Electrical Conductivity of Low-Temperature Potassium Cryolite Electrolytes Suitable for Innovation of Aluminum Preparation

Innovations of aluminum electrolysis process are focused on the inert electrodes and the new types of electrolytes with lower temperature of primary crystallization. The main component in new types of molten systems can be a potassium cryolite. Advantages of these electrolytes are low possible working temperature (above 660 degrees C) and sufficient solubility of an electrochemical active compound (alumina) at these temperatures. The electrical conductivity is one of the most important properties of the electrolytes. Electrochemical impedance spectroscopy was used as a suitable measurement method for determination of the electrical conductivity. Potassium cryolite-based mixtures with the different molar ratios (molar ratio of KF and AlF3 ) and with various additives were studied as a function of the temperature. The molar ratio of binary melt KF-AlF3 varied from 1.2 to 1.5 with the step of 0.1. The temperature dependence (from 655 degrees C to 850 degrees C) and the influence of the addition of Al2O3, CaF2, MgF2 and LiF on the electrical conductivity were obtained. The electrical conductivity was measured by tube-type cell with stationary electrodes; AC-techniques with a sine wave signal in the high frequency range were applied. Temperature and concentration dependencies of conductivity in the studied systems were described by non-linear regression equation. (C) 2018 The Electrochemical Society.