A High-Accuracy, Calibration-Free Technique for Measuring the Electrical Conductivity of Molten Oxides

A high-accuracy, calibration-free technique to measure the electrical conductivity of molten oxides has been developed-the coaxial cylinders technique. Because the melt under investigation cokes in contact only with metal and not with anything dielectric, the new technique enables the measurement of the electrical properties of liquids inaccessible by classical high-accuracy techniques. Two coaxial cylindrical electrodes are immersed in the melt to an arbitrary initial depth, and ac impedance is measured over a wide range of frequency. The electrodes are then immersed deeper, and ac impedance is again measured over the same range of frequency. This process is repeated at multiple immersions. The electrical conductivity is calculated from the change in measured conductance with immersion. The temperature dependence of electrical conductivity has been measured for two oxide melts: (M) 50.95 pct CaO, 12.51 pct MgO, 36.54 pct SiO,, 1733 K < T < 1843 K; and (S) 24.59 pct CaO, 26.15 pct MgO, 49.26 pct SiO,, 1763 K < T < 1903 K, where concentration is expressed in mole percent. Both melts exhibited behavior characteristic of ionic liquids.