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What is JCPDS Card Database and How to Use It for XRD Analysis
JCPDS card database, also known as ICDD database or PDF database, is a collection of reference data for identifying crystal structures and phases using X-ray diffraction (XRD) technique. JCPDS stands for Joint Committee on Powder Diffraction Standards, which was the original name of the organization that created and maintained the database. In 1978, the name was changed to International Centre for Diffraction Data (ICDD) to reflect its global scope and mission.
The JCPDS card database contains information such as chemical name, formula, crystal system, space group, lattice parameters, atomic coordinates, interplanar spacings, and diffraction intensities for thousands of materials. The database is updated regularly with new data from peer-reviewed journals and verified by ICDD experts. The database is available in different formats and products, such as PDF-2, PDF-4+, PDF-4/Minerals, PDF-4/Organics, etc., depending on the type and number of entries.
To use the JCPDS card database for XRD analysis, one needs to have access to the database product and a software that can search and match the experimental XRD pattern with the reference data. Some examples of such software are X'Pert HighScore, Jade, Topas, Match!, etc. The software can perform different types of analysis, such as phase identification, Rietveld refinement, quantitative analysis, etc., depending on the features and capabilities of the software.
To perform phase identification using JCPDS card database, one needs to follow these steps:
Obtain the experimental XRD pattern of the sample using an X-ray diffractometer.
Load the experimental XRD pattern into the software and select the appropriate scan range, background subtraction, peak detection, etc.
Select the JCPDS card database product as the reference database and specify the search criteria, such as chemical elements, formula, crystal system, etc.
Run the search and compare the experimental XRD pattern with the reference data. The software will display a list of possible matches with their similarity scores and other information.
Select the best match or matches based on the similarity score, peak positions, intensities, etc., and confirm the phase identification.
The JCPDS card database is a valuable resource for XRD analysis and can help researchers to identify unknown phases, study phase transformations, determine crystal structures, etc. However, one should also be aware of the limitations and uncertainties of the database and the software, such as incomplete or outdated data, errors in data entry or processing, differences in experimental conditions or sample preparation, etc. Therefore, one should always verify the results with other sources of information and use proper scientific judgment.
In this section, we will show an example of an XRD pattern and how to use the JCPDS card database to identify the phases present in the sample. The sample is a mixture of alumina (Al2O3) and magnesia (MgO) powders that were sintered at high temperature. The XRD pattern was obtained using a Cu KÎ radiation source and a 2Î range of 10Â to 80Â. The XRD pattern is shown in Figure 1.
Figure 1: XRD pattern of Al2O3-MgO sample
To identify the phases in the sample, we use X'Pert HighScore software and select the PDF-4+ database as the reference database. We specify the chemical elements Al, O, and Mg as the search criteria and run the search. The software displays a list of possible matches with their similarity scores and other information. The top five matches are shown in Table 1.
Rank
PDF Number
Chemical Name
Formula
Similarity Score
1
01-075-0209
Alumina
Al2O3
0.999
2
01-075-1526
Magnesia
MgO
0.998
3
01-075-1519
Magnesium aluminate spinel
MgAl2O4
0.996
4
01-075-1518
Magnesium aluminate spinel (inverse)
MgAl2O4
0.995
5
01-075-1517
Magnesium aluminate spinel (random)
MgAl2O4
0.994
Table 1: Top five matches from PDF-4+ database for Al2