Interstitial oxide

Hydrides are ionic (or interstitial) Oxides are ionic and basic... 

Growth of oxidation-induced stacking faults proceeds by the absorption of the generated self-interstitials. Oxidation-enhanced diffusion can occur as a result of the presence of the excess interstitials via the Watkins (36) replacement mechanism or by an interstitialcy process. 

An n-type cation interstitial oxide grows through interstitial cations diffusion to the oxide-gas interface (Fig. 11.8). The electrons travel to the same interface where the overall reaction, Eq. (11.3), occurs. The metal oxidation and oxide formation, Eq. (11.1), and oxygen reduction, Eq. (11.2), are shown in Fig. 11.8. 

It is well-established that p-alumina prepared by the usual ceramic methods contains an excess of Na ions over its ideal composition, and that the formula is expressed by Nai+,jAlnOi7+,c/2 (x =5 0.3). The parameter, x/2, represents the number of interstitial oxide ions, 0 at mO sites - a middle point between two 0(5) oxygens, Fig. 13.1 - per unit cell plane each Oj coordinates to two Frenkel defects i.e. two interstitial AljS which are associated with A1 vacancies at the adjacent Al(l) site . The situation in K p-gallate is identical to that of P-alumina. Local electroneutrality is not guaranteed in the ideal structure, since there is a... 

Le6n-Reina L, Porras-Vazquez J M, Losilla E R and Aranda MAG (2006), Interstitial oxide positions in oxygen-excess oxy-apatites . Solid State Ionics, 177,1307-1315. 

As described above, the variation in oxygen nonstoichiometry of oxide is followed by the formation of defects in the oxide. The oxide-ion vacancies may be accompanied by the oxygen deficient type nonstoichiometry. The interstitial oxide ions or the cation vacancies... 

When the concentrations of ionic defects such as oxide ion vacancies, interstitial oxide-ions or cation vacancies increase, the oxide-ion conductivity or the cation conductivity increases. When the concentrations of electronic defects such as electrons or holes both either localized or itinerant increase, electronic conductivity may increase. 

While this information on the crystal chemistry is of importance in determining the potential for new materials, it is the latest advances in data processing and interpretation that enable both structural and chemical information to be extracted from one data set. The advent of the Maximum Entropy Method (MEM) [63] for analysis of neutron-diffraction data has enabled authors to extract chemicalpathway data from the neutron density. Yashima et al. [64, 65] used the MEM technique to visualize the diffusion pathway of the oxide ions in an anisotropic Pr2Ni04+5-based interstitial oxide ion conductor. The data obtained. Fig. 19.9, at... 

Rare earth oxy-apatites are also attracting considerable interest as a new type of solid electrolytes possessing a high oxide-ion conductivity at intermediate temperatures [22-35]. In contrast to traditional fluorite- and perovskite-type oxide electrolytes conducting via oxide ion vacancies, the high ion conductivity of the apatites is provided by the transport of interstitial oxide ions [29-34], This is caused by peculiarities of the apatite structure that tolerates different structural defects such as cation vacancies and oxygen interstitial sites. 

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