[sdpd] Re: random orientation in flat platesnanocrystallites

[Armel Le Bail <armel...@fluo.univ-lemans.fr>]

>We have treated the diffraction image obtained with FIT2D and have taken
>into account all the parameters you mention...
>it is to note that the width W=0.0049 is that of the instrument
>and not that of my powder as far as i take into account the width of peaks
>applying the classical Debye-Scherrer law (as proposed by the fullprof
>program).

Sometimes the size of the coherently diffracting domains seen by
X-ray or neutron may not match the size observed by electron
microscopy. However, it can only be smaller... So that, if you
are sure of your 30nm, and also sure that this dimension is 
associated with only one crystallographic direction (say the c
direction in your rhomboedral nanocrystals - not so nano with
200x200nm - described in hexagonal setting) and if you effectively
see the 00l reflections on your powder data, and they have a quite
low FWHM corresponding to the diffractometer resolution (W=0.0049),
then, there is only two explanations ;-) :

You did not look at the same sample by both methods.
   - The preparation for the microscope, or the exposition to the
      electron beam has introduced fragmentation, or
   - the sample submitted to synchrotron radiation was annealed.

Of course, I can be wrong, there are a lot of "if" above. But
this is the only rational/logical explanation I can give.

Best,


Armel Le Bail - Universite du Maine, Laboratoire des Fluorures,
CNRS ESA 6010, Av. O. Messiaen, 72085 Le Mans Cedex 9, France
http://www.cristal.org/