Ionic-to-electronic conductivity of glasses in the P2O5-V2O5-ZnO-Li2O system

Glasses having a composition 15V(2)O(5)-5ZnO-(80-x)P2O5-xLi(2)O (x = 5, 10, 15 mol%) were prepared by the conventional melt quenching. Conduction and relaxation mechanisms in these glasses were studied using impedance spectroscopy in a frequency range from 10 Hz to 10 MHz and in a temperature range from 513 K to 566 K. The structure of the amorphous synthetic product was corroborated by X-ray diffraction (disappearance of nacrite peaks). The DC conductivity follows the Arrhenius law and the activation energy determined by regression analysis varies with the content of Li2O. Frequency-dependent AC conductivity was analyzed by Jonscher's universal power law, which is varying as omega(n), and the temperature-dependent power parameter supported by the Correlated Barrier Hopping (CBH) model. For x = 15mol%, the values of n <= 0.5 confirm the dominance of ionic conductivity. The analysis of the modulus formalism with a distribution of relaxation times was carried out using the Kohlrausch-Williams-Watts (KWW) stretched exponential function. The stretching exponent, beta, is dependent on temperature. The analysis of the temperature variation of the M" peak indicates that the relaxation process is thermally activated. Modulus study reveals the temperature-dependent non-Debye-type relaxation phenomenon.