Spectra Analysis of a Novel Ti-Doped LiAlO₂ Single Crystal

LiAlO₂ single crystals doped with Ti at concentration 0.2 at.% are grown by the Czochralskl technique with dimensions Ф42×55mm. Ti ions in the crystal are quadrivalence proven by comparing the absorption and fluorescence spectra of pure LiAlO₂ and Ti: LiAlO₂. After air and Li-rich atmosphere annealing, the absorption peaks in the range of 600--800nm disappear. We conclude that 682 and 756nm absorption peaks are attributed to the V_Li and V₀ absorptions, respectively. The peaks at 716nm and 798nm may stem from the V_Li⁺ and F⁺ absorptions. The colour-centre model can be applied to explain the experimental phenomena. Ti⁴⁺-doping produces more lithium vacancies in the LiAlO₂ crystal. The intensities of LiO₄ and the associated bonds remain unchanged, which improves the anti-hydrolyzation and thermal stability of LiAlO₂ crystals.