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

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The purpose of the present invention is to provide a composite oxide having high oxygen storage performance without using cerium. An iron oxide-zirconia composite oxide containing iron, zirconium and a rare earth element, said composite oxide being characterized in that the total content of Fe2O3, ZrO2 and an oxide of the rare earth element is 90 mass% or more, the content of iron oxide is 10 to 90 mass% in terms of Fe2O3 content, and the absolute value of a co-dispersed COV (Fe, Zr+X) content, which is determined in accordance with equations (1) to (3) (wherein Ii(Fe), Ii(Zr) and Ii(X) respectively represent the ratios of the X-ray intensities of iron, zirconium and the rare earth element each measured at a measurement point (i) (i = 1 to n) to the 100% intensities of the elements as measured by subjecting the composite oxide to a ray analysis by EPMA (WDX : wavelength dispersive X-ray spectroscopy) under predetermined conditions; and Rav(Fe) and Rav(Zr+X) respectively represent an average value of Ri(Fe) values and an average value of Ri(Zr+X) values both as measured at all of measurement points (n)), in the composite oxide that has been burned in the atmosphere at a temperature of 900˚C or higher for 5 hours or longer is 20 or less.