Patent ID: 8242046

Claim:
A particulate inorganic oxide comprising: aluminum oxide; a metal oxide forming no composite oxide with aluminum oxide; and an additional element including at least one of a rare-earth element and an alkali earth element, the inorganic oxide containing a secondary particle formed by aggregating primary particles, wherein at least a part of the secondary particle includes: a plurality of first primary particles, each having a particle size of 100 nm or less, containing aluminum oxide and the additional element; and a plurality of second primary particles, each having a particle size of 100 nm or less, containing the metal oxide and the additional element; wherein both of the first and the second primary particles has a surface concentrated region where the additional element has a locally increased content in a surface layer part thereof; and wherein a content of the additional element in terms of an amount of an oxide thereof is 5.6 mol % or less with respect to a total amount of the additional element, aluminum in aluminum oxide, and metal in the metal oxide.