Increasing the conductivity of V2O5-TeO2 glass by crystallization: structure and charge transfer studies

In the present paper, V2O5-TeO2 glass was prepared by the melt-quenching technique. Crystallization of glass with a vanadium content higher than 35%mol results in an increase in electrical conductivity by a few orders of magnitude and a decrease in activation energy from similar to 0.40 to similar to 0.12 eV. In this work, a critical review of existing charge transfer models was presented on the example of V2O5-TeO2 glass and glass-ceramics. Schnakenberg's and Friedman-Triberis' charge transfer models were found to be applicable to both glass and glass-ceramics. Optical phonon frequencies obtained from Schnakenberg's model are in agreement with FTIR studies. Values of activation energies obtained from the Schnakenberg model decrease after crystallization. Friedman-Triberis' model shows an increase in the density of states near the Fermi level from 10(19) eV(-1) cm(-3) in glass, to 10(21) eV(-1) cm(-3) in glass ceramics. Structural studies show that the main crystallizing phase is Te2V2O9 which occurs with the V2O5 shell in glasses with compositions 50-50%mol and 45-55%mol. It is concluded that crystallization results in the reduction of vanadium ions in the remaining glass matrix which leads to an increase in the V4+/V5+ ratio and therefore, an increase in electrical conductivity.

Automated summary

In this study, V2O5-TeO2 glass was prepared and its crystallization led to a significant increase in electrical conductivity and a decrease in activation energy. Existing charge transfer models, including Schnakenberg's and Friedman-Triberis', were found applicable to both glass and glass-ceramics. Structural studies revealed the main crystallizing phase to be Te2V2O9, which resulted in the reduction of vanadium ions and an increase in electrical conductivity.