PHASE-COMPOSITION, MICROSTRUCTURE, AND SINTERING IN THE SYSTEM CO-LI2CO3

Co and Li2CO3 were used as starting materials to obtain cobalt-based plaques of potential use in molten carbonate fuel cell technology. Samples were prepared by thermal treatments in the temperature range 800-1300 degrees C. Their composition and microstructure have been investigated at room temperature by X-ray diffraction analysis (Rietveld refinement), weight change and density data, porosimetry, and scanning electron microscopy. It is shown that a highly nonstoichiometric Co3O4 forms on lithium-containing samples in the entire temperature range investigated, while a stoichiometric Co3O4 is always obtained in the absence of Li. Moreover, clear evidence has been obtained that sinterization starts at lower temperatures on lithiated samples than on pure Co ones and that it causes the formation of consistent amounts of stoichiometric CoO in both types of sample. It is argued that the increased sinterization rate shown by Li-containing samples is due to the highly defective structure of their Co3O4 phase. (C) 1995 Academic Press, Inc.