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

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.