Ac conductivity and dielectric properties of TlIn 0.975 Y 0.025 S 2 single crystal

The frequency dependence of the electrical conductivity, dielectric properties, and dielectric loss of TlIn 0.975 Y 0.025 S 2 single crystal was studied in the temperature range 303–473 K over the frequency range 10 2 –10 5 Hz. A characteristic frequency, ω p , was found involved in the conduction mechanism, above which the electrical conductivity increased sharply. This observed variation was explained according to Summerfield theory for hopping conductivity which predicted a scaling law for the low‐frequency ac conductivity: σ ( ω ) = σ (0) [1 + ( ω / ω p ) β ]. At higher frequency (≥4 kHz) the ac conductivity increased sharply with frequency according to the power law σ ac ≈ Aω s . The analysis of the ac conductivity at higher frequency showed that the correlated barrier hopping model is the most appropriate mechanism. Also, the loss tangent, tan δ , was predicted to decrease with increasing frequency. Capacitance was found to decrease with increasing frequency and decreasing temperature. The capacitance reached a minimum value, C min , at higher frequencies. Finally the maximum barrier height, W M , the hopping energy, ω H , the relaxation time, τ , and the density of states, N ( E f ), for TlIn 0.975 Y 0.025 S 2 single crystals were determined. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)