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Synthesis and Structural Analysis of ϵ‐Fe 2 O 3
Author(s) -
Kelm Klemens,
Mader Werner
Publication year - 2005
Publication title -
zeitschrift für anorganische und allgemeine chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.354
H-Index - 66
eISSN - 1521-3749
pISSN - 0044-2313
DOI - 10.1002/zaac.200500283
Subject(s) - isostructural , crystallography , orthorhombic crystal system , nontronite , powder diffraction , crystal structure , materials science , rietveld refinement , electron diffraction , chemistry , diffraction , mineralogy , clay minerals , physics , optics
Powder material of ϵ‐Fe 2 O 3 was obtained by thermal decomposition of the clay mineral nontronite and subsequent isolation of the ferric oxide by leaching the silicate phases. Additionally, crystals of ϵ‐Fe 2 O 3 were grown as precipitates by internal oxidation of a Pd 96 Fe 4 alloy. Analysis of the precipitate crystals by electron diffraction yields an orthorhombic crystal system and space group Pna 2 1 ab initio . X‐ray diffraction data of the powder containing small amounts of Al substituting Fe were refined by the Rietveld method. The refinement yields lattice parameters a = 507.15 pm, b = 873.59 pm and c = 941.78 pm, and atom positions. ϵ‐Fe 2 O 3 is isostructural with κ‐Al 2 O 3 , AlFeO 3 , and GaFeO 3 having an anion stacking sequence /ABAC/, and 1/4 of the cations in tetrahedral co‐ordination. Some strongly distorted FeO 6 octahedrons with one large Fe‐O distance, which may be considered as a 5+1 co‐ordination, appear to be characteristic for ϵ‐Fe 2 O 3 . The structure shows elements known from silicates and oxyhydroxides of iron, respectively.