Ln2–x Y x CuO4+δ (Ln = Pr, Nd, Sm; x = 0, 0.025, 0.05, 0.1) cathode materials were synthesized using a sol–gel method and calcination at 1000 °C for 24 h. The phase structure, coefficient of thermal expansion (CTE), electrical conductivity, and electrochemical impedance of cathode materials were characterized. X-ray diffraction (XRD) patterns show that the cell volume of each cathode material decreases with the increase in the Y3+ doping amount and has good chemical compatibility with the Sm0.2Ce0.8O1.9 electrolyte. The thermal expansion test shows that the increase in Y3+ doping reduces the average CTE of Ln2CuO4+δ. The conductivity test shows that Y3+ doping increases the conductivity of Ln2CuO4+δ, and Pr1.975Y0.025CuO4+δ has the highest conductivity of 256 S·cm–1 at 800 °C. The AC impedance test shows that Y3+ doping reduces the polarization impedance of Ln2CuO4+δ, and Pr1.9Y0.1CuO4+δ has a minimum area-specific resistance (ASR) of 0.204 Ω·cm2 at 800 °C. In conclusion, Pr1.975Y0.025CuO4+δ has the best performance and is more suitable as a cathode material for a solid oxide fuel cell (SOFC).

The increase in Ca for Nd0.8−xSr0.2CaxCoO3−δ limits the electronic compensation capacity, resulting in a decrease in CTE. The Ca-doped material maintains good electrochemical properties under CTE reduction and thus can be used as an IT-SOFC cathode.

Nd0.6Sr0.4Co1−xCuxO3−δ (x = 0, 0.05, 0.1, 0.15, 0.2) (NSCCx) was prepared by replacing Co with Cu.