Influence of chromium ions on dielectric and spectroscopic properties of Na2O-PbO-B2O3 glass system

Na2O-PbO-B2O3 glasses doped with Cr2O3 by varying its concentration relative to borate (in the range of 0 to 0.2 mol% in steps of 0.05 mol %) are prepared. Dielectric studies (dielectric constant ε', loss tan δ, conductivity σac etc in the frequency range 103 to 106 Hz and in the temperature range 30 to 250 deg. C) and spectroscopic properties like IR and ESR etc. were carried out on these samples. From these studies it was noticed that chromium with Cr6+ ions exist in network forming positions at low concentration i.e., at 0.05 mol% beyond which Cr6+ ions gradually get converted into Cr3+ ions, there by act as network modifiers and decrease the rigidity of the glass network.