Structural characterization of Nd-doped Hf-zirconolite Ca1−xNdxHfTi2−xAlxO7 ceramics

Caurant, Daniel; Loiseau, Pascal; Bardez, I.

doi:10.1016/j.jnucmat.2010.09.033

Cited by 43 publications

(30 citation statements)

References 69 publications

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“…35,36 Previous studies have demonstrated that zirconolite can immobilise both actinides and fission products in the crystal lattice for the long term. 37,38 Zirconolite refers specifically to CaZrTi2O7, which has a monoclinic structure (space group C2/c). The zirconolite crystal structure forms a monoclinic system that is made up layers of TiO6 and TiO5 polyhedra with Ca 2+ (8 coordinate) and Zr 4+ (7 coordinate) ions located in the large interstitial sites between these layers (Figure 1b).…”

Section: Introductionmentioning

confidence: 99%

Investigation of the stability of glass-ceramic composites containing CeTi2O6 and CaZrTi2O7 after ion implantation

Paknahad

Grosvenor

2017

Solid State Sciences

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Glass-ceramic composite materials are being investigated for numerous applications (i.e. textile, energy storage, nuclear waste immobilization applications, etc.) due to the chemical durability and flexibility of these materials. Borosilicate and Fe-Al-borosilicate glass-ceramic composites containing brannerite (CeTi2O6) or zirconolite (CaZrTi2O7) crystallites were synthesized at different annealing temperatures. The objective of this study was to understand the interaction of brannerite or zirconolite-type crystallites within the glass matrix and to investigate how the local structure of these composite materials changed with changing synthesis conditions. Powder Xray diffraction (XRD) and Backscattered electron (BSE) microprobe images have been used to study how the ceramic crystallites dispersed in the glass matrix. X-ray absorption near edge spectroscopy (XANES) spectra were also collected from all glass-ceramic composite materials. Examination of Ti K-, Ce L3-, Zr K-, Si L2,3-, Fe K-, and Al L2,3-edge XANES spectra from the glass-ceramic composites have shown that the annealing temperature, glass composition, and the loading of the ceramic crystallites in the glass matrix can affect the local environment of the glass-ceramic composite materials. A comparison of the glass-ceramic composites containing brannerite or zirconolite crystallites has shown that similar changes in the long-range and local structure of these composite materials occur when the synthesis conditions to form these materials or the composition are changed.

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Section: Introductionmentioning

confidence: 99%

Investigation of the stability of glass-ceramic composites containing CeTi2O6 and CaZrTi2O7 after ion implantation

Paknahad

Grosvenor

2017

Solid State Sciences

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“…8,9 Synthetic analogues of natural zirconolite, based on the formula CaZrTi 2 O 7 , target substitution of trivalent and tetravalent actinides and lanthanide fission products on the Ca and Zr sites based on the comparable ionic radii of these species, with charge compensation introduced on the Ti site as necessary. [10][11][12][13][14][15] Actinide species incorporated within host crystalline lattices undergo alpha decay processes resulting in substantial structural damage that may eventually result in a radiation amorphized or "metamict" material as reviewed by Weber et al 16 For example, α-decay of Pu-239 affords an energetic (5.2 MeV) α-particle and a U--particle deposits its energy in ionisation processes causing relatively few atomic displacements, but recoil of the daughter atom produces 10 3 atomic displacements through ballistic collisions, within a 10 2 nm cascade. 16 Defect accumulation and cascade overlap eventually result in amorphization of the initially crystalline host material.…”

