Characterization and Conduction Mechanism of Highly Conductive Vanadate Glass

This paper reviews recent studies of highly conductive barium iron vanadate glass with a composition of 20 BaO ∙ 10 Fe₂O₃ ∙ 70 V₂O₅ (in mol %). Isothermal annealing of the vanadate glass for several ten minutes at a given temperature, higher than glass transition temperature or crystallization temperature, caused an increase in σ. Substitution of CuI (3d10), ZnII (3d10) and CuII (3d9) for FeIII (3d5) was investigated to elucidate the effect of electron configuration on the conductivity (σ). A marked decrease in the activation energy of conduction (Ea) was also observed after the annealing. Values of Ea were correlated to the energy gap between the donor level and the conduction band (CB) in the n-type semiconductor model. Isothermal annealing of ZnII-substituted vanadate glass (20 BaO ∙ 5 ZnO ∙ 5 Fe₂O₃ ∙ 70 V₂O₅) at 450 °C for 30 min showed an increase in σ from 2.5 × 10^–6 to 2.1 × 10^–1 S cm^–1, which was one order of magnitude larger than that of non-substituted vanadate glass (3.4 × 10^–2 S cm^–1). Under the same annealing condition, σ’s of 2.0 × 10^–1 and 3.2 × 10^–1 S cm^–1 were observed for 20 BaO ∙ 5 Cu₂O ∙ 5 Fe₂O₃ ∙ 70 V₂O₅ and 20 BaO ∙ 5 CuO ∙ 5 Fe₂O₃ ∙ 70 V₂O₅ glasses, respectively. These results demonstrate an increase in the carrier (electron) density in the CB, primarily composed of anti-bonding 4s-orbitals.

Abstract licence: CC BY

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