Crystal size is determined using the Scherrer equation (e.g., size = 0.9 * wavelength/ (widht of the sacttering peak in radian* cos (half the scatteing angle). For coating thickness (assuming thickness < um), you need to have reflectvity results. If you do, then to a first approximation, you can use Braggs law to get the coating thickness. You can also other techniques such as ellipsometry to determine the coating thickness.

Using the Scherrer equation for this kind of application can be kind of tricky mainly because of 2 issues:

1) XRD line broadening is not only affected by the crystallite size but also by the materials crystalinity and by intrinsic instrumental broadening. So that the particle size you measur may not be exactly the real value.

2) The shape constant (k = 0.89 = 0.9) is valid for spherical crystallites. That may be also not true for your system specially for thin films.

Maybe you can use the Williamson-Hall method that provides concominatly the real crystallite size amd the structural strain. But I am not really sure if it cam be applied to hin films.

Dear researcher, the coating thickness, it can be calculated from the equation of X-ray absortion, you can find it in Cullity, X-ray Diffraction or in other Books. I was did calculations of X-ray penetration and how to do it you will find in some of my publications in researchgate.

The second measurment of the crystal size you can find from the broadennig of peaks reflections that are happened in the range of 1000 anstrongs and less in grain diameters.

I think, that this information can be usefull for you.

The method for calculation of X=coating thickness is possible by using equation of absorpion of X-ray (Cullity), I/Io=1-exp ((Greese(miu)xX (layer thickness)/sin(Greese Teta)) when the relation between I/Io ca be about 0.98.

The second answer are about the crystal size that is depended on the peak broadening in the case that dimension of the grains are smaller from 1000 anstroms. Actually, is X-ray files that can do for you the work.