In case of catalytic activity, the presence of oxygen vacancies act as adsorption sites for the reactants and enhance the catalytic activity.

I don't know what kind of activity you're expecting but it depends on different cases

The unit cell of Ni Al2 O4 structure which the anions (oxygen) form close packed cubic, in whichthe cations Ni and Al occupy the tetrahedral and octahedral sites. The cation distrbution depend on three principle factors . The ionic radii of the metallic ions, their electronic configuration and the modeling energy of the lattice .( The activation energy of the sample) .

Each anion ( Oxygen with large radii) in the dpinel structure is surrondeing cations.

The same things for the Berovskit type compound structure Ni Al O3

Notice.

I am sorry for delay, there is some problems in electricity and web net in Sana'a Yemen

The rare-earth doping will create oxygen vacancies in the lattice which act as a center for adsorption and enhance the catalytic activity towards methanation.