Patent ID: 7553465

Claim:
A cerium oxide powder, consisting of: crystalline primary particles comprising cerium oxide and having carbonate groups on the surface of the crystalline primary particles and in a region close to the surface of the crystalline primary particles, wherein the powder has a BET surface area of from 25 to 150 m 2 /g, the crystalline primary particles have a mean diameter of from 5 to 50 nm, the region close to the surface of the crystalline primary particles is about 5 nm deep from the surface of the crystalline primary particles, the carbonate concentration in the region close to the surface of the crystalline primary particles decreases inwards from the surface on which the carbonate concentration is highest, the carbon content due to the carbonate groups on the surface of the crystalline primary particles is from 5 to 50% by area and the carbon content in the region at a depth of about 5 nm from the surface of the crystalline primary particles is from 0 to 30% by area, the content of cerium oxide, calculated as CeO 2 and based on the total weight of the powder, is at least 99.5% by weight and the content of carbon, encompassing organic and inorganic carbon, is from 0.01 to 0.3% by weight, based on the total weight of the powder.