Increases in FWHM with doping indicate disordering in ceramic sample. How, and why?
Try the Williamson-Hall plot to explain what happens in your samples. Maybe the microstrain can be a reason in your case.
http://pd.chem.ucl.ac.uk/pdnn/peaks/sizedet.htm
Martin is right. Try to use Williamson-Hall plot where you can get particle size and strain as well.
Broadening of the XRD peak or say FWHM of the peak, can be broaden, if the Particle size is smaller or Strain in the material or Instrumental Broadening or any of the combination.
Williamson-Hall plot will be a simple method to separate the Size and Strain effects, once the instrumental broadening effect is removed.
As was stated in other question/answer thread, disorder may mean many things in crystallography.
Broadening of FWHM peaks in powder XRD may also be caused by many phenomena, some connected and many disconnected from "disorder" of any kind.
Allowing for a loose interpretation of your question and guessing what your problem can be, I guess that the question should be "How does inhomogeneity of a sample affect peak FWHM"... but maybe my guess is far away from your problem.
Writing about all different kinds of "disorder" you may mean in crystallography and also about each phenomenon that increases FWHM may do this post look like various book chapters. So you should either precise your question a bit more or read other posts with questions and answers that maybe talk about your specifi problem.
Best of luck
about your question: Increases in FWHM with doping indicate disordering in ceramic sample. How, and why?
with each doped atom more and more stress is induced in the ceramic sample due to size mismatch of the aoms in the matrix. with higher doping thisoften leads to grain reduction and sometimes to segregation of the diped material in to the grain boundaries stabilizing small grains. this stress formaion an d grain reduction is probably the reason for peak broadening (see our work on Fe-Ag thin films),
Hi Kapil Sood,
FWHM represents the distribution of lattice parameter around a given value. It could originate from stresses, crystallite size etc., or sum of the effects. From correlation point of view, reducing crystallite size is nothing but increasing disorder.
For an infinite crystal the FWHM is equivalent to instrumental broadening, if the thickness kept reduced to the order of X-ray wave length, that's where the wider FWHM resulted due to reduced resolution. It is the basic diffraction principle that If the number of diffracting slits (In case of crystal it is diffracting planes, in case of grating it is line density) is lower, the width of each diffracted spot is higher.
So, if one have the FWHM, one can back calculate the crystallite size using Sherrer formula.
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