High-pressure x-ray diffraction and Raman spectroscopy of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi mathvariant="normal">Hf</mml:mi><mml:msub><mml:mi mathvariant="normal">V</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mn>7</mml:mn></mml:msub></mml:mrow></mml:math>

Hemamala, U. L. C.; El-Ghussein, F.; Goedken, A. M.; Chen, Bin; Leroux, C.; Krüger, Michael

doi:10.1103/physrevb.70.214114

Cited by 16 publications

(17 citation statements)

References 19 publications

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“…The calculated range ͑Fig. 2͒ of phonon frequencies in the high-temperature phase of ZrV 2 O 7 and HfV 2 O 7 is nearly same as that obtained from the experimental data 14,17 in the low-temperature phase. The potential reproduces the equilibrium crystal structure ͑Table I͒ and other dynamical properties quite satisfactorily as discussed later.…”

Section: Resultssupporting

confidence: 79%

“…The experimental Raman data 14,17 have been obtained from polycrystalline samples in the low-temperature phase. The range of phonon frequency in the high-temperature phase is expected to be same as that in the low-temperature phase.…”

Section: Resultsmentioning

confidence: 99%

“…Recent papers have described work on the structure and thermodynamic properties of these compounds using a combination of diffraction and spectroscopic techniques. [13][14][15][16][17] Powder and neutron diffraction, electron microscopy, and differential scanning calorimetry have been used to study structural changes in MV 2 O 7 as a function of temperature. Like the ZrW 2 O 8 family 1 ͑space group P2 1 3͒, the ZrV 2 O 7 family 15,16 has a cubic crystal structure ͑though with a different space group Pa3͒, and shows a large isotropic NTE.…”

Section: Introductionmentioning

confidence: 99%

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Lattice dynamical calculation of negative thermal expansion inZrV2O7andHfV2

Mittal

Chaplot

2008

Phys. Rev. B

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We report lattice dynamics calculations of negative thermal-expansion ͑NTE͒ behavior of ZrV 2 O 7 family, extending our previous work on the ZrW 2 O 8 family. The two families of compounds differ in terms of the oxygen coordination around the V/W atoms leading to differences in the nature of soft phonons under compression that are responsible for the NTE. Our calculations quantitatively reproduce the negative expansion over a range of temperatures. We also discuss the relation of the soft phonons with the phase transitions observed in the ZrV 2 O 7 family. Especially, the calculations show a soft-phonon mode at a wave vector of 0.31͗1,1,0͘, which is in excellent agreement with the known incommensurate modulation in ZrV 2 O 7 below 375 K.

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Section: Resultssupporting

confidence: 79%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Lattice dynamical calculation of negative thermal expansion inZrV2O7andHfV2

Mittal

Chaplot

2008

Phys. Rev. B

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“…Low bulk moduli are common amongst NTE and related materials, for example cubic ZrW 2 O 8 ͑72.5 GPa by neutron diffraction͒, 23 cubic ZrMo 2 O 8 ͑44.6 GPa͒, 88 cubic ZrP 2 O 7 ͑39 GPa͒, 35 cubic HfV 2 O 7 ͑14 GPa͒, 89 and cubic ZrV 2 O 7 ͑18 GPa͒, 35 presumably arising from the low density and framework flexibility that is characteristic of them. The marked decrease in bulk modulus at the phase transition in Sc 2 W 3 O 12 is reminiscent of the compressibility collapse seen in ReO 3 as the O-Re-O-Re-O chains start to kink, 90,91 and similar to that seen at the cubic to rhombohedral transition in NbO 2 F. 87,92 While ReO 3 and Nb 2 OF do not show NTE, they have structural characteristics typical of NTE materials and the close structural relative TaO 2 F has an expansion coefficient very close to zero, and perhaps slightly negative, over a wide temperature range.…”

Section: Discussionmentioning

confidence: 99%

In situhigh-pressure synchrotron x-ray diffraction study ofSc2W3O12at up to 10 GPa

et al. 2005

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Sc 2 W 3 O 12 is known to display both negative thermal expansion and significant Sc 3+ conductivity. Monochromatic synchrotron x-ray powder diffraction was used to study Sc 2 ͑WO 4 ͒ 3 at pressures up to 10 GPa in diamond anvil cells. Nitrogen and isopropanol were both used as pressure transmitting media. A phase transition from orthorhombic ͑Pnca͒ to monoclinic ͑P2 1 / a͒ symmetry was observed at ϳ0.3 GPa with a volume reduction of ϳ1.7%. A second crystalline to crystalline phase transition was seen at ϳ2.8 GPa. The latter was not reversible on decompression. The orthorhombic phase displays highly anisotropic compressibility, but that of the monoclinic phase is almost isotropic ͓orthorhombic in isopropanol ␤ a = 6.32͑16͒ ϫ 10 −3 GPa −1 , ␤ b = 1.76͑21͒ ϫ 10 −2 GPa −1 , ␤ c = 6.84͑32͒ ϫ 10 −3 GPa −1 ; monoclinic in isopropanol ␤ a = 1.85͑3͒ ϫ 10 −2 GPa −1 , ␤ b = 1.78͑3͒ ϫ 10 −2 GPa −1 , ␤ c = 1.69͑9͒ ϫ 10 −2 GPa −1 ͔. Sc 2 ͑WO 4 ͒ 3 is very soft even when compared to most other NTE phases. Fitting a Birch-Murnaghan equation of state to data from the experiment in isopropanol gave a bulk modulus ͑K 0 ͒ of 31͑3͒ for the orthorhombic and 14͑1͒ GPa for the monoclinic phase. This reduction in bulk modulus at the phase transition and the reduction in volume per formula unit is almost entirely associated with changes in the orthorhombic a and c directions. The variation of b ortho and its monoclinic equivalent lattice constant is essentially continuous through the transition. The pressure of the orthorhombic to monoclinic phase transition in A 2 M 3 O 12 compounds does not have a strong dependence on the identity of the A 3+ cation. Amorphization did not occur in the pressure range studied.

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“…The possible correlation between these phenomena in framework structured materials is a controversial issue in the literature. Especially, several studies have been published dealing with the possible relationship between PIA and the anomalous thermal behavior observed for some framework structured materials [4][5][6][7][8][9][10][11]. These studies, which followed a first report on PIA of zirconium tungstate [6], have been mainly focused on oxide compounds.…”

Section: Introductionmentioning

confidence: 97%