I have attached an excel file with the quantification of a mineral I conducted EDS on. I have more excel files of minerals too as I know EDS spectra for only 1 sample will certainly not be accurate at all. But I was wondering if there's any way to determine a chemical formula or the relative % of each element within the mineral?
I tried looking online and am struggling to understand the K-ratio? the data I have uploaded is directly from the software used for SEM-EDS.
Wt&, At% and K-Ratio is given along with Z, A and F.
If it is possible to obtain a chemical formula, would someone be able to explain how?
Thank you!
In general, it is not a good idea to use EDS to find a chemical formula. Especially for a naturally occurring samples. Technically, it is possible, but such data cannot be called reliable.
In addition to Vladimir's answer:
EDS takes only a thin (about 1 um) layer from the surface of the sample. Obviously, it means that it is extremely sensitive to contamination, oxidation, selective erosion, and other factors which make the surface chemically different from the volume. To minimize this effect, the surface should be as clean as possible (fresh cleavage, FIB milling right before the analysis, etc) and it is necessary to get EDS spectra for as many points from different parts of the sample, as possible.
Janki Patel
You can assume that your mineral consists of oxide with stable valencies K2O, Al2O3 ... and compare (calculate) with the results of the EDS analysis. Checking can be done by XRD
Yuri Mirgorod Hi, could you please elaborate? I wanted to create a chemical formula, with the amount of each element. I have done xrd, but I just wanted to see if there was a way to obtain chemical formulas from eds.
1. The SEM is not a perfect tool to check the exact composition, because you have "Oxygen" in your composition.
2. You can calculate approximately by following steps which are in the excel file
As you know the composition of the materials which you prepared, you can just check with reference to the excel sheet where I added example data.
Janki Patel
Talk to the chemists at your university. They will help you.This is a simple procedure.
It is possible to do, but rather difficult. You have to use standards - standardless analysis you used before is useless for your task. It is advisable to have standards which are somewhat close in composition to phases in your specimen. Good command of EDS quantitative analysis. With all of the above your task is doable. Also it's helpful to have special geological software package (usually sold as an option).
In general, it is not a good idea to use EDS to find a chemical formula. Especially for a naturally occurring samples. Technically, it is possible, but such data cannot be called reliable.
In addition to Vladimir's answer:
EDS takes only a thin (about 1 um) layer from the surface of the sample. Obviously, it means that it is extremely sensitive to contamination, oxidation, selective erosion, and other factors which make the surface chemically different from the volume. To minimize this effect, the surface should be as clean as possible (fresh cleavage, FIB milling right before the analysis, etc) and it is necessary to get EDS spectra for as many points from different parts of the sample, as possible.
Standardless EDS is very inaccurate, especially in the quantification of light elements. The ratios of the determined elements can be influenced by a number of factors. However, the calculation of a structural formula is a routine matter, but it has one premise. We trliably know what mineral it is. A column of atomic percentage data is taken and the whole is normalized with respect to some component.
From the attached data it is clear that some feldspar was probably analyzed (probably Na-K-Ca "ternary" feldspar?). However, the Mg content indicates a possible admixture of something else. The attached analysis is not very good.
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