Evaluation of the La_(0.75)Sr_(0.25)Mn_(0.8)Co_(0.2)O_(3 - delta) system as cathode material for ITSOFCs with La_9Sr_1Si_6O_(26.5) apatite as electrolyte

摘要

In the past years, a major interest has been devoted to decrease the working temperature of solid oxide fuel cells (SOFCs) down to about 700 deg C. Apatite materials (La_(10 - x)Sr_xSi_6O_(27 - x/2)) are attractive candidates for solid electrolytes, with a high ionic conductivity at 700 deg C, a chemical and a dimensional stability for a pO_2 ranging from 10~(-25) to 0.2 atm. A perovskite oxide (La_(0.75)Sr_(0.25)Mn_(0.8)Co_(0.2)O_(3 - delta)) has been used as a cathode material. Symmetrical cathode/electrolyte/cathode cells were fabricated by stacking layers obtained by tape casting of apatite and perovskite powders and co-sintering at 1400 deg C for 2 h in air. Impedance spectroscopy measurements were performed on these cells in order to determine the electrode resistance. It has been shown that the latter decreases with the porosity content of the cathode and with the use of a composite material (apatite/perovskite) instead of a simple perovskite.