Crystalline solid-state oxides that exhibit resistance to radiation-induced structural damage are being considered as materials for the immobilization of waste actinide elements. In this regard, compounds adopting the monazite (REPO4; RE = La to Gd) or xenotime (RE′PO4; RE′ = Tb to Lu and Y) structures are being investigated for this application. Both of these structures coexist in natural samples which leads to the formation of solid solutions. In this study, multiple series of solid solutions (La1–x Yb x PO4, La1–x Y x PO4, and Sm1–x Ho x PO4) were synthesized and investigated by powder X-ray diffraction, X-ray absorption near-edge spectroscopy (XANES), and X-ray photoelectron spectroscopy (XPS). XANES and XPS were performed to examine the influence of crystal structure on spectra. Examination of P K- and P L2,3-edge XANES spectra indicated that a positive shift in absorption energy and change in line shape occur with an increase in the concentration of xenotime structure. Analysis of Sm and Ho M5-edge XANES spectra showed that the spectral intensity changes because of a charge-transfer mechanism. The XPS spectra exhibited only a minor shift in binding energy depending on the structure. It has been established in this study that XANES can distinguish between samples that adopt the monazite or xenotime structure.

Synthetic analogues of naturally occurring monazite (REPO4; RE = La to Gd) and xenotime (RE'PO4; RE' = Tb to Lu and Y) minerals have been identified as potential wasteforms for nuclear waste. High energy ion-implantation of crystalline materials simulates radiation-induced structural damage and allows for the radiation resistance of a crystal structure to be probed. The structural stability of Auion-implanted La1-xYbxPO4 materials was investigated using micro-Xray diffraction (µ-XRD) and glancing angle X-ray absorption near-edge spectroscopy (GA-XANES) in this study. The long-and short-range order of La1-xYbxPO4 (x = 0, 0.3, 0.7, 1.0) is affected by ion-implantation and, thus, the materials are prone to structural damage. The structures of some members of the La1-xYbxPO4 series (x = 0.7 and 1.0) were observed to partially recover after being implanted with Auions to a high dose. The structures of all members of the La1-xYbxPO4 series were observed to recover from damage resulting from ionimplantation after annealing the materials at temperatures ≥300°C.

HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.