CERIA-ZIRCONIA COMPOSITE OXIDE, METHOD FOR PRODUCING THE SAME, AND CATALYST FOR PURIFYING EXHAUST

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A ceria-zirconia composite oxide includes at least one of lanthanum, yttrium, and praseodymium. A rate of a total content of the at least one rare earth element to a total content of cerium and zirconium is 0.1 at % to 4.0 at %. A content of the rare earth element present in near-surface regions, which are at a distance of less than 50 nm from surfaces of primary particles of the ceria-zirconia composite oxide, accounts for 90 at % or more of the total content of the rare earth element. An average particle size of the primary particles of the ceria-zirconia composite oxide is 2.2 μm to 4.5 μm. After a predetermined durability test, the intensity ratio I(14/29) of a diffraction line at 2θ=14.5° to a diffraction line at 2θ=29° and the intensity ratio I(28/29) of a diffraction line at 2θ=28.5° to the diffraction line at 2θ=29° respectively satisfy the following conditions : [in-line-formulae]I(14/29)≧0.02, and[/in-line-formulae] [in-line-formulae]I(28/29)≦0.08.[/in-line-formulae]