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Olympus XRD sample cell spacer choice


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More information on Olympus XRF and XRD solutions:

In this presentation learn how our TERRA and BTX II sample cells are used along with their analytical benefits.

Our X-ray Fluorescence (XRF) and X-ray Diffraction (XRD) Analyzers provide qualitative and quantitative material characterization for detection, identification, analysis, quality control, process control, regulatory compliance, and screening, for metals and alloys, mining and geology, scrap and recycling, environmental and consumer safety, education and research, and general manufacturing.

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Olympus XRD sample cell spacer choice

  1. 1. Choosing the Right XRD Sample Cell
  2. 2. TERRA and BTX II sample cells have 3 size options for the spacer Sample cell holder Front window Back window Spacer Spacer options: •175 µm (standard) •100 µm •75 µm Spacer WindowWindow Side View X-ray Path
  3. 3. X-ray interaction with a sample Diffraction: X-rays hit the sample and are bent at an angle related to their energy and the size of the crystal structure. Fluorescence: X-rays strike an atom, knocks out an inner electron. When the outer electron falls down to replace the removed electron, it lowers in energy. Energy difference is given off as an X-ray which the detector measures. Absorption: X-rays are absorbed by the sample and do not get through the detector. Incident X-ray Incident X-ray Crystal sample Crystal sample Incident X-ray Crystal sample Based on the sample chemistry the X-rays can interact in different ways – Diffraction, Fluorescence or Absorption
  4. 4. Increasing peak-to-noise ratio The goal is to limit fluorescence and absorption effects to produce high peak-to-noise ratio for a more identifiable diffraction pattern • The spacer determines the thickness of the sample which can influence how x-rays interact with the sample • A smaller spacer size reduces the amount of sample under the X- ray beam which reduces the diffracted intensity. • If the sample is subject to secondary fluorescence or absorption, this will also reduce the amount of that effect. It is a compromise of the diffracted intensity and fluorescence or absorption effects to optimize peak-to-noise ratio. • Many samples are not subject to strong secondary fluorescence or absorption and 175 um spacer is optimum.
  5. 5. Using sample density as a guideline for spacer choice Changing spacer size will require an adjustment to the particle size of your sample for proper convection. A rough guideline for the spacer and sieve size based on sample density is: * Mix the sample with ~50% glass to reduce the effective density SAMPLE DENSITY SPACER SIZE SEIVE SIZE 3 g/cm3 175 µm 150 µm 5 g/cm3 100 µm 75 µm 8 g/cm3 75 µm 50 µm 10 g/cm3 * 75 µm 50 µm
  6. 6. Increasing signal with spacer choice Overlay of 175 um (blue) and 75 um (red) patterns. Note the higher intensities for the thinner spacer. Zoom of overlay of 175 um (blue) and 75 um (red) patterns. Note the higher intensities for the thinner spacer. Using a thinner spacer allows more X-rays to make it through the sample to the detector which increases signal. In this example lead ore was originally tested using a 175µm spacer. High Pb- containing samples will strongly absorb X-rays generated by a Cu or Co source. Switching to a 75µm spacer increased the counts by 40%.
  7. 7. Choosing the right spacer • Olympus applications support can assist in choosing the right spacer and tuning the calibration for the specific spacer to get the best results for your application. • X-ray tube choice can also influence peak- to-noise ratio so this should be considered when purchasing an instrument.
  8. 8. Contact Olympus Applications Support BTX-II Benchtop XRD TERRA Portable XRD
  9. 9. For more information visit our website: Thank you!
  10. 10. For more information visit our website: Thank you!