Of nonstoichiometric oxides

The previous sections imply that in the case of nonstoichiometric oxides that favor electronic compensation of composition change a relationship exists between the variation in partial pressure and the electronic conductivity. The form that this relationship takes depends upon the way in which the oxide accommodates composition variation. 

In conclusion I should like to consider a few of the chemical investigations which might be accomplished in the rare earth field by Mossbauer spectroscopy. The study of nonstoichiometric oxides has been discussed earlier, but there is the problem of finding an appropriate doping nuclide for the praseodymium oxide system. The element most capable of following the changes in oxidation state of the praseodymium is terbium-159, which does have a Mossbauer state, however, with a rather broad resonance (58,0 k.e.v., = 0.13 nsec.). Nevertheless, with a sufiiciently... 

In the work an electronic structure of nanoparticles of nonstoichiometric oxide WO, was investigated by XPS-method at room and work temperatures. Hydrogen sensor based on these nanoparticles showed a good sensitivity at room temperature. 

Like molybdenum and tungsten, vanadium forms a variety of nonstoichiometric oxides with the alkali metals and other cations, for example, Cu+, Ag+, Zn+, or Al+, which have bronze-like properties. " These compounds can be made by heating appropriate mixtures of V2O5 and the desired alkali metal carbonate or oxide in platinum vessels under argon at 700-800 °C and then cooling slowly over... 

How can we assess the thermochemical data presented in Table 1 Many were obtained by static-bomb calorimetry. Regrettably, this technique is clearly unsuitable to deal with these substances due to the ill-defined composition of the combustion products (see the discussion in References 13 and 28). The formation of nonstoichiometric oxides upon combustion all but precludes the experimental rigor demanded of the combustion calorimetrist. This fact, by itself, allows us to question the reliability of the values shown for all of the trialkyl compounds and for triphenylantimony. Although the results for triphenylbismuth found by static and rotating-bomb calorimetry overlap within their error bars, this has been suggested to be fortuitous ... 

The starting point for understanding the behavior of nonstoichiometric oxides involves constructing their Kroger-Vink diagram, as discussed in Sec. 6.2.5. To illustrate, consider the following examples ... 

The dilfusivity will also depend on the chemical environment surrounding a crystal. This is especially true of nonstoichiometric oxides in which the stoichiometry and consequently the concentration of the defects are a relatively strong function of the oxygen partial pressure. In these instances, the partial pressure dependence of the dilfusivity is the same as that of the defects responsible for the dilfusivity. 

Sorensen, O.T., 1981, Thermodymamics and defect structure of nonstoichiometric oxides, in Nonsto-ichiometric Oxides, ed. O.T. Sorensen (Academic Press, New York) pp. 1-59. 

The Ag I Ag20 electrode was not frequently used. Earlier works on the Ag Ag20 electrode were discussed by Hamer and Craig [178] and briefly summarized by Ives and Janz [177]. Evidently the potential of such electrodes, as found in earlier works, was not quite stable and its drift to more negative values was observed in time. Hamer and Craig [178] explained these changes as due to not proper preparation of the electrode. Namely the Pt with deposited porous silver was dipped in a slurry of silver oxide before use. Instability could result from the oxygen adsorption on silver and the formation of a film of nonstoichiometric oxides on the surface. 

Tretiakov YD (1974) Chemistry of nonstoichiometric oxides. Moscow University Publications, Moscow... 

The electrosynthesis, in aqueous solution, of nonstoichiometrically oxidized, highly conducting complexes of platinum has been described,28/27 Eqs. 7.1 and 7.2 ... 

K. Sato, K. Yashiro, T. JCawada, H. Yugami, T. Hashida, J. Mizusaki, Fracture process of nonstoichiometric oxide based solid oxide fuel cell under oxidizing/reducing gradient conditions. J. Power Sources 195(17), 5481-5486 (2010)... 

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