Thermal stable La_2Ti_2O_7:Eu~(3+) phosphors for blue-chip white LEDs with high color rendering index

摘要

High concentration Eu~(3+) doped La_2Ti_2O_7 phosphor with good crystallinity was prepared via solid-state method. This phosphor can emit intense red light with a peak around 612 nm corresponding to the 5D(0) -> F-7(2) transitions of Eu~(3+). The luminescent intensity excited at 465 nm, which corresponds to the wavelength of InGaN-based LEDs, is comparable with the intensity excited at 396 nm. The emission intensity increased with increasing Eu3+ concentration up to 30 mol%, and then decreased due to the concentration quenching. The White LED (WLED) fabricated by coating a mixture of Y_3Al_5O_(12):Ce~(3+) and La_2Ti_2O_7 onto a blue InGaN chip showed higher color rendering index than the WLED fabricated by coating Y_3Al_5O_(12):Ce~(3+)(Y_3Al_5O_(12):Ce~(3+)-WLED). This phosphor also has excellent thermal stability, and the luminous intensity can remain 75.46% when it was heated to 200 degrees. By optimizing the Eu~(3+) concentration and calcination temperature, we demonstrated that La_2Ti_2O_7:Eu~(3+) was a promising red phosphor under blue light (465 nm) for high-power commercial Y_3Al_5O_(12):Ce~(3+)-WLEDs.