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Powder Diffraction Data Acquisition |
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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 1 μm.
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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