Conclusions

♦ Increasing the particle size of the La,.,Sr,Mn03 cathode results in higher overpotentials, but lends long term stability at 1000°C. Increasing the cathode firing temperature increases the overpotential, although the microstructure remains fairly constant. Although 800°C yields the best initial results, after 24 h of operation the overpotential climbs sharply. We have found that 1000°C gives the best performance/stability combination. At 1 A/cm2, the cathodic overpotential is =0.1 V, which is very good

♦ Nonstoichiometric LaiSrMnMnOj(x=0.70,0.75, and 0.79) cathode compositions exhibit the best properties. Previously-summarized results showed that A-site deficient compositions exhibited the lowest overpotentials. To further explore this effect, we completed a series of studies using these compositions fired on at temperatures of 1100, 1200, 1300 and 1400°C. In all instances, I200°C was the optimum, with the x=0.70 composition being the best. It has an overpotential of only 0.04V at 1 A/cm2. SEM analyses indicated no second phases or interdiffusion is detectable. Longer time studies are underway.

Acknowledgment

The authors would like to thank the Department of Energy and the Gas Research Institute for their financial support.

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