Self‐reduction process and enhanced blue emission in SrAl2Si2O8: Eu, Tb via electron transfer from Tb3+ to Eu3+

Eu, Tb co-doped SrAl2Si2O8 luminescent materials were synthesized via a high-temperature solid-state reaction. Excitation spectra of SrAl2Si2O8: Eu2+ gives two broad excitation bands maximizing at 270 and 330 nm, resulting from splitting Eu2+ energy levels in octahedral crystal field. Eu single doped SrAl2Si2O8 luminescent material exhibits two emission bands at about 406 and 616 nm. Intensity of the blue emission from Eu2+ is always strong, compared with that of the red emission band of Eu3+. Reduction from Eu3+ to Eu2+ can be explained with the model of charge compensation. Blue emission in SrAl2Si2O8: xEu was strengthened after incorporation of Tb, which can be explained by electron transfer from Tb3+ to Eu3+ (Tb3++Eu3+→Tb4++Eu2+). Under 230 nm excitation, intensity of Tb3+ emission was nearly unchanged and that of Eu2+ was increased, obviously due to the delivery of more electrons to Eu3+. The strongest emission of Eu2+ in 0.09Eu/0.06Tb co-doped SrAl2Si2O8 and excited at 270 and 330 nm was remarkably enhanced by about four times compared to that of 0.15Eu Single doped SrAl2Si2O8. All of the results indicate that SrAl2Si2O8: xEu, yTb are potential blue emitting luminescent materials for UV-LEDs. More importantly, this research may provide a new perspective in designing broad band blue luminescent materials.