Effect of annealing on the electrical and optical properties of V₂O₅-GeO₂ glasses

Increases in the electrical conductivities of vanadium germanate glasses on annealing have been reported recently in the literature. The increases were attributed to the formation of microstructure on annealing. In the present work we report a study of the V₂O₅-GeO₂ glass system using electron paramagnetic resonance, optical absorption, differential scanning calorimetry and electron diffraction techniques. The V₂O₅-GeO₂ glass system consists of an equimolar mixture of vanadium pentoxide and germanium dioxide. One sample was unannealed and the other was annealed at 300° C for about 24 h. The results revealed that the increase in the electrical conductivity of the annealed samples could be attributed to the increase of reduced valence states of vanadium ions which accompany the microstructure formation and not solely to the structural change.