Studies of silver-vanadate-phosphate glasses by Raman, EPR and impedance spectroscopy methods

Four different series of AgI-Ag2O-V2O5-P2O5 glasses have been prepared, in a wide range of compositions defined by the ratio of r = [Ag2O]/[V2O5 + P2O5] and a parameter x (mol.% of AgI). DTA and Raman scattering experiments reveal that the glass-networks of the investigated glasses are determined mainly by r values, and the x (up to 40%) parameter plays a secondary role. EPR spectra show that the interactions between vanadium centers (which are essential for electronic hopping) strongly depend on crosslinking of the glass network. They dramatically weaken if the glass-network is broken by addition of a large amount of a glass-modifier (Ag2O). Depending on values of r and x the character of electric conduction of the studied glasses changes from purely electronic through mixed to predominantly ionic (via Ag+ cations). (C) 2000 Elsevier Science B.V. All rights reserved.