The Debye–Scherrer camera at synchrotron sources: a revisit

In a powder diffraction pattern one measures the intensity of Miller-indexed Bragg peaksversusthe wavevector transfer sinθ/λ. With increasing wavevector transfer the density of occurrence of Bragg peaks increases while their intensity decreases until they vanish into the background level. The lowest possible background level is that due to Compton scattering from the powder. A powder diffraction instrument has been designed and tested that yields this ideal low-background level, obtainable by having the space between sample and detector all in vacuum with the entrance window so far upstream that scattering from it is negligible. To minimize overlap of Bragg peaks the combination of fine collimation of synchrotron radiation, a thin cylindrical sample and a high-resolution imaging plate detector is taken advantage of.

Determination of the Orientation Relations between the Low- and High-Temperature Phases of NiS

In order to get information about the transition mechanism, the temperature-induced transformation in the binary com¬pound NiS was investigated. Above 379 °C, a single crystal of millerite -NiS transforms to polycrystalline NiAs type -NiS with a sharp texture. Pole figures of both phases in the same orientation were measured using synchrotron radiation and an imaging plate detector. The Rietveld texture analysis showed that there are at least three components of the high-temperature -NiS phase. The main component shows the following orientation relations: [001]NiAs type  [001]millerite, [100]NiAs type  [210]millerite, [210]NiAs type  [100]millerite. The broad peaks of the recovered polycrystalline millerite occur at the same positions as the reflections of the original single crystal.

A wide-bandpass multilayer monochromator and its application to the determination of absolute structure

A diffraction system has been constructed at the Synchrotron Radiation Centre at Ritsumeikan University, in which a wide-band parallel X-ray beam is produced by reflection from the depth-graded multilayer monochromator. The band width is 600 eV and the monochromator is useful in the photon energy range from 6500 to 7700 eV. In diffraction patterns of an oscillating single crystal recorded using the beam, Bragg reflections appear in an elongated form on an imaging-plate detector and, if the absorption edge of an atom in the crystal is included in the band, a characteristic intensity profile is seen due to anomalous dispersion. As an application of the system, the absolute configuration was determined for a newly synthesized compound, 4-(1-hydroxyethyl)phenylferrocene, C18H18FeO, with an enantiomorphic structure, choosing the Fe atoms as anomalous scatterers. In the intensity profiles of the Friedel pairs of reflections, clear contrast between the pair was observed at the absorption edge, leading unequivocally to theSform. Further possible application of the wide-bandpass parallel beam is discussed.

A high-temperature furnace for X-ray diffraction with directly machined α-Al2O3ceramic parts

A complex high-temperature furnace has been produced from presintered α-Al2O3precompacts. The furnace is designed for the Mar345 imaging-plate detector system. Up to now, the design complexity of ceramic parts has been limited by the difficulty of machining hard ceramic materials or by the moulds used in hot-pressing and casting. However, the machining of soft presintered ceramic materials enables the realisation of much more demanding designs, provided that the final sintering shrinkage of the ceramic is homogeneous and predictable. The design of the furnace and its realisation and application in an X-ray diffraction study with synchrotron radiation are presented.