Perovskite iron-based

An example of a complex material used in syngas applications is Lag jSro gFeo g. Coo.iCro.203 [26]. This composition contains many of the features previously discussed. It is predominately an iron-based perovskite, providing both electronic and ionic conductivity. In order to improve the chemical stability and resistance to chemical expansion, the B-site is doped with chromium. A small amount of cobalt is added in order to improve the electronic conductivity, and cobalt wiU also increase the ionic conductivity slightly. Strontium is used as the A-site dopant in order to avoid the problems associated with calcium, and particularly with barium, in regard to reaction with CO2. In addition, the material has been made substantially A-site deficient to improve its stability. 

The catalytic data also indicated a strong dependence of the low hydrocarbons conversion on the catalyst elemental composition. For the Lai, s Fe03 g perovskites, a progressive Fe20s enrichment of the surface was evidenced by XPS characterization when decreasing the lanthanum content of the solid. Such additional undesirable surface iron oxide enrichment induced an inhibiting effect on the catalytic activity. As a result, the most efficient lanthanum iron-based perov-sldte was the stoichiometric LaFe03 mixed oxide [40]. 

Li, H., Zhu, X., Liu, Y., Wang, W., and Yang, W. (2014) Comparative investigation of dual-phase membranes containing cobalt and iron-based mixed conducting perovskite for oxygen permeation. /. Membr. ScL, 462,... 

The relatively high cost and lack of domestic supply of noble metals has spurred considerable efforts toward the development of nonnoble metal catalysts for automobile exhaust control. A very large number of base metal oxides and mixtures of oxides have been considered, especially the transition metals, such as copper, chromium, nickel, manganese, cobalt vanadium, and iron. Particularly prominent are the copper chromites, which are mixtures of the oxides of copper and chromium, with various promoters added. These materials are active in the oxidation of CO and hydrocarbons, as well as in the reduction of NO in the presence of CO (55-59). Rare earth oxides, such as lanthanum cobaltate and lanthanum lead manganite with Perovskite structure, have been investigated for CO oxidation, but have not been tested and shown to be sufficiently active under realistic and demanding conditions (60-63). Hopcalities are out-... 

A continuous process based on hydrodynamic cavitation can be employed to prepare a wide variety of metal oxides in grain sizes of 1 -10 nm, such as iron oxide, bismuth molybdate, perovskites, platinum-loaded zeolite, and other ceramics and superconductors [170]. The method uses a microfluidiser for mechanically generating hydrodynamic cavitation and the internal pressure of the liquid media is elevated from ambient pressure to between 1000 to 25 000 psi. 

The orthoferrites, RFeOa, where R is yttrium or a rare-earth element have a structure based on a distorted perovskite lattice with only one iron environment. Most of them possess weak ferrimagnetic character as a result of spin canting from the ideal two-sublattice antiferromagnetic ordering. 

Since part of the interpretations for the intermediate Fe in perovskite and postperovskite is based on the XES analyses for the total spin momentum of the 3d electronics in the samples, further understanding of the XES spectra involving multiple electronic transitions as well as theoretical calculations incorporating lattice distortion effects is needed to resolve the discrepancy between current experimental and theoretical results and interpretations. Although SMS spectra can now be collected from the laser-heated DAC experiments at relevant P-T conditions of the lower mantle, extended time windows are needed to extract more meaningful information to decipher the spin and valence states of iron in the lower-mantle minerals at relevant P-T conditions. Knowing the exact spin and valence states of iron in the lower-mantle minerals would then help geophysicists to address properties of the deep Earth. 

The role of support on the performance of noble metals-based catalysts for the total oxidation of aromatic hydrocarbons is essential [38]. Although with a smaller surface area than the typical supports, perovskites also demonstrate good properties as carriers for noble metals. Thus, perovskites of type LaBOs (B = Co, Mn, Fe, Ni) synthesized using the citrate route were used as support for noble metals in total oxidation of toluene [39]. The performances of these catalysts varied in the order Fe>Mn>Co>Ni, and the superior behavior of iron was attributed to the low temperature of calcination and the high stability of the perovskite lattice irrespective of the nature of the stream it was exposed to. The dispersion of palladium at the different stages of the process remained unchanged. 

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