A study of the energy transfer processes in sensitized gadolinium phosphors

By suitable sensitization and activation it is possible to design compositions on the basis of gadolinium compounds which show extremely efficient luminescence. For the general composition GdX3:S,A the relevant energy transfer processes are sensitization (S → Gd), energy migration {(Gd → Gd)nx} and trapping (Gd → A). Several examples will be presented in which S → Gd is an efficient process, whereas in other cases it is not. The energy migration process will be discussed in terms of crystal structure, the gadolinium concentration and the interaction mechanism. Finally the trapping process will be discussed. Efficient trapping is possible if the Gd3+ emission lines overlap with a broad allowed absorption band of the activator