Investigation of Radiation Damage in the Monazite-Type Solid Solution La1-xCexPO4

Theresa Lender, Gabriel Murphy, Elena Bazarkina, Andrey Bukaemskiy, Sara Gilson, Maximilian Henkes, Christoph Hennig, Alexander Kaspor, Julien Marquardt, Jonas Nießen, Lars Peters, Jenna Poonoosamy, André Rossberg, Volodymyr Svitlyk, Kristina O. Kvashnina, Nina Huittinen

Research output: Contribution to journalArticlepeer-review

2 Scopus citations

Abstract

Crystalline materials such as monazite have been considered for the storage of radionuclides due to their favorable radiation stability. Understanding their structural chemical response to radiation damage as solid solutions is a key component of determining their suitability for radionuclide immobilization. Herein, high-resolution structural studies were performed on ceramics of the monazite solid solution La1-xCexPO4 (x = 0.25, 0.5, 0.75, 1) in order to understand the role of structural chemistry on irradiation stability. Ceramic samples were irradiated with 14 MeV Au ions with 1014 ions/cm2 and 1015 ions/cm2 to simulate the recoil of daughter nuclei from the alpha decay of actinide radionuclides. The extent of radiation damage was analyzed in detail using scanning electron microscopy (SEM), Raman spectroscopy, grazing incidence X-ray diffraction (GI-XRD), and high-energy-resolution fluorescence detection extended X-ray absorption fine structure (HERFD-EXAFS) spectroscopy. SEM and Raman spectroscopy revealed extensive structural damage as well as the importance of grain boundary regions, which appear to impede the propagation of defects. Both radiation-induced amorphization and recrystallization were studied by GI-XRD, highlighting the ability of monazite to remain crystalline at high fluences throughout the solid solution. Both, diffraction and HERFD-EXAFS experiments show that while atomic disorder is increased in irradiated samples compared to pristine ceramics, the short-range order was found to be largely preserved, facilitating recrystallization. However, the extent of recrystallization was found to be dependent on the solid solution composition. Particularly, the samples with uneven ratios of solute cations, La0.75Ce0.25PO4 and La0.25Ce0.75PO4 were observed to exhibit the least apparent radiation damage resistance. The findings of this work are discussed in the context of the monazite solid solution chemistry and their appropriateness for radionuclide immobilization.

Original languageEnglish
Pages (from-to)17525-17535
Number of pages11
JournalInorganic Chemistry
Volume63
Issue number38
DOIs
StatePublished - Sep 23 2024
Externally publishedYes

Funding

The idea for this study originates from FZJ-IFN2. We gratefully acknowledge the BMBF for funding through grant number 02NUK060. The BMBF played no role in study design, data collection, analysis and interpretation of data, or the writing of this manuscript. We also thank the Ion Beam Center, HZDR for irradiations. GI-XRD and XAS measurements were performed at the ROBL beamline at ESRF under the proposal numbers A20-1-839 and A20-1-843, respectively. The authors thank the FAME beamline at ESRF for providing the Ge(331) crystals for this study.

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