1977 Volume 63 Issue 6 Pages 917-925
Galvanostatic polarization measurements were made at 1350°C on a solid platinum-molten alkali silicate interface. From the analysis of the initial dccay up to 80μsec of the overpotential-time curves, the exchange current density has been determined as a function of the M2O/SiO2 molar ratio (M=Li, Na and K) and the oxygen partial pressure. (PO2=1, 0.21 and 0.03atm) The exchange current density has been found to increase with increasing the M2O/SiO2 molar ratio and the oxygen partial pressure. Subsequent decay up to 1msec, 10msec, 100msec, 1sec and 5sec- of the overpotential curves has been studied on the assumption that mass-transfer controls the rate of the oxygen discharge reaction. At the constant M2O/SiO2 molar ratio, the slope in the overpotential-square root of time plots has been shown to be inversely proportional to the square root of an oxygen pressure. It was also found that the product of the solubility of and the square root of the diffusivity of soluble oxygen and oxygen ion increases with the increase of the M2O/SiO2 molar ratio. The product also increases with changing M2O from Li2O to Na2O to K2O in this order at a constant M2O/SiO2 molar ratio.