Structure and photoluminescence properties of Na2Y2B2O7:Ce3+,Tb3+ phosphors for solid-state lighting application

Novel phosphors of Na2Y2B2O7:Ce3+ and Na2Y2B2O7:Ce3+,Tb3+ were synthesized by a solid-state process and characterized with X-ray diffraction, photoluminescence (PL), PL excitation (PLE), and fluorescence decay time. The relationship between the observed Ce3+ emission properties and the crystal structure of Na2Y2B2O7 is built and the result shows that Ce3+ ions occupy two non-equivalent Y3+ sites in the host. The codoping of Tb3+ in Na2Y2B2O7:Ce3+ can tune the emitting colour from blue to green and increase the luminescence quantum efficiency to 75.2% by the energy transfer of Ce3+-> Tb3+. The energy transfer processes of Ce3+-Ce3+ and Ce3+-Tb3+ are analysed and determined to be electric dipole-dipole and dipole-quadrupole, respectively. The broad PLE spectra of Na2Y2B2O7:Ce3+ and Na2Y2B2O7:Ce3+,Tb3+ are well matched with the emission from near UV LED chips, which indicates that they are promising blue and green phosphors for phosphor-converted white LEDs. (C) 2014 Elsevier Inc. All rights reserved.