Structural studies of five layer Aurivillius oxides: A2Bi4Ti5O18 (A=Ca, Sr, Ba and Pb) |
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Authors: | Ismunandar T. Kamiyama Q. Zhou Y. Kubota |
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Affiliation: | a Institute of Materials Structure Science, High Energy Accelerator Research Organization, Tsukuba 305-0801, Japan b Departemen Kimia, Institut Teknologi Bandung, Jl. Ganesa 10 Bandung, 40132, Indonesia c The Centre for Heavy Metals Research, School of Chemistry, The University of Sydney, New South Wales 2006, Sydney, Australia d Department of Environmental Sciences, Faculty of Science Osaka Women's University Daisen-cho 2-1, Sakai, Osaka 590-0035, Japan e Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto, Mikazuki-cho, Sayo-gun, Hyogo 67905198, Japan |
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Abstract: | The room temperature structures of the five layer Aurivillius phases A2Bi4Ti5O18 (A=Ca, Sr, Ba and Pb) have been refined from powder neutron diffraction data using the Rietveld method. The structures consist of [Bi2O2]2+ layers interleaved with perovskite-like [A2Bi2Ti5O16]2− blocks. The structures were refined in the orthorhombic space group B2eb (SG. No. 41), Z=4, and the unit cell parameters of the oxides are a=5.4251(2), b=5.4034(1), c=48.486(1); a=5.4650(2), b=5.4625(3), c=48.852(1); a=5.4988(3), b=5.4980(4), c=50.352(1); a=5.4701(2), b=5.4577(2), c=49.643(1) for A=Ca, Sr, Ba and Pb, respectively. The structural features of the compounds were found similar to n=2-4 layers bismuth oxides. The strain caused by mismatch of cell parameter requirements for the [Bi2O2]2+ layers and perovskite-like [A2Bi2Ti5O16]2− blocks were relieved by tilting of the TiO6 octahedra. Variable temperature synchrotron X-ray studies for Ca and Pb compounds showed that the orthorhombic structure persisted up to 675 and 475 K, respectively. Raman spectra of the compounds are also presented. |
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Keywords: | Aurivillius phase Neutron powder diffraction Synchrotron X-ray diffraction CaBi4Ti5O18 SrBi4Ti5O18 BaBi4Ti5O18 PbBi4Ti5O18 |
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