COMPOSITE OXIDE, METHOD FOR PRODUCING THE SAME, AND CATALYST FOR EXHAUST GAS PURIFICATION

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PROBLEM TO BE SOLVED : To provide a composite oxide and a catalyst for purifying exhaust gas using the same, which oxide has excellent heat resistance, including that a large specific surface area is maintained even when the composite oxide is used in a high temperature environment, and that, even after calcination at 800°C for 2 hours, an AECeO3 phase which deteriorates performance is not detected and increase in CeO2 crystallite size is inhibited. SOLUTION : The composite oxide contains 50-98 mass% of a rare earth metal element containing Y, Zr and Al in terms of oxides, 1-30 mass% of an alkaline earth metal element in terms of oxides, and 1-20 mass% of Si in terms of SiO2, wherein the rare earth metal element containing Y, and Zr contains Ce, and at least one kind selected from a rare earth metal element containing Y and not containing Ce, Zr and Al at the mass ratio in the range of 85 : 15 to 100 : 0 in terms of oxides, and the specific surface area by BET method after calcination at 800°C for 2 hours shows ≥60 m2/g, and an AECeO3 phase is not detected by X-ray diffraction after calcination at 800°C for 2 hours, and the CeO2 crystallite size on (111) plane is ≤15 nm. COPYRIGHT : (C)2013, JPO&INPIT