Luminescence and Energy Transfer Properties of Gd³⁺ and Tb³⁺ in LaAlGe₂O₇

Abstract

The novel phosphors of LaAlGe2O7 doped with Gd3+ and Tb3+ were synthesized, and their luminescence properties were investigated. In Tb3+-activated LaAlGe2O7, the unusual excitation spectra showed only intense f−f transition of Tb3+ ions around the near-UV region, whereas the 4f−5d transition could be neglected. In the Gd3+−Tb3+-activated system, the decay time of Tb3+ emission under Gd3+ excitation at the 6IJ energy level was longer than that measured under direct Tb3+ excitation at the 5L10 energy level, which reinforces the existence of effective Gd3+-to-Tb3+ energy transfer. In the 5D4 decay measurements, time-resolved spectra exhibited a “grow-in” behavior as the Tb3+ concentration was diluted (<0.03 mol), whereas 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+-to-Tb3+ energy transfer processes in terms of Tb3+ concentration.