Evaluation of Nd_0.8- Sr_0.2Ca CoO_3- (x = 0, 0.05, 0.1, 0.15, 0.2) as a cathode material for intermediate-temperature...

A series of Nd_0.8- Sr_0.2Ca CoO_3- (x = 0, 0.05, 0.1, 0.15, 0.2) cathode materials was synthesized by sol-gel method. The effect of Ca doping amount on the structure was examined by scanning electron microscopy (SEM), X-ray diffraction (XRD), thermal expansion, and X-ray photoelectron spectroscopy (XPS). Electrochemical properties were evaluated for possible application in solid oxide fuel cell (SOFC) cathodes. Results showed that second phase NdCaCoO₄₊ is generated when the Ca doping amount is higher than 0.1. The increase in Ca limits the electronic compensation capacity of the material, resulting in a decrease in thermal expansion coefficient (TEC). With the increase of Ca content, the conductivity increases at first and then decreases, and the highest value of 443 S cm^-1 is at x = 0.1 and T = 800 °C. Nd_0.7Sr_0.2Ca_0.1CoO_3- exhibits the lowest area specific resistance of 0.0976 Ω cm² at 800 °C. The maximum power density of Nd_0.7Sr_0.2Ca_0.1CoO_3- at 800 °C is 409.31 mW cm^-2. The Ca-doped material maintains good electrochemical properties under the coefficient of thermal expansion (CTE) reduction and thus can be used as an intermediate-temperature SOFC (IT-SOFC) cathode.