Oxygen tracer diffusion (D*) and surface exchange rate constant (k*) were measured, using isotopic exchange and depth profiling by secondary ion mass spectrometry, in La1−xSrxFe0.8Cr0.2O3−δ (x = 0.2, 0.4 and 0.6). Measurements were made as a function of temperature (700–1000C) and O partial pressure (0.21–10−21atm) in dry O, water vapour and water-vapour/H/N mixtures. At high O activity, D* was found to increase with increasing temperature and Sr content. The activation energies for D* in air were 2.13eV (x = 0.2), 1.53eV (x = 0.4) and 1.21eV (x = 0.6). As the O activity decreased, D* increased as expected qualitatively from the increase in O vacancy concentration. Under strongly reducing conditions, the measured values of D* at 1000C ranged from about 10−8cm2/s for x = 0.2 to about 10−7cm2/s for x = 0.4 and 0.6. The activation energies determined at constant H2O/H2 ratio were 1.21eV (x = 0.2), 1.59eV (x = 0.4) and 0.82eV (x = 0.6). The surface exchange rate constant of O for the H2O molecule was similar in magnitude to that for the O2 molecule and both increase with increasing Sr concentration.

Oxygen Diffusion and Surface Exchange in La1-xSrxFe0.8Cr0.2O3-δ (x = 0.2, 0.4 and 0.6). T.Ramos, A.Atkinson: Solid State Ionics, 2004, 170[3-4], 275-86