Ceria-zirconia composite oxide, method for producing the same, and catalyst for purifying exhaust gas using the ceria-zirconia composite oxide

A ceria-zirconia composite oxide, containing a composite oxide of ceria and zirconia, comprising

• at least one rare earth element selected from the group consisting of lanthanum, yttrium, and praseodymium, wherein
• a rate of a total content of the at least one rare earth element to a total content of cerium and zirconium in the ceria-zirconia composite oxide is 0.1 at % to 4.0 at %,
• a content of the rare earth element present in near-surface regions accounts for 90 at % or more of the total content of the rare earth element, the near-surface regions being at a distance of less than 50 nm from surfaces of primary particles of the ceria-zirconia composite oxide,
• a content ratio of cerium to zirconium in the ceria-zirconia composite oxide is in a range from 43:57 to 48:52 by molar ratio,
• an average particle size of the primary particles of the ceria-zirconia composite oxide is 2.2 μm to 4.5 μm, and
• an intensity ratio I(14/29) of a diffraction line at 2θ=14.5° to a diffraction line at 2θ=29° and an 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:
• I(14/29)≧0.02;
• and
• I(28/29)≦0.08,
• wherein the intensity ratio I(14/29) and the intensity ratio I(28/29) are calculated from an X-ray diffraction pattern of the ceria-zirconia composite oxide, the X-ray diffraction pattern being obtained by an X-ray diffraction measurement using CuKα after heating the ceria-zirconia composite oxide under a temperature condition of 1100° C. in air for 5 hours.