Optical, scintillation and luminescent properties of lithium aluminate crystals activated with transition-metal ions

Optical, scintillation and luminescent properties of 0.1% Ti-, Mn- and Cu- doped lithium aluminate LiAlO₂ crystals are studied. The crystals were grown by micro-pulling down (μ-PD) method under N₂ + O₂ (2 vol %) atmosphere. By the X-ray excitation, the crystals exhibited intense emission bands at ultraviolet-visible regions which can be attributed to the Ti⁴⁺-O^2- charge transfer transition at 380 nm, ⁴T¹ → ⁶A₁ transition of Mn²⁺ ion at 550 nm and 3d⁹4s-3d¹⁰ transition of Cu⁺ at 360 nm, respectively. The scintillation decay time were estimated to be about 1.8 and 9.9 μs for Ti 0.1%, 310 μs and 2240 μs for Mn 0.1%, and 3.6 μs and 19.6 μs for Cu 0.1%. When ²⁵²Cf neutron irradiated the crystals, the relative scintillation light output found to be approximately (135 ± 13) × 10² ph/n (for Ti 0.1%) and (87 ± 8.0) × 10² ph/n (for Cu 0.1%) compared to that of GS20 commercial scintillator. Both TL and OSL spectra showed emission bands caused by the recombines of trapped electrons at the anion centers through the Ti⁴⁺, Mn²⁺ and Cu⁺ luminescence centers. The irradiation dose response was linear in the studied dose range at 0.1-5 Gy and 0.1-10 Gy.