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. Mossbauer results revealed that the relative fraction of Fe2 + was decreased with an increasing Li2O content. The isomer shift values of Fe3 + lie in a range of 0.38–0.45 mm s − 1, while those for Fe2 + 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 V4 + to V5 + in the “vanadate glass” units.