Boron removal from metallurgical grade silicon by oxidizing refining
(1. National Engineering Laboratory for Vacuum Metallurgy, Faculty of Materials and Metallurgical Engineering, Kunming University of Science and Technology, Kunming 650093, China;
2. Institute of Industrial Science, The University of Tokyo, Bunkyo Tokyo 113-8656, Japan)
2. Institute of Industrial Science, The University of Tokyo, Bunkyo Tokyo 113-8656, Japan)
Abstract: A purification process was developed to remove impurity element boron from the metallurgical grade silicon by the electric arc furnace refining. The thermodynamic equilibria calculation and experiment to remove boron in the oxidizing atmosphere were performed and analyzed. Boron is removed as the gaseous species BxOy and BxHzOy in O2 and H2O-O2 atmosphere respectively. The equilibrium pressure of BxHzOy is 105−1010 times that of BxOy. Boron is removed and its content in silicon is reduced from 18×10−6 to 2×10−6 in the Ar-H2O-O2 atmosphere in the electric arc furnace.
Key words: thermodynamics; metallurgical grade silicon; purification; oxidizing refining; electric arc furnace