Impact of rare earth ion size on the phase evolution of MoO3-containing aluminoborosilicate glass-ceramics
| Autor: | Manisha Konale, Mathew Gabel, Neil C. Hyatt, Ashutosh Goel, Jarrod V. Crum, Owen K. Neill, Deepak Patil, Martin C. Stennett, John S. McCloy |
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| Rok vydání: | 2018 |
| Předmět: |
010302 applied physics
Nuclear and High Energy Physics X-ray absorption spectroscopy Materials science Glass-ceramic Analytical chemistry Ionic bonding chemistry.chemical_element 02 engineering and technology 021001 nanoscience & nanotechnology Alkali metal 01 natural sciences Amorphous solid law.invention Nuclear Energy and Engineering chemistry law 0103 physical sciences General Materials Science Crystallization 0210 nano-technology Boron Powellite |
| Zdroj: | Journal of Nuclear Materials. 510:539-550 |
| ISSN: | 0022-3115 |
| DOI: | 10.1016/j.jnucmat.2018.08.004 |
| Popis: | Transition metal and rare earth (RE) elements are important fission products present in used nuclear fuel, which in high concentrations tend to precipitate crystalline phases in vitreous nuclear waste forms. Two phases of particular interest are powellite (CaMoO4) and oxyapatite (Ca2RE8(SiO4)6O2). The glass compositional dependencies controlling crystallization of these phases on cooling from the melt are poorly understood. In the present study, the effect of rare earth identity and modifier cation field strength on powellite and apatite crystallization were studied in a model MoO3-containing alkali/alkaline-earth aluminoborosilicate glass with focus on (1) influence of rare earth cation size (for RE3+: Ce, La, Nd, Sm, Er, Yb) and (2) influence of non-framework cations (RE3+, Mo6+, Na+, Ca2+). Quenched glasses and glass-ceramics (obtained by slow cooling) were characterized by X-ray diffraction (XRD), Raman spectroscopy, X-ray absorption spectroscopy (XAS), and electron probe microanalysis (EPMA). All samples were X-ray amorphous upon quenching, except the Ce-containing composition which crystallized ceria (CeO2), and the sample devoid of any rare earth cations which crystallized powellite. On heat treatment, powellite and oxyapatite crystallized in the majority of the samples, with the former crystallizing in the volume and the latter on the surface. The EPMA results confirmed a small concentration of boron in the oxyapatite crystal structure. RE cations were incorporated in the glass, as well as in powellite, oxyapatite, and in the case of Yb3+, keiviite (Yb2Si2O7). Raman spectroscopy showed that the primary vibration band for molybdate MoO42− in the glasses was strongly affected by the ionic field strength of the modifying cations (alkali, alkaline earth, and RE), suggesting their proximity to the MoO42− ions in the glass, though the Mo O bond length and coordination according to XAS suggested little local change. |
| Databáze: | OpenAIRE |
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