Perovskites effective charge

We have seen that in es.sentially all transition-metal compounds, a possible starting point for a calculation of the electronic structure is an ionic description. In the perovskites, however, it may be determined from Table 19-3 that perturbation theory runs into trouble. We may, for example, calculate the effective charge Z on oxygen, starting with a closed shell 0 . The perturbation of each oxygen pa... 

Depth profiles of matrix elements on Mn- and Co-perovskite layers of fuel cathodes have been measured by LA-ICP-MS in comparison to other well established surface analytical techniques (e.g., SEM-EDX).118 On perovskite layers at a spatial resolution of 100p.m a depth resolution of 100-200 nm was obtained by LA-ICP-MS. The advantages of LA-ICP-MS in comparison to other surface analytical techniques (such as XPS, AES, SIMS, SNMS, GD-OES, GDMS and SEM-EDX) are the speed, flexibility and relatively low detection limits with an easy calibration procedure. In addition, thick oxide layers can be analyzed directly and no charging effects are observed in the analysis of non-conducting thick layers. 

Donor dopants, i.e. those of higher charge than that of the ions they replace, are compensated by cation vacancies acceptors, i.e. dopants of lower charge than that of the replaced ions, are compensated by oxygen vacancies. Each dopant type tends to suppress the vacancy type that the other promotes. The common dopants in perovskite-type ceramics are listed in Table 6.1. The effects of aliovalent substituents are discussed in Section 2.6.2. 

The first electrochemical reduction of LCO was studied by chronoamperometry [283]. This method serves as an effective instrument for studying the phase composition and oxide properties [84], The cathodic current maximum was attributed [283] to the process of lattice reconstruction in the near-surface cuprate layers in the course of de-doping (the process similar to nucleation). Of prime interest for the development of LCO electrochemistry is the more efficient measurement of equilibrium charging curves. Experience of equilibrium measurements on perovskite... 

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