CERIUM-ZIRCONIUM-BASED COMPOSITE OXIDE AND METHOD FOR PRODUCING SAME

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Provided are a cerium-zirconium-based composite oxide that has an excellent OSC, high catalytic activity and excellent heat resistance, and a method for producing the same. The cerium-zirconium-based composite oxide comprises cerium, zirconium and a third element other than these two elements. The third element is either (a) a transition metal element or (b) at least one element selected from a rare earth element and an alkaline earth metal element. After a heat treatment at 1000-1100°C for 3 hours, the cerium-zirconium-based composite oxide shows the following characteristics : (1) the crystal structure contains a pyrochlore phase; (2) the value {I111/(I111+I222)}×100 is 1 or greater [wherein I111 stands for a peak strength on a (111) plane measured by X-ray diffractometry; and I222 stands for a peak strength on a (222) plane measured by X-ray diffractometry]; and (3) the oxygen absorption/emission performance at 600°C is 0.05 mmol/g or greater and the oxygen absorption/emission performance at 750°C is 0.3 mmol/g or greater.