Structure and microstructure of the high pressure synthesised misfit layer compound [Sr{sub 2}O{sub 2}][CrO{sub 2}]{sub 1.85}

• Published in: Journal of solid state chemistry 2008-08, Vol.181 (8)
• Main Authors: Castillo-Martinez, E., Schoenleber, A., Smaalen, S. van, Arevalo-Lopez, A.M., Alario-Franco, M.A.
• Format: Article
• Language: English
• Subjects: ANISOTROPY; CHROMIUM OXIDES; CRYSTAL DEFECTS; ELECTRON DIFFRACTION; INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; LATTICE PARAMETERS; LAYERS; LEAD SULFIDES; MICROSTRUCTURE; MONOCRYSTALS; ORTHORHOMBIC LATTICES; STRONTIUM OXIDES; TITANIUM SULFIDES; TRANSMISSION ELECTRON MICROSCOPY; X-RAY DIFFRACTION
• ISSN: 0022-4596; 1095-726X
• DOI: 10.1016/j.jssc.2008.03.033

The strontium chromium oxide [Sr{sub 2}O{sub 2}][CrO{sub 2}]{sub 1.85} misfit layer compound has been synthesised at high-pressure and high-temperature conditions. Electron diffraction patterns and high-resolution transmission electron microscopy images along [001] show the misfit character of the different layers composing the structure with a supercell along the incommensurate parameter b{approx}7b{sub 1}{approx}13b{sub 2}. The modulated crystal structure has been refined within the superspace formalism against single-crystal X-ray diffraction data, employing the (3+1)-dimensional superspace group C'nmb(0{sigma}{sub 2}0)0 0 s. The compound has a composite structure with lattice parameters a{sub 1}=5.182(1) A, b{sub 1}=5.411(1) A, c{sub 1}=18.194(3) A for the first, SrO, subsystem and the same a and c, but with b{sub 2}=2.925(1) A for the second, CrO{sub 2}, subsystem. The layer stacking is similar to that of orthorhombic PbS(TiS{sub 2}){sub 1.18}, but with a much stronger intersubsytem bonding in the case of the oxide. The intersubsystem lattice mismatch is mainly handled by displacement modulations of the Sr atoms, correlated with modulations of the valence, the coordination and the anisotropic displacement parameters. - Graphical abstract: A strontium chromium oxide, [Sr{sub 2}O{sub 2}][CrO{sub 2}]{sub 1.85}, with an orthorhombic misfit layer structure has been synthesised under high pressure. Mainly modulations on the Sr position, ADPs and coordination save the subsystems lattice mismatch.