Effect of partial preferential orientation and distortions in octahedral clusters on the photoluminescence properties of FeWO4 nanocrystals

Almeida, M. A. P.; Cavalcante, L. S.; Morilla-Santos, C.; Dalmaschio, Cleocir José; Rajagopal, Senthilkumar; Li, Máximo Siu; Longo, Elson

doi:10.1039/c2ce25771h

Cited by 34 publications

(20 citation statements)

References 47 publications

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“…In general, the simulated Raman profile has the same pattern of the experimental results. As the hydrothermal method for materials synthesis usually leads to a crystal growth with a preferential orientation, we argued that our samples may have a partial preferential orientation, which explains the differences between some of the experimental and calculated Raman intensities. As one can note in the XRD data, it can be confirmed a tendency for a microcrystal growth along the [001] direction, because the experimental peak intensities of the (001), (002), (003), and (004) reflections are higher than those reported at the inorganic crystal structure database (i.e., completely random oriented; Figure ).…”

Section: Resultsmentioning

confidence: 86%

Theoretical methods for calculations of optical phonons in BiOBr: Analysis and correction of propagated errors

Ferrer

Rodrigues

Almeida

et al. 2018

J Raman Spectroscopy

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Theoretical and experimental methods were employed to investigate the vibrational modes of BiOBr. Wavenumber prediction and assignments of the infrared and Raman modes were performed using density functional theory and lattice dynamics calculations. The theoretical models were directly compared with the experimental results of particles fabricated using the microwave‐assisted hydrothermal method and results reported in literature. The simulation results of the structure parameters, band gap, and vibrational modes are in agreement with the corresponding experimental values. The proposed models and calculations provided detailed insights into the vibrational modes and enabled to determine propagated assignment errors in results reported in the literature.

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Section: Resultsmentioning

confidence: 86%

Theoretical methods for calculations of optical phonons in BiOBr: Analysis and correction of propagated errors

Ferrer

Rodrigues

Almeida

et al. 2018

J Raman Spectroscopy

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“…It is interesting that the change in grain shape and crystal orientation produced additional strains (ε) in the film, and they can be represented by the following equation by adopting three Cartesian coordinates of reference frames in the case of polycrystalline film:

ε = \sum_{i = 1}^{n} ε_{i}^{h_{i} k_{i} l_{i}} v_{i}^{h_{i} k_{i} l_{i}}

where h i k i l i are the Miller indices,

ε_{i}^{h_{i} k_{i} l_{i}}

is the strain, and

v_{i}^{h_{i} k_{i} l_{i}}

is the volume fraction of i th grain. In several reports, these strains may cause extra distortion in the crystal, and the defect states were simultaneously fabricated.…”

Section: Resultsmentioning

confidence: 99%

“…where h i k i l i are the Miller indices, e hikili i is the strain, and v hikili i is the volume fraction of ith grain. In several reports, these strains may cause extra distortion in the crystal, 25,26 and the defect states were simultaneously fabricated.…”

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confidence: 99%

Strong Near‐Infrared Photoluminescence Emission of (003)‐Oriented MgTiO₃ Thin Films

Huang

2013

J. Am. Ceram. Soc.

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In this study, ilmenite‐MgTiO3 films were sputtered on p‐type Si(111) substrates and the extrinsic effects, such as grain size, crystallinity, and orientation of photoluminescence (PL) properties of the films are discussed. To reduce the effect of oxygen vacancies (act as shallow defects) on PL emissions in the films, oxygen (O2) was introduced as the sputtering gas and the excitation light source (λ = 532 nm) which has a corresponding energy (hν = 2.33 eV) below the shallow defect states was used. In this study, intense near‐infrared (NIR) PL emission centered at 810.1 nm at room temperature can be observed when the MgTiO3 thin films exhibit the preferred (003)‐orientation and accompanied by the presence of hexagon‐shaped grains. In this study, the experiment results reveal that the NIR emission intensity of MgTiO3 films highly depend on crystal orientation and/or grain morphology.

