Ceria-zirconia complex oxide material and method for producing same

A method for producing an oxygen storage material, the oxygen storage material comprising:

• zirconia particles and
• a ceria-zirconia complex oxide supported on the zirconia particles, wherein the ceria-zirconia complex oxide includes a pyrochlore phase and has a mean crystallite diameter of 10 nm to 22.9 nm,
• the method comprising the following steps in order:
• (i) a step of preparing an aqueous solution containing:
• a water-soluble cerium salt,
• a water-soluble zirconium salt or oxyzirconium salt,
• a complexing agent that is an alkylcarboxylic acid and/or an alkylcarboxylic acid salt, and
• zirconia particles,
• (ii) adding an aqueous alkali solution to the aqueous solution of (i),
• (iii) holding the aqueous solution mixture of (ii) at a temperature of 180° C. to 220° C. for 0.5 hours to 72 hours to produce a solid product by precipitation,
• (iv) holding the solid product at a temperature of 500° C. to 700° C. for 1 hour to 5 hours and then at a temperature of 700° C. to 1100° C. for 1 hour to 5 hours, and
• (v) further subjecting the solid product to temperature-programmed reduction treatment.