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

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 (Tg) and crystallization temperature (Tc) of these samples were determined by differential thermal analysis (DTA). It proved that Tg 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 Tc, indicated nanocrystals precipitated in the glassy matrix with an average particle size of 35 nm. Mössbauer 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.