Energy transfer in CaF2 doped with Ce3+, Eu2+ and Mn2+ ions

The optical properties of calcium fluoride triply doped with cerium, europium and manganese ions have been analyzed in the present investigation. The spectroscopic data obtained clearly indicate that energy transfer takes place from tetragonal Ce3+-Fint- ions to Eu2+ and Mn2+ ions. Such energy transfer occurs via a short-range interaction mechanism into Ce3+-Eu2+ and Ce3+-Mn2+ clusters formed in the crystalline matrix. In contrast to the Eu2+ → Mn2+ energy transfer usually observed in CaF2:Eu2+:Mn2+, manganese ions do not appear to be sensitized by europium ions, which might suggest that Eu2+ ions prefer to cluster with tetragonal Ce3+ ions when these ions are also present in the lattice. This preferential impurity clustering appears to be a quite relevant finding for the design of more efficient laser systems or conversion phosphors of ultraviolet to visible light. The number of tetragonal cerium ions associated with activator ions (europium or manganese) was estimated using a simple model describing the essential features of the kinetics of the Ce3+ → Eu2+ and Ce3+ → Mn2+ energy transfers