A LNF-GDC composite cathode with a gradual change in the composition between ScSZ electrolyte and LNF cathode was fabricated to reduce the cathode polarization resistance (Rp). The gradual change in composition between ScSZ electrolyte and LNF cathode shows the decreases in the charge transfer resistance (Rct) and gas phase diffusion resistance (Rd). The results revealed that the Rp value, measuring 0.452 Ω·cm2 at 750 °C, was the lowest for LNF-GDC composite cathodes with three layers and gradient changes in composition between ScSZ and LNF (Cathode C),, whereas the Rp value of 70%LNF-30%GDC composite cathodes with one layer (Cathode A) was 0.581 Ω·cm2. The reduction in Rp for the LNF-GDC composite cathodes with three layers and gradient changes in composition between ScSZ and LNF may be related to the fact that the microstructure of the cathode/electrolyte interfaces is significantly improved, resulting in the increase in the area of triple phase boundaries (TPBs), which enhanced the surface exchange of oxygen. This implied that the gradient LNF-GDC composite cathodes showed excellent performance in terms of its electrochemical properties.
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