Composite oxide

Abstract

Provided is a composite oxide which is suitable as a co-catalyst for an exhaust gas purifying catalyst or the like, has high heat resistance, and has an excellent oxygen absorbing and desorbing capability at low temperatures. The composite oxide contains Ce and Zr, wherein the Ce content is 30 to 80 at % and the Zr content is 20 to 70 at %, based on the total of Ce and Zr being 100 at %, or further contains particular element M, wherein the Ce content is not less than 30 at % and less than 80 at %, the Zr content is not less than 20 at % and less than 70 at %, and the content of element M is more than 0 at % and not more than 15 at %, based on the total of Ce, Zr, and element M being 100 at %; wherein the composite oxide has CaF 2 -type or CaF 2 -like structure phase, wherein the ratio of an actual lattice parameter in the (311) plane to the theoretical is 1.000, and wherein the composite oxide has a property of exhibiting a total pore volume of not less than 0.30 cc/g after calcination at 1000° C. for 5 hours in the atmosphere.

1 . A composite oxide comprising Ce and Zr,
 wherein a content of Ce is not less than 30 at % and not more than 80 at % and a content of Zr is not less than 20 at % and not more than 70 at %, based on a total of Ce and Zr being 100 at %,   wherein said composite oxide has CaF 2 -type structure phase or CaF 2 -like structure phase,   wherein a ratio of an actual lattice parameter in the (311) plane to theoretical lattice parameter (actual value/theoretical value) is 1.000, and   wherein said composite oxide has a property of exhibiting a total pore volume of not less than 0.30 cc/g after calcination at 1000° C. for 5 hours in atmosphere.   
     
     
         2 . The composite oxide according to  claim 1  further comprising at least one element M selected from the group consisting of alkaline earth metal elements, rare earth metal elements other than Ce, transition metal elements other than rare earth metal elements and Zr, halogen elements, B, C, Si, and S,
 wherein a content of Ce is not less than 30 at % and less than 80 at %, a content of Zr is not less than 20 at % and less than 70 at %, and a content of element M is more than 0 at % and not more than 15 at %, based on a total of Ce, Zr, and element M being 100 at %. 
 
     
     
         3 . The composite oxide according to  claim 2 , wherein a content of Ce is not less than 40 at % and less than 60 at %, a content of Zr is not less than 40 at % and less than 60 at %, and a content of element M is more than 0 at % and not more than 10 at %, based on a total of Ce, Zr, and element M being 100 at %. 
     
     
         4 . The composite oxide according to  claim 2 , wherein said composite oxide comprises at least one element selected from the group consisting of La, Pr, and Y, as said element M. 
     
     
         5 . The composite oxide according to  claim 4 , wherein said composite oxide comprises La and Pr and/or Y as said element M. 
     
     
         6 . The composite oxide according to  claim 1 , wherein said composite oxide has a property of exhibiting an oxygen storage capacity of not less than 300 μmol per gram of the composite oxide at 400° C. 
     
     
         7 . The composite oxide according to  claim 1 , wherein said composite oxide has a property of exhibiting an oxygen storage capacity of not less than 500 μmol per gram of the composite oxide at 400° C. 
     
     
         8 . The composite oxide according to  claim 1 , wherein said composite oxide has a property of exhibiting a total pore volume of not less than 0.35 cc/g after calcination at 1000° C. for 5 hours in atmosphere.