Structural and electrical properties of TeO2–V2O5–K2O glassy systems

• 50TeO2–(50–x)V2O5–xK2O glasses were prepared by melt-quenching.
• Promising glasses for electrochemical and thermoelectric devices
• The electronic contribution in the samples' conductivity increases with potassium.
• Increasing x promotes the change of V4 + to V5 +.

Ternary glasses with molar composition 50TeO2–(50–x)V2O5–xK2O, where 0 ≤ x ≤ 15, were prepared by the press-melt quenching method. Since this type of glasses shows promising application in electrochemical and thermoelectric devices, the structural and electrical properties of the glassy system presented above were investigated in the present work.In order to evaluate the structure of the prepared glasses, X-ray diffraction (XRD), density measurement, and Raman spectroscopy were performed, while the glass transition temperature and thermal stability were determined by Differential Scanning Calorimeter. The vitreous state of the compositions was confirmed by their XRD pattern. The compositional dependence, particularly the K2O content, on physical features such as density and molar volume, can be correlated with the non-bridging oxygen formation and the variation in linkages. Raman spectra showed a gradual development, from TeO3 to TeO4 structural units, when the mol% of potassium oxide added into the glass network changes from x = 7.5 to x = 15. In addition, for x ≥ 7.5, a decrease of the vanadium coordination from five to four was observed. The effect on the glasses' conductivity, due to the inclusion of K2O, was studied by impedance spectroscopy and dc electrical measurements, in a wide range of temperatures. It was found that the dc conductivity mechanism changed from predominantly ionic, for 2.5 < x ≤ 7.5, to predominantly electronic, for x > 7.5.