CERIUM-ZIRCONIUM TYPE COMPLEX OXIDE AND PRODUCTION METHOD THEREOF

PROBLEM TO BE SOLVED: To provide a cerium-zirconium type complex oxide which allows a pyrochlore phase to be present stably in a crystal structure even when exposed to high temperatures for a long time and is high in OSC and excellent in exhaust gas purification performance and its production method.SOLUTION: A cerium-zirconium type complex oxide comprises cerium, zirconium and one or more elements selected from rare earth elements other than cerium and alkaline earth metal elements. After a 3-h heat treatment at 1,000-1,100°C, (1) its crystal structure contains a pyrochlore phase; (2) it has a value of {I111/(I111+I222)}×100 of 1 or greater, with the peak intensity of the (111) plane taken as I111 and the peak intensity of the (222) plane as I222; and (3) it has an oxygen absorption/emission capacity at 450°C of 0.01 mmol/g or higher, an oxygen absorption/emission capacity at 600°C of 0.05 mmol/g or higher and an oxygen absorption/emission capacity at 750°C of 0.30 mmol/g or higher. 【課題】長時間高温に晒されても結晶構造中にパイロクロア相が安定に存在し，ＯＳＣが高く，排ガス浄化性能に優れるセリウム−ジルコニウム系複合酸化物及びその製造方法を提供する。【解決手段】セリウムと，ジルコニウムと，セリウムを除く希土類元素及びアルカリ土類金属元素から選ばれる少なくとも１種以上の元素と，を含む。１０００℃〜１１００℃で３時間の熱処理後において，（１）結晶構造はパイロクロア相を含み，（２）（１１１）面のピーク強度値をＩ１１１，（２２２）面のピーク強度値をＩ２２２として｛Ｉ１１１／（Ｉ１１１＋Ｉ２２２）｝?１００の値が１以上，（３）４５０℃での酸素吸放出能が０．０１ｍｍｏｌ／ｇ以上，６００℃での酸素吸放出能が０．０５ｍｍｏｌ／ｇ以上，７５０℃での酸素吸放出能が０．３０ｍｍｏｌ／ｇ以上，である。【選択図】図１