The structure of niobium and tantalum oxides processed by concentrated light flux

Палатников, М. Н.; Щербина, О. Б.; Сидоров, Н. В.; Skab, I.; Борманис, К.

doi:10.3116/16091833/13/4/207/2012

Cited by 31 publications

(12 citation statements)

References 16 publications

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“…The bands at higher wavelength, between 500 and 1000 cm -1 , were assigned to stretching of the covalent Nb-O bonds in NbO 4 . 42,43 As a result of the changes in Dy 3+ concentration, the full width at half maximum (FWHM) increased for some bands, especially for the band at 803 cm -1…”

Section: Raman Spectroscopymentioning

confidence: 99%

Effect of Dy3+ Amount on the Structural and Luminescence Properties of LaNbO4:Dy3+ Phosphor Obtained by One-Step Spray Pyrolysis Process

Freiria¹,

Ribeiro²,

Verelst³

et al. 2017

J. Braz. Chem. Soc.

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In this study, Dy 3+ -doped LaNbO 4 phosphors with a blue to white emission that can be tuned by varying the activator concentration were prepared by one-step spray pyrolysis process. According to the powder X-ray diffraction results, increasing Dy 3+ concentration favored the tetragonal phase. Slight changes were observed in the recorded Raman spectra as a function of Dy 3+ concentrations while SEM (scanning electron microscopy) micrographs presented similar profiles regardless the Dy 3+ amount. Investigation of Dy 3+ emission data in the visible range showed that rising the Dy 3+ concentration progressively shifted the emission towards the white color. All samples presented a wide excitation range from 254 to 475 nm. Keywords: spray pyrolysis, luminescence, lanthanum niobate IntroductionOver the last years, rare earth ions (RE 3+ ) have received increasing attention: solid-state materials doped with these ions can be applied in color screens, lighting, and optical devices. [1][2][3][4][5] The luminescence properties of these materials heavily depend on the structure of the electron energy levels. In RE 3+ , chemical binding affects these levels very little because orbitals 5s and 5p shield orbital 4f efficiently. 6 The f-f transitions in RE 3+ cause an array of emissions at different wavelengths, giving rise to a plethora of colors. However, f-f transitions are forbidden by the parity selection rule (Laporte rule), so they have low excitation efficiency. Excitation requires the use of a matrix and/or sensitizer that is able to absorb energy and transfer it to an emitting ion. 6,7 Lanthanum niobate (LaNbO 4 ) is a promising material for multifunctional applications. It has a band-gap of approximately 4.8 eV and emits blue and ultraviolet light when excited with ultraviolet (UV) radiation and X-rays, respectively. 8,9 Moreover, LaNbO 4 can transfer the absorbed energy to other emitting species, leading to different fluorescence emissions. 10,11 This oxide has been prepared by a number of techniques; for example, spray pyrolysis (SP), 12-14 solid-state reaction, 15-17 reactions in solution [18][19][20] and sol-gel route. 10,21 However, with an exception of our previously published work, 22 the authors were not able to finely control the size, shape, and distribution properties. Moreover, the SP process is completed in only several seconds, while other currently available methods require several hours or days to complete the process, even requiring a post annealing treatment. Briefly, SP process involves the vaporization of precursor solution followed by the drying, precipitation and decomposition in heated tubular furnace reactors. The stoichiometric ratio in the final prepared material is the same as the precursor solution, since the reaction and aggregation volume are confined in each generated micrometric droplet, which can be seen as a micro reactor. Therefore, particles synthesized by the SP process can be obtained on a laboratory or on an industrial scale. [22][23][24][25] Among the various material...

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Section: Raman Spectroscopymentioning

confidence: 99%

Effect of Dy3+ Amount on the Structural and Luminescence Properties of LaNbO4:Dy3+ Phosphor Obtained by One-Step Spray Pyrolysis Process

Freiria¹,

Ribeiro²,

Verelst³

et al. 2017

J. Braz. Chem. Soc.

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“…The high crystallinity of the Nb 2 O 5 as is evidenced by the powder XRD pattern is also confirmed from the Raman spectrum by giving well defined peaks in the 1000 cm –1 to 100 cm –1 region (Figure c). The peaks at 141 cm –1 , and 240 cm –1 and 317 cm –1 are due to the ν 1 (whole octahedron vibrations), and ν 2 and ν 3 (cation vibration inside the octahedron and tetrahedron, respectively) . The strong peak at 717 cm –1 (ν 4 ) corresponds to the stretching vibration of Nb–O bonds .…”

