Electrical and Optical Properties of Phosphate Glasses Containing Multiple Transition Ions

Electrical and optical properties of phosphate glasses containing multiple transition Ions have been studied In xP 2 O 5 - (100-x) (Fe 2 O 3 +MnO) (PFM) and xP 2 O 5 - [(100-x) (V 2 O 5 + MnO)] (PVM) glasses. DC conductivity results indicate that Mn Ions do not contribute to the conduction process. Small polarons, contributed by the reduced Fe and V Ions, have been identified to be the charge carriers in both glass systems. Although the activation energy for dc conduction, W, remains unchanged for all Fe concentrations in the PFM series, the resistivity shows an exponential increase when the concentration of Fe ions exceeds a critical value. In the PVM glasses, a decrease in the concentration of V Is accompanied with an Increase in W. However, as in the PFM system, an exponential Increase In resistivity was observed at a critical concentration of V Ions. The resistivity transition In these glasses has been tentatively explained by a (small) polaron to (small) bipolaron transition (PBT) which is supported by optical absorption data.