Optical characteristics of virgin and proton-irradiated ceramics of magnesium aluminate spinel

• Published in: Optical materials 2019-10, Vol.96, p.109308, Article 109308
• Main Authors: Feldbach, Eduard, Kudryavtseva, Irina, Mizohata, Kenichiro, Prieditis, Gatis, Räisänen, Jyrki, Shablonin, Evgeni, Lushchik, Aleksandr
• Format: Article
• Language: English
• Subjects: Cathodo- and photoluminescence; Intrinsic excitations; Magnesium aluminate spinel; Optical absorption; Proton irradiation; Structural defects
• ISSN: 0925-3467; 1873-1252
• DOI: 10.1016/j.optmat.2019.109308

Intrinsic properties of optical ceramics of MgAl2O4 have been studied by means of low-temperature cathodo-, photo- and thermo-luminescence methods. Based on the excitation spectra for different emissions measured at 6 K, the UV luminescence at 4.5–5.8 eV is tentatively ascribed to bound excitons (formation energy about 7 eV) near antisite defects (cation in a “wrong” position) and electron-hole recombination in a spinel matrix. The complex UV luminescence band peaked around 5 eV undergoes thermal quenching from 6 to 200 K. The value of energy gap is experimentally estimated as 8.2 eV at 80 K. There is no saturation of the absorption connected with the radiation-induced F-type color centers at the rise of 100-keV proton fluence up to 7 × 1017 cm−2, while such irradiation is accompanied by the drastic suppression of cathodoluminescence, especially in UV spectral region. A further study of the origin of this luminescence attenuation still lies ahead. •The intrinsic origin of the emission band at 4.5–5.8 eV was experimentally confirmed.•Bound excitons near ADs and other defects are formed by 6.8–7.4 eV photons at 6 K.•The energy gap in MgAl2O4 was estimated via luminescent methods as 8.2 eV at 80 K.•Dependence of radiation damage on proton fluence in MgAl2O4 ceramics was analysed.•The UV band of CL undergoes strong attenuation with the proton irradiation fluence.