ACTIVE-SITES IMAGING FOR OXYGEN REDUCTION AT THE LA0.9SR0.1MNO3-X YTTRIA-STABILIZED ZIRCONIA INTERFACE BY SECONDARY-ION MASS-SPECTROMETRY/

Active sites for oxygen reduction were investigated at the interface o f O-2/La0.9Sr0.1MnO3-x (LSM)/yttria-stabilized zirconia (YSZ). Isotopi c oxygen (O-16/O-18) exchange under cathodic polarization and secondar y-ion mass spectrometry (SIMS) analysis were examined to visualize the oxygen reduction active sites. The LSM mesh pattern electrode was pre pared to define the contact area of LSM/YSZ. Under cathodic polarizati on, oxygen can diffuse through the dense LSM via oxygen vacancy, which promotes the electrode reaction. By SIMS imaging technique, the activ e sites for oxygen reduction were clearly determined as spots around t he O-2/LSM/YSZ three-phase boundary. The Line analysis of the SIMS ima ge enabled us to draw a contour map of the O-18 concentration in the c ross section of YSZ. The diffusion paths were clearly visualized in th e contour map. The width of the active sites for oxygen reduction is e stimated to be less than 1 mu m under the examined condition.