Effects of microstructure on oxygen transport in perovskite-type oxides

La0.1Sr0.9Co0.9Fe0.1O3-d (LSCF) particulates with different microstructures were prepared and oxygen sorption kinetics on these particulates was studied by a gravimetric method. The surface reaction on the crystallite surface is the rate-limiting step for oxygen sorption in loosely packed LSCF powders. In this case the sorption kinetics can be described by a linear driving force model with crystalline size independent sorption and desorption surface reaction rate constants. Oxygen sorption and transport rates are affected by the intercrystalline (grain boundary) resistance for LSCF particulates prepared with a press-sintering step, and in these cases both crystalline and particulate sizes determine the oxygen sorption rates. Sorption rate constant increases when increases the oxygen partial pressure of the atmosphere surrounding the LSCF samples.