The structural role of Zr within alkali borosilicate glasses for nuclear waste immobilisation

Connelly, Andrew; Hyatt, Neil C.; Travis, Karl P.; Hand, Russell J.; Maddrell, Ewan R.; Short, Rick

doi:10.1016/j.jnoncrysol.2011.01.005

Cited by 56 publications

(25 citation statements)

References 26 publications

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“…In order to further determine the local coordination number around Zr, comparison of Zr K‐edge (main‐edge) XANES spectra of Ca 0.3 Ho 0.7 ZrTi 1.3 (Al, Fe) 0.7 O 7 with model compounds monoclinic‐ZrO 2 and ZrSiO 4 was taken. Monoclinic‐ZrO 2 and ZrSiO 4 are typical pure ZrO 7 and ZrO 8 coordination, respectively and employed as reference compounds in many researches . The reason for only using these two coordination environments is that there are only seven‐ and eight‐ coordinated sites for Zr in the zirconolite‐2M structure .…”

Section: Resultsmentioning

confidence: 99%

“…[49][50][51][52][53] The reason for only using these two coordination environments is that there are only seven-and eight-coordinated sites for Zr in the zirconolite-2M structure. 10,11 According to the results shown in Figure 10D and the studies to differentiate ZrO 7 and ZrO 8 environments in the literature, 49,[51][52][53] it is concluded that the Zr has a major sevenfold oxygen environment with a trace of 8-coordinated environment. This conclusion is consistent with those reported by Rossell who used Rietveld structural XRD to study the cations occupancy in zirconolite-2M structure and revealed that 2-7.5% of Ca 2+ sites (in forms of CaO 8 ) was replaced by Zr 4+ in zirconolite-2M structure.…”

Section: Occupancy Evolution Of Cations Fe 3+ mentioning

confidence: 99%

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Synchrotron x‐ray spectroscopy investigation of the Ca_1−xLn_xZrTi_2−x(Al, Fe)_xO₇ zirconolite ceramics (Ln = La, Nd, Gd, Ho, Yb)

Liao

et al. 2019

J Am Ceram Soc

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When incorporating actinides into zirconolite for high‐level radioactive waste immobilization, Al3+ and Fe3+ ions generally act as charge compensators. In this study, we rationally designed a series of Ca1-xLnxZrTi2-x)(Al,0.166667emFexnormalO7 (Ln = La, Nd, Gd, Ho, Yb) to unravel the dopant solubility and evolutions of the crystalline phase and local environment of cations through synchrotron X‐ray methods. It was found that single zirconolite phase is difficult to obtain and the fraction of perovskite have an increase with x from 0.1 to 0.9 in Ca1-xLaxZrTi2-x)(Al,0.166667emFexnormalO7. Formation of both zirconolite‐2M and zirconolite‐3O phases was observed in Ca1-xNdxZrTi2-x)(Al,0.166667emFexnormalO7 and Ca1-xGdxZrTi2-x)(Al,0.166667emFexnormalO7. Phase transformation from zirconolite‐2M to 3O occurs at x = 0.7 for Ca1-xNdxZrTi2-x)(Al,0.166667emFexnormalO7 while x = 0.9 for Ca1-xGdxZrTi2-x)(Al,0.166667emFexnormalO7. The solubility of Ca1-xHoxZrTi2-x)(Al,0.166667emFexnormalO7 and Ca1-xYbxZrTi2-x)(Al,0.166667emFexnormalO7 to form single zirconolite‐2M can reach to 0.9 f.u. and 0.7 f.u., respectively. The evolution of lattice parameters of zirconolite in Ca1-xLnxZrTi2-x)(Al,0.166667emFexnormalO7 is greatly related to the ionic radii of cations and substitution mechanism among the cations. X‐ray absorption near edge spectroscopy revealed that Fe3+ ions replace both five‐ and six‐coordinated Ti sites and the ratio of TiO5 to TiO6 decreases when increasing dopant concentration in the Ca1-xHoxZrTi2-x)(Al,0.166667emFexnormalO7. For the local environment of Zr4+, the major form is ZrO7 with a trace of ZrO8.

