Electronic Conductivity of La‐Doped Ceria Ceramics

Abstract

Lanthanum‐doped ceria powder with a composition Ce0.8La0.2O1.9 was prepared by heating the oxalate solid solution (Ce0.8La0.2)2(C2O4)3 at 873 K in air. As‐prepared powder was densified to 96%–97% relative density by sintering in air at 1773 K for 4 h. The electronic current of the disk sample was measured in a temperature range from 773 to 1113 K by the direct current polarization method using a Hebb–Wagner ion‐blocking cell. A linear relationship, which was theoretically predicted, was measured between log σe (electronic conductivity) and E (applied voltage) in the applied voltage range of 0.2–1.0 V. The σe was proportional to PO2−1/4.3≈PO2−1/4.6 in the oxygen partial pressure range of 10−2–10−8 Pa, and to PO2−1/6.7≈PO2−1/7.1 in the oxygen partial pressure range of 10−7.5–10−22 Pa. The apparent activation energy of the electronic conduction was 1.87–1.94 eV. The hole conduction was also measured in the Po2 range of 102–105 Pa. The transport number of oxide ion was 0.96–1.00 at 773–1113 K under an oxygen partial pressure of 10−5 Pa.