Zahra - Prof. Leoni's recommendation is that you need to take some time to go through the basics, and I fully agree. There are many excellent textbooks which explain exactly what you need (e.g. Cullity, Pecharsky & Zavalij, Snyder, Warren, ...). Attempting to use a program like EVA without really knowing what you are doing is a recipe for disaster - how will you know if your answer is right or wrong?
You can probably locate a phase diagram by searching the literature, or there may be one collected in the Phase Diagrams for Ceramists series published by the American Ceramic Society. La(Fe,Co)O3 is a material that has been extensively studied over many decades, so you should find LOTS of information.
I cannot tell from the plot you provided what radiation you were using. Can you please post this?
You can use the equation contain miller indices and spacing d. This is different form from cubic , tetragonal or hexagonal phase.
Ok... I want to calculate a,b, c for my samples but i dont know how to use xrd patterns
... suggesting someone asking this question to use the Rietveld method is like suggesting a 5y/o guy to jump on a car and drive it through NYC!
The first suggestion is to open a good crystallography book, and a good book on X-ray diffraction (Warren's book can be found for $10 online). This is in my opinion a good prerequisite if you want to start analyzing a diffraction pattern on your own.
There are a few other suggestions:
- check the phase diagram or, if known, the cell parameters for the various members of LaFeO3-LaCoO3 family. I suppose most of the doping affects the Fe site... but I cannot swear the La site is not influenced. If you have full miscibility (Fe and Co tend to create different structures so this is not given for granted), then the effect of the substitution is certainly a change in the cell parameter(s)
- Your signal/noise ratio and the number of points per peak are not that great (it seems you have some problems as I think the pattern is in counts per second and not counts as indicated...). If they are real counts then for sure you are working under very strange conditions.. most of those you identify as peaks are actually hidden under the background noise
- give more information when you place a question: for instance we don't even know if you are dealing with a powder specimen or a film (they can both give similar patterns). I definitely do not understand what Shannon has do do with diffraction.. (check also the spelling for LAW)...
- ask your supervisor: in many cases this saves a lot of time here. I would definitely not be happy to know that one of my students is placing such a question in a community of experts (instead of asking me and then spending some of his time learning).
RG is not a substitute for books and for learning. People may be kind and answer, but if you don't know what you are talking about or the questions are ridiculously basic (i.e. a few days on a book and you would not dare asking this), the risk is that non experts answer and that you would get useless or wrong feedback. And perhaps publish some wrong evaluation based on the advice you got from here....
First check which phase is observed in your material .You can use the equation contain miller indices and spacing d. This equation has different form for different phase. I am suggesting the book by B.D. Culity -Elements of X-ray diffraction, 2nd Edition (Addison Wesley) .It is available online.
Dear Matteo Leoni: thank you for your complete comment...you know i searched these peaks by eva software (bruker) but my problem is i dont know how to use this software to calculate cell parameters...by the way where can i find LaFeO3-LaCoO3 diagram?
Zahra - Prof. Leoni's recommendation is that you need to take some time to go through the basics, and I fully agree. There are many excellent textbooks which explain exactly what you need (e.g. Cullity, Pecharsky & Zavalij, Snyder, Warren, ...). Attempting to use a program like EVA without really knowing what you are doing is a recipe for disaster - how will you know if your answer is right or wrong?
You can probably locate a phase diagram by searching the literature, or there may be one collected in the Phase Diagrams for Ceramists series published by the American Ceramic Society. La(Fe,Co)O3 is a material that has been extensively studied over many decades, so you should find LOTS of information.
I cannot tell from the plot you provided what radiation you were using. Can you please post this?
thank you... Edward... Its Cu K alpha... you know im familiar with cality book and almost read it carefuly...but i wanted the answer as soon as possible from sb who is professional...:D... thats it...Many many thanks for your answer... i agree with you and prof Leoni...
You probably have already discovered that Cu k-alpha is a bad choice (though it may be your only available option) for this material, due to fluorescence of the cobalt and iron by copper radiation. Your data does not show much fluorescent background, so I am guessing that you are either (1) using a diffracted beam monochromator, or (2) showing data with the background subtracted. Perhaps that is also why I don't see much evidence of Cu k-alpha2 in your peak profiles?
Yes it was the only available option...but i read lots of article which used cu kalpha as well!!! For this material...
Zahra.. probably you need to read it a few more times.. and perhaps understanding vs reading. The name of the author is in any case Cullity and not cality.
If you read it carefully, you find a relationship between hkl, cell parameters and dspacing. If you don't know what you are doing, any software can give you any number, especially with an orthorhombic structure where a,b,c can be exchanged simply by changing the space group. settings.
The pattern is clearly highly processed, but the fact the PDF card matches means that the one displayed here is pure LaFeO3:
5.569
7.8547
5.553
Unfortunately the space group is not clear (Pb*a)... Your values are close to those, but I definitely don't know what you are going to do with those numbers, though. Without a proper modelling of the pattern (and this means knowing not just the real measurement but also how your instrument behaves) it is not possible to answer your question with a good accuracy
Zahra, the fact there are masochists around does not justify the assumption that everybody should be a masochist...
Dear Matteo Leoni: about Cullity... It was misspelled ...thank you for your full answer ...
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