Oxygen permeation through Sr(Ln)CoO3−δ (Ln=La, Nd, Sm, Gd) ceramic membranes

Oxygen permeability of Sr0.65−xLa0.35CoO3−δ (x=0–0.10), Sr0.65La0.35Co0.90O3−δ and Sr0.7Ln0.3CoO3−δ (Ln=La, Nd, Sm, Gd) ceramics was studied under temperatures of 950–1250 K. The experiments held proved that the transfer of oxygen through the strontium cobaltite-based ceramics was limited both by the rate of oxygen exchange between oxides and gas phase and by ionic conductivity of the materials. It has been established that the permeability of materials studied increases rapidly with increase in oxygen partial pressure. A creation of vacancies in both cation sublattices of ABO3 perovskite results in decreasing oxygen permeation flux. Therewith, cation deficiency in the sublattice B of the cobaltites have a lower influence on oxygen permeability in comparison with ones in the sublattice A. Oxygen permeation flux through Sr(Ln)CoO3−δ ceramics decreases with decreasing mean radius of the cations in the sublattice A. Electrical conductivity of the cobaltites reduces when oxygen partial pressure diminishes or concentration of the cation vacancies increases.