Permeation studies of the Sr4Fe6-xCoxO13 system, where x ranged from 0 to 2, were carried out. Samples which had been prepared by using solid-state techniques consisted of a single phase for x-values of between 0 and 1.5, and a 3-phase mixture of perovskite and spinel phases for x-values of between 1.5 and 2. Samples which had been prepared by using a sol-gel method consisted of single-phase Sr4Fe4Co2O13 over the entire range of x-values. The compositions which consisted of 3-phase mixtures exhibited O permeation fluxes which were an order of magnitude higher than those for single-phase samples. The higher O permeation rate of the former samples was attributed to the perovskite phase, since the single-phase perovskite, SrFe0.75Co0.25O3, passed O two orders of magnitude more rapidly than did single-phase Sr4Fe4Co2O13. The latter samples exhibited stable O permeation rates as a function of time. The Sr4Fe6-xCoxO13 samples which consisted of 3-phase mixture exhibited a decrease in O permeation with time.

Role of Perovskite Phase in the Oxygen Permeation Properties of the Sr4(Fe,Co)6O13 System. T.Armstrong, F.Prado, Y.Xia, A.Manthiram: Journal of the Electrochemical Society, 2000, 147[2], 435-8