Effect of TeO2 Addition on the Mobility of Silver Ions in Ag2O-B2O3-P2O5-TeO2 Glasses

Abstract

The effect of adding TeO2 into (100-x)[0.5Ag2O−0.1B2O3−0.4P2O5]−xTeO2 glasses, with 0−80 mol% TeO2, on the structural changes and electrical properties has been investigated. The structure was studied by Raman spectroscopy and electrical properties have been studied over a wide temperature and frequency range by impedance spectroscopy. The addition of the third glass former, TeO2, to the glass network causes the structural transformation from TeO3 (tp) to TeO4 (tbp) which contributes to the changes in conductivity. The glasses with low TeO2 content show only a slow decrease in dc conductivity with addition of TeO2 due to the increase of the number of non-bridging oxygens, which increases the mobility of Ag+ ions. The steep decrease in conductivity for glasses containing more than 40 mol% TeO2 is a result of decrease of the Ag2O content and stronger cross-linkage in glass network through the formation of more Te-eqOax-Te bonds in TeO4 tbp units. The glasses obey scaling of the ac conductivity with respect to temperature indicating that the dynamic process is independent of temperature. However, the scaling of the spectra for different glasses revealed deviations from the Summerfield scaling due to the local structural disorder caused by structural transition in tellurite glass network.