Effect of nanocrystallization on the electrical conduction of silver lithium phosphate glasses containing iron and vanadium

Abstract

xLi₂O·(20-x)Ag₂O·20Fe₂O₃·60P₂O₅ glasses (x = 0, 5, 10, 15 and 20 mol%) and 5Ag₂O·15Li₂O·5V₂O₅·15Fe₂O₃·60P₂O₅ glass were prepared by melt-quenching of the reagent mixture at 1000 °C. Glass transition temperature (T _g) and crystallization temperature (T _c) of these samples were determined by differential thermal analysis (DTA). It proved that T _g increased with Li₂O content. XRD of as-quenched glasses confirmed their amorphous nature. XRD of samples heat treated for one hour at temperature near their T _c, indicated nanocrystals precipitated in the glassy matrix with an average particle size of 35 nm. Mössbauer results revealed that the relative fraction of Fe^2 + was decreased with an increasing Li₂O content. The isomer shift values of Fe^3 + lie in a range of 0.38–0.45 mm s^− 1, while those for Fe^2 + were 1.10–1.31 mm s^− 1. Heat-treated sample of 5Ag₂O·15Li₂O·5V₂O₅·15Fe₂O₃·60P₂O₅ glass exhibit an enhancement of the electrical conductivity by three orders of magnitude due to the 3d-electron (polaron) hopping from V^4 + to V^5 + in the “vanadate glass” units.