Enhancement of oxygen permeation flux through the La1.5Sr0.5Ni1-yMnyO4+δ ceramic membranes by manganese doping

Abstract

The single-phase La1.5Sr0.5Ni1-yMnyO4+δ (y = 0, 0.1, 0.2 and 0.3) dense ceramic membranes of different thickness were fabricated by sintering at 1350 °C in air. The oxygen permeation flux through the La1.5Sr0.5Ni1-yMnyO4+δ membranes slightly decreases at y≤0.2 and increases by more than one order of magnitude in the 0.2 ≤ y ≤ 0.3 range due to a significant increase in the surface oxygen exchange rate. The surface study of La1.5Sr0.5Ni1-yMnyO4+δ by Electron backscatter diffraction technique reveals that manganese doping affects the orientation of crystallites and induces the appearance of planes with higher Miller indices, which are characterized by smaller reticular densities of the 3d-metals. The analysis of the effective paramagnetic moments for La1.5Sr0.5Ni1-yMnyO4+δ shows that manganese doping leads to the formation of mixed Mn3+/Mn4+ oxidation state when y>0.1. As compared to La1.5Sr0.5Ni0.8Mn0.2O4+δ, the significant decrease in surface limitations of the oxygen exchange process at the oxide/gas interface for La1.5Sr0.5Ni0.7Mn0.3O4+δ correlates with the increase in Mn4+ concentration.