Excited state dynamics of Gd3+ and energy transfer efficiency from Gd3+ to Tb3+ in (La, Gd)PO4:Tb3+

Energy transfer processes from Tb3+ 4f75d state to Gd3+ 4f7 state and from Gd3+6P7/2 state to Tb3+ 4f8 state occur in La0.99−xGdxTb0.01PO4 under Tb3+ 4f75d state excitation. The decay of Gd3+6P7/2 state upon Tb3+ 4f75d state excitation is faster than that upon Gd3+6IJ state excitation when Gd3+ concentration is lower than 30 mol%. A model describing different decay properties of Gd3+6P7/2 state was established and corresponding semiquantitative analysis was given. It was observed that the energy transfer efficiency from Gd3+ to Tb3+ was increasing with increase of Gd3+ concentration and an efficiency of close to 100% in Gd0.99Tb0.01PO4 was determined.