Combustion synthesis of silicon by magnesiothermic reduction

GRAPHICAL ABSTRACT

ABSTRACT

Magnesiothermic reduction of silica is a powerful method for producing silicon owing to its simplicity, low reduction temperature and low production cost. However, the inevitable formation of magnesium silicide (Mg₂Si) limits the use of this method. A new approach was developed in this research to prevent the formation of Mg₂Si by using alumina as a consumer of gaseous magnesium. Utilizing this approach, highly pure silicon was produced by firstly purifying the silica regent by acid-leaching. It was then subjected to magnesiothermic reduction regimes in order to optimize the power input and molar Mg/SiO₂ ratio to minimize Mg₂Si production. Silicon products were analyzed by X-ray powder diffraction (XRD) and quantitative Rietveld refinement. Optimum electrical power and molar ratio were found to be 3.75 kW and 2.25:1, respectively. The silicon product was examined by glow discharge mass spectrometry which indicated that its purity was 99.96%, with 0.10 ppm of B and 0.15 ppm of P, making it an attractive material for solar cell generation.

KEYWORDS:

• High purity
• silicon
• metallothermic reduction
• acid leaching
• magnesium silicide

Acknowledgements

Dr. Malek Benmansour is fully acknowledged for glow discharge mass spectrometry characterization and deeply thanked for the motivating discussion. Professor Kamel Guerfi and Professor Mostepha Bakouche are also thanked for their support during the stage of silica purification and silicon purification.