Efficient energy transfer from the Pr3+ 4f5d states to Eu3+ via Gd3+ in K2GdF5

In Pr3+and Eu3+ co-doped K2GdF5, efficient energy transfer from Pr3+ 4f5d states to Eu3+ via Gd3+ is observed. The integrated emission intensity ratio of Eu3+ 5D0,1/5D2,3 upon Pr3+ 4f5d state excitation is enhanced in comparison with the ratio upon Gd3+ 6IJ excitation. The decay times of Eu3+ 5D2 and 5D3 states decrease while those of 5D0,1 states keep the same with the increase of Pr3+ concentration, originating from cross-relaxation energy transfer between Pr3+ and Eu3+. The simulation demonstrates that the probability density φ(R) of Pr3+ distributing both sides of emitting Eu3+ which substitutes the sites with one-dimensional structure is larger upon Pr3+ 4f5d state excitation than that upon the 6IJ state excitation of Gd3+.