Preparation and characterization of Nd_2-xSr_xCoO _4+δ cathodes for intermediate-temperature solid oxide fuel cell

K₂NiF₄-type structural Nd_2-xSr _xCoO_4+δ (x = 0.8, 1.0, 1.2) was synthesized and evaluated as cathodes for intermediate-temperature solid oxide fuel cell (IT-SOFC). The crystal structure, thermal expansion, electrical conductivity and electrochemical properties were investigated by X-ray diffraction, dilatometry, DC four-probe method, AC impedance and polarization techniques. It is found that the electrochemical properties were remarkably improved with the increasing of Sr in the experiment range. Nd_0.8Sr_1.2CoO _4+δ showed the highest electrical conductivity of 212 S cm ^-1 at 800 °C, the lowest polarization resistance and cathodic overpotential, 0.40 Ωcm² at 700 °C and 35.6 mV at a current density of 0.1 A cm^-2 at 700 °C, respectively. The chemical compatibility experiment revealed that Nd_0.8Sr_1.2CoO _4+δ cathode was chemically stable with the SDC electrolyte. The thermal expansion coefficient also increased with the Sr content.