Perovskites cobalt-based

The change of spin state of Co3+ ions with changing temperature or pressure is an intriguing feature of cobalt-based perovskite compounds represented mainly by LaCo03. Due to the closeness of the crystal field... 

A final point to note from this table is that the properties of the materials vary tremendously from one cation to another. A cobalt-based perovskite could have an oxygen diffusivity as much as 10 orders of magnitude higher than a chromium-based perovskite which contains the same A-site elements, but the thermal expansion coefficient could be more than double that of the chromate. 

From XPS analyses, the coexistence of Mn and Mn species was evidenced in LaMnOs material, while the LaCoOs one showed the presence of Co and Co " at the same time. Additionally, these authors established a higher Oads/Oiatt molar ratio on LaCoOs perovskite than that observed for the LaMnOs one. This phenomenon, observed at the surface of the material, improved the low-temperature reducibility of LaCoOs material, where the catalyst s properties claimed to be responsible for the remarkable catalytic performance of the cobalt-based perovskite in the CO oxidation reaction. Other authors have also remarked the importance of the presence of Co " species as active sites for the adsorption of CO [37-39]. For instance, by using DRIFT spectroscopy, Natile et al. [37]... 

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-... 

Oxygen Tracer Diffusion Coefficient (D ), Oxygen Surface Exchange Coefficient (Ar) and Oxygen Ionic Conductivity (a, in air) of Doped Lanthanum Cobalt Ferrite-Based Perovskites... 

Similarly to the case of direct-oxidation anode materials, sulfur-tolerant anode materials based on sulfides [6, 7] or double-perovskite oxides have special requirements for their processing into SOFC layers. For example, nickel sulfide-promoted molybdenum sulfide is tolerant to high sulfur levels [7], However, it has a low melting temperature [6] that has resulted in the development of cobalt sulfide as a stabilizer of the molybdenum sulfide catalyst [6], CoS-MoS2 admixed with Ag has an even higher performance in H2S-containing fuels than in pure H2 [6]. However, processing methods such as PS, infiltration, or sol-gel techniques that can process... 

A series of perovskites were prepared but care must be taken in preparing these perovskites as it has been shown that composition and structure of these perovskites are highly dependent on the preparation route and the presence/concentration of dopants is critical. If all the perovskites studied here have a defective structure, then it is believed that the Co based perovskites with minor phases such as ceria, lanthana and cobalt oxide offer the most promise for catalytic application. PXRD analysis shows the presence of... 

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. 

Materials of interest are negatively (typically Sr) doped perovskites based on lanthanum manganate, cobaltate, or ferrate. Recently Bao.sSrosCoogFeo Os has been proposed as a very promising composition. Here we will largely focus on the standard material LSM (Sr-doped LaMnOg). 

By examining the solubility of the different salts of barium, lanthanum and cobalt it appeared at for the three, the nitrate salts are very soluble as opposed to the carbonate salts which are insoluble in water. For tungsten, no salt was found to be very soluble in water, or any inorganic base except ammonia. However cobalt is known to form a large number of ammoniacal complexes, thus this base caimot be used therefore no co-precipitation pathway was found to prepare tungsten containing perovskites. 

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