Comparison of Luminescence in LiGaO₂, Al₂O₃-Ga and Al₂O₃-Li Crystals

We have studied luminescence of LiGaO₂, Al₂O₃-Ga and Al₂O₃-Li crystals in order to reveal the nature of luminescence centres and mechanisms in these crystals. In Al₂O₃-Ga presence of Ga impurities determines occurrence of the 280 nm emission band, which demonstrates intra-centre character in photoluminescence and recombination character under X-ray irradiation. In Al₂O₃-Li crystal lithium induced luminescence is presented with the 326 nm band, which has a recombination character. Basing on spectral similarity of the main luminescence bands in pure LiGaO₂ crystal with the dopant-induced emission bands in Al₂O₃, and on peculiarities of the X-ray induced thermoluminescence, the adjustment of the previous luminescence interpretation is done. It is proposed that the donor-acceptor pairs with random separation distribution responsible for the 280 nm emission are represented with gallium Ga (plus an electron) and O (plus a hole) pairs, while the donor-acceptor pairs, producing the 330 nm emission band contain a lithium ion, presumably in the interstitial position Li_i⁰, and a neighbouring oxygen ion with a caught hole.