Nanosize hexagonal tungsten oxide for gas sensing applications

Balázsi, Csaba; Wang, Lisheng; Zayim, Esra Ozkan; Szilágyi, Imre Miklós; Sedlačková, Katarína; Pfeifer, J.; Tóth, A.L.; Gouma, Pelagia‐Irene

doi:10.1016/j.jeurceramsoc.2007.09.001

Cited by 100 publications

(49 citation statements)

References 9 publications

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“…This peak was deconvoluted into two peaks centred at 775 cm -1 and 816 cm -1 . ElBatal [25] observed Raman shifts at 333 cm [31][32][33][34][35]. Analysing spot 1, the peaks at 110 cm -1 and 152 cm -1 suggest a WO 3 hydrate [22].…”

Section: Resultsmentioning

confidence: 99%

Electrical and optical properties of mixed phase tungsten trioxide films grown by laser pyrolysis

Govender

Mwakikunga

Machatine

et al. 2014

Phys. Status Solidi C

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Laser pyrolysis is a synthesis method used to produce thin films and nanomaterials of high quality and purity, by intersecting a laser beam with a chemical precursor. We have chosen laser pyrolysis to synthesize tungsten trioxide starting with tungsten ethoxide precursor. The film had a thickness that varied from 205 nm to 1 µm. Xray diffraction and Raman spectroscopy confirmed the presence of a mixture of hexagonal and tetragonal phase WO 3 in the synthesized film, and it was clear that annealing greatly influenced the phases and types of structures formed. I-V curves of the films showed n-type semiconducting behaviour, but the mixed phase appeared to cause a similar behaviour of dopants in a semiconductor. The refractive index decreased with increasing wavelength and gave values of up to 21 at low wavelengths. The average optical band gap was found to 3.6 eV from UV/Vis spectroscopy. Scanning Electron Microscopy (SEM) showed a mixture of nano-and microstructures and shapes formed after annealing. One of the grown nanostructures was nanorods, this isolated using FIB for possible applications such as an active sensing medium in gas sensors.

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Section: Resultsmentioning

confidence: 99%

Electrical and optical properties of mixed phase tungsten trioxide films grown by laser pyrolysis

Govender

Mwakikunga

Machatine

et al. 2014

Phys. Status Solidi C

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“…hexagonal WO 3 , are very suitable for detection of ammonia gas, the reason being the reaction of lattice oxygen of the metal oxide with the measured gas, and easy mechanisms for adjusting the unstoichiometric metal to oxygen ratio [27,28]. As was already mentioned in the introduction, also V 2 O 5 and V 7 O 16 are formed of layered structures and thus should be considered as highly potential ammonia sensing materials.…”

Section: Ammonia Gas Sensing Propertiesmentioning

confidence: 99%

Synthesis of nanostructured solid-state phases of V7O16 and V2O5 compounds for ppb-level detection of ammonia

Huotari

Lappalainen

Eriksson

et al. 2016

Journal of Alloys and Compounds

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Solid state phase of V 7 O 16 with separate V 2 O 5 phase were fabricated by pulsed laser deposition. The crystal structure and symmetry of the deposited films were studied with X-ray diffraction and Raman spectroscopy, respectively. Rietveld analysis was performed to the X-ray diffraction measurement results. The surface potentials and morphologies of the films were studied with atomic force microscopy, and microstructure of the thin films was analyzed by transmission electron microscopy. Raman spectroscopy and Rietveld refinement results confirmed that the thin-film crystal structures varied between orthorombic V 2 O 5 phase and another phase, triclinic V 7 O 16 , previously found only in the walls of vanadium oxide nanotubes (VO x -NT), bound together with organic amine. We have earlier presented the first results of stable and pure metal-oxide solid-state phase of V 7 O 16 manufactured from ceramic V 2 O 5 target. Here we show more detailed study of these structures. The microstructure studies showed a variation on the porosity of the films according to crystal structures and also some fiber-like nanostructures were found in the films. The surface morphology depended strongly on the crystal structure and the surface potential studies showed ~ 50 meV difference in the work function values between the phases. Compounds were found to be extremely sensitive towards ammonia, NH 3 , down to ~ 40 ppb concentrations, and have shown to 2 have the stability and selectivity to control the Selective Catalytic Reduction process, where nitrogen oxides are reduced by ammonia in, e.g. diesel exhausts.

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“…One of their major applications is that tungsten oxides, metal tungstates, tungsten carbides or tungsten metal can be prepared from them, all of which are significant for various industries. Tungsten oxides can be used as catalysts [2][3][4][5], photocatalysts [6][7][8][9][10], gas sensors [11][12][13][14][15][16][17][18], chromogenic materials [19][20][21]; metal tungstates can be used among others as catalysts [22], pigments [23,24]; tungsten carbides are the hard components in cutting, drilling, tools [25][26][27] and they are also used as catalysts [28,29]; while tungsten metal is a key element in lighting industry [1,[30][31][32][33][34].…”

Section: Introductionmentioning

confidence: 99%

Structure and thermal decomposition of ammonium metatungstate

Hunyadi

Sajó

Szilágyi

2013

J Therm Anal Calorim

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The structure, morphology of ammonium metatungstate (AMT), (NH 4 formed between 380-500 °C, (iv) which then transformed into the more stable m-WO 3 between 500-600 °C. As a difference in air, the as-formed NH 3 ignited with an exothermic heat effect, and nitrous oxides formed as combustion products. The thermal behavior of AMT was similar to ammonium paratungstate (APT), (NH 4 ) 10 [H 2 W 12 O 42 ]•4H 2 O, the only main difference being the lack of dry NH 3 evolution between 170-240 °C in the case of AMT.)

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Nanosize hexagonal tungsten oxide for gas sensing applications

Cited by 100 publications

References 9 publications

Electrical and optical properties of mixed phase tungsten trioxide films grown by laser pyrolysis

Electrical and optical properties of mixed phase tungsten trioxide films grown by laser pyrolysis

Synthesis of nanostructured solid-state phases of V7O16 and V2O5 compounds for ppb-level detection of ammonia

Structure and thermal decomposition of ammonium metatungstate

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