A lattice dynamical investigation for the zone-centre phonon frequencies of the NaMnF3 perovskite

Gupta, H.C.; Ashdhir, P.; Rawat, Chitra

doi:10.1016/s0022-3697(96)00080-7

Cited by 13 publications

(7 citation statements)

References 3 publications

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“…It can be observed that the spectra underwent some modifications as the temperature rose. After analyzing the previous work on Raman spectra of pyrochlores [14][15][16], the typical bands of Bi 5 NbO 10 powders were found to be located at 157, 268, 306, 505, 611 and 752 cm −1 from 450 to 850 °C. The band at 157 cm −1 was attributed to the Bi-O stretching modes, while the band at 752 cm In order to have further insight into the dielectric behavior of Bi 5 NbO 10 solid solutions, the imaginary parts of impedance (Z") were plotted against frequencies at various temperatures (Fig.…”

Section: Figurementioning

confidence: 99%

Dielectric relaxation and electrical conductivity in Bi5NbO10 oxygen ion conductors prepared by a modified sol–gel process

Hou

Vaish

et al. 2010

Journal of Power Sources

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Crystalline Bi 5 NbO 10 nanoparticles have been achieved through a modified sol-gel process using a mixture of ethylenediamine and ethanolamine as a solvent. The Bi 5 NbO 10 nanoparticles were characterized by X-ray diffraction (XRD), differential scanning calorimetry/thermogravimetry (DSC/TG), fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM) and Raman spectroscopy. The results showed that well-dispersed 5-60 nm Bi 5 NbO 10 nanoparticles were prepared through heat-treating the precursor at 650 °C and the high density pellets were obtained at temperatures lower than those commonly employed. The frequency and temperature dependence of the dielectric constant and the electrical conductivity of the Bi 5 NbO 10 solid solutions were investigated in the 0.1 Hz -1 MHz frequency range. Two distinct relaxation mechanisms were observed in the plots of dielectric loss and the imaginary part of impedance (Z") versus frequency in the temperature range of 200-350 o C. The dielectric constant and the loss in the low frequency regime were electrode dependent. The ionic conductivity of Bi 5 NbO 10 solid solutions at 700 o C is 2.86 (Ω·m) -1 which is in same order of magnitude for Y 2 O 3 -stabilized ZrO 2 ceramics at same temperature. These results suggest that Bi 5 NbO 10 is a promising material for an oxygen-ion conductor.

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Section: Figurementioning

confidence: 99%

Dielectric relaxation and electrical conductivity in Bi5NbO10 oxygen ion conductors prepared by a modified sol–gel process

Hou

Vaish

et al. 2010

Journal of Power Sources

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“…The only theoretical study which has been made to investigate vibrational modes in pyrochlore compounds is in the D 3d Space group instead of O h and then a correlation was made from space group D 3d to O h . 1 Such correlation studies do not provide precise information about the interatomic interactions, as has been investigated in the case of perovskite NaMnF 3 by Gupta et al 2 They found that interatomic interactions in NaMnF 3 are different in the actual orthorhombic (Pnma) structure when compared with the corresponding cubic structure studied by Daniel et al 3 Hence for the first time, in this work, an attempt was made using normal coordinate analysis to investigate the zone center wavenumber of rare earth titanates A 2 Ti 2 O 7 (A D Y, Sm, Gd, Yb) in their cubic pyrochlore structure. It was observed that the interatomic interactions, which explain the observed Raman and infrared modes, are different from those which were obtained from correlation studies from space group D 3d to O h .…”

Section: Introductionmentioning

confidence: 99%

Lattice dynamic investigation of the zone center wavenumbers of the cubic A2Ti2O7 pyrochlores

Gupta

Brown

Rani

et al. 2001

J. Raman Spectrosc.

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A short‐range force constant model was applied for the first time to investigate the phonons in A2Ti2O7 (A = Y, Sm, Gd, Yb) pyrochlores in their cubic phase of space group Fd3m. The calculations of phonons were made with five stretching and four bending force constants. The calculated values of Raman and infrared wavenumbers are in good agreement with the observed values. Copyright © 2001 John Wiley & Sons, Ltd.

