ELECTRICAL-CONDUCTION IN NB2O5-DOPED CERIUM DIOXIDE

Electrical conductivity of the sintered Nb2O5-doped CeO2 specimens was measured between 800° and 1329°C in the PO2 range 10~19-1 atm. A polarization technique was used to determine the predominant electrical conduction mode in these specimens. Thermogravimetric analysis was done to measure the weight loss in selected specimens. The solid solubility limit of Nb2O5 in CeO2 is between 0.60 and 0.80 m/o, and it does not vary significantly with temperature or po2- The Nb2O5-doped CeO2 is an n-type semiconductor. At high po2, Nb3+ ions are incorporated in CeO2 by both possible charge-compensating mechanisms, viz. (i) reduction of some Ce4+ to Ce3+ and (ii) formation of oxygen interstitials. At low PO2, the first mechanism predominates. Doping with Nb2O5 significantly increases the electrical conductivity of CeO2 in the high po2 range. This extrinsic electronic conductivity, arising from mechanism (i), predominates over the intrinsic conductivity at high po2 (10-4-1 atm) and lower temperatures (800°-1029°C) giving po2-mdependent total conductivity at a constant temperature. At lower po2 or higher temperature, the intrinsic defects of CeO2-x increasingly affect the conductivity. © 1979, The Electrochemical Society, Inc. All rights reserved.