Improved scintillation time response in (Lu0.5Gd0.5)2O3:Eu3+ compared with Lu2O3:Eu3+ transparent ceramics

The scintillation properties of two sesquioxides ceramics Lu2O3 : Eu3+ and (Lu0.5Gd0.5)(2)O-3 : Eu3+ were studied. Both ceramics present comparable transparency and light yield whereas (Lu0.5Gd0.5)(2)O-3 : Eu3+ showed an order of magnitude reduced afterglow in the 3-300 ms range. A thorough study of the location and behaviour of Eu3+ dopant ions at C-2 and S-6 sites of Lu2O3 and (Lu0.5Gd0.5)(2)O-3 structures was carried out with low-temperature selective excitation of Eu3+. This revealed that (i) at both C-2 and S-6 sites, Eu3+ 4f-4f lifetime is shorter in (Lu0.5Gd0.5)(2)O-3 : Eu3+ than in Lu2O3 : Eu3+, (ii) the host matrix (Lu0.5Gd0.5)(2)O-3 as compared with Lu2O3 favours the location of Eu3+ at C-2 site. As decay times of Eu3+ in C-2 and S-6 sites are 1.0 ms and 3.8 ms, respectively, the preferred occupation of C-2 in (Lu0.5Gd0.5)(2)O-3 : Eu3+ implies a much shorter decay time for (Lu0.5Gd0.5)(2)O-3 : Eu3+ in the 3-20 ms range. Reduction of afterglow in the 20-300 ms range is illustrated by thermally stimulated luminescence peaks presenting a highly reduced intensity for (Lu0.5Gd0.5)(2)O-3 : Eu3+ compared with Lu2O3 : Eu3+ implying reduced charge trapping defects in (Lu0.5Gd0.5)(2)O-3 : Eu3+ ceramics.