Yttria-doped ceria

FIGURE 1.30 Conductivity at 500°C for YxCe1.x02.x/2 with various yttria concentrations [118,119,131], 

Solid Oxide Fuel Cells Materials Properties and Performance 

FIGURE 1.31 Variation of activation energy at different yttria concentrations. 

YDC has been prepared by various methods, including solid-state reaction, coprecipitation, glycine-nitrate process and metal organic chemical vapor deposition (MOCVD). Table 1.4 shows that the properties depend on the preparation method [118,119,127,129,130], Zha et al. [129] have studied the influence of sintering 

Selected Data on the Conductivity at 600°C for Y0 2Ce0 8O19 Prepared by Various Methods 

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FIGURE 1.2 Composition dependence of conductivity for yttria-stabilized zirconia (YSZ) measured at 1000°C [7], yttria-doped bismuth oxide (YDB) at 600°C [6], and yttria-doped ceria (YDC) at 700°C [8],... 

Figure 46. Performance characteristics of a cathode-supported thin film Ni—YSZ/YSZ/LSM fuel cell at 600 °C in humidified H2 and air with and without a dense protective yttria-doped ceria (YDC) protection layer introduced between the porous LSM cathode and the thin-film electrolyte. (Reprinted with permission from ref 296. Copyright 1997 Elsevier.)...

In the Monte Carlo method of Murray et al. the long-range Caulombic interaction between charged defects was neglected. By using the same Monte Carlo techniques, Adler et al. tested a model for oxygen transport in yttria-doped ceria that includes... 

Figure 8.4. Experimental (full lines) and calculated (dashed lines) d.c. ionic conductivities at two different temperatures for yttria-doped ceria as a function of the composition (adapted from ref. 59)...

Biswas A, Prabhakaran K, Gokhale NM, Sharma SC (2007) Synthesis of nanociystalline yttria doped ceria powder by urea-formaldehyde polymer gel auto-combustion process. Mater Res Bull 42 609-617... 

Barnett, Perry, and Kaufmann (75) found that fuel cells using 8 im thick yttria-stabiUzed zirconia (YSZ) electrolytes provide low ohmic loss. Furthermore, adding thin porous yttria-doped ceria (YDC) layers on either side of the YSZ yielded much-reduced interfacial resistance at both LSM cathodes and Ni-YSZ anodes. The cells provided higher power densities than previously reported below 700 °C, e g., 300 and 480 mW/cm at 600 and 650 °C, respectively (measured in 97 percent H2 and 3 percent H2O and air), and also provided high power densities at higher temperatures, e g., 760 mW/cm at 750 °C. Other data (Figure 7-25) from the University of Utah (73) show power densities of 1.75 W/cm with H2/air and 2.9 W/cm with H2/O2 at 800 °C for an anode-supported cell. However, no data is presented with regard to electrodes or electrolyte thickness or composition. 

Yttria-doped ceria (Yj.Cei J.O2 J./2) shows a peak ioiuc conductivity for an yttria concentration in the range of x = 10%-15%. The peak conductivity data vary from 0.0025 to 0.0044 at 500°C. 

One approach to overcoming the limitations of nickel anodes, which has met with some success, is to augment the oxidation activity of Ni/YSZ cermets through the addition of an oxide-based oxidation catalyst. For example, stable operation on dry methane has been reported at 650°C in an SOFC using an yttria-doped ceria interlayer between the YSZ electrolyte and the Ni/YSZ cermet anode [61]. Ceria is a well-known oxidation catalyst, and might be expected to increase the activity of the anode for the electrochemical oxidation of methane. This approach still requires, however, that the operating temperature be maintained below 700°C to suppress carbon deposition reactions that take place rai nickel. 

H. Mitsuyasu, Y. Nonaka, K. Eguchi, Analysis on Solid State Reaction at the Interface of Yttria-Doped Ceria/Yttria-Stabilized Zirconia, Solid State Ionics 113-115,279-284 (1998) N. Sakai, H. Kishimoto, K. Yamaji, T. Horita, M.E. Brito, H. Yokokawa, Degradation Behavior at Interface of LSCF Cathodes and Rare Earth Doped Ceria, SOFC X, ECS Transactions, 7(1) 389-398 (2007)... 

Recent studies have also identified some alternative anodes, one being copper-based and incorporating significant quantities of ceria in addition to YSZ [68,114] and the other adding yttria-doped ceria to nickel and YSZ [69], both of which have been reported to show considerable promise for the direct electrocatalytic oxidation of the hydrocarbon fuels, without the need for any co-fed oxidant. However, the conditions under which such anodes can be used for direct hydrocarbon oxidation may be a problem for their widespread application, whilst their long-term performance in terms of deactivation resulting from carbon deposition remains to be investigated. 

The experiments were performed on an anode supported planar Solid Oxide Fuel Cell which consists of a 525—610 pm thick anode with two layers (both made of MO/8YSZ cermet functional layer 5—10 pm thick support layer 520—600 p thick) a 4—6 pm thick dense electrolyte Yo,i6Zro.g402 (8YSZ) a 2—4 pm thick barrier layer made of yttria doped ceria (YDC) the cathode consists of a 20—30 pm thick layer made of porous lanthanum strontium cobalt ferrite oxide... 

F. Iguchi, Y. Endo, T. Ishida, T. Yokobori, H. Yugami, T. Otake, T. Kawada, J. Mizusaki, Oxygen partial pressure dependence of creep on yttria-doped ceria ceramics. Solid State Ionics 176(5-6), 641-644 (2005)... 

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