AC conductivity in rare earth ions doped vanadophosphate glasses

Room temperature density and AC conductivity in the temperature range 300-525 K and frequency range 50 Hz to 5 MHz have been investigated in a set of La2O doped vanadophosphate glasses. The density decreased and total conductivity increased with increase of La2O content. The high temperature electrical conductivity has been analyzed using Mott's small polaron model and polaron activation energies were determined. The polaron activation energy decreased marginally with increase of lanthanum content, at all frequencies of interest. These results have been attributed to the presence of mixed ion-polaron conduction in the present glasses. It is for the first time that La2O doped vanadophosphate glasses have been investigated for AC conductivity and despite heaviness of lanthanum ions, the mixed ion-polaron conduction has been detected. Frequency dependence of AC conductivity has been considered under the correlated barrier hopping (CBH) model of single electron hopping.