Contribution à l'étude structurale de la wüstite solide de haute température
Abstract
The structure of wüstite Fe _{1 z}O is studied by neutron diffraction on one polycrystalline sample under equilibrium conditions at high temperature. The mean isotrope temperature factor B is expressed as a sum of two parts, B_{Th} and B_{St}, which vary linearly with a single parameter, respectively temperature and z. A classification is established for clusters ( {m}/{n}) settled from m vacancies in octahedral sites and n Fe ^{III} ions in interstitial sites. Sixteen values have been experimentally determined for the vacancies to interstitials ratio ϱ = {(z + t)}/{t} = {m}/{n}. A constant value of ϱ, which is lower than 3, is observed. This result characterizes the shortrange order. It eliminates several possibilities of clusters like those obeying the relation ϱ = {(1 + 3n)}/{n}. Other clusters, namely ( {16}/{6}) or ( {40}/{14}), might agree. The ( {8}/{3}) and ( {9}/{4}) clusters obtained from ( {4}/{1}) clusters joined by an edge would be the more likely. An analysis of diffuse scattering eliminates the hypothesis of large domains with inverse spinel structure. The structural differences between the three varieties W_{1}, W_{2} and W_{3} would not be found in a structural change of clusters.
 Publication:

Journal of Solid State Chemistry France
 Pub Date:
 July 1979
 DOI:
 10.1016/00224596(79)902111
 Bibcode:
 1979JSSCh..29...81G