Combustion synthesis and characterization of LSCF-based materials as cathode of intermediate temperature solid oxide fuel cells

Nanocrystalline SOFC cathode materials of perovskite family, La1−xSrxM1−yCoyO3, where 0 < x ≤ 0.5, 0 < y ≤ 0.8 (M is transitional metal = Mn or Fe), have been synthesized at a relatively low temperature by combustion synthesis using alanine as a novel fuel. Detailed X-ray powder diffraction analyses show 47–96% phase purity in the as-synthesized powder and upon calcination at ∼825 °C single-phase material is obtained wherein the nanocrystallinity (crystallite size ∼19–24 nm) is retained. Densification studies of the materials are carried out within 900–1100 °C. The coefficient of thermal expansion (CTE) of these cathodes is measured. Electrical conductivity of the cathodes sintered at different temperatures are measured in the temperature range 700–900 °C and correlated with the density of the sintered materials. The electrochemical performances of Ni-YSZ anode-supported SOFC having YSZ electrolyte (∼10 μm) with CGO interlayer (∼15 μm) are studied with the developed cathodes in the temperature range 700–800 °C using H2 as fuel and oxygen as oxidant. Highest current density of ∼1.7 A/cm2 is achieved during testing at 800 °C measured at 0.7 V with a cathode composition of La0.5Sr0.5Co0.8Fe0.2O3. Precipitation of nanocrystalline grains over the core grains in porous microstructure of this cathode might be one of the reasons for such high cell performance.