Crystallite Size from XRD (comments on method required)

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SUMMARY

The discussion centers around the challenges faced with XRD analysis using the Siemens (Bruker-Axs) D5000 due to issues with the Win-Crysize software, resulting in the need for alternative methods to calculate crystallite size. The user successfully utilized PeakFit software to perform baseline subtraction and Voigt peak fitting on extracted raw data, yielding FWHM values for specific 2-Theta reflections. The Sherrer Equation was applied to estimate crystallite sizes, with expected diameters ranging from 10 to 120 nm. The user seeks validation of their manual calculation method and results.

PREREQUISITES
  • Understanding of X-ray diffraction (XRD) principles
  • Familiarity with the Sherrer Equation for crystallite size calculation
  • Experience with PeakFit software for data analysis
  • Knowledge of FWHM (Full Width at Half Maximum) in peak analysis
NEXT STEPS
  • Research the application of the Sherrer Equation in different crystallography contexts
  • Explore advanced features of PeakFit for enhanced data analysis
  • Learn about alternative software options for XRD analysis, such as TOPAS P
  • Investigate methods for correcting instrumental broadening in XRD data
USEFUL FOR

Researchers, materials scientists, and laboratory technicians involved in crystallography and XRD analysis, particularly those seeking to calculate crystallite sizes and validate their methodologies.

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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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.
 
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