Color tunable emission via efficient Ce3+→Tb3+ energy transfer pair in MgYSi2O5N oxynitride phosphor for near-UV-pumped white LEDs

An oxynitride phosphor MgYSi2O5N co-doped with Ce3+ and Tb3+ was successfully synthesized by the conventional solid-state reaction at 1623 K for 2 h in NH3 atmosphere. X-ray powder diffraction profiles, photoluminescence spectra, luminescence decay curves and chromaticity variation of the samples were investigated in detail. The photoluminescence properties showed that the Tb3+ ions exhibited characteristic green emission peaks at 545 nm corresponding to the strong excitation band of Ce3+ ions over a broad spectral range between 220 and 380 nm which matched well with the dominant emission band of near UV LED chips. The efficient energy transfer from Ce3+ to Tb3+ was verified by the excitation and emission spectra together with the luminescence decay curves. The corresponding efficiencies of energy transfer and energy transfer mechanisms were also calculated and analyzed according to the variations of the lifetime values of Ce3+. With the doping content of Tb3+ ions increasing, the emitting color of phosphors can be tuned from purplish-blue to green upon 365 nm excitation. All the results indicated that the developed phosphors have a potentiality to be a kind of near UV-convertible phosphor for application in phosphor-converted white-light-emitting diodes.