Effect of lead oxide on the electrical transport properties of lithium–iron–borate glasses

The electrical conductivity and dielectric properties of the glass system (70-x) B2O3–(x) Pb3O4–10Fe2O3–20Li2O [where 0 B x B 35] have been investigated in the temperature range from 300 to 530 K, at four fixed frequencies [0.12, 1, 10, and 100 kHz]. Ac conductivity is found to obey the universal relation, r(x)=Axs, where s is the frequency exponent factor and its value is less than unity. Investigation of rac results and the s factor reveals that the polarons hopping over barrier between Fe2? and Fe3? ions is the probable applicable mechanism for rac for these glasses. The dc activation energy values are found to increase from 0.67 to 1.61 eV as the lead oxide content increases. These remarks are explained using Mo ¨ssbauer Effect (ME) spectrometer and molar volume calculations. The observed higher records of the dielectric constant for the lead-free sample could be attributed to some precipitated iron in the form of a-Fe2O3, which increases the polarized space charges in the glass network.