The O self-diffusion coefficients and the activation energies for O self-diffusion, in manganite and cobaltite perovskites, were studied as a function of the occupation of the A and B sites of the ABO3 structure. The electrical conductivity was measured in the case of the manganites, and the permeability was determined in the case of the cobaltites. The self-diffusivity increased, with increasing x-value, in La1-x(Sr,Ca)x(Mn,Co)O3. This was attributed to the formation of new O vacancies which occurred upon introducing metals of lower valency (M2+) into the A3+ sites. The substitution of M2+ for B3+, or reduction of the metal (in the B3+ site) to a lower positive valency, also increased the self-diffusivity. The self-diffusivity in the cobaltites was higher, than that in the manganites, by 4 to 6 orders of magnitude. However, the high O fluxes which this would permit appeared to be limited by surface exchange kinetics. The activation energies for self-diffusion in the manganites were considerably higher than those found in the case of the cobaltites.

S.Carter, A.Selcuk, R.J.Chater, J.Kajda, J.A.Kilner, B.C.H.Steele: Solid State Ionics, 1992, 53-56, 597-605