COMPLEX OXIDE, METHOD FOR PRODUCING SAME AND EXHAUST GAS PURIFYING CATALYST

摘要

Disclosed are: a complex oxide which has excellent heat resistance and excellent reduction rate, and is capable of maintaining high specific surface area even in cases where the complex oxide is used in a high-temperature environment; a method for producing the complex oxide; and an exhaust gas purifying catalyst which utilizes the complex oxide. Specifically disclosed is a complex oxide which contains cerium and rare earth metal elements including yttrium but not including cerium at a mass ratio of from 85:15 to 99:1 in terms of oxides, while containing silicon in an amount of more than 0 part by mass but 20 parts by mass or less in terms of SiO2 relative to the total of 100 parts by mass of the cerium and the rare earth metal elements including yttrium but not including cerium in terms of oxides. The complex oxide has a specific surface area of not less than 40 m2/g as determined by a BET method after being fired at 900°C for 5 hours and a reduction rate of not less than 30% as calculated from the results of a temperature-programmed reduction measurement from 50°C to 900°C after being fired at 1000°C for 5 hours. The complex oxide is particularly suitable as a promoter for an exhaust gas purifying catalyst that is used for automobiles and the like.