Preparation, structural and optical characterization of BaWO4 and PbWO4 thin films prepared by a chemical route

Pontes, F. M.; Maurera, M. A. M. A.; Souza, A. G.; Longo, Elson; Leite, E. R.; Magnani, R.; Machado, Myrela O.; Pizani, P. S.; Varela, José Arana

doi:10.1016/s0955-2219(03)00099-2

Cited by 100 publications

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“…The slight increase in bandgap above 600 • C is attributed to the phase pure BWO, because WO 3 has the lower optical bandgap as compared with BWO. 7,18 The where T b and T c are transmittances before and after coloration, respectively. 19 The change in ∆OD as a function of wavelength is shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

“…The identified internal (927.03 -923.27, 705, 213 cm −1 ) and external (130 cm −1 ) modes for the BWO films deposited at 400 • C, 600 • C and 800 • C are in consistent with the earlier reports. 28,29 The obtained vibrational modes in Raman spectra of BWO films can be divided into two groups, internal and external. The internal vibrations correspond to the oscillations inside the [WO 4 ] −2 molecular group with an immovable mass center.…”

Section: Resultsmentioning

confidence: 99%

“…Nevertheless, there are very few studies available on BWO thin films and there is no report available on irreversible thermochromic nature of BWO films. Pontes et al 7 studied structural and optical properties of BWO films by prepared by chemical route. Dinesh et al 8,9 demonstrated the growth of crystalline BWO films at room temperature and reported structural and microstructure of these films.…”

Section: Introductionmentioning

confidence: 99%

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Irreversible thermochromic response of RF sputtered nanocrystalline BaWO4 films for smart window applications

Kumar

Pamu

2015

AIP Advances

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We report irreversible thermochromic behaviour of BaWO 4 (BWO) films for the first time. BWO films have been deposited at different substrate temperatures (RT, 200, 400, 600 and 800 • C) using RF magnetron sputtering in pure argon plasma. BWO films deposited at 800 • C exhibit crystalline nature. Also, BWO films deposited in the temperature range of 400 -600 • C exhibit WO 3 as a secondary phase and its weight percentage decreases with an increase in deposition temperature, whereas the films deposited at 800 • C exhibited pure tetragonal phase. FESEM images revealed that as the average particle sizes of the films are higher as compared with the thickness of the films and is explained based on Avrami type nucleation and growth. The transmittance of the films decreases with an increase in deposition temperature up to 600 • C and increases thereafter. Films deposited at 600 • C show ≤ 20% transmittance, looking at the films deposited at room temperature and 800 • C exhibits 90 and 70%, respectively. The refractive index and extinction coefficient of the films show profound dependence on crystallinity and packing density. The optical bandgap of BWO films increases significantly with an increase in O 2 % during the deposition. The optical bandgap of the BWO films deposited at different temperatures in pure argon plasma, are in the range of 3.7 to 3.94 eV whereas the films deposited at 600 • C under different O 2 plasma are in the range of 3.6 -4.5 eV. The formations of colour centres are associated with the oxygen vacancies, which are clearly seen from the optical bandgap studies. The observed irreversible thermochromic behaviour in BWO films is attributed to the presence of oxygen vacancies that arises due to the electrons trapped at oxygen vacancies causing an inter valence charge transfer of W 5+ to W 6+ and is confirmed through the change in the optical density (∆OD). Further, the Raman spectra are being used to quantify the presence of oxygen vacancies and the formation of pure BWO phase. The obtained optical responses of BWO films are promising for solar cell and smart window applications. C 2015 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License. [http://dx

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Irreversible thermochromic response of RF sputtered nanocrystalline BaWO4 films for smart window applications

Kumar

Pamu

2015

AIP Advances

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“…This solution was then first heat treated at 200 • C during 60 min to pyrolyse the organic material. To remove part of organic material the powder was de-agglomerated and carried at 300 • C for 2 h. The obtained powder was then heat treated in oven from 300 to 700 • C in air for 4 h. This polymeric precursor synthesis method is one of the numerous sol-gel routes commonly used and the advantages that it offers over other synthesis techniques are: low cost, good compositional homogeneity, high purity, and low processing temperatures [25,26]. The SWO powder was structurally characterized by X-ray diffraction (XRD) using CuKα radiation source with diffraction angle (2θ ) ranging between 5 and 75 • C. The diffraction patterns were recorded on a Siemens D5000 machine using a graphite monochromator.…”

Section: Methodsmentioning

confidence: 99%

Visible PL Phenomenon at Room Temperature in Disordered Structure of SrWO4 Powder

Anicete-Santos¹,

Lima²,

Orhan³

et al. 2006

J Computer-Aided Mater Des

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The SrWO 4 (SWO) powders were synthesized by the polymeric precursor method and annealed at different temperatures. The SWO structure was obtained by X-ray diffraction and the corresponding photoluminescence (PL) spectra was measured. The PL results reveal that the structural order-disorder degree in the SWO lattice influences in the PL emission intensity. Only the structurally order-disordered samples present broad and intense PL band in the visible range. To understand the origin of this phenomenon, we performed quantum-mechanical calculations with crystalline and order-disordered SWO periodic models. Their electronic structures were analyzed in terms of band structure. The appearance of localized levels in the band gap of the order-disordered structure was evidenced and is a favorable condition for the intense PL to occur.

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“…It is a promising material for crystalline nano-and picoseconds Raman lasers. A number of methods, including hydrothermal method, flux method and solid-state reaction [3]- [8], have been developed to generate tungstate materials. However, tough reaction conditions, such as highreaction temperature, long-reaction time or complex equipment, were applied in most this approaches [9].…”

Section: Introductionmentioning

confidence: 99%

Synthesis of Crystallized BaWO<sub>4</sub> Nanorods in a Microemulsion System

Zhang¹,

Zhu²,

Huang³

et al. 2017

ACES

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BaWO 4 nanorods have been successfully synthesized in w/o microemulsion system containing barium ions via a simple reaction between Ba 2+ andThe BaWO 4 Nanorods were characterized by XRD, TEM, and SEM, respectively. Results showed that the solvents composition-volume ratio of 4-dioxane and distilled water-played the key role in the formation of BaWO 4 Nanorods. Furthermore, the strong vibration at 925 cm −1 on its Raman spectrum indicated that the BaWO 4 nanorods is good at stimulating Raman scattering in transient and steady-state, making it as a promising candidate material for laser with self-raman conversion of radiation inside the active medium.

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Preparation, structural and optical characterization of BaWO4 and PbWO4 thin films prepared by a chemical route

Cited by 100 publications

References 15 publications

Irreversible thermochromic response of RF sputtered nanocrystalline BaWO4 films for smart window applications

Irreversible thermochromic response of RF sputtered nanocrystalline BaWO4 films for smart window applications

Visible PL Phenomenon at Room Temperature in Disordered Structure of SrWO4 Powder

Synthesis of Crystallized BaWO<sub>4</sub> Nanorods in a Microemulsion System

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Preparation, structural and optical characterization of BaWO4 and PbWO4 thin films prepared by a chemical route

Cited by 100 publications

References 15 publications

Irreversible thermochromic response of RF sputtered nanocrystalline BaWO4 films for smart window applications

Irreversible thermochromic response of RF sputtered nanocrystalline BaWO4 films for smart window applications

Visible PL Phenomenon at Room Temperature in Disordered Structure of SrWO4 Powder

Synthesis of Crystallized BaWO&lt;sub&gt;4&lt;/sub&gt; Nanorods in a Microemulsion System

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Synthesis of Crystallized BaWO<sub>4</sub> Nanorods in a Microemulsion System