Ferroelectric Tungsten Trioxide

Woodward, P.M.; Sleight, A.W.; Vogt, Thomas

doi:10.1006/jssc.1997.7268

Cited by 192 publications

(139 citation statements)

References 26 publications

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“…In particular, higher E g for e-WO 3 relative to d-WO 3 has been reported. 24 D. Raman spectroscopy Figure 5 shows Raman spectra of nano-WO 3 films prepared at different P tot . Peaks 6 and 7 are typical for crystalline WO 3 and are common to several WO 3 phases.…”

Section: Resultsmentioning

confidence: 99%

“…WO 3 exists in several phases, which differ with respect to each other by the tilting and displacement of the atoms in the octahedral building blocks that comprise the WO 3 structure. The thermodynamically favored phase is reported to change with temperature (at standard pressure) for crystalline bulk WO 3 as follows: monoclinic Pc (e-WO 3 ) up to 230 K, triclinic P1 (d-WO 3 ) 230-300 K, monoclinic P2 1 /n (c-WO 3 ) 300-623 K, orthorhombic Pnma (b-WO 3 ) 623-1020 K, tetragonal P4/ncc (a-WO 3 ) 1020-1171 K, and, finally, tetragonal P4/nmm (a-WO 3 ) to the melting point at 1700 K. [22][23][24][25][26] The stability of each of these phases is modified by preparation procedures. For nanocrystalline thin films, the detailed growth conditions are critical, including type of substrate, temperature, and pressure.…”

Section: Introductionmentioning

confidence: 99%

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Structural and optical properties of visible active photocatalytic WO₃ thin films prepared by reactive dc magnetron sputtering

2012

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Nanostructured tungsten trioxide films were prepared by reactive dc magnetron sputtering at different working pressures P tot 5 1-4 Pa. The films were characterized by scanning electron microscopy, x-ray diffraction, Rutherford backscattering spectroscopy, Raman spectroscopy, and ultraviolet-visible spectrophotometry. The films were found to exhibit predominantly monoclinic structures and have similar band gap, E g % 2.8 eV, with a pronounced Urbach tail extending down to 2.5 eV. At low P tot , strained film structures formed, which were slightly reduced and showed polaron absorption in the near-infrared region. The photodegradation rate of stearic acid was found to correlate with the stoichiometry and polaron absorption. This is explained by a recombination mechanism, whereby photoexcited electron-hole pairs recombine with polaron states in the band gap. The quantum yield decreased by 50% for photon energies close to E g due to photoexcitations to band gap states lying below the O 2 affinity level.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Structural and optical properties of visible active photocatalytic WO₃ thin films prepared by reactive dc magnetron sputtering

2012

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“…The center of the cube is empty, and hence the structure is easily distorted and tilted upon heating or cooling, with concomitant symmetry lowering. Five different crystal structures of WO 3 have been observed below 1000 K. [27][28][29] At room temperature, the most stable structure is γ-monoclinic with the following lattice parameters: a 1 = 7.306 Å, b 1 = 7.540 Å, c 1 = 7.692 Å, and β = 90.88 • ; note that this unit cell contains eight WO 3 formula units. LSAO substrate has a tetragonal structure with an in-plane lattice constant a = 3.754 Å.…”

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confidence: 99%

Epitaxial growth of high quality WO3 thin films

et al. 2015

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We have grown epitaxial WO3 films on various single-crystal substrates using radio frequency magnetron sputtering. While pronounced surface roughness is observed in films grown on LaSrAlO4 substrates, films grown on Y AlO3 substrates show atomically flat surfaces, as demonstrated by atomic force microscopy and X-ray diffraction (XRD) measurements. The crystalline structure has been confirmed to be monoclinic by symmetric and skew-symmetric XRD. The dependence of the growth modes and the surface morphology on the lattice mismatch are discussed.

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“…Nevertheless it has been widely studied in many precious theoretical calculations for its simplicity. 17,22,23 All our calculations in this work deal with the cubic phase WO 3 and its surfaces.…”

Section: Methodsmentioning

confidence: 99%

Chemical Stability of 2D-Nanostructured WO₃ in Hydrogen Sensing Under Varied Operation Temperature

Yang

Tian

Zhang

et al. 2016

NANO

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Nanostructured metal oxide-based resistive-type gas sensors are of high research interest. Chemical stability is the most critical issue due to the surface electron species and density. In the present paper, 2D-nanostructured WO 3 was prepared and characterized, and a WO 3 -based sensor was fabricated and analyzed. The results showed that the synthesized WO 3 material exhibited nanosheet structure, and during hydrogen sensing testing, the current baseline shifted with various tendencies, even completely opposite directions under di®erent operation temperatures. The chemistry analysis results indicated that water molecule and hydroxyl group were formed under low operation temperature but further oxidation occurred at higher temperatures. The adsorption of H 2 on oxygen terminated WO 3 (0 0 1) surfaces by density functional theory (DFT) method indicated that a water molecule formed by adsorption of a hydrogen molecule at the O site with the most thermodynamically stable state, and two surface hydroxyl groups formed by dissociative adsorption with a thermodynamically less stable state. The water molecule and surface hydroxyl groups increased the conductivity of the WO 3¯l m while that was decreased as the oxidation occurred.

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Ferroelectric Tungsten Trioxide

Cited by 192 publications

References 26 publications

Structural and optical properties of visible active photocatalytic WO₃ thin films prepared by reactive dc magnetron sputtering

Structural and optical properties of visible active photocatalytic WO₃ thin films prepared by reactive dc magnetron sputtering

Epitaxial growth of high quality WO3 thin films

Chemical Stability of 2D-Nanostructured WO₃ in Hydrogen Sensing Under Varied Operation Temperature

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Ferroelectric Tungsten Trioxide

Cited by 192 publications

References 26 publications

Structural and optical properties of visible active photocatalytic WO3 thin films prepared by reactive dc magnetron sputtering

Structural and optical properties of visible active photocatalytic WO3 thin films prepared by reactive dc magnetron sputtering

Epitaxial growth of high quality WO3 thin films

Chemical Stability of 2D-Nanostructured WO3 in Hydrogen Sensing Under Varied Operation Temperature

Contact Info

Product

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Structural and optical properties of visible active photocatalytic WO₃ thin films prepared by reactive dc magnetron sputtering

Structural and optical properties of visible active photocatalytic WO₃ thin films prepared by reactive dc magnetron sputtering

Chemical Stability of 2D-Nanostructured WO₃ in Hydrogen Sensing Under Varied Operation Temperature