Dissolution of ZrO2 based pyrochlores in the acid pH range: A macroscopic and electron microscopy study

Finkeldei, Sarah; Brandt, Felix; Rozov, Konstantin; Bukaemskiy, Andrey; Neumeier, Stefan; Bosbach, Dirk

doi:10.1016/j.apgeochem.2014.06.014

Cited by 28 publications

(34 citation statements)

References 53 publications

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“…This interpretation is based on the height differences that are associated with the respective sites in the flux map (Fig. 8) and previous observations based on SEM pictures 19 . The combination of both, dissolution and grain pull-out contributions to the overall material flux during corrosion has been described in the literature 28 .…”

Section: Surface Reactivitymentioning

confidence: 99%

Direct Measurement of Surface Dissolution Rates in Potential Nuclear Waste Forms: The Example of Pyrochlore

Finkeldei

Brandt

Bosbach

et al. 2015

ACS Appl. Mater. Interfaces

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The long-term stability of ceramic materials that are considered as potential nuclear waste forms is governed by heterogeneous surface reactivity. Thus, instead of a mean rate, the identification of one or more dominant contributors to the overall dissolution rate is the key to predict the stability of waste forms quantitatively. Direct surface measurements by vertical scanning interferometry (VSI) and their analysis via material flux maps and resulting dissolution rate spectra provide data about dominant rate contributors and their variability over time. Using pyrochlore (Nd2Zr2O7) pellet dissolution under acidic conditions as an example, we demonstrate the identification and quantification of dissolution rate contributors, based on VSI data and rate spectrum analysis. Heterogeneous surface alteration of pyrochlore varies by a factor of about 5 and additional material loss by chemo-mechanical grain pull-out within the uppermost grain layer. We identified four different rate contributors that are responsible for the observed dissolution rate range of single grains. Our new concept offers the opportunity to increase our mechanistic understanding and to predict quantitatively the alteration of ceramic waste forms.

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Section: Surface Reactivitymentioning

confidence: 99%

Direct Measurement of Surface Dissolution Rates in Potential Nuclear Waste Forms: The Example of Pyrochlore

Finkeldei

Brandt

Bosbach

et al. 2015

ACS Appl. Mater. Interfaces

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“…Because natural pyrochlores contain up to 30 wt.% UO 2 and 9 wt.% ThO 2 without damaging their crystalline structure [6] the pyrochlore-type ceramics are also considered as a final crystalline form for nuclear waste disposal [7-9]. The relevant properties of pyrochlores have been systematically investigated by various methods such as the actinide-doping [10-16], the dissolution experiments [17][18][19], the ion beam-irradiation [20][21][22][23][24][25][26][27][28][29][30], and by atomistic calculations. The latter include simulations of the disordering process [31-34] and of the defect formation energetics [26,35].…”

mentioning

confidence: 99%

Defect formation energies in A 2 B 2 O 7 pyrochlores

Kowalski

Beridze

et al. 2015

Scripta Materialia

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“…The calcination took place for 2 h at 873 K with a heating and cooling rate of 4.8 K min

^{- 1}

. A detailed description of the synthesis procedure can be found elsewhere . The crystallization in the defect fluorite structure was realized by 10 h sintering at 1273 K. The pyrochlore structure was obtained by 5 h sintering at 1873 K. The heating and cooling rate was always 5.3 K min

^{- 1}

.…”

Section: Methodsmentioning

confidence: 99%

“…The crystallization in the defect fluorite structure was realized by 10 h sintering at 1273 K. The pyrochlore structure was obtained by 5 h sintering at 1873 K. The heating and cooling rate was always 5.3 K min

^{- 1}

. Powders consisted of primary particles with a grain size of 1–5

μ

m (). During the sintering process aggregates were formed.…”

Section: Methodsmentioning

confidence: 99%

A general and Eu specific perspective on lattice dynamics in pyrochlore and defect fluorite (EuNd)ZrO

Klobes

Finkeldei

Brandt

et al. 2015

Physica Status Solidi (b)

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Lattice dynamics in pyrochlore and defect fluorite type (Eu1−xNdx)2Zr2O7 were investigated using nuclear inelastic scattering by the 151Eu Mössbauer resonance for x = 0, 0.5, and 0.75 and using inelastic neutron scattering for x = 1. On the basis of the generalized density of phonon states obtained by inelastic neutron scattering, the vibrational entropy of the disordered defect fluorite Nd2Zr2O7 is found to be 12(3)% smaller than the one of the ordered pyrochlore counterpart. Accordingly, the loss of specific Zr–O coordination in the defect fluorite structure leads to a strong broadening of phonon modes. The Eu sublattice in both structure types was further characterized by thermodynamic quantities calculated using the Eu partial density of phonon states. The Eu framework is shown to be significantly softer than the other sublattices.

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Dissolution of ZrO2 based pyrochlores in the acid pH range: A macroscopic and electron microscopy study

Cited by 28 publications

References 53 publications

Direct Measurement of Surface Dissolution Rates in Potential Nuclear Waste Forms: The Example of Pyrochlore

Direct Measurement of Surface Dissolution Rates in Potential Nuclear Waste Forms: The Example of Pyrochlore

Defect formation energies in A 2 B 2 O 7 pyrochlores

A general and Eu specific perspective on lattice dynamics in pyrochlore and defect fluorite (EuNd)ZrO

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