Abstract: A ceria-zirconia-based composite oxide oxygen storage material with a fast oxygen storage rate having an OSC ability enabling fast response to changes in exhaust gas which does not greatly fluctuate in composition, but varies at a fast rate near the stoichiometric air-fuel ratio, an exhaust gas purification catalyst, and a honeycomb structure for exhaust gas purification are provided. A ceria-zirconia-based composite oxide oxygen storage material, which oxygen storage material has a molar ratio of cerium and zirconium, by cerium/(cerium+zirconium), of 0.33 to 0.90, has an ion conductivity measured by an AC impedance method of 1×10?5S/cm or more at 400° C., and contains metal ions M of one or more types of rare earth elements selected from Sm3+, Eu3+, Pr3+, Gd3+, and Dy3+ with a coordination number of over 7.0 in an amount of 0.5 mol % to 15 mol % with respect to the total amount of cations.

Abstract: A ceria-zirconia-based composite oxide oxygen storage material with a fast oxygen storage rate having an OSC ability enabling fast response to changes in exhaust gas which does not greatly fluctuate in composition, but varies at a fast rate near the stoichiometric air-fuel ratio, an exhaust gas purification catalyst, and a honeycomb structure for exhaust gas purification are provided. A ceria-zirconia-based composite oxide oxygen storage material, which oxygen storage material has a molar ratio of cerium and zirconium, by cerium/(cerium+zirconium), of 0.33 to 0.90, has an ion conductivity measured by an AC impedance method of 1×10?5 S/cm or more at 400° C., and contains metal ions M of one or more types of rare earth elements selected from Sm3+, Eu3+, Pr3+, Gd3+, and Dy+3 with a coordination number of over 7.0 in an amount of 0.5 mol % to 15 mol % with respect to the total amount of cations.