Process for producing optically translucent mullite ceramic

Claim 1

A process for producing a polycrystalline mullite body optically translucent in the visible wave length which comprises providing an amorphous shapeless mixed oxide powder consisting essentially of from about 74 weight % to about 76.5 weight % Al 2 O 3 balance SiO 2 with a surface area ranging from about 100 square meters per gram to about 400 square meters per gram and a bulk density ranging from about 0.2 g/cc to about 0.3 g/cc containing a significant amount of water, calcining said powder at a temperature ranging from about 490° C. to about 1100° C. to remove water and any organic material therefrom leaving no significant amount thereof producing an amorphous shapeless mixed oxide powder consisting essentially of from about 74 weight % to about 76.5 weight % Al 2 O 3 balance SiO 2 , said calcining having no significant effect on the oxide composition or morphology of said powder, said calcined powder being pressable at about room temperature into a compact having a minimum density of 1.0 g/cc, pressing said calcined powder into a compact having a minimum density of 1.0 g/cc, and sintering said compact in an atmosphere of oxygen at a temperature ranging from about 1700° C. to about 1850° C. producing a sintered body of theoretical density based on the density of 3.16 g/cc±0.01 or 3.17 g/cc±0.01 for said mullite body.