Mixed conductivity of glasses in the P2O5-V2O5-Na2O system

The conductivity of glasses in the P2O5−[(1−x) V2O5−x Na2O] system is studied as a function of temperature and composition. For all compositions, the conductivity variations as a function of temperature follow an Arrhenius type relationship:\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document} $$\sigma = \frac{A}{T}\exp \left( { - \frac{{E_a }}{{RT}}} \right)$$ \end{document}. The activation energies and pre-exponential factors corresponding to the V2O5 richest compositions are lower than that corresponding to the ionic ones. Isothermal variations of the conductivity as a function of composition show a deep minimum for a molar ratio x near 0.65. On either side of this minimum, the conductivity is mainly electronic (x<0.7) or ionic (x>0.8). The variations are interpreted assuming a prevailing diluting effect of the non predominantly present oxide without any interactions between the electronic and ionic charge carriers.