Patent ID: 6887289

Claim:
A process for producing a sol which particles are dispersed in a medium, wherein the particles have a particle size of 0.005 to 1 Î¼m and comprise as a main component crystalline cerium oxide of the cubic system and as an additional component a lanthanum compound, neodymium compound or a combination thereof, wherein the additional component is contained in X/(Ce+X) molar ratio of 0.001 to 0.5 in which X is lanthanum atoms, neodymium atoms or a combination thereof, characterized in that the process comprises the steps: a first step of reacting an aqueous solution which a cerium (III) salt is mixed with a lanthanum (III) salt, a neodymium (III) salt or a combination thereof in an aqueous medium in X/(Ce+X) molar ratio of 0.001 to 0.5, with an alkaline substance in (OH âˆ’ )/(Ce 3+ +X 3+ ) molar ratio of 3 to 30 to give a suspension in which cerium (III) hydroxide and a hydroxide of the trivalent additional component X are homogeneously mixed; and a second step of blowing oxygen or a gas containing oxygen into the suspension at a temperature of 10 to 95Â° C.