A study was made of isothermal changes in the O non-stoichiometry of the perovskite-type material, La0.8Sr0.2MnO3, at 945 to 1255K. A thermogravimetric method was used to monitor the rate of gas/solid equilibration. For degrees of equilibration greater than 0.5, the equilibration kinetic data could be described by a diffusion equation. The associated chemical diffusion coefficient depended mainly upon the O partial pressure. Its temperature dependence could be described by:

D (cm2/s) = 1.9 x 10-3 exp[-83.4(kJ/mol)/RT]

D (cm2/s) = 1.6 x 10-3 exp[-121.2(kJ/mol)/RT]

at low and high O partial pressures, respectively.

Equilibration Kinetics of (La,Sr)MnO3. M.Rekas, T.Bak, J.Nowotny, C.C.Sorrell, Y.Zhao, K.Foger, E.R.Vance: Journal of Materials Science – Materials in Electronics, 2000, 11[9], 697-702