Perovskite tungsten bronze-type crystals of LixWO3 grown by chemical vapour transport and their characterisation

Rüscher, Claus H.; Dey, Kalpana R.; Debnath, Tapas; Horn, I.; Glaum, Robert; Hussain, Altaf

doi:10.1016/j.jssc.2007.10.033

Cited by 12 publications

(7 citation statements)

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“…The main signature of optical conductivity for intermediate-to-strong EP coupling in the adiabatic regime (Fehske and Trugman , 2007) is that the spectrum is strongly asymmetric, which is also characteristic for rather large polarons (III.F), as observed in cuprate superconductors (Mihailović et al , 1990), perovskite tungsten bronzes (Ruscher et al , 2008) and many other doped insulators. Importantly, the weaker decay at the high-energy side meets the experimental findings for many polaronic materials like TiO 2 (Kudinov et al , 1969) even better than standard small-polaron theory.…”

Section: B Optical Conductivitymentioning

confidence: 96%

“…More recent ED, VED and a kernel polynomial method (KPM) (for a review of KPM see Weiße et al (2006)) allowed for numerical calculations of lattice polaron properties in the Holstein model in the whole parameter range on fairly large systems (Barisic 2004, El Shawish et al 2003, Schubert et al 2005. The main signature of optical conductivity for intermediate-to-strong EP coupling in the adiabatic regime (Fehske and Trugman 2007) is that the spectrum is strongly asymmetric, which is also characteristic for rather large polarons (section 3.6), as observed in cuprate superconductors (Mihailović 1990), perovskite tungsten bronzes (Ruscher et al 2008) and many other doped insulators. Importantly, the weaker decay at the high-energy side meets the experimental findings for many polaronic materials likesuch as TiO 2 (Kudinov et al 1969) even better than standard small-polaron theory.…”

Section: Optical Conductivitymentioning

confidence: 99%

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Fröhlich polaron and bipolaron: recent developments

2009

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It is remarkable how the Fröhlich polaron, one of the simplest examples of a Quantum Field Theoretical problem, as it basically consists of a single fermion interacting with a scalar Bose field of ion displacements, has resisted full analytical or numerical solution at all coupling since ∼ 1950, when its Hamiltonian was first written. The field has been a testing ground for analytical, semi-analytical, and numerical techniques, such as path integrals, strong-coupling perturbation expansion, advanced variational, exact diagonalisation (ED), and quantum Monte Carlo (QMC) techniques. This article reviews recent developments in the field of continuum and discrete (lattice) Fröhlich (bi)polarons starting with the basics and covering a number of active directions of research. * Electronic address: jozef.devreese@ua.ac.be † Electronic address: a.s.alexandrov@lboro.ac.uk

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Section: B Optical Conductivitymentioning

confidence: 96%

Section: Optical Conductivitymentioning

confidence: 99%

Fröhlich polaron and bipolaron: recent developments

2009

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“…The simplest form of tungsten bronze structure is formed when the cuboctahedral perovskite A site of rhenium oxide structured WO 3 , Figure a, is being filled by a cation, and the structure is called perovskite tungsten bronze (PTB) with a composition of A x WO 3 . Examples include Li and Na ,, when Li content is below 0.5 and Na content is either small ( x < 0.10) or large (0.41 < x < 0.95). Also, protons enter easily to form a bronze structure.…”

Section: Introductionmentioning

confidence: 99%

Structural Properties of Pure and Nickel-Modified Nanocrystalline Tungsten Trioxide

et al. 2012

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The particle size and nickel-doping effect on pure nanocrystalline WO 3 powders are addressed through X-ray diffraction, Raman spectroscopy, and transmission electron microscopy. A brief review of different structure types of tungsten oxides is also given. Stable and metastable crystallographic structures, resulting from oxygen deficiency, metal doping, or low-temperature synthesis, are discussed. The focus is put on the topology of the structures and notably on the structural features allowing ion intercalation. Small particle size WO 3 powders were synthesized by two different wet chemical methods to determine the impact of particle size on the crystal symmetry: in the first method, a freeze-drying technique was utilized, whereas the second technique was based on a reverse micelle method. Both methods yielded similar powders with an average size of approximately 10 nm. However, the first method yielded single-phase rhenium oxide structured particles, whereas the latter method produced a mixture of hexagonal tungsten bronze and rhenium oxide structures. In the case of single-phase rhenium oxide structure powders, the crystal symmetry was found to increase from monoclinic P2 1 /n to orthorhombic Pbcn when particle size decreased below 20 nm. The effect of nickel doping (≈1 wt %) and synthesis conditions on WO 3 powders were studied. Ni-doped WO 3 was spatially inhomogeneous: the most abundant phase was monoclinic WO 3 , whereas the minority phase was either perovskite tungsten bronze (annealing temperature below 500°C) or wolframite (annealing temperature 500°C or higher) showing that annealing conditions are a way to selectively produce different crystal structures. The wolframite and tungsten bronze structures are very different with different applications. The results are discussed in the context of thin film synthesis and sensor applications. ■ INTRODUCTIONThe crystal symmetry of tungsten trioxide (WO 3 ) is very prone to temperature, stoichiometry, and particle size. The changes are accompanied by corresponding changes in physical properties, such as electrical conductivity and color, which form a basis for many industrially important applications, including gas sensors and smart windows. For applications in mind, one practical approach is to consider how open the structure is. Structures formed at low temperatures tend to have channels and flexibility to host intercalating ions, whereas structures formed at high pressure and temperature are characteristically densely packed. The synthetization method, such as thin film deposition, can be optimized to yield the desired crystal structure for the need.Many applications require small particle size powders or thin films, which are typically achieved through low-temperature synthesis. This in turn often results in a formation of metastable phases. Besides various distorted WO 3 structures, the changes in composition or stoichiometry may result in larger structural changes, such as the formation of tungsten bronze structures or structures derived from WO 3 by crys...

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“…Tungsten bronzes have received a lot of attention due to their electrochromic, photochromic, gasochromic, and superconducting properties [7][8][9][10][11]. Tungsten bronzes M x WO 3 with dopant ions such as Na, K, Rb, Cs, and other alkali metals [12,13] have been found to have the best optical and electrical properties.…”

Section: Accepted Manuscriptmentioning

confidence: 99%