Synthesis and properties of SmBaCo 2−x Ni x O 5+δ perovskite oxide for IT-SOFC cathodes

Abstract Double perovskite oxides SmBaCo 2− x Ni x O 5+ δ (SBCN x ) ( 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 SmBaCo 2 O 5+ δ (SBCO) in terms of structural characteristics, electrical properties, and electrochemical performance of SBCN x . At the given temperature, the electrical conductivities of SBCN x 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 ( R P ) of SBCN x on a Sm 0.2 Ce 0.8 O 1.9 (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 R P value (0.0464 Ω cm 2 at 800 °C) and high power density (536 mW cm −2 at 800 °C); thus, it may be a promising candidate for IT-SOFCs.