Radiation resistance of synthetic sapphire crystal irradiated by low‐energy neutron flux

Abstract

In this paper, high‐quality sapphire crystal grown by an improved Kyropoulos‐like method, was irradiated by low‐energy neutron (i.e. high proportion of thermal neutron) with various flux (low: 7.5×1015 n/cm2, medium: 7.0×1016 n/cm2 and high: 3.8×1017 n/cm2). The characteristic features of neutron fluence dependence of radiation‐defect formation process, mainly including its change of the structural and optical properties prior to and after irradiation, were investigated by optical absorption (OA), photoluminescence (PL), electron paramagnetic resonance (EPR) and positron annihilation spectroscopy (PAS). It is found that sapphire crystal exhibits high radiation resistance to low‐energy neutron with low fluence. But with the increase of irradiation fluence, it is still sensitive to neutron irradiation mostly in the UV‐visible spectral range, as irradiation‐induced color centers appear, including F‐type and their aggregate centers. Finally, the formation mechanism of the irradiation defects is also discussed. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Electron paramagnetic resonance in gamma-ray, electron and neutron flux irradiated sapphire

“…It can be deduced that the Cr 3+ impurity is barely found from the EPR spectroscopy, which is consistent with the previous PIXE result in Ref. [9]. The position and intensity of EPR signal in sapphire before and after irradiation are shown in Fig.…”

“…Radiation effects of sapphire do not depend only on irradiation conditions, but they are dependent also on its chemical composition and preparation process [9,18]. However, the identification of the defects in sapphire is not clear [19].…”

“…Sapphire is widely used in aerospace optical environment because of its excellent thermal shock resistance, great mechanical properties, low scattering, and superior high-temperature infrared properties [4][5][6][7]. So, it is indispensable for knowledge of its service performance under various space-radiation environments [8,9]. Radiation and spectral characteristics of sapphire produced by various methods have been studied [10][11][12].…”

Metallic Nano Particles Embedded in Sapphire

“…The ion fluences used along this paper are high enough to reach a dynamical equilibrium between defect production and recombination. It is also relevant to notice that the maximum luminescence occurs at the excitation wavelength corresponding to the absorption band of the center, as can be compared from the values reported in table 1 [13]. Absorption spectra show a strong increase in the overall background and also the small signal from the F + bands.…”

“…That means that these optical effects after implantation are understood in terms of the sapphire matrix alone and not to new bands due to the introduction of impurities. There is also an important difference with the results found with high energy ions [14] and gamma radiation [13]. In those cases, F centers are the most common kinds of defects found.…”