Supported perovskite-type oxides are described. The perovskite-type oxides have the general formula of A.sub.xA'.sub.x'B.sub.yB'.sub.y'O.sub.3-.delta., wherein A is an ion of a metal of Group IIIa or IIIb of the periodic table of elements or mixtures thereof; A' is an ion of a metal of Groups Ia or IIa of the periodic table or mixtures thereof; B and B' are ions of a d-block transition metal of the periodic table or mixtures thereof; x, x', y and y' vary from 0 to 1; 0.95