This invention relates to a
cerium-
zirconium-base
composite oxide, which is useful, e.g., for the purification of
exhaust gas discharged from
combustion engines such as internal
combustion engines and boilers and can release a high level of
oxygen in a low temperature region, a method for producing the same, an
oxygen storage / release component using the same, an
exhaust gas purification catalyst, and an
exhaust gas purification method. The
cerium-
zirconium-base
composite oxide satisfies requirements (1) that the
oxygen release
initiation temperature is 380° C. or below, (2) that the oxygen release amount is not less than 485 μmol / g, and further (3) that the oxygen release amount at 400° C. is not less than 15 μmol / g. The
cerium-
zirconium-base
composite oxide can be produced, for example, by mixing a starting material for cerium and a starting material for zirconium at a predetermined
mixing ratio together, melting the starting material mixture at a temperature at or above the
melting point, then cooling the melt to form an
ingot, then optionally
grinding the
ingot to prepare
powder, subsequently removing strain within
powder crystal grains under heating, and then
grinding to a further fine state.