Electrical and electronic conductivity of CaO-SiO2-FeOx slags at various oxygen potentials: Part II. Mechanism and a model of electronic conduction

The experimental results obtained for ionic and electronic conductivity of ‘FeO’-CaO-SiO₂ melts have been analyzed considering the mechanism of each conduction process. The Nernst-Einstein equation was employed to calculate diffusion coefficients of Fe²⁺ and Ca²⁺ cations from ionic conductance. A “diffusion-assisted charge transfer” model was developed to explain the dependence of the electronic conductivity on the oxidation state of iron in the slag. The model considers the electronic conduction as a two-step process: in one step, ferrous ions diffuse from their initial position to a proper distance from ferric ions; in the next step, an electron is transferred between Fe²⁺ and Fe³⁺. The optimum distance of the iron ions for electron hopping was found to be approximately 4 Å, in great consistency with the values reported for electron transfer between Fe²⁺ and Fe³⁺ in aqueous solutions and solid glasses.