Energy Transfer in the Luminescent System Na (  Y  , Gd )  F ₄ : Ce , Tb

The luminescent properties of hexagonal have been investigated. For and at room temperature, excitation into the Ce³⁺ ion results mainly in Tb³⁺ emission. We also observed two different Ce³⁺ emissions. This is related to the crystal structure of . It is shown that the excitation energy migrates from the Ce³⁺ ion over the Gd³⁺ sublattice to the Tb³⁺ traps. Energy transfer probabilities for this process are derived and compared with the probabilities derived for the system , which leads to some recommendations for the use of the Ce³⁺ ion as a sensitizer of the Gd³⁺ ion.