A method for the preparation of highly pure boron, silicon or germanium and / or mixtures of these substances

摘要

PICT:0926362/III/1 B or Si or mixtures or alloys of these are produced by passing the corresponding halide, hydride or hydrogen-containing halide or mixture thereof in the gaseous or vaporous form through a fluidized bed of the element to be produced or an inert material heated to above the decomposition temperature. Inert or reducing gases or vapours may be passed in with the gaseous starting materials. The Figure shows an apparatus in which an upflowing stream of gases or vapours from 2, preheated at 3, fluidizes a particulate bed contained between a and b. The issuing gases pass out through filters 5 and 6 and a condenser 7, and a part or all of them may be recycled through a pump 12. The element produced deposits on the particles of the fluidized bed until these fall and are discharged at 9. Simultaneously fresh particles are formed in the bed and further material deposits on these. By increasing the velocity of the upflowing gases these fresh particles may be removed and collected at the filter 5. Mixtures of elements may be produced by passing mixed gases into the bed and the particles produced may be alloyed if the bed temperature is correct. The process may also be used for producing fine Si particles from by passing Si Cl4 or Si Br4 through a bed of coarse Si particles at above the decomposition temperature. The fluidized bed may be heated by electric induction or resistance heating or by periodically supplying a gas (e.g. H2 or HCl) which reacts exothermically with the bed material.