Transmission diffractometers - PowerPoint PPT Presentation

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Transmission diffractometers

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  1. Transmission diffractometers Debye-Scherrer setup – George/Ringo Press any button for next slide Press any button Kα1 Advantages Kα,β - characteristic radiation deceleration radiation • Best setup for accurate positions and intensities Kα2 Goniometer circle Kβ1 Tube spectrum Divergence slit Primary Monochromator Wavelength Cu X-ray tube Capillary with powder Detector Disadvantages 2θ Incident/Monochromated spectrum • Low intensity • Absorption correction • required • Challenging sample preparation – highly absorbing powders require filling 0.1 – 0.2 mm capillaries Kα1 Kα1 Diffracted spectrum Same as incident, unless sample contains fluorescing elements, e.g.Mn Fe, in which case Wavelength Wavelength

  2. Transmission diffractometers Flat sample setup – Paul Press any button Kα1 Advantages Kα,β - characteristic radiation deceleration radiation • Higher intensity • than in Debye- • Scherrer setup Kα2 Goniometer circle Kβ1 Tube spectrum Divergence slit Primary Monochromator Wavelength Cu X-ray tube Sample container is rotated around the centre of the goniometer circle, in sync with the detector. θ Powder on foil Detector Disadvantages 2θ Incident/Monochromated spectrum • Absorption correction • required • Unbiased peak positions and intensities obtained ONLY IF the centre of the goniometer circle lies on the mid - thickness plane of the sample Kα1 Kα1 Diffracted spectrum Same as incident, unless sample contains fluorescing elements, e.g.Mn Fe, in which case Wavelength Wavelength