Voltammetric studies in iron-doped 5Na2O·xMgO·(15−x)CaO·yAl2O3·(80−y)SiO2 melts

Melts with the basic compositions 5Na2O·xMgO · (15−x)CaO·yAl2O3 · (80−y)SiO2 doped with 0.25–0.5 mol% Fe2O3 were studied using square-wave voltammetry at temperatures in the range of 1300–1600 °C. Decreasing the temperature resulted in more negative standard potentials. Introducing alumina in the soda–alkaline earth-silicate melts also resulted in less negative standard potentials, i.e. in a shift of the redox equilibrium to the reduced state. A further increase in the alumina concentration led to a re-decrease of the standard potentials. The alumina concentration attributed to maximum standard potentials is an effect of the CaO concentration. A structural model is proposed.