In situ powder diffraction

Nnhn H, Rossbach J (2000) LINAC-based short wavelength FELs The challenges to be overcome to produce the nltimate X-ray source-the X-ray laser. Synchrot Radial News 13 18-32 OTfare D, Evans ISO, Francis R, Price S, O Brien S (1998a) The use of in situ powder diffraction in the study of intercalation and hydrothermal reaction kinetics. Mater Sci Forum 278 367-378 OHare D, Evans ISO, Francis RJ, Halasyamani PS, Norby P, Hanson J (1998b) Time-resolved, in situ X-ray diffraction studies of the hydrothermal syntheses of microporous materials. Microporous Mesoporous Mat 21 253-262... 

In parallel with the development of powerful X-ray and neutron sources, development of increasingly more efficient detectors has made it possible to obtain very good powder diffraction data in a very short time. The use of position sensitive and area detectors allow a large part of the diffraction pattern to be collected simultaneously. Therefore, non-ambient and in situ powder diffraction studies which were unthinkable a few decades back can now be performed routinely. 

The term in situ powder diffraction is used for many different types of experiments, and there is no strict agreement on the definition. It may be argued that all non-ambient experiments are by definition in situ, as they must be performed at the required conditions, e.g. high temperature or high pressure. 

The early experiments spurred a great interest in using in situ powder diffraetion for many other systems. In situ powder diffraction is still a fast developing research field, which has expanded to increasingly more challenging experiments. 

The main reason for the explosive development in in situ powder diffraction experiments is the development of high intensity synchrotron X-ray sources. The very high intensity allows good time resolution, which makes it possible to follow even very fast reactions. In addition, the accessibility of high energy X-ray radiation has enabled in situ studies in even thick walled steel eontainers, making it possible to study materials under operating conditions. 

Due to the large number of in situ powder diffraction experiments being performed, the following will not attempt to present a comprehensive record of in situ experiments, but will try to focus on important aspects that should be considered when performing in situ powder diffraction experiments. 

Synchrotron X-ray Radiation. Both energy dispersive and angle dispersive diffraction is used for in situ powder diffraction studies using synchrotron X-ray radiation. 

Reactions between solids and gases are common in in situ powder diffraction studies, whether studying catalysts under real or realistic conditions, oxidation/ reduction of solids, adsorption/desorption under controlled conditions or synthesis involving gaseous species. 

R. I. Walton and D. O Hare, Watching solids crystallise using in situ powder diffraction, Chem. Commun., 2000, 2283-2291. 

In situ powder diffraction experiments performed in a wide temperature range of 12 - 1200 K show, that LSGT-8 structure is Rh in the temperature range 12- 303 K, and HT structure remains Or at least up to 1220 K. Refined structural parameters of LT and HT phases of LSGT-8 at 12 K, 303 K and 1203 K are summarized in table 1. 

Final results of the structural refinements of different Cei j Laj A103 and Cei cNd cA103 polymorphs are summarized in Tables 24 and 25. Based on the in situ powder diffraction and DTA/DSC studies, the phase diagrams of the CeA103-LaA103 and CeAlOs-NdAlOs pseudo-binary systems have been constructed (Figure 29 A and B). 

From in situ powder diffraction, DTA/DSC data, and melting temperatures reported in the literature, phase diagrams of the LaGaOs-RGaOs (R = Ce, Pr, Nd, and Sm) pseudo-binary systems have been constructed (Figure 66A-D). 

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