Defects oxygen vacancy

In conclusion, electron microscopy techniques reveal considerable evidence for variability in composition and defect structures, such as cation and anion vacancies, extended defects, substitutional ions and oxygen interstitials these are common to all of the high temperature superconducting oxides. These defects play an important role in controlling the carrier concentrations and therefore the... 

The defective structure in nanocrystalline ceria based catalysts proved to have strong effect on the OSC. Mamontov et al. (2000) reported the neutron diffraction studies of the atomic structures of nanocrystalline powder of ceria and ceria-zirconia solid solution. They found that the concentration of vacancy-interstitial oxygen defects has a direct correlation with the OSC. This effect is stronger than the correlation of surface area with OSC. Zirconia reduces ceria and preserves oxygen defects to retard the degradation of ceria-zirconia in OSC. Yan et al. observed the strong correlation between OSC and the lattice strain in nanosized ceria-zirconia, which could be measured via XRD (Si et al., 2004 Figure 11). 

Figure 10.6. TempcTature dependence of oxygen defect concentrations upon heating. Filled circles are oxygen interstitials, and open circles arc oxygen vacancies. The lower set of data points at 20°C were obtained upon completion of the thermal cycle. [ 13]...

The total introduction rates of radiation-induced defects (t]) drop upon increase of the irradiation temperature in the range of 730-780 K. In these temperature range the vacancy-oxygen complexes, which were the dominant radiation-induced defects after irradiations at lower temperatures, are not thermally stable. 

Figure 4 shows the present theoretical spectra and the experimental spectra (25). In the theoretical spectrum for the vacancy-containing cluster, the peaks A-C appear as well as for Ce02- The peak A becomes blurred because the resonances among the oxygen atoms are weakened due to the oxygen defect. The part for the peak A was not reported for the experimental spectrum. 

Oxygen transport in the perovskites is generally considered to occur via a vacancy transport mechanism. On the assumption that the oxygen vacancies are fully ionized and all contribute to transport, i.e., oxygen defects are not associated, the Nernst-Einstein equation reads,... 

For a substituted perovskite-type material with oxygen vacancy-type defect structure, the overall formula can be written as Aj A Bi where A, A denotes... 

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