α-Sr 2 SiO 4:Ce 3+, Dy3+, , Na+ phosphors with abnormal thermal quenching properties for solid-state lighting applications

There is urgent need of thermally stable phosphors for fabricating high-performance white light emitting diodes (LEDs). In this paper, Sr2SiO4:0.02Ce3+,xDy3+, 2 SiO 4 :0.02Ce 3+ ,xDy 3+ , (0.02+x)Na+ + phosphors were successfully synthesized by the solid-state reaction method and their luminescence properties were studied. Phase analysis shows that single- phasic alpha-Sr2SiO4 2 SiO 4 was prepared when x was greater than 0.006, while a mixed phase of alpha-Sr2SiO4 2 SiO 4 and 3- Sr 2 SiO 4 were obtained in the samples with x of 0.006 or less. When excited at 344 nm, there is a major emission band at 380-500 nm corresponding to the 5d-4f transition of Ce3+, 3+ , and other emission peaks with a dominated one at 575 nm corresponding to the 4F9/2 F 9/2- 6 H 13/2 transition of Dy3+. 3+ . The as-developed Sr2SiO4:Ce3+,Dy3+,Na+ 2 SiO 4 :Ce 3+ ,Dy 3+ ,Na + phosphors exhibit excellent thermal stability. To be specific, the intensity retention rate of 425 and 572 nm at 300 degrees C is as high as 103.6 % and 89.2 %, respectively. Furthermore, near-ultraviolet (nUV) chip-pumped white LED prototypes were assembled using the co-activated phosphor and commercial green and red phosphors, which demonstrate its great potential in high-power white LEDs for solid-state lighting applications.