Funct. Mater. 2014; 21 (4): 498-502.
Energy transfer in co-doped NaI:(Tl,Eu) crystals
[1] Institute for Scintillation Materials, 60 Lenin Avenue, 61001 Kharkov, Ukraine
[2] Institut Lumiere Matiere, Universite Claude Bernard Lyon 1, 69622 Villeurbanne Cedex, France
The energy transfer mechanism in Eu doped and Tl, Eu co-doped NaI crystals is discussed. The self-trapped exciton emission band overlaps stronger with Eu2+ excitation bands rather that with Tl+. This suggests that transfer STE -> Activator can be more efficient in Eu2+ co-doped NaI:Tl crystals. Theoretical estimation of energy transfer efficiency was done based on the Forster model. It is shown that Europium concentration of 1 mass% or above is required for efficient dipole-dipole energy transfer. However, this concentration is not reachable in NaI:(Tl,Eu) due to the solubility limit of Eu2+ in NaI crystal.
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