Synthesis and properties of SmBaCo2−xNixO5+δ perovskite oxide for IT-SOFC cathodes

Double perovskite oxides SmBaCo2−xNixO5+δ (SBCNx) (x=0-0.5) are synthesized via an EDTA-glycine process as cathodes for intermediate temperature solid oxide fuel cells (IT-SOFCs). In this study, we investigate the effects of Ni substitution for the Co sites in SmBaCo2O5+δ (SBCO) in terms of structural characteristics, electrical properties, and electrochemical performance of SBCNx. At the given temperature, the electrical conductivities of SBCNx decrease as the Ni content increases, and SBCO exhibits a maximum conductivity of 1091 S cm−1 at 250 °C. The average thermal expansion coefficients (TEC) over the temperature range of 25-800 °C show a decreased trend from 19.96×10−6 K−1 for SBCO to 16.26×10−6 K−1 for SBCN0.5, while the average TEC of SBCN0.3 reaches a minimum of 15.59×10−6 K−1. Generally, the power density of a single fuel cell at 600-800 °C decreases as the Ni content increases, whereas the polarization resistance (RP) of SBCNx on a Sm0.2Ce0.8O1.9 (SDC) electrolyte is enhanced. Among all of the samples, SBCN0.3 exhibits a combination of low thermal expansion (15.59×10−6 K−1), a reasonably low RP value (0.0464 Ω cm2 at 800 °C) and high power density (536 mW cm−2 at 800 °C); thus, it may be a promising candidate for IT-SOFCs.