The electronic conductivity of pure ceria with two different impurity levels is examined by dc polarization technique based on the Hebb-Wagner ion blocking method. The impurity level for the ceria with 99.999% purity (5N-CeO(2)) is about 1/100 of that with 99.9% purity (3N-CeO(2)) as confirmed by the fluorescence intensity of impurities obtained by Raman spectroscopy. The electronic conductivity for the 5N-CeO(2) was measured at T = 973 K to 1173 K. and the results are essentially the same as those for the 3N-CeO(2). The electronic conductivity increases with decreasing of P(O(2)) following slope values of -1/4 to -1/6. The -1/4 dependent region becomes narrower for the 5N-CeO(2) than that for the 3N-CeO(2). For both types of ceria, the P(O(2)) independent region appears in the same region of higher than 10(-2) and 10(-3) MPa at T = 1073 K and 973 K, respectively. Activation energies for the 5N-CeO(2) were 2.2 eV, 2.6 eV and 1.9 eV in P(02) dependent regions of -1/6, -1/4 and 0, respectively. (C) 2010 Elsevier B.V. All rights reserved.