Nonstoichiometric, rutile-type, solid solutions in the (FeF2)-F-II-(FeOF)-O-III system

Solid solutions of the form (Fe(1-x)FexIII)-Fe-II OxF2-x have been synthesi zed by the reaction of FeF2 with FeOF in a sealed platinum tube at 850 degr eesC. Careful electron probe microanalysis and X-ray powder diffraction hav e determined the existence of two distinct solid solution regions extending from 0 less than or equal to x less than or equal to 0.08 at the (FeF2)-F- II end and from 0.71 less than or equal to x less than or equal to 1 at the (FeOF)-O-III end with a miscibility gap from 0.08 less than or equal to x less than or equal to 0.71. Electron diffraction experiments have revealed the presence of characteristic diffuse intensity distributions for samples within either solid solution region. Plausible explanations for the observe d diffraction phenomena, based upon crystal chemical and bond length-bond v alence arguments, are provided. (C) 2001 Academic Press.