Electrolytic deposition of silicon and of silicon alloys Part III: Deposition of silicon and aluminum using a copper cathode

AbstractThe decomposition voltages of SiO2 and Al2O3 dissolved in cryolite were measured using a copper cathode. In a melt containing 90 wt% Na3AlF6 + 10 wt% Al2O3 at 1030°C the decomposition voltage of alumina was found to be Ed = 1.50 ± 0.05 V. In a melt containing 95 wt% Na3AlF6 + 5 wt% siO2 the value of the decomposition voltage was determined to Ed = 1.10 ± 0.05 V. In Na3AlF6-Al203-SiO2 mixtures the decomposition voltage of silica was found to increase with increasing concentration of alumina in the electrolyte.It was determined that at current densities below 0.2 A·cm−2 only silicon was deposited at the cathode whereas at higher current densities Si and Al were deposited simultaneously. The deposition ratio was found to depend on the current density.The distribution of silicon in the Si-Cu alloy was determined by spectroscopic analysis. It was found to be a function of the current density and of the diffusion rate of the deposited metal in the alloy. Resume Les auteurs mesurent sur cathode de cuivre...