Electronic conductivity of pure ceria

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-CeO2) is about 1/100 of that with 99.9% purity (3N-CeO2) as confirmed by the fluorescence intensity of impurities obtained by Raman spectroscopy. The electronic conductivity for the 5N-CeO2 was measured at T = 973 K to 1173 K, and the results are essentially the same as those for the 3N-CeO2. The electronic conductivity increases with decreasing of P(O2) following slope values of − 1/4 to − 1/6. The − 1/4 dependent region becomes narrower for the 5N-CeO2 than that for the 3N-CeO2. For both types of ceria, the P(O2) 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-CeO2 were 2.2 eV, 2.6 eV and 1.9 eV in P(O2) dependent regions of − 1/6, − 1/4 and 0, respectively.