Effects of anode firing temperature on the performance of the lanthanum-gallate thick-film-supported SOFC

The reaction between lanthanum-gallate electrolyte and Ni in the anode often occurs during the co-firing of an anode-supported cell and results in the degradation of cell performance. In this study, a thick-film LSGM (La0.9Sr0.1 Ga0.8 Mg0.2O3-δ) electrolyte-supported micro-cell was fabricated and electrochemically tested to see the effects of the anode-firing temperature on the SOFC performance. The LSGM tape (~ 20 μm-thick) was sintered and then mounted on a LSGM cylindrical-ring (~ 400 μm-thick) by sintering two pieces together at 1500 °C. NiO-GDC (Gd-doped ceria) slurries were brush painted for the anode on the bottom surface of the supporting LSGM electrolyte and the electrolyte/anode layers were subsequently fired at 1300, 1350, 1375 or 1400 °C, respectively. SSC (Sm0.5Sr0.5CoO3−δ) slurries were also brush painted for cathode on the opposite side and the cathode/electrolyte/anode layers were fired at 900 °C. The cell with the anode sintered at 1300 °C showed the highest performance (OCV ~ 1.1 V, Pmax or maximum power density ~ 0.93 W/cm2 at 700 °C). The increase of the anode-firing temperature reduced the cell performance. Although the anode fired at 1375 °C showed a reduced OCV (~ 0.90 V at 700 °C), the cell performance was still high (Pmax: ~ 0.55 W/cm2 at 700 °C). The cell with the anode fired at 1400 °C showed the lowest OCV (~ 0.27 V). The open-circuit voltage (OCV) and thus the performance of the cells were largely dependent upon the anode-firing temperature since the reaction of Ni with the LSGM electrolyte induces an electronic conduction in the LSGM electrolyte which then decreases the OCV.