Luminescence and multi-step energy transfer in GdAl3(BO3)4 doped with Ce3+/Tb3+

Ce3+ and/or Tb3+ doped GdAl3(BO3)4 phosphors were prepared via a high-temperature solid-state reaction method. The band gap of GdAl3(BO3)4 is determined from the VUV excitation spectrum of a Ce3+ doped sample at 14 K and further confirmed by that of undoped and Tb3+ doped samples at RT. X-ray excited luminescence (XEL) of GdAl3(BO3)4: Ce3+ was measured. The main electron-vibrational interaction (EVI) parameters for Ce3+ in GdAl3(BO3)4 were simulated. The vacuum referred binding energy (VRBE) scheme of lanthanide 4f/5d states in GdAl3(BO3)4 was constructed. Using this scheme, the lowest 5d excitation band of Pr3+ in GdAl3(BO3)4 was predicted, showing that the estimation is in agreement with the experimental result. The occurrence of multi-step energy transfer processes which include Gd3+→Ce3+, Gd3+→Tb3+, Ce3+→Tb3+, and Tb3+→Gd3+, Tb3+→Ce3+ under different excitations was derived from excitation, emission, and fluorescence decay spectra.