Process for producing fine-crystalline alpha quartz

摘要

A process for producing a fine-crystalline alpha -quartz with a crystal size of from 0.08 to 0.8 mm comprises crystallization of amorphous silica in the atmosphere of water vapours in the presence of a crystallization promoter - a substance possessing basic properties in an amount of from 1x10<-3>to 1% by weight of amorphous silica at a temperature within the range of from 300 to 500 DEG C under a pressure of from 20 to 400 atm for 5 to 100 hours. Exemplified crystallization promoters are alkali metal hydroxides, NH4OH, quaternary ammonium bases, polyethyleneimines, hydrazine and alkyl derivatives of hydrazine. The present invention can be useful in the manufacture of quartz glass and quartz ceramics.