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Figure 2

Accordingly, the air electrode with an SDC inter-layer showed excellent long-term durability and structural stability.

V-I characteristics of single cells with different electrodes: a) LSM cathode and Ni/YSZ anode, b) LSM cathode with SDC inter-layer and Ni/YSZ anode, and c) LSM cathode with SDC intcr-Iaycr and Ni/CeYSZ anode.

Temperature : 1000'C Current Density : 0.3A/cm

Figurc3

Temperature : 1000'C Current Density : 0.3A/cm

0 1000 2000 3000 4000 5000.

Operation Time (hr) Long-term test of single cells: a) without the SDC layer, b) with the SDC intcr-Iayer at the cathode/electrolyte interface.

4. Fuel electrode with a mixed conductor

In order to increase the electrochemically active sites of the fuel electrode, 10 mole % CeOj was doped to YSZ in the Ni-YSZ cermet. The doping of Ce02 causes the YSZ in the cermet to have higher electronic conductivity because the Ce4t ion can be reduced to Ce3* as it is described by the following reaction.

Ce^ + Ox0 = 2Ce' Vo"+ l/202 (2) The electrical neutralization condition can be expressed as:

Applying the law of mass action and substituting equation (3) into equation (2), the [Ce'J is found to be proportional to (Po2)""6, where Po2 is oxygen partial pressure. Therefore, the electronic conductivity of 10 mole % Ce02-doped YSZ (CeYSZ) increases with reduction of oxygen partial pressure and is expected to have about 1 x 10-' Scm-' at Po2 of 1 x 10"ls atm. This value is almost equivalent to the ionic conductivity of YSZ and thus indicates the „

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