Luminescence and energy transfer properties of Gd3+ and Tb3+ in LaAlGe2O7

The novel phosphors of LaAlGe2O7 doped with Gd3+ and Tb3+ were synthesized and their luminescence properties have been investigated. In Tb3+-activated LaAlGe2O7, the extraordinary excitation spectra showed only intense f–f transition of Tb3+ ions around near UV region, while the 4f–5d transition could be neglected. In Gd3+–Tb3+ system, time-resolved spectra exhibit a “grow-in” behavior, which indicates that the decay curves have a contribution from a Gd3+-to-Tb3+ energy transfer pathway. In response to Gd3+ excitation at the 6IJ energy levels, the 5D4 decay time-resolved spectra exhibited a “grow-in” behavior as the Tb3+ concentration was diluted (<0.03 mol), while only a simple exponential decay could be observed at higher (>0.05 mol) Tb3+ concentrations. Two linear relationships were found between the energy transfer probability (PGd→Tb) and the Tb3+ concentration, which is clear evidence that there were two kinds of efficient Gd3+–Tb3+ energy transfer processes in terms of Tb3+ concentration.