Potentiality of Ba2Co9O14 as cathode material for IT-SOFC on various electrolytes

In the research of new cathode materials for Solid Oxide Fuel Cells, the cobaltite Ba2Co9O14 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 O2− mobility, suggests a possible mixed conductivity. These properties make it a potential material for SOFC cathode application. A good chemical compatibility between Ba2Co9O14 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 [Ba2Co9O14–electrolyte] cathodes have been considered to improve the adhesion. Particular attention is paid on 70%wt. Ba2Co9O14–30%wt. YSZ and 70%wt. Ba2Co9O14–30%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. Ba2Co9O14–30%wt. CGO has the lowest polarization resistance: Rp(750 °C) = 0.5 Ω.cm2. The activation energies are about 1.1 eV in any case.