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electrolyte at temperatures above 500°C. Below this temperature the electrolyte remains ionic and electrolyte at temperatures above 500°C. Below this temperature the electrolyte remains ionic and

Fig. 2 Fraction of Ce4+ ions reduced to Ce3* as a function of temperature and p02

Fig. 2 Fraction of Ce4+ ions reduced to Ce3* as a function of temperature and p02

Electronic conductivity in the electrolyte is evident from the measured values of the open circuit voltage (OCV) when compared to the Nernst potential as shown in the following table.

Temperature (°C) Theoretical OCV. mV Measured OCV. mV

500 1054 995

700 997 869

Electrochemical Characterization

Figure 3 plots the performance from 500 to 700°C of a cell with the following configuration: Lao.6Sro.4Coo.2Feo.sO3 (LSCF) / CeosGdo.20i.9 Electrolyte /Ni-Ce0.sGd0.2O,.v

Current Density (nWan1)

Fig. 3 Cell performance with a 1.2 mm thick electrolyte, LSCF cathode and Ni-cermet anode

Current Density (nWan1)

Fig. 3 Cell performance with a 1.2 mm thick electrolyte, LSCF cathode and Ni-cermet anode

It shows that the performance of the cell at 500°C is inadequate. We found that the majority of the voltage losses apart from the electrolyte resistance were at the cathode electrolyte interface. Figure 4 shows the proportion of the voltage loss from the cathode compared to the anode. The electrolyte loss can be reduced by using 10- and 20-pm-thick electrolytes as shown on the right side of fig. 1. Cathode performance improvement requires either new microstructures or new materials that are more active while being compatible with the electrolyte.

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