Correlation between nanostructural and electrical properties of barium titanate-based glass-ceramic nano-composites

Glasses in the system BaTiO3-V2O5-Bi2O3 have been transformed into glass-ceramic nano-composites by annealing at crystallization temperature T-cr determined from DSC thermograms. After annealing they consist of small crystallites embedded in glassy matrix. The crystallization temperature T-cr increases with increasing BaTiO3 content. XRD and TEM of the glass-ceramic nano-composites show that nanocrystals were embedded in the glassy matrix with an average grain size of 25 nm. The resulting materials exhibit much higher electrical conductivity than the initial glasses. It was postulated that the major role in the conductivity enhancement of these nanomaterials is played by the developed interfacial regions between crystalline and amorphous phases, in which the concentration of V4+-V5+ pairs responsible for electron hopping, has higher than values that inside the glassy matrix. The experimental results were discussed in terms of a model proposed in this work and based on a "core-shell" concept. From the best fits, reasonable values of various small polaron hopping (SPH) parameters were obtained. The conduction was attributed to non-adiabatic hopping of small polaron. (C) 2011 Elsevier B. V. All rights reserved.