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Current Density, mAJar?

Fig. 5 Interface resistance of cathode electrolyte interface for different cathodes

This hypothesis is supported by the diffusion coefficients of some cathode materials measured on dense samples by isotope (O18) exchange and SIMS which are given in figure 6.

Two phase cathodes performed better still as shown by cathodes A and B in fig. 5. In addition cathode A has the ability to lose oxygen more easily than all other cathodes. This caused an increase in performance with increasing current density.

While the ability of the cathode material to lose oxygen increases the electrode performance for the materials considered, it is also known that this can cause an expansion mismatch with other fuel cell components. It is desirable then to work with materials that exhibit a constant performance at

Current Density (nWarf)

Fig. 4 Voltage losses in the fuel cell showing the large magnitude of the cathode loss

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