Abstract

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.