Electronic-Ionic Conductivity in Molybdenum Oxide glasses Doped with Sodium ions

Abstract

The conductivity of three glasses samples in 30Na₂O-(70-x)MoO₃-xP₂O₅ systems and two glass samples in 60%Na₂O-40%P₂O₅ and 60% MoO₃-40%P₂O₅ systems was investigated as a function of  temperature. It is also found that conductivity for glasses containing higher percentage of sodium ions is predominantly ionic and in glasses containing higher percentage of molybdenum ions is predominantly electronic. For pure sodium phosphate glass or the glass containing lower concentration of molybdenum the plot of logσ_dc vs. 1000/T is almost linear, whereas for glasses containing increasing concentration of molybdenum ions the plots depart from linearity. These non-linear plots indicate a change in activation energy which suggests a contribution from electronic conduction. Ionic glasses exhibit only one conduction process and single activation energy in the whole temperature range. In transition metal oxide glasses with mobile cations, different conduction processes contribute to electronic conduction at different temperature ranges leading to different values of activation energy. Choosing proper doping levels allows one to tailor mixed conducting oxides.