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

The novel phosphors of LaAlGe2O7 doped with Gd3+ and W, 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 I-6(J) energy levels, the D-5(4) 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 (P-Gd -> 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. (c) 2007 Elsevier B.V. All rights reserved.