Electron paramagnetic resonance and optical absorption studies of irradiated lithium aluminate

Using electron paramagnetic resonance(EPR) and optical absorption measurements, defect creation is studied in irradiated single crystals of lithium aluminate, γ-LiAlO2. The EPR observations show the presence of several paramagnetic defects in γ-LiAlO2 irradiated with 2.5 MeV electrons at 20 K and X-rays at room temperature. The major defect includes an electron trapped near an aluminium nucleus. Optical absorption measurements show four bands in the spectra of γ-LiAlO2 irradiated with 2.5 MeV electrons at 20 K and with 2 MeV He+ ions at room temperature and 77 K. By analogy with other oxides, the most intense band (at 5.25 eV) may be assigned to F+-centres. With that assumption, a configuration is proposed for the F+-centre consistent with the EPR observations.