ELECTRONIC CONDUCTION IN VITREOUS SEMICONDUCTORS IN THE PSEUDO-BINARYSYSTEM (AS2S3)(1-X)(PBS)(X)

AC conductivity and dielectric relaxation measurements of the bulk amo rphous compositions in the pseudo-binary system (As2S3)(1-x)(PbS)(x) ( x = 0, 0.1, 0.4 and 0.5) in the frequency range 500 Hz-10 kHz and in t he temperature span 180-450 K are reported. The temperature dependence of the ac conductivity, sigma(ac)(omega), has a broad structure at al l frequencies in compositions with x = 0.1, 0.4 and 0.5 whose peak pos ition is not thermally activated. A similar structure was also observe d in the data on the dielectric constant, epsilon(1), which peaked at a frequency of 1 kHz in the composition with x = 0.5. Analysis of the results using the correlated barrier hopping model revealed that the e lectronic conduction takes place by single polaron and bipolaron hoppi ng processes at high and low temperatures, respectively, in compositio ns containing Pb. The microstructure and phase-separation in the glass es containing Pb influence the electrical transport and dielectric dis persion. This study has revealed the possible presence of a phase tran sformation at around 300 K at a frequency of 1 kHz in the dielectric d ispersion behaviour of composition with x = 0.5.