Eu3+ luminescence and Gd3+-Eu3+ energy transfer in K5Li2GdF10:Eu3+

Abstract.

Polycrystalline samples of europium-doped K₅Li₂GdF₁₀ have been obtained by a slow cooling of melted compound and investigated using spectroscopy methods. Luminescence from the ⁵D₂ level of Eu³⁺ is found to be weak. Intense visible emission upon excitation into the ⁵D₂ or higher energy levels has been attributed to overlapping transitions from long-lived ⁵D₁ and ⁵D₀ levels. A strong increase of the ⁵D₀ emission at the expense of the ⁵D₁ emission occurs between 5 K and 25 K without significant change of the ⁵D₁ lifetime. To account for this, it is supposed that both the radiative and the nonradiative transition rates are temperature-dependent. Efficient energy transfer from the ⁶G_J levels of Gd³⁺ to Eu³⁺ ions has been evidenced by excitation spectra in the VUV region and VUV-excited luminescence. It has been concluded that the cross relaxation contributes to the energy-transfer process.