57Fe-Mössbauer study of electrically conductive alkaline iron vanadate glasses

Highly conductive barium iron vanadate glass containing different metal oxides

20BaO·5ZnO·5Fe2O3·70V2O5 glass annealed at 450°C for 30 min showed a marked decrease in the electric resistivity (ρ) from 4.0×105 to 4.8 Ωcm, while 20BaO·5Cu2O·5Fe2O3·70V2O5 glass from 2.0×105 to 5.0 Ωcm. As for the conduction mechanism, it proved that n-type semiconductor model in conjugation with the small polaron hopping theory was most probable. Since ZnII and CuI have a 3d10-electron configuration in the outer-most orbital, Ga2O3- and GeO2-containing vanadate glasses were explored in this study. 20BaO·5Ga2O3·5Fe2O3·70V2O5 glass showed a less remarkable decrease of ρ from 4.5×105 to 100 Ωcm, and 20BaO·5GeO2·5Fe2O3·70V2O5 glass from 3.3×106 to 400 Ωcm. Activation energies for the conduction (Ea) of GeO2- and Ga2O3-contaning glasses before the annealing were respectively estimated to be 0.42 and 0.41 eV. It proved that barium iron vanadate glass with a smaller Ea value could attain the higher conductivity after the annealing at temperaures higher than the crystalization temperature.