Irradiated rare‐earth‐doped powellite single crystal probed by confocal Raman mapping and transmission electron microscopy

Abstract

The irradiation‐induced damages and structure modifications of rare earths doped powellite single crystal have been precisely studied using optical and electron microscopy techniques, including optical interferometry, confocal micro‐Raman spectroscopy and transmission electron microscopy. The surface of powellite crystal pops out anisotropically after exposing under Ar ion beam, with a saturation swelling value of 2.0% along a‐axis and 1.3% along the c‐axis of powellite at high dose. Raman mapping on focused ion‐beam sections (5 × 3 µm2) perpendicular to the irradiated surface reveals that irradiation damage induces orientation‐dependent compressive stresses in powellite. However, no significant anisotropic effect has been found on the irradiation‐induced structural disorder in powellite. At low dose (0.012 dpa), the main irradiation‐induced defects created in powellite crystal are small defect clusters. By comparison, the dominant kinds of defects in high‐dose (5.0 dpa) sample are dislocations loops and networks. Copyright © 2014 John Wiley & Sons, Ltd.

Impacts of composition and beta irradiation on phase separation in multiphase amorphous calcium borosilicates

“…As previously mentioned, the fabrication process causes the cell parameters to be higher than single crystals, which irradiation aids in remediating. CaMoO 4 as a single crystal has been previously observed stable against amorphization following Ar-irradiation, which created 5 dpa of structural modifications [48] and low energy electron irradiation produced through in-situ TEM [70]. This study proves that CaMoO 4 is also stable with minimal alteration in a calcium borosilicate for up to 1.34 GGy of β-irradiation, though crystals may migrate through the surrounding amorphous network.…”

“…In contrast to the broad bands of the amorphous phase indicating structural disorder, the crystalline phase powellite with C 4h point symmetry exhibits several sharp peaks. These peaks are assigned to the lattice vibrations for internal (MoO 4 ) 2 − modes in powellite and are as [48]. These modes represent symmetric elongation of the molybdenum tetrahedron, asymmetrical translation of double degenerate modes, symmetric and asymmetrical bending, respectively [49].…”

Irradiation effects in CaF2 probed by Raman scattering

“…This is the case for, e.g. (Mg,Fe) 2 Al 4 Si 5 O 18 , Gd 2 Ti 2 O 7 , Gd 2 TiZrO 7 , CaMoO 4 and Ca 5 (PO 4 ) 3 F . For moderate and high resistance materials, the initially active modes of pristine samples do not completely disappear during irradiation, but additional modes are usually observed.…”

“…The high sensitivity of Raman spectroscopy allows us to evaluate the stability of radiation damage under exposure to lasers of different wavelengths. Additionally, its high spacial resolution allows us to profile the irradiation‐induced modifications as a function of depth . Furthermore, it also allows us to investigate heavily irradiated CaF 2 samples, where UV‐visible optical absorption is rather limited because of the strong enhancement of Mie scattering caused by the presence of a large amount of Ca colloids.…”

Swift heavy ion-irradiated multi-phase calcium borosilicates: implications to molybdenum incorporation, microstructure, and network topology

“…The bottom spectrum of each regional collection represents a pristine sample after which irradiated samples with increasing fluence (5 9 10 12 , 1 9 10 13 , spectra of phase A in Fig. 9, which also shows that growth of the D 1 and D 2 defect bands is more prevalent for low [ [61]. These modes represent symmetric elongation of the molybdenum tetrahedron, asymmetrical translation of double degenerate modes, and symmetric and asymmetrical bending, respectively [62].…”