Layered LnBa1−xSrxCoCuO5+δ (Ln = Nd and Gd) perovskite cathodes for intermediate temperature solid oxide fuel cells

The effects of Sr substitution on the crystal chemistry, phase stability, and electrochemical performance as cathodes in intermediate-temperature solid oxide fuel cells (IT-SOFCs) of the layered LnBa1−xSrxCoCuO5+δ (Ln = Nd and Gd) perovskites have been investigated. The LnBa1−xSrxCoCuO5+δ oxides crystallize in tetragonal P4/mmm symmetry for 0 ≤ x ≤ 0.75. The x = 0.75 samples show a significant improvement in electrochemical performance compared to the x = 0 samples for both Ln = Nd and Gd. In an electrolyte (La0.8Sr0.2Ga0.8Mg0.2O2.8)-supported single cell configuration (thickness = 0.50 mm), the Ln = Gd series shows an improved maximum power density from 468 mW cm−2 for the Sr-free (x = 0) sample to 530 mW cm−2 for the x = 0.75 sample. In the Ln = Nd system, the x = 0.75 sample shows a maximum power density of 562 mW cm−2. The Sr substitution was found to have negligible effect on the thermal expansion coefficients (TEC) between the x = 0 and x = 0.75 samples in both series.

► Substitution of Sr for Ba in LnBa1−xSrxCoCuO5+δ (Ln = Nd and Gd) improves performance without increasing TEC.
► Substitution of Cu for Co influences the crystal chemistry more profoundly than Sr for Ba.
► Electrical conductivity is significantly affected by tetragonal lattice distortion.
► The LnBa0.25Sr0.75CoCuO5+δ (Ln = Nd and Gd) composition exhibits the highest performance.