An in situ diffraction study of a solid oxide fuel cell system

The design of a synchrotron diffraction experiment on a working SOFC air-electrode is outlined. A large number of diffraction data sets were collected successfully from LSM/YSZ/Ag cells under different polarization states at 850 degrees C. Systematic changes are observed in lattice parameters and FWHM's for the LSM phase when the cell is polarized. The peak positions for the YSZ electrode are unchanged throughout the entire experiment. This is the first experimental evidence that oxygen stoichiometry in LSM is strongly influenced by the electrochemical reactions which take place. The cell parameters increase under reducing conditions, due to a decrease in the oxygen content of the LSM. All observed changes seem to be reversible.