GB787043A - Method for production of silicon - Google Patents

Abstract

Silicon together with hydrogen iodide is produced by interacting silicon tetraiodide vapour and hydrogen at a temperature of preferably 900-1000 DEG C., more preferably 900-950 DEG C. Hydrogen, purified by passing through finely divided copper at elevated temperature in order to remove oxygen and through calcium chloride to remove moisture, may be passed continuously over molten silicon tetraiodide and the resulting gaseous mixture of hydrogen and silicon tetraiodide passed into a reaction chamber of graphite or quartz surrounded by an induction heating coil. Silicon collects in the chamber and is periodically removed. Hydrogen iodide may be frozen out from the residual gases by passing through a cold trap containing liquid nitrogen. In a cyclic process, iodine may be passed over silicon of 97 per cent purity at a temperature of 750 DEG C., and the resulting silicon tetraiodide passed into a chamber containing pure graphite plates, which may be removed and replaced without stopping the process, for the deposition of the silicon. The hydrogen iodide produced is collected, converted into iodine in known manner and recycled to the process.