Advanced preparation of ceramic powders

Claim 1

A process for the preparation of sinterable metal oxide ceramic powders, comprising the steps of: (a) forming a first solution of an ammonia donor in a water-miscible organic liquid and a second solution of salts of all the metals whose oxides are present in said metal oxide ceramic powders, said second solution also containing sufficient water to produce by reaction with the ammonia donor in said first solution a sufficient amount of ammonia to precipitate at least part of the cations of the metal salts in said second solution when such ammonia is released into the said second solution; (b) mixing said first solution and said second solution while maintaining a temperature of at least 60° C. in the reaction vessel, so as to form a solid precipitate containing at least part of the ceramic metal content originally in said second solution; (c) treating said solid precipitate with alkali for a sufficient time to prevent discoloration of the precipitate upon subsequent heating to 400° C.; (d) neutralizing the alkali remaining after said treating of part (c) to produce a pH of 7.0±0.2 in the liquid phase in contact with said solid precipitate; (e) separating the solid phase remaining after part (d) from the bulk of the liquid phase present therewith after part (d); (f) washing the solid phase remaining after part (e) with sufficient aqueous ammonia to remove substantially all the soluble inorganic matter and the last traces of organic matter from said solid phase. (g) drying and calcining the solid phase remaining after part (f) by heating it for a sufficient time at a temperature sufficient to yield a stable crystal phase and degree of hydration if any for sintering but not so high as to cause appreciable sintering or coarsening of particle size in said solid phase.