Pressure-induced amorphization of cubic ZrMo2O8 studied in situ by X-ray absorption spectroscopy and diffraction

Varga, Tamás; Wilkinson, Angus P.; Lind, Cora; Bassett, William A.; Zha, Chang‐Sheng

doi:10.1016/j.ssc.2005.05.041

Cited by 21 publications

(28 citation statements)

References 67 publications

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“…However, thermal expansion mismatch between NTE and PTE materials in composites gives rise to internal stresses, which can be detrimental to the performance of the composite [9][10][11][12][13] as many NTE framework solids undergo phase transitions or changes in properties at low pressures. The combination of rich behavior upon modest compression and stresses arising from processing or thermal expansion mismatch motivates our studies of NTE materials under pressure [14][15][16][17][18][19][20][21][22][23][24].…”

Section: Introductionmentioning

confidence: 99%

Pressure-dependence of the phase transitions and thermal expansion in zirconium and hafnium pyrovanadate

Gallington

Hester

Kaplan

et al. 2017

Journal of Solid State Chemistry

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Low or negative thermal expansion (NTE) has been previously observed in members of the ZrP 2 O 7 family at temperatures higher than their order-disorder phase transitions. The thermoelastic properties and phase behavior of the low temperature superstructure and high temperature negative thermal expansion phases of ZrV 2 O 7 and HfV 2 O 7 were explored via in situ variable temperature/pressure powder x-ray diffraction measurements. The phase transition temperatures of ZrV 2 O 7 and HfV 2 O 7 exhibited a very strong dependence on pressure (∼ 700 K•GPa), with moderate compression suppressing the formation of their NTE phases below 513 K. Compression also reduced the magnitude of the coefficients of thermal expansion in both the positive and negative thermal expansion phases. Additionally, the high temperature NTE phase of ZrV 2 O 7 was found to be twice as stiff as the low temperature positive thermal expansion superstructure (24 and 12 GPa respectively).

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Section: Introductionmentioning

confidence: 99%

Pressure-dependence of the phase transitions and thermal expansion in zirconium and hafnium pyrovanadate

Gallington

Hester

Kaplan

et al. 2017

Journal of Solid State Chemistry

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“…1(a)), in agreement with prior work on this material. 29,31,32 The amorphization was largely complete by 3 GPa, and there were no obvious residual Bragg peaks at 5.5 GPa. Ruby fluorescence measurements indicated that the sample experienced conditions that were non-hydrostatic during its amorphization; an examination of multiple ruby chips showed large point to point pressure variations (range $ 0.7 GPa).…”

Section: Resultsmentioning

confidence: 95%

“…29 X-ray absorption spectroscopy studies suggest that amorphization involves changes in both molybdenum and zirconium coordination environments. 20,31 The current in situ high pressure total scattering data support a model for the amorphization of cubic ZrMo 2 O 8 that involves an increase in molybdenum coordination number, as the total number of short Mo-O bonds ($1.75 Å ) decreases on compression and the peak centered at $2.1 Å , corresponding to the longer Zr-O bonds in ZrO n polyhedra, or long Mo-O bonds in MoO x polyhedra with coordination number greater than 4, increases in magnitude (Fig. 3).…”

Section: Discussionmentioning

confidence: 99%

“…28 However, it adopts a disordered variant of the room temperature ZrW 2 O 8 structure under ambient conditions and its behavior on compression is different; 28,29 most notably it does not undergo a transition analogous to the a-c transition seen at $0.2 GPa in the tungstate. 30 There are few prior studies of pressure induced amorphization in this material, 29,31,32 none of which used total scattering methods. While total x-ray scattering measurements on ZrW 2 O 8 are very heavily influenced by contributions from the tungsten, the molybdenum and zirconium in ZrMo 2 O 8 both contribute heavily to the total scattering, potentially providing insights into the behavior of both metals at the expense of complicating the process of distinguishing contributions from Zr and Mo.…”

Section: Introductionmentioning

confidence: 99%

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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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“…ZM has been the focus of several studies within literature, where it has been synthesised for various applications, such as a Technetium-99m generator [ 4 , 5 , 6 , 7 ], a precursor for the formation of the negative thermal expansion material ZrMo 2 O 8 [ 8 , 9 ] and predominately for nuclear waste based studies [ 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 ]. Clearfield et al [ 24 ] were the first to publish a synthesis route for ZM to characterise its ion exchange properties.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and Physical Property Characterisation of Spheroidal and Cuboidal Nuclear Waste Simulant Dispersions

2018

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This study investigated dispersions analogous to highly active nuclear waste, formed from the reprocessing of Spent Nuclear Fuel (SNF). Non-radioactive simulants of spheroidal caesium phosphomolybdate (CPM) and cuboidal zirconium molybdate (ZM-a) were successfully synthesised; confirmed via Scanning Electron Microscopy (SEM), powder X-ray diffraction (PXRD) and Fourier transform infrared (FTIR) spectroscopy. In addition, a supplied ZM (ZM-b) with a rod-like/wheatsheaf morphology was also analysed along with titanium dioxide (TiO2). The simulants underwent thermal gravimetric analysis (TGA) and size analysis, where CPM was found to have a D50 value of 300 nm and a chemical formula of Cs3PMo12O40·13H2O, ZM-a a D50 value of 10 μm and a chemical formula of ZrMo2O7(OH)2·3H2O and ZM-b to have a D50 value of 14 μm and a chemical formula of ZrMo2O7(OH)2·4H2O. The synthesis of CPM was tracked via Ultraviolet-visible (UV-Vis) spectroscopy at both 25 °C and 50 °C, where the reaction was found to be first order with the rate constant highly temperature dependent. The morphology change from spheroidal CPM to cuboidal ZM-a was tracked via SEM, reporting to take 10 days. For the onward processing and immobilisation of these waste dispersions, centrifugal analysis was utilised to understand their settling behaviours, in both aqueous and 2 M nitric acid environments (mimicking current storage conditions). Spheroidal CPM was present in both conditions as agglomerated clusters, with relatively high settling rates. Conversely, the ZM were found to be stable in water, where their settling rate exponents were related to the morphology. In acid, the high effective electrolyte resulted in agglomeration and faster sedimentation.

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Pressure-induced amorphization of cubic ZrMo2O8 studied in situ by X-ray absorption spectroscopy and diffraction

Cited by 21 publications

References 67 publications

Pressure-dependence of the phase transitions and thermal expansion in zirconium and hafnium pyrovanadate

Pressure-dependence of the phase transitions and thermal expansion in zirconium and hafnium pyrovanadate

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

Synthesis and Physical Property Characterisation of Spheroidal and Cuboidal Nuclear Waste Simulant Dispersions

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