Mixed conduction in iodovanadate glass-nanocomposites: DC conductivity, hopping frequency, and frequency response curves

Here, the system of amorphous glassy system, xAgI—(1-x) (0.1CdO—0.3 V2O5—0.4 P2O5—0.2ZnO) with x = 0, 0.05, 0.1, 0.2, 0.3, 0.4 has been developed. The gradual change in the size of various nanocrystallites such as VO2, Zn2V2O7, V6O13, ZnV3O8, and P and the development of new phases of their combinations have been pronounced due to a gradual increase in AgI content. This may lead to possible structural changes of the system under investigation. V–O-V vibration at lower energy may be responsible for weakening the covalent bond, which may be responsible for releasing vanadium ion to contribute more electron/polaron. Correlated barrier hopping (CBH) model has been found to appropriate to predict the hopping conduction paths of charge carriers (or polarons) in pairs via current transfer between localized sites at the Fermi level. By incorporation of more and more AgI content in the composition, more bridging oxygen is expected to be formed in the composition and a strong covalent bonding between Ag+ and O−2 may play dominating role for Ag+ transport over polaron hopping. Double activation energy corresponding to DC conductivity in a wide range of temperature may be considered as the signature of mixed conduction process in the present system. Estimated values of frequency exponent (n) may be highlighted to validate this mixed conduction process. Percolation type of motion of polaron may be predicted from the higher values of n for the as-prepared samples with higher AgI content. Similarly, three-dimensional Ag+ motion may be the dominating charge carriers for the samples with higher AgI content as evidenced from the moderate values of n. A schematic conduction model has been proposed to explain the nature of electrical conductivity in the present system.