Acta Crystallographica Section C

Crystal Structure Communications

Volume 68, Part 12 (December 2012)


inorganic compounds



Acta Cryst. (2012). C68, i83-i85    [ doi:10.1107/S0108270112043016 ]

Fe6.67(PO4)5.35(HPO4)0.65 and Fe6.23(PO4)4.45(HPO4)1.55: two new mixed-valence iron phosphates

F. Dal Bo and F. Hatert

Abstract: Two new mixed-valence iron phosphates, namely heptairon pentaphosphate hydrogen phosphate, Fe6.67(PO4)5.35(HPO4)0.65, and heptairon tetraphosphate bis(hydrogen phosphate), Fe6.23(PO4)4.45(HPO4)1.55, have been synthesized hydrothermally at 973 K and 0.1 GPa. The structures are similar to that of FeII3FeIII4(PO4)6 and are characterized by infinite chains of Fe polyhedra parallel to the [101] direction. These chains are formed by the Fe1O6 and Fe2O6 octahedra, alternating with the Fe4O5 distorted pentagonal bipyramids, according to the stacking sequence ...Fe1-Fe1-Fe4-Fe2-Fe2.... The Fe3O6 octahedra and PO4 tetrahedra connect the chains together. FeII is localized on the Fe3 and Fe4 sites, whereas FeIII is found in the Fe1 and Fe2 sites, according to bond-valence calculations. Refined site occupancies indicate the presence of vacancies on the Fe4 site, explained by the substitution mechanism FeII + 2(PO43-) = vacancies + 2(HPO42-).

Formula: Fe6.67(PO4)5.35(HPO4)0.65 and Fe6.23(PO4)4.45(HPO4)1.55


hkldisplay filedownload file

Structure factor file (CIF format) (118.1 kbytes)
[ doi:10.1107/S0108270112043016/fn3113H339sup2.hkl ]
Contains datablock H339


hkldisplay filedownload file

Structure factor file (CIF format) (116.8 kbytes)
[ doi:10.1107/S0108270112043016/fn3113H347sup3.hkl ]
Contains datablock H347


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