| Résumé | The effect of composition of (1-x) Sm0.5Sr0.5CoO3 (SSC) + x Sm0.2Ce0.8O1.9 (SDC) cathodes (x = 0, 10, 25, 40 wt%) sintered at 1000°C for 2 hrs has been investigated using symmetric cells with Sm0.2Ce0.8O1.9 (SDC) electrolytes. The results showed that an increase in SDC content in the composite cathodes led to an increase in cathode resistance (Rc). The Rc values on average were 0.042 Ω·cm2 for the cathode without SDC addition, 0.063 Ω·cm2 for the cathode with 10 wt% SDC, 0.079 Ω·cm2 for the cathode with 25 wt% SDC, and 0.207 Ω·cm2 for the cathode with 40 wt% SDC at 650°C. The calculated activation energy values of the composite cathodes were in the range of 120 ± 20 kJ·mol-1. We also investigated an in-situ (650°C) sintered SSC cathode, and found that it showed the lowest Rc value, approximately 0.028 Ω·cm2 at 650°C. No obvious voltage degradation under constant current density (0.5 A·cm-2) has been observed in the cells with 1000o C-sintered SSC with 25 wt% SDC at 650°C in air over 100 hrs. However, the cell with in-situ sintered SSC cathode showed a steady decay rate of -4 mV/hr. EIS analysis of the cell before and after the stability test revealed that the degradation resulted entirely from an increase of electrode polarization resistance. |
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