Optimization of Segmented-in-series Tubular SOFCs using an La(0.5)Sr(0.5-x)Ca(x)MnO(3) System Cathode and the Generation Characteristics Under Pressurization

• Published in: Denki kagaku oyobi kōgyō butsuri kagaku 2009-05, Vol.77 (5), p.379-387
• Main Authors: Tomida, K, Hisatome, N, Kabata, T, Tsukuda, H, Yamashita, A, Yamazaki, Y
• Format: Article
• Language: English
• ISSN: 1344-3542

In this research, we studied the optimization of a segmented-in-series tubular solid oxide fuel cell using LA(0.5)Sr(0.5-x)Ca(x)MnO(3) system materials for the cathode. La(0.5)Sr(0.25)Ca(0.25)MnO(3) (LSCM25) was chosen for the cathode to obtain high electric conductivity and prevent the formation of highly resistive second phases with Y(2)O(3)-stabilized ZrO(2) (YSZ) electrolyte as a result of X-ray diffraction. To obtain lower resistance at the cathode/electrolyte interface, we studied the optimization of the cathode interlayer by changing the LSCM25-YSZ volume ratio and YSZ particle sizes. As a result, the lowest resistance was obtained at 50 vol. % LSCM25 (particle size: 3 km) + 50 voL % YSZ (2 km). The area-specific resistance of a tubular cell stack using the LSCM25 cathode and the LSCM25-YSZ interlayer decreased by 17% compared to a stack using only an LSCM25 cathode. We also conducted power-generation tests under pressurization to measure the cell stack performance integrated with micro gas turbines. Judging from the I-V characteristics, an increase of test pressure brought about not only an increase of open circuit voltage but also a decrease of internal resistances. According to our analysis of the internal resistances using the current interruption method, the electrode polarizations decreased as the operating pressure rose.