Takeshi Komatsu

Chemical reactivity of LaNi0.6Fe0.4O3LaNi0.6Fe0.4O3 (LNF) with Cr2O3Cr2O3 has been investigated in order to examine the long-term stability of the LNF phase at 1073K1073K , which shows a high performance as the cathode of intermediate-temperature solid oxide fuel cells (IT-SOFCs). The chemical stability of LNF was compared with that of La0.8Sr0.2MnO3La0.8Sr0.2MnO3 (LSM) under the existence of Cr2O3Cr2O3 . The LNF powder, a powder mixture of LNF and Cr2O3Cr2O3 , and a powder mixture of LSM and Cr2O3Cr2O3 were, respectively, heated at 1073K1073K , and they are analyzed by X-ray powder diffraction with the Rietveld refinement. We found that the LNF phase maintains the hexagonal crystal system heated in air up to 1000h1000h . In the LNF-Cr2O3LNF-Cr2O3 mixture, the LNF phase kept its pristine crystal structure while a new phase, NiCr2O4NiCr2O4 , was detected, which was produced by the reaction between Cr2O3Cr2O3 and the residual NiONiO contained in the starting LNF powder. In the LSM-Cr2O3LSM-Cr2O3 mixture, LSM reacted with Cr2O3Cr2O3 and produced a significant amount of MnCr2O4MnCr2O4 . LNF showed a much better chemical stability against Cr2O3Cr2O3 than LSM. LNF can serve as a long-life cathode in the IT-SOFC system.

We have investigated the effect of Cr poisoning on various cells which consist of either (LNF) or (LSM) as a cathode and either yttria-stabilized zirconia (YSZ) or alumina-doped scandia stabilized zirconia (SASZ) as the electrolyte. It was found that the cathodic overvoltage was almost the same for cells with LNF cathodes, either in the presence or absence of Cr-containing alloy (Inconel 600). LSM cathodes in the presence of Inconel 600 exhibited a very steep increase in voltage curves after applying the current. These results indicate that the LNF cathode is electrochemically stable for Cr poisoning compared with the LSM cathode.