Patent ID: 6933259

Claim:
A composite oxide powder, consisting essentially of: a mixture of particles of an oxide of metal M 1 which is cerium and an oxide of a metal M 2 which is at least one element selected from the group consisting of aluminum, titanium and silicon and which does not dissolve in said oxide of metal M 1 , wherein the cerium oxide constitutes more than 50% by wt of the composite oxide powder said mixture having been calcined at 600° C. for 5 hours or at 800° C. for 5 hours, and wherein the calcination of said mixture when calcined at 600° C for 5 hours results in a composite oxide powder having a porosity such that pores in the size range of 3.5 to 100 nm in diameter have a volume of 0.13 cc/g or more and when calcined at 800° C. for 5 hours results in a composite oxide powder having a porosity such that the pores in the size range of 3.5 to 100 nm in diameter have a volume of 0.10 cc/g or more.