IRON OXIDE-ZIRCONIA COMPOSITE OXIDE AND METHOD FOR PRODUCING SAME, AND EXHAUST GAS PURIFICATION CAT

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A composite oxide with a high oxygen storage capacity is provided without using cerium. The composite oxide is an iron oxide-zirconia composite oxide containing iron, zirconium, and a rare-earth element. The total content of Fe2O3, ZrO2, and an oxide of the rare-earth element is not less than 90 mass%, the content of an iron oxide in terms of Fe2O3 is 10 to 90 mass%, and the absolute value of the covariance COV(Fe, Zr + X) of the composite oxide, which has been baked in the atmosphere at a temperature of greater than or equal to 900°C for 5 hours or more, determined by the following Formulae (1) to (3), is not greater than 20 : [Math. 1] RiFe=IiFe×100IiFe+IiZr+IiXRi⁢Zr+X=IiZr+IiX×100IiFe+IiZr+IiXCOV⁢Fe, Zr+X=1n∑i=1nRiFe-RavFe×Ri⁢Zr+X-Rav⁢Zr+X (in the formula, Ii(Fe), Ii(Zr), and Ii(X) respectively represent the ratios of the X-ray intensities of iron, zirconium, and the rare-earth element measured at a measurement point i (where i = 1 to n) to the 100% intensities of the respective elements as measured by subjecting the composite oxide to a ray analysis through EPMA (WDX : wavelength dispersive X-ray spectrometry), where Rav(Fe) and Rav(Zr + X) represent the mean values of Ri(Fe) and Ri(Zr + X), respectively, at all measurement points n).