Oxide Ion Transport in Promising Cobaltites for SOC
Résumé
Two cobaltites were studied as air electrodes for Solid Oxide Cells with a Cerium Gadolinium Oxide electrolyte (CGO): Ca3Co4O9+δ, well known for its thermoelectric properties, and Ba2Co9O14. After optimisation of composition and thickness, a very good ASR of only 0.08 Ω.cm2 was obtained for the 50 wt% Ba2Co9O14 - 50 wt% 50CGO composite. In contrast, a value of 0.5 Ω.cm2 was reached for the 50 wt% Ca3Co4O9+δ - 50 wt% CGO composite. Although, Ba2Co9O14 sample contained 18O after annealing, oxide ion diffusion in this compound still has to be confirmed. In contrast, high surface exchange kinetics were measured for both Ca3Co4O9+δ and NdBaCo2O5+δ, for which mainly calcium and barium/neodymium were evidenced at the uppermost surface of the samples, whose atoms may play a key role in the mechanism of oxygen molecules dissociation.