Oxygen ionic conductivity

In the search of high-performance SOFC anode, doped ceria have been evaluated as possible anode materials [9,10]. Comparing Ni-samaria-doped ceria (SDC) with Ni-YSZ, the Ni-SDC anode exhibits higher open-circuit voltages and a lower degree of polarization with either methanol as the fuel, as shown in Fig. 5, or methane as the fuel, as shown in Fig. 6. It was found that the depolarization ability of the anode is associated with the catalytic activity, the electrical conductivity, and the oxygen ionic conductivity of the anode materials [9]. It was also found that the anodic polarization and electro-catalytic activity strongly depend on the Ni content in the anode, and the optimum result for the Ni-SDC anode is achieved with 60... 

FIGURE 1.1 Oxygen ionic conductivity of various solid-state electrolytes. (Data from Kharton, V.V. et al., Solid State Ionics, 174, 135, 2004.)... 

Oxygen Diffusion Coefficient (D ), Oxygen Surface Exchange Coefficient (Ar), and Oxygen Ionic Conductivity (tr,) of LaMn03-Based Oxides Measured by SIMS Technique... 

Over a large range partial pressures of oxygen ionic conductivity dominates and the material behaves as a solid electrolyte. Under these conditions there is an equilibrium established between oxygen ion vacancies, interstitial oxygen ions and lattice oxygen. 

BIMEVOX — Figure. Oxygen ionic conductivity of solid oxide electrolytes at atmospheric oxygen pressure. See Ref. [ii] for details... 

Zhao H and Feng S, Hydrothermal synthesis and oxygen ionic conductivity of co-doped nanocrystalline Cei.xMBio.402 6-x, M=Ca, Sr, Ba, Chem. Mater 11 (1999) pp. 958-964. 

S Atomistic simulation assisted synthesis and investigations The classical atomistic simulation techniques based on the pair potentials are suitable for the simulations of ceria nanoparticles even with a real sized model. Molecular d)mamics studies with several thousands of ions and up to hundreds of nanoseconds in a time scale have been carried out to interpret the diffusion, and crystal growth behaviors for pure and doped-ceria nanoparticles. Traditionally, the technique has been used to explore the oxygen ionic conductivity in ionic conductors such as ceria and zirconia (Maicaneanu et al., 2001 Sayle et al., 2006). 

Thermal and mechanical stability and oxygen ionic conductivity are general requirements for materials that can be used as electrode materials in SOFCs. Increase in stability and reduction of costs require lowering of the operation temperature. However, this prerequisite is accompanied by an increase of electrode polarization, which may be critical for the overall performance (Tsipis and Kharton,... 

Figure 9.4 Total conductivity of stabilized zirconia (a) and doped ceria (b) solid electrolytes [34—40], compared to the oxygen ionic conductivity of pyrochlore-type Cd2Zr2O7 5 [41], (Cd,Ca)2Ti2O7 5 [42], (Cd,Ca)2Sn2O7 s [43], and 241707 a [44].

Figure 9.10 Comparison of the oxygen ionic conductivity of several ferrite-based materials with layered, perovskite and garnet structures [68,133,134], and total conductivity of Ba2ln2O5-based ceramics [125, 127, 129]. Data for Ba2ln2O5 [125] correspond to...

Finally, it should be noted that numerous perovskite-related materials with relatively low oxygen ionic conductivity at 700-1200 K have been excluded from consideration in this brief survey, but may have potential electrochemical applications in fuel cell anodes, current collectors, sensors, and catalytic reactors. Further information on these applications is available elsewhere 1-4, 11, 159, 217-219]. 

Based on the Wagner method [16], the required character of conductivity can be achieved by the introduction of admixture into the basis oxide, which has a common anion with the basis oxide, and the cation has less valence. Type and quantity of the defects are stipulated by the admixture and its concentration. As a rule, the majority of well-known solid electrolytes with pure oxygen-ionic conductivity have a fluorite CaFj crystalUne structure [17]. 

Figure 1.13 shows the low boundary of the oxygen-ionic conductivity region based on Equation (1.44) for the (ZrOjlo.glYjOjlo.i electrolyte. The logarithm of the dissociation pressure for oxide Na20 is also shown for comparison. It is evident from... 

FIGURE 1.13 1 Low boundary of the oxygen-ionic conductivity for the solid (Zr02)o.9(Y203)o 1 electrolyte and 2 and the temperature dependence of logarithm pressure of dissociation for oxide Na20. (From Zhuiykov, S., Electron model of solid oxygen-ionic electrolytes used in gas sensors, Int. J. Applied Ceramic Techn. 3 (2006) 401-411. With permission.)... 

This temperature characterizes the transfer from the mix of electrolyte electroconductivity into the oxygen-ionic conductivity by correlation E/Eq = 0.98. As a result, these experiments concluded that the decrease of percentage of the iron admixture in zirconia from 0.3 to 0.001% allows deaeasing the lower level of threshold temperature Tj from 740 to 560°C. 

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