Crystallite Size from XRD (comments on method required)

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In summary, the conversation discusses the issue with the XRD Crystallite Size software and the need for manual calculation methods due to budget constraints. The use of PeakFit software and the Sherrer Equation is described, along with data and parameters used. The expected crystallite size ranges for the sample are also mentioned.
  • #1
Model 500
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Hi, the XRD in question is a Siemens (Bruker-Axs) D5000 and apologies as this may be a somewhat long post.

A member of staff tried to change password permissions on our XRD Crystallite Size software (Win-Crysize) and the copyright dongle for the software didn’t like this, so we now have a not-altogether inexpensive brick. Unfortunately our budget is already maxed out, so we cannot afford replacement software for the foreseeable future (this would be TOPAS P from Bruker-Axs).

However, luckily the XRD Control software (XRD Commander) and the XRD plot viewing software (Eva) are unaffected, and as such we can still perform XRD analysis (admittedly of a somewhat limited fashion).

This was fine until now, where I have had a request to obtain crystallite size for a sample. I now need a critical eye and input/suggestions on my manual calculation method.

I have obtained a 30-day trial of software called PeakFit, with this I have managed to use the extracted raw data (see attached .txt files), which when converted it into an Excel format can be imported into PeakFit.

View attachment sample raw data.txt
View attachment NaCl raw data.txt

Now PeakFit isn’t strictly speaking XRD software, however, it has allowed me to do a baseline subtraction, FFT Filter smoothing of the raw data and do a Voigt(amplitude) peak fit.

All this has enabled me to obtain a FWHM value for the Reflections of interest i.e. those at 2-Theta 7.0, 10.5 and 18.5, the FWHM values (from PeakFit not raw data):

7.0 = 0.202
10.5 = 0.230
18.5 = 0.265

Using the same approach above on an NaCl Std, to take account of instrumental broadening etc, the NaCl FWHM = 0.153.

Other parameters are:
x-axis is 2-Theta scanned from 3 to 35
y-axis is counts (scintillation detector)
λ = 1.54
k = 0.9

Now, as the crystallite size isn’t in the μm range I have went with the following version of the Sherrer Equation:

d = 0.9λ
...BcosΘ

Where B = bsample-bstandard


Please see attached Excel spreadsheet for details. (please rename XRD Crystallite Size - Sample Calc.txt to XRD Crystallite Size - Sample Calc.xls)

View attachment XRD Crystallite Size - Sample Calc.txt

We expect the sample to have an average primary crystal diameter of between 40 and 120nm.
Crystallite diameter perpendicular to β (001) plane of between 22 and 33nm
Crystallite diameter perpendicular to monoclinic β (200) plane of between 17 and 27nm.
Crystallite diameter perpendicular to β (010) plane of between 10 and 20nm.

Although it looks like I have obtained an answer within the ranges above I really need to know; Am I fudging it or does my method stand up to scrutiny?

All suggestions, comments and questions welcome.
 
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  • #2
the lamda should be A, right?

Model 500 said:
Hi, the XRD in question is a Siemens (Bruker-Axs) D5000 and apologies as this may be a somewhat long post.

A member of staff tried to change password permissions on our XRD Crystallite Size software (Win-Crysize) and the copyright dongle for the software didn’t like this, so we now have a not-altogether inexpensive brick. Unfortunately our budget is already maxed out, so we cannot afford replacement software for the foreseeable future (this would be TOPAS P from Bruker-Axs).

However, luckily the XRD Control software (XRD Commander) and the XRD plot viewing software (Eva) are unaffected, and as such we can still perform XRD analysis (admittedly of a somewhat limited fashion).

This was fine until now, where I have had a request to obtain crystallite size for a sample. I now need a critical eye and input/suggestions on my manual calculation method.

I have obtained a 30-day trial of software called PeakFit, with this I have managed to use the extracted raw data (see attached .txt files), which when converted it into an Excel format can be imported into PeakFit.

View attachment 12827
View attachment 12828

Now PeakFit isn’t strictly speaking XRD software, however, it has allowed me to do a baseline subtraction, FFT Filter smoothing of the raw data and do a Voigt(amplitude) peak fit.

All this has enabled me to obtain a FWHM value for the Reflections of interest i.e. those at 2-Theta 7.0, 10.5 and 18.5, the FWHM values (from PeakFit not raw data):

7.0 = 0.202
10.5 = 0.230
18.5 = 0.265

Using the same approach above on an NaCl Std, to take account of instrumental broadening etc, the NaCl FWHM = 0.153.

Other parameters are:
x-axis is 2-Theta scanned from 3 to 35
y-axis is counts (scintillation detector)
λ = 1.54
k = 0.9

Now, as the crystallite size isn’t in the μm range I have went with the following version of the Sherrer Equation:

d = 0.9λ
...BcosΘ

Where B = bsample-bstandard


Please see attached Excel spreadsheet for details. (please rename XRD Crystallite Size - Sample Calc.txt to XRD Crystallite Size - Sample Calc.xls)

View attachment 12829

We expect the sample to have an average primary crystal diameter of between 40 and 120nm.
Crystallite diameter perpendicular to β (001) plane of between 22 and 33nm
Crystallite diameter perpendicular to monoclinic β (200) plane of between 17 and 27nm.
Crystallite diameter perpendicular to β (010) plane of between 10 and 20nm.

Although it looks like I have obtained an answer within the ranges above I really need to know; Am I fudging it or does my method stand up to scrutiny?

All suggestions, comments and questions welcome.
 
  • #3
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What is the purpose of determining crystallite size from XRD?

Determining crystallite size from XRD is important because it provides valuable information about the structure and properties of materials. It can help researchers understand the behavior of materials at the atomic level and provide insights into their physical and mechanical properties.

What is the XRD method used for determining crystallite size?

The XRD method, or X-ray diffraction method, is a technique that uses X-rays to determine the structure and properties of materials. It works by shining a beam of X-rays onto a sample and measuring the diffraction pattern that is produced. This pattern can then be analyzed to determine the crystallite size of the material.

What are the limitations of using XRD for determining crystallite size?

XRD has some limitations when it comes to determining crystallite size. One limitation is that it cannot provide information about the size and shape of individual crystallites, but rather gives an average size for the entire sample. Additionally, XRD may not be accurate for materials with very small or very large crystallite sizes.

Are there any other methods for determining crystallite size besides XRD?

Yes, there are other methods for determining crystallite size such as transmission electron microscopy (TEM), scanning electron microscopy (SEM), and small-angle X-ray scattering (SAXS). These methods have their own advantages and limitations, and the choice of method may depend on the type of material being studied.

How accurate is XRD in determining crystallite size?

The accuracy of XRD in determining crystallite size depends on various factors such as the quality of the sample, the parameters used in the XRD analysis, and the skill of the operator. However, XRD is generally considered a reliable and effective method for determining crystallite size, especially when used in combination with other techniques.

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