Effect of cation substitution at the B site on the oxygen semi-permeation flux in La0.5Ba0.5Fe0.7B0.3O3−δ dense perovskite membranes with B = Al, Co, Cu, Mg, Mn, Ni, Sn, Ti and Zn (part II)

• The rate determining step of oxygen flux through the membranes is clearly determined.
• The kinetics of oxygen surface exchanges depend mainly on the B-site substitution.
• The oxygen bulk diffusion depends on the specific free volume.
• The value of the specific free volume depends mainly on the A-site substitution.

The aim of this paper is to provide insight into the effect of cation substitution at the B site on the oxygen semi-permeation performances. Particular attention is given here to identify the impact of cation substitution at the B site on oxygen diffusion and oxygen surface-exchange kinetics in the La0.5Ba0.5Fe0.7B0.3O3−δ perovskite membrane series with B = Al, Co, Cu, Mg, Mn, Ni, Sn, Ti and Zn.This study clearly shows that the prediction of the oxygen semi-permeation performances of membrane materials from the nature of cation at the A or B sites in perovskite structure is quite complex. The cation substitution at the B-site has a low impact on the nature of rate-determining step and a significant impact on oxygen semi-permeation performances, contrary to the cation substitution at A-site. Unfortunately, it is not possible to establish a relevant trend about the effect of the nature of cation in the A or B sites in perovskite structure on oxygen diffusion and the oxygen surface-exchange kinetics.