On the polarization caused by bulk charges and the ionic conductivity in TlInSe$_2$ crystals

TlInSe$_2$ crystals are investigated in dc and ac electric fields in the temperature range of 100–400 K. A decrease in the electrical conductivity $\sigma$ with time in a dc field is revealed. The complex-impedance spectra $Z^*(f)$ are measured in the frequency range of 10–10$^6$ Hz. Diagrams in the $(Z''-Z')$ complex plane are analyzed using the method of equivalent circuits. It is shown that the electrical properties of TlInSe$_2$ crystals in the investigated ranges of temperatures and frequencies are determined by hopping conductivity and the accumulation of charge carriers near blocking platinum electrodes.