Dariush Souri

Semiconducting glasses of the type 40TeO2–(60  x) V2O5–xSb were prepared by rapid melt quenching and their dc electrical conductivity was measured in the temperature range 180–296 K. For these glassy samples, the dc electrical conductivity ranged from 2.26 9 107 S cm1 to 1.11 9 105 S cm1 at 296 K, indicating the conductivity is enhanced by increasing the V2O5 content. These experimental results could be explained on the basis of different mechanisms (based on polaron-hopping theory) in the different temperature regions. At temperatures above HD/2 (where HD is the Debye temperature), the non-adiabatic small polaron hopping (NASPH) model is consistent with the data, whereas at temperatures below HD/2, a T1/4 dependence of the conductivity indicative of the variable range hopping (VRH) mechanism is dominant. For all these glasses crossover from SPH to VRH conduction was observed at a characteristic temperature TR £ HD/2. In this study, the hopping carrier density and carrier mobility were determined at different temperatures. N (EF), the density of states at (or near) the Fermi level, was also determined from the Mott variables; the results were dependent on V2O5 content.