Co-firing of anode-supported SOFCs with Thin La _0.9Sr _0.1Ga _0.8Mg _0.2O _3-δ electrolytes

Anode-supported solid oxide fuel cells (SOFCs) with thin La0.9 Sr0.1 Ga0.8 Mg0.2 O3-δ (LSGM) electrolytes and (Ce0.6 La0.4) O2-δ (LDC) barrier layers were studied. The cells were fabricated by first colloidally depositing an LDC/LSGM/LDC tri-layer on a NiO-LDC anode support and co-firing. Cathodes consisting of LSCF-LSGM (LSCF= La0.6 Sr0.4 Fe0.8 Co0.2 O3-δ) were then deposited and fired. Cell tests in air and humidified hydrogen showed maximum power densities of 0.91 W cm2 at 700°C and 0.60 W cm2 at 650°C. The relatively good performance indicated that the LDC layers were effective in minimizing interdiffusion and reaction. However, the open-circuit voltage of these cells was ∼0.1 V lower than the Nernst potential; observations of electrolyte microstructure and composition indicated that this was due to electronic conductivity in the LSGM layer, resulting from Ni impurities that entered during co-firing with the NiO-LDC anode. While the LDC layers were necessary, impedance measurements indicated that they substantially increased the cell ohmic resistance.