Reduced-Temperature Firing of Anode-Supported Solid Oxide Fuel Cells

Abstract

Anode-supported solid oxide fuel cells (SOFCs) with yttria-stabilized zirconia (YSZ) electrolytes were successfully co-sintered at a temperature as low as 1250 o C, substantially lower than the usual 1400 o C, by using 1 mol.% Fe 2 O 3 sintering aid. The effect of sintering temperature on cell electrochemical performance was investigated for cells with two different composite cathodes: (La 0.8 Sr 0.2 ) 0.98 MnO 3-δ (LSM) – YSZ or La 0.6 Sr 0.4 Fe 0.8 Co 0.2 O 3-δ (LSCF) – Gd-doped ceria (GDC). For the latter case, the electrolyte included a 3-µm-thick GDC layer that was co-sintered with the YSZ electrolyte and Ni-YSZ anode. Open-circuit voltages were near theoretical values within measurement accuracy for all cells. The LSM-cathode cell maximum power densities increased with decreasing sintering temperature, due to an anode resistance decrease. Cells with LSCF cathodes had substantially lower cathode polarization resistance than the LSM cells, yielding lower total resistance and higher power density. This was despite slightly higher than expected ohmic resistance for the GDC/YSZ bi-layer electrolytes; although this might be explained by the formation of a low-conductivity ceria-zirconia mixed phase by GDC/YSZ interdiffusion, energy-dispersive x-ray analysis did not detect interdiffusion. Micro-chemical analysis did not detect any zirconate formation in the LSCF/GDC/YSZ region.