Scherrer equation is often used to determine the grain size using XRD data. However, this equation is only valid for grains smaller than ~100 nm. If my sample consists of significantly bigger grains, e.g., several micrometers, how I can determine the grain size using XRD data?
Dear Tianye Zheng first of all Scherrer Equation calculate crystal size not grain. Second, about your question I think it is possible.
Dear Tianye Zheng ,
Siddig Abuelgasim is right.
With Scherrer equation you estimate the crystallite size.
But the particles of the powder measured via XRD may be up to the µm regime.
Please see for example the answers and appropriate references therein of:
https://www.researchgate.net/post/What-is-the-suitable-particle-size-range-for-a-good-XRD-analysis
Best regards
G.M.
Yes. The upper limit of applicability of Scherrer equation and similar methods for characterizing diffraction line shapes is not about 100 nm, but rather about 500-700 nm. The line width must be statistically significantly larger than the line width of the standard. The larger the crystallite size, the greater the quality requirements of the diffractometer and the processing. This requires Rietveld analysis or at least full profile fitting and standards with a defined size of diffractive domains.
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