A New Composite Material Ca3Co4O9+δ+La0.7Sr0.3CoO3 Developed for Intermediate‐Temperature SOFC Cathode

In this study, Ca₃Co₄O_9+δ (CCO) and La_0.7Sr_0.3CoO₃ (LSC) have been mixed as mass fraction by 1:1, to prepare novel two‐phase composites with high electrical conductivity and low thermal expansion coefficient (TEC), for potential application in intermediate‐temperature solid oxide fuel cells. The conductivity of the composite, Ca₃Co₄O_9+δ (50 wt.%) + La_0.7Sr_0.3CoO₃ (50 wt.%) (CCO‐LSC50), is improved to be three times that of single phase CCO material. And, the TEC of CCO‐LSC50 has been effectively improved to be 15.3 × 10^–6 °C^–1, about 20% lower than single phase LSC cathode, which ensures better chemical compatibility with adjacent electrolyte. As a result, compared with pure LSC and CCO cathodes, CCO‐LSC50 composite cathode improves the electrochemical performance, a percentage of 16 and 84%, respectively, according to the impedance spectra experiments. In addition, cathodic overpotential and oxygen reduction kinetics have also been researched to reveal what is driving the results. The microstructures and phases of cathodes were also compared and analyzed.