Three aluminum salts are investigated as a sintering aid for the in situ sintering of electrolyte matrices for molten carbonate fuel cells (MCFCs). Only aluminum acetylacetonate shows a potential, At or above 420 degreesC, aluminum acetylacetonate changes to Al2O3 and reacts with Li2CO3 in the electrolyte to produce gamma -LiAlO2. This reaction product forms necks between matrix particles. Necks grow with increasing sintering time and correspondingly, the mechanical strength of the electrolyte matrix shows an abrupt increase, starting at a sintering time of about 100 h until it levels off at about 250 h. The porosity of the matrices fabricated with aluminum acetylacetonate is in the range acceptable for use in MCFCs.