On vendredi 30 Avril 2004 17:15, Ling Fei Zhang wrote:
> Dear all,
>
> Recently, one of my friends ask me, coz he is neutron stranger, and his
> question is about one of his project in which they are studying the
> nanometer-sized domain effect on Nickel ferrite, NiFe2O4, different from
> conventional formula and occupancy which are used to describe the
> stoichiometry and they found significant anomalous evolution with the
> different grain sizes. the exiting techniques, Mosbauer Spectrum and XRD
> analysis tell them quantitatively the changes of Fe partial occupancy,
> however, both the Mosbauser spectrum and XRD have no capability to study
> Nickel partial occupancy situation due to the nature of Mosbauer spectrum
> and closeness of atomic number.
>
> Recently they asked me the possibility of neutron diffraction, and since
> the they use the natural abundance Nickel and iron as the precursor of
> sample preparation, so unfortunately, the similarity of coherent scattering
> length between the Ni and Fe makes trouble again, and there is no good
> perspective for this kind of set-up, though there seems a isotope
> substitution solution which presumably makes a good contrast, however, for
> the moment, they didn't give priority to this idea.
>
> What I am looking for is if there is any solution to study the the compound
> with close neutron scattering length, I supposed to see, there is some
> clever method to solve this issue based on the tips of data analysis from
> neutron diffraction, or any others?
The solution can come from resonant (anomalous) X-Ray diffraction, which
will allow you to separate Fe and Ni by measuring X-Ray diffraction patterns
near their respective absorption edges.
for a review see "Resonant Diffraction"
Hodeau, J.-L.; Favre-Nicolin, V.; Bos, S.; Renevier, H.; Lorenzo, E.; Berar,
J.-F.;
Chem. Rev. 101 (2001); 1843-1868
Also see recent examples:
J. Appl. Cryst. (2003). 36, 301-307 [DOI 10.1107/S002188980300150X]
Mixed valences in nanometric ferrites investigated by resonant powder
diffraction
J. Appl. Cryst. (2003). 36, 1182-1189 [DOI 10.1107/S0021889803013955]
Strategies for solving neighboring-element problems: a case study using
resonant X-ray diffraction and pulsed neutron diffraction to examine
Sr8Ga16Ge30
Vincent
--
Vincent Favre-Nicolin
Université Joseph Fourier
http://v.favrenicolin.free.fr
ObjCryst & Fox : http://objcryst.sourceforge.net
