Influence of fuel on morphology of LSM powders obtained by solution combustion synthesis

• Nanocrystalline LSM powders were obtained by combustion synthesis.
• Urea, sucrose and a mix of these fuels were used in the precursor solution.
• The use of sucrose significantly increases the specific surface area.
• The morphology and texture of LSM powders are significantly influenced by the fuel type and amount.

Combustion synthesis is a simple and reproducible method used to obtain fine ceramic powders, which can be used in energy-generation devices such as solid oxide fuel cells (SOFCs). Strontium-doped lanthanum manganites (LSM) are materials applied commonly as cathodes in a SOFC and can be obtained by combustion synthesis. Different combustion synthesis routes of LSM were evaluated in this paper, considering the influence of fuel amount and type in the phase formation and morphology of the powders. Moreover, a new fuel mixture, urea and sucrose, was proposed for the preparation of LSM powders. The synthesized powders showed significant loss of mass when obtained with 200% excess of oxidizers, and the use of urea resulted in single-phase powders directly from the combustion reaction. After calcination, a single-phase rhombohedral perovskite phase was identified in all powders. A larger specific surface area of calcined powders (34.9 m2/g) and a smaller crystallite (sized 18 nm) were obtained using sucrose as fuel, followed by the synthesis with mixed fuels (13.2 m2/g and 26 nm). These results were correlated with the morphology of the aggregates, which was visibly influenced by the nature of the precursor solution. The mixed fuels combustion led to a powder where the particles aggregated in a form of submicrometric hollow structures.

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