Nonstoichiometric, rutile-type, solid solutions in the FeIIF2-FeIIIOF system

Solid solutions of the form (Fe(1-x)FexIII)-Fe-II OxF2-x have been synthesized by the reaction of FeF2 with FeOF in a sealed platinum tube at 850 degreesC. Careful electron probe microanalysis and X-ray powder diffraction have 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 observed diffraction phenomena, based upon crystal chemical and bond length-bond valence arguments, are provided. (C) 2001 Academic Press.