Abstract: The present invention relates to doped ceria (CeO2) abrasive particles, having an essentially octahedral morphology. Such abrasives are used in water-based slurries for Chemical Mechanical Polishing (CMP) of subrates such as silicon wafers. The invention more particularly concerns yttrium-doped ceria particles having a specific surface area of 10 to 120 m2/g, characterized in that at least 95 wt %, preferably at least 99 wt %, of the particles are mono-crystalline and in that the particles' surfaces consist of more than 70%, preferably of more than 80%, of planes parallel to {111} planes. A novel gas phase process for synthesizing this product is also disclosed, comprising the steps of providing a hot gas stream, —and, introducing into said gas stream a cerium-bearing reactant, a dopant-bearing reactant, and an oxygen-bearing reactant, —the temperature of said gas stream being chosen so as to atomize said reactant, the reactant being selected so as to form, upon cooling, doped ceria particles.