Electrometallurgical Extraction of Silicon Using Solid Oxide Membrane—Molten Salt Electrolysis

Abstract

This paper describes a computational and experimental approach to electrodeposition of silicon using a MgF₂-CaF₂-CaO-Y₂O₃-SiO₂ molten salt electrolyte and a yttria-stabilized zirconia solid oxide membrane at the anode. A secondary and tertiary current density distribution model shows anodic current density between 0.5 and 1 A cm⁻² with a fairly even distribution along the anode surface except at the ends of the anodes. Finite element analysis of industrial cell magnetohydrodynamics (MHD) shows electrolyte flow to be 23 times slower compared to a calculated analytical model. The experiments demonstrate formation of highly pure silicon in the melt with particle sizes ranging from a few μm to clusters of 2 ~ 3 mm. Finally, the mechanism of Si formation based on a short thermodynamic analysis was discussed.