Electrical conductivity improvement of strontium titanate doped lead vanadate glasses by nanocrystallization

The structural and electrical conductivity (σ) of annealed SrTiO3–PbO2–V2O5 glasses were studied. The annealing of initially glass samples leads to formation of nanocrystalline grains embedded in the glassy matrix. XRD patterns of the glass–ceramic samples show that nanocrystals were embedded in the glassy matrix with an average grain size of 32 nm. The glass–ceramic nanocrystals obtained by annealing at temperatures close to the crystallization temperature Tc exhibit enhancement of electrical conductivity up to four orders of magnitude than initially glasses. The enhancement of the electrical conductivity due to annealing was attributed to two interdependent factors: (i) an increase of concentration of V4+–V5+ pairs; and (ii) formation of defective, well-conducting regions along the glass–crystallites interfaces. From the conductivity temperature relation, it was found that small polaron hopping model was applicable at temperature above θD/2 (θD, the Debye temperature). The electrical conduction at T >θD/2 was due to non-adiabatic small polaron hopping (SPH) of electrons between vanadium ions. The parameters obtained from the fits of the experimental data to this model appear reasonable and are consistent with glass composition.