Section: Introductionmentioning

confidence: 99%

Structural Transformations and Disordering in Zirconolite (CaZrTi₂O₇) at High Pressure

et al. 2013

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Abstract:There is interest in identifying novel materials for use in radioactive waste applications and studying their behavior under high pressure conditions. The mineral zirconolite (CaZrTi 2 O 7 ) exists naturally in trace amounts in diamond-bearing deep-seated metamorphic/igneous environments, and it is also identified as a potential ceramic phase for radionuclide sequestration. However, it has been shown to undergo radiation-induced metamictization resulting in amorphous forms. In this study we probed the high pressure structural properties of this pyrochlore-like structure to study its phase transformations and possible amorphization behavior. Combined synchrotron X-ray diffraction and Raman spectroscopy studies reveal a series of high pressure phase transformations. Starting from the ambient pressure monoclinic structure an intermediate phase with P2 1 /m symmetry is produced above 15.6 GPa via a first order transformation resulting in a wide coexistence range. Upon compression to above 56 GPa a disordered metastable phase III with a cotunnite-related structure appears that is recoverable to ambient conditions. We examine the similarity between the zirconolite behavior and the structural evolution of analogous pyrochlore systems under pressure.

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“…The reported structural details of monoclinic zirconolite were utilized as the initial model for Rietveld refinement of the powder XRD data. 32 The refined structural parameter fits greatly well with the 2M-zirconolite phase, whose PDF number is 84-0163 from the Internation Centre for Diffraction Data (ICDD) with molecular formula written as CaZr x Ti 3-x O 7 . The refined unit cell parameters are: a = 12.4514 A, b = 7.2607 A, c = 11.3817 A, and b = 100.5804°.…”

Section: Resultsmentioning

confidence: 67%

“…The phase composition was intensively characterized using XRD Rietveld refinement with the results shown in Figure . The reported structural details of monoclinic zirconolite were utilized as the initial model for Rietveld refinement of the powder XRD data . The refined structural parameter fits greatly well with the 2M‐zirconolite phase, whose PDF number is 84‐0163 from the Internation Centre for Diffraction Data (ICDD) with molecular formula written as CaZr x Ti 3‐x O 7 .…”

Section: Resultsmentioning

confidence: 94%

Two‐step synthesis of zirconolite‐rich ceramic waste matrice and its physicochemical properties

Zhang

Yin

Han

et al. 2017

Int J Applied Ceramic Tech

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In this study, the synthesis of single-phase zirconolite powder was explored using two-step route of combustion synthesis (CS) plus acid treatment. Zirconolite/Cu composite was firstly produced from the combustion reaction using CuO and Ti as the oxidant and reductant. After pickling and desiccation, refined zirconoliterich ceramic powder was obtained with bimodal particle size distribution. The ceramic powder was finally preformed and calcined at 1050-1300°C for 6-48 hours, which resulted in bulk density and Vickers hardness of 4.02 g/cm 3 and 11.54 GPa after sintering at 1100°C for 18 hours. Aqueous durability of the calcined waste matrice was evaluated according to MCC-1 standard. The 42 days normalized leaching rates of Ca, Ti and Zr were measured to be 3.96 9 10 À3 , 4.52 9 10 À6 and 1.54 9 10 À6 gÁm À2 Ád À1 . K E Y W O R D Schemical durability, combustion synthesis, nuclear waste, sintering

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Structural characterization of Nd-doped Hf-zirconolite Ca1−xNdxHfTi2−xAlxO7 ceramics

Cited by 43 publications

References 69 publications

Investigation of the stability of glass-ceramic composites containing CeTi2O6 and CaZrTi2O7 after ion implantation

Investigation of the stability of glass-ceramic composites containing CeTi2O6 and CaZrTi2O7 after ion implantation

Structural Transformations and Disordering in Zirconolite (CaZrTi₂O₇) at High Pressure

Two‐step synthesis of zirconolite‐rich ceramic waste matrice and its physicochemical properties

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Structural characterization of Nd-doped Hf-zirconolite Ca1−xNdxHfTi2−xAlxO7 ceramics

Cited by 43 publications

References 69 publications

Investigation of the stability of glass-ceramic composites containing CeTi2O6 and CaZrTi2O7 after ion implantation

Investigation of the stability of glass-ceramic composites containing CeTi2O6 and CaZrTi2O7 after ion implantation

Structural Transformations and Disordering in Zirconolite (CaZrTi2O7) at High Pressure

Two‐step synthesis of zirconolite‐rich ceramic waste matrice and its physicochemical properties

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Structural Transformations and Disordering in Zirconolite (CaZrTi₂O₇) at High Pressure