Structure Analyses XRD

The X-ray diffraction technique is widely used for routine characterization of solids and applied for determining crystalline phases of the compounds and evaluate possible changes in the crystal structure thereof. 

One can do X-ray diffraction experiments under non-ambient conditions. The X-ray diffractometer can be equipped with a reaction chamber, where the powder sample can be analyzed under the presence of gases, pressure, and/or vacuum. Sometimes, it is also possible to perform reactions. The in situ analyses were initiated with reduction or oxidation processes. The reaction can be carried out in the presence of the reaction mixture. 

Detecting and measuring the size of nanoparticles in supported metal catalysts is of utmost importance for the overall characterization of the system, a factor that is related to the catalytic behavior. Some properties of nanomaterials can be inferred by modeling its cluster structure and size, and a model is used to simulate the scattering of rays by the sample. In general, the parameters involved in the model are optimized until the theoretical pattern fit the experimental results. 

The in situ diffractograms for different reduction temperatures are displayed in Fig. 9.17, showing the collapse of oxide structure and appearance of new phases with increasing reduction temperature. Up to 300 °C, the oxide is resistant to reduction. It is a single-phase LaCoOs perovskite. At 400 °C, perovskite transforms to an intermediate structure brownmillerite La2Co205. This behavior is also reported by Hansteen et al. [11]. At 500 °C, this structure still holds, but collapses before reaching 600 °C, temperature at which cobalt metal is identified with La203 

Temperature Content Unit cell parameters (A) Cell volume  

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