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 Ce 3+ ion results mainly in Tb 3+ emission. We also observed two different Ce 3+ emissions. This is related to the crystal structure of . It is shown that the excitation energy migrates from the Ce 3+ ion over the Gd 3+ sublattice to the Tb 3+ 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 Ce 3+ ion as a sensitizer of the Gd 3+ ion.