let us consider some metal oxide particles, which shows cubic shape with some specific size of a singe cube in SEM image. now if we calculate crystallite size of the same with its PXRD data, then can we or should we compare the crystallite size calculate by PXRD and what is shown in SEM image.
Dear Guarav,
The principle of crystallite size measurements by x-ray diffraction is based upon the fact that the Fourier transform of different size crystallites varies inversely with the size of the crystallite. X-rays in the 0.15 nm range can measure crystallite sizes from approximately 2nm to 500nm.
The crystallite size is the average size of a coherent scattering domain (perfect arrangement of unit cells or perfect crystal).
In most cases the crystals observed in SEM are not "perfect" and will not lead to coherent scattering. Meaning, one crystal can consist of multiple crystallites. Also, in SEM investigations people often speak about crystal size but are in fact describing grain size.
Regards,
Sebastian
Dear Guarav,
The principle of crystallite size measurements by x-ray diffraction is based upon the fact that the Fourier transform of different size crystallites varies inversely with the size of the crystallite. X-rays in the 0.15 nm range can measure crystallite sizes from approximately 2nm to 500nm.
The crystallite size is the average size of a coherent scattering domain (perfect arrangement of unit cells or perfect crystal).
In most cases the crystals observed in SEM are not "perfect" and will not lead to coherent scattering. Meaning, one crystal can consist of multiple crystallites. Also, in SEM investigations people often speak about crystal size but are in fact describing grain size.
Regards,
Sebastian
I agree with this comment.
"In most cases the crystals observed in SEM are not "perfect" and will not lead to coherent scattering. Meaning, one crystal can sonsist of multiple crystallites. Also, in SEM investigations people often speak about crystal size but are in fact describing grain size." Sebastian Klaus
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