Ni-SDC cermet anode for medium-temperature solid oxide fuel cell with lanthanum gallate electrolyte

The polarization properties and microstructure of Ni-SDC (samaria-doped ceria) cermet anodes prepared from spray pyrolysis (SP) composite powder, and element interface diffusion between the anode and a La0.9Sr0.1Ga0.8Mg0.2O2-delta (LSGM) electrolyte are investigated as a function of anode sintering temperature. The anode sintered at 1250 degrees C displays minimum anode polarization (with anode ohmic loss), while the anode prepared at 1300 degrees C has the best electrochemical overpotential, viz., 27 mV at 300 mA cm(-2) operating at 800 degrees C. The anode ohmic loss gradually increases with increase in the sintering temperature at levels below 1300 degrees C, and sharply increases at 1350 degrees C. Electron micrographs show a clear grain growth at sintering temperatures higher than 1300 degrees C. The anode microstructure appears to be optimized at 1300 degrees C, in which nickel particles form a network with well-connected SDC particles finely distributed over the surfaces of the nickel particles. The anode sintered at 1350 degrees C has severe grain growth and an apparent interface diffusion of nickel from the anode to the electrolyte. The nickel interface diffusion is assumed to be the main reason for the increment in ohmic loss, and the resulting loss in anode performance. The findings suggest that sintering Ni-SDC composite powder near 1250 degrees C is the best method to prepare the anode on a LSGM electrolyte, (C) 1999 Elsevier Science S.A. All rights reserved.