Square-wave voltammetry and impedance spectroscopy in iron-doped melts of the system Li2O/Al2O3/SiO2

Glass melts with the basic compositions xLi₂O · 15Al₂O₃ · (85 − x)SiO₂ (x = 8.5, 11, 13.5, 16 and 18.5) doped with 0.25 mol% Fe₂O₃ were studied by square-wave voltammetry and impedance spectroscopy at temperatures in the range from 1100 to 1600 °C. The square-wave voltammograms show a pronounced peak attributed to the reduction of Fe³⁺ to Fe²⁺. The attributed peak potentials which are equal to the standard potentials of the redox pair decrease linearly with the temperature. Impedance spectra measured could be simulated using an equivalent circuit attributed to a simple electron transfer reaction controlled by diffusion.