Theoretical and Experimental Investigation of the Tb³⁺ → Eu³⁺ Energy Transfer Mechanisms in Cubic A₃Tb₀.₉₀Eu₀.₁₀(PO₄)₃ (A = Sr, Ba) Materials

In this study the optical spectroscopy, the excited state dynamics, and in particular the Tb³⁺ → Eu³⁺ energy transfer, have been investigated in detail both from the theoretical and experimental point of view in eulytite double phosphate hosts A₃Tb(PO₄)₃ (A = Sr, Ba) doped with Eu³⁺. It has been found that the energy transfer is strongly assisted by fast migration in the donor Tb³⁺ subset. Moreover, the transfer rates and efficiencies depend significantly on the nature of the divalent elements present in the structure and hence on the distances between Tb³⁺-Eu³⁺ nearest neighbors. It is shown that the competition between quadrupole–quadrupole and exchange interaction is crucial in accounting for the transfer rates.