Improved electrical and electrochemical performance of co-doped Nd1.8Sr0.2Ni1 − xCuxO4 + δ

• Maximum conductivity for x = 0.4 is understood on the basis of defect chemistry.
• Low-frequency impedance data simulated using Gerischer element
• Improved overall electrochemical performance due to extrinsic defects
• Nd1.8Sr0.2Ni0.8Cu0.4O4 + δ may be a potential cathode material for IT-SOFC.

Mixed conducting oxides of Nd1.8Sr0.2Ni1 - xCuxO4 + δ (x = 0.0, 0.2, 0.4, and 0.5) system are synthesized by combusting homogeneously mixed precursors under microwave heating. The Nd1.8Sr0.2Ni1 − xCuxO4 + δ solid solutions are of tetragonal structure in one single phase across the compositional range 0 ≤ x ≤ 0.5. The samples at x > 0.5 are multiphase. Nd1.8Sr0.2Ni0.6Cu0.4O4.01 exhibits maximum dc conductivity (σ = 42.7(3) S cm− 1 at 640 °C) and minimum activation energy (Ea = 0.07(3) eV). Minimum electrode polarization resistance value of 0.20(4) Ω cm2 (at 700 °C) is obtained for Nd1.8Sr0.2Ni0.6Cu0.4O4 + δ. Low-frequency complex impedance spectra corresponding to symmetric cells are modeled using Gerischer impedance. Oxygen partial pressure-dependent electrode polarization study suggests that the oxygen dissociation is the cathode reaction rate-limiting step.