensurations undergoing nucleation and evolution processes. (c) 2009 WILEY-VCH Verlag GmbH & Co. KGaA. Weinheim