Patent ID: 7919429

Claim:
A zirconia-ceria-yttria-based mixed oxide comprising, on an oxide basis, 40 to 90% of ZrO 2 , 5 to 50% of CeO 2 , 5 to 30% of Y 2 O 3 , and 0 to 30% of at least one oxide of rare earth element other than Ce and Y; the zirconia-ceria-yttria-based mixed oxide having a stable crystal structure after 12 hours of heat treatment at 1100° C. under a reducing atmosphere; and the zirconia-ceria-yttria-based mixed oxide having a specific surface area of 15 m 2 /g or more after 12 hours of heat treatment at 1100° C. under a reducing atmosphere, and a further 3 hours of heat treatment at 1100° C. under air.