Patent ID: 7625546

Claim:
An alkaline-earth or rare-earth metal aluminate precursor compound, characterized in that it has the following characteristics: it has a composition given by the formulae: a(M 1 O).b(MgO).c(A1 2 O 3 ) (1) or a(M 2 O 1.5 ).b(MgO).c(A1 2 O 3 ) (2) in which M 1 denotes an alkaline-earth metal and M 2 denotes yttrium or a combination of cerium and terbium, and a, b and c are integers or nonintegers that satisfy the relationships: 0.25≦a≦4; 0≦b≦2 and 0.5≦c≦9; it is crystallized in the form of an alumina having a transitional alumina crystal structure; it is in the form of substantially spherical and chemically homogeneous particles; and these particles include pores, the mean diameter of which is at least 10 nm.