Luminescence of F⁺ and F centers in AI₂O₃-Y₂O₃ oxide compounds

We summarize the results of investigation of spectral-kinetic characteristics of the luminescence of F⁺ and F-centers in Al₂O₃, YAlO₃ (YAP) and Y₃Al₅O₁₂ (YAG) crystals under excitation by synchrotron radiation in the transmittance and fundamental absorption ranges of these oxides. We show that the luminescence of F⁺ and F centers in the mentioned crystals can be excited via the corresponding intrinsic 1A→2A, 2B and 3P (F⁺) and ¹S→³P, ¹P (F) transitions of these centers, as well as via the radiative relaxation of excitons localized around F⁺ and F centers. In YAG crystal fast (2.3 ns) emission in the 400 nm band, excited at 3.33, 5.37 and 6.56 eV, arises from the F⁺-type centers, localized around Y_Al antisite defects (ADs). In Al₂O₃ and YAP crystals, the luminescence of excitons localized around F⁺ centers (LE(F⁺) centers) is revealed and the energies of formation of such excitons are determined as well. In YAG crystal the observation of the luminescence of LE(F⁺) centers is obscured due to presence of the large content (∼0.2 at.%) of Y_Al ADs and formation of an excitons localized around Y_Al ADs and dimer F⁺-ADs centers.