FYI, I have used XRD analytical technique for phase identification of a crystalline transition metal hydroxide. The analyzed material was finely grounded. I got some short and long peak for particular compound. How can I identify these peaks?
Masruck Alam
I’m not sure why you (or maybe a technician) is running samples on XRD without apparently any knowledge of what you’re doing and why.
Have you not been on a basic XRD course in your metallurgy undergraduate work? Is there no one in your department that you can ask? This should be your first port of call - not ResearchGate... Have you read any textbooks/been to the library/used the internet (beyond this incredibly basic question)? What are your course textbooks for XRD? Can you use the information you have to calculate unit cell data?
I assume you have knowledge of what materials you mixed and the heat treatment? Can you share this information with us? What XRD instrument and software were you using? These programs invariably have suggestions for any materials corresponding to your XRD peaks.
Alan F Rawle
Thank you for your answer. Yes, we had XRD course in undergraduate work.
For my thesis work, I prepared some layered double hydroxide sample for adsorption of organic compound. I analyzed sample on XRD to identify the crystalline phases by matching peak position. However, both raw and treated sample analyzed to know how the peak changes after loading with the organic compound.
We do not have XRD machine at our university laboratory. I did characterization from Bangladesh Council of Scientific and Industrial Research center. They used D8 advanced XRD analyzer. They did not provided any reference peak data for my analyzed materials. That's why I got problem to identify the peak position of my expected materials. However, I also searched reference data in Open crystallographic database for my compound.
Thanks for your suggestion.
The XRD spectrum is not a picture for an article or dissertation (as well as any other spectrum). Structure spectrum analysis is quite a professional job, giving lot of information. But to analyze the roentgen peaks, you must have knowledge and skills that significantly exceed the standard undergraduate course. Now this is done by software, both supplied with the equipment, and freeware. It is difficult to imagine a person doing this "manually" (although I did it myself many years ago).
Therefore, the most optimal thing is to request the center where the spectrum was taken for they to make phase analysis for you sample. It's not so hard, the Bruker D8 (EVA) software is capable of it. It is surprising that they gave out a "bare spectrum" ...
Vadim S. Gorshkov
Thank you for your answer. I agree with you, we need better understanding and skills to perform this job. However, we have learned only the basic of XRD in undergraduate study.
I asked them for phase analysis of my sample but they told me it is a difficult and time consuming job. Unfortunately, we do not have much opportunity here to do research because of the limitation of instruments.
Masruck Alam
Now processed of results are the standard in XRD use, and staff know it. Moreover, it does not require any additional effort - the software works, not the person. I would also understand if it was a full-profile analysis (TOPAS program in the case of Bruker, there are really needed the brain turned on), but it's still funny.
If they don't do it with the software and JCPDS databases, what can a user do on his knee?
By the way, to process the data given by you experts need to know at least the wavelength (CuKalpha ???) and data in tabular form, not a graph.
Masruck Alam
I'm sorry for your difficulties but as Vadim S. Gorshkov states, your answers lie in the software and the instrument operators. Again, you should at least have some knowledge of the materials that you have synthesized. You can then research hydroxide XRD patterns on line for comparison. If you have a mix then the software is everything - you can't do Rietveld (for example) by hand.
For example, see attached from DOI: 10.1039/C8RA00269J for XRD of LiOH
Masruck Alam
A number of your peaks show distortion. This can mean at least 2 things:
- Poorly alloyed systems, mixtures, closely overlapping peaks from elements - i.e. related to the sample. Again it would help to outline your synthesis protocol including materials. You're not helping us to help you...
- Instrument misalignment - artifact related to the instrument. Unlikely, but what is being used to verify the XRD system? In my day, late 1970's, we used crushed quartz. Now you may use LaB6 or other materials
Again you've not indicated to Vadim S. Gorshkov what wavelength is being used. Cu Kalpha is common, but in certain circumstances e.g. Fe, there may be reasons (e.g. fluorescence) for using another wavelength. Given your interaction with the operators of the instrument, then anything seems possible...
Plus a number of your peaks do not have 2 theta data associated with them.
A very minor point, but I'm a pedant and into trivia, why is your plot shown as a jpeg and not a .gif (or even .png or .tiff)?
Alan F Rawle
We prepared Al/Ca, Al/Cu, Al/Zn, Al/Ni LDHs followed by coprecipitation method. Hydroxide compound of different metals and other compound might present there, for example, Al(OH)3, Ca(OH)2, CaCO3, NaCl.
I am not sure what wavelength used for XRD, performed XRD patterns in 2 theta. The technician only provided Excel datasheet and a jpeg images.
Fact is, I have analyzed sample as my supervisor suggested. However, if I knew about it before we can get everything from the software I could ask for it.
Thanks.
Masruck Alam
The Ca(OH)2 is likely to be changed to CaCO3 from CO2 in the air, so I'd not be expecting Ca(OH)2. Mixtures need more complex analysis - you can't do this easily from the provided information.
X-Ray Diffraction, frequently abbreviated as XRD, is a non-destructive test method used to analyze the structure of crystalline materials. XRD analysis, by way of the study of the crystal structure, is used to identify the crystalline phases present in a material and thereby reveal chemical composition information.
XRD peaks are produced by constructive interference of a monochromatic beam of X-rays scattered at specific angles from each set of lattice planes in a sample. The peak intensities are determined by the atomic positions within the lattice planes. To check the XRD pattern of any sample with the reference from JCPDS.
JCPDS files can be found in archive software available from the ICDD (http://www.icdd.com/) . Their software is not free, but there is very reasonable pricing for academic institutions. Depending on what materials you are investigating, you can find some sites where people are voluntarily depositing diffraction files for free download. Two such places are: http://www.crystallography.net/cod/ and http://comptech.compres.us/tools/jcpds/.
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