Fabrication and VUV luminescence of Lu2O3:Eu3+ (5 at.%) nanopowders and transparent ceramics

Low-agglomerated Lu$_2$O$_3$:Eu$³⁺$ 5 at.% nanopowders, as well as transparent ceramics were fabricated by co-precipitation with ammonium hydrogen carbonate and vacuum sintering method, respectively. It was determined that transition of a part of europium ions into the divalent state enhanced sinterability due to formation of anionic vacancies and decrease of the RE-O bonds covalency. The luminescent properties of the Lu$_2$O$_3$:Eu$³⁺$ 5 at.% nanopowders and ceramics were studied under excitation by synchrotron radiation. The difference in the excitation spectra of Lu$_2$O$_3$:Eu$³⁺$ nanopowders and ceramics are caused by participation of the F$^+$ centers in the excitation processes of Eu$³⁺$ luminescence in Lu$_2$O$_3$ host. Finally, the locations of the energy levels related to the Eu$³⁺$ dopant in Lu$_2$O$_3$ matrix were determined.