EFFECT OF MOLTEN SALT SYNTHESIS CONDITIONS ON THE PARTICLE SIZE OF La_1-xSr_xMn_1-yFe_yO₃ PEROVSKITES

Perovskite-type oxides such as La_1-xSr_xMn_1-yFe_yO₃ are promising materials for solid oxide fuel cells and catalysis. The traditional solid-state synthesis of these perovskites uses metal-oxide powders as starting materials and a high temperature thermal treatment with limited control over the product properties. Molten salt synthesis (MSS) offers an alternative route for synthesizing mixed oxides in a one-step, simple and versatile procedure.

Molten salts provide a liquid-phase medium for the perovskite formation process, enhancing the mass transport rates and therefore decreasing the time and temperature required for the synthesis. The variety of available salts and salt mixtures allows for diversity in synthesis conditions, yielding different results and morphologies. In order to take the full advantage of this diversity, there is a need to understand the factors that control the particle size and morphology of synthesized perovskites.

In this work, La_1-xSr_xMn_1-yFe_yO₃ was successfully synthesized for the first time in molten alkali chlorides. XRD confirmed pure perovskite structure of synthesized materials. Fe content (y=0-0.5) was found to affect the morphology of the final product, while the type of salt influenced the size of the obtained particles. Synthesis of LaMn_1-yFe_yO₃ in LiCl-KCl eutectic mixture yielded larger particles than synthesis in NaCl-KCl or KCl. It was also found that feeding the metal precursors into the molten salt mixture at the synthesis temperature yields smaller and more uniform particles. These results contribute to the understanding of MSS based on the nucleation and crystal growth model.