Oxygen storage/release material and method for producing the same

An oxygen storage/release material comprising a ceria-zirconia-based composite oxide containing ceria (CeO2) and zirconia (ZrO2), wherein

• the ceria-zirconia-based composite oxide comprises, as an additional element, praseodymium (Pr) or neodymium (Nd),
• the ceria-zirconia-based composite oxide has, in at least a part thereof, at least one ordered phase of a κ phase and a pyrochlore phase,
• primary particles having particle diameters of 0.4 μm to 1.5 μm account for, on a particle number basis, 40% to 100% of all primary particles in the ceria-zirconia-based composite oxide, and
• when heated for 5 hours in the air at 1,100° C. and then examined by X-ray diffractometry using CuKα, the ceria-zirconia-based composite oxide exhibits an X-ray diffraction pattern in which an intensity ratio of a diffraction line at 2θ of 14.5° to a diffraction line at 2θ of 29° {I(14/29) value} is 0.015 or more and an intensity ratio of a diffraction line at 2θ of 28.5° to a diffraction line at 2θ of 29° {I(28/29) value} is 0.08 or less, and
• the oxygen storage/release material is obtained with the use of a fluorite-structured ceria-zirconia-based solid solution powder comprising, as an additional element, praseodymium (Pr) or neodymium (Nd), wherein, when heated for 5 hours in the air at 1,200° C., the solid solution powder satisfies conditions of a proportion y (%) of Ce0.5Zr0.5O2 crystals relative to entire crystals and a content x (% by weight) of praseodymium oxide (Pr6O11) or neodymium oxide (Nd2O3) represented by Formula (1):
• y≥−0.7079x2+5.3331x+9.4883 (1),
• wherein x≥0.6.