Section: Resultsmentioning

confidence: 98%

“…The peaks at 141 cm –1 , and 240 cm –1 and 317 cm –1 are due to the ν 1 (whole octahedron vibrations), and ν 2 and ν 3 (cation vibration inside the octahedron and tetrahedron, respectively) . The strong peak at 717 cm –1 (ν 4 ) corresponds to the stretching vibration of Nb–O bonds . The DRS spectrum of Nb 2 O 5 was measured, and it is presented in Figure d.…”

Section: Resultsmentioning

confidence: 98%

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Synthesis of Nb₂O₅ Nanoplates and their Conversion into NbO₂F Nanoparticles by Controlled Fluorination with Molecular Fluorine

2019

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Following a synthesis protocol developed by us, nanoparticles of NbO2F were prepared for the very first time by the gas‐solid type fluorination of hexagonal‐shaped niobium pentoxide (Nb2O5) nanostructures with molecular fluorine (F2). The optimized fluorination parameters, like F2 pressure, gas‐solid reaction temperature, and duration, were very crucial for successful synthesis of the desired NbO2F nanomaterial. The hexagonal‐shaped Nb2O5 nanoplates were synthesized in a previous step by a hydrothermal method. The oxide to oxyfluoride transformation protocol is highly efficient, giving single‐phase NbO2F in the cubic crystal system, as confirmed by powder X‐ray diffraction (XRD) and energy dispersive X‐ray spectroscopy (EDX). The structures of Nb2O5 nanoplates and NbO2F nanoparticles were also characterized by vibrational spectroscopy (FTIR and Raman scattering). The morphologies of the materials were studied by transmission and scanning electron microscopy (T/SEM), which revealed that the hexagonal‐shaped plates of Nb2O5 disintegrated into nanoparticles with an approximate size of 27 nm upon fluorination to provide NbO2F. The lithiation and sodiation ability of nanostructured NbO2F is established with relevant electrochemical properties.

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“…As bandas de Raman mais intensas são normalmente atribuídas a vibrações simétricas, provocando as mudanças mais significativas na polarização da célula unitária (Dobal et al, 2002;Palatnikov et al, 2012 (Sidorov et al, 2004). A banda bem definida em cerca de 992 cm -1 e a banda em 900 cm -1 são atribuídas a modos de estiramentos simétrico e antissimétrico da ligação dupla terminal Nb=O, respectivamente (Jehng e Wachs, 1991;Chan et al, 2017).…”

Section: Distribuição Do Tamanho De Partículas Por Difração De Laserunclassified

Produção de membranas cerâmicas do tipo fibra oca utilizando pentóxido de nióbio

Ferreira¹

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The structure of niobium and tantalum oxides processed by concentrated light flux

Cited by 31 publications

References 16 publications

Effect of Dy3+ Amount on the Structural and Luminescence Properties of LaNbO4:Dy3+ Phosphor Obtained by One-Step Spray Pyrolysis Process

Effect of Dy3+ Amount on the Structural and Luminescence Properties of LaNbO4:Dy3+ Phosphor Obtained by One-Step Spray Pyrolysis Process

Synthesis of Nb₂O₅ Nanoplates and their Conversion into NbO₂F Nanoparticles by Controlled Fluorination with Molecular Fluorine

Produção de membranas cerâmicas do tipo fibra oca utilizando pentóxido de nióbio

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The structure of niobium and tantalum oxides processed by concentrated light flux

Cited by 31 publications

References 16 publications

Effect of Dy3+ Amount on the Structural and Luminescence Properties of LaNbO4:Dy3+ Phosphor Obtained by One-Step Spray Pyrolysis Process

Effect of Dy3+ Amount on the Structural and Luminescence Properties of LaNbO4:Dy3+ Phosphor Obtained by One-Step Spray Pyrolysis Process

Synthesis of Nb2O5 Nanoplates and their Conversion into NbO2F Nanoparticles by Controlled Fluorination with Molecular Fluorine

Produção de membranas cerâmicas do tipo fibra oca utilizando pentóxido de nióbio

Contact Info

Product

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Synthesis of Nb₂O₅ Nanoplates and their Conversion into NbO₂F Nanoparticles by Controlled Fluorination with Molecular Fluorine