The permeation of O through dense membranes which had been prepared by using various routes (standard ceramic or organic precursors) was measured. This revealed that an important role was played by the processing conditions and microstructure in determining permeation fluxes. A higher permeability of ceramics which had been produced by using the ceramic route was attributed to a lower grain-boundary resistance to O transport. The experimental data were also compared with the results of a numerical modelling of O transport that was based upon isotopic diffusion in single crystals. The ionic conduction of ceramics with a smaller grain size was lower than that of single crystals; thus suggesting the existence of a significant grain boundary resistance. The O permeability of material which had been prepared by using standard ceramic synthesis, involving higher sintering temperatures, was higher than expected. This suggested the occurrence of easy diffusion along grain boundaries. The effect of the ceramic microstructure upon the total conductivity and thermal expansion was found to be negligible.

Mixed Electronic and Ionic Conductivity of LaCo(M)O3 (M = Ga, Cr, Fe or Ni) - Effect of Preparation Method on Oxygen Transport in LaCoO3. V.V.Kharton, E.N.Naumovich, A.V.Kovalevsky, A.P.Viskup, F.M.Figueiredo, I.A.Bashmakoy, F.M.B.Marques: Solid State Ionics, 2000, 138[1-2], 135-48