Luminescence and energy transfer of color-tunable Na6Ca3Si6O18:Ce3+,Tb3+ phosphors for WLED

A series of Ce3+, Tb3+ co-doped Na6Ca3Si6O18 phosphors have been synthesized by traditional solid state reaction. The emission spectra of the Na6Ca3Si6O18:Ce3+,Tb3+ phosphors show a blue broad band at 450 nm of the Ce3+ and a green line peaking at 550 nm. Energy transfer from CO3+ to Tb3+ ions has been investigated. Results indicate that the color of these phosphors changes from blue to green by adjusting the ratio of Ce3+ to Tb3+. In addition, the mechanism of the energy transfer from the Ce3+ to Tb3+ ions is demonstrated to be a dipole-quadrupole mechanism. The energy transfer efficiency as well as the critical distance is also estimated. By optimizing the Tb3+ concentration, the absolute PL quantum yield as high as 43% can be achieved. The results show that this phosphor has potential applications as a single-phased phosphor for DV white-light LEDs.