Advantages of synchrotron radiation for polycrystalline diffractometry

Methods developed at the Stanford Synchrotron Radiation Laboratory for obtaining high quality polycrystalline diffraction patterns are described. Any wavelength from about 0.5 to 2 A can be selected from the high intensity parallel beam source. The X-ray optics includes an incident beam silicon (111) channel monochromator and long parallel slits with 0.05º aperture to define the diffracted beams. Patterns with a selected wavelength are recorded with θ:2θ scanning or with fixed specimen and 2θ detector scanning; the wavelength can be chosen at will. The high resolution single profiles have the same shape in the entire pattern except for the width which increases with tanθ. They are fitted with a pseudo Voigt function (75% G 4-25 %L) to resolve overlaps and derive integrated intensities. High resolution energy dispersive diffraction patterns are made with the same instrumentation and a scintillation counter by step scanning the monochromator. A number of methods and new applications that have been developed are briefly described. © 1987, by R. Oldenbourg Verlag