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

Abstract

Gadolinium- and samarium-doped ceria powders with compositions of Ce_0.8Gd_0.20_1.9 (GDC) and Ce_0.8Sm_0.20_1.9 (SDC) were prepared by heating the oxalate solid solution (Ce_0.8R_0.2)₂(C₂O₄)₃ (R : Gd, Sm) at 873 K in air. As-produced powders with secondary particle size of 0.5-1 μm were densified to 96.6-99.4 ^oC 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. The slope of log σ (electronic conductivity) - log P_O2 (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 numbers of oxide ion for the present GDC and SDC were significantly higher than the previously reported values.