EP0451958A1 — Method for preparing zircon powder

USPTO Abstract

A method for preparing zircon powder, which comprises mixing (1) silica sol and (2) an aqueous zirconium oxychloride solution having a concentration which would be from 0.1 to 2 mols/ℓ after mixed with the silica sol, in a SiO₂/ZrO₂ molar ratio of from 0.95 to 1.10, heating the mixture to hydrolyze the zirconium oxychloride, followed by dehydration treatment to obtain a powder, heating the powder from room temperature to a calcination temperature over a period of from 0.7 to 30 hours and calcining the powder at a temperature of from 1,200 to 1,400°C for a period of time satisfying the relation of: t ≧ 116 - 0.08T where t is the calcination time in hours and T is the calcination temperature in degrees Centigrade, or heating the powder from room temperature to a calcination temperature over a period of from 0.8 to 70 hours and calcining the powder at a temperature higher than 1,400°C and not higher than 1,700°C for a period of time satisfying the relation of: t ≧ 18 - 0.01T where t is the calcination time in hours and T is the calcination temperature in degrees Centigrade.