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In the research of new cathode materials for Solid Oxide Fuel Cells, the cobaltite Ba 2 Co 9 O 14 shows attractive properties. Its good electronic conductivity (σ = 100–240 S.cm −1 between 450 to 650 °C) as well as a reversible partial reducibility without structural modification, evidenced above 400 °C, in favor of a possible O 2− mobility, suggests a possible mixed conductivity. These properties make it a potential material for SOFC cathode application. A good chemical compatibility between Ba 2 Co 9 O 14 and the classical electrolytes YSZ and CGO is evidenced. However, the cathode adhesion on both electrolytes is problematic due to its greater thermal expansion. Various composites [Ba 2 Co 9 O 14 –electrolyte] cathodes have been considered to improve the adhesion. Particular attention is paid on 70%wt. Ba 2 Co 9 O 14 –30%wt. YSZ and 70%wt. Ba 2 Co 9 O 14 –30%wt. CGO cathodes on dense YSZ and CGO, respectively. The cathode layers were deposited by hand-painting or screen-printing. The impedance spectroscopy carried out on symmetrical cells under air reveals that the deposition technique affects the polarization resistance. In the series of samples considered in our study, the screen-printed layer 70%wt. Ba 2 Co 9 O 14 –30%wt. CGO has the lowest polarization resistance: Rp(750 °C) = 0.5 Ω.cm 2 . The activation energies are about 1.1 eV in any case. |
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