Voltammetric studies on redox equilibria of various polyvalent elements in CaO/BaO/Al2O3/SiO2-melts

The thermodynamics of redox equilibria of various polyvalent elements were studied by square-wave voltammetry in glass melts with the basic molar compositions of 10CaO·10BaO·15Al2O3·65SiO2 and 10CaO·10BaO·10Al2O3·70SiO2 doped with 0.5 mol% Na2O and oxides of As, Sb, Sn, Ti, V, Cr, Fe and Cu. Besides Fe and Ti, all elements may occur in these melts in three different oxidation states. Standard potentials measured increased linearly with temperature, the redox equilibria were shifted to the reduced state. Most standard potentials were more negative in the melt with 15 mol% Al2O3. The electrochemical series of elements were almost the same as those previously observed in silicate melts possessing alkali contents in the range 15–33 mol%.