Leaching behaviors of impurities in metallurgical-grade silicon with hafnium addition

This study investigates the leaching behaviors of impurities in metallurgical-grade silicon (MG-Si) with the addition of hafnium (Hf) as an impurity getter. The objective was to enhance the removal of various impurities including boron, iron, aluminum, calcium, phosphorus, zirconium, titanium, vanadium, manganese, hafnium, and nickel from MG-Si. Various leaching approaches were employed to analyze the effects of 5wt% Hf on impurity removal during the solidification of silicon and a silicon-aluminum solvent. Results revealed that Hf significantly improved the leaching efficiency, achieving impressive removal fractions of 94.2% for boron and 86.2% for phosphorus, while reducing the total impurity concentration in silicon from 6126 ppmw to just 94 ppmw. Furthermore, the amount of Hf necessary for effective impurity removal was drastically reduced from 50,000 ppmw to 0.2 ppmw. These findings suggest that Hf is an effective additive for enhancing the purity of metallurgical-grade silicon, providing a promising approach for improving the quality of silicon used in various applications.