Powder Diffraction Data Acquisition

 

The representative samples for powder diffraction data acquisition should be normally sent with sample submission form, clearly marked and have brief description of origin and instructions describing the type and parameters of diffraction experiments.

Powder diffraction data  collection requests using conventional laboratory diffractometers should include the following information: angular range, radiation source type, step size (or continuous run), diffraction in reflection or transmission mode, total or step counting time etc. Example: A heavy metal contaminated soil #200-#400 mesh sieve dry fraction, possible with clay minerals, metallic and/or corrosion products, not pulverized, to be run using cobalt anode. Two theta angular range: 5-65, step size 0.05 degrees two theta, counting time 5 sec per step: (65-5) / 0.05= 1200 data points 5 sec = 6000 sec total = 1.6 hours.

If the data will be used for phase quantification purposes or Rietveld structure refinement and the sample has high amounts of iron containing phases we will recommend you to use cobalt anode instead of copper one to eliminate the errors arising from microabsorption.  Cobalt  anode will provide the results not sensitive to microabsorption with added advantage of greater angular dispersion.

To avoid the extinction effect experimentally, the particle sizes of the phases should be grounded to less than 1μm. To achieve 1% absolute accuracy in phase quantification by Rietveld method for sample volume of 20 mm3 and using Bragg-Brentano geometry, the particles should be grounded to less than 0.8μm. There are many other important parameters involved in sample preparation and data collection strategies which we can help with.

If you are not experienced in diffraction methods, please let us know, what kind of samples you are dealing with and what kind of problems you are trying to solve. Our experienced staff will  help you with optimal experimental parameters.

 

 

 

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