Electronic Conductivity Measurement of Gd- and Sm-Doped Ceria Ceramics by Hebb-Wagner Method

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Gadolinium- and samarium-doped ceria powders with compositions Ce0.8Gd0.2O1.9 (GDC) and Ce0.8Sm0.2O1.9 (SDC) were prepared by heating the oxalate solid solution (Ce0.8R0.2)2(C2O4)3 (R: Gd, Sm) at 873 K in air. As-prepared powders with secondary particle size of 0.5-1 μm were densified to 96.6-99.4% relative density by sintering in air at 1773 K for 4 h. The electronic current of disk sample was measured in a temperature range from 773 to 1113 K by direct current polarization method using Hebb-Wagner ion blocking cell. A linear relationship, which was theoretically predicted, was measured between log I (electronic current) and E (applied voltage) for GDC and SDC in the applied voltage range of 0.2-1.4 V. The slopes of log σ (electronic conductivity)-log Po2 (oxygen partial pressure) plot for GDC agreed with the theoretically predicted value of -1/6. However, the slope for SDC was in the range from -0.10 to -0.16. The transport number of oxide ion for the GDC and SDC was significantly higher than the previously reported values.
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