Quantitative Analysis of Microstructural Change at the Interface Between (La,Sr)MnO[sub 3] Cathode and YSZ Electrolyte upon Discharge Operation

The microstructural change at the interface between (LSM) cathode and yttria-stabilized zirconia (YSZ) electrolyte upon discharge was quantitatively evaluated by focused ion beam-scanning electron microscopy technique so as to elucidate the activation process of cathode. The performance of the single cell was enhanced soon after the current passage up to at due to the reduction in impedance at the cathode. In response to this electrochemical behavior, the interfacial structure between LSM and YSZ changed depending on the time duration of discharge; the roughness of YSZ surface both in and out of contact with LSM particles increased with time. Furthermore, the closed pores were formed at the well-adhered LSM/YSZ interface, which were unexposed to the cathode gas. The triple phase boundary-length (TPB-length) of the as-prepared sample was evaluated to be , whereas after the discharge at for the total TPB-length was increased to . In the latter case, however, the active TPB-length was , which was only 7% larger than that of as-prepared one. Then the contribution rate of TPB-length to the performance enhancement of cathode was discussed.