Effects of heat treatment on the structural and electrical conductivity of Fe2O3-P2O5-PbO glasses

Glasses having compositions xFe(2)O(3)-(80 - x)P2O5-20PbO with x = 20, 25, 30, 35 mol% were prepared by traditional glass melt-quenching method. The effects of the heat treatment of glasses on their structural and electrical conductivity were studied by X-ray diffraction (XRD), differential scanning calorimeter, density (rho) and dc conductivity (sigma). The glass transition temperature (T-g) was observed to increase with Fe2O3 content. The density of the prepared glass and corresponding glass-ceramics increases with Fe2O3 content. XRD of as-quenched glass samples confirm the amorphous nature. Triclinic lead iron phosphate PbFe2(P2O7)(2) is the main crystalline ceramic phase formed after heat treatment at 973 K, of 20 and 25 Fe2O3 mol% with average crystallite size of 74 nm. Hexagonal iron phosphate FePO4 phases appeared with Fe2O3 exceeded 30 mol%. The high-temperature conductivity is well explained by polaronic hopping conduction model. It is observed that in this system non-adiabatic hopping conduction is present. The longitudinal optical phonon frequency (nu(omicron)) and density of state N(E-F) of the prepared glass and corresponding glass-ceramics are reasonable for the localized states.