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Rare-Earth Orthophosphates: Advanced Applications

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Front. Chem. | doi: 10.3389/fchem.2019.00013

The quantification of radiation damage in orthophosphates using confocal µ-luminescence spectroscopy of Nd3+

 Christoph Lenz1, 2*,  Gordon Thorogood2,  Robert Aughterson2, Mihail Ionescu2, Daniel Gregg2, Joel Davis2 and  Gregory R. Lumpkin2
  • 1Institute of Mineralogy and Crystallography, Faculty of Geosciences, Geography and Astronomy, University of Vienna, Austria
  • 2Australian Nuclear Science and Technology Organisation, Australia

In this study, we present a new concept based on the steady-state, laser-induced photoluminescence of Nd3+, which aims at a direct determination of the amorphous fraction fa in monazite- and xenotime-type orthophosphates on a micrometer scale. Poly-crystalline, cold-pressed, sintered LaPO4 and YPO4 ceramics were exposed to quadruple Au-ion irradiation with ion energies 35 MeV (50% of the respective total fluence), 22 MeV (21%), 14 MeV (16%), and 7 MeV (13%). Total irradiation fluences were varied in the range 1.6×1013 − 6.5 ×1013 ions/cm2. Ion-irradiation resulted in amorphization and damage accumulation unto a depth of ~ 5 µm below the irradiated surfaces. The amorphous fraction created was quantified by means of surface-sensitive grazing-incidence X-ray diffraction and photoluminescence spectroscopy using state-of-the-art confocal spectrometers with spatial resolution in the μm range. Monazite-type LaPO4 was found to be more susceptible to ion-irradiation induced damage accumulation than xenotime-type YPO4. Transmission electron microscopy of lamella cut from irradiated surfaces with the focused-ion beam technique confirmed damage depth-profiles with those obtained from PL hyperspectral mapping. Potential analytical advantages that arise from an improved characterization and quantification of radiation damage (i.e., fa) on the µm-scale are discussed.

Keywords: xenotime YPO4, monazite LaPO4, rare earth elements REEs, Radiation damage and others irradiation effects, Amorphous fraction, Luminescence spectroscopy, Grazing-incidence X-ray diffraction (GI-XRD), Transmission electron microscopy, nuclear waste form materials

Received: 28 Oct 2018; Accepted: 07 Jan 2019.

Edited by:

Adel Mesbah, UMR5257 Institut de Chimie Séparative de Marcoule (ICSM), France

Reviewed by:

Edison Pecoraro, São Paulo State University, Brazil
Roberto Nisticò, Politecnico di Torino, Italy  

Copyright: © 2019 Lenz, Thorogood, Aughterson, Ionescu, Gregg, Davis and Lumpkin. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Dr. Christoph Lenz, Institute of Mineralogy and Crystallography, Faculty of Geosciences, Geography and Astronomy, University of Vienna, Vienna, Austria, christoph.lenz@univie.ac.at