Thermodynamics of the Sn2+/Sn4+ equilibrium in alkali-alkaline earthsilicate melts

Abstract

Melts with the basic compositions I6R2O - 10CaO - 74SiO2 (R = lithium, sodium, potassium), 20Na2O ∙ xCaO ∙ (80-x)SiO2 (x = 0, 10, 20), 16Na2O - 10MgO - 74SiO2 and 15Na2O - 85SiO2 all doped with 0.25 mol% SnO2 were studied using square-wave voltammetry at temperatures in the range from 1000 to 1600 °C. Over a wide temperature range, the measured peak potentials decreased linearly with temperature. The peak potentials are most negative for the 15Na2O - 85SiO2 melt and least negative for the 16Na2O - 10MgO - 74SiO2 melt. The effect of the glass composition on the Sn2+/Sn4+ redox equilibrium is much less pronounced than in the case of the Fe2+/Fe3+ equilibrium.