Mixed crystal formation and structural studies in the mullite-type system Bi2Fe4O9–Bi2Mn4O10

• Published in: Journal of solid state chemistry Vol. 185; pp. 62 - 71
• Main Authors: Kann, Zachary R., Auletta, Jeffrey T., Hearn, Eric W., Weber, Sven-U., Becker, Klaus D., Schneider, Hartmut, Lufaso, Michael W.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Inc 01.01.2012; Elsevier
• Subjects: Condensed matter: structure, mechanical and thermal properties; Diffraction; Disorders; Exact sciences and technology; Inorganic compounds; Iron; Mixed crystals; Mossbauer spectroscopy; Mullite; Mössbauer; Oxide; Physics; Pyramids; Solid solution; Solid state; Structure of solids and liquids; crystallography; Structure of specific crystalline solids; X-rays; Oxide; Mössbauer; Mullite; Solid solution; Rietveld method; Moessbauer effect; Space groups; Atomic position; Moessbauer spectroscopy; Beryllium additions; Iron; XRD; Charge compensation; Solid state; Dual phase structure; Ion substitution; Solid solutions; Transition elements; Orthorhombic lattices; Crystallographic site; Crystal structure
• ISSN: 0022-4596; 1095-726X
• DOI: 10.1016/j.jssc.2011.10.046

The limits of metal cation substitution and distribution in the sequence Bi2Fe4O9–Bi2Mn4O10 have been investigated by solid state synthesis, X-ray powder diffraction, and Mössbauer spectroscopy. Rietveld refinements conducted for the entire range along the join indicate the structures are orthorhombic with space group Pbam, with partial transition-metal site disorder confirmed and detailed by Mössbauer spectroscopy. Single-phase regions are found near each end-member and a two-phase region is observed at intermediate compositions, extending from about x=1 to 3, according to the general formula of the mixed crystals Bi2Fe4−xMnxO10−δ. An incorporation of Mn at octahedral sites replacing Fe is taken into account for the Bi2Fe4O9-related side of the system. Charge compensation is believed to be effected by addition of O, which gives rise to the formation of FeO5 pyramids. At the Bi2Mn4O10-related side of the system, substitution of pyramidal Mn3+ by Fe3+ is envisaged. Single-phase regions are found near each end-member and a two-phase region is observed at intermediate compositions, extending from about x=1 to 3, according to the general formula of the mixed crystals Bi2Fe4−xMnxO10−δ. [Display omitted] ► Mixed crystals of the mullite-type Bi2Fe4−xMnxO10−δ were synthesized. ► Two single-phase regions and an intermediate two-phase region were found. ► Site substitution was examined via X-ray diffraction and Mössbauer spectroscopy. ► Charge compensation models were examined for intermediate compositions.