We need to give two different parametrs during XRD pattern measurement i.e. Step size and Step time. Based on this we calculate scan rate of measurement. Is step size and X-ray beam width has any relation?
Dear Rahul Pujari ,
you know that in XRD measurement the x-ray diffracted beam intensity is measured as a function of the scatter angle 2theta or from a 'reflection' point of view on the glancing angle theta of both, the incoming as well as the 'reflected' beam, part of which is being picked up by the detector.
The step size is the increment of the angle theta (i.e. the increment of the sample angle with respect to the primary beam) for each measurement step and step time is the time duration while the acquisition of the x-rays is performed at each theta position.
There is no relation to the x-ray beam width.
Beam width is governed by an appropriate slit and its value is chosen to optimally illuminate the sample surface.
Dear Rahul Pujari ,
you know that in XRD measurement the x-ray diffracted beam intensity is measured as a function of the scatter angle 2theta or from a 'reflection' point of view on the glancing angle theta of both, the incoming as well as the 'reflected' beam, part of which is being picked up by the detector.
The step size is the increment of the angle theta (i.e. the increment of the sample angle with respect to the primary beam) for each measurement step and step time is the time duration while the acquisition of the x-rays is performed at each theta position.
There is no relation to the x-ray beam width.
Beam width is governed by an appropriate slit and its value is chosen to optimally illuminate the sample surface.
Gerhard Martens has already explained it well. I just want to add a few more things.
Briefly, step-size are the scattering angle intervals after which you acquire data. In diffraction experiments, generally we prefer a step-size of ≤0.05°, basically it is kind of an instrumental least count for the particular experiment. If you are providing information on some peak-shift, deconvolution of broad peak into the successive components or any other quantitative data, it is the rough uncertainty associated with it.
In most instruments, the default step-size is 0.02°, and it is all okay to use. If you try to decrease it less than 0.01°, it will not provide any new thing, as mostly the detector or sample-holder is not mechanically rotated with a better accuracy.
Step time on the other hand is the time spent to acquire data against each data point. It is equal to the total time of measurement, divided by the number of data points. Slower scan is specially recommended for Rietveld refinement.
Beam width, aperture etc are less important for a particular experiment. Generally, the company, that supplied the instrument recommends some settings, optimal for most materials. And you are good to go with those values. It'll just enhance the resolution and overall quality of data. These are not related to quantitative analysis that much; and hence you don't need to change those values after each experiment.
Thank you Gerhard Martens and Souvik Bhattacharjee for your comments. I am satisfied with it.
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