5d–4f and 4f–4f emissions in Ln-doped sesquioxide ceramics

► We performed synthesis of transparent rare earth doped mixed oxides. ► We described criteria for Pr ( 1D 2 level) or Pr ( 3P 0 level) emission. ► Energy level positions for the host and the C 2 and S 6 sites. ► Description of how energy level positions influence the lanthanides emission. In this study, various lanthanide and mixed lanthanide oxides (Ln 2O 3 with Ln = La, Lu, Lu 0.5Gd 0.5) powders have been synthesized by a coprecipitation method. The luminescence properties and/or the quenching mechanisms of different dopants (europium, cerium, praseodymium) have been studied. Luminescence mechanisms of Ce:Ln 2O 3 and Pr:Ln 2O 3, are closely related to the 5d and 4f energy levels positions of the dopant versus materials bandgap and crossing effect between dopant energy levels. Energy level positions have been analyzed through optical spectroscopy and their effect on the luminescence is presented. Eu:Lu 2O 3 and Eu:LuGdO 3 have also been prepared as transparent ceramics and radioluminescence properties are presented.