Evolution of pressure-amorphized zirconium tungstate upon annealing

Ravindran, T. R.; Arora, Akhi̇lesh; Sastry, V. Sankara; Sahu, P. Ch.

doi:10.1016/j.jnoncrysol.2009.07.019

Cited by 8 publications

(4 citation statements)

References 38 publications

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“…The amorphous zirconium tungstate a-Zr͑WO 4 ͒ 2 recovered after releasing the pressure is found to be substantially denser than the starting cubic ␣ phase. 26 The density, structure, and stability of a-Zr͑WO 4 ͒ 2 has been studied by several investigators [26][27][28][29][30][31][32][33] and the samples are found to recrystallize to the ␣ phase when annealed above 900 K. On the other hand, if a-Zr͑WO 4 ͒ 2 is heated while under high pressure, it is reported to either decompose into mixture of simple oxides 30 or go to hexagonal U 3 O 8 -type structure 31 depending on the pressure and temperature of the treatment. The specific volumes ͑volume per formula unit͒ of a-Zr͑WO 4 ͒ 2 recovered after pressure cycling in large-volume piston-cylinder-type high-pressure apparatuses ranged between 142.6 and 152.6 Å 3 for samples treated between 4 and 7.5 GPa.…”

Section: Introductionmentioning

confidence: 99%

Structural analysis of pressure-amorphized zirconium tungstate

2010

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The negative thermal-expansion material zirconium tungstate, when subjected to a moderate pressure of 2 GPa, turns amorphous irreversibly; the amorphous state being ϳ26% more dense than the crystalline phase ␣-Zr͑WO 4 ͒ 2 . Structure of pressure-amorphized Zr͑WO 4 ͒ 2 is investigated using synchrotron x-ray diffraction. Structure factors S͑q͒ of samples recovered from different pressures are obtained. The first peak in S͑q͒ for 10.5 GPa-treated sample is found to occur at a slightly larger q than that recovered from 5.5 GPa, suggesting that the amorphous samples recovered from higher pressure could be more dense. The pair-correlation functions g͑r͒, obtained by Fourier transforming S͑q͒, suggests that the further densification of amorphous phase occurs via contraction of second and third neighbor shells representing O-O and W-W and W-Zr distances rather than first neighbor shell. In contrast to earlier speculations, the present results do not show evidence for an increase in the coordination number and consequent existence of distinct amorphous phases in samples recovered from pressures up to 10.5 GPa.

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Section: Introductionmentioning

confidence: 99%

Structural analysis of pressure-amorphized zirconium tungstate

2010

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“…a-Zr(WO 4 ) 2 is reported to decompose into mixture of simple oxides (ZrO 2 + 2WO 3 ), when its temperature is raised in-situ at high pressure [15]. On the other hand, it crystallizes back to the cubic phase if it is heated at ambient pressure [16]. Based on the closeness of the amorphous density with that of a mixture of simple oxides, the amorphous structure has been argued to be a precursor to decomposition [17].…”

Section: Resultsmentioning

confidence: 99%

Polyamorphism in network structures

Arora

2012

J. Phys.: Conf. Ser.

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Abstract. Reports of high-density amorphous forms of ice, quartz and Si have intensified the search for amorphous polymorphs in other systems. The network structures that exhibit pressure-induced amorphization are interesting from the point of view of polyamorphism. Recent in-situ high pressure Raman scattering and synchrotron x-ray diffraction studies on negative thermal expansion material zirconium tungstate have revealed an amorphous to amorphous transition at 19 GPa. The transition was identified for the discontinuities in the structural parameters such as position and height of the first peak of the structure factor and that in the tungstate internal vibrational mode frequency. Another compound, vanadium pentaoxide that forms a glass during melt-quenching, is also found to turn amorphous at 40 GPa, pointing to a possibility of polyamorphism.

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“…39) that contains 6 coordinate tungsten and zirconium. 26 It has been suggested that the relaxation of a-ZrW 2 O 8 on decompression and heating may involve the breaking of some W-O-W bridges. 21 Calorimetric studies have shown that structural relaxation on heating prior to recrystallization, which is associated with a decrease in density for the glass, is exothermic, but that the recrystallization event itself is endothermic.…”

Section: Discussionmentioning

confidence: 99%

“…9-20) (amorphous-ZrW 2 O 8 ), the physical properties 21,22 and thermodynamics of the amorphous material, [23][24][25] and its relaxation on heat treatment. 21,25,26 It has even been proposed that ZrW 2 O 8 may display polyamorphism on compression. 18 X-ray and neutron total scattering methods are, in principle, excellent probes of the structural changes associated with pressure induced amorphization.…”

Section: Introductionmentioning

confidence: 99%

Pressure induced amorphization of ZrMo2O8 and its relaxation on decompression as seen by in situ total x-ray scattering

Wilkinson

Greve

Ruschman

et al. 2012

Journal of Applied Physics

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The pressure induced amorphization of the negative thermal expansion material cubic ZrMo2O8 was examined in situ within a diamond anvil cell, using high energy x-ray total scattering, during compression up to ∼7.2 GPa, and then decompressed. The amorphization upon compression was largely complete by ∼3 GPa. There was significant, but not complete, structural relaxation of the amorphous material on decompression; the pair distribution function (PDF) for the material recovered from 7.2 GPa closely resembled that for the sample during initial compression at ∼5.5 GPa. The PDFs indicated that the amorphization, densification, and relaxation of the amorphous solid involve changes in the first coordination shell of molybdenum and the creation/loss of Mo-O-M bridges with ∼3.4 Å Mo-M separation (M–Mo or Zr).

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Evolution of pressure-amorphized zirconium tungstate upon annealing

Cited by 8 publications

References 38 publications

Structural analysis of pressure-amorphized zirconium tungstate

Structural analysis of pressure-amorphized zirconium tungstate

Polyamorphism in network structures

Pressure induced amorphization of ZrMo2O8 and its relaxation on decompression as seen by in situ total x-ray scattering

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