The electrolyte tile of molten carbonate fuel cells consists of a matrix prepared from lithium aluminate powders impregnated with molten alkaline metal carbonate. The increase in Lithium aluminate particle size in the molten carbonate accelerates degradation of the electrolyte tile. We investigated the mechanism of lithium aluminate particle growth. Results indicate that, although the particles basically grow through a dissolution-precipitation mechanism, with lithium aluminate passing through the molten carbonate, growth tends to occur readily in the interior of agglomerates resulting from the coagulation of fine particles. As fine pores fill fully with lithium aluminate precipitate in the interior of the agglomerates, and then are amalgamated into other surrounding particles, the particles can grow at higher rates than individual particles, which grow by the dissolution-precipitation mechanism.