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 Eu3+ 5D0 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.