Detailed steps of XRD data processing, search analysis and Origin graphing using Jade software

X-ray diffraction (XRD) is the first method used by human beings to study the microstructure of substances.

When a substance (crystalline or amorphous) is analyzed by diffraction, the substance is irradiated by X-rays to produce different degrees of diffraction phenomena, and by comparing the measured diffraction curves with the standard PDF card, information on the composition, crystal type, intramolecular bonding, molecular configuration, conformation and other information can be obtained.

X-ray diffraction has the advantages of no damage to the sample, no contamination, quickness, high measurement accuracy, and the ability to obtain a large amount of information about the integrity of the crystal.

Therefore, X-ray diffraction analysis, as a modern scientific method for analyzing the structure and composition of materials, has gradually gained wide application in the research and production of physics, chemistry, earth science, material science and other disciplines.

Therefore, proficiency in XRD data processing, analysis and graphing is essential for modern science and engineering students.

Preparation before XRD test

Before the XRD test, we must first do the XRD test sample type and preparation method in mind, first of all, to understand the physical and chemical properties of the sample, such as whether it is flammable, easy to moisture, easy to corrosion, toxic, volatile.

XRD can measure block, powder and thin film samples, which can be ceramics, metals, compounds, organics and so on.

Block samples need to have their surfaces polished to expose their fresh surfaces. (The area is usually not less than 5mm x 5mm, but if the sample is too small, it should be centered to ensure that the X-rays are on the sample surface before the test begins).

Powdered samples need to be processed before use, first of all, the use of alcohol to clean the slide to ensure maximum removal of other substances on the slide to avoid interference with the test results.

The powdered sample is then laid flat on the surface of the slide and flattened using another slide. For smaller metal powder particles, the effect of oxidation behavior during sample preparation on the test results is considered.

Figure 1: Sample Specimens and Sample Stands

XRD data processing

XRD data were analyzed using MDI JADE software (before analysis, make sure that your computer is synchronized with the PDF database, http://www.icddchina.com/).

As the most extensive application of XRD, the identification of the physical phase is mainly based on the measured diffraction pattern of the sample and the given search conditions in the PDF card library of the “standard card” for comparison, and then based on the three strong peak position, peak intensity and the elements in the sample to determine whether there is such a physical phase.

The following are the specific steps of the phase search:

Import Files

XRD tests are generally exported to three formats, we can directly drag and drop the .raw file into it.

Unconditional search

Click on the toolbar at the top of the screen, enter the simultaneous selection of a variety of PDF sub-library, the search object selection of the main phase (S/M Focus on Major Phases) and then click the “OK” button, enter the “Search/Match Display “window.

Pop-up Search/Match Display window

At this time, by clicking on the window below the search list can be observed pdf card and diffraction spectrum match, generally in accordance with the value of the FOM is sorted, the smaller the value of the FOM, indicating a higher degree of match.

Qualified Element Search

When the unconditional search can not directly find the corresponding object phase, can be considered to qualify the element search. First of all, right-click on the home page of the software, select “Use chemistry filter” in the dialog box that appears, continue to select the specific classification corresponding to the item you are measuring on the left side of the dialog box, and then click on the OK button in the lower right corner to enter the element selection interface.

After selecting the elements, click on the OK button in the upper right corner to enter the curve fitting stage smoothly. At this point, we can see that the peak positions are already well matched.

For general samples, the last two rounds of search can basically determine the sample phase, but if there is still can not be retrieved out of the physical phase exists, can be used to determine the physical phase of single-peak search.

In the main window, select the “Calculate Peak Area” button, draw a bottom line under the peak, the peak is designated, right mouse button click on the “S/M”, at this time, the search object becomes gray and can not be adjusted (Jade 5 is displayed as “Painted Peaks”). Painted Peaks” in Jade 5).

At this point, you can qualify the element or not, and the software will list the standard cards that have diffraction peaks at this peak position.

Double-click on the searched phases to bring up the corresponding PDF cards, so that you can get the corresponding crystal surface index, 2-theta and other information.

Grain size analysis

The calculation of the grain size of diffracted powder is mainly based on the half-width at height of the diffraction pattern to perform the relevant calculations.

If the diffraction peak is simply regarded as a triangle, then the area of the peak is equal to the height of the peak multiplied by the width of the half height. The height at half height has a special term called “half width at half height”, which is written in English as FWHM.

The specific procedure is as follows:

(1) as shown above for the object phase search, after determining the corresponding object phase, right-click the common toolbar in the picture button, set the deduction Kα2, deduct the background operation. The red box in the figure can be checked.

Remove the front:

After removal:

Click on the button for the image in the common toolbar for smoothing, and perform a full-spectrum fitting operation.

Click on the symbols at the top of the page after fitting to read out the grain size values directly.

Note: When using XRD for grain size calculation, the premise is to assume that the grains are “spherical”, so the measured grain size is not very reliable, and the result is always smaller than SEM and TEM, but when SEM and TEM are not available, the results have a certain reference basis.

Data Graphing

At present, most of the scientific papers basically use Origin software for graphing. When plotting, 2θ is taken as the horizontal coordinate, and the diffraction intensity is taken as the vertical coordinate. The specific graphing process is not described in detail here.