In Situ Synchrotron X-ray Diffraction Study of the Sol-Gel Synthesis of Fe<inf>3</inf>N and Fe<inf>3</inf>C

Sol-gel chemistry is a powerful tool for the synthesis of porous or nanocrystalline structures of a wide range of materials. The morphology and composition of the final product can be strongly dependent on the mechanism that operates during the heating step, as has been demonstrated in many investigations of binary, ternary, and quaternary metal oxides. We demonstrate the complex phase transformations occurring in a transition-metal carbide (Fe<inf>3</inf>C, cementite) synthesis using in situ synchrotron X-ray diffraction. Our new study proves the existence of multiple intermediate phases and elucidates how oxide-nitride and nitride-carbide phase transformations can occur. This is particularly important as many transition-metal nitrides and carbides are metastable, which renders their stability windows sensitive to small changes in sol-gel methodology.