Oxygen bulk diffusion and surface exchange in Sr-substituted La2NiO4 + δ

The oxygen bulk diffusion and surface exchange in Sr-substituted La2NiO4 + δ were investigated separately in this work. The oxygen flux through La2−xSrxNiO4 + δ (x = 0.1 and 0.2) was measured as a function of temperature and the oxygen self diffusion coefficients, DO, were extracted. The results show that the higher the Sr concentration, the lower the oxygen permeation and the higher the activation energy of DO. The surface exchange rate was determined by measuring isotope exchange with a mass spectrometer. The Sr substitution leads to higher surface exchange rate with lower activation energy. The incorporation of ionized atomic oxygen into surface vacancies was suggested to be the rate determining step.