The purification of metallurgical grade

Metallurgical grade silicon (MG-Si) is obtained from the reduction of silica (SiO2) in a voltaic arc furnace. The impurities are inherent to the reduction process and they are also dependent on the quality of the initial materials. Among other applications, silicon is used as a substrate for photovoltaic conversion of energy and this conversion improves with greater purity of the substrate. This research utilized the technique of silicon purification in an electron beam furnace, where melting occurs in a high vacuum and impurities are extracted by evaporation. Two types of MG-Si were used as starting materials: bulk MG-Si without leaching, with an initial purity of 99.88%, and leached MG-Si with an initial purity of 99.92%. The final purity of both materials exceeded 99.999%. These findings demonstrate that the electron beam melting process is technically viable and effectively reduces the need for chemical purification stages employed in other techniques. This study contributes to the ongoing exploration of new purification processes for silicon, significant for enhancing substrate quality in solar energy applications.