Impact of rare earth ion size on the phase evolution of MoO3-containing aluminoborosilicate glass-ceramics
- Washington State Univ., Pullman, WA (United States)
- Washington State Univ., Pullman, WA (United States); Univ. of Pardubice (Czech Republic)
- Univ. of Michigan, Ann Arbor, MI (United States)
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
- Rutgers Univ., Piscataway, NJ (United States)
- Univ. of Sheffield (United Kingdom)
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Washington State Univ., Pullman, WA (United States)
Transition metal and rare earth cations 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 (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 (CaMoO4). On heat treatment, powellite and oxyapatite crystallized in the majority of the samples with the former crystallizing in the volume, while 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 MoO4 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 MoO4 ions in the glass, though the Mo O bond length and coordination according to XAS suggested little local change.
- Research Organization:
- Pacific Northwest National Laboratory (PNNL), Richland, WA (United States); Washington State Univ., Pullman, WA (United States)
- Sponsoring Organization:
- USDOE Office of Nuclear Energy (NE)
- Contributing Organization:
- Univ. of Sheffield (United Kingdom)
- Grant/Contract Number:
- NE0008431; AC0576RL01830; AC05-76RL01830
- OSTI ID:
- 1465748
- Alternate ID(s):
- OSTI ID: 1485493; OSTI ID: 1512399; OSTI ID: 1703234
- Report Number(s):
- PNNL-SA-137055; PII: S0022311518302514; TRN: US1902546
- Journal Information:
- Journal of Nuclear Materials, Vol. 510; ISSN 0022-3115
- Publisher:
- ElsevierCopyright Statement
- Country of Publication:
- United States
- Language:
- English
Web of Science
Crystallization study of rare earth and molybdenum containing nuclear waste glass ceramics
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journal | January 2020 |
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