Synthesis and characterization of (68-x) CuO? xV2O5? 32TeO2 (x=0?68 mol%) and (35-x) CuO? xV2O5? 65TeO2 (x=0?35 mol%) glasses: Conduction mechanism, structure and EPR study

In this work, two series of glasses, i.e. (68-x) CuO ? xV2O5 ? 32TeO2 (x = 0?68 mol%, Te32 series) and (35-x) CuO ? xV2O5 ? 65TeO2 (x = 0?35 mol%, Te65 series), were synthesized by the melt-quenching method and subjected to physical, thermal and electrical characterization. Their vitreous nature was confirmed by X-Ray diffraction and differential scanning calorimetry, while their structural units were determined by Raman spectroscopy. CuO substitution by V2O5 led to a decrease in density and glass-transition temperature, together with a conductivity increase. Conduction mechanism was interpreted as mainly due to small polaron hopping from the lower (V4+) to the higher (V5+) vanadium valence states. Te32 glasses, possessing the highest electronic conductivities (ranging from 2 E-4 to 5 E-7 ?- 1 cm-1), were investigated by the Electron Paramagnetic Resonance technique, in order to more deeply analyze their structureconductivity correlation. Particularly, the observed signals were determined to consist in a superposition of a first line due to paramagnetic Cu2+ ions and a second line due to exchange-coupled CuO clusters. Differences in the spectra were determined between samples with higher (i.e. 20-30 mol%) Cu2+ concentrations and samples with lower Cu2+ concentrations, suggesting they are located in different local environments. Finally, it was found that the Cu2+ ions are not involved in the process of electron transfer.

Automated summary

In this study, two series of glasses were synthesized and characterized, showing that substitution of CuO by V2O5 led to a decrease in density and glass-transition temperature, as well as an increase in conductivity. The Te32 series of glasses exhibited the highest electronic conductivities and the structure-conductivity correlation was further analyzed using Electron Paramagnetic Resonance technique.