Property optimization for strontium-rich lanthanum chromium ferrite cathodes: A demonstration of lanthanide replacement effect

Abstract The structure, electrical conducting, thermal expansion and electrocatalytic properties of Ln0.3Sr0.7Fe0.7Cr0.3O3-δ (Ln = La, Pr, Nd, Sm) perovskites were investigated to evaluate their potential for cathodes of intermediate temperature solid oxide fuel cells (IT-SOFCs). Reducing the size of the lanthanide cations enhanced the deformation of the perovskite structures and decreased the dimension of the primitive unit cells. Meanwhile, the oxygen nonstoichiometry (δ) values at elevated temperatures slightly increased. The electrical conductivity degraded with smaller lanthanide cation sizes, while the thermal expansion coefficients (TECs) tended to decrease. These property changes were diagnosed with respect to the corresponding structural evolutions. Sm0.3Sr0.7Fe0.7Cr0.3O3-δ was identified to be the optimal composition after an overall property assessment. This composition exhibited an average TEC (∼14 × 10−6 K−1 between 40 and 1000 °C) compatible with IT-SOFC electrolytes, eligible electrical conductivity and good electrocatalytic activity. The good overall properties of Sm0.3Sr0.7Fe0.7Cr0.3O3-δ demonstrate that this composition is a promising cathode material for IT-SOFCs.