Effect of Electrolysis Potential and Molar Ratio of CaO to SiO₂ on Si Metal Deposition in Molten CaCl₂

Abstract

The electrodeposition of Si metal in molten CaCl₂ containing various types of calcium silicate has been studied at 1373∼1673 K. It was shown that the influence of the molar ratio of CaO to SiO₂ on Si electrodeposition was not remarkable in contrast with our previous results that the molar ratio of CaO to TiO₂ strongly affected the Ti metal deposition in the similar system. Silicon metal was obtained on MoSi₂ cathode in the melt by potentio-static electrolysis. The cathodic current efficiency was about 30% regardless of the added types of calcium silicate. The current efficiency tended to be better as the electrolysis potential became negative, but the electrolysis below the border potential lead to lower current efficiency due to Ca co-deposition.

Enough metallic Si to evaluate the current efficiency from its weight was obtained by potentio-static electrolysis in molten CaCl₂ with Ca₂SiO₄ at 1673 K. It was shown that the current efficiency of Si metal deposition depended on electrolysis potential, though the further study to clarify the optimum condition for better electrolysis is necessary.