Preparation and luminescence characterization of Cu-doped lithium aluminate ceramics within the Li2O-Al2O3 system

Cu + -doped lithium aluminates with LiAlO 2 , LiAl 5 O 8 , and Li 5 AlO 4 stoichiometry were investigated. Tetragonal γ -LiAlO 2 and cubic α -LiAl 5 O 8 were prepared in the form of bulk ceramics using the Pechini sol–gel route with Cu-doping concentrations up to 1 mol%. For γ -LiAlO 2 , single-phase samples were obtained only for the lowest doping concentration tested, which was 0.1 mol%, while α -LiAl 5 O 8 samples were single phase within the full concentration series. Radioluminescence and photoluminescence of Cu-doped γ -LiAlO 2 featured only the transition from 3d 9 4s 1 to 3d 10 corresponding to Cu + ions. On the other hand, Cu-doped α -LiAl 5 O 8 samples showed mainly emissions associated with Fe 3+ and Cr 3+ impurities with overall very small intensity compared to the reference BGO scintillator. Samples of Cu-doped β -Li 5 AlO 4 were prepared using a nitrates decomposition method. Due to the volatility of Li 2 O, the samples were not in a single phase and contained a certain amount of secondary γ -LiAlO 2 phase, even though excess lithium was used for the sample preparation. Furthermore, samples with β -Li 5 AlO 4 exhibited strong hygroscopic properties, making Li 5 AlO 4 an undesirable host material outside of a controlled atmosphere environment. The graphical abstract shows the unit cells of the three lithium aluminate hosts investigated in this work, along with X-ray excited radioluminescence spectra obtained by doping copper into the γ -LiAlO 2 and α -LiAl 5 O 8 hosts. Highlights Single-phase samples of copper-doped γ -LiAlO 2 and α -LiAl 5 O 8 were obtained by the sol–gel method. The Cu:LiAlO 2 samples showed a single emission band, caused by a radiative transition of Cu + ions. The Cu:LiAl 5 O 8 samples exhibited mainly low-intensity emission of undesired impurities. The Cu:Li 5 AlO 4 samples contained a secondary γ -LiAlO 2 phase and were highly hygroscopic.