PHASE-TRANSITIONS AND ELECTRICAL-CONDUCTIVITY OF TLINS2

The temperature dependence of the electrical conductivity of a TlInS2 single crystal has been investigated under static (delta T/delta t = 0) and dynamic (delta T/delta t not equal 0) conditions. Under the static condition, the electrical conductivity (sigma) of TlInS2 shows a weak anisotropy as the direction of the current in the sample changed from perpendicular to parallel with respect to the crystallographic C-axis. The calculated activation energy of impurity, in both directions of the current, shows a discrepancy, which is attributed to the change of the impurity state under the influence of the internal field. Anomalous behaviour of the electrical conductivity were observed in temperature regions (217-223 K), (200-212 K) and(190-199 K). Under dynamic conditions the temperature dependence of the electrical current I(T) reveals anomalous behaviour at 217, 201, 198 and 192 K. Also anomalies at temperatures 209, 205 and 175 K, corresponding to ferroelectric and structural phase transitions, were detected. A comparison between the present data and some other investigated properties of TlInS2 is also given.