>How does one handle the problem of bimodal particle size distributions by
>diffraction techniques? My previous experience at particle size measurements
>using laser light scattering indicates non-monomodality is the norm rather
>than the exception. Can powder diffraction resolve this?
The more easy method is to use in the Rietveld two equal phases with
different crystallites and microstrains (or different line-broadening).
Obviously the two phases must have the same crystallographic parameters;
better to have a program allowing to keep the two phases in sync while
refining some parameters. Out of the Rietveld the Warren-Averbach method
(fourier extraction) should obtain the bimodal distribution and using
analytical shapes you can use the same trick of two peaks for any
reflection with the same angular position.
Another approach is the IT method of Guerin et al. (Acta Cryst. 88?). I
builded a program for using it (the IT) including the microstrains (not in
the original work). One advantage is that you are not limited by an
analytical peak function and the fit become perfect.
The results of that work and a testing on the accuracy of bi-modal
distribution analysis are in L. Lutterotti & P. Scardi, Adv. in X-ray Anal.
35, 577.
Best regards,
Luca Lutterotti
-----------------------Luca Lutterotti----------------------------
Dipartimento di Ingegneria dei Materiali, Universita' di Trento,
via Mesiano 77, 38050 Trento, Italy
e-mail address : [EMAIL PROTECTED]
Home page : http://www.ing.unitn.it/~luttero
Mirror: http://www.ccp14.ac.uk/ccp/web-mirrors/lutterotti/~luttero/
Phone number :+39-0461-88-2414
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