Ionic oxides

In insulating oxides, ionic defects arise from the presence of impurities of different valence from the host cation. An aluminum ion impurity substituting in a magnesium oxide [1309-48-4] MgO, hostlattice creates Mg vacancies. 

During the last 5 years, Inabe and co-workers [73-76] have used electrochemical oxidation to synthesize a series of partially oxidized ionic Pc compounds [PXX]n[MmPc(CN)2] (M = Fe or Co) (87-90) and [TPP][ComPc(X)2]2 (X = 0(91) or Br(92)) with two trans CN groups, Cl- or Br ions. The central metal ions all have distorted hexacoordinated octahedral geometries. The Pc skeletons in these complexes are nearly strictly planar and the central metal ions lie in the (Niso)4 planes. The M-C=N angles are almost linear and the axial CN groups, Cl- or Br ions are relatively small. Therefore, these Pc complexes always form ID columnlike or 2D sheet-like Pc stacks via various Pc n-n interactions. In addition, the planar... 

Different from the critical radius, Mori et al. [89] proposed a concept of effective crystallographic index to maximize the oxide ionic conductivity of doped ceria. The index, I, is defined as... 

Ionic models for g tensor, 32 11-14 Ionic oxides, see specific oxides Ionic promoters in ruthenium catalysis, 32 387-406... 

In addition to being able to catalyze the dissociation of O2. the material used for the cathode must be electronically conductive in the presence of air at high temperature, a property found primarily in noble metals and electronically conductive oxides. Ionic conductivity is also desirable for extending the reaction zone well into the electrode since the ions must ultimately be transferred to the electrolyte. Since precious metals are prohibitively expensive when used in quantities sufficient for providing electronic conductivity, essentially all SOFC prototypes use perovskite-based cathodes, with the most common material being a Sr-doped LaMnOs (LSM). In most cases, the cathode is a composite of the electronically conductive ceramic and an ionically conductive oxide, often the same material used in the electrolyte. 

Nickel oxides and hydroxides play an important role in the passivity of nickel in aqueous solutions, in oxidizing ionic... 

Ishihara, T., Matsuda, H. and Takita, Y., Doped LaGaC>3 Perovskite type oxide as a new oxide ionic conductor, Journal of the American Chemical Society 116, 1994, 3801. 

Organoboron compound, geminal, 219 Organodiboron derivatives, 193 Organodielement halides, 79-83 Organoelement halides, 99 Os-Cl exchange, 186 Osmium boryl complexes, 179 Oxidation, ionic liquids, 278-279... 

Another aspect to consider is the presence or absence of oxygen in solution. The effect of its presence in acidic solution is demonstrated in Fig. 16.5, the result being greater corrosion. Sometimes it catalyses corrosion by oxidizing ionic species in solution, for example... 

Iwahara, H., Oxide-ionic and protonic conductors based on perovskite-type oxides and their possible applications. Solid State Ionics, 52, 99-104 (1992). 

The color of doped samples changes from green to black during the adsorption of oxygen (about 2 cm /gm at po, = 2 torr, see Table XI) at room temperature. There is simultaneously an increase of the electrical conductivity of the oxides [from 6.2 x lO- to 1.8 x 10- ohm-i cm" in the case of NiO(10 Li)(250°)]. Outgassing at room temperature produces the desorption of a small quantity of oxygen ( 0.2 cm /gm) but does not modify the electrical conductivity of the oxides. Ionic species are thus irreversibly adsorbed and because of the similarity of the adsorption processes on doped oxides and on pure NiO(200°) or NiO(260°), we admit that again 0 (ads) ions are formed on doped oxides. 

Several methods exist for the identification and quantification of the HO and H02 radicals generated by the sonolysis of water. These species can oxidize ionic moieties e.g. Fe2+ into Fe3+ (the Fricke dosimeter) and I- into iodine. In addition, either can dimerize to form hydrogen peroxide (Schemes 2 and 3), which can then be titrated using conventional techniques. The HO will also react with terephtha-late anion in aqueous solution to produce hydroxyterephthalate anion, a fluorescent material which can then be estimated using fluorimetry. 

We have studied the partial oxidation of hydrocarbons with electrochemical reactor using an oxide ionic conductor, e.g. YSZ, SDC, etc. [2-4, 10]. In these studies, it was found that a ceria-based solid electrolyte is useful for the propene oxidation to acrylaldehyde at relatively low temperature of 350°C [10]. In this case, however, the acrylaldehyde selectivity was lower than that obtained with the electrochemical reactor constructed from YSZ. This may be due to the high activity of ceria surface for the complete oxidation of hydrocarbons [13,14]. 

As heterogeneous equilibria in solid oxide-ionic solvent systems are the most investigated in molten chlorides, the general acid-base scale for such melts may be constructed using the solubility method. 

Equilibria in Solid Oxide-Ionic Melt Systems... 

Equilibria in solid oxide-ionic melt systems... 

The sequential addition method (SAM) recently developed in our studies makes it possible to estimate the solubility of oxides having different values of specific (molar) surface and, probably, of surface energy at the oxide—ionic melt interface boundary [333]. 

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