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Color-center formation in x-ray and electron-irradiated magnesium aluminate spinel

Abstract : We have studied the formation of color centers in magnesium aluminate spinel (MgAl2O4) by X-ray and electron irradiations near room temperature (RT). For this purpose, CuKet61537; radiation and three electron energies (1.0, 1.4, and 2.5 MeV) were used for variable fluences (up to 4.2x1018 cm-2). Off-line UV-visible optical absorption spectra were recorded at RT. Low temperature measurements down to 27 K were also carried out off line after electron irradiation. The dependence of the production rate of F0 centers (neutral oxygen vacancies) on the electron energy yields a threshold displacement energy for oxygen atoms of 190 et61617; 10 eV at RT, that is much higher than the determinations by molecular-dynamics simulations. Such a discrepancy is discussed on the basis of available migration data of point defects in spinel. Moreover, the evolution of the width of color-center absorption bands versus temperature from 27 K to 250 K is interpreted with the classical theory for F centers (neutral halogen vacancies) in alkali halides. Large Stokes shifts like for the alkaline-earth oxides are deduced from the temperature dependence of the absorption band widths of color centers.
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https://hal-cea.archives-ouvertes.fr/cea-02339818
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Submitted on : Wednesday, October 30, 2019 - 3:30:22 PM
Last modification on : Monday, September 7, 2020 - 11:44:04 AM

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Jm. Costantini, G. Lelong, M. Guillaumet, S. Takaki, K. Yasuda. Color-center formation in x-ray and electron-irradiated magnesium aluminate spinel. Journal of Applied Physics, American Institute of Physics, 2018, 124, ⟨10.1063/1.5055230⟩. ⟨cea-02339818⟩

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