Intermediate range order in Fe,Al silicate network glasses: a neutron diffraction and EPSR modeling investigation - Condensed Matter > Materials ScienceReport as inadecuate




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Abstract: The local structural environment and the spatial distribution of iron andaluminum ions in sodosilicate glasses with composition NaFexAl1-xSi2O6 x = 1,0.8, 0.5 and 0 is studied by high-resolution neutron diffraction combined withstructural modeling using the Empirical Potential Structure Refinement EPSRcode. This work gives evidence of differences in the structural behavior ofAl3+ and Fe3+, which are both often considered to act as network formers incharge-balanced compositions. The short-range environment and the structuralrole of the two cations are not composition dependent, and hence the structureof intermediate glasses can then be seen as a mixture of the structures of thetwo end-members. All Al3+ is 4-coordinated for a distanced4Al3+-O=1.76$\pm$0.01{\AA}. The high-resolution neutron data allowsdeciphering between two populations of Fe. The majority of Fe3+ is4-coordinated d4Fe3+-O=1.87$\pm$0.01{\AA} while the remaining Fe3+ and allFe2+ ~12% of total Fe are 5-coordinated d5Fe-O=2.01$\pm$0.01{\AA}. BothAlO4 and FeO4 are randomly distributed and connected with the silicate networkin which they share corners with SiO4 tetrahedra, in agreement with anetwork-forming role of those species. On the contrary FeO5 tends to formclusters and to share edges with each other. 5-coordinated Fe is interpreted asnetwork modifier and it turns out that, even if this coordination number israre in crystals, it is more common in glasses in which they can have a keyrole on physical properties.



Author: Coralie Weigel IMPMC, Laurent Cormier IMPMC, Georges Calas IMPMC, Laurence Galoisy IMPMC, Daniel Bowron

Source: https://arxiv.org/



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