Liquid dispersion and powder of cerium based core-shell particles, process for producing the same and uses thereof in polishing

A process for producing a dispersion of cerium based core-shell particles in a liquid, comprising the following steps:

• (a) providing an aqueous dispersion comprising particles of cerium oxide optionally doped with at least one metal (M);
• providing an aqueous solution comprising a cerium (III) salt;
• providing an aqueous peroxygen solution;
• and optionally providing an aqueous solution comprising at least one metal (M′) salt;
• and
• (b) contacting the aqueous dispersion with the aqueous solutions provided in step (a), while maintaining a temperature comprised between 0° C. and 80° C. and a pH lower or equal to 11, to produce the dispersion of cerium based core-shell particles;
• wherein at least one of the steps (a) and (b) is carried out in the presence of nitrate ions.