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The Fe2+/Fe3+-redox equilibrium in 5Na2O·15CaO·xAl2O3· liquids

2001; Elsevier BV; Volume: 290; Issue: 1 Linguagem: Inglês

10.1016/s0022-3093(01)00715-3

1873-4812

Achim Wiedenroth, Christian Rüssel,

Ferroelectric and Piezoelectric Materials

Liquids with the basic compositions of 5Na2O·15CaO·xAl2O3·(80−x)SiO2 (x=5,10,15,20,25) doped with 0.25 mol% Fe2O3 were studied by means of square-wave voltammetry in the temperature range 1200–1600°C. With increasing temperature, redox equilibria were shifted to the reduced state. Increasing the alumina concentration from 5 to 10 mol% resulted in an increase in the standard potentials, i.e., in a shift to the reduced state. If the alumina concentration is further increased, the standard potentials decrease again. The latter is caused by the incorporation of alumina in sixfold coordination.