Excited state dynamics and energy transfer rates in Sr3Tb0.90Eu0.10(PO4)3

The emission spectrum of neat Sr₃Tb(PO₄)₃ upon excitation at 337 nm in the levels above ⁵D₃ is dominated by ⁵D₄ emission and no significant emission from ⁵D₃ is observed due to efficient cross relaxation involving the Tb³⁺ levels. On the other hand, the emission spectrum of the same host containing 10 mol% Eu³⁺ upon excitation at the same wavelength (in the Tb³⁺ levels) is dominated by strong emission bands from the ⁵D₀ level of Eu³⁺. This clearly indicates that Tb³⁺→Eu³⁺ energy transfer is present. The excitation spectrum of the Eu^{3+ 5}D₀ emission is dominated by Tb³⁺ bands extending in the UV region.The presence of 10 mol% Eu³⁺ in Sr₃Tb(PO₄)₃ very strongly shortens the ⁵D₄ decay time. The decay curve is not far from exponential, indicating that the energy transfer to Eu³⁺ is accompanied by fast energy migration. The transfer regimes are identified and the donor–donor and donor–acceptor transfer microparameters are quantified under the assumption of electric dipole–electric dipole interactions.