THE TYPES OF SURFACE EXCHANGE AND DIFFUSION OF OXYGEN IN LA0.7SR0.3COO3-DELTA

The kinetics of the oxygen isotopic exchange between La0.7Sr0.3CoO3-de lta and oxygen gas has been studied at on oxygen pressure of 1.28 x 10 (3) Pa and temperatures from 786 to 875 degrees C. Experimental time d ependencies of molecules (OO)-O-16-O-16, (OO)-O-18-O-16, (OO)-O-18-O-1 8 content in the gas phase have been analyzed by the method first prop osed by the authors. Using this method we have directly calculated bot h the rates of the different types of surface exchange and the bulk di ffusivity of oxygen from experimental data. It has been shown that und er the experiment conditions at elevated temperatures the surface exch ange proceed by the dissociative adsorption-desorption mechanism. (C) 1998 Published by Elsevier Science B.V. All rights reserved.