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Section: Resultsmentioning

confidence: 99%

Section: Occupancy Evolution Of Cations Fe 3+ mentioning

confidence: 99%

Synchrotron x‐ray spectroscopy investigation of the Ca_1−xLn_xZrTi_2−x(Al, Fe)_xO₇ zirconolite ceramics (Ln = La, Nd, Gd, Ho, Yb)

Liao

et al. 2019

J Am Ceram Soc

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“…The study of Zr in both simplified and simulant borosilicate glasses using EXAFS 44,57,60,61 dates back to the late 1990s and has consistently shown that Zr is in 6-fold coordination, with evidence for 7-fold coordinated Zr only appearing at very high ZrO 2 contents. 61 In contrast, the composition of the second shell has not been unequivocally resolved from EXAFS due in large part to the large number of degrees of freedom (elements, distances, coordination numbers, Debye-Waller factors) in the traditional shell-by-shell EXAFS fitting approach.…”

Section: Discussionmentioning

confidence: 99%

Structural role of ZrO2 and its impact on properties of boroaluminosilicate nuclear waste glasses

Deng

Kerisit

et al. 2018

npj Mater Degrad

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Addition of zirconia (ZrO 2 ) to nuclear waste glasses, even in small amount, significantly affects physical properties such as chemical durability, density, viscosity, and glass transition temperature. Hence ZrO 2 plays an important role in the development of nuclear waste glass compositions. It was found recently that addition of zirconia decreases the initial dissolution rate but increases longterm dissolution by changing the protective properties such as porosity of alteration layers. In this study, the International Simple Glass (ISG) with different amounts of ZrO 2 /SiO 2 substitution was simulated using classical molecular dynamics (MD) simulations and recently developed composition-dependent potential sets. Local structural descriptors such as bond distances, bond angle distributions, and coordination numbers were systematically studied and compared with experimental values. Zr K-edge extended X-ray absorption fine structure spectra were also calculated and compared with experiment to resolve the local coordination environment around Zr. Medium-range structural information (e.g., Q n distribution, network connectivity, and ring-size distribution) showed that ZrO 2 /SiO 2 substitution increases the overall network connectivity and the amount of smaller sized rings, which will decrease the initial dissolution rate by strengthening the glass network and limiting water diffusivity. Finally, diffusion and dynamic properties of the ions were studied and discussed to develop a better understanding of the chemical durability of these glasses.

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“…For manganese, magnesium and titanium, their low concentrations mean that any changes in oxidation state or coordination from those assumed for modelling, have minimal effects. Zirconium has been shown [46,47] to occur predominantly as [6] Zr 4+ in oxide glasses broadly similar to those under consideration here, and consequently we have assumed [6] Zr 4+ in our models.…”

Section: +mentioning

confidence: 92%

Modelling the sulfate capacity of simulated radioactive waste borosilicate glasses

Bingham

Vaishnav

Forder

et al. 2017

Journal of Alloys and Compounds

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(2017). Modelling the sulfate capacity of simulated radioactive waste borosilicate glasses. Journal of Alloys and Compounds, 695,[656][657][658][659][660][661][662][663][664][665][666][667]. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Copyright and re-use policy M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT

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The structural role of Zr within alkali borosilicate glasses for nuclear waste immobilisation

Cited by 56 publications

References 26 publications

Synchrotron x‐ray spectroscopy investigation of the Ca_1−xLn_xZrTi_2−x(Al, Fe)_xO₇ zirconolite ceramics (Ln = La, Nd, Gd, Ho, Yb)

Synchrotron x‐ray spectroscopy investigation of the Ca_1−xLn_xZrTi_2−x(Al, Fe)_xO₇ zirconolite ceramics (Ln = La, Nd, Gd, Ho, Yb)

Structural role of ZrO2 and its impact on properties of boroaluminosilicate nuclear waste glasses

Modelling the sulfate capacity of simulated radioactive waste borosilicate glasses

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The structural role of Zr within alkali borosilicate glasses for nuclear waste immobilisation

Cited by 56 publications

References 26 publications

Synchrotron x‐ray spectroscopy investigation of the Ca1−xLnxZrTi2−x(Al, Fe)xO7 zirconolite ceramics (Ln = La, Nd, Gd, Ho, Yb)

Synchrotron x‐ray spectroscopy investigation of the Ca1−xLnxZrTi2−x(Al, Fe)xO7 zirconolite ceramics (Ln = La, Nd, Gd, Ho, Yb)

Structural role of ZrO2 and its impact on properties of boroaluminosilicate nuclear waste glasses

Modelling the sulfate capacity of simulated radioactive waste borosilicate glasses

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Product

Resources

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Synchrotron x‐ray spectroscopy investigation of the Ca_1−xLn_xZrTi_2−x(Al, Fe)_xO₇ zirconolite ceramics (Ln = La, Nd, Gd, Ho, Yb)

Synchrotron x‐ray spectroscopy investigation of the Ca_1−xLn_xZrTi_2−x(Al, Fe)_xO₇ zirconolite ceramics (Ln = La, Nd, Gd, Ho, Yb)