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

Abstract

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 (La(0.9)Sr(0.1)Ga(0.8)Mg(0.2)O(3-delta)) 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 (similar to 20 mu m-thick) was sintered and then mounted on a LSGM cylindrical-ring (similar to 400 mu m-thick) by sintering two pieces together at 1500 degrees 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 degrees C, respectively. SSC (Sm(0.5)Sr(0.5)CoO(3-delta)) slurries were also brush painted for cathode on the opposite side and the cathode/electrolyte/anode layers were fired at 900 degrees C. The cell with the anode sintered at 1300 C showed the highest performance (OCV similar to 1.1 V, P(max), or maximum power density similar to 0.93 W/cm(2) at 700 C). The increase of the anode-firing temperature reduced the cell performance. Although the anode fired at 1375 degrees C showed a reduced OCV (similar to 0.90 V at 700 degrees C), the cell performance was still high (P(max): similar to 0.55 W/cm(2) at 700 degrees C). The cell with the anode fired at 1400 degrees C showed the lowest OCV (similar to 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. (C) 2010 Elsevier B.V. All rights reserved.