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“…The larger Ba 2? and Sr 2? cations are coordinated to eight oxygen (O) atoms in solid in tetragonal lattice which is composed of deltahedral 6 ] clusters [12,13]. Moreover, in AWO 4 and/or AMoO 4 materials with scheelite-type tetragonal structure have a body centered tetragonal scheelite structure, with four formula units per primitive cell (Z = 4) [14].…”

Section: Introductionmentioning

confidence: 99%

Structural refinement, Raman spectroscopy, optical and electrical properties of (Ba1−xSrx)MoO4 ceramics

Ghosh

Rout

Tiwari

et al. 2015

J Mater Sci: Mater Electron

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In this paper, structural refinement, Raman spectroscopy, optical and electrical properties of barium strontium molybdate [(Ba 1-x Sr x )MoO 4 ] ceramics with different (x) contents (x = 0; 0.1; 0.2; 0.3; 0.4; 0.5; 0.6; 0.7; 0.8; 0.9; and 1) were synthesized by the solid state reaction method. These ceramics were structurally characterized by X-ray diffraction (XRD), Rietveld refinement, and micro-Raman spectroscopy. The shape of the grains for these ceramics was observed by means of scanning electron microscopy (SEM) images. The optical properties were investigated using ultraviolet-visible (UV-Vis) absorption spectroscopy and photoluminescence (PL) measurements. The dielectric and ferroelectric properties were analyzed by permittivity (e r ), loss tangent (tan d) and polarization versus electric field (P-E) hysteresis loop. XRD patterns, Rietveld refinement, and micro-Raman spectra showed that all ceramics are monophasic with a scheelite-type tetragonal structure. A decreased of lattice parameters and unit cell volume was observed with the increase of Sr 2? ions into BaMoO 4 lattice. Rietveld data were employed to model the [BaO 8 ], [SrO 8 ] and [MoO 4 ] clusters in the tetragonal lattices. The SEM images indicate that increased x content promotes a decrease in the grain size and modifications in the shape. UV-Vis spectra indicated a decrease in the optical band gap values with an increase in x content in the (Ba 1-x Sr x )MoO 4 ceramics. PL emissions exhibit a non-linear behavior to increase or decrease with the increase of Sr 2? ions in the tetragonal lattices, when excited by a wavelength of 350 nm. The P-E decreases along with slim hysteresis loop towards higher Sr 2? ions concentration. These effects are correlated with decrease in lattice parameters and c/a ratio in this tetragonal lattice. The microwave dielectric constant and quality factor were measured using the method proposed by Hakki-Coleman. Temperature coefficient and quality factor of these materials were measured by vector network analyzer.

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Effect of partial preferential orientation and distortions in octahedral clusters on the photoluminescence properties of FeWO4 nanocrystals

Cited by 34 publications

References 47 publications

Theoretical methods for calculations of optical phonons in BiOBr: Analysis and correction of propagated errors

Theoretical methods for calculations of optical phonons in BiOBr: Analysis and correction of propagated errors

Strong Near‐Infrared Photoluminescence Emission of (003)‐Oriented MgTiO₃ Thin Films

Structural refinement, Raman spectroscopy, optical and electrical properties of (Ba1−xSrx)MoO4 ceramics

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Effect of partial preferential orientation and distortions in octahedral clusters on the photoluminescence properties of FeWO4 nanocrystals

Cited by 34 publications

References 47 publications

Theoretical methods for calculations of optical phonons in BiOBr: Analysis and correction of propagated errors

Theoretical methods for calculations of optical phonons in BiOBr: Analysis and correction of propagated errors

Strong Near‐Infrared Photoluminescence Emission of (003)‐Oriented MgTiO3 Thin Films

Structural refinement, Raman spectroscopy, optical and electrical properties of (Ba1−xSrx)MoO4 ceramics

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Strong Near‐Infrared Photoluminescence Emission of (003)‐Oriented MgTiO₃ Thin Films