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“…One of the F 2g modes is caused by the 8a oxygen sub-lattice vibration and the other F 2g Raman modes are related to 48f oxygen sub-lattice vibrations in the cubic pyrochlore lattice. 20,21 The E g mode can be assigned to B-O 6 Raman modes are assigned to symmetry species by referencing the previous literature, 18 and the proposed mode assignment is given in Table 2. The Raman modes are broad as compared to that of well-ordered crystalline compounds, which is due to the inherent disorder in the system.…”

Section: Raman Spectroscopic Studiesmentioning

confidence: 99%

“…One of the F 2g modes is caused by the 8a oxygen sub-lattice vibration and the other F 2g Raman modes are related to 48f oxygen sub-lattice vibrations in the cubic pyrochlore lattice. 20,21 The E g mode can be assigned to B-O 6 bending vibrations and the A 1g mode to O-B-O bending vibrations, while F 2g modes represent a mixture of A-O and B-O bond stretching vibrations with bending vibrations. Raman modes are assigned to symmetry species by referencing the previous literature, 18 and the proposed mode assignment is given in Table 2.…”

Section: Raman Spectroscopic Studiesmentioning

confidence: 99%

Structural and photoluminescence properties of stannate based displaced pyrochlore-type red phosphors: Ca_3−xSn₃Nb₂O₁₄:xEu³⁺

et al. 2015

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New stannate based displaced pyrochlore-type red phosphors, Ca(3-x)Sn3Nb2O14:xEu(3+), were prepared via a conventional solid state method. The influence of partial occupancy of Sn in both A and B sites of the pyrochlore-type oxides on the photoluminescence properties was studied using powder X-ray diffraction, FT-Raman, transmission electron microscopy, scanning electron microscopy with energy dispersive spectrometry, UV-visible absorption spectroscopy, and photoluminescence excitation and emission spectra with lifetime measurements. The structural analysis establishes that these oxides belong to a cubic displaced pyrochlore type structure with a space group Fd3̄m. These phosphors exhibit strong absorptions at near UV and blue wavelength regions and emit intense multiband emissions due to Eu(3+ 5)D0-(7)F(0, 1, 2) transitions. The absence of characteristic MD transition splitting points out that local cation disorder exists in this type of displaced pyrochlores, reducing the D(3d) inversion symmetry, which is not evidenced by such disorder in the X-ray diffraction analysis. The unusual forbidden intense sharp (5)D0-(7)F0 transition indicates single site occupancy of Eu(3+) with a narrower range of bonding environment, preventing the cluster formation. This is supported by the stable (5)D0 lifetime with Eu(3+) concentration. The Judd-Ofelt intensity parameter assessment corroborates these results. The CIE color coordinates of these phosphors were found to be (0.60, 0.40), which are close to the NTSC standard values (0.67, 0.33) for a potential red phosphor.

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A lattice dynamical investigation for the zone-centre phonon frequencies of the NaMnF3 perovskite

Cited by 13 publications

References 3 publications

Dielectric relaxation and electrical conductivity in Bi5NbO10 oxygen ion conductors prepared by a modified sol–gel process

Dielectric relaxation and electrical conductivity in Bi5NbO10 oxygen ion conductors prepared by a modified sol–gel process

Lattice dynamic investigation of the zone center wavenumbers of the cubic A2Ti2O7 pyrochlores

Structural and photoluminescence properties of stannate based displaced pyrochlore-type red phosphors: Ca_3−xSn₃Nb₂O₁₄:xEu³⁺

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A lattice dynamical investigation for the zone-centre phonon frequencies of the NaMnF3 perovskite

Cited by 13 publications

References 3 publications

Dielectric relaxation and electrical conductivity in Bi5NbO10 oxygen ion conductors prepared by a modified sol–gel process

Dielectric relaxation and electrical conductivity in Bi5NbO10 oxygen ion conductors prepared by a modified sol–gel process

Lattice dynamic investigation of the zone center wavenumbers of the cubic A2Ti2O7 pyrochlores

Structural and photoluminescence properties of stannate based displaced pyrochlore-type red phosphors: Ca3−xSn3Nb2O14:xEu3+

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Structural and photoluminescence properties of stannate based displaced pyrochlore-type red phosphors: Ca_3−xSn₃Nb₂O₁₄:xEu³⁺