Ce decay curves in Ce, Tb co-doped LaF₃ and the energy transfer mechanism

Energy transfer phenomena can play an important role in the development of luminescent materials, and hosts co-doped with Ce³⁺ and Tb ³⁺ ions continue to be actively studied. Several recent reports on Ce, Tb co-doped phosphors suggest different mechanisms for the energy transfer from Ce³⁺ to Tb³⁺ ions and further study is required to reach consensus on the mechanism or to understand why different mechanisms dominate in different hosts. A more direct method of analysis is proposed to distinguish between the different types of multipole energy transfer mechanisms. When applied to Ce, Tb co-doped LaF₃, the experimental data shows a poor match to any of these models but is consistent with energy transfer through the exchange mechanism. The decay curves of Ce emission in Ce, Tb co-doped LaF₃ were also studied to obtain further insight on the energy transfer mechanism. Although the decrease in lifetime with increasing Tb concentration shows that energy transfer occurs through a non-radiative mechanism, the form of the decay curves does not correspond to what is expected for energy transfer via multipole interactions.