Novel emission-tunable oxyapatites-type phosphors: Synthesis, luminescent properties and the applications in white light emitting diodes with higher color rendering index

Developing color-tunable phosphors via the introduction of co-doping activators and sensitizers to the host with energy transfer processes has been a state-of-the-art topic for a long time. In this work, novel emission-tunable oxyapatites-type Ba10(PO4)6O:Eu2+,Tb3+/Li+ phosphors were prepared via a high temperature solid state reaction for the applications in white light emitting diodes (w-LEDs) with higher color rendering index. Tunable colors from blue to green can be realized in the Ba10(PO4)6O:Eu2+,Tb3+/Li+ by varying the relative ratios of Eu2+ to Tb3+, showing good absorption in the range of 230-400 nm. The energy transfer mechanism from Eu2+ to Tb3+ ions was demonstrated to be a quadrupole-quadrupole interaction by combining the Inokuti-Hirayama (IH) model and Reisfeld's approximation. Importantly, a prototype white lamp was packaged by mixing Ba9.83(PO4)6O: 0.03Eu2+, 0.07Tb3+, 0.07Li+ and commercial red phosphor CaAlSiN3: Eu2+, and the lamp exhibits a higher color rendering index (Ra = 92 and R9 = 56) and warm correlated color temperature of 4361 K for the actual application. Better luminescent properties compared to commercial Y3Al5O12:Ce3+-based w-LEDs, indicating that Ba10(PO4)6O: Eu2+, Tb3+/Li+ phosphors are emerging as potential phosphor-converted w-LEDs.