Perovskite tungsten bronze-type crystals of Li{sub x}WO{sub 3} grown by chemical vapour transport and their characterisation

Journal Article · Tue Jan 15 00:00:00 EST 2008 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/j.jssc.2007.10.033· OSTI ID:21043865

Dey, Kalpana R ^[1]; Debnath, Tapas; Horn, Ingo ^[2]; Glaum, Robert ^[3]; Hussain, Altaf ^[4]

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1. School of Environmental Science and Management, Independent University, Dhaka 1212 (Bangladesh)
2. Institut fuer Mineralogie und Zentrum fuer Festkoerperchemie und neue Materialien (ZFM), Leibniz Universitaet Hannover, Welfengarten 1, 30167 Hannover (Germany)
3. Institut fuer Anorganische Chemie, Universitaet Bonn, Gerhard-Domagk-Strasse 1, 53121 Bonn (Germany)
4. Department of Chemistry, University of Dhaka, Dhaka 1000 (Bangladesh)

Crystals of Li{sub x}WO{sub 3} with nominal compositions, x=0.1, 0.25, 0.3, 0.35, 0.4 and 0.45 were grown by chemical vapour transport method using HgCl{sub 2} as transporting agent. A complete transport was achieved with a temperature gradient T{sub 1}/T{sub 2}=800/700 deg. C revealing bluish-black crystals of sizes up to a few 10th of a millimeter. X-ray powder diffraction and infrared (IR) absorption spectra show Perovskite tungsten bronze of cubic symmetry (PTB{sub c}) for x=0.45 and 0.4, mixed phase of PTB{sub c} and Perovskite tungsten bronze of tetragonal symmetry (PTB{sub t}) for x=0.35, 0.3 and 0.25 and of PTB{sub t} and Perovskite tungsten bronze of orthorhombic symmetry (PTB{sub o}) for x=0.1. The structure of PTB{sub t} is explained by the off centring of the W-ions along c and tilting of the WO{sub 6} octahedra around c. Crystal slices of mixed phase (i.e. PTB{sub c} and PTB{sub t}) reveal bright and dark areas on a sub-millimeter scale which are separated by sharp interfaces. Laser ablation inductively coupled plasma optical emission (LA ICP OES) analysis on small spot sizes show the separation into Li contents of x=0.18 (bright areas) and x=0.38 (dark areas) as threshold compositions of PTB{sub t} and PTB{sub c}, respectively. Polarized reflectivity using a microscope technique in the bright area of the crystals indicates strong anisotropic absorption effects with maximum between 1000 and 6000 cm{sup -1}, which are related to optical excitations of polarons. Crystals of composition x=0.4 and 0.45 appear optically homogeneous and show an effective 'free carrier-type plasma frequency' (w{sub p}) of about 12,900 and 13,700 cm{sup -1}, respectively. - Graphical abstract: Optical microscope image (reflection mode) of Li{sub x}WO{sub 3} crystals of nominal composition x=0.35. The separation into PTB{sub cubic} (dark areas) and PTB{sub tetragonal} (bright areas) were used to determine the miscibility gap and optical properties.

• OSTI ID: 21043865
• Journal Information: Journal of Solid State Chemistry, Vol. 181, Issue 1; Other Information: DOI: 10.1016/j.jssc.2007.10.033; PII: S0022-4596(07)00445-8; Copyright (c) 2007 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); ISSN 0022-4596
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ABSORPTION SPECTRA
CHEMICAL VAPOR DEPOSITION
CRYSTAL GROWTH
CRYSTALS
EMISSION SPECTROSCOPY
LANGMUIR FREQUENCY
LITHIUM COMPOUNDS
MERCURY CHLORIDES
OPTICAL MICROSCOPES
ORTHORHOMBIC LATTICES
OXIDES
PEROVSKITE
POLARONS
REFLECTIVITY
SYMMETRY
TEMPERATURE GRADIENTS
TUNGSTEN BRONZE
TUNGSTEN COMPOUNDS
TUNGSTEN IONS
X-RAY DIFFRACTION