Structure refinements of members in the brownmillerite solid solution series Ca{sub 2}Al{sub x}(Fe{sub 0.5}Mn{sub 0.5}){sub 2-x}O{sub 5+{delta}} with 1/2{<=}x{<=}4/3
- Martin-Luther-Universitaet Halle Institut fuer Geowissenschaften Mineralogie/Geochemie Von Seckendorff-Platz 3 06120 Halle (Saale) (Germany)
- Universitaet Salzburg FB Materialforschung und Physik Abt. Mineralogie Hellbrunnerstrasse 34A-5020 Salzburg (Austria)
- Freie Universitaet Berlin FB Geowissenschaften Mineralogie/Petrologie Malteserstrasse 74-100, Haus N 12249 Berlin (Germany)
- Helmholtz-Zentrum-Berlin fuer Materialien und Energie, Hahn-Meitner-Platz 1, D-14109 Berlin (Germany)
Four different brownmillerite solid solutions Ca{sub 2}Al{sub x}(Fe{sub 0.5}Mn{sub 0.5}){sub 2-x}O{sub 5+{delta}} with 1/2{<=}x{<=}4/3 were synthesized by a solid oxide ceramic method. The phases crystallize either in a primitive centered orthorhombic cell with space group Pnma or in a body centered cell with space group I2mb dependent on the aluminum concentration present in the solid solution. Mn{sup 3+} ions occupy exclusively site 4a coordinated by six oxygen anions. Increasing Mn{sup 3+} concentrations cause a remarkable distortion of the octahedron and indirectly of the tetrahedron, resulting in twisted and tilted octahedral layers as well as buckled tetrahedral chains. The influences are discussed on the site 4a of trivalent manganese due to its Jahn-Teller activity, with regard to the occupation of octahedron and tetrahedron with different sized iron and aluminum ions. - Graphical Abstract: The coupled substitution Fe{sup 3+}>Mn{sup 3+}+Fe{sup 3+} <=>2 Al{sup 3+} in brownmillerite phases (Ca{sub 2}(Fe{sub 0.5}Mn{sub 0.5}){sub 2-x}Al{sub x}O{sub 5+{delta}}) changes predominantly their structural properties, which is essential for the hydration performance of the calcium aluminate cement, where brownmillerites occur as clinker phases. Highlights: Black-Right-Pointing-Pointer We present structural data of four Ca-Al-Fe-Mn-brownmillerites. Black-Right-Pointing-Pointer Mn{sup 3+}-ions occupy exclusively the octahedrally coordinated site 0,0,0. Black-Right-Pointing-Pointer Bonds and angles of the octahedrally coordinated site are distorted strongly. Black-Right-Pointing-Pointer Mn{sup 3+}-ions influence indirectly the shape of the tetrahedron. Black-Right-Pointing-Pointer Mn{sup 3+}-ions stabilize Pnma instead of I2mb in Ca-Al-Fe-Mn-brownmillerites.
- OSTI ID:
- 22131208
- Journal Information:
- Journal of Solid State Chemistry, Journal Name: Journal of Solid State Chemistry Vol. 197; ISSN 0022-4596; ISSN JSSCBI
- Country of Publication:
- United States
- Language:
- English
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