Electronic and ionic transport in liquid PbO-SiO₂ systems

The objective of the present work was to examine electronic transport in the PbO-SiO₂ melt. The experimental work consisted of studying the oxidation of liquid Pb covered by a layer of liquid PbO-SiO₂ using a thermogravimetric arrangement. Oxidation of liquid Pb was dependent on the melt height and was parabolic in nature, indicating the oxidation process to be diffusion controlled. We observed a moderate increase in the oxidation rate with additions of a transition metal oxide (Fe₂O₃) to the melt. However, when melt/gas and melt/metal interfaces were short circuited by Ir wires, a much higher increase in the oxidation rate was noticed. Additionally, the conductivity of the PbO-SiO₂ melt with Fe₂O₃ additions was measured as a function of P_o, to detect the nature of electronic contribution by the Fe₂O₃. Combining the results of the oxidation and conductivity experiments, we conclude that the oxidation of liquid lead covered by liquid slag occurs through ionic and rate controlling electronic (probably electron holes) transport in the melt.