Provided is an inexpensive
oxygen storage material having an excellent
oxygen release performance at low temperature. One aspect of the present disclosure relates to a
composite oxide having a composition represented by a general formula Ce2-w-x′AwA′x′B1-y′-zB′y′B″zO6-w / 2-x′-y′ / 2-z. In the formula, A is one or more elements selected from rare-earth
metal elements excluding Ce, A′ is one or more elements selected from
alkaline earth metal elements, B is one or more elements selected from the group consisting of Ti and Group 14 elements, B′ is one or more elements selected from the group consisting of Group 13 elements, B″ is one or more elements selected from the group consisting of Group 12 elements, 2−w−x′, w, x′, 1−y′−z, y′, z, and 6−w / 2−x′−y′ / 2−z are mole ratios of Ce, A, A′, B, B′, B″, and O, respectively when B+B′+B″ is assumed to be 1, w, x′, y′, and z satisfy 0≤w<2, 0≤x′<0.5, 0≤y′≤1, 0≤z≤0.5, respectively, and w+x′ satisfies 0≤w+x′<2, and y′+z satisfies 0≤y′+z≤1.