Ceria Electrolyte

Pure stoichiometric ceria is not a good oxygen ion conductor. The oxygen ion conductivity can be introduced dramatically by low valance doping. Thus the conductivity depends on the characteristics of the dopant elements and their concentrations. 

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FIGURE 1.34 Comparison in open-circuit voltage of a unit cell with gadolinia-doped ceria electrolyte containing 3 mol% of Ln(Y, Sm, Nd, Pr, and La) codopant [134]. 

Most of the literature focuses on the aspects of sinterability and microstructure, but limited data on the electrical properties is available. Tok [152] reported a conductivity of 18.3 x 10-3 Scm-1 at 600°C for Gd0 jCeo.gOj 95, and we measured a high conductivity of 22 x 10-3 scm-1 for Sm0 2Cc08O 9 at the same temperature. Their activation energies are relatively low—less than 0.7 eV. Although conductivity data reported for doped ceria prepared with carbonate precipitation is varied from different authors [153-155], the conductivity is generally high and the activation energy is usually low for ceria electrolytes fabricated with this method. 

The open-circuit voltages (V0c) of SOFCs with doped-ceria electrolytes are relatively low. SOFC can be considered an oxygen concentration cell. The open-circuit... 

Maximum Power Output (WM) and Open-Circuit Voltage (Voc) for SOFCs with Doped-Ceria Electrolytes... 

Performance of Single-Chamber SOFCs with Doped-Ceria Electrolytes... 

Bao 5Sr0 5Co08Fe0 2O3 (BSCF) shows extremely high electrochemical activity for the 02 reduction reaction at intermediate temperatures. Shao and Flaile [105] applied BSCF as cathode to a doped ceria electrolyte cell and achieved the power densities of... 

To introduce a barrier layer when utilizing doped ceria electrolytes (SDC, GDC, or lanthanum-doped ceria, LDC) to prevent the reduction of Ce4+ to Ce3+. Reduction of cerium cations results in unwanted electronic conductivity that lowers fuel efficiency [34], and mechanical degradation that results from the volume expansion of cerium ions upon reduction [35],... 

Xu X, Xia C, Xiao G, and Peng D. Fabrication and performance of functionally graded cathodes for IT-SOFCs based on doped ceria electrolytes. Solid State Ionics 2005 176 1513-1520. 

Ralph JM, Kilner JA, and Steele BCH. Improving Gd-doped ceria electrolytes for low temperature solid oxide fuel cells. Mater. Res. Soc. Symp. Proc. 1999 575 309-314. 

Xu X, Jiang Z, Fan X, and Xia C. LSM-SDC electrodes fabricated with an ion-impregnating process for SOFCs with doped ceria electrolytes. Solid State Ionics 2006 177 2113-2117. 

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