COMPOSITE OXIDE MATERIAL AND EXHAUST GAS PURIFICATION CATALYST USING SAME

摘要

The object of the present invention is to provide an oxygen storage material used for an exhaust gas purifying catalyst that is superior in stability at high temperatures. The composite oxide material of the invention comprises crystalline particles of a ceria-zirconia composite oxide with a pyrochlore structure and crystals of a lanthana-zirconia composite oxide with a pyrochlore structure existing on the particle surface, in which the crystals of the lanthana-zirconia composite oxide is solidly dissolved in at least a part of the surface of the crystalline particles of ceria-zirconia composite oxide. In the composite oxide material according to the present invention, the pyrochlore structure of the ceria-zirconia composite oxide is stabilized, and the decrease in oxygen storage capacity resulting from phase shift into the fluorite structure is suppressed.