Abstract: A method for producing high-purity silicon nitride in two steps is described, wherein a) high-purity silicon is reacted with nitrogen in a rotary tubular furnace comprising a first temperature zone of 1,150 to 1,250° C. and at least one other temperature zone of 1,250 to 1,350° C. in the presence of a gas mixture comprising argon and hydrogen, said reaction proceeding up to a nitrogen content of 10 to 30 wt % and b) allowing the partially nitrogen-containing product from step a) to react in a chamber or settling furnace in a quiescent bed at 1,100 to 1,450° C. with a mixture of nitrogen, argon and optionally hydrogen up to the completion of nitrogen uptake. It is possible, utilizing the method according to the invention, to produce high-purity silicon nitride with a purity of >99.9 in a technically simple manner, wherein no further purification steps, such as leaching with inorganic acids, are required.

Abstract: A method for producing high-purity silicon nitride in two steps is described, wherein a) high-purity silicon is reacted with nitrogen in a rotary tubular furnace comprising a first temperature zone of 1,150 to 1,250° C. and at least one other temperature zone of 1,250 to 1,350° C. in the presence of a gas mixture comprising argon and hydrogen, said reaction proceeding up to a nitrogen content of 10 to 30 wt % and b) allowing the partially nitrogen-containing product from step a) to react in a chamber or settling furnace in a quiescent bed at 1,100 to 1,450° C. with a mixture of nitrogen, argon and optionally hydrogen up to the completion of nitrogen uptake. It is possible, utilizing the method according to the invention, to produce high-purity silicon nitride with a purity of >99.9 in a technically simple manner, wherein no further purification steps, such as leaching with inorganic acids, are required.

Abstract: The present invention provides a process for the production of silicon nitride by the reaction of silicon and nitrogen, wherein, in one reaction step, silicon powder is reacted with nitrogen which continuously rotates at a temperature of from 1000.degree. to 1800.degree. C. and at a pressure of from 1.01 to 1.8 bar up to a nitrogen content of 1 to 39.5% by weight.The present invention also provides a silicon nitride produced by this process wherein it is obtained in porous form and has the following properties.a) grain size of 0.1 to 20 mm.b) nitrogen content of 1 to 39.5% by weight,c) oxygen content of 1%,d) ratio of .alpha.:.beta.-phase of 1:9 to 9:1.