Single-base metal oxides

The central topic of the book was the integration of microhotplate-based metal-oxide gas sensors with the associated circuitry to arrive at single-chip systems. Innovative microhotplate designs, dedicated post-CMOS micromachining steps, and novel system architectures have been developed to reach this goal. The book includes a multitude of building blocks for an application-specific sensor system design based on a modular approach. 

Inorganic Metal oxide materials Base single or mixed metal oxides Deposition method and conditions of base metal oxide(s) Annealing method and conditions Dopant(s) Doping method and conditions Purity of materials... 

There are considerable data in the literature on the activities of both single component base metal oxides and mixed oxides (1-22). Some of these data are summarized in Tables I, II, and III and in Figure 1. 

Watanabe, N. and Ueda, W. (2006). Comparative Study on the Catalytic Performance of Single-Phase Mo-V-O-Based Metal Oxide Catalysts in Propane Ammoxidation to Acrylonitrile, Ind. Eng. Chem. Res., 45, pp. 607-614. 

Stabilization of Ru based oxides by valve metal oxides has not been studied in such detail using photoelectron spectroscopy. The most common compositions, however, with relatively high valve metal content, are not in favor of formation of a solid solution. Studies of the phase formation in Ru/Ti mixed oxides has shown [49] that homogeneous solutions are formed for compositions with Ru < 2% or Ru > 98% (see Section 3.1.1). Therefore electrodes with other compositions are better described as physical mixtures and the electrochemical behaviour is most likely that of a linear superposition of the single components. It has to be considered, however, that the investigations performed by Triggs [49] concern thermodynamic equilibrium conditions. If, by means of the preparation procedure, thermodynamic equilibrium is... 

One other caveat concerning the approach used here must be made. This discussion, and the studies to which it relates, are based on some version of the Stern model for the oxide-electrolyte interface. Oxide surfaces are rough and heterogeneous. Even for the mercury-electrolyte interface, or single crystal metal-electrolyte interfaces, the success of some form of the Stern model has been less than satisfactory. It is important to bear in mind the operational nature of these models and not to attach too much significance to the physical picture of the planar interface. 

Several methods are employed for the purification of the single platinum metal salts, for instance re-crystallization of Na2[Pt(Cl)6] with oxidative hydrolysis of the impurities of Pd, Rh, Ir, etc. which together with base-heavy metals are removed as insoluble hydroxides. Generally the metals are obtained, initially as sponge or powder, by conversion of their salts through thermal decomposition or by reduction of aqueous solutions of the ammonium-chloro complexes. Os which has been oxidized to the volatile 0s04 and Ru have to be reduced by H2. 

M. Graf, D. Barrettino, P. Kaser, J. Cerdk, A. Hierlemann, and H. Baltes, Smart single-chip CMOS microhotplate array for metal-oxide-based gas sensors Proc. IEEE Transducers 03, Boston, MA, USA (2003), 123-126. 

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