Square-wave voltammetry and impedance spectroscopy in tin doped melts with the compositions xNa2O · 15Al2O3 · (85 − x)SiO2 (x = 8.5, 11 and 16)

Glasses with the base compositions xNa2O · 15Al2O3 · (85 − x)SiO2 (x = 8.5, 11 and 16) doped with 0.5 mol% SnO2 were investigated by both square-wave voltammetry and impedance spectroscopy in the temperature range from 1300 to 1600 °C. Each recorded square-wave voltammogram exhibits a well pronounced peak attributed to the Sn2+/Sn4+-redox pair. Impedance spectra were measured in a frequency range from 0.1 to 105 s−1 as a function of the superimposed dc-potential and were simulated using an equivalent circuit taking into account the resistivity of the melt, the electrochemical double layer, a resistor attributed to a kinetically hindered electron transfer and a Warburg parameter which accounts for the diffusion process of Sn4+ and Sn2+ to and from the electrode. Additionally, two impedance elements, a resistor and a capacitance both attributed to adsorption processes were necessary to fit the impedance spectra.