ON THE MECHANISTIC ASPECTS OF LaMO₃ (M = Mn, Al, Fe) MOLTEN SALT SYNTHESIS

La-based perovskites are an interesting class of oxides potentially applied in solid oxide fuel cells and catalysis. In the traditional synthesis methods, the formation of perovskite crystals occurs via a process in the solid phase, limiting the ability to control the product properties, especially morphology and crystal size. Molten salt offers a unique liquid medium for the perovskite formation potentially enhancing the control of its properties. However, in order to fully utilize the advantage of molten salt synthesis, there is a need for deeper understanding of the mechanistic aspects and the factors affecting the perovskites formation process. In this work, pure phase LaMO₃ (M = Mn, Al, Fe) perovskites were synthesized in molten LiCl-KCl and KF-KCl eutectic mixtures at various temperatures (600-850°C) and reactants crystal size/morphology. The synthesis temperature had minor effect on the obtained perovskites crystal size for the given salt, while the salt type effect was much more pronounced yielding larger crystals in LiCl-KCl due to its low melting point. Heating the mixture of La- and M-precursors with the salt to the synthesis temperature yielded large La-perovskite crystals, while when La- and M-precursors were introduced to the molten salt heated to synthesis temperature, much smaller crystals were obtained. In addition, sampling the molten salt reaction medium during the synthesis revealed the process rate and product morphology evolution. These results shed light on the kinetic and mechanistic aspects of the perovskites formation in molten salts involving nucleation and crystal growth phenomena.