Faculty of Science - Leading creativity and innovation in the sciences


X-Ray Centre


Siemens/Bruker SMART APEX II Single Crystal Diffractometer


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X-ray Diffraction is a non-destructive analytical technique which provides detailed information about the internal lattice of crystalline substances, including unit cell dimensions, bond-lengths, bond-angles, and details of site-ordering. Directly related is single-crystal refinement, where the data generated from the X-ray analysis is interpreted and refined to obtain the crystal structure. 

Our service includes

  • Single-crystal X-ray diffraction is most commonly used for precise determination of a unit cell, including cell dimensions and positions of atoms within the lattice. Bond-lengths and angles are directly related to the atomic positions.
  • Data collection and structure determination.

Samples, instrumentation and data collection

The samples should be optically clear single crystals. Their size should be between 0.1 and 0.3(max 0.48) millimeters in the three directions of space. They are normally selected using an optical microscope equipped with a polarizing attachment (Leica M125, magnification up to 100x). A selected crystal is fixed on the tip of a thin glass fibre using epoxy or cement, or in a loop including specific oil, which fits into the goniometer head in the diffractometer. The crystal is then aligned along the beam direction. It is necessary to know the stability properties of the crystals. Crystals can be sensitive to light, air or moisture, or susceptible to loss of crystallization solvent. If so, a special treatment is required. For example, the data collection can be performed at low temperature 100 K.

Once the crystal is mounted on the diffractometer, the intensity data is collected. Data is typically obtained between 3 º and 30 º2θ when using molybdenum radiation. Generally, a complete data collection may require between 6 to 24 hours, depending on the symmetry and size of the crystals. Some of the measured intensities enable the calculation of the unit cell parameters. Then all the intensities are indexed and a list of observed hkl reflections is obtained.

 

Limitations of Single Crystal X-Ray Diffraction.

  • Must have a single, robust (stable) sample, generally between 0.1-0.5 millimetres in size.
  • Optically clear sample.
  • Twinned samples can be handled with difficulty.
  • Data collection generally requires between 6 and 24+ hours.

 

PANalytical Empyrean X-ray Diffractometer


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The PANalytical Empyrean X-ray diffractometer (XRD) is a multipurpose instrument that can be used for phase identification of powders, structural analysis and the analysis of geological minerals.

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Radiation /wavelength: Cu K-alpha, 1.5418 Å

Measurement in reflection (bragg-brentano geometry, theta-theta geometry) and transmission (debye-scherrer geometry with preFIX-focusing X-Ray mirror) at temperatures 25-1000 °C.

  • Programmable spinner for reflection/transmission stage.
  • Sample changer for 45 samples (in Bragg-Brentano geometry), PreFIX-PDS (programmable divergence slit) and PreFIX-PASS (programmable anti-scatter slit).
  • PIXcel1D-detector and graphite monochromator.
  • Theta/theta goniometer with R=240 mm, smallest step width 0.0001°.
  • Capillary spinner for small volume samples.
  • High temperature reaction chamber for measurement up to 1000 °C (Anton Paar XRK 900) in aggressive atmospheres, and by pressure up to 1 bar. 

Applications:

  • Powder and polycrystalline bulk materials; limited applicability to soft matter samples.
  • Phase analysis, composition quantification, crystallographic structure determination.
  • Crystallite / grain size and strain analysis.
  • Texture (preferred orientation) analysis. 
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PANalytical Axios 1kW X-ray Fluorescence Spectrometer


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The PANalytical Axios is a 1kW wavelength dispersive X-ray fluorescence (XRF) spectrometer equipped with an argon flow counter and solid state scintillation counter. This system uses PANalytical's Axios high resolution, wavelenth dispersive, X-ray fluorescence (WDXRF) spectrometer for elemental analysis.

Our Service includes

  • Preparation and elemental analysis of fused glass discs.
  • Preparation and elemental analysis of pressed powders, liquid samples and thin films (in the future).
  • Element search and quantification.
  • Automated sample disc fusion and programmable fusion settings to optimise the preparation of the sample discs.
  • XRF instrument operates in continuous measurement mode reducing sample turnaround times.

Limitations of XRF

  • Quantification of certain low mass and trace elements are not possible due to the limits of the instrument.
  • Samples must be dried powders and require a minimum of 4g mass before ignition.
  • Samples must be  safe to handle with bare hands.
  • Certain materials with high concentrations of certain elements may be unsuitable samples for this instrument, please see a technician to assess suitability.
  • Data collection generally requires between 1.5+ hours per sample.
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Our people


Dr Ilyas Qasim is the X-Ray Technical officer and is the point of contact for use of the X-Ray Centre, he is located in the School of Chemical Sciences.  

People associated with the centre

  • Powder and single crystal XRD: Dr Tilo Sohnel is an Associate Professor in Chemistry at the School of Chemical Sciences.
  • XRF: Dr Michael Rowe is a Senior Lecturer in Geology at the School of Environment.
  • Single crystal XRD: Ms Tania Groutso is a Senior Research Technician at the School of Chemical Sciences.

See, Selected Publications